setup constructor function of http_client and started minimal work on http_client.request

lib/http_client.js

@@ -1,11 +1,59 @@
 var https = require('https');
+var v8type = require('v8type');
+
 
 var client = function(options){
+    /*
+     * new http_client([options])
+     *
+     * http client used to make requests to datadog api service
+     *
+     * `options` is an optional object of parameters to set:
+     *    {
+     *      'api_key': 'datadog api key',
+     *      'app_key': 'datadog app key',
+     *      'api_version': 'default is v1',
+     *      'api_host': 'default is https://app.datadoghq.com',
+     *    }
+     *
+     * this client also allows you to provide these options as
+     * environment variables instead:
+     *
+     *    api_key: DD_API_KEY
+     *    app_key: DD_APP_KEY
+     *    api_version: DD_API_VERSION
+     *    api_host: DD_API_HOST
+    */
     options = (options)? options : {};
-};
 
-client.prototype.request = function(callback){
+    this.api_key = (options['api_key'])? options['api_key'] : process.env['DD_API_KEY'];
+    if(!this.api_key){
+	throw new Error('`api_key` is not present, either provide `api_key` in `options` or use environment variable `DD_API_KEY`');
+    }
+
+    this.app_key = (options['app_key'])? options['app_key'] : process.env['DD_APP_KEY'];
+    if(!this.api_key){
+	throw new Error('`app_key` is not present, either provide `app_key` in `options` or use environment variable `DD_APP_KEY`');
+    }
+
+    this.api_version = (options['api_version'])? options['api_version'] : process.env['DD_API_VERSION'];
+    if(!this.api_version){
+	this.api_version = 'v1';
+    }
+
+    this.api_host = (options['api_host'])? options['api_host'] : process.env['DD_API_HOST'];
+    if(!this.api_host){
+	this.api_host = 'https://app.datadoghq.com';
+    }
+
+
+};
 
+client.prototype.request = function(method, url, params, callback){
+    if(arguments.length == 3 && v8type.is(arguments[2], v8type.FUNCTION)){
+	params = {};
+	callback = arguments[2];
+    }
 };
 
 return module.exports = client;