<?php

#  Copyright (C) 2008,2009 Joshua Grams <josh@qualdan.com>
#
#  This program is free software: you can redistribute it and/or modify
#  it under the terms of the GNU General Public License as published by
#  the Free Software Foundation, either version 3 of the License, or
#  (at your option) any later version.
#  
#  This program is distributed in the hope that it will be useful,
#  but WITHOUT ANY WARRANTY; without even the implied warranty of
#  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
#  GNU General Public License for more details.
#  
#  You should have received a copy of the GNU General Public License
#  along with this program.  If not, see <http://www.gnu.org/licenses/>.


# This is a simple template-handling system.  You pass it a big data 
# structure with key/value pairs, and a template string to fill out.
#
# Within a template, it recognizes tags delimited by tildes (~).  When 
# the template is filled out, the tags will be replaced with the 
# corresponding data.  Tags ending with '?' and '.' mark the start and 
# end of a sub-template (for optional or repeated text), and can be 
# wrapped in HTML comments (which will be removed along with the tags
# when the template is filled out).

require_once('code/wfpl/encode.php');
require_once('code/wfpl/file.php');
require_once('code/wfpl/misc.php');


# Public functions
# ----------------

function template($data, $template) {
	return fill_template($data, parse_template($template));
}

function template_file($data, $filename) {
	return fill_template($data, parse_template_file($filename));
}

function parse_template_file($filename) {
	return parse_template(file_get_contents($filename));
}

# First we take the template string and break it up into an array 
# of strings and sub-arrays.  The first item in a sub-array is the name
# of the value or sub-template.

function parse_template($string) {
	# Don't mess with the $stack/$tem assignments!  Since
	# PHP references point to the variable, not the data,
	# it really does have to be written exactly like this.
	$stack[] = array('name' => 'root', 'pieces' => array());
   	$tem = &last($stack);
	# note: for some reason this captures '<!--' but not '-->'.
	$matches = preg_split("/(<!--)?(~[^~]*~)(?(1)-->)/", $string, -1, PREG_SPLIT_DELIM_CAPTURE);
	foreach($matches as $match) {
		if(substr($match,0,1) == '~') {
			$args = explode(' ', substr($match,1,-1));

			if(count($args) == 1 and $args[0] == '}') $name = '';
			else $name = array_shift($args);

			if(last($args) == '{') {  # open block
				array_pop($args);
				$stack[] = array('name' => $name, 'pieces' => array(), 'args' => $args);
				$tem['pieces'][] = &last($stack);
				$tem = &last($stack);
			} elseif(last($args) == '}') {  # close block
				array_pop($args);
				$cur = $stack[count($stack)-1]['name'];
				if($name && $name != $cur) {
				   	die("Invalid template: tried to close '$name', but '$cur' is current.");
				}
				array_pop($stack); $tem = &last($stack);
			} else {  # value slot
				$tem['pieces'][] = array('name' => $name, 'args' => $args);
			}
		} elseif($match and $match != '<!--') {  # static string
			$tem['pieces'][] = $match;
		}
	}
	return $tem;
}

# Then we do a depth-first traversal of the template tree,
# replacing all tags with the data values.

function fill_template($data, $template, $context = NULL, $keychain = NULL) {
	$context[] = $data;
	foreach($template['pieces'] as $piece) {
		if(is_string($piece)) $output .= $piece;
		else {
			if($piece['pieces']) {  # sub-template
				$keychain[] = $piece['name'];
				$rows = tem_get_rows($piece, $context, $keychain);
				foreach($rows as $key => $row) {
					$keychain[] = $key;
					$output .= fill_template($row, $piece, $context, $keychain);
					array_pop($keychain);
				}
				array_pop($keychain);
			} else $output .= tem_get_enc($piece, $context);
		}
	}
	return $output;
}


# Replace top-level values in $main with top-level templates from $tem.
function merge_templates($main, $tem) {
	$out = array('name' => $main['name'], 'pieces' => array());

	$subs = top_sub_templates($tem);

	foreach($main['pieces'] as $piece) {
		if(is_array($piece) and !$piece['pieces'] and $subs[$piece['name']]) {
			$piece = $subs[$piece['name']];
		}
		$out['pieces'][] = $piece;
	}
	return $out;
}


# tem_auto functions
# ------------------
#
# If a { tag has an argument, the corresponding tem_auto function is called.
# This allows it to mangle the data to automate some common cases.

# 'sep' (separator) sections will be shown for all but the last parent row.
# Sample usage:
# 	<!--~rows~-->
# 		<!--~row~-->
# 			row content...
# 			<!--~separator sep {~--><hr><!--~separator }"-->
# 		<!--~row~-->
# 	<!--~rows~-->
#
function tem_auto_sep($piece, $context, $keychain) {
	list($name, $index, $this_name) = array_slice($keychain, -3);
	$array = tem_get($name, $context);
	if($index != count($array)-1) return true;
}

# 'once' sections will be shown once unless the corresponding data value
# is false.  We check only for false; 0 or '' will not work.

function tem_auto_once($piece, $context, $keychain) {
	$value = tem_get(array_pop($keychain), $context);
	if($value !== false) return true;
}

# 'evenodd' sections are given an 'evenodd' attribute whose value
# alternates between 'even' and 'odd'.

function tem_auto_evenodd($piece, $context, $keychain) {
	$rows = tem_get(array_pop($keychain), $context);
	$even = 0;
	$text = array('even', 'odd');
	foreach($rows as $key => $value) {
		$rows[$key]['evenodd'] = $text[$even];
		$even = 1 - $even;
	}
	return $rows;
}


# Internal functions
# ------------------
#
# Of course, nothing stops you from using these, but I don't know
# why you would want to...


# Convert value to array of hashes for use in sub-template expansion.
# This adds flexibility to how you represent your data.
function tem_value_as_rows($value) {
	if(is_array($value)) {
		# numeric keys, is already array of arrays -- expand sub-template for each.
		if(array_key_exists(0, $value)) return $value;
		# key/value pairs -- expand sub-template once.
		else return array($value);
	} elseif($value) {
		# value -- expand sub-template once using only parent values
		return array(array());
	} else {
		# empty value -- don't expand sub-template
		return array();
	}
}

# Search the current context and return the value for key.
function tem_get($key, $context) {
	while($context) {
		$data = array_pop($context);
		if(array_key_exists($key, $data)) return $data[$key];
	}
}

# Return the value for a tag as a set of rows to fill a sub-template.
# If $tag has an arg, call the tem_auto function to munge the data.
function tem_get_rows($tag, $context, $keychain)
{
	if(count($tag['args'])) {
		$func = "tem_auto_" . $tag['args'][0];
		if(function_exists($func)) $value = $func($tag, $context, $keychain);
		else die("ERROR: template auto function '$func' not found.<br>\n");
	} else $value = tem_get($tag['name'], $context);

	return tem_value_as_rows($value);
}

# Return the value for a tag as an encoded string.
function tem_get_enc($tag, $context)
{
	$key = $tag['name'];
	$value = tem_get($key, $context);
	foreach($tag['args'] as $encoding) {
		$func = "enc_$encoding";
		if(function_exists($func)) $value = $func($value, $key);
		else die("ERROR: encoder function '$func' not found.<br>\n");
	}
	return $value;
}

function top_sub_templates($tem) {
	$subs = array();
	foreach($tem['pieces'] as $piece) {
		if(is_array($piece) and $piece['pieces']) {
		   	$subs[$piece['name']] = $piece;
		}
	}
	return $subs;
}

?>