batch hack

CRMWebAPI.prototype.batch = function (entity, fetchXml, QueryOptions) {
    const self = this

    // build the body
    var body = '--batch_contactfetch\n'
    body += 'Content-Type: application/http\n'
    body += 'Content-Transfer-Encoding: binary\n'
    body += '\n'
    body += 'GET ' + self.config.APIUrl + `${entity}?fetchXml=${encodeURIComponent(fetchXml)} HTTP/1.1\n`
    body += 'Content-Type: application/json\n'
    body += 'OData-Version: 4.0\n'
    body += 'OData-MaxVersion: 4.0\n'
    body += '\n'
    body += '--batch_contactfetch--'

    return new Promise(function (resolve, reject) {
        const url = self._BuildQueryURL("$batch", QueryOptions, self.config)
        self._log('ODataUrl',url)
        //self._GetHttpRequest(self.config, "POST", url, { // won't work, additive headers
        self._hack(self.config, "POST", url, {
            'data': body,
            headers: {
                "Content-Type": "multipart/mixed;boundary=batch_contactfetch"
            }
        }, function (err, res) { // callback
            if (err != false) {
                self._log('Errors','batch error',res)
                reject(res)
            } else {
                //if(DEBUG) console.log("raw r", res)
                var data = JSON.parse(self._sliceBatchResponse(res.response), self._DateReviver)
                if(data.error) {
                    // its really an error
                    self._log('Errors','batch error', res)
                    reject(data.error)
                    return
                }
                var nextLink = data['@odata.nextLink']
                var recordCount = data['@odata.count']
                var response = {
                    List: data.value,
                    Count: recordCount
                }
                if ((QueryOptions != null) && (QueryOptions.RecordAction != null))
                {
                    response.List.forEach(function(record){
                        QueryOptions.RecordAction(record)
                    });
                    response.List = [];
                }
                if ((QueryOptions != null) && (QueryOptions.PageAction != null))
                {
                    QueryOptions.PageAction(response.List)
                response.List = []
        }
        if (!nextLink) {
                    resolve(response)
                } else {
                    if(DEBUG) console.log("NEXT LINK BUT NEED TO IMPLEMENT WHILST!!!")
                    if(DEBUG) console.log("response", data)
                    resolve(response)
                    // the lib has page processing code here...copy and paste it!
                }
            }
        })
    })
}

CRMWebAPI.prototype._hack = function (config, method, url, payload, callback) {
    var self = this;
    var req = new XMLHttpRequest();
    //req.open(method, encodeURI(url), true);
    req.open(method, url, true);
    if (config.AccessToken != null) req.setRequestHeader("Authorization", "Bearer " + config.AccessToken);
    req.setRequestHeader("Accept", "application/json");
    req.setRequestHeader("OData-MaxVersion", "4.0");
    req.setRequestHeader("OData-Version", "4.0");
    if (config.callerId) req.setRequestHeader("MSCRMCallerID", config.callerId);
    if (config.CallerID) req.setRequestHeader("MSCRMCallerID", config.CallerID);
    if (['POST', 'PUT', 'PATCH'].indexOf(method) >= 0) {
    req.setRequestHeader("Content-Length", payload.data.length);
    //req.setRequestHeader("Content-Type", "application/json");
    }
    if (payload.headers !== 'undefined') {
    for (var name in payload.headers) {
        req.setRequestHeader(name, payload.headers[name]);
    }
    }
    req.onreadystatechange = function () {
    if (this.readyState == 4 /* complete */ ) {
        req.onreadystatechange = null;
        if ((this.status >= 200) && (this.status < 300)) {
        callback(false, {
            'response': this.response,
            'headers': self.parseResponseHeaders(this.getAllResponseHeaders())
        });
        } else {
        callback(true, this)
        }
    }
    };
    if (['POST', 'PUT', 'PATCH'].indexOf(method) >= 0) {
    req.send(payload.data);
    } else {
    req.send();
    }
}

CRMWebAPI.prototype._sliceBatchResponse = function(response) {
    const start = response.indexOf("{")
    const end = response.lastIndexOf("}")+1
    //console.log("stats", start, end, response[start], response[end-1])
    //console.log("parsing", response.substring(start, end))
    return response.substring(start, end)
}