import { NextResponse } from 'next/server';
import { getServerSession } from 'next-auth';
import { authOptions } from '@/lib/auth';
import { prisma } from '@/lib/prisma';
import { getHolidayHint } from '@/lib/holidays';

export async function GET(req: Request) {
    try {
        const session = await getServerSession(authOptions);
        if (!session || !session.user) {
            return NextResponse.json({ error: 'Unauthorized' }, { status: 401 });
        }

        const userId = (session.user as any).id;
        if (!userId) {
            return NextResponse.json({ error: 'User ID missing from session' }, { status: 400 });
        }

        const { searchParams } = new URL(req.url);
        const weekStartParam = searchParams.get('weekStart');

        if (!weekStartParam) {
            return NextResponse.json({ error: 'weekStart is required' }, { status: 400 });
        }

        const date = new Date(weekStartParam);
        date.setUTCHours(0, 0, 0, 0);

        // Fetch user preferences
        const user = await prisma.user.findUnique({
            where: { id: userId },
            select: {
                goalFallbackType: true,
                goalDefaultSentence: true,
            }
        });

        // 1. Check if user has a custom set goal for THIS week specifically
        const goal = await prisma.weeklyGoal.findUnique({
            where: {
                userId_weekStart: {
                    userId: userId,
                    weekStart: date,
                },
            },
        });

        if (goal && goal.text && goal.text !== 'your goal of this week' && goal.text !== user?.goalDefaultSentence) {
            return NextResponse.json({ goal: goal.text });
        }

        // 2. Handle Fallbacks based on user settings
        const fallbackType = user?.goalFallbackType || 'quote';

        if (fallbackType === 'next_todo') {
            // Fetch first incomplete task for this week
            const weekEnd = new Date(date);
            weekEnd.setDate(weekEnd.getDate() + 7);

            const nextTask = await prisma.task.findFirst({
                where: {
                    userId,
                    completed: false,
                    scheduledDate: {
                        gte: date,
                        lt: weekEnd
                    }
                },
                orderBy: [
                    { scheduledDate: 'asc' },
                    { order: 'asc' }
                ]
            });

            if (nextTask) {
                return NextResponse.json({ goal: `Next: ${nextTask.title}`, isNextTask: true });
            }
            // If no tasks, fall back to quote or default? Let's go to quote.
        }

        if (fallbackType === 'default') {
            return NextResponse.json({ goal: user?.goalDefaultSentence || 'goal of the week', isDefault: true });
        }

        // 3. Fallback to holiday/celebration hints (High priority for "quote" type)
        const holidayHint = getHolidayHint(date);
        if (holidayHint) {
            return NextResponse.json({ goal: holidayHint, isHoliday: true });
        }

        // 4. Fallback to ZenQuotes motivational quote
        try {
            const res = await fetch('https://zenquotes.io/api/random', { signal: AbortSignal.timeout(3000) });
            if (res.ok) {
                const data = await res.json();
                if (data && data[0] && data[0].q) {
                    return NextResponse.json({ goal: `${data[0].q} — ${data[0].a}`, isQuote: true });
                }
            }
        } catch (e) {
            console.error('Failed to fetch from ZenQuotes:', e);
        }

        // Final default fallback
        return NextResponse.json({ goal: user?.goalDefaultSentence || 'goal of the week', isDefault: true });
    } catch (error) {
        console.error('API Error:', error);
        return NextResponse.json({ error: 'Internal Server Error' }, { status: 500 });
    }
}

// POST delegates to PUT for client compatibility
export async function POST(req: Request) {
    return PUT(req);
}

export async function PUT(req: Request) {
    try {
        const session = await getServerSession(authOptions);
        if (!session || !session.user) {
            return NextResponse.json({ error: 'Unauthorized' }, { status: 401 });
        }

        const userId = (session.user as any).id;
        if (!userId) {
            return NextResponse.json({ error: 'User ID missing from session' }, { status: 400 });
        }

        const { weekStart, text } = await req.json();

        if (!weekStart) {
            return NextResponse.json({ error: 'weekStart is required' }, { status: 400 });
        }

        const date = new Date(weekStart);
        date.setUTCHours(0, 0, 0, 0);

        const goal = await prisma.weeklyGoal.upsert({
            where: {
                userId_weekStart: {
                    userId: userId,
                    weekStart: date,
                },
            },
            update: { text },
            create: {
                userId: userId,
                weekStart: date,
                text,
            },
        });

        return NextResponse.json({ goal: goal.text });
    } catch (error) {
        console.error('API Error:', error);
        return NextResponse.json({ error: 'Internal Server Error' }, { status: 500 });
    }
}