<?php
/**
 * Implementation of Integrated Templates API with template 'compilation' added.
 *
 * PHP versions 4 and 5
 *
 * LICENSE: This source file is subject to version 3.01 of the PHP license
 * that is available through the world-wide-web at the following URI:
 * http://www.php.net/license/3_01.txt If you did not receive a copy of
 * the PHP License and are unable to obtain it through the web, please
 * send a note to license@php.net so we can mail you a copy immediately.
 *
 * @category  HTML
 * @package   HTML_Template_Sigma
 * @author    Ulf Wendel <ulf.wendel@phpdoc.de>
 * @author    Alexey Borzov <avb@php.net>
 * @copyright 2001-2007 The PHP Group
 * @license   http://www.php.net/license/3_01.txt PHP License 3.01
 * @link      http://pear.php.net/package/HTML_Template_Sigma
 */

/**
 * PEAR and PEAR_Error classes (for error handling)
 */
require_once 'PEAR.php';

/**#@+
 * Error codes
 * @see HTML_Template_Sigma::errorMessage()
 */
define('SIGMA_OK',                         1);
define('SIGMA_ERROR',                     -1);
define('SIGMA_TPL_NOT_FOUND',             -2);
define('SIGMA_BLOCK_NOT_FOUND',           -3);
define('SIGMA_BLOCK_DUPLICATE',           -4);
define('SIGMA_CACHE_ERROR',               -5);
define('SIGMA_UNKNOWN_OPTION',            -6);
define('SIGMA_PLACEHOLDER_NOT_FOUND',     -10);
define('SIGMA_PLACEHOLDER_DUPLICATE',     -11);
define('SIGMA_BLOCK_EXISTS',              -12);
define('SIGMA_INVALID_CALLBACK',          -13);
define('SIGMA_CALLBACK_SYNTAX_ERROR',     -14);
/**#@-*/

/**
* Implementation of Integrated Templates API with template 'compilation' added.
*
* The main new feature in Sigma is the template 'compilation'. Consider the
* following: when loading a template file the engine has to parse it using
* regular expressions to find all the blocks and variable placeholders. This
* is a very "expensive" operation and is definitely an overkill to do on
* every page request: templates seldom change on production websites. This is
* where the cache kicks in: it saves an internal representation of the
* template structure into a file and this file gets loaded instead of the
* source one on subsequent requests (unless the source changes, of course).
*
* While HTML_Template_Sigma inherits PHPLib Template's template syntax, it has
* an API which is easier to understand. When using HTML_Template_PHPLIB, you
* have to explicitly name a source and a target the block gets parsed into.
* This gives maximum flexibility but requires full knowledge of template
* structure from the programmer.
*
* Integrated Template on the other hands manages block nesting and parsing
* itself. The engine knows that inner1 is a child of block2, there's
* no need to tell it about this:
*
* <pre>
* + __global__ (hidden and automatically added)
*     + block1
*     + block2
*         + inner1
*         + inner2
* </pre>
*
* To add content to block1 you simply type:
* <code>$tpl->setCurrentBlock("block1");</code>
* and repeat this as often as needed:
* <code>
*   $tpl->setVariable(...);
*   $tpl->parseCurrentBlock();
* </code>
*
* To add content to block2 you would type something like:
* <code>
* $tpl->setCurrentBlock("inner1");
* $tpl->setVariable(...);
* $tpl->parseCurrentBlock();
*
* $tpl->setVariable(...);
* $tpl->parseCurrentBlock();
*
* $tpl->parse("block2");
* </code>
*
* This will result in one repetition of block2 which contains two repetitions
* of inner1. inner2 will be removed if $removeEmptyBlock is set to true (which
* is the default).
*
* Usage:
* <code>
* $tpl = new HTML_Template_Sigma( [string filerootdir], [string cacherootdir] );
*
* // load a template or set it with setTemplate()
* $tpl->loadTemplatefile( string filename [, boolean removeUnknownVariables, boolean removeEmptyBlocks] )
*
* // set "global" Variables meaning variables not beeing within a (inner) block
* $tpl->setVariable( string variablename, mixed value );
*
* // like with the HTML_Template_PHPLIB there's a second way to use setVariable()
* $tpl->setVariable( array ( string varname => mixed value ) );
*
* // Let's use any block, even a deeply nested one
* $tpl->setCurrentBlock( string blockname );
*
* // repeat this as often as you need it.
* $tpl->setVariable( array ( string varname => mixed value ) );
* $tpl->parseCurrentBlock();
*
* // get the parsed template or print it: $tpl->show()
* $html = $tpl->get();
* </code>
*
* @category HTML
* @package  HTML_Template_Sigma
* @author   Ulf Wendel <ulf.wendel@phpdoc.de>
* @author   Alexey Borzov <avb@php.net>
* @license  http://www.php.net/license/3_01.txt PHP License 3.01
* @version  Release: 1.3.0
* @link     http://pear.php.net/package/HTML_Template_Sigma
*/
class HTML_Template_Sigma extends PEAR
{
    /**
     * First character of a variable placeholder ( _{_VARIABLE} ).
     * @var      string
     * @access   public
     * @see      $closingDelimiter, $blocknameRegExp, $variablenameRegExp
     */
    var $openingDelimiter = '{';

    /**
     * Last character of a variable placeholder ( {VARIABLE_}_ )
     * @var      string
     * @access   public
     * @see      $openingDelimiter, $blocknameRegExp, $variablenameRegExp
     */
    var $closingDelimiter = '}';

    /**
     * RegExp for matching the block names in the template.
     * Per default "sm" is used as the regexp modifier, "i" is missing.
     * That means a case sensitive search is done.
     * @var      string
     * @access   public
     * @see      $variablenameRegExp, $openingDelimiter, $closingDelimiter
     */
    var $blocknameRegExp = '[0-9A-Za-z_-]+';

    /**
     * RegExp matching a variable placeholder in the template.
     * Per default "sm" is used as the regexp modifier, "i" is missing.
     * That means a case sensitive search is done.
     * @var      string
     * @access   public
     * @see      $blocknameRegExp, $openingDelimiter, $closingDelimiter
     */
    var $variablenameRegExp = '[0-9A-Za-z._-]+';

    /**
     * RegExp used to find variable placeholder, filled by the constructor
     * @var      string    Looks somewhat like @(delimiter varname delimiter)@
     * @see      HTML_Template_Sigma()
     */
    var $variablesRegExp = '';

    /**
     * RegExp used to strip unused variable placeholders
     * @see      $variablesRegExp, HTML_Template_Sigma()
     */
    var $removeVariablesRegExp = '';

    /**
     * RegExp used to find blocks and their content, filled by the constructor
     * @var      string
     * @see      HTML_Template_Sigma()
     */
    var $blockRegExp = '';

    /**
     * Controls the handling of unknown variables, default is remove
     * @var      boolean
     * @access   public
     */
    var $removeUnknownVariables = true;

    /**
     * Controls the handling of empty blocks, default is remove
     * @var      boolean
     * @access   public
     */
    var $removeEmptyBlocks = true;

    /**
     * Name of the current block
     * @var      string
     */
    var $currentBlock = '__global__';

    /**
     * Template blocks and their content
     * @var      array
     * @see      _buildBlocks()
     * @access   private
     */
    var $_blocks = array();

    /**
     * Content of parsed blocks
     * @var      array
     * @see      get(), parse()
     * @access   private
     */
    var $_parsedBlocks = array();

    /**
     * Variable names that appear in the block
     * @var      array
     * @see      _buildBlockVariables()
     * @access   private
     */
    var $_blockVariables = array();

    /**
     * Inner blocks inside the block
     * @var      array
     * @see      _buildBlocks()
     * @access   private
     */
    var $_children = array();

    /**
     * List of blocks to preserve even if they are "empty"
     * @var      array
     * @see      touchBlock(), $removeEmptyBlocks
     * @access   private
     */
    var $_touchedBlocks = array();

    /**
     * List of blocks which should not be shown even if not "empty"
     * @var      array
     * @see      hideBlock(), $removeEmptyBlocks
     * @access   private
     */
    var $_hiddenBlocks = array();

