/**
 * BaserowJwtManager — auto-login service account pattern.
 *
 * Pourquoi ce module existe :
 *   Le DB token Baserow (Token brg_*) suffit pour les CRUD rows mais Baserow
 *   renvoie 401 PERMISSION_DENIED sur les endpoints metadata (views, tables
 *   detail). Ces endpoints necessitent un JWT user obtenu via token-auth.
 *
 * Pattern :
 *   - Lazy init : pas de login au boot, premier getToken() declenche le login.
 *   - Cache memoire : le JWT est conserve jusqu'a `exp - refreshMarginSeconds`.
 *   - Refresh : POST /api/user/token-refresh/ avec le token courant avant expiry.
 *   - Mutex : un seul refresh concurrent (lock promesse partage).
 *   - Fallback : si creds absentes, isEnabled() = false ; getToken() leve une
 *     erreur BASEROW_USER_AUTH_NOT_CONFIGURED que le caller transforme en 503.
 *
 * Sources :
 *   - baserow.io/docs/apis/rest-api : POST /api/user/token-auth/ (CLAIM L3)
 *   - github.com/code-watch/baserow/blob/master/docs/getting-started/api.md : JWT 60min (CLAIM L3)
 *   - community.baserow.io/t/jwt-token-authentication/4138 : email not username (CLAIM L3)
 */

import type { Logger } from 'pino';

// ---------------------------------------------------------------------------
// Public interface
// ---------------------------------------------------------------------------

export interface BaserowJwtManager {
  /** Returns a valid JWT. Refreshes if close to expiry. */
  getToken(): Promise<string>;
  /** True if user credentials are configured. */
  isEnabled(): boolean;
}

// ---------------------------------------------------------------------------
// Internal types
// ---------------------------------------------------------------------------

interface TokenAuthResponse {
  token: string;
}

interface DecodedJwtPayload {
  exp?: number;
}

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

/**
 * Decode the payload of a JWT without verifying signature.
 * Used only to read `exp` so we know when to refresh.
 */
function decodeJwtPayload(token: string): DecodedJwtPayload {
  const parts = token.split('.');
  if (parts.length !== 3) return {};
  try {
    const raw = parts[1];
    if (!raw) return {};
    // atob is available in Node 22 globalThis. Buffer fallback for safety.
    const decoded =
      typeof atob === 'function'
        ? atob(raw.replace(/-/g, '+').replace(/_/g, '/'))
        : Buffer.from(raw, 'base64url').toString('utf8');
    return JSON.parse(decoded) as DecodedJwtPayload;
  } catch {
    return {};
  }
}

// ---------------------------------------------------------------------------
// Implementation
// ---------------------------------------------------------------------------

export class BaserowJwtManagerImpl implements BaserowJwtManager {
  private readonly baseUrl: string;
  private readonly email: string;
  private readonly password: string;
  private readonly refreshMarginSeconds: number;
  private readonly logger: Logger;

  private cachedToken: string | null = null;
  private tokenExp: number | null = null; // unix timestamp seconds
  // Lock: prevents concurrent logins/refreshes under burst conditions.
  private inflightRefresh: Promise<string> | null = null;

  constructor(opts: {
    baseUrl: string;
    email: string;
    password: string;
    refreshMarginSeconds: number;
    logger: Logger;
  }) {
    this.baseUrl = opts.baseUrl.replace(/\/$/, '');
    this.email = opts.email;
    this.password = opts.password;
    this.refreshMarginSeconds = opts.refreshMarginSeconds;
    this.logger = opts.logger.child({ service: 'baserow-jwt-manager' });
  }

  isEnabled(): boolean {
    return true;
  }

  async getToken(): Promise<string> {
    // If we have a cached token that is still fresh, return it immediately.
    if (this.cachedToken !== null && this.isTokenFresh()) {
      return this.cachedToken;
    }

    // Dedup concurrent refresh: if a refresh is already in flight, await it.
    if (this.inflightRefresh !== null) {
      return this.inflightRefresh;
    }

    this.inflightRefresh = this.acquireToken().finally(() => {
      this.inflightRefresh = null;
    });

    return this.inflightRefresh;
  }

  // ---------------------------------------------------------------------------
  // Private
  // ---------------------------------------------------------------------------

  private isTokenFresh(): boolean {
    if (this.tokenExp === null) return false;
    const nowSeconds = Math.floor(Date.now() / 1000);
    return this.tokenExp - this.refreshMarginSeconds > nowSeconds;
  }

  private storeToken(token: string): void {
    this.cachedToken = token;
    const payload = decodeJwtPayload(token);
    if (typeof payload.exp === 'number') {
      this.tokenExp = payload.exp;
      this.logger.debug(
        { exp: this.tokenExp, margin: this.refreshMarginSeconds },
        'jwt token stored',
      );
    } else {
      // No exp claim — default 55 min from now to stay safe within 60min Baserow TTL.
      this.tokenExp = Math.floor(Date.now() / 1000) + 55 * 60;
      this.logger.warn('jwt token has no exp claim — defaulting to 55min TTL');
    }
  }

