added query API

WhatsAppWeb.Query.js

@@ -0,0 +1,81 @@
+/* 
+	Contains the code for sending queries to WhatsApp 
+*/
+module.exports = function(WhatsAppWeb) {
+    // check if given number is registered on WhatsApp
+    WhatsAppWeb.prototype.isOnWhatsApp = function (jid) {
+		return this.query(["query", "exist", jid])
+	}
+	// check the presence status of a given jid
+	WhatsAppWeb.prototype.requestPresenceUpdate = function (jid) {
+		return this.query(["action","presence","subscribe",jid])
+    }
+    // check the presence status of a given jid
+	WhatsAppWeb.prototype.getStatus = function (jid) {
+		return this.query(["query","Status",jid])
+    }
+    // check the presence status of a given jid
+	WhatsAppWeb.prototype.getProfilePicture = function (jid) {
+        if (!jid) {
+            jid = this.userMetaData.id
+        }
+		return this.query(["query","ProfilePicThumb",jid])
+    }
+    // query all the contacts
+    WhatsAppWeb.prototype.getContactList = function () {
+        const json = [
+            "query",
+            {epoch: this.msgCount.toString(), type: "contacts"},
+            null
+        ]
+        return this.query(json, true) // this has to be an encrypted query
+    }
+    // load messages from a group or sender
+    WhatsAppWeb.prototype.getMessages = function (jid, count, beforeMessage=null) {
+        // construct JSON
+        let json = [
+            "query",
+            { 
+                epoch: this.msgCount.toString(), 
+                type: "message", 
+                jid: jid,
+                kind: "before", 
+                owner: "true",
+                count: count.toString()
+            },
+            null
+        ]
+        // if we have some index before which we want to query
+        if (beforeMessage) {
+            json[1].index = beforeMessage.id
+            json[1].owner = beforeMessage.fromMe ? "true" : "false"
+        }
+        return this.query(json, true)
+    }
+    // loads all the conversation you've had with given ID
+    WhatsAppWeb.prototype.getAllMessages = function (jid, onMessage, chunkSize=25) {
+        var offsetID = null
+
+        const loadMessage = () => {
+            return this.getMessages(jid, chunkSize, offsetID)
+            .then (json => {
+                if (json[2]) {
+                    // callback with most recent message first (descending order of date)
+                    for (var i = json[2].length-1; i >= 0;i--) {
+                        onMessage(json[2][i][2])
+                    }
+                    // if there are still more messages
+                    if (json[2].length >= chunkSize) {
+                        offsetID = json[2][0][2].key // get the oldest message
+                        return new Promise ( (resolve, reject) => {
+                            // send query after 200 ms
+                            setTimeout( () => loadMessage().then (resolve).catch(reject), 200)
+                        } )
+                    }  
+                }
+            })
+        } 
+
+        return loadMessage()
+    }
+}