index.js

'use strict';

var join = require('url').resolve;
var iconv = require('iconv-lite');
var coRequest = require('co-request');

module.exports = function(options) {
  options || (options = {});
  var request = coRequest.defaults({ jar: options.jar === true });

  if (!(options.host || options.map || options.url)) {
    throw new Error('miss options');
  }

  return function* proxy(next) {
    var url = resolve(this.path, options);

    if(typeof options.suppressRequestHeaders === 'object'){
      options.suppressRequestHeaders.forEach(function(h, i){
        options.suppressRequestHeaders[i] = h.toLowerCase();
      });
    }

    var suppressResponseHeaders = [];  // We should not be overwriting the options object!
    if(typeof options.suppressResponseHeaders === 'object'){
      options.suppressResponseHeaders.forEach(function(h, i){
        suppressResponseHeaders.push(h.toLowerCase());
      });
    }

    // don't match
    if (!url) {
      return yield* next;
    }

    // if match option supplied, restrict proxy to that match
    if (options.match) {
      if (!this.path.match(options.match)) {
        return yield* next;
      }
    }
    
    var parsedBody = getParsedBody(this);

    var opt = {
      url: url + (this.querystring ? '?' + this.querystring : ''),
      headers: this.header,
      encoding: null,
      followRedirect: options.followRedirect === false ? false : true,
      method: this.method,
      body: parsedBody,
    };

    // set 'Host' header to options.host (without protocol prefix), strip trailing slash
    if (options.host) opt.headers.host = options.host.slice(options.host.indexOf('://')+3).replace(/\/$/,'');

    if (options.requestOptions) {
      if (typeof options.requestOptions === 'function') {
        opt = options.requestOptions(this.request, opt);
      } else {
        Object.keys(options.requestOptions).forEach(function (option) { opt[option] = options.requestOptions[option]; });
      }
    }

    for(name in opt.headers){
      if(options.suppressRequestHeaders && options.suppressRequestHeaders.indexOf(name.toLowerCase()) >= 0){
        delete opt.headers[name];
      }
    }

    var requestThunk = request(opt);

    if (parsedBody) {
      var res = yield requestThunk;
    } else {
      // Is there a better way?
      // https://github.com/leukhin/co-request/issues/11
      var res = yield pipeRequest(this.req, requestThunk);
    }

    this.status = res.statusCode;
    for (var name in res.headers) {
      // http://stackoverflow.com/questions/35525715/http-get-parse-error-code-hpe-unexpected-content-length
      if(suppressResponseHeaders.indexOf(name.toLowerCase())>=0){
        continue;
      }
      if (name === 'transfer-encoding') {
        continue;
      }
      this.set(name, res.headers[name]);
    }

    if (options.encoding === 'gbk') {
      this.body = iconv.decode(res.body, 'gbk');
      return;
    }

    this.body = res.body;

    if (options.yieldNext) {
      yield next;
    }
  };
};


function resolve(path, options) {
  var url = options.url;
  if (url) {
    if (!/^http/.test(url)) {
      url = options.host ? join(options.host, url) : null;
    }
    return ignoreQuery(url);
  }

  if (typeof options.map === 'object') {
    if (options.map && options.map[path]) {
      path = ignoreQuery(options.map[path]);
    }
  } else if (typeof options.map === 'function') {
    path = options.map(path);
  }

  return options.host ? join(options.host, path) : null;
}

function ignoreQuery(url) {
  return url ? url.split('?')[0] : null;
}

function getParsedBody(ctx){
  var body = ctx.request.body;
  if (body === undefined || body === null){
    return undefined;
  }
  var contentType = ctx.request.header['content-type'];
  if (!Buffer.isBuffer(body) && typeof body !== 'string'){
    if (contentType && contentType.indexOf('json') !== -1){
      body = JSON.stringify(body);
    } else {
      body = body + '';
    }
  }
  return body;
}

function pipeRequest(readable, requestThunk){
  return function(cb){
    readable.pipe(requestThunk(cb));
  }
}