var utils   = require('./utils'),
    helpers = require('./helpers'),
    custom  = require('./custom'),
    errors  = require('./errors'),
    connect = require('express/node_modules/connect'),
    models  = require('./models'),
    config  = require('./config');

// Custom middleware used by the application.
module.exports = {
  // Transparently handle JSONP. Although this does require wrapping the
  // Request#send() method which is a bit nasty. Other alternative is to
  // always pass the response on and include this middleware after the
  // routes.
  jsonp: function () {
    return function (req, res, next) {
      var _send = res.send;
      res.send = function (body) {
        var callback = req.param('callback'),
            isJSONP  = res.get('Content-Type') === 'application/json' && callback;

        if (body && req.method !== 'HEAD' && isJSONP) {
          res.contentType('js');
          body = callback + '(' + body.toString().trim() + ');';
        }
        _send.call(this, body);
      };
      next();
    };
  },
  // Check for ajax requests and set the Request/Response#ajax flag to true.
  ajax: function () {
    return function (req, res, next) {
      req.ajax = res.ajax = utils.isAjax(req);

      // if ((req.get('X-Stream') || '').toLowerCase() === 'true') {
      //   req.ajax = false;
      // }

      next();
    };
  },
  // Add relevant CORS headers for the application.
  cors: function () {
    return function (req, res, next) {
      var headers = req.header('Access-Control-Request-Headers');
      var origin = req.header('Origin');

      if (req.method === 'OPTIONS' || (req.method === 'GET' && utils.isAjax(req)) || (req.method === 'GET' && req.headers.origin)) {
        res.header({
          'Access-Control-Allow-Origin':  origin,
          'Access-Control-Allow-Headers': headers
        });
        req.cors = true;
      }

      if (req.method === 'OPTIONS') {
        res.send(204);
      } else {
        next();
      }
    };
  },
  flash: function () {
    function flash(key, message) {
      var cache = this.session.flash = this.session.flash || {},
          value;

      if (arguments.length === 2) {
        cache[key] = message;
        return this;
      } else if (arguments.length === 1) {
        value = cache[key];
        delete cache[key];
        return value;
      }

      this.session.flash = {};
      return cache;
    }

    return function (req, res, next) {
      req.flash = res.flash = flash.bind(req);

      req.flash.INFO = 'info';
      req.flash.ERROR = 'error';

      next();
    };
  },
  // Redirect urls with trailing slashes to their non-trailing counterpart,
  // requires the "strict routing" setting to be false.
  noslashes: function () {
    return function (req, res, next) {
      if (req.path !== '/' && req.originalUrl.slice(-1) === '/') {
        return res.redirect(301, req.originalUrl.slice(0, -1));
      }
      next();
    };
  },
  // monkey patch for express' own csrf method, so we can ignore specific url patterns
  csrf: function (options) {
    var ignore = options.ignore || [],
        csrf = connect.csrf(options),
        always = {OPTIONS: 1, GET: 1, HEAD: 1};

    return function (req, res, next) {
      if (always[req.method]) {
        return csrf(req, res, next);
      } else {
        var skipCSRF = false;
        ignore.forEach(function(matcher) {
          if (typeof matcher === 'string') {
            if (matcher == req.url) {
              skipCSRF = true;
            }
          } else {
            // regular expression matcher
            if (req.url.match(matcher)) {
              skipCSRF = true;
            }
          }
        });

        if (skipCSRF) {
          next();
        } else {
          return csrf(req, res, next);
        }
      }
    };
  },
  // Checks for a subdomain in the current url, if found it sets the
  // req.subdomain property. This supports existing behaviour that allows
  // subdomains to load custom config files.
  subdomain: function (app) {
    return function (req, res, next) {
      var apphost = app.set('url host').split(':')[0],
          host = req.header('Host', ''),
          offset = host.indexOf(apphost);

      if (offset) {
        // Slice the host from the subdomain and subtract 1 for
        // trailing . on the subdomain.
        req.subdomain = host.slice(0, offset - 1);
      }
      next();
    };
  },

  // Limit the file size that can be uploaded.
  limitContentLength: function (options) {
    // Parse a string representing a file size and convert it into bytes.
    // A number on it's own will be assumed to be bytes. A multiple such as
    // "k" or "m" can be appended to the string to handle larger numbers. This
    // is case insensitive and uses powers of 1024 rather than (1000).
    // So both 1kB and 1kb == 1024.
    function parseLimit(string) {
      var matches = ('' + string).toLowerCase().match(regexp),
          bytes = null, power;

      if (matches) {
        bytes = parseFloat(matches[1]);
        power = powers[matches[2]];

        if (bytes && power) {
          bytes = Math.pow(bytes * 1024, power);
        }
      }

      return bytes || null;
    }

    var powers = { k: 1, m: 2, g: 3, t: 4 },
        regexp = /^(\d+(?:.\d+)?)\s*([kmgt]?)b?$/,
        limit  = options && parseLimit(options.limit);

    return function (req, res, next) {
      if (limit) {
        var contentLength = parseInt(req.header('Content-Length', 0), 10),
            message = 'Sorry, the content you have uploaded is larger than JS Bin can handle. Max size is ' + options.limit;

        if (limit && contentLength > limit) {
          return next(new errors.RequestEntityTooLarge(message));
        }
      }
      next();
    };
  },

  // detect if this is an API request and add flag isApi to the request object
  api: function(options) {
    return function (req, res, next) {
      var apiKey,
          userModel = models.createModels(options.app.store).user;

      if (req.url.indexOf('/api') === 0) {
        req.isApi = true;

        if (config.api.requireSSL) {
          if (!req.secure && (String(req.headers['x-forwarded-proto']).toLowerCase() !== "https") ) {
            res.status(403); // forbidden
            res.json({ error: 'All API requests must be made over SSL/TLS' });
            return;
          }
        }

        if (req.query.api_key) {
          apiKey = req.query.api_key;
        } else if (req.headers.authorization) {
          apiKey = req.headers.authorization.replace(/token\s/,'');
        }

        if (config.api.allowAnonymous || (config.api.allowReadOnly && req.method === 'GET')) {
          next();
        } else {
          if (!apiKey) {
            res.status(403); // forbidden
            res.json({ error: 'You need to provide a valid API key when using this API' });
          } else {
            userModel.loadByApiKey(apiKey, function (err, user) {
              if (err) {
                return next(err);
              }

              if (user) {
                req.session.user = user;
                next();
              } else {
                res.status(403); // forbidden
                res.json({ error: 'The API key you provided is not valid' });
              }
            });
          }
        }
      } else {
        next();
      }
    };
  }
};