    /**
     * Variables for substitution.
     *
     * Variables are kept in this array before the replacements are done.
     * This allows automatic removal of empty blocks.
     *
     * @var      array
     * @see      setVariable()
     * @access   private
     */
    var $_variables = array();

    /**
     * Global variables for substitution
     *
     * These are substituted into all blocks, are not cleared on
     * block parsing and do not trigger "non-empty" logic. I.e. if
     * only global variables are substituted into the block, it is
     * still considered "empty".
     *
     * @var      array
     * @see      setVariable(), setGlobalVariable()
     * @access   private
     */
    var $_globalVariables = array();

    /**
     * Root directory for "source" templates
     * @var    string
     * @see    HTML_Template_Sigma(), setRoot()
     */
    var $fileRoot = '';

    /**
     * Directory to store the "prepared" templates in
     * @var      string
     * @see      HTML_Template_Sigma(), setCacheRoot()
     * @access   private
     */
    var $_cacheRoot = null;

    /**
     * Flag indicating that the global block was parsed
     * @var    boolean
     */
    var $flagGlobalParsed = false;

    /**
     * Options to control some finer aspects of Sigma's work.
     *
     * @var      array
     * @access   private
     */
    var $_options = array(
        'preserve_data' => false,
        'trim_on_save'  => true,
        'charset'       => 'iso-8859-1'
    );

    /**
     * Function name prefix used when searching for function calls in the template
     * @var    string
     */
    var $functionPrefix = 'func_';

    /**
     * Function name RegExp
     * @var    string
     */
    var $functionnameRegExp = '[_a-zA-Z][A-Za-z_0-9]*';

    /**
     * RegExp used to grep function calls in the template (set by the constructor)
     * @var    string
     * @see    _buildFunctionlist(), HTML_Template_Sigma()
     */
    var $functionRegExp = '';

    /**
     * List of functions found in the template.
     * @var    array
     * @access private
     */
    var $_functions = array();

    /**
     * List of callback functions specified by the user
     * @var    array
     * @access private
     */
    var $_callback = array();

    /**
     * RegExp used to find file inclusion calls in the template
     * @var  string
     */
    var $includeRegExp = '#<!--\s+INCLUDE\s+(\S+)\s+-->#im';

    /**
     * RegExp used to find (and remove) comments in the template
     * @var  string
     */
    var $commentRegExp = '#<!--\s+COMMENT\s+-->.*?<!--\s+/COMMENT\s+-->#sm';

    /**
     * Files queued for inclusion
     * @var    array
     * @access private
     */
    var $_triggers = array();

    /**
     * Name of the block to use in _makeTrigger() (see bug #20068)
     * @var string
     * @access private
     */
    var $_triggerBlock = '__global__';

    /**
     * Constructor: builds some complex regular expressions and optionally
     * sets the root directories.
     *
     * Make sure that you call this constructor if you derive your template
     * class from this one.
     *
     * @param string $root      root directory for templates
     * @param string $cacheRoot directory to cache "prepared" templates in
     *
     * @see   setRoot(), setCacheRoot()
     */
    function HTML_Template_Sigma($root = '', $cacheRoot = '')
    {
        // the class is inherited from PEAR to be able to use $this->setErrorHandling()
        $this->PEAR();
        $this->variablesRegExp       = '@' . $this->openingDelimiter . '(' . $this->variablenameRegExp . ')' .
                                       '(:(' . $this->functionnameRegExp . '))?' . $this->closingDelimiter . '@sm';
        $this->removeVariablesRegExp = '@' . $this->openingDelimiter . '\s*(' . $this->variablenameRegExp . ')\s*'
                                       . $this->closingDelimiter . '@sm';
        $this->blockRegExp           = '@<!--\s+BEGIN\s+(' . $this->blocknameRegExp
                                       . ')\s+-->(.*)<!--\s+END\s+\1\s+-->@sm';
        $this->functionRegExp        = '@' . $this->functionPrefix . '(' . $this->functionnameRegExp . ')\s*\(@sm';
        $this->setRoot($root);
        $this->setCacheRoot($cacheRoot);

        $this->setCallbackFunction('h', array(&$this, '_htmlspecialchars'));
        $this->setCallbackFunction('e', array(&$this, '_htmlentities'));
        $this->setCallbackFunction('u', 'urlencode');
        $this->setCallbackFunction('r', 'rawurlencode');
        $this->setCallbackFunction('j', array(&$this, '_jsEscape'));
    }


    /**
     * Sets the file root for templates. The file root gets prefixed to all
     * filenames passed to the object.
     *
     * @param string $root directory name
     *
     * @see    HTML_Template_Sigma()
     * @access public
     * @return void
     */
    function setRoot($root)
    {
        if (('' != $root) && (DIRECTORY_SEPARATOR != substr($root, -1))) {
            $root .= DIRECTORY_SEPARATOR;
        }
        $this->fileRoot = $root;
    }


    /**
     * Sets the directory to cache "prepared" templates in, the directory should be writable for PHP.
     *
     * The "prepared" template contains an internal representation of template
     * structure: essentially a serialized array of $_blocks, $_blockVariables,
     * $_children and $_functions, may also contain $_triggers. This allows
     * to bypass expensive calls to _buildBlockVariables() and especially
     * _buildBlocks() when reading the "prepared" template instead of
     * the "source" one.
     *
     * The files in this cache do not have any TTL and are regenerated when the
     * source templates change.
     *
     * @param string $root directory name
     *
     * @see    HTML_Template_Sigma(), _getCached(), _writeCache()
     * @access public
     * @return void
     */
    function setCacheRoot($root)
    {
        if (empty($root)) {
            $root = null;
        } elseif (DIRECTORY_SEPARATOR != substr($root, -1)) {
            $root .= DIRECTORY_SEPARATOR;
        }
        $this->_cacheRoot = $root;
    }


    /**
     * Sets the option for the template class
     *
     * Currently available options:
     * - preserve_data: If false (default), then substitute variables and
     *   remove empty placeholders in data passed through setVariable (see also
     *   PHP bugs #20199, #21951)
     * - trim_on_save: Whether to trim extra whitespace from template on cache
     *   save (defaults to true). Generally safe to leave this on, unless you
     *   have <<pre>><</pre>> in templates or want to preserve HTML indentantion
     * - charset: is used by builtin template callback 'h'/'e'. Defaults to 'iso-8859-1'
     *
     * @param string $option option name
     * @param mixed  $value  option value
     *
     * @access public
     * @return mixed SIGMA_OK on success, error object on failure
     */
    function setOption($option, $value)
    {
        if (isset($this->_options[$option])) {
            $this->_options[$option] = $value;
            return SIGMA_OK;
        }
        return $this->raiseError($this->errorMessage(SIGMA_UNKNOWN_OPTION, $option), SIGMA_UNKNOWN_OPTION);
    }


    /**
     * Returns a textual error message for an error code
     *
     * @param integer|PEAR_Error $code error code or another error object for code reuse
     * @param string             $data additional data to insert into message
     *
     * @access public
     * @return string error message
     */
    function errorMessage($code, $data = null)
    {
        static $errorMessages;
        if (!isset($errorMessages)) {
            $errorMessages = array(
                SIGMA_ERROR                 => 'unknown error',
                SIGMA_OK                    => '',
                SIGMA_TPL_NOT_FOUND         => 'Cannot read the template file \'%s\'',
                SIGMA_BLOCK_NOT_FOUND       => 'Cannot find block \'%s\'',
                SIGMA_BLOCK_DUPLICATE       => 'The name of a block must be unique within a template. '
                                               . 'Block \'%s\' found twice.',
                SIGMA_CACHE_ERROR           => 'Cannot save template file \'%s\'',
                SIGMA_UNKNOWN_OPTION        => 'Unknown option \'%s\'',
                SIGMA_PLACEHOLDER_NOT_FOUND => 'Variable placeholder \'%s\' not found',
                SIGMA_PLACEHOLDER_DUPLICATE => 'Placeholder \'%s\' should be unique, found in multiple blocks',
                SIGMA_BLOCK_EXISTS          => 'Block \'%s\' already exists',
                SIGMA_INVALID_CALLBACK      => 'Callback does not exist',
                SIGMA_CALLBACK_SYNTAX_ERROR => 'Cannot parse template function: %s'
            );
        }

        if (is_a($code, 'PEAR_Error')) {
            $code = $code->getCode();
        }
        if (!isset($errorMessages[$code])) {
            return $errorMessages[SIGMA_ERROR];
        } else {
            return (null === $data)? $errorMessages[$code]: sprintf($errorMessages[$code], $data);
        }
    }


