web3.js/lib/web3/httpprovider.js

/*
    This file is part of ethereum.js.

    ethereum.js is free software: you can redistribute it and/or modify
    it under the terms of the GNU Lesser General Public License as published by
    the Free Software Foundation, either version 3 of the License, or
    (at your option) any later version.

    ethereum.js is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU Lesser General Public License for more details.

    You should have received a copy of the GNU Lesser General Public License
    along with ethereum.js.  If not, see <http://www.gnu.org/licenses/>.
*/
/** @file httpprovider.js
 * @authors:
 *   Marek Kotewicz <marek@ethdev.com>
 *   Marian Oancea <marian@ethdev.com>
 *   Fabian Vogelsteller <fabian@ethdev.com>
 * @date 2015
 */

"use strict";

var errors = require('./errors');

// workaround to use httpprovider in different envs
var XMLHttpRequest; // jshint ignore: line

// meteor server environment
if (typeof Meteor !== 'undefined' && Meteor.isServer) { // jshint ignore: line
    XMLHttpRequest = Npm.require('xmlhttprequest').XMLHttpRequest; // jshint ignore: line

// browser
} else if (typeof window !== 'undefined' && window.XMLHttpRequest) {
    XMLHttpRequest = window.XMLHttpRequest; // jshint ignore: line

// node
} else {
    XMLHttpRequest = require('xmlhttprequest').XMLHttpRequest; // jshint ignore: line
}

/**
 * HttpProvider should be used to send rpc calls over http
 */
var HttpProvider = function (host) {
    this.host = host || 'http://localhost:8545';
};

/**
 * Should be called to prepare new XMLHttpRequest
 *
 * @method prepareRequest
 * @param {Boolean} true if request should be async
 * @return {XMLHttpRequest} object
 */
HttpProvider.prototype.prepareRequest = function (async) {
    var request = new XMLHttpRequest();
    request.open('POST', this.host, async);
    request.setRequestHeader('Content-Type','application/json');
    return request;
};

/**
 * Should be called to make sync request
 *
 * @method send
 * @param {Object} payload
 * @return {Object} result
 */
HttpProvider.prototype.send = function (payload) {
    var request = this.prepareRequest(false);

    try {
        request.send(JSON.stringify(payload));
    } catch(error) {
        throw errors.InvalidConnection(this.host);
    }

    var result = request.responseText;

    try {
        result = JSON.parse(result);
    } catch(e) {
        throw errors.InvalidResponse(request.responseText);                
    }

    return result;
};

/**
 * Should be used to make async request
 *
 * @method sendAsync
 * @param {Object} payload
 * @param {Function} callback triggered on end with (err, result)
 */
HttpProvider.prototype.sendAsync = function (payload, callback) {
    var request = this.prepareRequest(true); 

    request.onreadystatechange = function() {
        if (request.readyState === 4) {
            var result = request.responseText;
            var error = null;

            try {
                result = JSON.parse(result);
            } catch(e) {
                error = errors.InvalidResponse(request.responseText);                
            }

            callback(error, result);
        }
    };
    
    try {
        request.send(JSON.stringify(payload));
    } catch(error) {
        callback(errors.InvalidConnection(this.host));
    }
};

/**
 * Synchronously tries to make Http request
 *
 * @method isConnected
 * @return {Boolean} returns true if request haven't failed. Otherwise false
 */
HttpProvider.prototype.isConnected = function() {
    try {
        this.send({
            id: 9999999999,
            jsonrpc: '2.0',
            method: 'net_listening',
            params: []
        });
        return true;
    } catch(e) {
        return false;
    }
};

module.exports = HttpProvider;