server/src/services/oidcService.ts

import crypto from 'crypto';
import jwt from 'jsonwebtoken';
import { db } from '../db/database';
import { JWT_SECRET, SESSION_DURATION_SECONDS } from '../config';
import { User } from '../types';
import { decrypt_api_key } from './apiKeyCrypto';
import { resolveAuthToggles } from './authService';

// ---------------------------------------------------------------------------
// Types
// ---------------------------------------------------------------------------

export interface OidcDiscoveryDoc {
  authorization_endpoint: string;
  token_endpoint: string;
  userinfo_endpoint: string;
  jwks_uri?: string;
  issuer?: string;
  _issuer?: string;
}

export interface OidcTokenResponse {
  access_token?: string;
  id_token?: string;
  token_type?: string;
}

export interface OidcUserInfo {
  sub: string;
  email?: string;
  // Standard OIDC claim. Some IdPs send it as the string "true"/"false".
  email_verified?: boolean | string;
  name?: string;
  preferred_username?: string;
  groups?: string[];
  roles?: string[];
  [key: string]: unknown;
}

export interface OidcConfig {
  issuer: string;
  clientId: string;
  clientSecret: string;
  displayName: string;
  discoveryUrl: string | null;
}

// ---------------------------------------------------------------------------
// Constants / TTLs
// ---------------------------------------------------------------------------

const AUTH_CODE_TTL = 60000;          // 1 minute
const AUTH_CODE_CLEANUP = 30000;      // 30 seconds
const STATE_TTL = 5 * 60 * 1000;     // 5 minutes
const STATE_CLEANUP = 60 * 1000;      // 1 minute
const DISCOVERY_TTL = 60 * 60 * 1000; // 1 hour

// ---------------------------------------------------------------------------
// State management – pending OIDC states
// ---------------------------------------------------------------------------

const pendingStates = new Map<string, { createdAt: number; redirectUri: string; inviteToken?: string; codeVerifier: string }>();

setInterval(() => {
  const now = Date.now();
  for (const [state, data] of pendingStates) {
    if (now - data.createdAt > STATE_TTL) pendingStates.delete(state);
  }
}, STATE_CLEANUP);

function base64url(buf: Buffer): string {
  return buf.toString('base64').replace(/\+/g, '-').replace(/\//g, '_').replace(/=+$/, '');
}

// Creates the login state and a matching PKCE pair. The verifier stays server
// side (in pendingStates); the S256 challenge goes to the provider so PKCE-
// required setups (e.g. Pocket ID with PKCE = required) work.
export function createState(redirectUri: string, inviteToken?: string): { state: string; codeChallenge: string } {
  const state = crypto.randomBytes(32).toString('hex');
  const codeVerifier = base64url(crypto.randomBytes(32));
  const codeChallenge = base64url(crypto.createHash('sha256').update(codeVerifier).digest());
  pendingStates.set(state, { createdAt: Date.now(), redirectUri, inviteToken, codeVerifier });
  return { state, codeChallenge };
}

export function consumeState(state: string) {
  const pending = pendingStates.get(state);
  if (!pending) return null;
  pendingStates.delete(state);
  return pending;
}

// ---------------------------------------------------------------------------
// Auth code management – short-lived codes exchanged for JWT
// ---------------------------------------------------------------------------

const authCodes = new Map<string, { token: string; created: number }>();

setInterval(() => {
  const now = Date.now();
  for (const [code, entry] of authCodes) {
    if (now - entry.created > AUTH_CODE_TTL) authCodes.delete(code);
  }
}, AUTH_CODE_CLEANUP);

export function createAuthCode(token: string): string {
  const { v4: uuidv4 } = require('uuid');
  const authCode: string = uuidv4();
  authCodes.set(authCode, { token, created: Date.now() });
  return authCode;
}

export function consumeAuthCode(code: string): { token: string } | { error: string } {
  const entry = authCodes.get(code);
  if (!entry) return { error: 'Invalid or expired code' };
  authCodes.delete(code);
  if (Date.now() - entry.created > AUTH_CODE_TTL) return { error: 'Code expired' };
  return { token: entry.token };
}

