<?php
/**
 * ==============================================================================
 * SAQEL ENTERPRISE (EDTECH 2.0) - DYNAMIC CURRICULUM SERVICE
 * ==============================================================================
 * 
 * ملف: CurriculumService.php
 * الهدف المعماري:
 * إدارة المنظومة الحية للمناهج والكتب الوزارية وشجرة الدروس (Zero Mock Data):
 * 1. مسح وتوليد الشجرة الهرمية للمناهج من ملفات (manifest.json) وملفات الماركداون الحية.
 * 2. البحث الدلالي اللحظي في عناوين الدروس ونتاجات التعلم والمفاهيم.
 * 3. قراءة وحفظ وتحديث نصوص الماركداون للدروس والمصادر والملخصات.
 * 4. الربط المرجعي بين شجرة المناهج وقاعدة بيانات الدورات والدروس والفيديوهات.
 */

namespace App\Services;

use App\Core\Database;

class CurriculumService
{
    /**
     * التحقق التوافقي التلقائي من بنية قاعدة البيانات للمناهج
     */
    public static function ensureSchema(): void
    {
        // No-op (schema managed via database_schema.sql)
    }

    /**
     * Runtime migration: add is_system_curriculum (and related columns) to `courses`
     * if they are missing. Safe to call multiple times — uses IF NOT EXISTS / IGNORE.
     */
    public static function ensureSystemCurriculumColumn(): void
    {
        static $ran = false;
        if ($ran) return;
        $ran = true;

        try {
            // Check whether the column exists to avoid noisy ALTER errors on every request
            $row = Database::selectOne(
                "SELECT COUNT(*) as cnt FROM information_schema.COLUMNS
                 WHERE TABLE_SCHEMA = DATABASE()
                   AND TABLE_NAME   = 'courses'
                   AND COLUMN_NAME  = 'is_system_curriculum'
                 LIMIT 1"
            );

            if (empty($row['cnt'])) {
                Database::query(
                    "ALTER TABLE `courses`
                     ADD COLUMN `is_system_curriculum` TINYINT(1) NOT NULL DEFAULT 0
                         COMMENT 'الدورة الرئيسية للمنهاج الوزاري'
                     AFTER `is_school_exclusive`"
                );
            }

            // Also ensure grade_level + stream columns exist (for student filtering)
            $gradeRow = Database::selectOne(
                "SELECT COUNT(*) as cnt FROM information_schema.COLUMNS
                 WHERE TABLE_SCHEMA = DATABASE()
                   AND TABLE_NAME   = 'courses'
                   AND COLUMN_NAME  = 'grade_level'
                 LIMIT 1"
            );
            if (empty($gradeRow['cnt'])) {
                Database::query(
                    "ALTER TABLE `courses`
                     ADD COLUMN `grade_level` VARCHAR(50) DEFAULT NULL
                         COMMENT 'المرحلة الدراسية مثل: tawjihi_2008'
                     AFTER `is_system_curriculum`,
                     ADD COLUMN `stream` ENUM('scientific','literary','vocational','general') DEFAULT NULL
                         COMMENT 'الفرع الدراسي'
                     AFTER `grade_level`"
                );
            }
        } catch (\Throwable $e) {
            error_log('[CurriculumService] ensureSystemCurriculumColumn error: ' . $e->getMessage());
        }
    }

    /**
     * Resolve or create the master system curriculum course.
     *
     * Returns a guaranteed valid `course_id` that satisfies the FK constraint on
     * `lessons.course_id → courses.id`. Called by CurriculumController when
     * uploading AI/ministry videos without an explicit teacher course.
     *
     * @return int Valid course_id
     * @throws \RuntimeException if no subjects or teachers exist and creation fails
     */
    public static function getOrCreateSystemCourse(): int
    {
        // Ensure the column exists before querying it (runtime migration)
        self::ensureSystemCurriculumColumn();

        // 1. Look for existing master system course
        $existing = Database::selectOne(
            "SELECT id FROM courses WHERE is_system_curriculum = 1 LIMIT 1"
        );
        if ($existing && !empty($existing['id'])) {
            return (int)$existing['id'];
        }

