<?php
if (!defined('ABSPATH')) exit;

class AdPageX_Inserter
{
    private static $instance = null;
    private $config = [];
    private $styles_enqueued = false;

    public static function get_instance()
    {
        if (self::$instance === null) {
            self::$instance = new self();
        }
        return self::$instance;
    }

    private function __construct()
    {
        add_action('wp_enqueue_scripts', [$this, 'enqueue_assets']);
    }

    /**
     * Set config từ placement config
     */
    public function set_config($placement_config)
    {
        $this->config = wp_parse_args($placement_config, [
            'position' => 2,
            'location' => 'after_paragraph',
            'alignment' => 'default',
            'readmore_text' => __('Read More', 'adpagex'),
            'target_element' => '',
            'show_readmore' => 'no'
        ]);
    }

    /**
     * Process content - hỗ trợ tất cả vị trí với hoặc không có readmore
     */
    public function process_content($content, $ad_html = '', $placement_config = [])
    {
        if (!empty($placement_config)) {
            $this->set_config($placement_config);
        }

        // Kiểm tra có bật readmore không
        $use_readmore = !empty($this->config['show_readmore']) && $this->config['show_readmore'] === 'yes';
        
        $location = $this->config['location'] ?? 'after_paragraph';


        switch ($location) {
            case 'after_content':
                return $use_readmore ? $this->insert_after_content_with_readmore($content, $ad_html) 
                                    : $this->insert_after_content_simple($content, $ad_html);

            case 'before_content':
                return $use_readmore ? $this->insert_before_content_with_readmore($content, $ad_html)
                                    : $this->insert_before_content_simple($content, $ad_html);

            case 'after_paragraph':
            case 'before_paragraph':
                return $use_readmore ? $this->insert_at_paragraph_with_readmore($content, $ad_html)
                                    : $this->insert_at_paragraph_simple($content, $ad_html);

            case 'after_image':
            case 'before_image':
                return $use_readmore ? $this->insert_at_image_with_readmore($content, $ad_html)
                                    : $this->insert_at_image_simple($content, $ad_html);

            case 'after_heading':
            case 'before_heading':
                return $use_readmore ? $this->insert_at_heading_with_readmore($content, $ad_html)
                                    : $this->insert_at_heading_simple($content, $ad_html);

            case 'custom_element':
                return $use_readmore ? $this->insert_at_custom_element_with_readmore($content, $ad_html)
                                    : $this->insert_at_custom_element_simple($content, $ad_html);

            default:
                return $use_readmore ? $this->insert_at_paragraph_with_readmore($content, $ad_html)
                                    : $this->insert_at_paragraph_simple($content, $ad_html);
        }
    }

    // =========================
    // SIMPLE INSERTIONS (NO READMORE)
    // =========================

    private function insert_after_content_simple($content, $ad_html)
    {
        return $content . $ad_html;
    }

    private function insert_before_content_simple($content, $ad_html)
    {
        return $ad_html . $content;
    }

    private function insert_at_paragraph_simple($content, $ad_html)
    {
        $paragraph = max(1, (int)$this->config['position']);
        $location = $this->config['location'];

        if ($location === 'before_paragraph') {
            return $this->insert_before_paragraph_simple($content, $ad_html, $paragraph);
        } else {
            return $this->insert_after_paragraph_simple($content, $ad_html, $paragraph);
        }
    }

    private function insert_after_paragraph_simple($content, $ad_html, $paragraph_number)
    {
        $closingTag = '</p>';
        $offset = 0;
        $paragraphs_found = 0;

        while (($pos = stripos($content, $closingTag, $offset)) !== false) {
            $paragraphs_found++;
            if ($paragraphs_found == $paragraph_number) {
                return substr($content, 0, $pos + strlen($closingTag)) . $ad_html . substr($content, $pos + strlen($closingTag));
            }
            $offset = $pos + strlen($closingTag);
        }

        return $content . $ad_html;
    }

    private function insert_before_paragraph_simple($content, $ad_html, $paragraph_number)
    {
        $pattern = '/<p(?:[^>]*)>/i';
        preg_match_all($pattern, $content, $matches, PREG_OFFSET_CAPTURE);

        if (count($matches[0]) >= $paragraph_number) {
            $target_paragraph = $matches[0][$paragraph_number - 1];
            $insert_pos = $target_paragraph[1];
            return substr($content, 0, $insert_pos) . $ad_html . substr($content, $insert_pos);
        }

        return $content . $ad_html;
    }

    private function insert_at_image_simple($content, $ad_html)
    {
        $image_number = max(1, (int)$this->config['position']);
        $location = $this->config['location'];

