Algorithmic Advent: 24 – Value object stack parser (PHP)
<?php
/**
* A simple value object (VO)
*
*/
class MyVO
{
// Section title
public $title;
// Array of key->value mappings
public $data;
}
/**
* Simple tree structure to hold arbitrary data
*
*/
class TreeNode
{
protected $_data;
protected $_children;
public function __construct()
{
$this->_children = array();
$this->_data = array();
}
public function addChild(TreeNode $child)
{
$this->_children[] = $child;
}
public function getChildren()
{
return $this->_children;
}
public function setValue($key, $value)
{
$this->_data[$key] = $value;
}
public function getValue($key)
{
return (isset($this->_data[$key]) ? $this->_data[$key] : null);
}
}
/**
* Standard PHP doesn't seem to contain a peek function for arrays
*
* @param array $array
* @return mixed Last element from the array
*/
function array_peek(array &$array)
{
$o = array_pop($array);
array_push($array, $o);
return $o;
}
/**
* Creates a tree structure from file content
*
* @param string $file File to parse
* @return TreeNode Root element of created tree
*/
function parseFileIntoTree($file)
{
$lines = file($file);
$root = new TreeNode();
// Stack of TreeNode instances
$stack = array();
array_push($stack, $root);
foreach ($lines as $line) {
$line = trim($line);
// Skip empty lines
if ($line == '') {
continue;
}
switch (substr($line, 0, 1)) {
case '{':
// Functionality is implemented in default case; ignore
break;
case '}':
// Pop stack
array_pop($stack);
break;
case '"':
// Add new entry to last section on stack
$node = array_peek($stack);
$vo = $node->getValue('data');
$parts = explode(' ', $line);
$parts[0] = substr($parts[0], 1, strlen($parts[0]) - 2);
$parts[1] = substr($parts[1], 1, strlen($parts[1]) - 2);
$vo->data[$parts[0]] = $parts[1];
break;
default:
// Initialize new section
$vo = new MyVO();
$vo->title = $line;
$node = new TreeNode();
$node->setValue('data', $vo);
// Add new section to tree structure
$parent = array_peek($stack);
$parent->addChild($node);
// Push new section on stack
array_push($stack, $node);
}
}
return $root;
}
/**
* Displays the content of a tree structure
*
* @param TreeNode $node Root element
* @param int $depth Recursion depth
*/
function showRec(TreeNode $node, $depth = 0)
{
foreach ($node->getChildren() as $child) {
$vo = $child->getValue('data');
echo str_repeat(' ', $depth) . $vo->title . "\n";
if ($vo->data != null) {
foreach ($vo->data as $key => $value) {
echo str_repeat(' ', $depth) . ' ' . $key . ' => ' . $value . "\n";
}
}
showRec($child, $depth + 1);
}
}
$root = parseFileIntoTree('input.txt');
echo '<pre>';
showRec($root);
echo '</pre>';Example input:
Text1
{
Colours
{
"1" "red"
"2" "yellow"
"3" "green"
}
Animals
{
"6" "Cat"
"3" "Dog"
}
}Output:
Text1
Colours
1 => red
2 => yellow
3 => green
Animals
6 => Cat
3 => Dog