<?php
namespace PHPHtmlParser;

use PHPHtmlParser\Dom\AbstractNode;
use PHPHtmlParser\Dom\Collection;
use PHPHtmlParser\Dom\InnerNode;
use PHPHtmlParser\Dom\LeafNode;
use PHPHtmlParser\Exceptions\ChildNotFoundException;

/**
 * Class Selector
 *
 * @package PHPHtmlParser
 */
class Selector
{

    /**
     * Pattern of CSS selectors, modified from 'mootools'
     *
     * @var string
     */
    protected $pattern = "/([\w-:\*>]*)(?:\#([\w-]+)|\.([\w-]+))?(?:\[@?(!?[\w-:]+)(?:([!*^$]?=)[\"']?(.*?)[\"']?)?\])?([\/, ]+)/is";

    protected $selectors = array();

    /**
     * Constructs with the selector string
     *
     * @param string $selector
     */
    public function __construct($selector)
    {
        $this->parseSelectorString($selector);
    }

    /**
     * Returns the selectors that where found in __construct
     *
     * @return array
     */
    public function getSelectors()
    {
        return $this->selectors;
    }

    /**
     * Attempts to find the selectors starting from the given
     * node object.
     *
     * @param AbstractNode $node
     * @return Collection
     */
    public function find(AbstractNode $node)
    {
        $results = new Collection;
        foreach ($this->selectors as $selector) {
            $nodes = array($node);
            if (count($selector) == 0) {
                continue;
            }

            $options = array();
            foreach ($selector as $rule) {
                if ($rule['alterNext']) {
                    $options[] = $this->alterNext($rule);
                    continue;
                }
                $nodes = $this->seek($nodes, $rule, $options);
                // clear the options
                $options = array();
            }

            // this is the final set of nodes
            foreach ($nodes as $result) {
                $results[] = $result;
            }
        }

        return $results;
    }

    /**
     * Parses the selector string
     *
     * @param string $selector
     */
    protected function parseSelectorString($selector)
    {
        $matches = array();
        preg_match_all($this->pattern, trim($selector).' ', $matches, PREG_SET_ORDER);

        // skip tbody
        $result = array();
        foreach ($matches as $match) {
            // default values
            $tag       = strtolower(trim($match[1]));
            $operator  = '=';
            $key       = null;
            $value     = null;
            $noKey     = false;
            $alterNext = false;

            // check for elements that alter the behavior of the next element
            if ($tag == '>') {
                $alterNext = true;
            }

            // check for id selector
            if ( ! empty($match[2])) {
                $key   = 'id';
                $value = $match[2];
            }

            // check for class selector
            if ( ! empty($match[3])) {
                $key   = 'class';
                $value = $match[3];
            }

            // and final attribute selector
            if ( ! empty($match[4])) {
                $key = strtolower($match[4]);
            }
            if ( ! empty($match[5])) {
                $operator = $match[5];
            }
            if ( ! empty($match[6])) {
                $value = $match[6];
            }

            // check for elements that do not have a specified attribute
            if (isset($key[0]) && $key[0] == '!') {
                $key   = substr($key, 1);
                $noKey = true;
            }

            $result[] = array(
                'tag'       => $tag,
                'key'       => $key,
                'value'     => $value,
                'operator'  => $operator,
                'noKey'     => $noKey,
                'alterNext' => $alterNext,
            );
            if (trim($match[7]) == ',') {
                $this->selectors[] = $result;
                $result            = array();
            }
        }

        // save last results
        if (count($result) > 0) {
            $this->selectors[] = $result;
        }
    }

    /**
     * Attempts to find all children that match the rule
     * given.
     *
     * @param array $nodes
     * @param array $rule
     * @param array $options
     * @return array
     * @recursive
     */
    protected function seek(array $nodes, array $rule, array $options)
    {
        // XPath index
        if (count($rule['tag']) > 0 &&
            count($rule['key']) > 0 &&
            is_numeric($rule['key'])
        ) {
            $count = 0;
            /** @var AbstractNode $node */
            foreach ($nodes as $node) {
                if ($rule['tag'] == '*' ||
                    $rule['tag'] == $node->getTag()->name()
                ) {
                    ++$count;
                    if ($count == $rule['key']) {
                        // found the node we wanted
                        return array($node);
                    }
                }
            }

            return array();
        }

        $options = $this->flattenOptions($options);

