import express, { Request, Response } from 'express';
import { authenticate, requireCookieAuth, optionalAuth } from '../middleware/auth';
import { AuthRequest, OptionalAuthRequest } from '../types';
import { isAddonEnabled } from '../services/adminService';
import { ALL_SCOPES } from '../mcp/scopes';
import { ADDON_IDS } from '../addons';
import {
  validateAuthorizeRequest,
  createAuthCode,
  consumeAuthCode,
  saveConsent,
  issueTokens,
  issueClientCredentialsToken,
  refreshTokens,
  revokeToken,
  verifyPKCE,
  authenticateClient,
  listOAuthClients,
  createOAuthClient,
  deleteOAuthClient,
  rotateOAuthClientSecret,
  listOAuthSessions,
  revokeSession,
  getUserByAccessToken,
  AuthorizeParams,
} from '../services/oauthService';
import { writeAudit, getClientIp, logWarn } from '../services/auditLog';
import { getMcpSafeUrl } from '../services/notifications';

// ---------------------------------------------------------------------------
// Minimal in-file rate limiter (same pattern as auth.ts)
// ---------------------------------------------------------------------------

interface RateEntry { count: number; first: number; }

function makeRateLimiter(maxAttempts: number, windowMs: number, keyFn: (req: Request) => string) {
  const store = new Map<string, RateEntry>();
  setInterval(() => {
    const now = Date.now();
    for (const [k, r] of store) if (now - r.first >= windowMs) store.delete(k);
  }, windowMs).unref();

  return (req: Request, res: Response, next: () => void): void => {
    const key = keyFn(req);
    const now = Date.now();
    const record = store.get(key);
    if (record && record.count >= maxAttempts && now - record.first < windowMs) {
      res.status(429).json({ error: 'too_many_requests', error_description: 'Too many attempts. Please try again later.' });
      return;
    }
    if (!record || now - record.first >= windowMs) {
      store.set(key, { count: 1, first: now });
    } else {
      record.count++;
    }
    next();
  };
}

const tokenLimiter    = makeRateLimiter(30, 60_000, (req) => `${req.ip}|${req.body?.client_id ?? ''}`);
const validateLimiter = makeRateLimiter(30, 60_000, (req) => req.ip ?? 'unknown');
const revokeLimiter   = makeRateLimiter(10, 60_000, (req) => req.ip ?? 'unknown');

// ---------------------------------------------------------------------------
// Public router: /oauth/token and /oauth/revoke
// (/.well-known and /oauth/register are now handled by SDK in app.ts)
// ---------------------------------------------------------------------------

export const oauthPublicRouter = express.Router();

// Token endpoint — handles authorization_code and refresh_token grants
oauthPublicRouter.post('/oauth/token', tokenLimiter, (req: Request, res: Response) => {
  if (!isAddonEnabled(ADDON_IDS.MCP)) return res.status(404).end();

  // M1: RFC 6749 §5.1 — token responses must not be cached
  res.set('Cache-Control', 'no-store');
  res.set('Pragma', 'no-cache');

  // Accept both JSON and application/x-www-form-urlencoded
  const body: Record<string, string> = typeof req.body === 'object' ? req.body : {};
  const { grant_type, code, redirect_uri, client_id, client_secret, code_verifier, refresh_token, resource } = body;
  const ip = getClientIp(req);

  if (!client_id) {
    return res.status(401).json({ error: 'invalid_client', error_description: 'client_id is required' });
  }

  // ---- authorization_code grant ----
  if (grant_type === 'authorization_code') {
    if (!code || !redirect_uri || !code_verifier) {
      return res.status(400).json({ error: 'invalid_request', error_description: 'code, redirect_uri, and code_verifier are required' });
    }

    const pending = consumeAuthCode(code);

    // H5: collapse all invalid_grant cases to one message; log specifics server-side
    if (!pending) {
      writeAudit({ userId: null, action: 'oauth.token.grant_failed', details: { client_id, reason: 'code_invalid_or_expired' }, ip });
      return res.status(400).json({ error: 'invalid_grant', error_description: 'Authorization grant is invalid.' });
    }

    if (pending.clientId !== client_id) {
      writeAudit({ userId: pending.userId, action: 'oauth.token.grant_failed', details: { client_id, reason: 'client_id_mismatch' }, ip });
      return res.status(400).json({ error: 'invalid_grant', error_description: 'Authorization grant is invalid.' });
    }

    if (pending.redirectUri !== redirect_uri) {
      writeAudit({ userId: pending.userId, action: 'oauth.token.grant_failed', details: { client_id, reason: 'redirect_uri_mismatch' }, ip });
      return res.status(400).json({ error: 'invalid_grant', error_description: 'Authorization grant is invalid.' });
    }

