import "server-only";

const ACCOUNTS_BASE_URL = process.env.GOOYAL_ACCOUNTS_BASE_URL!;
const CLIENT_ID = process.env.GOOYAL_CLIENT_ID!;
const CLIENT_SECRET = process.env.GOOYAL_CLIENT_SECRET!;
const SCOPE = process.env.GOOYAL_OAUTH_SCOPE!;

function basicAuthHeader() {
  return "Basic " + Buffer.from(`${CLIENT_ID}:${CLIENT_SECRET}`).toString("base64");
}

const ERROR_MESSAGES_FA: Record<string, string> = {
  invalid_grant: "کد تایید نامعتبر یا منقضی شده است.",
  invalid_client: "خطا در پیکربندی سرویس احراز هویت. لطفاً بعداً تلاش کنید.",
  invalid_request: "درخواست نامعتبر است.",
  unsupported_grant_type: "خطا در پیکربندی سرویس احراز هویت.",
};

export class GooyalAuthError extends Error {
  constructor(
    public status: number,
    public code: string,
    description?: string,
  ) {
    super(ERROR_MESSAGES_FA[code] ?? description ?? code);
  }
}

export interface RequestOtpResult {
  phone_number: string;
  otp_expire: string;
  ttl: number;
}

export async function requestOtp(phoneNumber: string): Promise<RequestOtpResult> {
  const res = await fetch(`${ACCOUNTS_BASE_URL}/users/api/request_otp/`, {
    method: "POST",
    headers: { "Content-Type": "application/json" },
    body: JSON.stringify({ phone_number: phoneNumber }),
    cache: "no-store",
  });
  const data = await res.json().catch(() => ({}));
  if (!res.ok) {
    throw new GooyalAuthError(res.status, data.error ?? "request_otp_failed", data.error_description ?? data.detail);
  }
  return data;
}

export interface GooyalTokenResponse {
  access_token: string;
  refresh_token?: string;
  token_type: string;
  expires_in: number;
  scope: string;
}

export async function exchangeOtpForToken(phoneNumber: string, otp: string): Promise<GooyalTokenResponse> {
  const body = new URLSearchParams({
    grant_type: "password",
    username: phoneNumber,
    password: otp,
    scope: SCOPE,
    auth_fields: "phone_number:otp",
  });
  const res = await fetch(`${ACCOUNTS_BASE_URL}/oauth2/token/`, {
    method: "POST",
    headers: {
      Authorization: basicAuthHeader(),
      "Content-Type": "application/x-www-form-urlencoded",
    },
    body: body.toString(),
    cache: "no-store",
  });
  const data = await res.json().catch(() => ({}));
  if (!res.ok) {
    throw new GooyalAuthError(res.status, data.error ?? "token_exchange_failed", data.error_description);
  }
  return data;
}

export async function refreshAccessToken(refreshToken: string): Promise<GooyalTokenResponse> {
  const body = new URLSearchParams({
    grant_type: "refresh_token",
    refresh_token: refreshToken,
  });
  const res = await fetch(`${ACCOUNTS_BASE_URL}/oauth2/token/`, {
    method: "POST",
    headers: {
      Authorization: basicAuthHeader(),
      "Content-Type": "application/x-www-form-urlencoded",
    },
    body: body.toString(),
    cache: "no-store",
  });
  const data = await res.json().catch(() => ({}));
  if (!res.ok) {
    throw new GooyalAuthError(res.status, data.error ?? "refresh_failed", data.error_description);
  }
  return data;
}