<?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 of the form ~name [arg...]~, 
# optionally wrapped in HTML comments (which will be removed along with 
# the tag markers when the template is filled out).
#
# { and } as the final argument mark those tags as being the start and 
# end of a sub-template (for optional or repeated sections).  All other 
# tags represent slots to be directly filled by data values.  On a } 
# tag, the name is optional, but must match the corresponding { tag if 
# present.
#
# For a value tag, arguments represent encodings to be applied 
# successively.  For instance, ~foo html~ will encode it to be safe in 
# HTML ('&' to '&amp;', '<' to '&lt;', and so on).
#
# { tags can take one argument, which will call the corresponding 
# tem_auto_* function to munge the data, automating certain common use 
# cases.  See the comments on the tem_auto functions for more details.

require_once(__DIR__.'/'.'encode.php');
require_once(__DIR__.'/'.'file.php');
require_once(__DIR__.'/'.'misc.php');


# Top-Level Functions
# -------------------

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

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

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

# We parse the template string into a tree of strings and sub-templates.
# A template is a hash with a name string, a pieces array, and possibly 
# an args array.

function &parse_template($string) {
	$tem =& tem_push();
	$tem['pieces'] = array();
	$matches = preg_split('/(<!--)?(~[^~]*~)(?(1)-->)/', preg_replace('/<!--(~[^~]*~)-->/', '$1', $string), -1, PREG_SPLIT_DELIM_CAPTURE | PREG_SPLIT_NO_EMPTY);
	foreach($matches as $match) {
		if($match == '~~') $match = '~';
		if(substr($match,0,1) == '~' and strlen($match) > 2) {
			$args = explode(' ', substr($match,1,-1));

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

			if(last($args) == '{') {  # open block
				array_pop($args);  # drop '{'
				$tem =& tem_push($tem);              # create a new sub-template
				$tem['parent']['pieces'][] =& $tem;  # as a piece of the parent
				$tem['name'] = $name;
				$tem['pieces'] = array();
				$tem['args'] = $args;
			} elseif(last($args) == '}') {  # close block
				array_pop($args);  # drop '}'
				$cur = $tem['name'];
				if($name && $name != $cur) {
					die("Invalid template: tried to close '$name', but '$cur' is current.");
				}
				$tem =& $tem['parent'];
			} else {  # value slot
				$tem['pieces'][] = array('name' => $name, 'args' => $args);
			}
		} else {  # static string
			$tem['pieces'][] = $match;
		}
	}
	return $tem;
}

function fill_template($template, &$data, &$context = NULL) {
	$context =& tem_push($context);
	$context['data'] =& $data;

	foreach($template['pieces'] as $tem) {
		if(is_string($tem)) $output .= $tem;
		elseif($tem['pieces']) {  # sub-template
			$rows =& tem_row_data($tem, $context);
			$context['rows'] =& $rows;
			foreach($rows as $key => &$row) {
				$context['cur'] = $key;
				$output .= fill_template($tem, $row, $context);
			}
		} else {  # variable
			$output .= tem_encoded_data($tem, $context);
		}
	}
	$context =& $context['parent'];
	return $output;
}


# Implementation
# --------------


# To track our position in the template and in the data, we use a linked 
# stack structure.  Each node is a hash with a reference to the parent 
# node along with whatever other data you want to add.  For each stack, 
# you simply keep a variable with a reference to the top element.  Then 
# the push and pop operations are:

# $top =& tem_push($top);
# $top =& $top['parent'];

function &tem_push(&$stack = NULL) {
	static $refs = array();

	# Since a PHP reference is *not* a pointer to data, but a pointer to 
	# a variable (or array slot), we *have* to first put the new node in
	# $refs, and then reference it from $new.

	$refs[] = array();
	$new =& $refs[count($refs)-1];
	if($stack) $new['parent'] =& $stack;
	return $new;
}

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

# The data starts out as a nested set of key/value pairs, where the 
# values can be:

	# a string to fill a value slot
	# a hash to fill one instance of a sub-template
	# an array of hashes to fill multiple instances of a sub-template

# The middle form will be converted to the last form as we use it.

function tem_data_as_rows($value, $key) {
	if(is_array($value)) {
		# numeric keys
		if(array_key_exists(0, $value)) {
			if(is_array($value[0])) return $value;  # already array of hashes.
			else return columnize($value, $key);
		# key/value pairs -- expand sub-template once.
		} else return array($value);
	} elseif($value || $value === 0 || $value === '0' || $value === '') {
		# value -- expand sub-template once using only parent values
		return array(array());
	} else {
		# empty value -- don't expand sub-template
		return array();
	}
}

# To look up a key, we check each namespace (starting with the
# innermost one) until a value is found.

function tem_data_scope($key, $context) {
	static $refs = array();

	$scope = $context;
	do{
		if(array_key_exists($key, $scope['data'])) {
			return $scope;
		}
	} while($scope = $scope['parent']);

	# not found; return empty scope.
	$refs[] = array();
	$ret = array();
	$ret['parent'] =& $context;
	$ret['data'] =& last($refs);
	return $ret;
}

function tem_get_data($key, $context) {
	$scope = tem_data_scope($key, $context);
	if($scope) return $scope['data'][$key];
}

