/**
 * @fileoverview HTTP client for api.veraetime.net (with mock mode).
 * @module clients/veraeClient
 */

import { createHash, randomUUID } from 'node:crypto';
import { config } from '../config.js';
import { AppError } from '../errors.js';
import { createDebugger } from '../debug/logger.js';

const log = createDebugger('http');

const mockJobs = new Map();
/** @type {Map<string, { jobId: string, sha256: string, timestamp?: string, publicMetadata?: object, privateMetadata?: object }>} */
const mockHashes = new Map();

/**
 * @param {string} data
 * @returns {string}
 */
export function sha256Hex(data) {
  return createHash('sha256').update(String(data), 'utf8').digest('hex');
}

/**
 * @param {number} ms
 * @returns {Promise<void>}
 */
function delay(ms) {
  return new Promise((resolve) => setTimeout(resolve, ms));
}

async function mockLogin({ username, password }) {
  if (!username || !password) {
    throw new AppError('Invalid credentials', { status: 401, code: 'UNAUTHORIZED' });
  }
  const expiresAt = new Date(Date.now() + 24 * 60 * 60 * 1000).toISOString();
  return {
    token: `mock-jwt-${username}`,
    expiresAt,
    user: {
      id: randomUUID(),
      username,
      role: username.includes('admin') ? 'admin' : 'user',
    },
  };
}

async function mockValidate(token) {
  if (!token?.startsWith('mock-jwt-')) {
    throw new AppError('Invalid or expired token', { status: 401, code: 'UNAUTHORIZED' });
  }
  const username = token.replace('mock-jwt-', '');
  return {
    valid: true,
    userId: randomUUID(),
    username,
    role: 'user',
    expiresAt: new Date(Date.now() + 24 * 60 * 60 * 1000).toISOString(),
  };
}

async function mockCreateTimestamp({ data, hashAlg, sha256, publicMetadata, privateMetadata }) {
  if (!data && !sha256) {
    throw new AppError('Invalid input data', { status: 400, code: 'VALIDATION_ERROR' });
  }
  const key = (sha256 || sha256Hex(data)).toLowerCase();
  const existing = mockHashes.get(key);
  if (existing) {
    const job = mockJobs.get(existing.jobId);
    return {
      jobId: existing.jobId,
      sha256: key,
      existing: true,
      timestamp: job?.completedAt ?? existing.timestamp,
    };
  }

  const jobId = randomUUID();
  mockJobs.set(jobId, {
    id: jobId,
    status: 'pending',
    createdAt: Date.now(),
    data: data ?? key,
    hashAlg: hashAlg ?? 'SHA256',
    sha256: key,
    publicMetadata: publicMetadata ?? {},
    privateMetadata: privateMetadata ?? {},
  });
  mockHashes.set(key, { jobId, sha256: key, publicMetadata, privateMetadata });

  const delayMs = config.mockJobCompleteMs ?? 150;
  setTimeout(() => {
    const job = mockJobs.get(jobId);
    if (!job) return;
    job.status = 'completed';
    job.result = `mock-cert-${jobId}`;
    job.completedAt = new Date().toISOString();
    job.metadata = {
      blockIndex: 42,
      timestamp: job.completedAt,
      certificate: job.result,
      sha256: key,
      publicMetadata: job.publicMetadata,
    };
    const rec = mockHashes.get(key);
    if (rec) rec.timestamp = job.completedAt;
  }, delayMs);

  return { jobId, sha256: key, existing: false };
}

async function mockGetStatus(jobId) {
  const job = mockJobs.get(jobId);
  if (!job) {
    throw new AppError('Job not found', { status: 404, code: 'NOT_FOUND' });
  }
  return {
    id: job.id,
    status: job.status,
    result: job.result,
    completedAt: job.completedAt,
    metadata: job.metadata,
    privateMetadata: job.privateMetadata,
    error: job.error,
    sha256: job.sha256,
  };
}

async function mockLookupHash(sha256) {
  const key = String(sha256 || '').toLowerCase();
  const rec = mockHashes.get(key);
  if (!rec) {
    throw new AppError('Hash not found', { status: 404, code: 'NOT_FOUND' });
  }
  const job = mockJobs.get(rec.jobId);
  return {
    sha256: key,
    exists: true,
    jobId: rec.jobId,
    timestamp: rec.timestamp ?? job?.completedAt,
    status: job?.status,
    publicMetadata: job?.publicMetadata ?? rec.publicMetadata ?? {},
  };
}

async function mockVerify({ certificate }) {
  if (!certificate) {
    throw new AppError('Invalid input data', { status: 400, code: 'VALIDATION_ERROR' });
  }
  const valid = certificate.startsWith('mock-cert-') || certificate.startsWith('eyJ');
  return valid
    ? { valid: true, timestamp: new Date().toISOString(), blockIndex: 42 }
    : { valid: false };
}

