--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/sat_templates/default/static/websocket.js	Sat Jun 02 17:25:43 2018 +0200
@@ -0,0 +1,131 @@
+/*
+SàT templates: suit of templates for Salut à Toi
+Copyright (C) 2017 Jérôme Poisson (goffi@goffi.org)
+
+This program is free software: you can redistribute it and/or modify
+it under the terms of the GNU Affero General Public License as published by
+the Free Software Foundation, either version 3 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU Affero General Public License for more details.
+
+You should have received a copy of the GNU Affero General Public License
+along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+/* websocket handler */
+
+
+//TODO: retry websocket instead of reload
+function WSHandler(url, token, debug=false) {
+    var socket = new WebSocket(url, 'libervia_page_' + token );
+    var retried = 0;
+
+    var errorHandler = function(error) {
+        if (retried > 20) {
+            console.error("Too many tries, can't start websocket");
+            alert("Dynamic connection with server can't be established, please try to reload this page in a while or contact your service administrator");
+            return;
+        }
+        var delay = Math.floor((Math.random() * 10) + 1) + 30 * Math.min(retried, 6);
+        notifyRetry(delay, function() {
+            retried++;
+            socket = new WebSocket(url, 'libervia_page_' + token );
+            socket.addEventListener('error', errorHandler);
+        });
+    };
+
+    socket.addEventListener('error', errorHandler);
+
+    if (debug) {
+        socket.addEventListener('message', function(event) {
+            console.log('WS in <== ', JSON.parse(event.data));
+        });
+    }
+
+    socket.addEventListener('message', function(event) {
+        try {data = JSON.parse(event.data);}
+        catch (e) {
+            console.warn('invalid websocket message received: %s', e);
+            return;
+        }
+        switch (data.type) {
+            case 'reload':
+                location.reload(true);
+                break;
+            case 'dom':
+                selected_element = document.body.querySelector(data.selectors);
+                switch (data.update_type) {
+                    case 'append':
+                        var template = document.createElement('template');
+                        template.innerHTML = data.html.trim();
+                        new_element = template.content.firstChild;
+                        selected_element.appendChild(new_element);
+                        break;
+                    default:
+                        console.warn('Unknown DOM update type: %s', data.update_type);
+                }
+                break;
+            default:
+                console.warn('Unknown data type: %s', data.type);
+        }
+    });
+
+    socket.addEventListener('open', function (event) {
+        console.log('Websocket opened');
+        retried = 0;
+    }.bind(this));
+
+    this.send = function(data) {
+        if (debug) {
+            console.log('WS out ==> ', data);
+        }
+        socket.send(JSON.stringify(data));
+    };
+
+    function notifyRetry(timeout, retryCb) {
+        /* Show a notification dialog informing the user that server can't be reach
+         * and call retryCb after timeout seconds.
+         * A "retry now" link allows to retry immediately"
+         *
+         * @param timeout(int): delay before retrying, in seconds
+         * @param retryCb(function): function to call when retrying
+         */
+        var startTime = Date.now() / 1000;
+        var retryIntervalID;
+        var notif = document.createElement("div");
+        notif.setAttribute('class', 'notification retry');
+        //FIXME: we use English without translation for now, must be changed when we can use gettext in Libervia pages
+        notif.innerHTML = "<p>Can't reach the server, retrying in <span id='retry_counter'></span> seconds</p><p><a id='retry_now'>retry now</a></p>";
+        document.body.appendChild(notif);
+        var retryCounter = document.getElementById('retry_counter');
+        retryCounter.textContent = timeout;
+
+        var retry = function () {
+            clearInterval(retryIntervalID);
+            notif.parentNode.removeChild(notif);
+            retryCb();
+        };
+
+        var updateTimer = function () {
+            var elapsed = Math.floor(Date.now() / 1000 - startTime);
+            var remaining = timeout - elapsed;
+            if (remaining < 0) {
+                retry();
+            }
+            else {
+                retryCounter.textContent = remaining;
+            }
+        };
+
+        var retryNow = document.getElementById('retry_now');
+        retryNow.addEventListener('click', function(){
+            retry();
+        });
+
+        retryIntervalID = setInterval(updateTimer, 1000);
+    }
+}