<?php

namespace App\Controllers;

use App\Core\Request;
use App\Core\Response;
use App\Core\Database;
use App\Core\Security;
use App\Core\Validator;

class ChatController
{
    /**
     * List all active conversations for the authenticated user (Student or Teacher)
     * GET /api/chat/conversations
     */
    public function getConversations(Request $request, Response $response): void
    {
        $userId = $request->user_id;

        // Find all distinct other parties in conversations
        $sql = "
            SELECT 
                u.id as user_id,
                u.uuid as user_uuid,
                u.full_name as encrypted_name,
                u.role as user_role,
                tp.specialization,
                m.last_message,
                m.last_message_type,
                m.last_message_at,
                COALESCE(unread.unread_count, 0) as unread_count
            FROM (
                SELECT 
                    CASE WHEN sender_id = ? THEN receiver_id ELSE sender_id END as other_user_id,
                    message as last_message,
                    message_type as last_message_type,
                    created_at as last_message_at,
                    ROW_NUMBER() OVER (
                        PARTITION BY (CASE WHEN sender_id = ? THEN receiver_id ELSE sender_id END) 
                        ORDER BY created_at DESC
                    ) as rn
                FROM chat_messages
                WHERE sender_id = ? OR receiver_id = ?
            ) m
            JOIN users u ON u.id = m.other_user_id
            LEFT JOIN teacher_profiles tp ON tp.user_id = u.id
            LEFT JOIN (
                SELECT sender_id, COUNT(*) as unread_count 
                FROM chat_messages 
                WHERE receiver_id = ? AND is_read = 0 
                GROUP BY sender_id
            ) unread ON unread.sender_id = u.id
            WHERE m.rn = 1
            ORDER BY m.last_message_at DESC
        ";

        try {
            $rows = Database::select($sql, [$userId, $userId, $userId, $userId, $userId]);
        } catch (\Exception $e) {
            // Fallback for MySQL setups without window functions
            $rows = Database::select("
                SELECT 
                    u.id as user_id,
                    u.uuid as user_uuid,
                    u.full_name as encrypted_name,
                    u.role as user_role,
                    tp.specialization
                FROM users u
                LEFT JOIN teacher_profiles tp ON tp.user_id = u.id
                WHERE u.id IN (
                    SELECT DISTINCT CASE WHEN sender_id = ? THEN receiver_id ELSE sender_id END
                    FROM chat_messages
                    WHERE sender_id = ? OR receiver_id = ?
                )
            ", [$userId, $userId, $userId]);
        }

        $conversations = array_map(function ($row) {
            $rawName = (string)($row['encrypted_name'] ?? '');
            $decryptedName = Security::decrypt($rawName) ?: $rawName;

            return [
                'user_id'           => (int)$row['user_id'],
                'user_uuid'         => $row['user_uuid'] ?? '',
                'full_name'         => $decryptedName ?: ($row['user_role'] === 'teacher' ? 'أستاذ المادة' : 'طالب صَقِل'),
                'role'              => $row['user_role'] ?? 'student',
                'specialization'    => $row['specialization'] ?? null,
                'last_message'      => $row['last_message'] ?? '',
                'last_message_type' => $row['last_message_type'] ?? 'text',
                'last_message_at'   => $row['last_message_at'] ?? null,
                'unread_count'      => (int)($row['unread_count'] ?? 0),
            ];
        }, $rows);

        $response->json([
            'status' => 'success',
            'data'   => $conversations
        ]);
    }

    /**
     * Get chat message history between authenticated user and another user
     * GET /api/chat/messages?other_user_id=123&course_id=456
     */
    public function getMessages(Request $request, Response $response): void
    {
        $userId = $request->user_id;
        $queryParams = $request->getQueryParams();

        $otherUserId = (int)($queryParams['other_user_id'] ?? $queryParams['user_id'] ?? 0);
        $courseId = !empty($queryParams['course_id']) ? (int)$queryParams['course_id'] : null;
        $limit = min(100, max(1, (int)($queryParams['limit'] ?? 50)));

        if (!$otherUserId) {
            $response->status(400)->json([
                'status'  => 'error',
                'message' => 'معرف الطرف الآخر (other_user_id) مطلوب'
            ]);
            return;
        }

        // Fetch other user info
        $otherUser = Database::selectOne("SELECT id, uuid, full_name, role FROM users WHERE id = ? LIMIT 1", [$otherUserId]);
        if (!$otherUser) {
            $response->status(404)->json(['status' => 'error', 'message' => 'المستخدم الآخر غير موجود']);
            return;
        }

        $rawOtherName = (string)($otherUser['full_name'] ?? '');
        $otherUserName = Security::decrypt($rawOtherName) ?: $rawOtherName;

        // Fetch messages bidirectional
        $sql = "
            SELECT id, uuid, sender_id, receiver_id, course_id, lesson_id, message, message_type, media_url, is_read, read_at, created_at
            FROM chat_messages
            WHERE ((sender_id = ? AND receiver_id = ?) OR (sender_id = ? AND receiver_id = ?))
        ";
        $params = [$userId, $otherUserId, $otherUserId, $userId];

        if ($courseId) {
            $sql .= " AND (course_id = ? OR course_id IS NULL)";
            $params[] = $courseId;
        }

        $sql .= " ORDER BY created_at ASC LIMIT ?";
        $params[] = $limit;