    /**
     * Prints a block with all replacements done.
     *
     * @param string $block block name
     *
     * @access  public
     * @return  void
     * @see     get()
     */
    function show($block = '__global__')
    {
        print $this->get($block);
    }


    /**
     * Returns a block with all replacements done.
     *
     * @param string $block block name
     * @param bool   $clear whether to clear parsed block contents
     *
     * @return string block with all replacements done
     * @throws PEAR_Error
     * @access public
     * @see    show()
     */
    function get($block = '__global__', $clear = false)
    {
        if (!isset($this->_blocks[$block])) {
            return $this->raiseError($this->errorMessage(SIGMA_BLOCK_NOT_FOUND, $block), SIGMA_BLOCK_NOT_FOUND);
        }
        if ('__global__' == $block && !$this->flagGlobalParsed) {
            $this->parse('__global__');
        }
        // return the parsed block, removing the unknown placeholders if needed
        if (!isset($this->_parsedBlocks[$block])) {
            return '';

        } else {
            $ret = $this->_parsedBlocks[$block];
            if ($clear) {
                unset($this->_parsedBlocks[$block]);
            }
            if ($this->removeUnknownVariables) {
                $ret = preg_replace($this->removeVariablesRegExp, '', $ret);
            }
            if ($this->_options['preserve_data']) {
                $ret = str_replace(
                    $this->openingDelimiter . '%preserved%' . $this->closingDelimiter, $this->openingDelimiter, $ret
                );
            }
            return $ret;
        }
    }


    /**
     * Parses the given block.
     *
     * @param string $block         block name
     * @param bool   $flagRecursion true if the function is called recursively (do not set this to true yourself!)
     * @param bool   $fakeParse     true if parsing a "hidden" block (do not set this to true yourself!)
     *
     * @return bool whether the block was "empty"
     * @access public
     * @see    parseCurrentBlock()
     * @throws PEAR_Error
     */
    function parse($block = '__global__', $flagRecursion = false, $fakeParse = false)
    {
        static $vars;

        if (!isset($this->_blocks[$block])) {
            return $this->raiseError($this->errorMessage(SIGMA_BLOCK_NOT_FOUND, $block), SIGMA_BLOCK_NOT_FOUND);
        }
        if ('__global__' == $block) {
            $this->flagGlobalParsed = true;
        }
        if (!isset($this->_parsedBlocks[$block])) {
            $this->_parsedBlocks[$block] = '';
        }
        $outer = $this->_blocks[$block];

        if (!$flagRecursion) {
            $vars = array();
        }
        // block is not empty if its local var is substituted
        $empty = true;
        foreach ($this->_blockVariables[$block] as $allowedvar => $v) {
            if (isset($this->_variables[$allowedvar])) {
                $vars[$this->openingDelimiter . $allowedvar . $this->closingDelimiter] = $this->_variables[$allowedvar];
                $empty = false;
                // vital for checking "empty/nonempty" status
                unset($this->_variables[$allowedvar]);
            }
        }

        // processing of the inner blocks
        if (isset($this->_children[$block])) {
            foreach ($this->_children[$block] as $innerblock => $v) {
                $placeholder = $this->openingDelimiter.'__'.$innerblock.'__'.$this->closingDelimiter;

                if (isset($this->_hiddenBlocks[$innerblock])) {
                    // don't bother actually parsing this inner block; but we _have_
                    // to go through its local vars to prevent problems on next iteration
                    $this->parse($innerblock, true, true);
                    unset($this->_hiddenBlocks[$innerblock]);
                    $outer = str_replace($placeholder, '', $outer);

                } else {
                    $this->parse($innerblock, true, $fakeParse);
                    // block is not empty if its inner block is not empty
                    if ('' != $this->_parsedBlocks[$innerblock]) {
                        $empty = false;
                    }

                    $outer = str_replace($placeholder, $this->_parsedBlocks[$innerblock], $outer);
                    $this->_parsedBlocks[$innerblock] = '';
                }
            }
        }

        // add "global" variables to the static array
        foreach ($this->_globalVariables as $allowedvar => $value) {
            if (isset($this->_blockVariables[$block][$allowedvar])) {
                $vars[$this->openingDelimiter . $allowedvar . $this->closingDelimiter] = $value;
            }
        }
        // if we are inside a hidden block, don't bother
        if (!$fakeParse) {
            if (0 != count($vars) && (!$flagRecursion || !empty($this->_functions[$block]))) {
                $varKeys     = array_keys($vars);
                $varValues   = $this->_options['preserve_data']
                               ? array_map(array(&$this, '_preserveOpeningDelimiter'), array_values($vars))
                               : array_values($vars);
            }

            // check whether the block is considered "empty" and append parsed content if not
            if (!$empty || '__global__' == $block
                || !$this->removeEmptyBlocks || isset($this->_touchedBlocks[$block])
            ) {
                // perform callbacks
                if (!empty($this->_functions[$block])) {
                    foreach ($this->_functions[$block] as $id => $data) {
                        $placeholder = $this->openingDelimiter . '__function_' . $id . '__' . $this->closingDelimiter;
                        // do not waste time calling function more than once
                        if (!isset($vars[$placeholder])) {
                            $args         = array();
                            $preserveArgs = !empty($this->_callback[$data['name']]['preserveArgs']);
                            foreach ($data['args'] as $arg) {
                                $args[] = (empty($varKeys) || $preserveArgs)
                                          ? $arg
                                          : str_replace($varKeys, $varValues, $arg);
                            }
                            if (isset($this->_callback[$data['name']]['data'])) {
                                $res = call_user_func_array($this->_callback[$data['name']]['data'], $args);
                            } else {
                                $res = isset($args[0])? $args[0]: '';
                            }
                            $outer = str_replace($placeholder, $res, $outer);
                            // save the result to variable cache, it can be requested somewhere else
                            $vars[$placeholder] = $res;
                        }
                    }
                }
                // substitute variables only on non-recursive call, thus all
                // variables from all inner blocks get substituted
                if (!$flagRecursion && !empty($varKeys)) {
                    $outer = str_replace($varKeys, $varValues, $outer);
                }

                $this->_parsedBlocks[$block] .= $outer;
                if (isset($this->_touchedBlocks[$block])) {
                    unset($this->_touchedBlocks[$block]);
                }
            }
        }
        return $empty;
    }


    /**
     * Sets a variable value.
     *
     * The function can be used either like setVariable("varname", "value")
     * or with one array $variables["varname"] = "value" given setVariable($variables)
     *
     * If $value is an array ('key' => 'value', ...) then values from that array 
     * will be assigned to template placeholders of the form {variable.key}, ...
     *
     * @param string|array $variable variable name or array ('varname' => 'value')
     * @param string|array $value    variable value if $variable is not an array
     *
     * @access public
     * @return void
     */
    function setVariable($variable, $value = '')
    {
        if (is_array($variable)) {
            $this->_variables = array_merge($this->_variables, $variable);
        } elseif (is_array($value)) {
            $this->_variables = array_merge(
                $this->_variables, $this->_flattenVariables($variable, $value)
            );
        } else {
            $this->_variables[$variable] = $value;
        }
    }


    /**
     * Sets a global variable value.
     *
     * @param string|array $variable variable name or array ('varname' => 'value')
     * @param string|array $value    variable value if $variable is not an array
     *
     * @access public
     * @return void
     * @see    setVariable()
     */
    function setGlobalVariable($variable, $value = '')
    {
        if (is_array($variable)) {
            $this->_globalVariables = array_merge($this->_globalVariables, $variable);
        } elseif (is_array($value)) {
            $this->_globalVariables = array_merge(
                $this->_globalVariables, $this->_flattenVariables($variable, $value)
            );
        } else {
            $this->_globalVariables[$variable] = $value;
        }
    }