    // RFC 8707: if the auth code was bound to a resource, the token request must present the same value
    if (pending.resource && resource && pending.resource !== resource.replace(/\/+$/, '')) {
      writeAudit({ userId: pending.userId, action: 'oauth.token.grant_failed', details: { client_id, reason: 'resource_mismatch' }, ip });
      return res.status(400).json({ error: 'invalid_grant', error_description: 'Authorization grant is invalid.' });
    }

    // Verify client secret
    if (!authenticateClient(client_id, client_secret)) {
      logWarn(`[OAuth] Invalid client credentials for client_id=${client_id} ip=${ip ?? '-'}`);
      writeAudit({ userId: pending.userId, action: 'oauth.token.client_auth_failed', details: { client_id }, ip });
      return res.status(401).json({ error: 'invalid_client', error_description: 'Invalid client credentials' });
    }

    // Verify PKCE
    if (!verifyPKCE(code_verifier, pending.codeChallenge)) {
      writeAudit({ userId: pending.userId, action: 'oauth.token.grant_failed', details: { client_id, reason: 'pkce_failed' }, ip });
      return res.status(400).json({ error: 'invalid_grant', error_description: 'Authorization grant is invalid.' });
    }

    const tokens = issueTokens(client_id, pending.userId, pending.scopes, null, pending.resource ?? null);
    writeAudit({ userId: pending.userId, action: 'oauth.token.issue', details: { client_id, scopes: pending.scopes, audience: pending.resource ?? null }, ip });
    return res.json(tokens);
  }

  // ---- refresh_token grant ----
  if (grant_type === 'refresh_token') {
    if (!refresh_token) {
      return res.status(400).json({ error: 'invalid_request', error_description: 'refresh_token is required' });
    }

    const result = refreshTokens(refresh_token, client_id, client_secret, ip);
    if (result.error) {
      if (result.error === 'invalid_client') {
        logWarn(`[OAuth] Invalid client credentials on refresh for client_id=${client_id} ip=${ip ?? '-'}`);
      }
      return res.status(result.status || 400).json({
        error: result.error,
        error_description: result.error === 'invalid_client' ? 'Invalid client credentials' : 'Refresh token is invalid or expired',
      });
    }

    return res.json(result.tokens);
  }

  // ---- client_credentials grant ----
  if (grant_type === 'client_credentials') {
    if (!client_secret) {
      return res.status(401).json({ error: 'invalid_client', error_description: 'client_secret is required for client_credentials grant' });
    }

    const client = authenticateClient(client_id, client_secret);
    if (!client) {
      logWarn(`[OAuth] Invalid client credentials for client_id=${client_id} ip=${ip ?? '-'}`);
      writeAudit({ userId: null, action: 'oauth.token.client_auth_failed', details: { client_id }, ip });
      return res.status(401).json({ error: 'invalid_client', error_description: 'Invalid client credentials' });
    }

    // Public clients and DCR-anonymous clients are ineligible for client_credentials.
    if (client.is_public || !client.allows_client_credentials || client.user_id == null) {
      writeAudit({ userId: client.user_id ?? null, action: 'oauth.token.grant_failed', details: { client_id, reason: 'unauthorized_client' }, ip });
      return res.status(400).json({ error: 'unauthorized_client', error_description: 'This client is not authorized for the client_credentials grant' });
    }

    // Scope: use requested subset or fall back to all allowed scopes.
    const allowedScopes: string[] = JSON.parse(client.allowed_scopes);
    let grantedScopes: string[];
    if (body.scope) {
      const requested = body.scope.split(' ').filter(Boolean);
      const invalid = requested.filter(s => !allowedScopes.includes(s));
      if (invalid.length > 0) {
        return res.status(400).json({ error: 'invalid_scope', error_description: `Scopes not allowed for this client: ${invalid.join(', ')}` });
      }
      grantedScopes = requested;
    } else {
      grantedScopes = allowedScopes;
    }

    // Audience: honour RFC 8707 resource param; default to the MCP endpoint so the
    // token passes audience binding in mcp/index.ts without extra configuration.
    const audience = resource ? resource.replace(/\/+$/, '') : `${getMcpSafeUrl().replace(/\/+$/, '')}/mcp`;

    const tokens = issueClientCredentialsToken(client_id, client.user_id, grantedScopes, audience);
    writeAudit({ userId: client.user_id, action: 'oauth.token.issue', details: { client_id, scopes: grantedScopes, audience, grant: 'client_credentials' }, ip });
    return res.json(tokens);
  }

  return res.status(400).json({ error: 'unsupported_grant_type', error_description: `Unsupported grant_type: ${grant_type}` });
});

