var origin = require('./origin.js');
var constants = require('./constants.js');

exports.handler = function(options) {

  return function(req, res, next) {
    var originHeader = req.headers['origin'];

    // If either no origin was set, or the origin isn't supported, continue
    // without setting any headers
    if (!originHeader || !origin.match(originHeader, options.origins)) {
      return next();
    }

    // if match was found, let's set some headers.
    res.setHeader(constants['AC_ALLOW_ORIGIN'], originHeader);
    res.setHeader(constants['STR_VARY'], constants['STR_ORIGIN']);
    if(options.credentials) {
      res.setHeader(constants['AC_ALLOW_CREDS'], 'true');
    }
    res.setHeader(constants['AC_EXPOSE_HEADERS'],
      options.exposeHeaders.join(', '));

    return next();
  };

};