    /**
     * Sets the name of the current block: the block where variables are added
     *
     * @param string $block block name
     *
     * @access public
     * @return mixed SIGMA_OK on success, error object on failure
     * @throws PEAR_Error
     */
    function setCurrentBlock($block = '__global__')
    {
        if (!isset($this->_blocks[$block])) {
            return $this->raiseError($this->errorMessage(SIGMA_BLOCK_NOT_FOUND, $block), SIGMA_BLOCK_NOT_FOUND);
        }
        $this->currentBlock = $block;
        return SIGMA_OK;
    }


    /**
     * Parses the current block
     *
     * @see    parse(), setCurrentBlock()
     * @access public
     * @return bool whether the block was "empty"
     */
    function parseCurrentBlock()
    {
        return $this->parse($this->currentBlock);
    }


    /**
     * Returns the current block name
     *
     * @return string block name
     * @access public
     */
    function getCurrentBlock()
    {
        return $this->currentBlock;
    }


    /**
     * Preserves the block even if empty blocks should be removed.
     *
     * Sometimes you have blocks that should be preserved although they are
     * empty (no placeholder replaced). Think of a shopping basket. If it's
     * empty you have to show a message to the user. If it's filled you have
     * to show the contents of the shopping basket. Now where to place the
     * message that the basket is empty? It's not a good idea to place it
     * in you application as customers tend to like unecessary minor text
     * changes. Having another template file for an empty basket means that
     * one fine day the filled and empty basket templates will have different
     * layouts.
     *
     * So blocks that do not contain any placeholders but only messages like
     * "Your shopping basked is empty" are intoduced. Now if there is no
     * replacement done in such a block the block will be recognized as "empty"
     * and by default ($removeEmptyBlocks = true) be stripped off. To avoid this
     * you can call touchBlock()
     *
     * @param string $block block name
     *
     * @access public
     * @return mixed SIGMA_OK on success, error object on failure
     * @throws PEAR_Error
     * @see    $removeEmptyBlocks, $_touchedBlocks
     */
    function touchBlock($block)
    {
        if (!isset($this->_blocks[$block])) {
            return $this->raiseError($this->errorMessage(SIGMA_BLOCK_NOT_FOUND, $block), SIGMA_BLOCK_NOT_FOUND);
        }
        if (isset($this->_hiddenBlocks[$block])) {
            unset($this->_hiddenBlocks[$block]);
        }
        $this->_touchedBlocks[$block] = true;
        return SIGMA_OK;
    }


    /**
     * Hides the block even if it is not "empty".
     *
     * Is somewhat an opposite to touchBlock().
     *
     * Consider a block (a 'edit' link for example) that should be visible to
     * registered/"special" users only, but its visibility is triggered by
     * some little 'id' field passed in a large array into setVariable(). You
     * can either carefully juggle your variables to prevent the block from
     * appearing (a fragile solution) or simply call hideBlock()
     *
     * @param string $block block name
     *
     * @access public
     * @return mixed SIGMA_OK on success, error object on failure
     * @throws PEAR_Error
     */
    function hideBlock($block)
    {
        if (!isset($this->_blocks[$block])) {
            return $this->raiseError($this->errorMessage(SIGMA_BLOCK_NOT_FOUND, $block), SIGMA_BLOCK_NOT_FOUND);
        }
        if (isset($this->_touchedBlocks[$block])) {
            unset($this->_touchedBlocks[$block]);
        }
        $this->_hiddenBlocks[$block] = true;
        return SIGMA_OK;
    }


    /**
     * Sets the template.
     *
     * You can either load a template file from disk with LoadTemplatefile() or set the
     * template manually using this function.
     *
     * @param string  $template               template content
     * @param boolean $removeUnknownVariables remove unknown/unused variables?
     * @param boolean $removeEmptyBlocks      remove empty blocks?
     *
     * @access public
     * @return mixed SIGMA_OK on success, error object on failure
     * @see    loadTemplatefile()
     */
    function setTemplate($template, $removeUnknownVariables = true, $removeEmptyBlocks = true)
    {
        $this->_resetTemplate($removeUnknownVariables, $removeEmptyBlocks);
        $list = $this->_buildBlocks(
            '<!-- BEGIN __global__ -->' .
            preg_replace($this->commentRegExp, '', $template) .
            '<!-- END __global__ -->'
        );
        if (is_a($list, 'PEAR_Error')) {
            return $list;
        }
        return $this->_buildBlockVariables();
    }


    /**
     * Loads a template file.
     *
     * If caching is on, then it checks whether a "prepared" template exists.
     * If it does, it gets loaded instead of the original, if it does not, then
     * the original gets loaded and prepared and then the prepared version is saved.
     * addBlockfile() and replaceBlockfile() implement quite the same logic.
     *
     * @param string  $filename               filename
     * @param boolean $removeUnknownVariables remove unknown/unused variables?
     * @param boolean $removeEmptyBlocks      remove empty blocks?
     *
     * @access public
     * @return mixed SIGMA_OK on success, error object on failure
     * @see    setTemplate(), $removeUnknownVariables, $removeEmptyBlocks
     */
    function loadTemplateFile($filename, $removeUnknownVariables = true, $removeEmptyBlocks = true)
    {
        if ($this->_isCached($filename)) {
            $this->_resetTemplate($removeUnknownVariables, $removeEmptyBlocks);
            return $this->_getCached($filename);
        }
        if (false === ($template = @file_get_contents($this->fileRoot . $filename))) {
            return $this->raiseError($this->errorMessage(SIGMA_TPL_NOT_FOUND, $filename), SIGMA_TPL_NOT_FOUND);
        }
        $this->_triggers     = array();
        $this->_triggerBlock = '__global__';
        $template = preg_replace_callback($this->includeRegExp, array(&$this, '_makeTrigger'), $template);
        if (SIGMA_OK !== ($res = $this->setTemplate($template, $removeUnknownVariables, $removeEmptyBlocks))) {
            return $res;
        } else {
            return $this->_writeCache($filename, '__global__');
        }
    }


    /**
     * Adds a block to the template changing a variable placeholder to a block placeholder.
     *
     * This means that a new block will be integrated into the template in
     * place of a variable placeholder. The variable placeholder will be
     * removed and the new block will behave in the same way as if it was
     * inside the original template.
     *
     * The block content must not start with <!-- BEGIN blockname --> and end with
     * <!-- END blockname -->, if it does the error will be thrown.
     *
     * @param string $placeholder name of the variable placeholder, the name must be unique within the template.
     * @param string $block       name of the block to be added
     * @param string $template    content of the block
     *
     * @access public
     * @return mixed SIGMA_OK on success, error object on failure
     * @throws PEAR_Error
     * @see    addBlockfile()
     */
    function addBlock($placeholder, $block, $template)
    {
        if (isset($this->_blocks[$block])) {
            return $this->raiseError($this->errorMessage(SIGMA_BLOCK_EXISTS, $block), SIGMA_BLOCK_EXISTS);
        }
        $parents = $this->_findParentBlocks($placeholder);
        if (0 == count($parents)) {
            return $this->raiseError(
                $this->errorMessage(SIGMA_PLACEHOLDER_NOT_FOUND, $placeholder), SIGMA_PLACEHOLDER_NOT_FOUND
            );

        } elseif (count($parents) > 1) {
            return $this->raiseError(
                $this->errorMessage(SIGMA_PLACEHOLDER_DUPLICATE, $placeholder), SIGMA_PLACEHOLDER_DUPLICATE
            );
        }

        $list = $this->_buildBlocks(
            "<!-- BEGIN $block -->" .
            preg_replace($this->commentRegExp, '', $template) .
            "<!-- END $block -->"
        );
        if (is_a($list, 'PEAR_Error')) {
            return $list;
        }
        $this->_replacePlaceholder($parents[0], $placeholder, $block);
        return $this->_buildBlockVariables($block);
    }


