import { NextResponse } from "next/server";
import { auth } from "@/auth";

export async function POST(request: Request) {
	const session = await auth();
	
	if (!session?.user) {
		return NextResponse.json(
			{ error: "Authentication required" },
			{ status: 401 }
		);
	}

	const { prompt } = await request.json();

	const systemPrompt = `
You are an assistant that converts natural language into an ARRAY of calendar events.
TypeScript type:

{
  id?: string,
  title: string,
  description?: string,
  location?: string,
  url?: string,
  start: string, // ISO datetime
  end?: string,
  allDay?: boolean,
  recurrenceRule?: string // valid iCal RRULE string like FREQ=WEEKLY;BYDAY=MO;INTERVAL=1
}[]

Rules:
  - If the user describes multiple events in one prompt, return multiple objects (one per event).
  - Always return a valid JSON array of objects, even if there's only one event.
  - Today is ${new Date().toLocaleString()}.
  - If no time is given, assume allDay event.
  - If no end time is given (and event is not allDay), default to 1 hour after start.
  - If multiple events are described, return multiple.
  - If recurrence is implied (e.g. "every Monday", "daily for 10 days", "monthly on the 15th"), generate a recurrenceRule.
  - Output ONLY valid JSON (no prose).
`;

	const res = await fetch("https://openrouter.ai/api/v1/chat/completions", {
		method: "POST",
		headers: {
			Authorization: `Bearer ${process.env.OPENROUTER_API_KEY}`,
			"Content-Type": "application/json",
		},
		body: JSON.stringify({
			model: "openai/gpt-4.1-nano",
			messages: [
				{ role: "system", content: systemPrompt },
				{ role: "user", content: prompt },
			],
		}),
	});

	const data = await res.json();
	try {
		const content = data.choices[0].message.content;
		const parsed = JSON.parse(content);
		return NextResponse.json(parsed);
	} catch (e) {
		return NextResponse.json(
			{ error: "Failed to parse AI output", raw: data },
			{ status: 500 },
		);
	}
}