        $pattern = '/<img[^>]+>/i';
        preg_match_all($pattern, $content, $matches, PREG_OFFSET_CAPTURE);

        if (count($matches[0]) < $image_number) {
            return $content . $ad_html;
        }

        $target_image = $matches[0][$image_number - 1];
        $img_offset = $target_image[1];
        $img_length = strlen($target_image[0]);

        if ($location === 'before_image') {
            $insert_pos = $img_offset;
        } else {
            $insert_pos = $img_offset + $img_length;
        }

        return substr($content, 0, $insert_pos) . $ad_html . substr($content, $insert_pos);
    }

    private function insert_at_heading_simple($content, $ad_html)
    {
        $heading_number = max(1, (int)$this->config['position']);
        $location = $this->config['location'];

        $pattern = '/<h[1-6][^>]*>.*?<\/h[1-6]>/is';
        preg_match_all($pattern, $content, $matches, PREG_OFFSET_CAPTURE);

        if (count($matches[0]) < $heading_number) {
            return $content . $ad_html;
        }

        $target_heading = $matches[0][$heading_number - 1];
        $heading_offset = $target_heading[1];
        $heading_length = strlen($target_heading[0]);

        if ($location === 'before_heading') {
            $insert_pos = $heading_offset;
        } else {
            $insert_pos = $heading_offset + $heading_length;
        }

        return substr($content, 0, $insert_pos) . $ad_html . substr($content, $insert_pos);
    }

    private function insert_at_custom_element_simple($content, $ad_html)
    {
        $target_element = $this->config['target_element'] ?? '';
        $position = max(1, (int)$this->config['position']);

        if (empty($target_element)) {
            return $content . $ad_html;
        }

        $pattern = $this->build_element_pattern($target_element);
        if (!$pattern) {
            return $content . $ad_html;
        }

        preg_match_all($pattern, $content, $matches, PREG_OFFSET_CAPTURE);

        if (count($matches[0]) < $position) {
            return $content . $ad_html;
        }

        $target = $matches[0][$position - 1];
        $element_offset = $target[1];
        $element_length = strlen($target[0]);

        $insert_pos = $element_offset + $element_length;

        return substr($content, 0, $insert_pos) . $ad_html . substr($content, $insert_pos);
    }

    // =========================
    // READMORE INSERTIONS
    // =========================

    private function insert_after_content_with_readmore($content, $ad_html)
    {
        $readmore_id = 'adpagex-readmore-' . uniqid();
        $readmore_button = $this->build_readmore_button($readmore_id);

        $position = max(1, (int)$this->config['position']);
        $content_parts = $this->split_content_by_percentage($content, $position);

        return $content_parts['before'] .
            $ad_html .
            $readmore_button .
            '<div id="' . esc_attr($readmore_id) . '" style="display:none;">' .
            $content_parts['after'] .
            '</div>';
    }

    private function insert_before_content_with_readmore($content, $ad_html)
    {
        $readmore_id = 'adpagex-readmore-' . uniqid();
        $readmore_button = $this->build_readmore_button($readmore_id);

        return $ad_html .
            $readmore_button .
            '<div id="' . esc_attr($readmore_id) . '" style="display:none;">' .
            $content .
            '</div>';
    }

    private function insert_at_paragraph_with_readmore($content, $ad_html)
    {
        $paragraph = max(1, (int)$this->config['position']);
        $location = $this->config['location'];
        $readmore_id = 'adpagex-readmore-' . uniqid();

        if (extension_loaded('dom')) {
            return $this->process_paragraph_with_dom($content, $ad_html, $paragraph, $location, $readmore_id);
        }

        return $this->process_paragraph_with_regex($content, $ad_html, $paragraph, $location, $readmore_id);
    }

    private function insert_at_image_with_readmore($content, $ad_html)
    {
        $image_number = max(1, (int)$this->config['position']);
        $location = $this->config['location'];
        $readmore_id = 'adpagex-readmore-' . uniqid();