        // 2. Also try by canonical title in case migration was run after records existed
        $byTitle = Database::selectOne(
            "SELECT id FROM courses WHERE title LIKE '%منهاج وزارة التربية%' LIMIT 1"
        );
        if ($byTitle && !empty($byTitle['id'])) {
            // Stamp it so future lookups are fast
            Database::query(
                "UPDATE courses SET is_system_curriculum = 1 WHERE id = ?",
                [(int)$byTitle['id']]
            );
            return (int)$byTitle['id'];
        }

        // 3. Create a new master course — resolve required FK dependencies first
        // Resolve subject_id (use first available subject or create a placeholder)
        $subject = Database::selectOne("SELECT id FROM subjects LIMIT 1");
        if (!$subject) {
            $subjectId = Database::insert(
                "INSERT INTO subjects (name, description) VALUES ('المنهاج الوزاري الأردني', 'مقررات وزارة التربية والتعليم المعتمدة') ON DUPLICATE KEY UPDATE id = LAST_INSERT_ID(id)"
            );
        } else {
            $subjectId = (int)$subject['id'];
        }

        // Resolve teacher_id (use system teacher with id=1 or first available)
        $teacher = Database::selectOne("SELECT id FROM teachers WHERE id = 1 LIMIT 1");
        if (!$teacher) {
            $teacher = Database::selectOne("SELECT id FROM teachers LIMIT 1");
        }
        if (!$teacher) {
            $tUuid = sprintf('%04x%04x-%04x-%04x-%04x-%04x%04x%04x', mt_rand(0, 0xffff), mt_rand(0, 0xffff), mt_rand(0, 0xffff), mt_rand(0, 0x0fff) | 0x4000, mt_rand(0, 0x3fff) | 0x8000, mt_rand(0, 0xffff), mt_rand(0, 0xffff), mt_rand(0, 0xffff));
            $teacherId = Database::insert(
                "INSERT INTO teachers (uuid, full_name, specialization, is_school_exclusive, is_marketplace_public)
                 VALUES (?, 'منهاج الذكاء الاصطناعي والوزارة', 'المنهاج الوزاري المعتمد', 0, 1)",
                [$tUuid]
            );
        } else {
            $teacherId = (int)$teacher['id'];
        }

        // Generate stable UUID for the master course
        $uuid = sprintf('%04x%04x-%04x-%04x-%04x-%04x%04x%04x',
            mt_rand(0, 0xffff), mt_rand(0, 0xffff),
            mt_rand(0, 0xffff),
            mt_rand(0, 0x0fff) | 0x4000,
            mt_rand(0, 0x3fff) | 0x8000,
            mt_rand(0, 0xffff), mt_rand(0, 0xffff), mt_rand(0, 0xffff)
        );

        $courseId = Database::insert(
            "INSERT INTO courses
                (uuid, subject_id, teacher_id, title, description, semester,
                 price_jod, is_published, is_system_curriculum, grade_level, stream)
             VALUES
                (?, ?, ?, 'منهاج وزارة التربية والتعليم الأساسي',
                 'الدورة الرئيسية للمنهاج الوزاري — تُستخدم لرفع وتنظيم فيديوهات الذكاء الاصطناعي التعليمية',
                 'full_year', 0.00, 1, 1, 'tawjihi_2008', 'scientific')",
            [$uuid, $subjectId, $teacherId]
        );

        if (!$courseId) {
            throw new \RuntimeException('فشل إنشاء الدورة الرئيسية للمنهاج — تحقق من وجود records في جداول subjects و teachers');
        }

        error_log("[CurriculumService] Created master system course id={$courseId}");
        return (int)$courseId;
    }

    private static string $storagePath = __DIR__ . '/../../storage/curriculum';
    private static string $manifestFile = __DIR__ . '/../../storage/curriculum/manifest.json';

    public static function ensureStorage(): void
    {
        if (!is_dir(self::$storagePath)) {
            mkdir(self::$storagePath, 0777, true);
        }
        if (!file_exists(self::$manifestFile)) {
            file_put_contents(self::$manifestFile, json_encode(new \stdClass(), JSON_UNESCAPED_UNICODE | JSON_PRETTY_PRINT));
        }
    }

    /**
     * Get Complete Live Curriculum Tree from Storage Manifest
     */
    public static function getCurriculumTree(): array
    {
        self::ensureStorage();
        if (!file_exists(self::$manifestFile)) {
            return [];
        }
        $json = file_get_contents(self::$manifestFile);
        $tree = json_decode($json, true);
        if (!is_array($tree)) {
            return [];
        }

