const axios = require('axios');
const crypto = require('crypto');
const fs = require('fs');
const https = require('https');

function trimSlash(value) {
  return String(value || '').replace(/\/+$/, '');
}

function encodeQuery(query = {}) {
  const params = new URLSearchParams();
  for (const [key, value] of Object.entries(query || {})) {
    if (value !== undefined && value !== null && value !== '') {
      params.set(key, String(value));
    }
  }
  const text = params.toString();
  return text ? `?${text}` : '';
}

function formatOmadaError(error, context = '') {
  if (error.response) {
    const data = error.response.data;
    const body = typeof data === 'string' ? data : JSON.stringify(data);
    return `${context}${error.response.status} ${error.response.statusText}: ${body}`;
  }
  if (error.omada) {
    const detail = error.result ? ` ${JSON.stringify(error.result)}` : '';
    return `${context}Omada error ${error.errorCode}: ${error.message}${detail}`;
  }
  return `${context}${error.message}`;
}

class OmadaClient {
  constructor(config) {
    this.config = config || {};
    this.controllerUrl = trimSlash(config.controllerUrl);
    this.omadacId = config.omadacId;
    this.clientId = config.clientId;
    this.clientSecret = config.clientSecret;
    this.accessToken = config.accessToken || null;
    this.authHeaderStyle = config.authHeaderStyle || 'access-token';
    this.controllerId = config.controllerId || config.omadacId || null;
    this.csrfToken = null;
    this.sessionCookies = '';

    this.http = axios.create({
      baseURL: this.controllerUrl,
      timeout: Number(config.timeoutMs || 30000),
      httpsAgent: new https.Agent({
        rejectUnauthorized: config.rejectUnauthorized === true,
      }),
      validateStatus: () => true,
    });
  }

  requireOpenApiConfig() {
    const missing = [];
    if (!this.controllerUrl) missing.push('OMADA_URL');
    if (!this.omadacId) missing.push('OMADA_OPENAPI_OMADAC_ID');
    if (!this.clientId) missing.push('OMADA_OPENAPI_CLIENT_ID');
    if (!this.clientSecret) missing.push('OMADA_OPENAPI_CLIENT_SECRET');
    if (missing.length) {
      throw new Error(`Missing required Omada OpenAPI config: ${missing.join(', ')}`);
    }
  }

  async authorize() {
    this.requireOpenApiConfig();
    const body = {
      omadacId: this.omadacId,
      client_id: this.clientId,
      client_secret: this.clientSecret,
    };
    const res = await this.http.post('/openapi/authorize/token?grant_type=client_credentials', body);
    const data = this.unwrap(res, 'authorize');
    const token = data.result?.accessToken || data.result?.token || data.accessToken || data.token;
    if (!token) {
      throw new Error(`Authorize succeeded but no access token was found: ${JSON.stringify(data)}`);
    }
    this.accessToken = token;
    return data;
  }

  authHeaders(style = this.authHeaderStyle) {
    if (!this.accessToken) return {};
    if (style === 'bearer-access-token') {
      return { Authorization: `Bearer AccessToken=${this.accessToken}` };
    }
    if (style === 'bearer') {
      return { Authorization: `Bearer ${this.accessToken}` };
    }
    return { Authorization: `AccessToken=${this.accessToken}` };
  }

  openApiPath(pathPart) {
    const suffix = String(pathPart || '').startsWith('/') ? pathPart : `/${pathPart}`;
    return `/openapi/v1/${this.omadacId}${suffix}`;
  }

  async request(method, url, { body = null, query = null, headers = {}, retry = true } = {}) {
    if (!this.accessToken) {
      await this.authorize();
    }

    const fullUrl = `${url}${encodeQuery(query)}`;
    const styles = [this.authHeaderStyle, 'bearer-access-token', 'bearer']
      .filter((style, index, arr) => arr.indexOf(style) === index);
    let lastError = null;

    for (const style of styles) {
      const res = await this.http.request({
        method,
        url: fullUrl,
        headers: {
          ...this.authHeaders(style),
          ...headers,
        },
        data: body ?? undefined,
      });

