--- a/svghmi/svghmi.js	Fri Oct 11 12:03:14 2019 +0200
+++ b/svghmi/svghmi.js	Tue Oct 15 17:14:48 2019 +0200
@@ -1,26 +1,153 @@
 // svghmi.js
 
-(function(){
-    // Open WebSocket to relative "/ws" address
-    var ws = new WebSocket(window.location.href.replace(/^http(s?:\/\/[^\/]*)\/.*$/, 'ws$1/ws'));
+function dispatch_value(index, value) {
+    console.log("dispatch_value("+index+value+")");
+};
 
-    // Register message reception handler 
-    ws.onmessage = function (evt) {
-        // TODO : dispatch and cache hmi tree updates
+// Open WebSocket to relative "/ws" address
+var ws = new WebSocket(window.location.href.replace(/^http(s?:\/\/[^\/]*)\/.*$/, 'ws$1/ws'));
+ws.binaryType = 'arraybuffer';
 
-        var received_msg = evt.data;
-        // TODO : check for hmitree hash header
-        //        if not matching, reload page
-        alert("Message is received..."+received_msg); 
+const dvgetters = {
+    INT: [DataView.prototype.getInt16, 2],
+    BOOL: [DataView.prototype.getInt8, 1]
+    /* TODO */
+};
+
+// Register message reception handler 
+ws.onmessage = function (evt) {
+
+    let data = evt.data;
+    let dv = new DataView(data);
+    let i = 0;
+    for(let hash_int of hmi_hash) {
+        if(hash_int != dv.getUint8(i)){
+            console.log("Recv non maching hash. Reload.");
+
+            // 1003 is for "Unsupported Data"
+            ws.close(1003,"Hash doesn't match");
+
+            // TODO : remove debug alert ?
+            alert("HMI will be reloaded.");
+
+            // force reload ignoring cache
+            location.reload(true);
+        };
+        i++;
     };
 
-    // Once connection established
-    ws.onopen = function (evt) {
-        // TODO : enable the HMI (was previously offline, or just starts)
-        //        show main page
+    while(i < data.length){
+        let index = dv.getUint32(i);
+        i += 4;
+        let iectype = hmitree_types[index];
+        let [dvgetter, bytesize] = dvgetters[iectypes];
+        value = dvgetter.call(dv,i);
+        dispatch_value(index, value);
+        i += bytesize;
+    };
+};
 
 
-        // TODO : prefix with hmitree hash header
-        ws.send("test");
+function send_blob(data) {
+    if(data.length > 0) {
+        ws.send(new Blob([
+            new Uint8Array(hmi_hash), 
+            data]));
     };
-})();
+};
+
+const typedarray_types = {
+    INT: Int16Array,
+    BOOL: Uint8Array
+    /* TODO */
+};
+
+function send_reset() {
+    send_blob(new Uint8Array([1])); /* reset = 1 */
+};
+
+// subscription state, as it should be in hmi server
+// hmitree indexed array of integers
+var subscriptions =  hmitree_types.map(_ignored => 0);
+
+// subscription state as needed by widget now
+// hmitree indexed array of Sets of widgets objects
+var subscribers = hmitree_types.map(_ignored => new Set());
+
+function update_subscriptions() {
+    let delta = [];
+    for(let index = 0; index < subscribers.length; index++){
+        let widgets = subscribers[index];
+
+        // periods are in ms
+        let previous_period = subscriptions[index];
+
+        let new_period;
+        if(widgets.size > 0) {
+            let maxfreq = 0;
+            for(let widget of widgets)
+                if(maxfreq < widgets.frequency)
+                    maxfreq = widgets.frequency;
+
+            new_period = 1000/maxfreq;
+        } else {
+            new_period = 0;
+        }
+
+        if(previous_period != new_period) {
+            subscriptions[index] = new_period;
+            delta.push([
+                new Uint8Array([2]), /* subscribe = 2 */
+                new Uint32Array([index]), 
+                new Uint16Array([new_period])]);
+        }
+        
+    }
+    send_blob(delta);
+};
+
+function update_value(index, value) {
+    iectype = hmitree_types[index];
+    jstype = typedarray_types[iectypes];
+    send_blob([
+        new Uint8Array([0]),  /* setval = 0 */
+        new jstype([value])
+        ]);
+
+};
+
+var current_page;
+
+function switch_page(page_name) {
+    let old_desc = page_desc[current_page];
+    let new_desc = page_desc[page_name];
+    /* TODO hide / show widgets */
+    /* TODO move viewport */
+
+    /* remove subsribers of previous page if any */
+    if(old_desc) for(let widget of old_desc.widgets){
+        for(let index of widget.indexes){
+            subscribers[index].delete(widget);
+        }
+    }
+    /* add new subsribers if any */
+    if(new_desc) for(let widget of new_desc.widgets){
+        for(let index of widget.indexes){
+            subscribers[index].add(widget);
+        }
+    }
+
+    current_page = page_name;
+
+    update_subscriptions();
+};
+
+
+// Once connection established
+ws.onopen = function (evt) {
+    send_reset();
+    // show main page
+    switch_page(default_page);
+
+};
+