xhr.js

/* global window, document, location, Event, setTimeout */
/*
    ## MockXMLHttpRequest

    期望的功能：
    1. 完整地覆盖原生 XHR 的行为
    2. 完整地模拟原生 XHR 的行为
    3. 在发起请求时，自动检测是否需要拦截
    4. 如果不必拦截，则执行原生 XHR 的行为
    5. 如果需要拦截，则执行虚拟 XHR 的行为
    6. 兼容 XMLHttpRequest 和 ActiveXObject
        new window.XMLHttpRequest()
        new window.ActiveXObject("Microsoft.XMLHTTP")

    关键方法的逻辑：
    * new   此时尚无法确定是否需要拦截，所以创建原生 XHR 对象是必须的。
    * open  此时可以取到 URL，可以决定是否进行拦截。
    * send  此时已经确定了请求方式。

    规范：
    http://xhr.spec.whatwg.org/
    http://www.w3.org/TR/XMLHttpRequest2/

    参考实现：
    https://github.com/philikon/MockHttpRequest/blob/master/lib/mock.js
    https://github.com/trek/FakeXMLHttpRequest/blob/master/fake_xml_http_request.js
    https://github.com/ilinsky/xmlhttprequest/blob/master/XMLHttpRequest.js
    https://github.com/firebug/firebug-lite/blob/master/content/lite/xhr.js
    https://github.com/thx/RAP/blob/master/lab/rap.plugin.xinglie.js

    **需不需要全面重写 XMLHttpRequest？**
        http://xhr.spec.whatwg.org/#interface-xmlhttprequest
        关键属性 readyState、status、statusText、response、responseText、responseXML 是 readonly，所以，试图通过修改这些状态，来模拟响应是不可行的。
        因此，唯一的办法是模拟整个 XMLHttpRequest，就像 jQuery 对事件模型的封装。

    // Event handlers
    onloadstart         loadstart
    onprogress          progress
    onabort             abort
    onerror             error
    onload              load
    ontimeout           timeout
    onloadend           loadend
    onreadystatechange  readystatechange
 */

var Util = require('../util')

// 备份原生 XMLHttpRequest
window._XMLHttpRequest = window.XMLHttpRequest
window._ActiveXObject = window.ActiveXObject

/*
    PhantomJS
    TypeError: '[object EventConstructor]' is not a constructor (evaluating 'new Event("readystatechange")')

    https://github.com/bluerail/twitter-bootstrap-rails-confirm/issues/18
    https://github.com/ariya/phantomjs/issues/11289
*/
try {
    new window.Event('custom')
} catch (exception) {
    window.Event = function(type, bubbles, cancelable, detail) {
        var event = document.createEvent('CustomEvent') // MUST be 'CustomEvent'
        event.initCustomEvent(type, bubbles, cancelable, detail)
        return event
    }
}

var XHR_STATES = {
    // The object has been constructed.
    UNSENT: 0,
    // The open() method has been successfully invoked.
    OPENED: 1,
    // All redirects (if any) have been followed and all HTTP headers of the response have been received.
    HEADERS_RECEIVED: 2,
    // The response's body is being received.
    LOADING: 3,
    // The data transfer has been completed or something went wrong during the transfer (e.g. infinite redirects).
    DONE: 4
}

var XHR_EVENTS = 'readystatechange loadstart progress abort error load timeout loadend'.split(' ')
var XHR_REQUEST_PROPERTIES = 'timeout withCredentials'.split(' ')
var XHR_RESPONSE_PROPERTIES = 'readyState responseURL status statusText responseType response responseText responseXML upload'.split(' ')

// https://github.com/trek/FakeXMLHttpRequest/blob/master/fake_xml_http_request.js#L32
var HTTP_STATUS_CODES = {
    100: "Continue",
    101: "Switching Protocols",
    200: "OK",
    201: "Created",
    202: "Accepted",
    203: "Non-Authoritative Information",
    204: "No Content",
    205: "Reset Content",
    206: "Partial Content",
    300: "Multiple Choice",
    301: "Moved Permanently",
    302: "Found",
    303: "See Other",
    304: "Not Modified",
    305: "Use Proxy",
    307: "Temporary Redirect",
    400: "Bad Request",
    401: "Unauthorized",
    402: "Payment Required",
    403: "Forbidden",
    404: "Not Found",
    405: "Method Not Allowed",
    406: "Not Acceptable",
    407: "Proxy Authentication Required",
    408: "Request Timeout",
    409: "Conflict",
    410: "Gone",
    411: "Length Required",
    412: "Precondition Failed",
    413: "Request Entity Too Large",
    414: "Request-URI Too Long",
    415: "Unsupported Media Type",
    416: "Requested Range Not Satisfiable",
    417: "Expectation Failed",
    422: "Unprocessable Entity",
    500: "Internal Server Error",
    501: "Not Implemented",
    502: "Bad Gateway",
    503: "Service Unavailable",
    504: "Gateway Timeout",
    505: "HTTP Version Not Supported"
}