// ---------------------------------------------------------------------------
// OIDC configuration (env + DB)
// ---------------------------------------------------------------------------

export function getOidcConfig(): OidcConfig | null {
  const get = (key: string) =>
    (db.prepare("SELECT value FROM app_settings WHERE key = ?").get(key) as { value: string } | undefined)?.value || null;

  const issuer = process.env.OIDC_ISSUER || get('oidc_issuer');
  const clientId = process.env.OIDC_CLIENT_ID || get('oidc_client_id');
  const clientSecret = process.env.OIDC_CLIENT_SECRET || decrypt_api_key(get('oidc_client_secret'));
  const displayName = process.env.OIDC_DISPLAY_NAME || get('oidc_display_name') || 'SSO';
  const discoveryUrl = process.env.OIDC_DISCOVERY_URL || get('oidc_discovery_url') || null;

  if (!issuer || !clientId || !clientSecret) return null;
  return { issuer: issuer.replace(/\/+$/, ''), clientId, clientSecret, displayName, discoveryUrl };
}

// ---------------------------------------------------------------------------
// Discovery document (cached, 1 h TTL)
// ---------------------------------------------------------------------------

let discoveryCache: OidcDiscoveryDoc | null = null;
let discoveryCacheTime = 0;

export async function discover(issuer: string, discoveryUrl?: string | null): Promise<OidcDiscoveryDoc> {
  const url = discoveryUrl || `${issuer}/.well-known/openid-configuration`;
  if (discoveryCache && Date.now() - discoveryCacheTime < DISCOVERY_TTL && discoveryCache._issuer === url) {
    return discoveryCache;
  }
  const res = await fetch(url);
  if (!res.ok) throw new Error('Failed to fetch OIDC discovery document');
  const doc = (await res.json()) as OidcDiscoveryDoc;
  // Validate that the discovery doc's issuer matches the operator-configured one.
  // When no custom discoveryUrl is set, a mismatch signals a MITM or misconfiguration
  // and we reject. When the operator explicitly overrides the discovery URL (e.g.
  // Authentik realm paths), the discovery doc's issuer is the canonical value —
  // trust it and warn rather than blocking login.
  const docIssuer = doc.issuer?.replace(/\/+$/, '') ?? '';
  if (docIssuer && docIssuer !== issuer) {
    if (discoveryUrl) {
      console.warn(
        `[OIDC] Discovery doc issuer "${doc.issuer}" differs from configured OIDC_ISSUER "${issuer}". ` +
        `Using discovery doc issuer for id_token verification (custom OIDC_DISCOVERY_URL is set).`,
      );
    } else {
      throw new Error(`OIDC discovery issuer mismatch: expected "${issuer}", got "${doc.issuer}"`);
    }
  }
  doc._issuer = url;
  discoveryCache = doc;
  discoveryCacheTime = Date.now();
  return doc;
}

// ---------------------------------------------------------------------------
// Role resolution via OIDC claims
// ---------------------------------------------------------------------------

export function resolveOidcRole(userInfo: OidcUserInfo, isFirstUser: boolean): 'admin' | 'user' {
  if (isFirstUser) return 'admin';
  const adminValue = process.env.OIDC_ADMIN_VALUE;
  if (!adminValue) return 'user';
  const claimKey = process.env.OIDC_ADMIN_CLAIM || 'groups';
  const claimData = userInfo[claimKey];
  if (Array.isArray(claimData)) {
    return claimData.some((v) => String(v) === adminValue) ? 'admin' : 'user';
  }
  if (typeof claimData === 'string') {
    return claimData === adminValue ? 'admin' : 'user';
  }
  return 'user';
}