# Return the value for a tag as a set of rows to fill a sub-template.
# If $tag has an arg, call the tem_auto function to munge the data.
function &tem_row_data($tem, $context)
{
	$key = $tem['name'];
	$scope = tem_data_scope($key, $context);

	if(count($tem['args'])) {
		$auto_func = "tem_auto_" . $tem['args'][0];
		if (!function_exists($auto_func)) {
			die("ERROR: template auto function '$auto_func' not found.<br>\n");
		}
		# NAMESPACIFY $auto_func
	}
	if ($auto_func) {
		$value = $auto_func($scope['data'][$key], $key, $scope, $tem['args']);
	}
	else $value = $scope['data'][$key];

	$rows = tem_data_as_rows($value, $key);
	if(is_array($value)) $scope['data'][$key] = $rows;

	return $rows;
}

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


function is_sub_template(&$piece) {
	return is_array($piece) and $piece['pieces'];
}

function is_value_slot(&$piece) {
	return is_array($piece) and !$piece['pieces'];
}

# Return a hash containing the top-level sub-templates of tem.
function top_sub_templates($tem, $is_sub = 'is_sub_template') {
	function_exists($is_sub) or die("no such function '$is_sub'.");
	$subs = array();
	foreach($tem['pieces'] as $piece) {
		if($is_sub($piece)) {
			$subs[$piece['name']] = $piece;
		}
	}
	return $subs;
}

# merge $subs (sub_templates) into variables in $main (template)
function merge_sub_templates(&$main, &$subs) {
	foreach($main['pieces'] as &$piece) {
		if(is_array($piece)) { # not just text
			if($piece['pieces']) {
				# a sub-template in main
				merge_sub_templates($piece, $subs);
			} else {
				# a value-slot in main
				$sub = $subs[$piece['name']];
				if($sub and $sub['args'][0] != 'hide') {
					$piece = $subs[$piece['name']];
					$piece['parent'] =& $main;
				}
			}
		}
	}
	return $out;
}

# Replace values in $main with top-level templates from $tem.
function merge_templates(&$main, &$tem) {
	$subs = top_sub_templates($tem);

	merge_sub_templates($main, $subs);
}


# 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><!--~}~-->
# 		<!--~}~-->
# 	<!--~}~-->
#
function tem_auto_sep(&$value, $key, $context) {
	$rows =& $context['parent']['parent'];
	if($rows['cur'] != count($rows['rows'])-1)  # last row?
		return true;  # show once
}

# auto-show once, only when this is the first row of the parent
function tem_auto_last(&$value, $key, $context) {
	$rows =& $context['parent']['parent'];
	if($rows['cur'] == count($rows['rows'])-1)  # last row?
		return true;  # show once
}

# auto-show once, only when this is the last row of the parent
function tem_auto_first(&$value, $key, $context) {
	$rows =& $context['parent']['parent'];
	if($rows['cur'] == 0)  # first row?
		return true;  # show once
}

# 'show' sections will be shown unless the corresponding data
# value === false
function tem_auto_show(&$value) {
	if($value === null) return true;
	return $value;
}

# 'empty' sections will be shown only if the corresponding data value is the
# empty string
function tem_auto_empty(&$value) {
	if($value === '') return true;
	return null;
}

# 'nonempty' sections will not be shown if the corresponding data
# value is the empty string
function tem_auto_nonempty(&$value) {
	if($value === '') return null;
	return $value;
}

# 'unset' sections will not be shown if the corresponding data
# value is not set (opposite of default)
function tem_auto_unset(&$value) {
	if($value === null) {
		return '';
	} else {
		return null;
	}
}

# 'evenodd' sections are given an 'evenodd' attribute whose value
# alternates between 'even' and 'odd'.
function tem_auto_evenodd(&$values) {
	$even = true;
	if($values) foreach($values as &$value) {
		$value['evenodd'] = $even ? 'even' : 'odd';
		$even = !$even;
	}
	return $values;
}

# 'once' sections are shown exactly once if the value is set (and not at all
# otherwise.) This is useful when an array value would otherwise cause the
# section to be displayed multiple times.
function tem_auto_once(&$value) {
	if($value === null) return null;
	return true;
}

function tem_auto_once_if(&$value) {
	if($value) return true;
	return null;
}

# 'once' sections are shown exactly once if php evaluates the value to false
# (and not at all otherwise.) This is useful when an array value would
# otherwise cause the section to be displayed multiple times.
function tem_auto_once_else(&$value) {
	if($value) return null;
	return true;;
}


# Backward Compatibility
# ----------------------

function is_shown($piece) {
	return $piece['args'][0] == 'hide';
}

function is_shown_sub_template($piece) {
	return is_sub_template($piece) and is_shown($piece);
}

# Old-style templates don't show unless explicitly requested.
function tem_auto_hide(&$value, $key, $context) {
	unset($context['data'][$key]);
	return false;
}