/*
    MockXMLHttpRequest
*/

function MockXMLHttpRequest() {
    // 初始化 custom 对象，用于存储自定义属性
    this.custom = {
        events: {},
        requestHeaders: {},
        responseHeaders: {}
    }
}

MockXMLHttpRequest._settings = {
    timeout: '10-100',
    /*
        timeout: 50,
        timeout: '10-100',
     */
}

MockXMLHttpRequest.setup = function(settings) {
    Util.extend(MockXMLHttpRequest._settings, settings)
    return MockXMLHttpRequest._settings
}

Util.extend(MockXMLHttpRequest, XHR_STATES)
Util.extend(MockXMLHttpRequest.prototype, XHR_STATES)

// 标记当前对象为 MockXMLHttpRequest
MockXMLHttpRequest.prototype.mock = true

// 是否拦截 Ajax 请求
MockXMLHttpRequest.prototype.match = false

// 初始化 Request 相关的属性和方法
Util.extend(MockXMLHttpRequest.prototype, {
    // https://xhr.spec.whatwg.org/#the-open()-method
    // Sets the request method, request URL, and synchronous flag.
    open: function(method, url, async, username, password) {
        var that = this

        Util.extend(this.custom, {
            method: method,
            url: url,
            async: typeof async === 'boolean' ? async : true,
            username: username,
            password: password,
            options: {
                url: url,
                type: method
            }
        })

        this.custom.timeout = function(timeout) {
            if (typeof timeout === 'number') return timeout
            if (typeof timeout === 'string' && !~timeout.indexOf('-')) return parseInt(timeout, 10)
            if (typeof timeout === 'string' && ~timeout.indexOf('-')) {
                var tmp = timeout.split('-')
                var min = parseInt(tmp[0], 10)
                var max = parseInt(tmp[1], 10)
                return Math.round(Math.random() * (max - min)) + min
            }
        }(MockXMLHttpRequest._settings.timeout)

        // 查找与请求参数匹配的数据模板
        var item = find(this.custom.options)

        function handle(event) {
            // 同步属性 NativeXMLHttpRequest => MockXMLHttpRequest
            for (var i = 0; i < XHR_RESPONSE_PROPERTIES.length; i++) {
                try {
                    that[XHR_RESPONSE_PROPERTIES[i]] = xhr[XHR_RESPONSE_PROPERTIES[i]]
                } catch (e) {}
            }
            // 触发 MockXMLHttpRequest 上的同名事件
            that.dispatchEvent(new Event(event.type /*, false, false, that*/ ))
        }

        // 如果未找到匹配的数据模板，则采用原生 XHR 发送请求。
        if (!item) {
            // 创建原生 XHR 对象，调用原生 open()，监听所有原生事件
            var xhr = createNativeXMLHttpRequest()
            this.custom.xhr = xhr

            // 初始化所有事件，用于监听原生 XHR 对象的事件
            for (var i = 0; i < XHR_EVENTS.length; i++) {
                xhr.addEventListener(XHR_EVENTS[i], handle)
            }

            // xhr.open()
            if (username) xhr.open(method, url, async, username, password)
            else xhr.open(method, url, async)

            // 同步属性 MockXMLHttpRequest => NativeXMLHttpRequest
            for (var j = 0; j < XHR_REQUEST_PROPERTIES.length; j++) {
                try {
                    xhr[XHR_REQUEST_PROPERTIES[j]] = that[XHR_REQUEST_PROPERTIES[j]]
                } catch (e) {}
            }

            return
        }

        // 找到了匹配的数据模板，开始拦截 XHR 请求
        this.match = true
        this.custom.template = item
        this.readyState = MockXMLHttpRequest.OPENED
        this.dispatchEvent(new Event('readystatechange' /*, false, false, this*/ ))
    },
    // https://xhr.spec.whatwg.org/#the-setrequestheader()-method
    // Combines a header in author request headers.
    setRequestHeader: function(name, value) {
        // 原生 XHR
        if (!this.match) {
            this.custom.xhr.setRequestHeader(name, value)
            return
        }

        // 拦截 XHR
        var requestHeaders = this.custom.requestHeaders
        if (requestHeaders[name]) requestHeaders[name] += ',' + value
        else requestHeaders[name] = value
    },
    timeout: 0,
    withCredentials: false,
    upload: {},
    // https://xhr.spec.whatwg.org/#the-send()-method
    // Initiates the request.
    send: function send(data) {
        var that = this
        this.custom.options.body = data

        // 原生 XHR
        if (!this.match) {
            this.custom.xhr.send(data)
            return
        }

        // 拦截 XHR

        // X-Requested-With header
        this.setRequestHeader('X-Requested-With', 'MockXMLHttpRequest')

        // loadstart The fetch initiates.
        this.dispatchEvent(new Event('loadstart' /*, false, false, this*/ ))

        if (this.custom.async) setTimeout(done, this.custom.timeout) // 异步
        else done() // 同步

        function done() {
            that.readyState = MockXMLHttpRequest.HEADERS_RECEIVED
            that.dispatchEvent(new Event('readystatechange' /*, false, false, that*/ ))
            that.readyState = MockXMLHttpRequest.LOADING
            that.dispatchEvent(new Event('readystatechange' /*, false, false, that*/ ))

            that.status = 200
            that.statusText = HTTP_STATUS_CODES[200]

