/**
 * Module dependencies.
 */

var mixin = require('utils-merge');
var escapeHtml = require('escape-html');
var Router = require('./router');
var methods = require('methods');
var middleware = require('./middleware/init');
var query = require('./middleware/query');
var debug = require('debug')('express:application');
var View = require('./view');
var http = require('http');

/**
 * Application prototype.
 */

var app = exports = module.exports = {};

/**
 * Initialize the server.
 *
 *   - setup default configuration
 *   - setup default middleware
 *   - setup route reflection methods
 *
 * @api private
 */

app.init = function(){
  this.cache = {};
  this.settings = {};
  this.engines = {};
  this.defaultConfiguration();
};

/**
 * Initialize application configuration.
 *
 * @api private
 */

app.defaultConfiguration = function(){
  // default settings
  this.enable('x-powered-by');
  this.enable('etag');
  var env = process.env.NODE_ENV || 'development';
  this.set('env', env);
  this.set('subdomain offset', 2);

  debug('booting in %s mode', env);

  // inherit protos
  this.on('mount', function(parent){
    this.request.__proto__ = parent.request;
    this.response.__proto__ = parent.response;
    this.engines.__proto__ = parent.engines;
    this.settings.__proto__ = parent.settings;
  });

  // setup locals
  this.locals = Object.create(null);

  // top-most app is mounted at /
  this.mountpath = '/';

  // default locals
  this.locals.settings = this.settings;

  // default configuration
  this.set('view', View);
  this.set('views', process.cwd() + '/views');
  this.set('jsonp callback name', 'callback');

  if (env === 'production') {
    this.enable('view cache');
  }

  Object.defineProperty(this, 'router', {
    get: function() {
      throw new Error('\'app.router\' is deprecated!\nPlease see the 3.x to 4.x migration guide for details on how to update your app.');
    }
  });
};

/**
 * lazily adds the base router if it has not yet been added.
 *
 * We cannot add the base router in the defaultConfiguration because
 * it reads app settings which might be set after that has run.
 *
 * @api private
 */
app.lazyrouter = function() {
  if (!this._router) {
    this._router = new Router({
      caseSensitive: this.enabled('case sensitive routing'),
      strict: this.enabled('strict routing')
    });

    this._router.use(query());
    this._router.use(middleware.init(this));
  }
};

/**
 * Dispatch a req, res pair into the application. Starts pipeline processing.
 *
 * If no _done_ callback is provided, then default error handlers will respond
 * in the event of an error bubbling through the stack.
 *
 * @api private
 */

app.handle = function(req, res, done) {
  var env = this.get('env');

  this._router.handle(req, res, function(err) {
    if (done) {
      return done(err);
    }

    // unhandled error
    if (err) {
      // default to 500
      if (res.statusCode < 400) res.statusCode = 500;
      debug('default %s', res.statusCode);

      // respect err.status
      if (err.status) res.statusCode = err.status;

      // production gets a basic error message
      var msg = 'production' == env
        ? http.STATUS_CODES[res.statusCode]
        : err.stack || err.toString();
      msg = escapeHtml(msg);

      // log to stderr in a non-test env
      if ('test' != env) console.error(err.stack || err.toString());
      if (res.headersSent) return req.socket.destroy();
      res.setHeader('Content-Type', 'text/html');
      res.setHeader('Content-Length', Buffer.byteLength(msg));
      if ('HEAD' == req.method) return res.end();
      res.end(msg);
      return;
    }

    // 404
    debug('default 404');
    res.statusCode = 404;
    res.setHeader('Content-Type', 'text/html');
    if ('HEAD' == req.method) return res.end();
    res.end('Cannot ' + escapeHtml(req.method) + ' ' + escapeHtml(req.originalUrl) + '\n');
  });
};

/**
 * Proxy `Router#use()` to add middleware to the app router.
 * See Router#use() documentation for details.
 *
 * If the _fn_ parameter is an express app, then it will be
 * mounted at the _route_ specified.
 *
 * @param {String|Function|Server} route
 * @param {Function|Server} fn
 * @return {app} for chaining
 * @api public
 */

app.use = function(route, fn){
  var mount_app;