        $return = array();
        /** @var InnerNode $node */
        foreach ($nodes as $node) {
            // check if we are a leaf
            if ($node instanceof LeafNode ||
                ! $node->hasChildren()
            ) {
                continue;
            }

            $children = array();
            $child    = $node->firstChild();
            while ( ! is_null($child)) {
                // wild card, grab all
                if ($rule['tag'] == '*' && is_null($rule['key'])) {
                    $return[] = $child;
                    try {
                        $child = $node->nextChild($child->id());
                    } catch (ChildNotFoundException $e) {
                        // no more children
                        $child = null;
                    }
                    continue;
                }

                $pass = true;
                // check tag
                if ( ! empty($rule['tag']) && $rule['tag'] != $child->getTag()->name() &&
                    $rule['tag'] != '*'
                ) {
                    // child failed tag check
                    $pass = false;
                }

                // check key
                if ($pass && ! is_null($rule['key'])) {
                    if ($rule['noKey']) {
                        if ( ! is_null($child->getAttribute($rule['key']))) {
                            $pass = false;
                        }
                    } else {
                        if ($rule['key'] != 'plaintext' &&
                            is_null($child->getAttribute($rule['key']))
                        ) {
                            $pass = false;
                        }
                    }
                }

                // compare values
                if ($pass && ! is_null($rule['key']) &&
                    ! is_null($rule['value']) && $rule['value'] != '*'
                ) {
                    if ($rule['key'] == 'plaintext') {
                        // plaintext search
                        $nodeValue = $child->text();
                    } else {
                        // normal search
                        $nodeValue = $child->getAttribute($rule['key']);
                    }

                    $check = $this->match($rule['operator'], $rule['value'], $nodeValue);

                    // handle multiple classes
                    if ( ! $check && $rule['key'] == 'class') {
                        $childClasses = explode(' ', $child->getAttribute('class'));
                        foreach ($childClasses as $class) {
                            if ( ! empty($class)) {
                                $check = $this->match($rule['operator'], $rule['value'], $class);
                            }
                            if ($check) {
                                break;
                            }
                        }
                    }

                    if ( ! $check) {
                        $pass = false;
                    }
                }

                if ($pass) {
                    // it passed all checks
                    $return[] = $child;
                } else {
                    // this child failed to be matched
                    if ($child instanceof InnerNode &&
                        $child->hasChildren()
                    ) {
                        // we still want to check its children
                        $children[] = $child;
                    }
                }

                try {
                    // get next child
                    $child = $node->nextChild($child->id());
                } catch (ChildNotFoundException $e) {
                    // no more children
                    $child = null;
                }
            }

            if (( ! isset($options['checkGrandChildren']) ||
                    $options['checkGrandChildren'])
                && count($children) > 0
            ) {
                // we have children that failed but are not leaves.
                $matches = $this->seek($children, $rule, $options);
                foreach ($matches as $match) {
                    $return[] = $match;
                }
            }
        }

        return $return;
    }

    /**
     * Attempts to match the given arguments with the given operator.
     *
     * @param string $operator
     * @param string $pattern
     * @param string $value
     * @return bool
     */
    protected function match($operator, $pattern, $value)
    {
        $value   = strtolower($value);
        $pattern = strtolower($pattern);
        switch ($operator) {
            case '=':
                return $value === $pattern;
            case '!=':
                return $value !== $pattern;
            case '^=':
                return preg_match('/^'.preg_quote($pattern, '/').'/', $value);
            case '$=':
                return preg_match('/'.preg_quote($pattern, '/').'$/', $value);
            case '*=':
                if ($pattern[0] == '/') {
                    return preg_match($pattern, $value);
                }

                return preg_match("/".$pattern."/i", $value);
        }

        return false;
    }

    /**
     * Attempts to figure out what the alteration will be for
     * the next element.
     *
     * @param array $rule
     * @return array
     */
    protected function alterNext($rule)
    {
        $options = array();
        if ($rule['tag'] == '>') {
            $options['checkGrandChildren'] = false;
        }

        return $options;
    }

    /**
     * Flattens the option array.
     *
     * @param array $optionsArray
     * @return array
     */
    protected function flattenOptions(array $optionsArray)
    {
        $options = array();
        foreach ($optionsArray as $optionArray) {
            foreach ($optionArray as $key => $option) {
                $options[$key] = $option;
            }
        }

        return $options;
    }
}