import { NextRequest, NextResponse } from 'next/server';
import { prisma } from '@/lib/prisma';
import type { FeedItem, FeedResponse } from '@/app/types/feed';

// Contract
// Inputs: search params { before?: ISOString, limit?: number }
// Output: { items: FeedItem[], nextCursor: ISOString | null }

export async function GET(req: NextRequest) {
  const { searchParams } = new URL(req.url);
  const limitParam = searchParams.get('limit');
  const beforeParam = searchParams.get('before');

  const limit = Math.min(Math.max(Number(limitParam ?? '24'), 1), 60); // 1..60
  const before = beforeParam ? new Date(beforeParam) : null;

  // fetch chunk from both tables
  const [videos, posts] = await Promise.all([
    prisma.video.findMany({
      where: before ? { created_at: { lt: before } } : undefined,
      orderBy: { created_at: 'desc' },
      take: limit,
      include: { author: true },
    }),
    prisma.imagePost.findMany({
      where: before ? { created_at: { lt: before } } : undefined,
      orderBy: { created_at: 'desc' },
      take: limit,
      include: { author: true, images: { orderBy: { order: 'asc' }, take: 1 } },
    }),
  ]);

  const merged: FeedItem[] = [
    ...videos.map((v) => ({
      type: 'video' as const,
      aweme_id: v.aweme_id,
      created_at: v.created_at,
      desc: v.desc,
      video_url: v.video_url,
      cover_url: v.cover_url ?? null,
      width: v.width ?? null,
      height: v.height ?? null,
      author: { nickname: v.author.nickname, avatar_url: v.author.avatar_url ?? null },
      likes: Number(v.digg_count),
    })),
    ...posts.map((p) => ({
      type: 'image' as const,
      aweme_id: p.aweme_id,
      created_at: p.created_at,
      desc: p.desc,
      cover_url: p.images?.[0]?.url ?? null,
      width: p.images?.[0]?.width ?? null,
      height: p.images?.[0]?.height ?? null,
      author: { nickname: p.author.nickname, avatar_url: p.author.avatar_url ?? null },
      likes: Number(p.digg_count),
    })),
  ]
    .sort((a, b) => +new Date(b.created_at as any) - +new Date(a.created_at as any))
    .slice(0, limit);

  const nextCursor = merged.length > 0 ? new Date(merged[merged.length - 1].created_at as any).toISOString() : null;
  const payload: FeedResponse = { items: merged, nextCursor };
  return NextResponse.json(payload);
}