import { NextRequest, NextResponse } from 'next/server';
import { adminFirestore, adminMessaging } from '@/lib/firebase-admin';

export async function POST(req: NextRequest) {
    console.log("[/api/call-notification] Received a POST request.");
    
    let recipientUidForError: string | null = null;

    try {
        const { recipientUid, callerName, channelName, callType, callerPhoto } = await req.json();
        recipientUidForError = recipientUid;
        console.log("[/api/call-notification] Request body parsed:", { recipientUid, callerName, channelName, callType });

        if (!recipientUid || !callerName || !channelName || !callType) {
            console.log("[/api/call-notification] Missing required fields.");
            return NextResponse.json({ error: 'Missing required fields' }, { status: 400 });
        }

        const userDoc = await adminFirestore.collection('users').doc(recipientUid).get();
        
        if (!userDoc.exists) {
            console.log(`[/api/call-notification] Recipient user not found: ${recipientUid}`);
            return NextResponse.json({ error: 'Recipient user not found' }, { status: 404 });
        }
        
        const fcmToken = userDoc.data()?.fcmToken;
        if (!fcmToken) {
            console.log(`[/api/call-notification] Notification not sent: User ${recipientUid} does not have an FCM token.`);
            return NextResponse.json({ success: true, message: 'User has no FCM token.' });
        }

        const message = {
            token: fcmToken,
            notification: {
                title: `Incoming ${callType} call`,
                body: `From: ${callerName}`,
            },
            webpush: {
                notification: {
                    icon: callerPhoto || '/favicon.ico',
                    badge: '/favicon.ico',
                    actions: [
                        { action: 'answer', title: 'Answer' },
                        { action: 'decline', title: 'Decline' }
                    ],
                    data: {
                        type: 'incoming-call',
                        channelName: channelName,
                    },
                    requireInteraction: "true" as const,
                    tag: `call-${channelName}`
                }
            },
        };
        console.log("[/api/call-notification] Prepared message payload:", message);

        const response = await adminMessaging.send(message);
        console.log('[/api/call-notification] Successfully sent call notification:', response);
        return NextResponse.json({ success: true, messageId: response });

    } catch (error: any) {
        console.error('[/api/call-notification] CRITICAL ERROR:', error);
        
        let errorMessage = 'Internal Server Error';
        let statusCode = 500;

        if (error.code === 'messaging/invalid-argument') {
            errorMessage = 'Invalid argument provided for FCM message.';
            statusCode = 400;
        } else if (error.code === 'messaging/registration-token-not-registered') {
             errorMessage = `The FCM token for user ${recipientUidForError} is no longer valid. It might be expired.`;
             if (recipientUidForError) {
                await adminFirestore.collection('users').doc(recipientUidForError).update({ fcmToken: '' });
             }
             statusCode = 404;
        } else if (error.code === 'messaging/invalid-registration-token') {
             errorMessage = `Invalid FCM registration token for user ${recipientUidForError}.`;
             if (recipientUidForError) {
                await adminFirestore.collection('users').doc(recipientUidForError).update({ fcmToken: '' });
             }
             statusCode = 400;
        }
        
        return NextResponse.json({ error: 'Failed to send notification', details: errorMessage, rawError: error.message }, { status: statusCode });
    }
}