import {
  createCipheriv,
  createDecipheriv,
  createHmac,
  randomBytes,
  timingSafeEqual,
} from "node:crypto";

function required(name: string, min = 32): Buffer {
  const value = process.env[name];
  if (!value) throw new Error(`${name} is required`);
  const decoded =
    name === "PHONE_ENCRYPTION_KEY"
      ? Buffer.from(value, "base64")
      : Buffer.from(value);
  if (decoded.length < min)
    throw new Error(`${name} must be at least ${min} bytes`);
  return decoded;
}
const REQUIRED_KEYS = [
  "PHONE_ENCRYPTION_KEY",
  "PHONE_HMAC_KEY",
  "VERIFICATION_CODE_HMAC_KEY",
  "REFRESH_TOKEN_HMAC_KEY",
  "JWT_SECRET",
] as const;
type AuthSecrets = Record<(typeof REQUIRED_KEYS)[number], Buffer>;
let secrets: AuthSecrets | undefined;
let configuredWebOrigin: string | undefined;

function parseWebOrigin(): string {
  const raw = process.env.WEB_ORIGIN;
  if (!raw) throw new Error("WEB_ORIGIN is required");
  let url: URL;
  try {
    url = new URL(raw);
  } catch {
    throw new Error("WEB_ORIGIN must be an absolute HTTP(S) origin");
  }
  if (
    !["http:", "https:"].includes(url.protocol) ||
    url.username ||
    url.password ||
    url.pathname !== "/" ||
    url.search ||
    url.hash ||
    url.origin !== raw
  )
    throw new Error(
      "WEB_ORIGIN must be one absolute HTTP(S) origin without credentials or path",
    );
  return url.origin;
}

export function validateAuthEnvironment(): void {
  const loaded = Object.fromEntries(
    REQUIRED_KEYS.map((name) => [name, required(name)]),
  ) as unknown as AuthSecrets;
  if (loaded.PHONE_ENCRYPTION_KEY.length !== 32)
    throw new Error("PHONE_ENCRYPTION_KEY must decode to exactly 32 bytes");
  const fingerprints = REQUIRED_KEYS.map((name) =>
    loaded[name].toString("hex"),
  );
  if (new Set(fingerprints).size !== fingerprints.length)
    throw new Error("Auth secrets must be independent");
  const origin = parseWebOrigin();
  if (process.env.DEMO_SMS_CODE_ENABLED === "true" && !demoEnvironmentAllowed())
    throw new Error(
      "DEMO_SMS_CODE_ENABLED is forbidden outside test or local development",
    );
  secrets = loaded;
  configuredWebOrigin = origin;
}
export function resetAuthEnvironmentForTests(): void {
  if (process.env.NODE_ENV !== "test")
    throw new Error("Auth environment reset is test-only");
  secrets = undefined;
  configuredWebOrigin = undefined;
}
function authSecrets(): AuthSecrets {
  if (!secrets) validateAuthEnvironment();
  return secrets!;
}
export const jwtSecret = (): Buffer => authSecrets().JWT_SECRET;
export const webOrigin = (): string => {
  if (!configuredWebOrigin) validateAuthEnvironment();
  return configuredWebOrigin!;
};
const demoEnvironmentAllowed = (): boolean =>
  process.env.NODE_ENV === "test" ||
  (process.env.NODE_ENV === "development" && process.env.APP_ENV === "local");
export const demoSmsCodeEnabled = (): boolean =>
  process.env.DEMO_SMS_CODE_ENABLED === "true" && demoEnvironmentAllowed();
export const phoneHmac = (phone: string): string =>
  createHmac("sha256", authSecrets().PHONE_HMAC_KEY)
    .update(phone)
    .digest("hex");
export const codeHmac = (phoneDigest: string, code: string): string =>
  createHmac("sha256", authSecrets().VERIFICATION_CODE_HMAC_KEY)
    .update(`${phoneDigest}:${code}`)
    .digest("hex");
export const refreshHmac = (token: string): string =>
  createHmac("sha256", authSecrets().REFRESH_TOKEN_HMAC_KEY)
    .update(token)
    .digest("hex");
export const safeEqual = (a: string, b: string): boolean => {
  const x = Buffer.from(a);
  const y = Buffer.from(b);
  return x.length === y.length && timingSafeEqual(x, y);
};
export function encryptPhone(phone: string): Buffer {
  const key = authSecrets().PHONE_ENCRYPTION_KEY;
  if (key.length !== 32)
    throw new Error("PHONE_ENCRYPTION_KEY must decode to exactly 32 bytes");
  const nonce = randomBytes(12);
  const cipher = createCipheriv("aes-256-gcm", key, nonce);
  const body = Buffer.concat([cipher.update(phone, "utf8"), cipher.final()]);
  return Buffer.concat([nonce, cipher.getAuthTag(), body]);
}
export function decryptPhone(value: Buffer): string {
  const key = authSecrets().PHONE_ENCRYPTION_KEY;
  const decipher = createDecipheriv("aes-256-gcm", key, value.subarray(0, 12));
  decipher.setAuthTag(value.subarray(12, 28));
  return Buffer.concat([
    decipher.update(value.subarray(28)),
    decipher.final(),
  ]).toString();
}
export const envInt = (name: string, fallback: number): number => {
  const n = Number(process.env[name] ?? fallback);
  return Number.isInteger(n) && n > 0 ? n : fallback;
};