        $messages = Database::select($sql, $params);

        // Mark unread messages sent by other user to me as read
        Database::query(
            "UPDATE chat_messages SET is_read = 1, read_at = NOW() WHERE sender_id = ? AND receiver_id = ? AND is_read = 0",
            [$otherUserId, $userId]
        );

        $formattedMessages = array_map(function ($msg) use ($userId) {
            return [
                'id'           => (int)$msg['id'],
                'uuid'         => $msg['uuid'],
                'is_mine'      => ((int)$msg['sender_id'] === (int)$userId),
                'sender_id'    => (int)$msg['sender_id'],
                'receiver_id'  => (int)$msg['receiver_id'],
                'course_id'    => $msg['course_id'] ? (int)$msg['course_id'] : null,
                'lesson_id'    => $msg['lesson_id'] ? (int)$msg['lesson_id'] : null,
                'message'      => $msg['message'],
                'message_type' => $msg['message_type'],
                'media_url'    => $msg['media_url'],
                'is_read'      => (bool)$msg['is_read'],
                'read_at'      => $msg['read_at'],
                'created_at'   => $msg['created_at'],
            ];
        }, $messages);

        $response->json([
            'status' => 'success',
            'data'   => [
                'other_user' => [
                    'id'        => (int)$otherUser['id'],
                    'uuid'      => $otherUser['uuid'],
                    'full_name' => $otherUserName,
                    'role'      => $otherUser['role'],
                ],
                'messages' => $formattedMessages
            ]
        ]);
    }

    /**
     * Send a new chat message (Text, Voice Note, Image, File)
     * POST /api/chat/messages
     */
    public function sendMessage(Request $request, Response $response): void
    {
        $userId = $request->user_id;
        $body = $request->getBody();

        $validator = new Validator();
        $isValid = $validator->validate($body, [
            'receiver_id' => 'required',
            'message'     => 'required'
        ]);

        if (!$isValid) {
            $response->status(400)->json([
                'status'  => 'error',
                'message' => 'معرف المستقبل ونص الرسالة مطلوبان',
                'errors'  => $validator->getErrors()
            ]);
            return;
        }

        $receiverId  = (int)$body['receiver_id'];
        $messageText = trim((string)$body['message']);
        $messageType = (string)($body['message_type'] ?? 'text');
        $mediaUrl    = !empty($body['media_url']) ? trim((string)$body['media_url']) : null;
        $courseId    = !empty($body['course_id']) ? (int)$body['course_id'] : null;
        $lessonId    = !empty($body['lesson_id']) ? (int)$body['lesson_id'] : null;

        if (!in_array($messageType, ['text', 'voice', 'image', 'file'], true)) {
            $messageType = 'text';
        }

        // Validate receiver exists
        $receiver = Database::selectOne("SELECT id, role FROM users WHERE id = ? LIMIT 1", [$receiverId]);
        if (!$receiver) {
            $response->status(404)->json([
                'status'  => 'error',
                'message' => 'المستخدم المستلم غير موجود'
            ]);
            return;
        }

        $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)
        );

        $messageId = Database::insert(
            "INSERT INTO chat_messages (uuid, sender_id, receiver_id, course_id, lesson_id, message, message_type, media_url, is_read) 
             VALUES (?, ?, ?, ?, ?, ?, ?, ?, 0)",
            [$uuid, $userId, $receiverId, $courseId, $lessonId, $messageText, $messageType, $mediaUrl]
        );

        $response->status(201)->json([
            'status'  => 'success',
            'message' => 'تم إرسال الرسالة بنجاح',
            'data'    => [
                'id'           => $messageId,
                'uuid'         => $uuid,
                'sender_id'    => $userId,
                'receiver_id'  => $receiverId,
                'is_mine'      => true,
                'course_id'    => $courseId,
                'lesson_id'    => $lessonId,
                'message'      => $messageText,
                'message_type' => $messageType,
                'media_url'    => $mediaUrl,
                'is_read'      => false,
                'created_at'   => date('Y-m-d H:i:s'),
            ]
        ]);
    }

    /**
     * Mark all messages in a conversation as read
     * POST /api/chat/read
     */
    public function markAsRead(Request $request, Response $response): void
    {
        $userId = $request->user_id;
        $body = $request->getBody();

        $senderId = (int)($body['sender_id'] ?? 0);
        if (!$senderId) {
            $response->status(400)->json([
                'status'  => 'error',
                'message' => 'معرف المرسل مطلوب'
            ]);
            return;
        }

        Database::query(
            "UPDATE chat_messages SET is_read = 1, read_at = NOW() WHERE sender_id = ? AND receiver_id = ? AND is_read = 0",
            [$senderId, $userId]
        );

        $response->json([
            'status'  => 'success',
            'message' => 'تم تحديث حالة القراءة'
        ]);
    }

    /**
     * Get total unread count for badge notification
     * GET /api/chat/unread-count
     */
    public function getUnreadCount(Request $request, Response $response): void
    {
        $userId = $request->user_id;

        $row = Database::selectOne(
            "SELECT COUNT(*) as unread_total FROM chat_messages WHERE receiver_id = ? AND is_read = 0",
            [$userId]
        );

        $response->json([
            'status' => 'success',
            'data'   => [
                'unread_count' => (int)($row['unread_total'] ?? 0)
            ]
        ]);
    }
}