    /**
     * Adds a block taken from a file to the template, changing a variable placeholder
     * to a block placeholder.
     *
     * @param string $placeholder name of the variable placeholder
     * @param string $block       name of the block to be added
     * @param string $filename    template file that contains the block
     *
     * @access public
     * @return mixed SIGMA_OK on success, error object on failure
     * @throws PEAR_Error
     * @see    addBlock()
     */
    function addBlockfile($placeholder, $block, $filename)
    {
        if ($this->_isCached($filename)) {
            return $this->_getCached($filename, $block, $placeholder);
        }
        if (false === ($template = @file_get_contents($this->fileRoot . $filename))) {
            return $this->raiseError($this->errorMessage(SIGMA_TPL_NOT_FOUND, $filename), SIGMA_TPL_NOT_FOUND);
        }
        list($oldTriggerBlock, $this->_triggerBlock) = array($this->_triggerBlock, $block);
        $template = preg_replace_callback($this->includeRegExp, array(&$this, '_makeTrigger'), $template);
        $this->_triggerBlock = $oldTriggerBlock;
        if (SIGMA_OK !== ($res = $this->addBlock($placeholder, $block, $template))) {
            return $res;
        } else {
            return $this->_writeCache($filename, $block);
        }
    }


    /**
     * Replaces an existing block with new content.
     *
     * This function will replace a block of the template and all blocks
     * contained in it and add a new block instead. This means you can
     * dynamically change your template.
     *
     * Sigma analyses the way you've nested blocks and knows which block
     * belongs into another block. This nesting information helps to make the
     * API short and simple. Replacing blocks does not only mean that Sigma
     * has to update the nesting information (relatively time consuming task)
     * but you have to make sure that you do not get confused due to the
     * template change yourself.
     *
     * @param string  $block       name of a block to replace
     * @param string  $template    new content
     * @param boolean $keepContent true if the parsed contents of the block should be kept
     *
     * @access public
     * @return mixed SIGMA_OK on success, error object on failure
     * @throws PEAR_Error
     * @see    replaceBlockfile(), addBlock()
     */
    function replaceBlock($block, $template, $keepContent = false)
    {
        if (!isset($this->_blocks[$block])) {
            return $this->raiseError($this->errorMessage(SIGMA_BLOCK_NOT_FOUND, $block), SIGMA_BLOCK_NOT_FOUND);
        }
        // should not throw a error as we already checked for block existance
        $this->_removeBlockData($block, $keepContent);

        $list = $this->_buildBlocks(
            "<!-- BEGIN $block -->" .
            preg_replace($this->commentRegExp, '', $template) .
            "<!-- END $block -->"
        );
        if (is_a($list, 'PEAR_Error')) {
            return $list;
        }
        // renew the variables list
        return $this->_buildBlockVariables($block);
    }


    /**
     * Replaces an existing block with new content from a file.
     *
     * @param string  $block       name of a block to replace
     * @param string  $filename    template file that contains the block
     * @param boolean $keepContent true if the parsed contents of the block should be kept
     *
     * @access public
     * @return mixed SIGMA_OK on success, error object on failure
     * @throws PEAR_Error
     * @see    replaceBlock(), addBlockfile()
     */
    function replaceBlockfile($block, $filename, $keepContent = false)
    {
        if ($this->_isCached($filename)) {
            $res = $this->_removeBlockData($block, $keepContent);
            if (is_a($res, 'PEAR_Error')) {
                return $res;
            } else {
                return $this->_getCached($filename, $block);
            }
        }
        if (false === ($template = @file_get_contents($this->fileRoot . $filename))) {
            return $this->raiseError($this->errorMessage(SIGMA_TPL_NOT_FOUND, $filename), SIGMA_TPL_NOT_FOUND);
        }
        list($oldTriggerBlock, $this->_triggerBlock) = array($this->_triggerBlock, $block);
        $template = preg_replace_callback($this->includeRegExp, array(&$this, '_makeTrigger'), $template);
        $this->_triggerBlock = $oldTriggerBlock;
        if (SIGMA_OK !== ($res = $this->replaceBlock($block, $template, $keepContent))) {
            return $res;
        } else {
            return $this->_writeCache($filename, $block);
        }
    }


    /**
     * Checks if the block exists in the template
     *
     * @param string $block block name
     *
     * @access public
     * @return bool
     */
    function blockExists($block)
    {
        return isset($this->_blocks[$block]);
    }


    /**
     * Returns the name of the (first) block that contains the specified placeholder.
     *
     * @param string $placeholder Name of the placeholder you're searching
     * @param string $block       Name of the block to scan. If left out (default) all blocks are scanned.
     *
     * @access public
     * @return string Name of the (first) block that contains the specified placeholder.
     *                If the placeholder was not found an empty string is returned.
     * @throws PEAR_Error
     */
    function placeholderExists($placeholder, $block = '')
    {
        if ('' != $block && !isset($this->_blocks[$block])) {
            return $this->raiseError($this->errorMessage(SIGMA_BLOCK_NOT_FOUND, $block), SIGMA_BLOCK_NOT_FOUND);
        }
        if ('' != $block) {
            // if we search in the specific block, we should just check the array
            return isset($this->_blockVariables[$block][$placeholder])? $block: '';
        } else {
            // _findParentBlocks returns an array, we need only the first element
            $parents = $this->_findParentBlocks($placeholder);
            return empty($parents)? '': $parents[0];
        }
    } // end func placeholderExists


    /**
     * Sets a callback function.
     *
     * Sigma templates can contain simple function calls. This means that the
     * author of the template can add a special placeholder to it:
     * <pre>
     * func_h1("embedded in h1")
     * </pre>
     * Sigma will parse the template for these placeholders and will allow
     * you to define a callback function for them. Callback will be called
     * automatically when the block containing such function call is parse()'d.
     *
     * Please note that arguments to these template functions can contain
     * variable placeholders: func_translate('Hello, {username}'), but not
     * blocks or other function calls.
     *
     * This should NOT be used to add logic (except some presentation one) to
     * the template. If you use a lot of such callbacks and implement business
     * logic through them, then you're reinventing the wheel. Consider using
     * XML/XSLT, native PHP or some other template engine.
     *
     * <code>
     * function h_one($arg) {
     *    return '<h1>' . $arg . '</h1>';
     * }
     * ...
     * $tpl = new HTML_Template_Sigma( ... );
     * ...
     * $tpl->setCallbackFunction('h1', 'h_one');
     * </code>
     *
     * template:
     * <pre>
     * func_h1('H1 Headline');
     * </pre>
     *
     * @param string   $tplFunction  Function name in the template
     * @param callable $callback     A callback: anything that can be passed to call_user_func_array()
     * @param bool     $preserveArgs If true, then no variable substitution in arguments
     *                               will take place before function call
     *
     * @access public
     * @return mixed SIGMA_OK on success, error object on failure
     * @throws PEAR_Error
     */
    function setCallbackFunction($tplFunction, $callback, $preserveArgs = false)
    {
        if (!is_callable($callback)) {
            return $this->raiseError($this->errorMessage(SIGMA_INVALID_CALLBACK), SIGMA_INVALID_CALLBACK);
        }
        $this->_callback[$tplFunction] = array(
            'data'         => $callback,
            'preserveArgs' => $preserveArgs
        );
        return SIGMA_OK;
    } // end func setCallbackFunction


    /**
     * Returns a list of blocks within a template.
     *
     * If $recursive is false, it returns just a 'flat' array of $parent's
     * direct subblocks. If $recursive is true, it builds a tree of template
     * blocks using $parent as root. Tree structure is compatible with
     * PEAR::Tree's Memory_Array driver.
     *
     * @param string $parent    parent block name
     * @param bool   $recursive whether to return a tree of child blocks (true) or a 'flat' array (false)
     *
     * @access public
     * @return array a list of child blocks
     * @throws PEAR_Error
     */
    function getBlockList($parent = '__global__', $recursive = false)
    {
        if (!isset($this->_blocks[$parent])) {
            return $this->raiseError($this->errorMessage(SIGMA_BLOCK_NOT_FOUND, $parent), SIGMA_BLOCK_NOT_FOUND);
        }
        if (!$recursive) {
            return isset($this->_children[$parent])? array_keys($this->_children[$parent]): array();
        } else {
            $ret = array('name' => $parent);
            if (!empty($this->_children[$parent])) {
                $ret['children'] = array();
                foreach (array_keys($this->_children[$parent]) as $child) {
                    $ret['children'][] = $this->getBlockList($child, true);
                }
            }
            return $ret;
        }
    }