        // Dynamically enrich manifest nodes with live uploaded videos from MySQL
        try {
            $dbLessons = \App\Core\Database::select(
                "SELECT id, title, curriculum_key, hls_url, duration_seconds 
                 FROM lessons 
                 WHERE hls_url IS NOT NULL AND hls_url != ''"
            );

            if (!empty($dbLessons)) {
                $attachVideos = function (&$node) use (&$attachVideos, $dbLessons) {
                    if (!is_array($node)) return;
                    if (isset($node['lessons']) && is_array($node['lessons'])) {
                        foreach ($node['lessons'] as &$lesson) {
                            if (!is_array($lesson)) continue;
                            $lessonId = (string)($lesson['id'] ?? '');
                            $lessonFile = (string)($lesson['file'] ?? '');
                            $lessonFileNoExt = preg_replace('/\.md$/i', '', $lessonFile);
                            $lessonTitle = (string)($lesson['title'] ?? '');

                            foreach ($dbLessons as $dbl) {
                                $currKey = (string)($dbl['curriculum_key'] ?? '');
                                $currKeyNoExt = preg_replace('/\.md$/i', '', $currKey);
                                $dbTitle = (string)($dbl['title'] ?? '');

                                $matched = false;
                                if ($currKey !== '' && ($currKey === $lessonFile || $currKeyNoExt === $lessonFileNoExt)) {
                                    $matched = true;
                                } elseif ($currKeyNoExt !== '' && str_ends_with($currKeyNoExt, $lessonId)) {
                                    $matched = true;
                                } elseif ($dbTitle !== '' && ($dbTitle === $lessonTitle || str_contains($lessonTitle, $dbTitle) || str_contains($dbTitle, $lessonTitle))) {
                                    $matched = true;
                                }

                                if ($matched) {
                                    $lesson['has_video'] = true;
                                    $lesson['video_url'] = $dbl['hls_url'];
                                    if (!empty($dbl['duration_seconds'])) {
                                        $lesson['duration_seconds'] = (int)$dbl['duration_seconds'];
                                    }
                                    break;
                                }
                            }
                        }
                    }
                    foreach ($node as &$child) {
                        if (is_array($child)) {
                            $attachVideos($child);
                        }
                    }
                };

                $attachVideos($tree);
            }
        } catch (\Throwable $e) {
            error_log("Enrich curriculum tree notice: " . $e->getMessage());
        }

        return $tree;
    }

    /** Resolve a manifest lesson slug to its canonical title/file. */
    public static function findLessonById(string $lessonId): ?array
    {
        $walk = function ($node) use (&$walk, $lessonId): ?array {
            if (!is_array($node)) return null;
            if (isset($node['lessons']) && is_array($node['lessons'])) {
                foreach ($node['lessons'] as $lesson) {
                    if (is_array($lesson) && (string)($lesson['id'] ?? '') === $lessonId) return $lesson;
                }
            }
            foreach ($node as $value) {
                $found = $walk($value);
                if ($found !== null) return $found;
            }
            return null;
        };
        return $walk(self::getCurriculumTree());
    }

    /** Resolve a manifest file path to its canonical lesson record. */
    public static function findLessonByFile(string $file): ?array
    {
        $walk = function ($node) use (&$walk, $file): ?array {
            if (!is_array($node)) return null;
            if (isset($node['lessons']) && is_array($node['lessons'])) {
                foreach ($node['lessons'] as $lesson) {
                    if (is_array($lesson) && (string)($lesson['file'] ?? '') === $file) return $lesson;
                }
            }
            foreach ($node as $value) {
                $found = $walk($value);
                if ($found !== null) return $found;
            }
            return null;
        };
        return $walk(self::getCurriculumTree());
    }

    /**
     * Save/Update Complete Curriculum Tree Manifest
     */
    public static function saveCurriculumTree(array $tree): bool
    {
        self::ensureStorage();
        return file_put_contents(self::$manifestFile, json_encode($tree, JSON_UNESCAPED_UNICODE | JSON_PRETTY_PRINT)) !== false;
    }

    /**
     * Merge Newly Extracted PDF Structure into Live Tree
     */
    public static function mergeExtractedCurriculum(array $extracted): array
    {
        self::ensureStorage();
        $tree = self::getCurriculumTree();

