<?php
if (!defined('ABSPATH')) exit;

/**
 * Adds semantic presentation wrappers around existing HTML without rewriting
 * the approved page content. Every original byte remains inside the wrappers.
 */
class AIWEST_Semantic_Layout_Composer {
    const VERSION = '1';

    public static function compose($content, $profile = 'editorial') {
        $content = self::decompose((string) $content);
        if (trim($content) === '') return $content;

        $parts = self::section_parts($content);
        if (!is_array($parts) || count($parts) < 2) {
            $role = preg_match('/<h2\b/i', $content) ? self::classify($content, 0, $profile) : 'content';
            $body = in_array($role, ['cards', 'steps', 'faq', 'comparison'], true) ? self::componentize_h3_groups($content, $role) : $content;
            return self::wrap_section($body, $role, 0);
        }

        $output = '';
        $section_index = 0;
        foreach ($parts as $part) {
            if ($part === '') continue;
            $has_h2 = preg_match('/^\s*(?:<!--.*?-->\s*)*<h2\b/is', $part) === 1;
            if (!$has_h2) {
                $output .= self::wrap_section($part, 'intro', $section_index++);
                continue;
            }

            $role = self::classify($part, $section_index, $profile);
            $body = in_array($role, ['cards', 'steps', 'faq', 'comparison'], true)
                ? self::componentize_h3_groups($part, $role)
                : $part;
            $output .= self::wrap_section($body, $role, $section_index++);
        }
        return $output;
    }

    public static function decompose($content) {
        $content = (string) $content;
        if (strpos($content, 'data-aiwest-layout-section') === false && strpos($content, 'data-aiwest-layout-grid') === false) {
            return $content;
        }

        $patterns = [
            '/<!--\s*aiwest-layout-section:start.*?-->\s*<section\b[^>]*\bdata-aiwest-layout-section\s*=\s*(["\'])1\1[^>]*>/is',
            '/<\/section>\s*<!--\s*aiwest-layout-section:end\s*-->/i',
            '/<!--\s*aiwest-layout-grid:start\s*-->\s*<div\b[^>]*\bdata-aiwest-layout-grid\s*=\s*(["\'])1\1[^>]*>/i',
            '/<\/div>\s*<!--\s*aiwest-layout-grid:end\s*-->/i',
            '/<!--\s*aiwest-layout-item:start\s*-->\s*<article\b[^>]*\bdata-aiwest-layout-item\s*=\s*(["\'])1\1[^>]*>/i',
            '/<\/article>\s*<!--\s*aiwest-layout-item:end\s*-->/i',
        ];
        return preg_replace($patterns, '', $content);
    }

    public static function inventory($content) {
        $content = self::decompose((string) $content);
        preg_match_all('/<h([1-6])\b[^>]*>(.*?)<\/h\1>/is', $content, $headings, PREG_SET_ORDER);
        preg_match_all('/<a\b[^>]*\bhref\s*=\s*(["\'])(.*?)\1/is', $content, $links, PREG_SET_ORDER);
        $heading_list = [];
        foreach ($headings as $heading) {
            $heading_list[] = strtolower($heading[1] . ':' . trim(wp_strip_all_tags($heading[2])));
        }
        $link_list = [];
        foreach ($links as $link) $link_list[] = html_entity_decode(trim($link[2]), ENT_QUOTES, 'UTF-8');

        return [
            'text_hash' => hash('sha256', self::visible_text($content)),
            'headings_hash' => hash('sha256', wp_json_encode($heading_list)),
            'links_hash' => hash('sha256', wp_json_encode($link_list)),
            'headings' => count($heading_list),
            'links' => count($link_list),
            'lists' => preg_match_all('/<(?:ul|ol)\b/i', $content),
            'tables' => preg_match_all('/<table\b/i', $content),
            'images' => preg_match_all('/<img\b/i', $content),
        ];
    }

    public static function identity_preserved($before, $after) {
        return self::inventory($before) === self::inventory($after);
    }

    protected static function wrap_section($html, $role, $index) {
        $role = sanitize_key($role) ?: 'content';
        $classes = 'aiwest-layout-section aiwest-layout-role-' . $role;
        return '<!-- aiwest-layout-section:start ' . esc_html($role) . ' -->'
            . '<section class="' . esc_attr($classes) . '" data-aiwest-layout-section="1" data-aiwest-layout-role="' . esc_attr($role) . '" data-aiwest-layout-index="' . intval($index) . '">'
            . $html . '</section><!-- aiwest-layout-section:end -->';
    }