    /**
     * Returns a list of placeholders within a block.
     *
     * Only 'normal' placeholders are returned, not auto-created ones.
     *
     * @param string $block block name
     *
     * @access public
     * @return array a list of placeholders
     * @throws PEAR_Error
     */
    function getPlaceholderList($block = '__global__')
    {
        if (!isset($this->_blocks[$block])) {
            return $this->raiseError($this->errorMessage(SIGMA_BLOCK_NOT_FOUND, $block), SIGMA_BLOCK_NOT_FOUND);
        }
        $ret = array();
        foreach ($this->_blockVariables[$block] as $var => $v) {
            if ('__' != substr($var, 0, 2) || '__' != substr($var, -2)) {
                $ret[] = $var;
            }
        }
        return $ret;
    }


    /**
     * Clears the variables
     *
     * Global variables are not affected. The method is useful when you add
     * a lot of variables via setVariable() and are not sure whether all of
     * them appear in the block you parse(). If you clear the variables after
     * parse(), you don't risk them suddenly showing up in other blocks.
     *
     * @access public
     * @return void
     * @see    setVariable()
     */
    function clearVariables()
    {
        $this->_variables = array();
    }


    //------------------------------------------------------------
    //
    // Private methods follow
    //
    //------------------------------------------------------------

     /**
      * Builds the variable names for nested variables
      *
      * @param string $name  variable name
      * @param array  $array value array
      *
      * @access private
      * @return array array with 'name.key' keys
      */
    function _flattenVariables($name, $array)
    {
        $ret = array();
        foreach ($array as $key => $value) {
            if (is_array($value)) {
                $ret = array_merge($ret, $this->_flattenVariables($name . '.' . $key, $value));
            } else {
                $ret[$name . '.' . $key] = $value;
            }
        }
        return $ret;
    }


    /**
     * Recursively builds a list of all variables within a block.
     *
     * Also calls _buildFunctionlist() for each block it visits
     *
     * @param string $block block name
     *
     * @access private
     * @return mixed SIGMA_OK on success, error object on failure
     * @see    _buildFunctionlist()
     */
    function _buildBlockVariables($block = '__global__')
    {
        $this->_blockVariables[$block] = array();
        $this->_functions[$block]      = array();
        preg_match_all($this->variablesRegExp, $this->_blocks[$block], $regs, PREG_SET_ORDER);
        foreach ($regs as $match) {
            $this->_blockVariables[$block][$match[1]] = true;
            if (!empty($match[3])) {
                $funcData = array(
                    'name' => $match[3],
                    'args' => array($this->openingDelimiter . $match[1] . $this->closingDelimiter)
                );
                $funcId   = substr(md5(serialize($funcData)), 0, 10);

                // update block info
                $this->_blocks[$block] = str_replace(
                    $match[0],
                    $this->openingDelimiter . '__function_' . $funcId . '__' . $this->closingDelimiter,
                    $this->_blocks[$block]
                );
                $this->_blockVariables[$block]['__function_' . $funcId . '__'] = true;
                $this->_functions[$block][$funcId] = $funcData;
            }
        }
        if (SIGMA_OK != ($res = $this->_buildFunctionlist($block))) {
            return $res;
        }
        if (isset($this->_children[$block]) && is_array($this->_children[$block])) {
            foreach ($this->_children[$block] as $child => $v) {
                if (SIGMA_OK != ($res = $this->_buildBlockVariables($child))) {
                    return $res;
                }
            }
        }
        return SIGMA_OK;
    }


    /**
     * Recusively builds a list of all blocks within the template.
     *
     * @param string $string template to be scanned
     *
     * @access private
     * @return mixed array of block names on success or error object on failure
     * @throws PEAR_Error
     * @see    $_blocks
     */
    function _buildBlocks($string)
    {
        $blocks = array();
        if (preg_match_all($this->blockRegExp, $string, $regs, PREG_SET_ORDER)) {
            foreach ($regs as $match) {
                $blockname    = $match[1];
                $blockcontent = $match[2];
                if (isset($this->_blocks[$blockname]) || isset($blocks[$blockname])) {
                    return $this->raiseError(
                        $this->errorMessage(SIGMA_BLOCK_DUPLICATE, $blockname), SIGMA_BLOCK_DUPLICATE
                    );
                }
                $this->_blocks[$blockname] = $blockcontent;
                $blocks[$blockname] = true;
                $inner              = $this->_buildBlocks($blockcontent);
                if (is_a($inner, 'PEAR_Error')) {
                    return $inner;
                }
                foreach ($inner as $name => $v) {
                    $pattern     = sprintf('@<!--\s+BEGIN\s+%s\s+-->(.*)<!--\s+END\s+%s\s+-->@sm', $name, $name);
                    $replacement = $this->openingDelimiter.'__'.$name.'__'.$this->closingDelimiter;
                    $this->_children[$blockname][$name] = true;
                    $this->_blocks[$blockname]          = preg_replace(
                        $pattern, $replacement, $this->_blocks[$blockname]
                    );
                }
            }
        }
        return $blocks;
    }


    /**
     * Resets the object's properties, used before processing a new template
     *
     * @param boolean $removeUnknownVariables remove unknown/unused variables?
     * @param boolean $removeEmptyBlocks      remove empty blocks?
     *
     * @access private
     * @return void
     * @see    setTemplate(), loadTemplateFile()
     */
    function _resetTemplate($removeUnknownVariables = true, $removeEmptyBlocks = true)
    {
        $this->removeUnknownVariables = $removeUnknownVariables;
        $this->removeEmptyBlocks      = $removeEmptyBlocks;
        $this->currentBlock           = '__global__';
        $this->_variables             = array();
        $this->_blocks                = array();
        $this->_children              = array();
        $this->_parsedBlocks          = array();
        $this->_touchedBlocks         = array();
        $this->_functions             = array();
        $this->flagGlobalParsed       = false;
    } // _resetTemplate


    /**
     * Checks whether we have a "prepared" template cached.
     *
     * If we do not do caching, always returns false
     *
     * @param string $filename source filename
     *
     * @access private
     * @return bool yes/no
     * @see    loadTemplatefile(), addBlockfile(), replaceBlockfile()
     */
    function _isCached($filename)
    {
        if (null === $this->_cacheRoot) {
            return false;
        }
        $cachedName = $this->_cachedName($filename);
        $sourceName = $this->fileRoot . $filename;
        // if $sourceName does not exist, error will be thrown later
        return false !== ($sourceTime = @filemtime($sourceName)) && @filemtime($cachedName) === $sourceTime;
    } // _isCached


    /**
     * Loads a "prepared" template file
     *
     * @param string $filename    filename
     * @param string $block       block name
     * @param string $placeholder variable placeholder to replace by a block
     *
     * @access private
     * @return mixed SIGMA_OK on success, error object on failure
     * @see    loadTemplatefile(), addBlockfile(), replaceBlockfile()
     */
    function _getCached($filename, $block = '__global__', $placeholder = '')
    {
        // the same checks are done in addBlock()
        if (!empty($placeholder)) {
            if (isset($this->_blocks[$block])) {
                return $this->raiseError($this->errorMessage(SIGMA_BLOCK_EXISTS, $block), SIGMA_BLOCK_EXISTS);
            }
            $parents = $this->_findParentBlocks($placeholder);
            if (0 == count($parents)) {
                return $this->raiseError(
                    $this->errorMessage(SIGMA_PLACEHOLDER_NOT_FOUND, $placeholder), SIGMA_PLACEHOLDER_NOT_FOUND
                );

            } elseif (count($parents) > 1) {
                return $this->raiseError(
                    $this->errorMessage(SIGMA_PLACEHOLDER_DUPLICATE, $placeholder), SIGMA_PLACEHOLDER_DUPLICATE
                );
            }
        }
        if (false === ($content = @file_get_contents($this->_cachedName($filename)))) {
            return $this->raiseError(
                $this->errorMessage(SIGMA_TPL_NOT_FOUND, $this->_cachedName($filename)), SIGMA_TPL_NOT_FOUND
            );
        }
        $cache = unserialize($content);
        if ('__global__' != $block) {
            $this->_blocks[$block]         = $cache['blocks']['__global__'];
            $this->_blockVariables[$block] = $cache['variables']['__global__'];
            $this->_children[$block]       = $cache['children']['__global__'];
            $this->_functions[$block]      = $cache['functions']['__global__'];
            unset(
                $cache['blocks']['__global__'], $cache['variables']['__global__'],
                $cache['children']['__global__'], $cache['functions']['__global__']
            );
        }
        $this->_blocks         = array_merge($this->_blocks, $cache['blocks']);
        $this->_blockVariables = array_merge($this->_blockVariables, $cache['variables']);
        $this->_children       = array_merge($this->_children, $cache['children']);
        $this->_functions      = array_merge($this->_functions, $cache['functions']);