  // default route to '/'
  if ('string' != typeof route) fn = route, route = '/';

  // express app
  if (fn.handle && fn.set) mount_app = fn;

  // restore .app property on req and res
  if (mount_app) {
    debug('.use app under %s', route);
    mount_app.mountpath = route;
    fn = function(req, res, next) {
      var orig = req.app;
      mount_app.handle(req, res, function(err) {
        req.__proto__ = orig.request;
        res.__proto__ = orig.response;
        next(err);
      });
    };
  }

  this.lazyrouter();
  this._router.use(route, fn);

  // mounted an app
  if (mount_app) {
    mount_app.parent = this;
    mount_app.emit('mount', this);
  }

  return this;
};

/**
 * Proxy to the app `Router#route()`
 * Returns a new `Route` instance for the _path_.
 *
 * Routes are isolated middleware stacks for specific paths.
 * See the Route api docs for details.
 *
 * @api public
 */

app.route = function(path){
  this.lazyrouter();
  return this._router.route(path);
};

/**
 * Register the given template engine callback `fn`
 * as `ext`.
 *
 * By default will `require()` the engine based on the
 * file extension. For example if you try to render
 * a "foo.jade" file Express will invoke the following internally:
 *
 *     app.engine('jade', require('jade').__express);
 *
 * For engines that do not provide `.__express` out of the box,
 * or if you wish to "map" a different extension to the template engine
 * you may use this method. For example mapping the EJS template engine to
 * ".html" files:
 *
 *     app.engine('html', require('ejs').renderFile);
 *
 * In this case EJS provides a `.renderFile()` method with
 * the same signature that Express expects: `(path, options, callback)`,
 * though note that it aliases this method as `ejs.__express` internally
 * so if you're using ".ejs" extensions you dont need to do anything.
 *
 * Some template engines do not follow this convention, the
 * [Consolidate.js](https://github.com/visionmedia/consolidate.js)
 * library was created to map all of node's popular template
 * engines to follow this convention, thus allowing them to
 * work seamlessly within Express.
 *
 * @param {String} ext
 * @param {Function} fn
 * @return {app} for chaining
 * @api public
 */

app.engine = function(ext, fn){
  if ('function' != typeof fn) throw new Error('callback function required');
  if ('.' != ext[0]) ext = '.' + ext;
  this.engines[ext] = fn;
  return this;
};

/**
 * Proxy to `Router#param()` with one added api feature. The _name_ parameter
 * can be an array of names.
 *
 * See the Router#param() docs for more details.
 *
 * @param {String|Array} name
 * @param {Function} fn
 * @return {app} for chaining
 * @api public
 */

app.param = function(name, fn){
  var self = this;
  self.lazyrouter();

  if (Array.isArray(name)) {
    name.forEach(function(key) {
      self.param(key, fn);
    });
    return this;
  }

  self._router.param(name, fn);
  return this;
};

/**
 * Assign `setting` to `val`, or return `setting`'s value.
 *
 *    app.set('foo', 'bar');
 *    app.get('foo');
 *    // => "bar"
 *
 * Mounted servers inherit their parent server's settings.
 *
 * @param {String} setting
 * @param {*} [val]
 * @return {Server} for chaining
 * @api public
 */

app.set = function(setting, val){
  if (1 == arguments.length) {
    return this.settings[setting];
  } else {
    this.settings[setting] = val;
    return this;
  }
};

/**
 * Return the app's absolute pathname
 * based on the parent(s) that have
 * mounted it.
 *
 * For example if the application was
 * mounted as "/admin", which itself
 * was mounted as "/blog" then the
 * return value would be "/blog/admin".
 *
 * @return {String}
 * @api private
 */

app.path = function(){
  return this.parent
    ? this.parent.path() + this.mountpath
    : '';
};