// OIDC UserInfo endpoint (RFC 9068 / OpenID Connect Core §5.3)
// ChatGPT hits this after OAuth to fetch the authenticated user's email for domain claiming.
oauthPublicRouter.get('/oauth/userinfo', (req: Request, res: Response) => {
  if (!isAddonEnabled(ADDON_IDS.MCP)) return res.status(404).end();
  const auth = req.headers['authorization'];
  if (!auth || !auth.toLowerCase().startsWith('bearer ')) {
    res.set('WWW-Authenticate', 'Bearer realm="TREK MCP"');
    return res.status(401).json({ error: 'invalid_token' });
  }
  const token = auth.slice(7);
  const info = getUserByAccessToken(token);
  if (!info) {
    res.set('WWW-Authenticate', 'Bearer realm="TREK MCP", error="invalid_token"');
    return res.status(401).json({ error: 'invalid_token' });
  }
  return res.json({
    sub:            String(info.user.id),
    email:          info.user.email,
    email_verified: true,
    preferred_username: info.user.username,
  });
});

// Token revocation endpoint (RFC 7009)
oauthPublicRouter.post('/oauth/revoke', revokeLimiter, (req: Request, res: Response) => {
  if (!isAddonEnabled(ADDON_IDS.MCP)) return res.status(404).end();
  const body: Record<string, string> = typeof req.body === 'object' ? req.body : {};
  const { token, client_id, client_secret } = body;
  const ip = getClientIp(req);

  if (!token || !client_id) {
    return res.status(400).json({ error: 'invalid_request', error_description: 'token and client_id are required' });
  }

  if (!authenticateClient(client_id, client_secret)) {
    logWarn(`[OAuth] Invalid client credentials on revoke for client_id=${client_id} ip=${ip ?? '-'}`);
    writeAudit({ userId: null, action: 'oauth.token.client_auth_failed', details: { client_id, endpoint: 'revoke' }, ip });
    return res.status(401).json({ error: 'invalid_client', error_description: 'Invalid client credentials' });
  }

  revokeToken(token, client_id, undefined, ip);
  // RFC 7009 §2.2: always respond 200 even if token was already revoked or not found
  return res.status(200).json({});
});

// ---------------------------------------------------------------------------
// API router: /api/oauth/* — authenticated endpoints used by the SPA
// ---------------------------------------------------------------------------

export const oauthApiRouter = express.Router();

// SPA calls this on page load to validate OAuth params before rendering consent UI
oauthApiRouter.get('/authorize/validate', validateLimiter, optionalAuth, (req: Request, res: Response) => {
  // M2 / H3: gate by addon; 404 prevents feature fingerprinting for anonymous callers
  if (!isAddonEnabled(ADDON_IDS.MCP)) return res.status(404).end();

  const params = req.query as Partial<AuthorizeParams>;
  const userId = (req as OptionalAuthRequest).user?.id ?? null;

  const result = validateAuthorizeRequest(
      {
        response_type:          params.response_type || '',
        client_id:              params.client_id || '',
        redirect_uri:           params.redirect_uri || '',
        scope:                  params.scope || '',
        state:                  params.state,
        code_challenge:         params.code_challenge || '',
        code_challenge_method:  params.code_challenge_method || '',
        resource:               typeof params.resource === 'string' ? params.resource : undefined,
      },
      userId,
  );

  // H3: when caller is unauthenticated, strip client name / allowed_scopes from the response
  // (validateAuthorizeRequest already does this, but be explicit here)
  if (userId === null && result.valid) {
    return res.json({ valid: result.valid, loginRequired: true });
  }

  // For unauthenticated error cases return a generic error to prevent oracle enumeration
  if (userId === null && !result.valid) {
    return res.json({ valid: false, error: 'invalid_request', error_description: 'Invalid authorization request' });
  }

  return res.json(result);
});

// User submits consent (approve or deny) — requires cookie-only auth (M7)
oauthApiRouter.post('/authorize', requireCookieAuth, (req: Request, res: Response) => {
  const { user } = req as AuthRequest;
  const {
    client_id, redirect_uri, scope, state,
    code_challenge, code_challenge_method, approved, resource,
  } = req.body as {
    client_id: string;
    redirect_uri: string;
    scope: string;
    state?: string;
    code_challenge: string;
    code_challenge_method: string;
    approved: boolean;
    resource?: string;
  };
  const ip = getClientIp(req);

  if (!isAddonEnabled(ADDON_IDS.MCP)) {
    return res.status(403).json({ error: 'MCP is not enabled' });
  }

  if (!approved) {
    // User denied — redirect with error
    const url = new URL(redirect_uri);
    url.searchParams.set('error', 'access_denied');
    url.searchParams.set('error_description', 'User denied the authorization request');
    if (state) url.searchParams.set('state', state);
    return res.json({ redirect: url.toString() });
  }