        $pattern = '/<img[^>]+>/i';
        preg_match_all($pattern, $content, $matches, PREG_OFFSET_CAPTURE);

        if (count($matches[0]) < $image_number) {
            if (count($matches[0]) === 0) {
                return $this->insert_after_content_with_readmore($content, $ad_html);
            }
            $image_number = count($matches[0]);
        }

        $target_image = $matches[0][$image_number - 1];
        $img_offset = $target_image[1];
        $img_length = strlen($target_image[0]);

        $readmore_button = $this->build_readmore_button($readmore_id);

        if ($location === 'before_image') {
            $insert_pos = $img_offset;
            $remaining_content = substr($content, $insert_pos);
        } else {
            $insert_pos = $img_offset + $img_length;
            $remaining_content = substr($content, $insert_pos);
        }

        return substr($content, 0, $insert_pos) .
            $ad_html .
            $readmore_button .
            '<div id="' . esc_attr($readmore_id) . '" style="display:none;">' .
            $remaining_content .
            '</div>';
    }

    private function insert_at_heading_with_readmore($content, $ad_html)
    {
        $heading_number = max(1, (int)$this->config['position']);
        $location = $this->config['location'];
        $readmore_id = 'adpagex-readmore-' . uniqid();

        $pattern = '/<h[1-6][^>]*>.*?<\/h[1-6]>/is';
        preg_match_all($pattern, $content, $matches, PREG_OFFSET_CAPTURE);

        if (count($matches[0]) < $heading_number) {
            if (count($matches[0]) === 0) {
                return $this->insert_after_content_with_readmore($content, $ad_html);
            }
            $heading_number = count($matches[0]);
        }

        $target_heading = $matches[0][$heading_number - 1];
        $heading_offset = $target_heading[1];
        $heading_length = strlen($target_heading[0]);

        $readmore_button = $this->build_readmore_button($readmore_id);

        if ($location === 'before_heading') {
            $insert_pos = $heading_offset;
            $remaining_content = substr($content, $insert_pos);
        } else {
            $insert_pos = $heading_offset + $heading_length;
            $remaining_content = substr($content, $insert_pos);
        }

        return substr($content, 0, $insert_pos) .
            $ad_html .
            $readmore_button .
            '<div id="' . esc_attr($readmore_id) . '" style="display:none;">' .
            $remaining_content .
            '</div>';
    }

    private function insert_at_custom_element_with_readmore($content, $ad_html)
    {
        $target_element = $this->config['target_element'] ?? '';
        $position = max(1, (int)$this->config['position']);
        $readmore_id = 'adpagex-readmore-' . uniqid();

        if (empty($target_element)) {
            return $this->insert_after_content_with_readmore($content, $ad_html);
        }

        $pattern = $this->build_element_pattern($target_element);
        if (!$pattern) {
            return $this->insert_after_content_with_readmore($content, $ad_html);
        }

        preg_match_all($pattern, $content, $matches, PREG_OFFSET_CAPTURE);

        if (count($matches[0]) < $position) {
            return $this->insert_after_content_with_readmore($content, $ad_html);
        }

        $target = $matches[0][$position - 1];
        $element_offset = $target[1];
        $element_length = strlen($target[0]);

        $readmore_button = $this->build_readmore_button($readmore_id);
        $insert_pos = $element_offset + $element_length;
        $remaining_content = substr($content, $insert_pos);

        return substr($content, 0, $insert_pos) .
            $ad_html .
            $readmore_button .
            '<div id="' . esc_attr($readmore_id) . '" style="display:none;">' .
            $remaining_content .
            '</div>';
    }

    // =========================
    // DOM & REGEX PROCESSING
    // =========================

    private function process_paragraph_with_dom($content, $ad_html, $paragraph, $location, $readmore_id)
    {
        libxml_use_internal_errors(true);
        $dom = new \DOMDocument('1.0', 'UTF-8');

        $wrapped = mb_convert_encoding(
            '<!DOCTYPE html><html><head><meta charset="utf-8"></head><body>' . $content . '</body></html>',
            'HTML-ENTITIES',
            'UTF-8'
        );

        @$dom->loadHTML($wrapped, LIBXML_HTML_NOIMPLIED | LIBXML_HTML_NODEFDTD);
        libxml_clear_errors();

        $body = $dom->getElementsByTagName('body')->item(0);
        if (!$body) {
            return $content . $ad_html;
        }

