export const prerender = false;

const TOKEN_ENDPOINT = "https://accounts.spotify.com/api/token";

function requiredEnv(name: string): string {
	const v = import.meta.env[name];
	if (!v) throw new Error(`Missing env var: ${name}`);
	return v;
}

export async function GET({ request, url }: { request: Request; url: URL }) {
	try {
		const reqUrl = new URL(request.url);
		const code =
			reqUrl.searchParams.get("code") ?? url.searchParams.get("code");
		if (!code) {
			return new Response(
				[
					"Missing ?code",
					"",
					`request.url: ${request.url}`,
					`astro.url: ${url.toString()}`,
				].join("\n"),
				{
					status: 400,
					headers: { "Content-Type": "text/plain; charset=utf-8" },
				},
			);
		}

		const client_id = requiredEnv("SPOTIFY_CLIENT_ID");
		const client_secret = requiredEnv("SPOTIFY_CLIENT_SECRET");
		const redirect_uri =
			import.meta.env.SPOTIFY_REDIRECT_URI ??
			`${reqUrl.origin}/api/spotify/callback`;

		const basic = Buffer.from(`${client_id}:${client_secret}`).toString(
			"base64",
		);

		const res = await fetch(TOKEN_ENDPOINT, {
			method: "POST",
			headers: {
				Authorization: `Basic ${basic}`,
				"Content-Type": "application/x-www-form-urlencoded",
			},
			body: new URLSearchParams({
				grant_type: "authorization_code",
				code,
				redirect_uri,
			}),
		});

		const text = await res.text();
		if (!res.ok) {
			return new Response(
				`Spotify token exchange failed (${res.status}).\n\n${text}`,
				{
					status: 500,
					headers: { "Content-Type": "text/plain; charset=utf-8" },
				},
			);
		}

		const data = JSON.parse(text) as {
			access_token?: string;
			refresh_token?: string;
			scope?: string;
			expires_in?: number;
			token_type?: string;
		};

		const refresh = data.refresh_token;
		if (!refresh) {
			return new Response(
				`No refresh_token returned.\n\nThis usually means you already authorized this app before.\nGo to https://www.spotify.com/account/apps/ and remove access, then try again.\n\nRaw response:\n${text}`,
				{
					status: 500,
					headers: { "Content-Type": "text/plain; charset=utf-8" },
				},
			);
		}

		return new Response(
			[
				"Refresh token generated successfully.",
				"",
				`SPOTIFY_REFRESH_TOKEN=${refresh}`,
				"",
				"Put that into your .env (server-side).",
			].join("\n"),
			{ status: 200, headers: { "Content-Type": "text/plain; charset=utf-8" } },
		);
	} catch (err) {
		const message = err instanceof Error ? err.message : String(err);
		return new Response(message, {
			status: 500,
			headers: { "Content-Type": "text/plain; charset=utf-8" },
		});
	}
}