<?php

namespace App\Services;

class AccessibilityAnalyzer
{
    /**
     * Analyze block-based content for common accessibility issues.
     * This method scans for missing alt text, incorrect heading hierarchy, and other WCAG-related gaps.
     *
     * @param array $content The JSON-encoded block content from the editor.
     * @return array A list of identified issues with severity and messages.
     */
    public function analyze(array $content): array
    {
        // Handle multi-locale content
        $isMultiLocale = false;
        $locales = array_keys($content);
        foreach ($locales as $locale) {
            if (is_string($locale) && is_array($content[$locale]) && isset($content[$locale][0]['type'])) {
                $isMultiLocale = true;
                break;
            }
        }

        if ($isMultiLocale) {
            $allIssues = [];
            foreach ($content as $locale => $localeContent) {
                if (is_array($localeContent)) {
                    $localeIssues = $this->analyzeBlocks($localeContent);
                    if (!empty($localeIssues)) {
                        $allIssues[$locale] = $localeIssues;
                    }
                }
            }
            return $allIssues;
        }

        return $this->analyzeBlocks($content);
    }

    /**
     * Internal helper to analyze a flat list of blocks.
     *
     * @param array $content
     * @return array
     */
    protected function analyzeBlocks(array $content): array
    {
        $issues = [];
        $headings = [];

        foreach ($content as $index => $block) {
            $type = $block['type'] ?? '';
            $data = $block['data'] ?? [];

            switch ($type) {
                case 'heading':
                    $level = (int) ($data['level'] ?? 0);
                    if ($level > 0) {
                        $headings[] = [
                            'level' => $level,
                            'index' => $index
                        ];
                    }
                    break;

                case 'image':
                    $alt = $data['alt'] ?? '';
                    if (empty($alt)) {
                        $issues[] = [
                            'severity' => 'error',
                            'message' => 'Image block is missing alternative text (alt tag).',
                            'block_index' => $index,
                        ];
                    }
                    break;

                case 'media':
                    $alt = $data['alt'] ?? '';
                    if (empty($alt)) {
                        $issues[] = [
                            'severity' => 'warning',
                            'message' => 'Media block may be missing alternative text.',
                            'block_index' => $index,
                        ];
                    }
                    break;
            }
        }

        if (!empty($headings)) {
            $prevLevel = 0;
            foreach ($headings as $h) {
                $level = $h['level'];
                if ($prevLevel > 0 && $level > $prevLevel + 1) {
                    $issues[] = [
                        'severity' => 'warning',
                        'message' => "Skipped heading level from H$prevLevel to H$level. Headings should be sequential.",
                        'block_index' => $h['index'],
                    ];
                }
                $prevLevel = $level;
            }
        }

        return $issues;
    }
}