    /** Keep a Gutenberg heading block comment attached to the H2 it opens. */
    protected static function section_parts($content) {
        $offsets = self::heading_offsets($content, 2);
        if (!$offsets) return [$content];
        $parts = [];
        $cursor = 0;
        foreach ($offsets as $offset) {
            if ($offset > $cursor) $parts[] = substr($content, $cursor, $offset - $cursor);
            $cursor = $offset;
        }
        if ($cursor < strlen($content)) $parts[] = substr($content, $cursor);
        return array_values(array_filter($parts, static function ($part) { return $part !== ''; }));
    }

    protected static function componentize_h3_groups($html, $role) {
        $offsets = self::heading_offsets($html, 3);
        if (count($offsets) < 2) return $html;
        $offset = $offsets[0];
        $prefix = substr($html, 0, $offset);
        $items = [];
        foreach ($offsets as $index => $item_offset) {
            $end = $offsets[$index + 1] ?? strlen($html);
            $items[] = substr($html, $item_offset, $end - $item_offset);
        }

        $grid = '<!-- aiwest-layout-grid:start -->'
            . '<div class="aiwest-layout-grid aiwest-layout-grid-' . esc_attr($role) . '" data-aiwest-layout-grid="1">';
        foreach ($items as $item) {
            $grid .= '<!-- aiwest-layout-item:start -->'
                . '<article class="aiwest-layout-item" data-aiwest-layout-item="1">'
                . $item . '</article><!-- aiwest-layout-item:end -->';
        }
        return $prefix . $grid . '</div><!-- aiwest-layout-grid:end -->';
    }

    protected static function heading_offsets($content, $level) {
        preg_match_all('/<h' . intval($level) . '\b[^>]*>/i', $content, $matches, PREG_OFFSET_CAPTURE);
        $offsets = [];
        foreach ($matches[0] ?? [] as $heading) {
            $offset = intval($heading[1]);
            $prefix = substr($content, 0, $offset);
            if (preg_match('/<!--\s*wp:heading\b(?:(?!-->).)*-->\s*$/is', $prefix, $comment, PREG_OFFSET_CAPTURE)) $offset = intval($comment[0][1]);
            $offsets[$offset] = true;
        }
        $offsets = array_keys($offsets);
        sort($offsets, SORT_NUMERIC);
        return $offsets;
    }

    protected static function classify($html, $index, $profile) {
        preg_match('/<h2\b[^>]*>(.*?)<\/h2>/is', $html, $heading_match);
        $heading = self::lower(trim(wp_strip_all_tags($heading_match[1] ?? '')));
        $h3_count = preg_match_all('/<h3\b/i', $html);
        $numbered_h3 = preg_match_all('/<h3\b[^>]*>\s*(?:<[^>]+>\s*)*[0-9]+[\.)\-:]/i', $html);

        if (preg_match('/\b(faq|frequently asked|questions and answers|common questions)\b/u', $heading)) return 'faq';
        if (preg_match('/\b(request|contact|start now|get started|download|subscribe|early access|donate|join)\b/u', $heading)) return 'cta';
        if (preg_match('/\b(related|resources|explore|further reading|see also)\b/u', $heading)) return 'related';
        if (preg_match('/\b(vs\.?|versus|comparison|compare|differences?)\b/u', $heading) || preg_match('/<table\b/i', $html)) return 'comparison';
        if ($numbered_h3 >= 2 || preg_match('/\b(how .* works?|steps?|process|workflow|getting started)\b/u', $heading)) return 'steps';
        if ($h3_count >= 2) return 'cards';
        if ($index === 0 && $profile === 'landing') return 'hero';
        return ($index % 2 === 0) ? 'content' : 'soft';
    }

    protected static function visible_text($html) {
        $text = html_entity_decode(wp_strip_all_tags((string) $html, true), ENT_QUOTES, 'UTF-8');
        $text = preg_replace('/\s+/u', ' ', trim($text));
        return $text;
    }

    protected static function lower($text) {
        return function_exists('mb_strtolower') ? mb_strtolower((string) $text, 'UTF-8') : strtolower((string) $text);
    }
}