      try {
        const data = this.unwrap(res, `${method} ${fullUrl}`);
        this.authHeaderStyle = style;
        return data;
      } catch (err) {
        lastError = err;
        if (retry && this.isExpiredToken(err)) {
          this.accessToken = null;
          await this.authorize();
          return this.request(method, url, { body, query, headers, retry: false });
        }
        if (!this.isAuthHeaderCandidate(err)) {
          throw err;
        }
      }
    }

    throw lastError;
  }

  async openApi(method, pathPart, options = {}) {
    return this.request(method, this.openApiPath(pathPart), options);
  }

  async controllerLogin() {
    if (!this.controllerId) {
      const info = await this.http.get('/api/info');
      const data = this.unwrap(info, 'GET /api/info');
      this.controllerId = data.result?.omadacId;
      if (!this.controllerId) {
        throw new Error(`Controller ID not found in /api/info: ${JSON.stringify(data)}`);
      }
    }

    const username = this.config.controllerUsername || process.env.OMADA_USER;
    const password = this.config.controllerPassword || process.env.OMADA_PASS;
    if (!username || !password) {
      throw new Error('Missing OMADA_USER/OMADA_PASS for Omada controller fallback');
    }

    const res = await this.http.post(`/${this.controllerId}/api/v2/login`, { username, password });
    const data = this.unwrap(res, 'controller login');
    this.csrfToken = data.result?.token;
    this.sessionCookies = (res.headers['set-cookie'] || []).map((item) => item.split(';')[0]).join('; ');
    return data;
  }

  async controllerRequest(method, pathPart, body = null, retried = false) {
    if (!this.controllerId || !this.csrfToken) {
      await this.controllerLogin();
    }
    const path = String(pathPart || '').startsWith('/') ? pathPart : `/${pathPart}`;
    const res = await this.http.request({
      method,
      url: `/${this.controllerId}/api/v2${path}`,
      headers: {
        'Csrf-Token': this.csrfToken,
        Cookie: this.sessionCookies,
        'Content-Type': 'application/json',
      },
      data: body ?? undefined,
    });

    try {
      return this.unwrap(res, `${method} controller ${path}`);
    } catch (err) {
      if (!retried && this.isExpiredToken(err)) {
        await this.controllerLogin();
        return this.controllerRequest(method, pathPart, body, true);
      }
      throw err;
    }
  }

  async controllerUploadDataField(pathPart, data, retried = false) {
    if (!this.controllerId || !this.csrfToken) {
      await this.controllerLogin();
    }
    const path = String(pathPart || '').startsWith('/') ? pathPart : `/${pathPart}`;
    const form = new FormData();
    form.append('data', JSON.stringify(data));

    const res = await this.http.request({
      method: 'POST',
      url: `/${this.controllerId}/api/v2${path}`,
      headers: {
        'Csrf-Token': this.csrfToken,
        Cookie: this.sessionCookies,
        'X-Requested-With': 'XMLHttpRequest',
        refresh: 'manual',
      },
      data: form,
    });

    try {
      return this.unwrap(res, `POST controller ${path}`);
    } catch (err) {
      if (!retried && this.isExpiredToken(err)) {
        await this.controllerLogin();
        return this.controllerUploadDataField(pathPart, data, true);
      }
      throw err;
    }
  }

  fileMd5(filePath) {
    return crypto.createHash('md5').update(fs.readFileSync(filePath)).digest('hex');
  }

  unwrap(res, label) {
    const data = res.data;
    if (res.status < 200 || res.status >= 300) {
      const err = new Error(`${label} failed with HTTP ${res.status}: ${typeof data === 'string' ? data : JSON.stringify(data)}`);
      err.response = res;
      throw err;
    }
    if (data && typeof data === 'object' && 'errorCode' in data && data.errorCode !== 0) {
      const err = new Error(data.msg || data.message || `${label} failed`);
      err.omada = true;
      err.errorCode = data.errorCode;
      err.result = data.result;
      throw err;
    }
    return data;
  }

  isExpiredToken(err) {
    return err.response?.status === 401 || [-1000, -44106, -44112].includes(err.errorCode);
  }

  isAuthHeaderCandidate(err) {
    return err.response?.status === 401 || [-44106, -44112, -44113].includes(err.errorCode);
  }
}

module.exports = {
  OmadaClient,
  formatOmadaError,
};