# The old API is being used with the named sub-template,
# so hide it and insert a value slot for its expansion(s).
function &tem_is_old_sub($name, &$template) {
	foreach($template['pieces'] as $key => &$piece) {
		if(is_sub_template($piece)) {
			if($piece['name'] == $name) {
				if(!is_shown($piece)) {
					# hide template unless explicitly show()n.
					$piece['args'] = array('hide');
					# insert a value slot with the same name (for the expansion).
					$var = array('name' => $name, 'args' => array());
					array_splice($template['pieces'], $key, 0, array($var));
				}
				return $piece;
			}
			$tem = tem_is_old_sub($name, $piece);
			if($tem) return $tem;
		}
	}
	return false;
}

class tem {
	var $template;
	var $data; 

	function tem() {
		$this->template = array('pieces' => array());
		$this->data = array();
	}
	
	function set($key, $value = true) {
		$this->data[$key] = $value;
	}

	function sets($hash) {
		foreach($hash as $key => $value) {
			$this->set($key, $value);
		}
	}

	function append($key, $value) {
		$this->data[$key] .= $value;
	}

	function prepend($key, $value) {
		$this->data[$key] = $value . $this->data[$key];
	}

	function clear($key) {
		unset($this->data[$key]);
	}

	function get($key) {
		return $this->data[$key];
	}

	function show($name) {
		$tem = tem_is_old_sub($name, $this->template);
		if($tem) {
			$this->data[$name] .= fill_template($tem, $this->data);
		}
	}

	function show_separated($name) {
		if($this->get($name)) {
			$this->show($name . '_sep');
		}
		$this->show($name);
	}

	function load_str($str) {
		$this->template =& parse_template($str);
	}

	function load($filename) {
		$this->template =& parse_template_file($filename);
	}

	function run($tem = false) {
		if($tem) {
			if(strlen($tem < 150 && file_exists($tem))) $this->load($tem);
			else $this->load_str($tem);
		}

		return fill_template($this->template, $this->data);
	}

	function output($tem = false) {
		print($this->run($tem));
	}

	# merge top-level sub-templates of $tem (object) into $this,
	# supporting both new and old semantics.
	function merge($tem) {
		# append expansions to $this->data (old style)

		$subs = $tem->top_subs('is_shown_sub_template');
		if($subs) foreach($subs as $name => $val) {
			$this->append($name, $val);
			unset($tem->data[$name]);  # so array_merge() won't overwrite things
		}

		# merge the data arrays and template trees (new style)
		$this->data = array_merge($this->data, $tem->data);
		merge_templates($this->template, $tem->template);
	}

	# see merge() above
	function merge_file($filename) {
		$other_tem = new tem();
		$other_tem->load($filename);
		$this->merge($other_tem);
	}

	function top_sub_names($is_sub = 'is_sub_template') {
		return array_keys(top_sub_templates($this->template, $is_sub));
	}

	function top_subs($is_sub = 'is_sub_template') {
		$ret = array();
		$names = $this->top_sub_names($is_sub);
		foreach($names as $name) {
			$ret[$name] = $this->get($name);
		}
		return $ret;
	}

	# old name for show (deprecated)
	function sub($name) {
		$this->show($name);
	}
}

function tem_init() {
	if(!$GLOBALS['wfpl_template']) {
		$GLOBALS['wfpl_template'] = new tem();
	}
}

function tem_append($key, $value) {
	tem_init();
	$GLOBALS['wfpl_template']->append($key, $value);
}

function tem_prepend($key, $value) {
	tem_init();
	$GLOBALS['wfpl_template']->prepend($key, $value);
}

function tem_set($key, $value = true) {
	tem_init();
	$GLOBALS['wfpl_template']->set($key, $value);
}

function tem_sets($hash) {
	tem_init();
	$GLOBALS['wfpl_template']->sets($hash);
}

function tem_get($key) {
	tem_init();
	return $GLOBALS['wfpl_template']->get($key);
}

function tem_run($tem = false) {
	tem_init();
	return $GLOBALS['wfpl_template']->run($tem);
}

function tem_show($name) {
	tem_init();
	return $GLOBALS['wfpl_template']->show($name);
}

function tem_show_separated($name) {
	tem_init();
	$GLOBALS['wfpl_template']->show_separated($name);
}

function tem_load($filename) {
	tem_init();
	$GLOBALS['wfpl_template']->load($filename);
}

function tem_merge($tem) {
	tem_init();
	$GLOBALS['wfpl_template']->merge($tem);
}

function tem_merge_file($filename) {
	tem_init();
	$GLOBALS['wfpl_template']->merge_file($filename);
}

function tem_output($filename = false) {
	tem_init();
	$GLOBALS['wfpl_template']->output($filename);
}

function tem_top_subs() {
	tem_init();
	return $GLOBALS['wfpl_template']->top_subs();
}

function tem_top_sub_names() {
	tem_init();
	return $GLOBALS['wfpl_template']->top_sub_names();
}

function tem_load_new($filename) {
	$old = $GLOBALS['wfpl_template'];
	$GLOBALS['wfpl_template'] = new tem();
	$GLOBALS['wfpl_template']->load($filename);
	return $old;
}

# deprecated (old name for show)
function tem_sub($name) {
	tem_show($name);
}

?>