import {
  ForbiddenException,
  Inject,
  Injectable,
  Logger,
  ServiceUnavailableException,
} from '@nestjs/common';
import {
  IdentityProvider,
  InvalidAccessTokenError,
  InvalidCredentialsError,
} from '@task-stream/api/identity/application';
import {
  AuthorizationConfig,
  TokenGrant,
  TokenSet,
  User,
  UserFactory,
} from '@task-stream/api/identity/domain';
import { PIREON_CONFIG, PireonConfig } from './pireon.config';

/** User resource as documented in https://oauth.pireon.dev/docs?api-docs.json */
interface PireonUser {
  id: number;
  name: string;
  email: string;
  is_active: boolean;
  roles?: string[];
  app_roles?: string[];
}

interface OAuthClient {
  id: string;
  secret: string | undefined;
}

/** Driven adapter for the Pireon OAuth2 identity server (Laravel Passport). */
@Injectable()
export class PireonIdentityProvider extends IdentityProvider {
  private readonly logger = new Logger(PireonIdentityProvider.name);

  constructor(
    @Inject(PIREON_CONFIG) private readonly config: PireonConfig,
    private readonly users: UserFactory,
  ) {
    super();
  }

  async whoAmI(accessToken: string): Promise<User> {
    const response = await this.request('/api/user', accessToken);
    if (response.status === 401 || response.status === 403) {
      throw new InvalidAccessTokenError();
    }
    this.assertOk(response, 'GET /api/user');
    return this.toUser((await response.json()) as PireonUser);
  }

  async findUser(id: string, accessToken: string): Promise<User | null> {
    if (!/^\d+$/.test(id)) return null;
    const response = await this.request(`/api/users/${id}`, accessToken);
    if ([401, 403, 404].includes(response.status)) return null;
    this.assertOk(response, `GET /api/users/${id}`);
    return this.toUser((await response.json()) as PireonUser);
  }

  async listUsers(accessToken: string): Promise<User[]> {
    const response = await this.request('/api/users', accessToken);
    if (response.status === 401 || response.status === 403) return [];
    this.assertOk(response, 'GET /api/users');
    const body = (await response.json()) as
      | PireonUser[]
      | { data: PireonUser[] };
    const users = Array.isArray(body) ? body : body.data;
    return users.map((u) => this.toUser(u));
  }

  async issueToken(grant: TokenGrant): Promise<TokenSet> {
    const clients = this.clientsFor(grant);
    // A refresh token only works with the client that issued it, and we don't
    // know which one that was: try each until one accepts it.
    let rejected: InvalidCredentialsError | undefined;
    for (const client of clients) {
      try {
        return await this.requestToken(client, grant);
      } catch (error) {
        if (
          grant.type !== 'refresh_token' ||
          !(error instanceof InvalidCredentialsError)
        )
          throw error;
        rejected = error;
      }
    }
    throw rejected ?? new InvalidCredentialsError();
  }

  /**
   * Pireon clients allow a single grant type: authorization_code uses
   * PIREON_CLIENT_ID, password PIREON_PASSWORD_CLIENT_ID (or the former).
   */
  private clientsFor(grant: TokenGrant): OAuthClient[] {
    const { clientId, clientSecret, passwordClientId, passwordClientSecret } =
      this.config;
    const code: OAuthClient | undefined = clientId
      ? { id: clientId, secret: clientSecret }
      : undefined;
    const password: OAuthClient | undefined = passwordClientId
      ? { id: passwordClientId, secret: passwordClientSecret }
      : code;

    switch (grant.type) {
      case 'authorization_code':
        if (!code)
          throw new ServiceUnavailableException(
            'Sign-in with Pireon is not configured (PIREON_CLIENT_ID)',
          );
        return [code];
      case 'password':
        if (!this.config.passwordGrant)
          throw new ForbiddenException(
            'Email and password sign-in is disabled',
          );
        if (!password)
          throw new ServiceUnavailableException(
            'Email and password sign-in is not configured (PIREON_PASSWORD_CLIENT_ID)',
          );
        return [password];
      case 'refresh_token': {
        const candidates = [password, code].filter(
          (client): client is OAuthClient => !!client,
        );
        if (!candidates.length)
          throw new ServiceUnavailableException(
            'Sign-in is not configured (PIREON_CLIENT_ID)',
          );
        return candidates.filter(
          (client, i) => candidates.findIndex((c) => c.id === client.id) === i,
        );
      }
    }
  }