// ---------------------------------------------------------------------------
// Helpers
// ---------------------------------------------------------------------------

export function frontendUrl(path: string): string {
  const base = process.env.NODE_ENV === 'production' ? '' : 'http://localhost:5173';
  return base + path;
}

export function generateToken(user: { id: number }): string {
  // Embed the current password_version so an OIDC-issued session is invalidated
  // by a password change/reset exactly like a password-login session (the auth
  // middleware compares this `pv` against users.password_version).
  const pv = (db.prepare('SELECT password_version FROM users WHERE id = ?').get(user.id) as { password_version?: number } | undefined)?.password_version ?? 0;
  return jwt.sign({ id: user.id, pv }, JWT_SECRET, { expiresIn: SESSION_DURATION_SECONDS, algorithm: 'HS256' });
}

// ---------------------------------------------------------------------------
// Token exchange with OIDC provider
// ---------------------------------------------------------------------------

export async function exchangeCodeForToken(
  doc: OidcDiscoveryDoc,
  code: string,
  redirectUri: string,
  clientId: string,
  clientSecret: string,
  codeVerifier?: string,
): Promise<OidcTokenResponse & { _ok: boolean; _status: number }> {
  const body = new URLSearchParams({
    grant_type: 'authorization_code',
    code,
    redirect_uri: redirectUri,
    client_id: clientId,
    client_secret: clientSecret,
  });
  if (codeVerifier) body.set('code_verifier', codeVerifier);
  const tokenRes = await fetch(doc.token_endpoint, {
    method: 'POST',
    headers: { 'Content-Type': 'application/x-www-form-urlencoded' },
    body,
  });
  const tokenData = (await tokenRes.json()) as OidcTokenResponse;
  return { ...tokenData, _ok: tokenRes.ok, _status: tokenRes.status };
}

// ---------------------------------------------------------------------------
// Fetch userinfo from OIDC provider
// ---------------------------------------------------------------------------

export async function getUserInfo(userinfoEndpoint: string, accessToken: string): Promise<OidcUserInfo> {
  const res = await fetch(userinfoEndpoint, {
    headers: { Authorization: `Bearer ${accessToken}` },
  });
  return (await res.json()) as OidcUserInfo;
}

// ---------------------------------------------------------------------------
// id_token verification (signature + iss + aud + exp)
// ---------------------------------------------------------------------------

// 5 minute JWKS cache — short enough to pick up key rotation within a
// reasonable window, long enough that normal login flow doesn't fetch
// JWKS on every callback.
const JWKS_TTL_MS = 5 * 60 * 1000;
type JwksEntry = { keys: Array<Record<string, unknown>>; fetchedAt: number };
const jwksCache = new Map<string, JwksEntry>();

async function fetchJwks(jwksUri: string): Promise<Array<Record<string, unknown>>> {
  const cached = jwksCache.get(jwksUri);
  if (cached && Date.now() - cached.fetchedAt < JWKS_TTL_MS) return cached.keys;
  const res = await fetch(jwksUri);
  if (!res.ok) throw new Error(`JWKS fetch failed: HTTP ${res.status}`);
  const json = (await res.json()) as { keys?: Array<Record<string, unknown>> };
  const keys = json.keys ?? [];
  jwksCache.set(jwksUri, { keys, fetchedAt: Date.now() });
  return keys;
}

function base64UrlDecode(input: string): Buffer {
  const padded = input.replace(/-/g, '+').replace(/_/g, '/') + '='.repeat((4 - (input.length % 4)) % 4);
  return Buffer.from(padded, 'base64');
}

