/**
 * OAuth/OIDC Authentication Strategy
 * Handles OAuth 2.0 and OpenID Connect flows
 */

import type { AuthProvider } from '../../../models/auth.provider.ts';
import type { CryptoService } from '../../crypto.service.ts';
import type {
  IExternalUserInfo,
  IConnectionTestResult,
} from '../../../interfaces/auth.interfaces.ts';
import type { IAuthStrategy, IOAuthCallbackData } from './auth.strategy.interface.ts';

interface ITokenResponse {
  access_token: string;
  token_type: string;
  expires_in?: number;
  refresh_token?: string;
  id_token?: string;
  scope?: string;
}

interface IOIDCDiscovery {
  issuer: string;
  authorization_endpoint: string;
  token_endpoint: string;
  userinfo_endpoint?: string;
  jwks_uri?: string;
  scopes_supported?: string[];
}

export class OAuthStrategy implements IAuthStrategy {
  private discoveryCache: IOIDCDiscovery | null = null;

  constructor(
    private provider: AuthProvider,
    private cryptoService: CryptoService
  ) {}

  /**
   * Get the authorization URL for initiating OAuth flow
   */
  public async getAuthorizationUrl(state: string, nonce?: string): Promise<string> {
    const config = this.provider.oauthConfig;
    if (!config) {
      throw new Error('OAuth config not found');
    }

    // Get authorization URL from config or discovery
    let authorizationUrl = config.authorizationUrl;
    if (!authorizationUrl) {
      const discovery = await this.getDiscovery();
      authorizationUrl = discovery.authorization_endpoint;
    }

    const params = new URLSearchParams({
      client_id: config.clientId,
      redirect_uri: config.callbackUrl,
      response_type: 'code',
      scope: config.scopes.join(' '),
      state,
    });

    // Add nonce for OIDC
    if (nonce) {
      params.set('nonce', nonce);
    }

    return `${authorizationUrl}?${params.toString()}`;
  }

  /**
   * Handle OAuth callback - exchange code for tokens and get user info
   */
  public async handleCallback(data: IOAuthCallbackData): Promise<IExternalUserInfo> {
    if (data.error) {
      throw new Error(`OAuth error: ${data.error} - ${data.errorDescription || ''}`);
    }

    const config = this.provider.oauthConfig;
    if (!config) {
      throw new Error('OAuth config not found');
    }

    // Exchange code for tokens
    const tokens = await this.exchangeCodeForTokens(data.code);

    // Get user info
    const userInfo = await this.fetchUserInfo(tokens.access_token);

    // Map attributes according to provider config
    return this.mapAttributes(userInfo);
  }

  /**
   * Test connection by fetching OIDC discovery document
   */
  public async testConnection(): Promise<IConnectionTestResult> {
    const start = Date.now();
    const config = this.provider.oauthConfig;

    if (!config) {
      return {
        success: false,
        latencyMs: Date.now() - start,
        error: 'OAuth config not found',
      };
    }

    try {
      const discovery = await this.getDiscovery();

      return {
        success: true,
        latencyMs: Date.now() - start,
        serverInfo: {
          issuer: discovery.issuer,
          scopes_supported: discovery.scopes_supported,
          has_userinfo: !!discovery.userinfo_endpoint,
        },
      };
    } catch (error) {
      return {
        success: false,
        latencyMs: Date.now() - start,
        error: error instanceof Error ? error.message : String(error),
      };
    }
  }

  /**
   * Exchange authorization code for tokens
   */
  private async exchangeCodeForTokens(code: string): Promise<ITokenResponse> {
    const config = this.provider.oauthConfig!;

    // Get token URL from config or discovery
    let tokenUrl = config.tokenUrl;
    if (!tokenUrl) {
      const discovery = await this.getDiscovery();
      tokenUrl = discovery.token_endpoint;
    }

    // Decrypt client secret
    const clientSecret = await this.cryptoService.decrypt(config.clientSecretEncrypted);

    const response = await fetch(tokenUrl, {
      method: 'POST',
      headers: {
        'Content-Type': 'application/x-www-form-urlencoded',
        Accept: 'application/json',
      },
      body: new URLSearchParams({
        grant_type: 'authorization_code',
        code,
        redirect_uri: config.callbackUrl,
        client_id: config.clientId,
        client_secret: clientSecret,
      }),
    });

    if (!response.ok) {
      const errorText = await response.text();
      throw new Error(`Token exchange failed: ${response.status} - ${errorText}`);
    }

    return await response.json();
  }

  /**
   * Fetch user info from the provider
   */
  private async fetchUserInfo(accessToken: string): Promise<Record<string, unknown>> {
    const config = this.provider.oauthConfig!;

    // Get userinfo URL from config or discovery
    let userInfoUrl = config.userInfoUrl;
    if (!userInfoUrl) {
      const discovery = await this.getDiscovery();
      userInfoUrl = discovery.userinfo_endpoint;
    }

    if (!userInfoUrl) {
      throw new Error('UserInfo endpoint not found');
    }

    const response = await fetch(userInfoUrl, {
      headers: {
        Authorization: `Bearer ${accessToken}`,
        Accept: 'application/json',
      },
    });

    if (!response.ok) {
      const errorText = await response.text();
      throw new Error(`UserInfo fetch failed: ${response.status} - ${errorText}`);
    }

    return await response.json();
  }

  /**
   * Get OIDC discovery document
   */
  private async getDiscovery(): Promise<IOIDCDiscovery> {
    if (this.discoveryCache) {
      return this.discoveryCache;
    }

    const config = this.provider.oauthConfig!;
    const discoveryUrl = `${config.issuer}/.well-known/openid-configuration`;

    const response = await fetch(discoveryUrl, {
      headers: { Accept: 'application/json' },
    });

    if (!response.ok) {
      throw new Error(`OIDC discovery failed: ${response.status}`);
    }

    this.discoveryCache = await response.json();
    return this.discoveryCache!;
  }

  /**
   * Map provider attributes to standard user info
   */
  private mapAttributes(rawInfo: Record<string, unknown>): IExternalUserInfo {
    const mapping = this.provider.attributeMapping;

    // Get external ID (sub for OIDC, or id for OAuth2)
    const externalId = String(rawInfo.sub || rawInfo.id || '');
    if (!externalId) {
      throw new Error('External ID not found in user info');
    }

    // Get email
    const email = rawInfo[mapping.email];
    if (!email || typeof email !== 'string') {
      throw new Error('Email not found in user info');
    }

    return {
      externalId,
      email,
      username: rawInfo[mapping.username]
        ? String(rawInfo[mapping.username])
        : undefined,
      displayName: rawInfo[mapping.displayName]
        ? String(rawInfo[mapping.displayName])
        : undefined,
      avatarUrl: mapping.avatarUrl && rawInfo[mapping.avatarUrl]
        ? String(rawInfo[mapping.avatarUrl])
        : (rawInfo.picture ? String(rawInfo.picture) : undefined),
      groups: mapping.groups && rawInfo[mapping.groups]
        ? (Array.isArray(rawInfo[mapping.groups])
            ? (rawInfo[mapping.groups] as string[])
            : [String(rawInfo[mapping.groups])])
        : undefined,
      rawAttributes: rawInfo,
    };
  }
}