        $xpath = new \DOMXPath($dom);
        // Exclude <p> nested inside blockquote/figure/li (same as Ad Inserter defaults)
        $paragraphs = $xpath->query('//p[normalize-space() != "" and not(ancestor::blockquote) and not(ancestor::figure) and not(ancestor::li)]');

        if ($paragraphs->length < $paragraph) {
            if ($paragraphs->length === 0) {
                return $this->insert_after_content_with_readmore($content, $ad_html);
            }
            $paragraph = $paragraphs->length;
        }

        $target_paragraph = $paragraphs->item($paragraph - 1);
        if (!$target_paragraph) {
            return $this->insert_after_content_with_readmore($content, $ad_html);
        }

        $readmore_button = $this->build_readmore_button($readmore_id);

        // Parse ad HTML as real HTML (not XML) — appendXML fails silently on <script async>, & in URLs, etc.
        $temp_dom = new \DOMDocument('1.0', 'UTF-8');
        @$temp_dom->loadHTML(
            mb_convert_encoding(
                '<!DOCTYPE html><html><head><meta charset="utf-8"></head><body>' . $ad_html . $readmore_button . '</body></html>',
                'HTML-ENTITIES',
                'UTF-8'
            ),
            LIBXML_HTML_NOIMPLIED | LIBXML_HTML_NODEFDTD
        );
        $temp_body = $temp_dom->getElementsByTagName('body')->item(0);

        $ad_nodes = [];
        if ($temp_body) {
            foreach ($temp_body->childNodes as $child) {
                $ad_nodes[] = $dom->importNode($child, true);
            }
        }

        $hidden_div = $dom->createElement('div');
        $hidden_div->setAttribute('id', $readmore_id);
        $hidden_div->setAttribute('style', 'display:none;');

        if ($location === 'before_paragraph') {
            foreach ($ad_nodes as $node) {
                $target_paragraph->parentNode->insertBefore($node, $target_paragraph);
            }
            $target_paragraph->parentNode->insertBefore($hidden_div, $target_paragraph);

            $current = $target_paragraph;
            while ($current) {
                $next = $current->nextSibling;
                $hidden_div->appendChild($current);
                $current = $next;
            }
        } else {
            $next_sibling = $target_paragraph->nextSibling;
            if ($next_sibling) {
                foreach ($ad_nodes as $node) {
                    $target_paragraph->parentNode->insertBefore($node, $next_sibling);
                }
                $target_paragraph->parentNode->insertBefore($hidden_div, $next_sibling);
            } else {
                foreach ($ad_nodes as $node) {
                    $target_paragraph->parentNode->appendChild($node);
                }
                $target_paragraph->parentNode->appendChild($hidden_div);
            }

            $current = $next_sibling;
            while ($current) {
                $next = $current->nextSibling;
                $hidden_div->appendChild($current);
                $current = $next;
            }
        }

        $new_content = '';
        foreach ($body->childNodes as $child) {
            $new_content .= $dom->saveHTML($child);
        }

        return $new_content;
    }

    private function process_paragraph_with_regex($content, $ad_html, $paragraph, $location, $readmore_id)
    {
        $pattern = '/<p(?:[^>]*)>(?:(?!<\/p>).)*<\/p>/is';
        preg_match_all($pattern, $content, $matches, PREG_OFFSET_CAPTURE);

        $valid_paragraphs = [];
        foreach ($matches[0] as $match) {
            $p_content = $match[0];
            $stripped = trim(wp_strip_all_tags($p_content));
            $has_media = (stripos($p_content, '<img') !== false) ||
                (stripos($p_content, '<iframe') !== false) ||
                (stripos($p_content, '<video') !== false);

            if (!empty($stripped) || $has_media) {
                $valid_paragraphs[] = $match;
            }
        }

        if (count($valid_paragraphs) < $paragraph) {
            if (count($valid_paragraphs) === 0) {
                return $this->insert_after_content_with_readmore($content, $ad_html);
            }
            $paragraph = count($valid_paragraphs);
        }

        $target_paragraph = $valid_paragraphs[$paragraph - 1];
        $target_offset = $target_paragraph[1];
        $target_length = strlen($target_paragraph[0]);

