const http = require("http");
const url = require("url");
const path = require("path");
const logger = require("./logger");
const database = require("./database");

class TrackingServer {
  constructor() {
    this.server = null;
    this.port = process.env.TRACKING_PORT || 3000;
    this.trackingDomain =
      process.env.TRACKING_DOMAIN || `http://localhost:${this.port}`;
  }

  // 1x1 transparent pixel GIF
  get trackingPixel() {
    return Buffer.from(
      "R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7",
      "base64"
    );
  }

  async start() {
    this.server = http.createServer((req, res) => {
      this.handleRequest(req, res);
    });

    return new Promise((resolve, reject) => {
      this.server.listen(this.port, (err) => {
        if (err) {
          reject(err);
        } else {
          console.log(`📊 Tracking server started on ${this.trackingDomain}`);
          logger.info("Tracking server started", {
            port: this.port,
            domain: this.trackingDomain,
          });
          resolve();
        }
      });
    });
  }

  async stop() {
    if (this.server) {
      return new Promise((resolve) => {
        this.server.close(() => {
          console.log("📊 Tracking server stopped");
          logger.info("Tracking server stopped");
          resolve();
        });
      });
    }
  }

  async handleRequest(req, res) {
    const parsedUrl = url.parse(req.url, true);
    const pathname = parsedUrl.pathname;

    try {
      if (pathname.startsWith("/track/open/")) {
        await this.handleOpenTracking(req, res, parsedUrl);
      } else if (pathname.startsWith("/track/click/")) {
        await this.handleClickTracking(req, res, parsedUrl);
      } else if (pathname === "/health") {
        this.handleHealthCheck(req, res);
      } else {
        this.handle404(req, res);
      }
    } catch (error) {
      logger.error("Tracking request error", {
        error: error.message,
        url: req.url,
        userAgent: req.headers["user-agent"],
      });
      this.handle500(req, res);
    }
  }

  async handleOpenTracking(req, res, parsedUrl) {
    const pathParts = parsedUrl.pathname.split("/");
    const trackingId = pathParts[3]; // /track/open/{trackingId}

    if (!trackingId) {
      return this.handle400(req, res, "Missing tracking ID");
    }

    // Log the email open
    const trackingData = {
      trackingId,
      event: "email_open",
      timestamp: new Date().toISOString(),
      ip: req.connection.remoteAddress || req.headers["x-forwarded-for"],
      userAgent: req.headers["user-agent"],
      referer: req.headers.referer,
    };

    logger.info("Email opened", trackingData);

    // Store in database
    try {
      await database.storeTrackingEvent(trackingId, "open", trackingData);
    } catch (error) {
      logger.error("Failed to store tracking event", {
        trackingId,
        event: "open",
        error: error.message,
      });
    }

    // Return 1x1 transparent pixel
    res.writeHead(200, {
      "Content-Type": "image/gif",
      "Content-Length": this.trackingPixel.length,
      "Cache-Control": "no-cache, no-store, must-revalidate",
      Pragma: "no-cache",
      Expires: "0",
    });
    res.end(this.trackingPixel);
  }

  async handleClickTracking(req, res, parsedUrl) {
    const pathParts = parsedUrl.pathname.split("/");
    const trackingId = pathParts[3]; // /track/click/{trackingId}
    const linkId = pathParts[4]; // /track/click/{trackingId}/{linkId}
    const targetUrl = parsedUrl.query.url;

    if (!trackingId || !targetUrl) {
      return this.handle400(req, res, "Missing tracking ID or target URL");
    }

    // Log the click
    const trackingData = {
      trackingId,
      linkId,
      event: "email_click",
      targetUrl,
      timestamp: new Date().toISOString(),
      ip: req.connection.remoteAddress || req.headers["x-forwarded-for"],
      userAgent: req.headers["user-agent"],
      referer: req.headers.referer,
    };

    logger.info("Email link clicked", trackingData);

    // Store in database
    try {
      await database.storeTrackingEvent(trackingId, "click", trackingData);
    } catch (error) {
      logger.error("Failed to store tracking event", {
        trackingId,
        event: "click",
        error: error.message,
      });
    }

    // Redirect to target URL
    res.writeHead(302, {
      Location: targetUrl,
      "Cache-Control": "no-cache",
    });
    res.end();
  }

  handleHealthCheck(req, res) {
    res.writeHead(200, { "Content-Type": "application/json" });
    res.end(
      JSON.stringify({
        status: "healthy",
        timestamp: new Date().toISOString(),
        uptime: process.uptime(),
      })
    );
  }

  handle400(req, res, message) {
    res.writeHead(400, { "Content-Type": "text/plain" });
    res.end(`Bad Request: ${message}`);
  }

  handle404(req, res) {
    res.writeHead(404, { "Content-Type": "text/plain" });
    res.end("Not Found");
  }

  handle500(req, res) {
    res.writeHead(500, { "Content-Type": "text/plain" });
    res.end("Internal Server Error");
  }

  // Generate tracking URLs
  generateOpenTrackingUrl(emailId) {
    return `${this.trackingDomain}/track/open/${emailId}`;
  }

  generateClickTrackingUrl(emailId, linkId, targetUrl) {
    const encodedUrl = encodeURIComponent(targetUrl);
    return `${this.trackingDomain}/track/click/${emailId}/${linkId}?url=${encodedUrl}`;
  }

  // Add tracking to email content
  addTrackingToEmail(htmlContent, emailId) {
    if (!htmlContent) return htmlContent;

    // Add tracking pixel just before closing body tag
    const trackingPixel = `<img src="${this.generateOpenTrackingUrl(
      emailId
    )}" width="1" height="1" style="display:none;" alt="" />`;

    if (htmlContent.includes("</body>")) {
      return htmlContent.replace("</body>", `${trackingPixel}</body>`);
    } else {
      // If no body tag, append at the end
      return htmlContent + trackingPixel;
    }
  }

  // Replace links with tracking URLs
  addClickTrackingToEmail(htmlContent, emailId) {
    if (!htmlContent) return htmlContent;

    let linkId = 0;
    return htmlContent.replace(
      /<a\s+([^>]*href=["']([^"']+)["'][^>]*)>/gi,
      (match, attributes, href) => {
        linkId++;

        // Skip if already a tracking URL or mailto/tel links
        if (
          href.includes("/track/click/") ||
          href.startsWith("mailto:") ||
          href.startsWith("tel:")
        ) {
          return match;
        }

        const trackingUrl = this.generateClickTrackingUrl(
          emailId,
          linkId,
          href
        );
        return `<a ${attributes.replace(
          /href=["'][^"']+["']/i,
          `href="${trackingUrl}"`
        )}`;
      }
    );
  }

  // Combined method to add all tracking
  addEmailTracking(htmlContent, emailId, skipTracking = false) {
    if (!htmlContent) return htmlContent;

    // If skip tracking is enabled, return original content without tracking
    if (skipTracking) {
      return htmlContent;
    }

    let trackedContent = this.addClickTrackingToEmail(htmlContent, emailId);
    trackedContent = this.addTrackingToEmail(trackedContent, emailId);

    return trackedContent;
  }
}

module.exports = new TrackingServer();