/**
 * Low-level fetch to Verae API.
 * @param {string} path
 * @param {{ method?: string, token?: string, body?: unknown }} [options]
 * @returns {Promise<any>}
 */
async function request(path, { method = 'GET', token, body } = {}) {
  const url = `${config.veraeApiBaseUrl}${path}`;
  const headers = { Accept: 'application/json' };

  if (token) {
    headers.Authorization = `Bearer ${token}`;
  }
  if (body !== undefined) {
    headers['Content-Type'] = 'application/json';
  }

  const started = Date.now();
  log.debug('verae request', { method, path, hasToken: Boolean(token) });

  const response = await fetch(url, {
    method,
    headers,
    body: body !== undefined ? JSON.stringify(body) : undefined,
  });

  let payload = null;
  const text = await response.text();
  if (text) {
    try {
      payload = JSON.parse(text);
    } catch {
      payload = { error: text };
    }
  }

  log.debug('verae response', {
    method,
    path,
    status: response.status,
    durationMs: Date.now() - started,
  });

  if (!response.ok) {
    throw new AppError(payload?.error ?? `Verae API error (${response.status})`, {
      status: response.status,
      code: payload?.code ?? 'VERAE_API_ERROR',
      details: payload,
    });
  }

  return payload;
}

/**
 * Verae API client (mock when config.mockVerae is true).
 */
export const veraeClient = {
  /**
   * @param {{ username: string, password: string }} credentials
   */
  async login(credentials) {
    if (config.mockVerae) return mockLogin(credentials);
    return request('/auth/login', { method: 'POST', body: credentials });
  },

  /**
   * @param {string} token
   */
  async validate(token) {
    if (config.mockVerae) return mockValidate(token);
    return request('/auth/validate', { token });
  },

  /**
   * @param {string} token
   * @param {{ data: string, hashAlg?: string }} body
   */
  async createTimestamp(token, body) {
    if (config.mockVerae) return mockCreateTimestamp(body);
    const liveBody = { data: body.data, hashAlg: body.hashAlg };
    return request('/api/timestamp', { method: 'POST', token, body: liveBody });
  },

  /**
   * @param {string} token
   * @param {string} sha256
   */
  async lookupHash(token, sha256) {
    if (config.mockVerae) return mockLookupHash(sha256);
    throw new AppError('Hash lookup is not on the live Verae OpenAPI', {
      status: 501,
      code: 'NOT_IMPLEMENTED',
    });
  },

  /**
   * @param {string} token
   * @param {{ items: Array<{ data: string, hashAlg?: string }> }} body
   */
  async createBatchTimestamp(token, body) {
    if (config.mockVerae) {
      const jobIds = [];
      for (const item of body.items ?? []) {
        const res = await mockCreateTimestamp(item);
        jobIds.push(res.jobId);
      }
      return { jobIds };
    }
    return request('/api/batch/timestamp', { method: 'POST', token, body });
  },

  /**
   * @param {string} token
   * @param {string} jobId
   */
  async getStatus(token, jobId) {
    if (config.mockVerae) return mockGetStatus(jobId);
    return request(`/api/status/${encodeURIComponent(jobId)}`, { token });
  },

  /**
   * @param {string} token
   * @param {{ jobIds: string[] }} body
   */
  async getBatchStatus(token, body) {
    if (config.mockVerae) {
      const results = {};
      for (const jobId of body.jobIds ?? []) {
        results[jobId] = await mockGetStatus(jobId);
      }
      return { results };
    }
    return request('/api/batch/status', { method: 'POST', token, body });
  },

  /**
   * @param {string} token
   * @param {{ certificate: string }} body
   */
  async verify(token, body) {
    if (config.mockVerae) return mockVerify(body);
    return request('/api/verify', { method: 'POST', token, body });
  },

  /**
   * @param {string} token
   * @param {{ certificates: string[] }} body
   */
  async verifyBatch(token, body) {
    if (config.mockVerae) {
      const results = [];
      for (const certificate of body.certificates ?? []) {
        results.push(await mockVerify({ certificate }));
      }
      return { results };
    }
    return request('/api/batch/verify', { method: 'POST', token, body });
  },

  /**
   * @param {string} token
   * @param {string} jobId
   */
  async getJobVerification(token, jobId) {
    if (config.mockVerae) return mockGetStatus(jobId);
    return request(`/api/verify/${encodeURIComponent(jobId)}`, { token });
  },

  /**
   * Poll until completed/failed or timeout.
   * @param {string} token
   * @param {string} jobId
   * @param {{ maxAttempts: number, intervalMs: number }} options
   */
  async waitForJob(token, jobId, { maxAttempts, intervalMs }) {
    for (let attempt = 0; attempt < maxAttempts; attempt += 1) {
      const status = await this.getStatus(token, jobId);
      if (status.status === 'completed' || status.status === 'failed') {
        return status;
      }
      await delay(intervalMs);
    }
    throw new AppError(`Job ${jobId} timed out`, { status: 504, code: 'GATEWAY_TIMEOUT' });
  },
};

/**
 * Clear mock jobs (tests only).
 * @returns {void}
 */
export function clearMockJobs() {
  mockJobs.clear();
  mockHashes.clear();
}