  private async requestToken(
    client: OAuthClient,
    grant: TokenGrant,
  ): Promise<TokenSet> {
    const { scopes } = this.config;
    const body = new URLSearchParams({ client_id: client.id });
    if (client.secret) body.set('client_secret', client.secret);
    switch (grant.type) {
      case 'authorization_code':
        body.set('grant_type', 'authorization_code');
        body.set('code', grant.code);
        body.set('code_verifier', grant.codeVerifier);
        body.set('redirect_uri', grant.redirectUri);
        break;
      case 'password':
        body.set('grant_type', 'password');
        body.set('username', grant.username);
        body.set('password', grant.password);
        body.set('scope', scopes.join(' '));
        break;
      case 'refresh_token':
        body.set('grant_type', 'refresh_token');
        body.set('refresh_token', grant.refreshToken);
        break;
    }

    let response: Response;
    try {
      response = await fetch(new URL('/oauth/token', this.config.baseUrl), {
        method: 'POST',
        headers: {
          'Content-Type': 'application/x-www-form-urlencoded',
          Accept: 'application/json',
        },
        body,
        signal: AbortSignal.timeout(this.config.requestTimeoutMs),
      });
    } catch (error) {
      this.logger.error(
        `Pireon unreachable (/oauth/token): ${(error as Error).message}`,
      );
      throw new ServiceUnavailableException('Identity server unavailable');
    }
    if (response.status === 400 || response.status === 401) {
      // OAuth2 error (RFC 6749 §5.2). Passport puts the useful part in `hint`
      // (which parameter was wrong), so keep it in the message and the log.
      const error = (await response.json().catch(() => ({}))) as {
        error?: string;
        error_description?: string;
        hint?: string;
        message?: string;
      };
      const description =
        error.error_description ?? error.message ?? 'Invalid credentials';
      this.logger.warn(
        `Pireon rejected ${grant.type} for client ${client.id}: ` +
          `${error.error ?? response.status} — ${description}` +
          (error.hint ? ` (hint: ${error.hint})` : ''),
      );
      throw new InvalidCredentialsError(
        error.hint ? `${description} (${error.hint})` : description,
      );
    }
    this.assertOk(response, 'POST /oauth/token');
    const token = (await response.json()) as {
      access_token: string;
      refresh_token?: string;
      expires_in: number;
      token_type: string;
    };
    return {
      accessToken: token.access_token,
      refreshToken: token.refresh_token ?? null,
      expiresIn: token.expires_in,
      tokenType: token.token_type,
    };
  }

  authorizationConfig(): AuthorizationConfig | null {
    const { clientId, passwordClientId, passwordGrant } = this.config;
    const password = passwordGrant && !!(passwordClientId ?? clientId);
    if (!clientId && !password) return null;
    return {
      authorizeUrl: new URL('/oauth/authorize', this.config.baseUrl).toString(),
      clientId: clientId ?? null,
      scopes: this.config.scopes,
      passwordGrant: password,
    };
  }

  private toUser(user: PireonUser): User {
    return this.users.create({
      id: String(user.id),
      name: user.name,
      email: user.email,
      isActive: user.is_active,
      roles: user.roles,
      appRoles: user.app_roles,
    });
  }

  private async request(path: string, accessToken: string): Promise<Response> {
    try {
      return await fetch(new URL(path, this.config.baseUrl), {
        headers: {
          Authorization: `Bearer ${accessToken}`,
          Accept: 'application/json',
        },
        signal: AbortSignal.timeout(this.config.requestTimeoutMs),
      });
    } catch (error) {
      this.logger.error(
        `Pireon unreachable (${path}): ${(error as Error).message}`,
      );
      throw new ServiceUnavailableException('Identity server unavailable');
    }
  }

  private assertOk(response: Response, operation: string): void {
    if (response.ok) return;
    this.logger.error(`${operation} answered ${response.status}`);
    throw new ServiceUnavailableException('Identity server error');
  }
}