import { NextRequest, NextResponse } from "next/server";
import { auth } from "@/lib/auth";
import { prisma } from "@/lib/prisma";
import { z } from "zod";

const UpdateSchema = z.object({
  title: z.string().min(1).max(200).optional(),
  model: z.string().optional(),
  contextWindow: z.number().int().positive().optional(),
  systemPrompt: z.string().optional(),
  temperature: z.number().min(0).max(2).optional(),
  showThinking: z.boolean().optional(),
  keepAlive: z.number().int().min(-1).optional(),
});

async function ensureOwner(chatId: string, userId: string) {
  const chat = await prisma.chat.findUnique({ where: { id: chatId } });
  if (!chat || chat.userId !== userId) return null;
  return chat;
}

export async function GET(
  _req: NextRequest,
  { params }: { params: Promise<{ id: string }> },
) {
  const session = await auth();
  if (!session?.user?.id) return NextResponse.json({ error: "Unauthorized" }, { status: 401 });

  const { id } = await params;
  const chat = await prisma.chat.findUnique({
    where: { id },
    include: { messages: { orderBy: { createdAt: "asc" } } },
  });
  if (!chat || chat.userId !== session.user.id)
    return NextResponse.json({ error: "Not found" }, { status: 404 });

  return NextResponse.json({ chat });
}

export async function PATCH(
  req: NextRequest,
  { params }: { params: Promise<{ id: string }> },
) {
  const session = await auth();
  if (!session?.user?.id) return NextResponse.json({ error: "Unauthorized" }, { status: 401 });

  const { id } = await params;
  const existing = await ensureOwner(id, session.user.id);
  if (!existing) return NextResponse.json({ error: "Not found" }, { status: 404 });

  const body = await req.json().catch(() => null);
  const parsed = UpdateSchema.safeParse(body);
  if (!parsed.success) return NextResponse.json({ error: "Invalid body" }, { status: 400 });

  const chat = await prisma.chat.update({ where: { id }, data: parsed.data });
  return NextResponse.json({ chat });
}

export async function DELETE(
  _req: NextRequest,
  { params }: { params: Promise<{ id: string }> },
) {
  const session = await auth();
  if (!session?.user?.id) return NextResponse.json({ error: "Unauthorized" }, { status: 401 });

  const { id } = await params;
  const existing = await ensureOwner(id, session.user.id);
  if (!existing) return NextResponse.json({ error: "Not found" }, { status: 404 });

  await prisma.chat.delete({ where: { id } });
  return NextResponse.json({ ok: true });
}