            // fix #92 #93 by @qddegtya
            that.response = that.responseText = JSON.stringify(
                convert(that.custom.template, that.custom.options),
                null, 4
            )

            that.readyState = MockXMLHttpRequest.DONE
            that.dispatchEvent(new Event('readystatechange' /*, false, false, that*/ ))
            that.dispatchEvent(new Event('load' /*, false, false, that*/ ));
            that.dispatchEvent(new Event('loadend' /*, false, false, that*/ ));
        }
    },
    // https://xhr.spec.whatwg.org/#the-abort()-method
    // Cancels any network activity.
    abort: function abort() {
        // 原生 XHR
        if (!this.match) {
            this.custom.xhr.abort()
            return
        }

        // 拦截 XHR
        this.readyState = MockXMLHttpRequest.UNSENT
        this.dispatchEvent(new Event('abort', false, false, this))
        this.dispatchEvent(new Event('error', false, false, this))
    }
})

// 初始化 Response 相关的属性和方法
Util.extend(MockXMLHttpRequest.prototype, {
    responseURL: '',
    status: MockXMLHttpRequest.UNSENT,
    statusText: '',
    // https://xhr.spec.whatwg.org/#the-getresponseheader()-method
    getResponseHeader: function(name) {
        // 原生 XHR
        if (!this.match) {
            return this.custom.xhr.getResponseHeader(name)
        }

        // 拦截 XHR
        return this.custom.responseHeaders[name.toLowerCase()]
    },
    // https://xhr.spec.whatwg.org/#the-getallresponseheaders()-method
    // http://www.utf8-chartable.de/
    getAllResponseHeaders: function() {
        // 原生 XHR
        if (!this.match) {
            return this.custom.xhr.getAllResponseHeaders()
        }

        // 拦截 XHR
        var responseHeaders = this.custom.responseHeaders
        var headers = ''
        for (var h in responseHeaders) {
            if (!responseHeaders.hasOwnProperty(h)) continue
            headers += h + ': ' + responseHeaders[h] + '\r\n'
        }
        return headers
    },
    overrideMimeType: function( /*mime*/ ) {},
    responseType: '', // '', 'text', 'arraybuffer', 'blob', 'document', 'json'
    response: null,
    responseText: '',
    responseXML: null
})

// EventTarget
Util.extend(MockXMLHttpRequest.prototype, {
    addEventListener: function addEventListener(type, handle) {
        var events = this.custom.events
        if (!events[type]) events[type] = []
        events[type].push(handle)
    },
    removeEventListener: function removeEventListener(type, handle) {
        var handles = this.custom.events[type] || []
        for (var i = 0; i < handles.length; i++) {
            if (handles[i] === handle) {
                handles.splice(i--, 1)
            }
        }
    },
    dispatchEvent: function dispatchEvent(event) {
        var handles = this.custom.events[event.type] || []
        for (var i = 0; i < handles.length; i++) {
            handles[i].call(this, event)
        }

        var ontype = 'on' + event.type
        if (this[ontype]) this[ontype](event)
    }
})

// Inspired by jQuery
function createNativeXMLHttpRequest() {
    var isLocal = function() {
        var rlocalProtocol = /^(?:about|app|app-storage|.+-extension|file|res|widget):$/
        var rurl = /^([\w.+-]+:)(?:\/\/([^\/?#:]*)(?::(\d+)|)|)/
        var ajaxLocation = location.href
        var ajaxLocParts = rurl.exec(ajaxLocation.toLowerCase()) || []
        return rlocalProtocol.test(ajaxLocParts[1])
    }()

    return window.ActiveXObject ?
        (!isLocal && createStandardXHR() || createActiveXHR()) : createStandardXHR()

    function createStandardXHR() {
        try {
            return new window._XMLHttpRequest();
        } catch (e) {}
    }

    function createActiveXHR() {
        try {
            return new window._ActiveXObject("Microsoft.XMLHTTP");
        } catch (e) {}
    }
}


// 查找与请求参数匹配的数据模板：URL，Type
function find(options) {

    for (var sUrlType in MockXMLHttpRequest.Mock._mocked) {
        var item = MockXMLHttpRequest.Mock._mocked[sUrlType]
        if (
            (!item.rurl || match(item.rurl, options.url)) &&
            (!item.rtype || match(item.rtype, options.type.toLowerCase()))
        ) {
            // console.log('[mock]', options.url, '>', item.rurl)
            return item
        }
    }

    function match(expected, actual) {
        if (Util.type(expected) === 'string') {
            return expected === actual
        }
        if (Util.type(expected) === 'regexp') {
            return expected.test(actual)
        }
    }

}

// 数据模板 ＝> 响应数据
function convert(item, options) {
    return Util.isFunction(item.template) ?
        item.template(options) : MockXMLHttpRequest.Mock.mock(item.template)
}

module.exports = MockXMLHttpRequest