        $gradeKey = $extracted['grade_key'] ?? 'general_grade';
        $gradeName = $extracted['grade_name'] ?? 'الصف الدراسي';

        $subKey = $extracted['subject_key'] ?? 'general_subject';
        $subName = $extracted['subject_name'] ?? 'المبحث';

        $semKey = $extracted['semester_key'] ?? 'semester_1';
        $semName = $extracted['semester_name'] ?? 'الفصل الدراسي الأول';

        if (!isset($tree[$gradeKey])) {
            $tree[$gradeKey] = [
                'name'     => $gradeName,
                'subjects' => []
            ];
        }

        if (!isset($tree[$gradeKey]['subjects'][$subKey])) {
            $tree[$gradeKey]['subjects'][$subKey] = [
                'name'      => $subName,
                'semesters' => []
            ];
        }

        if (!isset($tree[$gradeKey]['subjects'][$subKey]['semesters'][$semKey])) {
            $tree[$gradeKey]['subjects'][$subKey]['semesters'][$semKey] = [
                'name'  => $semName,
                'units' => []
            ];
        }

        // Add / Update Units & Lessons
        foreach ($extracted['units'] ?? [] as $unit) {
            $unitKey = $unit['unit_key'] ?? ('unit_' . mt_rand(100, 999));
            $unitName = $unit['unit_name'] ?? 'الوحدة الدراسية';

            $unitLessons = [];
            foreach ($unit['lessons'] ?? [] as $les) {
                $lesId = $les['lesson_id'] ?? ('les_' . mt_rand(1000, 9999));
                $lesTitle = $les['title'] ?? 'الدرس';
                $lesOutcomes = $les['outcomes'] ?? [];
                $relFilePath = "{$gradeKey}/{$subKey}/{$semKey}/{$unitKey}/{$lesId}.md";
                $mdContent = $les['markdown_content'] ?? "# {$lesTitle}\n\nنتاجات التعلم المستهدفة للمنهاج الرسمي.";

                // Save MD file to disk
                self::saveLessonMarkdown($relFilePath, $mdContent);

                $unitLessons[] = [
                    'id'       => $lesId,
                    'title'    => $lesTitle,
                    'outcomes' => $lesOutcomes,
                    'file'     => $relFilePath
                ];
            }

            $tree[$gradeKey]['subjects'][$subKey]['semesters'][$semKey]['units'][$unitKey] = [
                'name'    => $unitName,
                'lessons' => $unitLessons
            ];
        }

        self::saveCurriculumTree($tree);
        return $tree;
    }

    /**
     * Save Single Lesson Markdown Content to Hierarchical File System
     */
    public static function saveLessonMarkdown(string $relativePath, string $content): bool
    {
        self::ensureStorage();
        $fullPath = self::$storagePath . '/' . ltrim($relativePath, '/');
        $dir = dirname($fullPath);
        if (!is_dir($dir)) {
            mkdir($dir, 0777, true);
        }
        return file_put_contents($fullPath, $content) !== false;
    }

    /**
     * Retrieve Lesson Markdown Content
     */
    public static function getLessonMarkdown(string $relativePath): string
    {
        self::ensureStorage();
        $fullPath = self::$storagePath . '/' . ltrim($relativePath, '/');
        if (file_exists($fullPath)) {
            return file_get_contents($fullPath);
        }
        return "# محتوى المنهاج\nالمحتوى المعتمد للمنهاج الرسمي.";
    }

    public static function saveLessonAiAssets(string $relativePath, array $assets): bool
    {
        self::ensureStorage();
        $baseName = preg_replace('/\.md$/i', '', ltrim($relativePath, '/'));
        $jsonPath = self::$storagePath . '/' . $baseName . '_ai_assets.json';
        
        $dir = dirname($jsonPath);
        if (!is_dir($dir)) {
            mkdir($dir, 0777, true);
        }
        return file_put_contents($jsonPath, json_encode($assets, JSON_UNESCAPED_UNICODE | JSON_PRETTY_PRINT)) !== false;
    }

    public static function getLessonAiAssets(string $relativePath): array
    {
        self::ensureStorage();
        $baseName = preg_replace('/\.md$/i', '', ltrim($relativePath, '/'));
        $jsonPath = self::$storagePath . '/' . $baseName . '_ai_assets.json';
        
        if (file_exists($jsonPath)) {
            return json_decode(file_get_contents($jsonPath), true) ?: [];
        }
        return [];
    }

    public static function saveLessonLabData(string $relativePath, array $labData): bool
    {
        self::ensureStorage();
        $baseName = preg_replace('/\.md$/i', '', ltrim($relativePath, '/'));
        $jsonPath = self::$storagePath . '/' . $baseName . '_lab.json';
        