/**
 * Verify an OIDC id_token end-to-end: signature against the provider's
 * JWKS, issuer match, audience match, and exp/nbf. Does NOT verify a
 * nonce — the server doesn't currently send one in the auth request;
 * when that's added, pass the expected nonce here and check `claims.nonce`.
 *
 * Returning the claims lets callers cross-check `sub` / `email` against
 * the userinfo response. A mismatch would mean the provider's userinfo
 * endpoint is speaking for a different subject than the id_token — a
 * classic IdP-side compromise signal worth refusing login over.
 */
export async function verifyIdToken(
  idToken: string,
  doc: OidcDiscoveryDoc,
  clientId: string,
  expectedIssuer: string,
): Promise<{ ok: true; claims: Record<string, unknown> } | { ok: false; error: string }> {
  if (!doc.jwks_uri) return { ok: false, error: 'no_jwks_uri' };
  const parts = idToken.split('.');
  if (parts.length !== 3) return { ok: false, error: 'malformed_token' };

  let header: { kid?: string; alg?: string };
  try { header = JSON.parse(base64UrlDecode(parts[0]!).toString('utf8')); }
  catch { return { ok: false, error: 'bad_header' }; }

  const alg = header.alg;
  if (!alg || !/^(RS256|RS384|RS512|ES256|ES384|ES512|PS256|PS384|PS512)$/.test(alg)) {
    return { ok: false, error: 'unsupported_alg' };
  }

  let keys: Array<Record<string, unknown>>;
  try { keys = await fetchJwks(doc.jwks_uri); }
  catch (e) { return { ok: false, error: 'jwks_fetch_failed' }; }

  // When the token carries a `kid`, refuse to fall back to any other
  // key in the JWKS — a mismatch means the token was signed with a key
  // the provider no longer publishes, and we should reject rather than
  // mask the failure by trying another key.
  const jwk = header.kid
    ? keys.find((k) => k['kid'] === header.kid)
    : keys[0];
  if (!jwk) return { ok: false, error: 'no_matching_key' };

  let publicKey;
  try {
    // Node 16+ understands JWK directly; no PEM conversion library needed.
    // Node's crypto accepts a JWK object directly as `{ key, format: 'jwk' }`.
    // The type signature isn't strict on our TS config so we cast through any.
    publicKey = crypto.createPublicKey({ key: jwk as any, format: 'jwk' });
  } catch {
    return { ok: false, error: 'key_import_failed' };
  }

  let claims: Record<string, unknown>;
  try {
    const verified = jwt.verify(idToken, publicKey, {
      algorithms: [alg as jwt.Algorithm],
      audience: clientId,
    });
    claims = typeof verified === 'string' ? {} : (verified as Record<string, unknown>);
  } catch (err) {
    const msg = err instanceof Error ? err.message : 'verify_failed';
    return { ok: false, error: `signature_or_claim_mismatch: ${msg}` };
  }

  // Normalize trailing slash before issuer comparison — some IdPs (e.g. Authentik)
  // include a trailing slash in the id_token iss claim.
  const tokenIssuer = typeof claims['iss'] === 'string' ? claims['iss'].replace(/\/+$/, '') : '';
  if (tokenIssuer !== expectedIssuer) {
    return { ok: false, error: `signature_or_claim_mismatch: jwt issuer invalid. expected: ${expectedIssuer}` };
  }

  return { ok: true, claims };
}

// ---------------------------------------------------------------------------
// Find or create user by OIDC sub / email
// ---------------------------------------------------------------------------

export function findOrCreateUser(
  userInfo: OidcUserInfo,
  config: OidcConfig,
  inviteToken?: string,
): { user: User } | { error: string } {
  const email = userInfo.email!.trim().toLowerCase();
  const name = userInfo.name || userInfo.preferred_username || email.split('@')[0];
  const sub = userInfo.sub;

