mjackson/mach

var normalizeHeaderName = require('../utils/normalizeHeaderName');

/**
 * A middleware that overrides the method of the request to a value that was
 * given either in a request parameter or a request header. Can be useful when
 * you need to use HTTP methods other than GET and POST with clients that don't
 * support them, like web browsers.
 *
 * For example, you could use the following HTML form:
 *
 *   <form method="POST" action="/">
 *     <input type="hidden" name="_method" value="PUT">
 *   </form>
 *
 * with an app that uses methodOverride:
 *
 *   var app = mach.stack();
 *   app.use(mach.params);
 *   app.use(mach.methodOverride);
 *   app.run(function (request) {
 *     return request.method; // PUT
 *   });
 *
 * Note: When using mach.methodOverride with POST parameters you need to put
 * mach.params in front of it so that the request parameters will be available.
 *
 * Options may be any of the following:
 *
 * - paramName        The name of the request param that contains the
 *                    request method. Defaults to "_method"
 * - headerName       The name of the HTTP header that will contain the
 *                    request method. This allows you to put the request
 *                    method in an HTTP header instead of a request param.
 *                    Defaults to "X-Http-Method-Override"
 */
function methodOverride(app, options) {
  options = options || {};

  if (typeof options === 'string')
    options = { paramName: options };

  var paramName = options.paramName || '_method';
  var headerName = normalizeHeaderName(options.headerName || 'X-Http-Method-Override');

  return function (conn) {
    var method;
    if (conn.request.headers[headerName]) {
      method = conn.request.headers[headerName];
    } else if (!conn.params) {
      conn.onError(new Error('No params! Use mach.params in front of mach.methodOverride'));
    } else if (conn.params[paramName]) {
      method = conn.params[paramName];

      // If multiple _method parameters were used, use the last one.
      if (Array.isArray(method))
        method = method[method.length - 1];
    }

    if (method)
      conn.method = method.toUpperCase();

    return conn.call(app);
  };
}

module.exports = methodOverride;