/**
 * Check if `setting` is enabled (truthy).
 *
 *    app.enabled('foo')
 *    // => false
 *
 *    app.enable('foo')
 *    app.enabled('foo')
 *    // => true
 *
 * @param {String} setting
 * @return {Boolean}
 * @api public
 */

app.enabled = function(setting){
  return !!this.set(setting);
};

/**
 * Check if `setting` is disabled.
 *
 *    app.disabled('foo')
 *    // => true
 *
 *    app.enable('foo')
 *    app.disabled('foo')
 *    // => false
 *
 * @param {String} setting
 * @return {Boolean}
 * @api public
 */

app.disabled = function(setting){
  return !this.set(setting);
};

/**
 * Enable `setting`.
 *
 * @param {String} setting
 * @return {app} for chaining
 * @api public
 */

app.enable = function(setting){
  return this.set(setting, true);
};

/**
 * Disable `setting`.
 *
 * @param {String} setting
 * @return {app} for chaining
 * @api public
 */

app.disable = function(setting){
  return this.set(setting, false);
};

/**
 * Delegate `.VERB(...)` calls to `router.VERB(...)`.
 */

methods.forEach(function(method){
  app[method] = function(path){
    if ('get' == method && 1 == arguments.length) return this.set(path);

    this.lazyrouter();

    var route = this._router.route(path);
    route[method].apply(route, [].slice.call(arguments, 1));
    return this;
  };
});

/**
 * Special-cased "all" method, applying the given route `path`,
 * middleware, and callback to _every_ HTTP method.
 *
 * @param {String} path
 * @param {Function} ...
 * @return {app} for chaining
 * @api public
 */

app.all = function(path){
  this.lazyrouter();

  var route = this._router.route(path);
  var args = [].slice.call(arguments, 1);
  methods.forEach(function(method){
    route[method].apply(route, args);
  });

  return this;
};

// del -> delete alias

app.del = app.delete;

/**
 * Render the given view `name` name with `options`
 * and a callback accepting an error and the
 * rendered template string.
 *
 * Example:
 *
 *    app.render('email', { name: 'Tobi' }, function(err, html){
 *      // ...
 *    })
 *
 * @param {String} name
 * @param {String|Function} options or fn
 * @param {Function} fn
 * @api public
 */

app.render = function(name, options, fn){
  var opts = {};
  var cache = this.cache;
  var engines = this.engines;
  var view;

  // support callback function as second arg
  if ('function' == typeof options) {
    fn = options, options = {};
  }

  // merge app.locals
  mixin(opts, this.locals);

  // merge options._locals
  if (options._locals) mixin(opts, options._locals);

  // merge options
  mixin(opts, options);

  // set .cache unless explicitly provided
  opts.cache = null == opts.cache
    ? this.enabled('view cache')
    : opts.cache;

  // primed cache
  if (opts.cache) view = cache[name];

  // view
  if (!view) {
    view = new (this.get('view'))(name, {
      defaultEngine: this.get('view engine'),
      root: this.get('views'),
      engines: engines
    });

    if (!view.path) {
      var err = new Error('Failed to lookup view "' + name + '" in views directory "' + view.root + '"');
      err.view = view;
      return fn(err);
    }

    // prime the cache
    if (opts.cache) cache[name] = view;
  }

  // render
  try {
    view.render(opts, fn);
  } catch (err) {
    fn(err);
  }
};

/**
 * Listen for connections.
 *
 * A node `http.Server` is returned, with this
 * application (which is a `Function`) as its
 * callback. If you wish to create both an HTTP
 * and HTTPS server you may do so with the "http"
 * and "https" modules as shown here:
 *
 *    var http = require('http')
 *      , https = require('https')
 *      , express = require('express')
 *      , app = express();
 *
 *    http.createServer(app).listen(80);
 *    https.createServer({ ... }, app).listen(443);
 *
 * @return {http.Server}
 * @api public
 */

app.listen = function(){
  var server = http.createServer(this);
  return server.listen.apply(server, arguments);
};