  // Try to find existing user by sub, then by email
  let user = db.prepare('SELECT * FROM users WHERE oidc_sub = ? AND oidc_issuer = ?').get(sub, config.issuer) as User | undefined;
  if (!user) {
    user = db.prepare('SELECT * FROM users WHERE LOWER(email) = ?').get(email) as User | undefined;
  }

  if (user) {
    // Reaching here without an oidc_sub means we matched an existing local
    // account by email. Only auto-link the OIDC identity when the IdP asserts
    // the email is verified; an unverified email must not auto-link.
    if (!user.oidc_sub) {
      const emailVerified = userInfo.email_verified === true || userInfo.email_verified === 'true';
      if (!emailVerified) {
        return { error: 'email_not_verified' };
      }
      db.prepare('UPDATE users SET oidc_sub = ?, oidc_issuer = ? WHERE id = ?').run(sub, config.issuer, user.id);
    }
    // Update role based on OIDC claims on every login (if claim mapping is configured)
    if (process.env.OIDC_ADMIN_VALUE) {
      const newRole = resolveOidcRole(userInfo, false);
      if (user.role !== newRole) {
        db.prepare('UPDATE users SET role = ? WHERE id = ?').run(newRole, user.id);
        user = { ...user, role: newRole } as User;
      }
    }
    return { user };
  }

  // --- New user registration ---
  const userCount = (db.prepare('SELECT COUNT(*) as count FROM users').get() as { count: number }).count;
  const isFirstUser = userCount === 0;

  let validInvite: any = null;
  if (inviteToken) {
    validInvite = db.prepare('SELECT * FROM invite_tokens WHERE token = ?').get(inviteToken);
    if (validInvite) {
      if (validInvite.max_uses > 0 && validInvite.used_count >= validInvite.max_uses) validInvite = null;
      if (validInvite?.expires_at && new Date(validInvite.expires_at) < new Date()) validInvite = null;
    }
  }

  if (!isFirstUser && !validInvite) {
    const { oidc_registration } = resolveAuthToggles();
    if (!oidc_registration) {
      return { error: 'registration_disabled' };
    }
  }

  const role = resolveOidcRole(userInfo, isFirstUser);
  const randomPass = crypto.randomBytes(32).toString('hex');
  const bcrypt = require('bcryptjs');
  const hash = bcrypt.hashSync(randomPass, 10);

  // Username: sanitize and avoid collisions
  let username = name.replace(/[^a-zA-Z0-9_-]/g, '').substring(0, 30) || 'user';
  const existing = db.prepare('SELECT id FROM users WHERE LOWER(username) = LOWER(?)').get(username);
  if (existing) username = `${username}_${Date.now() % 10000}`;

  // Atomic registration: if an invite was presented, the increment IS
  // the capacity check — UPDATE matches zero rows the moment another
  // concurrent callback wins the last slot, and the transaction aborts
  // the user INSERT. Without this, two parallel OIDC callbacks could
  // both pass the earlier SELECT-based check and each create a user.
  const inviteRaceError = new Error('invite_exhausted');
  try {
    const createUser = db.transaction(() => {
      if (validInvite) {
        const updated = db.prepare(
          'UPDATE invite_tokens SET used_count = used_count + 1 WHERE id = ? AND (max_uses = 0 OR used_count < max_uses)',
        ).run(validInvite.id);
        if (updated.changes === 0) throw inviteRaceError;
      }
      return db.prepare(
        'INSERT INTO users (username, email, password_hash, role, oidc_sub, oidc_issuer, first_seen_version, login_count) VALUES (?, ?, ?, ?, ?, ?, ?, 0)',
      ).run(username, email, hash, role, sub, config.issuer, process.env.APP_VERSION || '0.0.0');
    });
    const result = createUser() as { lastInsertRowid: number | bigint };
    user = { id: Number(result.lastInsertRowid), username, email, role } as User;
    return { user };
  } catch (err) {
    if (err === inviteRaceError) {
      console.warn(`[OIDC] Invite token ${inviteToken?.slice(0, 8)}... exhausted — concurrent callback won the last slot`);
      return { error: 'registration_disabled' };
    }
    throw err;
  }
}

// ---------------------------------------------------------------------------
// Update last_login timestamp
// ---------------------------------------------------------------------------

export function touchLastLogin(userId: number): void {
  db.prepare('UPDATE users SET last_login = CURRENT_TIMESTAMP, login_count = login_count + 1 WHERE id = ?').run(userId);
}