        // the same thing gets done in addBlockfile()
        if (!empty($placeholder)) {
            $this->_replacePlaceholder($parents[0], $placeholder, $block);
        }
        // pull the triggers, if any
        if (isset($cache['triggers'])) {
            return $this->_pullTriggers($cache['triggers']);
        }
        return SIGMA_OK;
    } // _getCached


    /**
     * Returns a full name of a "prepared" template file
     *
     * @param string $filename source filename, relative to root directory
     *
     * @access private
     * @return string filename
     */
    function _cachedName($filename)
    {
        if (OS_WINDOWS) {
            $filename = str_replace(array('/', '\\', ':'), array('__', '__', ''), $filename);
        } else {
            $filename = str_replace('/', '__', $filename);
        }
        return $this->_cacheRoot. $filename. '.it';
    } // _cachedName


    /**
     * Writes a prepared template file.
     *
     * Even if NO caching is going on, this method has a side effect: it calls
     * the _pullTriggers() method and thus loads all files added via <!-- INCLUDE -->
     *
     * @param string $filename source filename, relative to root directory
     * @param string $block    name of the block to save into file
     *
     * @access private
     * @return mixed SIGMA_OK on success, error object on failure
     */
    function _writeCache($filename, $block)
    {
        // do not save anything if no cache dir, but do pull triggers
        if (null !== $this->_cacheRoot) {
            $cache = array(
                'blocks'    => array(),
                'variables' => array(),
                'children'  => array(),
                'functions' => array()
            );
            $cachedName = $this->_cachedName($filename);
            $this->_buildCache($cache, $block);
            if ('__global__' != $block) {
                foreach (array_keys($cache) as $k) {
                    $cache[$k]['__global__'] = $cache[$k][$block];
                    unset($cache[$k][$block]);
                }
            }
            if (isset($this->_triggers[$block])) {
                $cache['triggers'] = $this->_triggers[$block];
            }
            $res = $this->_writeFileAtomically($cachedName, serialize($cache));
            if (is_a($res, 'PEAR_Error')) {
                return $res;
            }
            @touch($cachedName, @filemtime($this->fileRoot . $filename));
        }
        // now pull triggers
        if (isset($this->_triggers[$block])) {
            if (SIGMA_OK !== ($res = $this->_pullTriggers($this->_triggers[$block]))) {
                return $res;
            }
            unset($this->_triggers[$block]);
        }
        return SIGMA_OK;
    } // _writeCache

    /**
     * Atomically writes given content to a given file
     *
     * The method first creates a temporary file in the cache directory and
     * then renames it to the final name. This should prevent creating broken
     * cache files when there is no space left on device (bug #19220) or reading
     * incompletely saved files in another process / thread.
     *
     * The same idea is used in Twig, Symfony's Filesystem component, etc.
     *
     * @param string $fileName Name of the file to write
     * @param string $content  Content to write
     *
     * @access private
     * @return mixed SIGMA_OK on success, error object on failure
     * @link http://pear.php.net/bugs/bug.php?id=19220
     */
    function _writeFileAtomically($fileName, $content)
    {
        $dirName = dirname($fileName);
        $tmpFile = tempnam($dirName, basename($fileName));

        if (function_exists('file_put_contents')) {
            if (false === @file_put_contents($tmpFile, $content)) {
                return $this->raiseError($this->errorMessage(SIGMA_CACHE_ERROR, $fileName), SIGMA_CACHE_ERROR);
            }

        } else {
            // Fall back to previous solution
            if (!($fh = @fopen($tmpFile, 'wb'))) {
                return $this->raiseError($this->errorMessage(SIGMA_CACHE_ERROR, $fileName), SIGMA_CACHE_ERROR);
            }
            if (!fwrite($fh, $content)) {
                return $this->raiseError($this->errorMessage(SIGMA_CACHE_ERROR, $fileName), SIGMA_CACHE_ERROR);
            }
            fclose($fh);
        }

        if (!OS_WINDOWS || version_compare(phpversion(), '5.2.6', '>=')) {
            if (@rename($tmpFile, $fileName)) {
                return SIGMA_OK;
            }

        } else {
            // rename() to an existing file will not work on Windows before PHP 5.2.6,
            // so we need to copy, which isn't that atomic, but better than writing directly to $fileName
            // https://bugs.php.net/bug.php?id=44805
            if (@copy($tmpFile, $fileName) && @unlink($tmpFile)) {
                return SIGMA_OK;
            }
        }

        return $this->raiseError($this->errorMessage(SIGMA_CACHE_ERROR, $fileName), SIGMA_CACHE_ERROR);
    }

    /**
     * Builds an array of template data to be saved in prepared template file
     *
     * @param array  &$cache template data
     * @param string $block  block to add to the array
     *
     * @access private
     * @return void
     */
    function _buildCache(&$cache, $block)
    {
        if (!$this->_options['trim_on_save']) {
            $cache['blocks'][$block] = $this->_blocks[$block];
        } else {
            $cache['blocks'][$block] = preg_replace(
                array('/^\\s+/m', '/\\s+$/m', '/(\\r?\\n)+/'),
                array('', '', "\n"),
                $this->_blocks[$block]
            );
        }
        $cache['variables'][$block] = $this->_blockVariables[$block];
        $cache['functions'][$block] = isset($this->_functions[$block])? $this->_functions[$block]: array();
        if (!isset($this->_children[$block])) {
            $cache['children'][$block] = array();
        } else {
            $cache['children'][$block] = $this->_children[$block];
            foreach (array_keys($this->_children[$block]) as $child) {
                $this->_buildCache($cache, $child);
            }
        }
    }


    /**
     * Recursively removes all data belonging to a block
     *
     * @param string  $block       block name
     * @param boolean $keepContent true if the parsed contents of the block should be kept
     *
     * @access private
     * @return mixed SIGMA_OK on success, error object on failure
     * @see    replaceBlock(), replaceBlockfile()
     */
    function _removeBlockData($block, $keepContent = false)
    {
        if (!isset($this->_blocks[$block])) {
            return $this->raiseError($this->errorMessage(SIGMA_BLOCK_NOT_FOUND, $block), SIGMA_BLOCK_NOT_FOUND);
        }
        if (!empty($this->_children[$block])) {
            foreach (array_keys($this->_children[$block]) as $child) {
                $this->_removeBlockData($child, false);
            }
            unset($this->_children[$block]);
        }
        unset($this->_blocks[$block]);
        unset($this->_blockVariables[$block]);
        unset($this->_hiddenBlocks[$block]);
        unset($this->_touchedBlocks[$block]);
        unset($this->_functions[$block]);
        if (!$keepContent) {
            unset($this->_parsedBlocks[$block]);
        }
        return SIGMA_OK;
    }


    /**
     * Returns the names of the blocks where the variable placeholder appears
     *
     * @param string $variable variable name
     *
     * @access private
     * @return array block names
     * @see    addBlock(), addBlockfile(), placeholderExists()
     */
    function _findParentBlocks($variable)
    {
        $parents = array();
        foreach ($this->_blockVariables as $blockname => $varnames) {
            if (!empty($varnames[$variable])) {
                $parents[] = $blockname;
            }
        }
        return $parents;
    }


