#!/usr/bin/env node

var util = require("util"),
  http = require("http"),
  fs = require("fs"),
  url = require("url"),
  events = require("events");

var DEFAULT_PORT = 3001;

function main(argv) {
  new HttpServer({
    GET: createServlet(StaticServlet),
    HEAD: createServlet(StaticServlet)
  }).start(Number(argv[2]) || DEFAULT_PORT);
}

function escapeHtml(value) {
  return value
    .toString()
    .replace("<", "&lt;")
    .replace(">", "&gt;")
    .replace('"', "&quot;");
}

function createServlet(Class) {
  var servlet = new Class();
  return servlet.handleRequest.bind(servlet);
}

/**
 * An Http server implementation that uses a map of methods to decide
 * action routing.
 *
 * @param {Object} Map of method => Handler function
 */
function HttpServer(handlers) {
  this.handlers = handlers;
  this.server = http.createServer(this.handleRequest_.bind(this));
}

HttpServer.prototype.start = function(port) {
  this.port = port;
  this.server.listen(port);
  util.puts("Http Server running at http://localhost:" + port + "/");
};

HttpServer.prototype.parseUrl_ = function(urlString) {
  var parsed = url.parse(urlString);
  parsed.pathname = url.resolve("/", parsed.pathname);
  return url.parse(url.format(parsed), true);
};

HttpServer.prototype.handleRequest_ = function(req, res) {
  var logEntry = req.method + " " + req.url;
  if (req.headers["user-agent"]) {
    logEntry += " " + req.headers["user-agent"];
  }
  util.puts(logEntry);
  req.url = this.parseUrl_(req.url);
  var handler = this.handlers[req.method];
  if (!handler) {
    res.writeHead(501);
    res.end();
  } else {
    handler.call(this, req, res);
  }
};

/**
 * Handles static content.
 */
function StaticServlet() {}

StaticServlet.MimeMap = {
  txt: "text/plain",
  html: "text/html",
  css: "text/css",
  xml: "application/xml",
  json: "application/json",
  js: "application/javascript",
  jpg: "image/jpeg",
  jpeg: "image/jpeg",
  gif: "image/gif",
  png: "image/png",
  svg: "image/svg+xml"
};

StaticServlet.prototype.handleRequest = function(req, res) {
  var that = this;
  var path = ("./" + req.url.pathname)
    .replace("//", "/")
    .replace(/%(..)/g, function(match, hex) {
      return String.fromCharCode(parseInt(hex, 16));
    });
  var parts = path.split("/");
  if (parts[parts.length - 1].charAt(0) === ".")
    return that.sendForbidden_(req, res, path);
  fs.stat(path, function(err, stat) {
    if (err) return that.sendMissing_(req, res, path);
    if (stat.isDirectory()) return that.sendDirectory_(req, res, path);
    return that.sendFile_(req, res, path);
  });
};

StaticServlet.prototype.sendError_ = function(req, res, error) {
  res.writeHead(500, {
    "Content-Type": "text/html"
  });
  res.write("<!doctype html>\n");
  res.write("<title>Internal Server Error</title>\n");
  res.write("<h1>Internal Server Error</h1>");
  res.write("<pre>" + escapeHtml(util.inspect(error)) + "</pre>");
  util.puts("500 Internal Server Error");
  util.puts(util.inspect(error));
};

StaticServlet.prototype.sendMissing_ = function(req, res, path) {
  path = path.substring(1);
  res.writeHead(404, {
    "Content-Type": "text/html"
  });
  res.write("<!doctype html>\n");
  res.write("<title>404 Not Found</title>\n");
  res.write("<h1>Not Found</h1>");
  res.write(
    "<p>The requested URL " +
      escapeHtml(path) +
      " was not found on this server.</p>"
  );
  res.end();
  util.puts("404 Not Found: " + path);
};

StaticServlet.prototype.sendForbidden_ = function(req, res, path) {
  path = path.substring(1);
  res.writeHead(403, {
    "Content-Type": "text/html"
  });
  res.write("<!doctype html>\n");
  res.write("<title>403 Forbidden</title>\n");
  res.write("<h1>Forbidden</h1>");
  res.write(
    "<p>You do not have permission to access " +
      escapeHtml(path) +
      " on this server.</p>"
  );
  res.end();
  util.puts("403 Forbidden: " + path);
};

StaticServlet.prototype.sendRedirect_ = function(req, res, redirectUrl) {
  res.writeHead(301, {
    "Content-Type": "text/html",
    Location: redirectUrl
  });
  res.write("<!doctype html>\n");
  res.write("<title>301 Moved Permanently</title>\n");
  res.write("<h1>Moved Permanently</h1>");
  res.write(
    '<p>The document has moved <a href="' + redirectUrl + '">here</a>.</p>'
  );
  res.end();
  util.puts("301 Moved Permanently: " + redirectUrl);
};

StaticServlet.prototype.sendFile_ = function(req, res, path) {
  var that = this;
  var file = fs.createReadStream(path);
  res.writeHead(200, {
    "Content-Type": StaticServlet.MimeMap[path.split(".").pop()] || "text/plain"
  });
  if (req.method === "HEAD") {
    res.end();
  } else {
    file.on("data", res.write.bind(res));
    file.on("close", function() {
      res.end();
    });
    file.on("error", function(error) {
      that.sendError_(req, res, error);
    });
  }
};

StaticServlet.prototype.sendDirectory_ = function(req, res, path) {
  var that = this;
  if (path.match(/[^\/]$/)) {
    req.url.pathname += "/";
    var redirectUrl = url.format(url.parse(url.format(req.url)));
    return that.sendRedirect_(req, res, redirectUrl);
  }
  fs.readdir(path, function(err, files) {
    if (err) return that.sendError_(req, res, error);

    if (!files.length) return that.writeDirectoryIndex_(req, res, path, []);

    var remaining = files.length;
    files.forEach(function(fileName, index) {
      fs.stat(path + "/" + fileName, function(err, stat) {
        if (err) return that.sendError_(req, res, err);
        if (stat.isDirectory()) {
          files[index] = fileName + "/";
        }
        if (!--remaining)
          return that.writeDirectoryIndex_(req, res, path, files);
      });
    });
  });
};

StaticServlet.prototype.writeDirectoryIndex_ = function(req, res, path, files) {
  path = path.substring(1);
  res.writeHead(200, {
    "Content-Type": "text/html"
  });
  if (req.method === "HEAD") {
    res.end();
    return;
  }
  res.write("<!doctype html>\n");
  res.write("<title>" + escapeHtml(path) + "</title>\n");
  res.write("<style>\n");
  res.write("  ol { list-style-type: none; font-size: 1.2em; }\n");
  res.write("</style>\n");
  res.write("<h1>Directory: " + escapeHtml(path) + "</h1>");
  res.write("<ol>");
  files.forEach(function(fileName) {
    if (fileName.charAt(0) !== ".") {
      res.write(
        '<li><a href="' +
          escapeHtml(fileName) +
          '">' +
          escapeHtml(fileName) +
          "</a></li>"
      );
    }
  });
  res.write("</ol>");
  res.end();
};

// Must be last,
main(process.argv);