        $dir = dirname($jsonPath);
        if (!is_dir($dir)) {
            mkdir($dir, 0777, true);
        }
        return file_put_contents($jsonPath, json_encode($labData, JSON_UNESCAPED_UNICODE | JSON_PRETTY_PRINT)) !== false;
    }

    public static function getLessonLabData(string $relativePath): array
    {
        self::ensureStorage();
        $baseName = preg_replace('/\.md$/i', '', ltrim($relativePath, '/'));
        $jsonPath = self::$storagePath . '/' . $baseName . '_lab.json';
        
        if (file_exists($jsonPath)) {
            return json_decode(file_get_contents($jsonPath), true) ?: [];
        }
        return [];
    }

    /**
     * Fast Keyword Search across All Markdown Files
     */
    public static function searchCurriculum(string $query): array
    {
        $tree = self::getCurriculumTree();
        $results = [];
        $queryClean = mb_strtolower(trim($query));
        if (empty($queryClean)) return [];

        foreach ($tree as $gradeKey => $grade) {
            foreach ($grade['subjects'] ?? [] as $subKey => $subject) {
                foreach ($subject['semesters'] ?? [] as $semKey => $semester) {
                    foreach ($semester['units'] ?? [] as $unitKey => $unit) {
                        foreach ($unit['lessons'] ?? [] as $lesson) {
                            $matches = false;
                            if (str_contains(mb_strtolower($lesson['title']), $queryClean) ||
                                str_contains(mb_strtolower($unit['name']), $queryClean) ||
                                str_contains(mb_strtolower($subject['name']), $queryClean)) {
                                $matches = true;
                            }
                            if (!$matches && !empty($lesson['outcomes'])) {
                                foreach ($lesson['outcomes'] as $out) {
                                    if (str_contains(mb_strtolower($out), $queryClean)) {
                                        $matches = true;
                                        break;
                                    }
                                }
                            }
                            if ($matches) {
                                $results[] = [
                                    'grade'     => $grade['name'],
                                    'subject'   => $subject['name'],
                                    'unit'      => $unit['name'],
                                    'lesson'    => $lesson['title'],
                                    'file_path' => $lesson['file'],
                                    'outcomes'  => $lesson['outcomes']
                                ];
                            }
                        }
                    }
                }
            }
        }

        return $results;
    }

    /**
     * Retrieve Context for Video Analysis
     */
    public static function getCurriculumContext(int $courseId, string $lessonTitle): array
    {
        $tree = self::getCurriculumTree();
        $walk = function ($node, string $subject = 'المبحث الدراسي', string $unit = 'الوحدة التعليمية') use (&$walk, $lessonTitle): ?array {
            if (!is_array($node)) return null;
            if (isset($node['semesters']) && isset($node['name'])) {
                $subject = (string)$node['name'];
            }
            if (isset($node['lessons']) && is_array($node['lessons'])) {
                $unit = (string)($node['name'] ?? $unit);
                foreach ($node['lessons'] as $lesson) {
                    if (!is_array($lesson)) continue;
                    if ((string)($lesson['title'] ?? '') === $lessonTitle) {
                        return [
                            'grade'       => 'الصف العاشر',
                            'subject'     => $subject,
                            'unit'        => $unit,
                            'core_topics' => array_values(array_filter(array_map('strval', $lesson['outcomes'] ?? []))),
                            'lesson_file' => (string)($lesson['file'] ?? '')
                        ];
                    }
                }
            }
            foreach ($node as $value) {
                $found = $walk($value, $subject, $unit);
                if ($found !== null) return $found;
            }
            return null;
        };

        $matched = $walk($tree);
        if ($matched !== null) return $matched;

        // Safe generic context when the lesson is not in the manifest.
        return [
            'grade'       => 'المرحلة التعليمية المعتمدة',
            'subject'     => 'المبحث الدراسي',
            'unit'        => 'الوحدة التعليمية',
            'core_topics' => ['تحليل المفاهيم الأساسية', 'التطبيقات والمسائل النموذجية']
        ];
    }
}