  // Re-validate all params (server-side re-check after user action)
  const params: AuthorizeParams = {
    response_type: 'code',
    client_id,
    redirect_uri,
    scope,
    state,
    code_challenge,
    code_challenge_method,
    resource,
  };

  const validation = validateAuthorizeRequest(params, user.id);
  if (!validation.valid) {
    return res.status(400).json({ error: validation.error, error_description: validation.error_description });
  }

  const scopes = validation.scopes!;

  // Store consent (union with any existing scopes)
  saveConsent(client_id, user.id, scopes, ip);

  // Issue auth code
  const code = createAuthCode({
    clientId: client_id,
    userId: user.id,
    redirectUri: redirect_uri,
    scopes,
    resource: validation.resource ?? null,
    codeChallenge: code_challenge,
    codeChallengeMethod: 'S256',
  });

  if (!code) {
    return res.status(503).json({ error: 'server_error', error_description: 'Authorization server is temporarily unavailable' });
  }

  const url = new URL(redirect_uri);
  url.searchParams.set('code', code);
  if (state) url.searchParams.set('state', state);

  return res.json({ redirect: url.toString() });
});

// ---- OAuth client CRUD ----

oauthApiRouter.get('/clients', authenticate, (req: Request, res: Response) => {
  if (!isAddonEnabled(ADDON_IDS.MCP)) return res.status(403).json({ error: 'MCP is not enabled' });
  const { user } = req as AuthRequest;
  return res.json({ clients: listOAuthClients(user.id) });
});

oauthApiRouter.post('/clients', requireCookieAuth, (req: Request, res: Response) => {
  if (!isAddonEnabled(ADDON_IDS.MCP)) return res.status(403).json({ error: 'MCP is not enabled' });
  const { user } = req as AuthRequest;
  const { name, redirect_uris, allowed_scopes, allows_client_credentials } = req.body as {
    name: string;
    redirect_uris?: string[];
    allowed_scopes: string[];
    allows_client_credentials?: boolean;
  };

  const result = createOAuthClient(user.id, name, redirect_uris ?? [], allowed_scopes, getClientIp(req), { allowsClientCredentials: allows_client_credentials });
  if (result.error) return res.status(result.status || 400).json({ error: result.error });
  return res.status(201).json(result);
});

oauthApiRouter.post('/clients/:id/rotate', requireCookieAuth, (req: Request, res: Response) => {
  if (!isAddonEnabled(ADDON_IDS.MCP)) return res.status(403).json({ error: 'MCP is not enabled' });
  const { user } = req as AuthRequest;
  const result = rotateOAuthClientSecret(user.id, req.params.id, getClientIp(req));
  if (result.error) return res.status(result.status || 400).json({ error: result.error });
  return res.json({ client_secret: result.client_secret });
});

oauthApiRouter.delete('/clients/:id', requireCookieAuth, (req: Request, res: Response) => {
  if (!isAddonEnabled(ADDON_IDS.MCP)) return res.status(403).json({ error: 'MCP is not enabled' });
  const { user } = req as AuthRequest;
  const result = deleteOAuthClient(user.id, req.params.id, getClientIp(req));
  if (result.error) return res.status(result.status || 400).json({ error: result.error });
  return res.json({ success: true });
});

// ---- Active OAuth sessions ----

oauthApiRouter.get('/sessions', authenticate, (req: Request, res: Response) => {
  if (!isAddonEnabled(ADDON_IDS.MCP)) return res.status(403).json({ error: 'MCP is not enabled' });
  const { user } = req as AuthRequest;
  return res.json({ sessions: listOAuthSessions(user.id) });
});

oauthApiRouter.delete('/sessions/:id', requireCookieAuth, (req: Request, res: Response) => {
  if (!isAddonEnabled(ADDON_IDS.MCP)) return res.status(403).json({ error: 'MCP is not enabled' });
  const { user } = req as AuthRequest;
  const result = revokeSession(user.id, Number(req.params.id), getClientIp(req));
  if (result.error) return res.status(result.status || 400).json({ error: result.error });
  return res.json({ success: true });
});