const SPOTIFY_TOKEN_URL = "https://accounts.spotify.com/api/token";
const configuredBaseUrl = (
  process.env as Record<string, string | undefined>
).SPOTIRIP_BASE_URL?.trim().replace(/\/+$/, "");
export const SPOTIRIP_BASE_URL =
  configuredBaseUrl || "https://spotirip.auroradragon.dev";
export const SPOTIFY_REDIRECT_URI = SPOTIRIP_BASE_URL + "/spotify/callback";

type StoredSpotifySession = {
  accessToken?: string;
  refreshToken?: string;
  expiresAt?: number;
};

type TokenResponse = {
  access_token: string;
  token_type: string;
  scope?: string;
  expires_in: number;
  refresh_token?: string;
};

export function parseCookies(request: Request) {
  const raw = request.headers.get("cookie") || "";
  const cookies: Record<string, string> = {};
  for (const part of raw.split(";")) {
    const index = part.indexOf("=");
    if (index < 0) continue;
    const key = part.slice(0, index).trim();
    const value = part.slice(index + 1).trim();
    if (key) cookies[key] = decodeURIComponent(value);
  }
  return cookies;
}

export function readSpotifySession(request: Request): StoredSpotifySession {
  const cookies = parseCookies(request);
  const expiresAt = Number(cookies.spotirip_spotify_expires || 0);
  return {
    accessToken: cookies.spotirip_spotify_access,
    refreshToken: cookies.spotirip_spotify_refresh,
    expiresAt: Number.isFinite(expiresAt) ? expiresAt : 0,
  };
}

export function makeCookie(
  name: string,
  value: string,
  options: { maxAge?: number; httpOnly?: boolean } = {},
) {
  const segments = [
    `${name}=${encodeURIComponent(value)}`,
    "Path=/",
    "Secure",
    "SameSite=Lax",
  ];
  if (options.httpOnly !== false) segments.push("HttpOnly");
  if (typeof options.maxAge === "number") segments.push(`Max-Age=${Math.max(0, Math.floor(options.maxAge))}`);
  return segments.join("; ");
}

export function clearCookie(name: string) {
  return `${name}=; Path=/; Secure; HttpOnly; SameSite=Lax; Max-Age=0`;
}

function spotifyBasicAuth() {
  const clientId = process.env.SPOTIFY_CLIENT_ID;
  const clientSecret = process.env.SPOTIFY_CLIENT_SECRET;
  if (!clientId || !clientSecret) {
    throw new Error("Spotify credentials are not configured.");
  }
  return "Basic " + Buffer.from(`${clientId}:${clientSecret}`).toString("base64");
}

export async function exchangeSpotifyCode(code: string) {
  const response = await fetch(SPOTIFY_TOKEN_URL, {
    method: "POST",
    headers: {
      Authorization: spotifyBasicAuth(),
      "Content-Type": "application/x-www-form-urlencoded",
    },
    body: new URLSearchParams({
      grant_type: "authorization_code",
      code,
      redirect_uri: SPOTIFY_REDIRECT_URI,
    }),
  });

  if (!response.ok) {
    const message = await response.text();
    throw new Error(`Spotify token exchange failed (${response.status}): ${message.slice(0, 300)}`);
  }

  return (await response.json()) as TokenResponse;
}

export async function refreshSpotifyToken(refreshToken: string) {
  const response = await fetch(SPOTIFY_TOKEN_URL, {
    method: "POST",
    headers: {
      Authorization: spotifyBasicAuth(),
      "Content-Type": "application/x-www-form-urlencoded",
    },
    body: new URLSearchParams({
      grant_type: "refresh_token",
      refresh_token: refreshToken,
    }),
  });

  if (!response.ok) {
    const message = await response.text();
    throw new Error(`Spotify token refresh failed (${response.status}): ${message.slice(0, 300)}`);
  }

  return (await response.json()) as TokenResponse;
}

export async function ensureSpotifyAccessToken(request: Request) {
  const current = readSpotifySession(request);
  const now = Date.now();
  if (current.accessToken && current.expiresAt && current.expiresAt > now + 60_000) {
    return { accessToken: current.accessToken, setCookies: [] as string[] };
  }

  if (!current.refreshToken) {
    return { accessToken: null, setCookies: [] as string[] };
  }

  const refreshed = await refreshSpotifyToken(current.refreshToken);
  const expiresAt = Date.now() + refreshed.expires_in * 1000;
  const setCookies = [
    makeCookie("spotirip_spotify_access", refreshed.access_token, { maxAge: refreshed.expires_in }),
    makeCookie("spotirip_spotify_expires", String(expiresAt), { maxAge: refreshed.expires_in }),
  ];

  if (refreshed.refresh_token) {
    setCookies.push(
      makeCookie("spotirip_spotify_refresh", refreshed.refresh_token, { maxAge: 60 * 60 * 24 * 30 }),
    );
  }

  return { accessToken: refreshed.access_token, setCookies };
}

export function appendSetCookies(headers: Headers, cookies: string[]) {
  for (const cookie of cookies) headers.append("Set-Cookie", cookie);
}