[IMP] im_livechat: ensure that visitors always gets the same operator

Task #1919871

Purpose
=======

If a visitor comes on the website and launches a livechat, it will be randomly assigned operator A.
If he comes the next day and opens a livechat again, we want him to have the same operator if he's available.

To handle that use case, we added a cookie that stores the "previous operator id" information for 7 days.

3 files changed, 48 insertions, 4 deletions

diff --git a/addons/im_livechat/controllers/main.py b/addons/im_livechat/controllers/main.py
index d87cf2329cb..5703563e95d 100644
--- a/addons/im_livechat/controllers/main.py
+++ b/addons/im_livechat/controllers/main.py
@@ -80,7 +80,7 @@ class LivechatController(http.Controller):
         }
 
     @http.route('/im_livechat/get_session', type="json", auth='public', cors="*")
-    def get_session(self, channel_id, anonymous_name, **kwargs):
+    def get_session(self, channel_id, anonymous_name, previous_operator_id=None, **kwargs):
         user_id = None
         country_id = None
         # if the user is identifiy (eg: portal user on the frontend), don't use the anonymous name. The user will be added to session.
@@ -94,7 +94,11 @@ class LivechatController(http.Controller):
             country = request.env['res.country'].sudo().search([('code', '=', country_code)], limit=1) if country_code else None
             if country:
                 anonymous_name, country_id = _("%s (%s)") % (anonymous_name, country.name), country.id
-        return request.env["im_livechat.channel"].with_context(lang=False).sudo().browse(channel_id)._get_mail_channel(anonymous_name, user_id, country_id)
+
+        if previous_operator_id:
+            previous_operator_id = int(previous_operator_id)
+
+        return request.env["im_livechat.channel"].with_context(lang=False).sudo().browse(channel_id)._get_mail_channel(anonymous_name, previous_operator_id, user_id, country_id)
 
     @http.route('/im_livechat/feedback', type='json', auth='public', cors="*")
     def feedback(self, uuid, rate, reason=None, **kwargs):
diff --git a/addons/im_livechat/models/im_livechat_channel.py b/addons/im_livechat/models/im_livechat_channel.py
index 4a682c912f1..6a568bbb269 100644
--- a/addons/im_livechat/models/im_livechat_channel.py
+++ b/addons/im_livechat/models/im_livechat_channel.py
@@ -132,19 +132,33 @@ class ImLivechatChannel(models.Model):
         return self.user_ids.filtered(lambda user: user.im_status == 'online')
 
     @api.multi
-    def _get_mail_channel(self, anonymous_name, user_id=None, country_id=None):
+    def _get_mail_channel(self, anonymous_name, previous_operator_id=None, user_id=None, country_id=None):
         """ Return a mail.channel given a livechat channel. It creates one with a connected operator, or return false otherwise
             :param anonymous_name : the name of the anonymous person of the channel
+            :param previous_operator_id : partner_id.id of the previous operator that this visitor had in the past
             :param user_id : the id of the logged in visitor, if any
             :param country_code : the country of the anonymous person of the channel
             :type anonymous_name : str
             :return : channel header
             :rtype : dict
+
+            If this visitor already had an operator within the last 7 days (information stored with the 'im_livechat_previous_operator_pid' cookie),
+            the system will first try to assign that operator if he's available (to improve user experience).
         """
         self.ensure_one()
-        operator = self._get_random_operator()
+
+        operator = False
+        if previous_operator_id:
+            available_users = self._get_available_users()
+            # previous_operator_id is the partner_id of the previous operator, need to convert to user
+            if previous_operator_id in available_users.mapped('partner_id').ids:
+                operator = next(available_user for available_user in available_users if available_user.partner_id.id == previous_operator_id)
         if not operator:
+            operator = self._get_random_operator()
+        if not operator:
+            # no one available
             return False
+
         operator_partner_id = operator.partner_id.id
         # partner to add to the mail.channel
         channel_partner_to_add = [(4, operator_partner_id)]
diff --git a/addons/im_livechat/static/src/js/im_livechat.js b/addons/im_livechat/static/src/js/im_livechat.js
index 4e0a48f4325..086f02daa32 100644
--- a/addons/im_livechat/static/src/js/im_livechat.js
+++ b/addons/im_livechat/static/src/js/im_livechat.js
@@ -215,6 +215,7 @@ var LivechatButton = Widget.extend({
             def = session.rpc('/im_livechat/get_session', {
                 channel_id : this.options.channel_id,
                 anonymous_name : this.options.default_username,
+                previous_operator_id: this._get_previous_operator_id(),
             }, {shadow: true});
         }
         def.then(function (livechatData) {
@@ -233,6 +234,13 @@ var LivechatButton = Widget.extend({
 
                     utils.set_cookie('im_livechat_session', JSON.stringify(self._livechat.toData()), 60*60);
                     utils.set_cookie('im_livechat_auto_popup', JSON.stringify(false), 60*60);
+                    if (livechatData.operator_pid[0]) {
+                        // livechatData.operator_pid contains a tuple (id, name)
+                        // we are only interested in the id
+                        var operatorPidId = livechatData.operator_pid[0];
+                        var oneWeek = 7*24*60*60;
+                        utils.set_cookie('im_livechat_previous_operator_pid', operatorPidId, oneWeek);
+                    }
                 });
             }
         }).then(function () {
@@ -242,6 +250,24 @@ var LivechatButton = Widget.extend({
         });
     }, 200, true),
     /**
+     * Will try to get a previous operator for this visitor.
+     * If the visitor already had visitor A, it's better for his user experience
+     * to get operator A again.
+     *
+     * The information is stored in the 'im_livechat_previous_operator_pid' cookie.
+     *
+     * @private
+     * @return {integer} operator_id.partner_id.id if the cookie is set
+     */
+    _get_previous_operator_id: function () {
+        var cookie = utils.get_cookie('im_livechat_previous_operator_pid');
+        if (cookie) {
+            return cookie;
+        }
+
+        return null;
+    },
+    /**
      * @private
      * @return {Promise}
      */