  /**
   * Acquire a token: refresh if we have a stale cached token, else login from scratch.
   */
  private async acquireToken(): Promise<string> {
    if (this.cachedToken !== null && !this.isTokenFresh()) {
      // Try refresh first; fall back to full login on failure.
      try {
        const token = await this.doRefresh(this.cachedToken);
        this.storeToken(token);
        this.logger.info('baserow jwt refreshed');
        return token;
      } catch (err) {
        this.logger.warn({ err }, 'baserow jwt refresh failed — falling back to full login');
        // Fall through to full login below.
      }
    }

    const token = await this.doLogin();
    this.storeToken(token);
    this.logger.info('baserow jwt login succeeded');
    return token;
  }

  private async doLogin(): Promise<string> {
    this.logger.debug({ email: this.email }, 'baserow jwt login');
    const url = `${this.baseUrl}/user/token-auth/`;
    const res = await fetch(url, {
      method: 'POST',
      headers: { 'Content-Type': 'application/json' },
      body: JSON.stringify({ username: this.email, password: this.password }),
      signal: AbortSignal.timeout(10_000),
    });

    if (!res.ok) {
      const body = await res.text().catch(() => '');
      this.logger.error(
        { status: res.status, email: this.email, password: '***' },
        'baserow jwt login failed',
      );
      throw new BaserowAuthError(
        `BRIDGE_BASEROW_AUTH_FAILED: login returned ${res.status} — ${body}`,
        res.status,
      );
    }

    const data = (await res.json()) as TokenAuthResponse;
    if (!data.token) {
      throw new BaserowAuthError('BRIDGE_BASEROW_AUTH_FAILED: response missing token field', 502);
    }
    return data.token;
  }

  private async doRefresh(currentToken: string): Promise<string> {
    this.logger.debug('baserow jwt refresh');
    const url = `${this.baseUrl}/user/token-refresh/`;
    const res = await fetch(url, {
      method: 'POST',
      headers: { 'Content-Type': 'application/json' },
      body: JSON.stringify({ token: currentToken }),
      signal: AbortSignal.timeout(10_000),
    });

    if (!res.ok) {
      throw new BaserowAuthError(
        `BRIDGE_BASEROW_AUTH_FAILED: refresh returned ${res.status}`,
        res.status,
      );
    }

    const data = (await res.json()) as TokenAuthResponse;
    if (!data.token) {
      throw new BaserowAuthError(
        'BRIDGE_BASEROW_AUTH_FAILED: refresh response missing token field',
        502,
      );
    }
    return data.token;
  }
}

// ---------------------------------------------------------------------------
// Disabled stub (when creds not configured)
// ---------------------------------------------------------------------------

export class BaserowJwtManagerDisabled implements BaserowJwtManager {
  isEnabled(): boolean {
    return false;
  }

  getToken(): Promise<string> {
    return Promise.reject(
      new BaserowAuthError(
        'BASEROW_USER_AUTH_NOT_CONFIGURED: set BASEROW_USER_EMAIL and BASEROW_USER_PASSWORD to enable metadata endpoints',
        503,
      ),
    );
  }
}

// ---------------------------------------------------------------------------
// Error class
// ---------------------------------------------------------------------------

export class BaserowAuthError extends Error {
  constructor(
    message: string,
    public readonly statusCode: number,
  ) {
    super(message);
    this.name = 'BaserowAuthError';
  }
}

// ---------------------------------------------------------------------------
// Factory
// ---------------------------------------------------------------------------

export function createBaserowJwtManager(opts: {
  baseUrl: string;
  email?: string;
  password?: string;
  refreshMarginSeconds: number;
  logger: Logger;
}): BaserowJwtManager {
  if (opts.email && opts.password) {
    return new BaserowJwtManagerImpl({
      baseUrl: opts.baseUrl,
      email: opts.email,
      password: opts.password,
      refreshMarginSeconds: opts.refreshMarginSeconds,
      logger: opts.logger,
    });
  }
  return new BaserowJwtManagerDisabled();
}