        $readmore_button = $this->build_readmore_button($readmore_id);
        $insertion_html = $ad_html . $readmore_button;
        $hidden_start = '<div id="' . esc_attr($readmore_id) . '" style="display:none;">';
        $hidden_end = '</div>';

        if ($location === 'before_paragraph') {
            $before_target = substr($content, 0, $target_offset);
            $from_target = substr($content, $target_offset);

            return $before_target . $insertion_html . $hidden_start . $from_target . $hidden_end;
        } else {
            $before_target = substr($content, 0, $target_offset + $target_length);
            $after_target = substr($content, $target_offset + $target_length);

            return $before_target . $insertion_html . $hidden_start . $after_target . $hidden_end;
        }
    }

    // =========================
    // UTILITY FUNCTIONS
    // =========================

    private function build_readmore_button($readmore_id)
    {
        $readmore_text = $this->config['readmore_text'] ?? __('Read More', 'adpagex');

        return '<div class="adpagex-custom-read-more-container" style="clear:both; margin: 20px 0; text-align: center;">' .
            '<span id="' . esc_attr($readmore_id) . '-btn" ' .
            'class="adpagex-custom-read-more-button" ' .
            'data-target-id="' . esc_attr($readmore_id) . '" ' .
            'style="cursor:pointer; display: inline-block; padding: 12px 24px; background: #0073aa; color: white; border-radius: 5px; text-decoration: none; font-weight: bold;">' .
            wp_kses_post($readmore_text) .
            '</span></div>';
    }

    private function split_content_by_percentage($content, $percentage)
    {
        $percentage = min(100, max(0, $percentage));
        $content_length = mb_strlen($content, 'UTF-8');
        $split_point = intval(($content_length * $percentage) / 100);
        
        return [
            'before' => mb_substr($content, 0, $split_point, 'UTF-8'),
            'after' => mb_substr($content, $split_point, null, 'UTF-8')
        ];
    }

    private function build_element_pattern($target_element)
    {
        $patterns = [
            'div' => '/<div[^>]*>.*?<\/div>/is',
            'span' => '/<span[^>]*>.*?<\/span>/is',
            'blockquote' => '/<blockquote[^>]*>.*?<\/blockquote>/is',
            'ul' => '/<ul[^>]*>.*?<\/ul>/is',
            'ol' => '/<ol[^>]*>.*?<\/ol>/is',
            'table' => '/<table[^>]*>.*?<\/table>/is',
        ];
        
        return $patterns[$target_element] ?? null;
    }

    public function enqueue_assets()
    {
        if ($this->styles_enqueued) {
            return;
        }

        $css = '
        .adpagex-custom-read-more-container {
            text-align: center;
            margin: 20px 0;
            clear: both;
            width: 100%;
        }
        .adpagex-custom-read-more-button {
            display: inline-block;
            min-width: 120px;
            max-width: 280px;
            padding: 12px 24px;
            font-size: 14px;
            font-weight: bold;
            text-transform: uppercase;
            letter-spacing: 0.5px;
            text-align: center;
            background-color: #0073aa;
            color: white !important;
            text-decoration: none;
            border-radius: 5px;
            border: none;
            transition: all 0.3s ease;
            cursor: pointer;
            box-shadow: 0 2px 4px rgba(0,0,0,0.1);
        }
        .adpagex-custom-read-more-button:hover {
            background-color: #005177;
            transform: translateY(-1px);
            box-shadow: 0 4px 8px rgba(0,0,0,0.15);
        }
        .adpagex-custom-read-more-button:active {
            transform: translateY(0);
            box-shadow: 0 2px 4px rgba(0,0,0,0.1);
        }';

        wp_register_style('adpagex-readmore-style', false, [], ADPAGEX_VERSION);
        wp_enqueue_style('adpagex-readmore-style');
        wp_add_inline_style('adpagex-readmore-style', $css);

        $js = '
        document.addEventListener("DOMContentLoaded", function() {
            document.addEventListener("click", function(e) {
                var btn = e.target.closest(".adpagex-custom-read-more-button");
                if (btn) {
                    e.preventDefault();
                    var targetId = btn.getAttribute("data-target-id");
                    var hiddenDiv = document.getElementById(targetId);
                    if (hiddenDiv) {
                        hiddenDiv.style.display = hiddenDiv.style.display === "none" ? "block" : "none";
                    }
                }
            });
        });';

        wp_register_script('adpagex-readmore-script', false, [], ADPAGEX_VERSION, true);
        wp_enqueue_script('adpagex-readmore-script');
        wp_add_inline_script('adpagex-readmore-script', $js);

        $this->styles_enqueued = true;
    }
}