/**
 * Serla Analytics - JavaScript SDK (Node.js)
 *
 * Usage:
 *   const { Serla } = require('./lib/sdk/serla');
 *   const serla = new Serla('sk_live_YOUR_API_KEY');
 *   await serla.send('user_signup', { plan: 'pro' });
 */

class Serla {
  constructor(apiKey, options = {}) {
    if (!apiKey) {
      throw new Error('Serla: API key is required');
    }

    this.apiKey = apiKey;
    this.endpoint = options.endpoint || 'https://serla.dev/api/events/ingest';
    this.pageviewEndpoint = 'https://serla.dev/api/pageviews/ingest';
    this.debug = options.debug || false;
    this.userId = null;
    this.sessionId = null;

    this.log('Initialized with endpoint:', this.endpoint);
  }

  /**
   * Send an event to Serla
   * @param {string} eventName - Name of the event
   * @param {Object} metadata - Optional metadata object
   * @param {string|null} userId - Optional userId for this event (overrides identify())
   * @param {string|null} sessionId - Optional sessionId for this event (overrides setSession())
   * @returns {Promise<Object>}
   */
  async send(eventName, metadata = {}, userId = undefined, sessionId = undefined) {
    if (!eventName || typeof eventName !== 'string') {
      throw new Error('Serla: Event name is required and must be a string');
    }

    const payload = {
      eventName,
      metadata: metadata || {},
    };

    // Use parameter if provided, otherwise fall back to instance variable
    if (userId !== undefined) {
      if (userId !== null) payload.userId = userId;
    } else if (this.userId) {
      payload.userId = this.userId;
    }

    if (sessionId !== undefined) {
      if (sessionId !== null) payload.sessionId = sessionId;
    } else if (this.sessionId) {
      payload.sessionId = this.sessionId;
    }

    this.log('Sending event:', eventName, metadata);

    try {
      const response = await fetch(this.endpoint, {
        method: 'POST',
        headers: {
          'Content-Type': 'application/json',
          'Authorization': `Bearer ${this.apiKey}`,
        },
        body: JSON.stringify(payload),
      });

      if (!response.ok) {
        const errorText = await response.text();
        throw new Error(`Serla API error (${response.status}): ${errorText}`);
      }

      const data = await response.json();
      this.log('Event sent successfully:', data);
      return data;
    } catch (error) {
      this.log('Error sending event:', error);
      throw error;
    }
  }

  /**
   * Track a pageview
   * @param {string} path - Page path
   * @param {string} referrer - Referrer URL
   * @returns {Promise<Object>}
   */
  async pageview(path, referrer) {
    // Ensure we have a session ID
    if (!this.sessionId) {
      const timestamp = Date.now().toString(36);
      const randomStr = Math.random().toString(36).substring(2, 15);
      this.sessionId = `${timestamp}-${randomStr}`;
    }

    // Construct URL - required field
    let url;
    if (typeof window !== 'undefined') {
      // Browser environment
      if (path) {
        url = `${window.location.origin}${path}`;
      } else {
        url = window.location.href;
      }
    } else {
      // Server environment
      url = path || '/';
    }

    const payload = {
      url,
      sessionId: this.sessionId,
    };

    if (this.userId) {
      payload.userId = this.userId;
    }

    if (referrer) {
      payload.referrer = referrer;
    } else if (typeof document !== 'undefined' && document.referrer) {
      payload.referrer = document.referrer;
    }

    this.log('Tracking pageview:', url);

    try {
      const response = await fetch(this.pageviewEndpoint, {
        method: 'POST',
        headers: {
          'Content-Type': 'application/json',
          'Authorization': `Bearer ${this.apiKey}`,
        },
        body: JSON.stringify(payload),
      });

      if (!response.ok) {
        const errorText = await response.text();
        throw new Error(`Serla API error (${response.status}): ${errorText}`);
      }

      const data = await response.json();
      this.log('Pageview tracked successfully:', data);
      return data;
    } catch (error) {
      this.log('Error tracking pageview:', error);
      throw error;
    }
  }

  /**
   * Identify a user for all subsequent events
   * @param {string|null} userId - User identifier
   */
  identify(userId) {
    this.userId = userId;
    this.log('User identified:', userId);
  }

  /**
   * Set a session ID for all subsequent events
   * @param {string|null} sessionId - Session identifier
   */
  setSession(sessionId) {
    this.sessionId = sessionId;
    this.log('Session set:', sessionId);
  }

  /**
   * Get the current user ID
   * @returns {string|null}
   */
  getUserId() {
    return this.userId;
  }

  /**
   * Get the current session ID
   * @returns {string|null}
   */
  getSessionId() {
    return this.sessionId;
  }

  /**
   * Log debug messages if debug mode is enabled
   * @private
   */
  log(...args) {
    if (this.debug) {
      console.log('[Serla]', ...args);
    }
  }
}

// Factory function
function createSerla(apiKey, options) {
  return new Serla(apiKey, options);
}

// Exports
module.exports = { Serla, createSerla };
module.exports.default = Serla;