<?php

namespace WPDaddy\Dom;

class Translator {
	const cssRegex =
		'/'
		.'(?P<star>\*)'
		.'|(:(?P<pseudo>[\w-]*))'
		.'|\(*(?P<pseudospecifier>["\']*[\w\h-]*["\']*)\)'
		.'|(?P<element>[\w-]*)'
		.'|(?P<child>\s*>\s*)'
		.'|(#(?P<id>[\w-]*))'
		.'|(\.(?P<class>[\w-]*))'
		.'|(?P<sibling>\s*\+\s*)'
		."|(\[(?P<attribute>[\w-]*)((?P<attribute_equals>[=~$]+)(?P<attribute_value>[^\]]+))*\])+"
		.'|(?P<descendant>\s+)'
		.'/';

	const EQUALS_EXACT                                 = "=";
	const EQUALS_CONTAINS_WORD                         = "~=";
	const EQUALS_ENDS_WITH                             = "$=";
	const EQUALS_CONTAINS                              = "*=";
	const EQUALS_STARTS_WITH_OR_STARTS_WITH_HYPHENATED = "|=";
	const EQUALS_STARTS_WITH                           = "^=";

	protected $cssSelector;
	protected $prefix;

	public function __construct($cssSelector, $prefix = ".//"){
		$this->cssSelector = $cssSelector;
		$this->prefix      = $prefix;
	}

	public function __toString(){
		return $this->asXPath();
	}

	public function asXPath(){
		return $this->convert($this->cssSelector);
	}

	protected function convert($css){
		$cssArray   = preg_split(
			'/(["\']).*?\1(*SKIP)(*F)|,/',
			$css
		);
		$xPathArray = [];

		foreach($cssArray as $input) {
			$output        = $this->convertSingleSelector(trim($input));
			$xPathArray [] = $output;
		}

		return implode(" | ", $xPathArray);
	}

	protected function convertSingleSelector($css){
		$thread = $this->preg_match_collated(self::cssRegex, $css);
		$thread = array_values($thread);

		$xpath    = [ $this->prefix ];
		$prevType = "";
		foreach($thread as $threadKey => $currentThreadItem) {
			$next = isset($thread[$threadKey+1])
				? $thread[$threadKey+1]
				: false;

			switch($currentThreadItem['type']) {
				case 'star':
				case 'element':
					$xpath [] = $currentThreadItem['content'];
					break;

				case 'pseudo':
					$specifier = '';
					if($next && $next['type'] == 'pseudospecifier') {
						$specifier = "{$next['content']}";
					}

					switch($currentThreadItem['content']) {
						case 'disabled':
						case 'checked':
						case 'selected':
							$xpath [] = "[@{$currentThreadItem['content']}]";
							break;

						case 'text':
							$xpath [] = '[@type="text"]';
							break;

						case 'contains':
							if(empty($specifier)) {
								continue 3;
							}

							$xpath [] = "[contains(text(),$specifier)]";
							break;

						case 'first-child':
							$prev         = count($xpath)-1;
							$xpath[$prev] = '*[1]/self::'.$xpath[$prev];
							break;

						case 'nth-child':
							if(empty($specifier)) {
								continue 3;
							}

							$prev     = count($xpath)-1;
							$previous = $xpath[$prev];

							if(substr($previous, -1, 1) === ']') {
								$xpath[$prev] = str_replace(']', " and position() = $specifier]", $xpath[$prev]);
							} else {
								$xpath [] = "[$specifier]";
							}
							break;
						case 'nth-of-type':
							if(empty($specifier)) {
								continue 3;
							}

							$prev     = count($xpath)-1;
							$previous = $xpath[$prev];

							if(substr($previous, -1, 1) === ']') {
								$xpath [] = "[$specifier]";
							} else {
								$xpath [] = "[$specifier]";
							}
							break;
					}
					break;

				case 'child':
					$xpath [] = '/';
					break;

				case 'id':
					$xpath [] = ($prevType != 'element' ? '*' : '')."[@id='{$currentThreadItem['content']}']";
					break;

				case 'class':
					// https://devhints.io/xpath#class-check
					$xpath [] = (($prevType != 'element' && $prevType != 'class') ? '*' : '')
					            ."[contains(concat(' ',normalize-space(@class),' '),' {$currentThreadItem['content']} ')]";
					break;

				case 'sibling':
					$xpath [] = "/following-sibling::*[1]/self::";
					break;

				case 'attribute':
					if(!$prevType) {
						$xpath [] = "*";
					}
					$value = $currentThreadItem["detail"];

					$detail      = $value ? $value : null;
					$value       = $detail[0];
					$detailType  = $value ? $value : null;
					$value       = $detail[1];
					$detailValue = $value ? $value : null;

					if(!$detailType
					   || $detailType["type"] !== "attribute_equals") {
						$xpath [] = "[@{$currentThreadItem['content']}]";
						continue 2;
					}

					$valueString = trim(
						$detailValue["content"],
						" '\""
					);

					$equalsType = $detailType["content"];
					switch($equalsType) {
						case self::EQUALS_EXACT:
							$xpath [] = "[@{$currentThreadItem['content']}=\"{$valueString}\"]";
							break;

						case self::EQUALS_CONTAINS:
							// TODO.
							break;

						case self::EQUALS_CONTAINS_WORD:
							$xpath [] = "["
							            ."contains("
							            ."concat(\" \",@{$currentThreadItem['content']},\" \"),"
							            ."concat(\" \",\"{$valueString}\",\" \")"
							            .")"
							            ."]";
							break;

						case self::EQUALS_STARTS_WITH_OR_STARTS_WITH_HYPHENATED:
							// TODO.
							break;

						case self::EQUALS_STARTS_WITH:
							// TODO.
							break;

						case self::EQUALS_ENDS_WITH:
							$xpath [] = "["
							            ."substring("
							            ."@{$currentThreadItem['content']},"
							            ."string-length(@{$currentThreadItem['content']}) - "
							            ."string-length(\"{$valueString}\") + 1)"
							            ."=\"{$valueString}\""
							            ."]";
							break;
					}
					break;

				case 'descendant':
					$xpath [] = '//';
					break;
			}

			$prevType = $currentThreadItem['type'];
		}

		return implode("", $xpath);
	}

	/**
	 * @param          $regex
	 * @param          $string
	 * @param callable $transform
	 *
	 * @return array
	 */
	protected function preg_match_collated(
		$regex,
		$string,
		$transform = null
	){
		preg_match_all(
			$regex,
			$string,
			$matches,
			PREG_PATTERN_ORDER
		);

		$set = [];
		foreach($matches[0] as $k => $v) {
			if(!empty($v)) {
				$set[$k] = null;
			}
		}

		foreach($matches as $k => $m) {
			if(is_numeric($k)) {
				continue;
			}

			foreach($m as $i => $match) {
				if($match === '') {
					continue;
				}

				$toSet = null;

				if($transform) {
					$toSet = $transform($k, $match);
				} else {
					$toSet = [ 'type' => $k, 'content' => $match ];
				}

				if(!isset($set[$i])) {
					$set [$i] = $toSet;
				} else {
					if(!isset($set[$i]["detail"])) {
						$set[$i]["detail"] = [];
					}

					$set[$i]["detail"] [] = $toSet;
				}
			}
		}

		return $set;
	}
}