    /**
     * Replaces a variable placeholder by a block placeholder.
     *
     * Of course, it also updates the necessary arrays
     *
     * @param string $parent      name of the block containing the placeholder
     * @param string $placeholder variable name
     * @param string $block       block name
     *
     * @access private
     * @return void
     */
    function _replacePlaceholder($parent, $placeholder, $block)
    {
        $this->_children[$parent][$block] = true;
        $this->_blockVariables[$parent]['__'.$block.'__'] = true;
        $this->_blocks[$parent] = str_replace(
            $this->openingDelimiter . $placeholder . $this->closingDelimiter,
            $this->openingDelimiter . '__' . $block . '__' . $this->closingDelimiter,
            $this->_blocks[$parent]
        );
        unset($this->_blockVariables[$parent][$placeholder]);
    }


    /**
     * Callback generating a placeholder to replace an <!-- INCLUDE filename --> statement
     *
     * @param array $matches Matches from preg_replace_callback() call
     *
     * @access private
     * @return string  a placeholder
     */
    function _makeTrigger($matches)
    {
        $name = 'trigger_' . substr(md5($matches[1] . ' ' . uniqid($this->_triggerBlock)), 0, 10);
        $this->_triggers[$this->_triggerBlock][$name] = $matches[1];
        return $this->openingDelimiter . $name . $this->closingDelimiter;
    }


    /**
     * Replaces the "trigger" placeholders by the matching file contents.
     *
     * @param array $triggers array ('trigger placeholder' => 'filename')
     *
     * @access private
     * @return mixed SIGMA_OK on success, error object on failure
     * @see _makeTrigger(), addBlockfile()
     */
    function _pullTriggers($triggers)
    {
        foreach ($triggers as $placeholder => $filename) {
            if (SIGMA_OK !== ($res = $this->addBlockfile($placeholder, $placeholder, $filename))) {
                return $res;
            }
            // we actually do not need the resultant block...
            $parents = $this->_findParentBlocks('__' . $placeholder . '__');
            // merge current block's children and variables with the parent's ones
            if (isset($this->_children[$placeholder])) {
                $this->_children[$parents[0]] = array_merge(
                    $this->_children[$parents[0]], $this->_children[$placeholder]
                );
            }
            $this->_blockVariables[$parents[0]] = array_merge(
                $this->_blockVariables[$parents[0]], $this->_blockVariables[$placeholder]
            );
            if (isset($this->_functions[$placeholder])) {
                $this->_functions[$parents[0]] = array_merge(
                    $this->_functions[$parents[0]], $this->_functions[$placeholder]
                );
            }
            // substitute the block's contents into parent's
            $this->_blocks[$parents[0]] = str_replace(
                $this->openingDelimiter . '__' . $placeholder . '__' . $this->closingDelimiter,
                $this->_blocks[$placeholder],
                $this->_blocks[$parents[0]]
            );
            // remove the stuff that is no more needed
            unset(
                $this->_blocks[$placeholder], $this->_blockVariables[$placeholder],
                $this->_children[$placeholder], $this->_functions[$placeholder],
                $this->_children[$parents[0]][$placeholder],
                $this->_blockVariables[$parents[0]]['__' . $placeholder . '__']
            );
        }
        return SIGMA_OK;
    }


    /**
     * Builds a list of functions in a block.
     *
     * @param string $block Block name
     *
     * @access private
     * @return mixed SIGMA_OK on success, error object on failure
     * @see    _buildBlockVariables()
     */
    function _buildFunctionlist($block)
    {
        $template = $this->_blocks[$block];
        $this->_blocks[$block] = '';

        while (preg_match($this->functionRegExp, $template, $regs)) {
            $this->_blocks[$block] .= substr($template, 0, strpos($template, $regs[0]));
            $template = substr($template, strpos($template, $regs[0]) + strlen($regs[0]));

            $state    = 1;
            $arg      = '';
            $quote    = '';
            $funcData = array(
                'name' => $regs[1],
                'args' => array()
            );
            for ($i = 0, $len = strlen($template); $i < $len; $i++) {
                $char = $template[$i];
                switch ($state) {
                case 0:
                case -1:
                    break 2;

                case 1:
                    if (')' == $char) {
                        $state = 0;
                    } elseif (',' == $char) {
                        $error = 'Unexpected \',\'';
                        $state = -1;
                    } elseif ('\'' == $char || '"' == $char) {
                        $quote = $char;
                        $state = 5;
                    } elseif (!ctype_space($char)) {
                        $arg  .= $char;
                        $state = 3;
                    }
                    break;

                case 2:
                    $arg = '';
                    if (',' == $char || ')' == $char) {
                        $error = 'Unexpected \'' . $char . '\'';
                        $state = -1;
                    } elseif ('\'' == $char || '"' == $char) {
                        $quote = $char;
                        $state = 5;
                    } elseif (!ctype_space($char)) {
                        $arg  .= $char;
                        $state = 3;
                    }
                    break;

                case 3:
                    if (')' == $char) {
                        $funcData['args'][] = rtrim($arg);
                        $state  = 0;
                    } elseif (',' == $char) {
                        $funcData['args'][] = rtrim($arg);
                        $state = 2;
                    } elseif ('\'' == $char || '"' == $char) {
                        $quote = $char;
                        $arg  .= $char;
                        $state = 4;
                    } else {
                        $arg  .= $char;
                    }
                    break;

                case 4:
                    $arg .= $char;
                    if ($quote == $char) {
                        $state = 3;
                    }
                    break;

                case 5:
                    if ('\\' == $char) {
                        $state = 6;
                    } elseif ($quote == $char) {
                        $state = 7;
                    } else {
                        $arg .= $char;
                    }
                    break;

                case 6:
                    $arg  .= $char;
                    $state = 5;
                    break;

                case 7:
                    if (')' == $char) {
                        $funcData['args'][] = $arg;
                        $state  = 0;
                    } elseif (',' == $char) {
                        $funcData['args'][] = $arg;
                        $state  = 2;
                    } elseif (!ctype_space($char)) {
                        $error = 'Unexpected \'' . $char . '\' (expected: \')\' or \',\')';
                        $state = -1;
                    }
                    break;
                } // switch
            } // for
            if (0 != $state) {
                return $this->raiseError(
                    $this->errorMessage(
                        SIGMA_CALLBACK_SYNTAX_ERROR,
                        (empty($error) ? 'Unexpected end of input' : $error)
                        . ' in ' . $regs[0] . substr($template, 0, $i)
                    ),
                    SIGMA_CALLBACK_SYNTAX_ERROR
                );

            } else {
                $funcId   = 'f' . substr(md5(serialize($funcData)), 0, 10);
                $template = substr($template, $i);

                $this->_blocks[$block] .= $this->openingDelimiter . '__function_' . $funcId
                                          . '__' . $this->closingDelimiter;
                $this->_blockVariables[$block]['__function_' . $funcId . '__'] = true;
                $this->_functions[$block][$funcId] = $funcData;
            }
        } // while
        $this->_blocks[$block] .= $template;
        return SIGMA_OK;
    } // end func _buildFunctionlist


    /**
     * Replaces an opening delimiter by a special string.
     *
     * Used to implement $_options['preserve_data'] logic
     *
     * @param string $str String possibly containing opening delimiters
     *
     * @access private
     * @return string
     */
    function _preserveOpeningDelimiter($str)
    {
        return (false === strpos($str, $this->openingDelimiter))
               ? $str
               : str_replace(
                   $this->openingDelimiter,
                   $this->openingDelimiter . '%preserved%' . $this->closingDelimiter, $str
               );
    }


    /**
     * Quotes the string so that it can be used in Javascript string constants
     *
     * @param string $value String to be used in JS
     *
     * @access private
     * @return string
     */
    function _jsEscape($value)
    {
        return strtr(
            $value,
            array(
                "\r" => '\r',    "'"  => "\\x27", "\n" => '\n',
                '"'  => '\\x22', "\t" => '\t',    '\\' => '\\\\'
            )
        );
    }


    /**
     * Wrapper around htmlspecialchars() needed to use the charset option
     *
     * @param string $value String with special characters
     *
     * @access private
     * @return string
     */
    function _htmlspecialchars($value)
    {
        return htmlspecialchars($value, ENT_COMPAT, $this->_options['charset']);
    }


    /**
     * Wrapper around htmlentities() needed to use the charset option
     *
     * @param string $value String with special characters
     *
     * @access private
     * @return string
     */
    function _htmlentities($value)
    {
        return htmlentities($value, ENT_COMPAT, $this->_options['charset']);
    }
}
?>
