Add realm setting to time-limit editing of message content.

This is controlled through the admin tab and a new field in the Realms table.
Notes:
* The admin tab setting takes a value in minutes, whereas the backend stores it
  in seconds.
* This setting is unused when allow_message_editing is false.
* There is some generosity in how the limit is enforced. For instance, if the
  user sees the hovering edit button, we ensure they have at least 5 seconds to
  click it, and if the user gets to the message edit form, we ensure they have
  at least 10 seconds to make the edit, by relaxing the limit.
* This commit also includes a countdown timer in the message edit form.

Resolves #903.

frontend_tests/casper_tests/10-admin.js

@@ -312,7 +312,7 @@ casper.waitForSelector('input[type="checkbox"][id="id_realm_allow_message_editin
     casper.click('input[type="checkbox"][id="id_realm_allow_message_editing"]');
     casper.click('form.admin-realm-form input.btn');
     casper.waitUntilVisible('#admin-realm-message-editing-status', function () {
-        casper.test.assertSelectorHasText('#admin-realm-message-editing-status', 'Users can now edit the content and topics of all their past messages!');
+        casper.test.assertSelectorHasText('#admin-realm-message-editing-status', 'Users can now edit topics for all their messages, and the content of messages which are less than 10 minutes old.');
         casper.test.assertEval(function () {
             return document.querySelector('input[type="checkbox"][id="id_realm_allow_message_editing"]').checked;
         }, 'Allow message editing Setting re-activated');
@@ -353,6 +353,85 @@ casper.then(function () {
     });
 });
 
+// go back to admin page
+casper.then(function () {
+    casper.test.info('Administration page');
+    casper.click('a[href^="#administration"]');
+    casper.test.assertUrlMatch(/^http:\/\/[^\/]+\/#administration/, 'URL suggests we are on administration page');
+    casper.test.assertExists('#administration.tab-pane.active', 'Administration page is active');
+});
+
+casper.waitForSelector('form.admin-realm-form input.btn', function () {
+    // deactivate message editing
+    casper.waitForSelector('input[type="checkbox"][id="id_realm_allow_message_editing"]', function () {
+        casper.evaluate(function () {
+            $('input[type="text"][id="id_realm_message_content_edit_limit_minutes"]').val('4');
+        });
+        casper.click('input[type="checkbox"][id="id_realm_allow_message_editing"]');
+        casper.click('form.admin-realm-form input.btn');
+        casper.waitUntilVisible('#admin-realm-message-editing-status', function () {
+            casper.test.assertSelectorHasText('#admin-realm-message-editing-status', 'Users can no longer edit their past messages!');
+            casper.test.assertEval(function () {
+                return !(document.querySelector('input[type="checkbox"][id="id_realm_allow_message_editing"]').checked);
+            }, 'Allow message editing Setting de-activated');
+            casper.test.assertEval(function () {
+                return $('input[type="text"][id="id_realm_message_content_edit_limit_minutes"]').val() === '4';
+            }, 'Message content edit limit now 4');
+        });
+    });
+
+    // allow message editing again, and check that the old edit limit is still there
+    casper.waitForSelector('input[type="checkbox"][id="id_realm_allow_message_editing"]', function () {
+        casper.click('input[type="checkbox"][id="id_realm_allow_message_editing"]');
+        casper.click('form.admin-realm-form input.btn');
+        casper.waitUntilVisible('#admin-realm-message-editing-status', function () {
+            casper.test.assertSelectorHasText('#admin-realm-message-editing-status', 'Users can now edit topics for all their messages, and the content of messages which are less than 4 minutes old.');
+            casper.test.assertEval(function () {
+                return document.querySelector('input[type="checkbox"][id="id_realm_allow_message_editing"]').checked;
+            }, 'Allow message editing Setting activated');
+            casper.test.assertEval(function () {
+                return $('input[type="text"][id="id_realm_message_content_edit_limit_minutes"]').val() === '4';
+            }, 'Message content edit limit still 4');
+        });
+    });
+
+    // allow arbitrary message editing
+    casper.waitForSelector('input[type="checkbox"][id="id_realm_allow_message_editing"]', function () {
+        casper.evaluate(function () {
+            $('input[type="text"][id="id_realm_message_content_edit_limit_minutes"]').val('0');
+        });
+        casper.click('form.admin-realm-form input.btn');
+        casper.waitUntilVisible('#admin-realm-message-editing-status', function () {
+            casper.test.assertSelectorHasText('#admin-realm-message-editing-status', 'Users can now edit the content and topics of all their past messages!');
+            casper.test.assertEval(function () {
+                return document.querySelector('input[type="checkbox"][id="id_realm_allow_message_editing"]').checked;
+            }, 'Allow message editing Setting still activated');
+            casper.test.assertEval(function () {
+                return $('input[type="text"][id="id_realm_message_content_edit_limit_minutes"]').val() === '0';
+            }, 'Message content edit limit is 0');
+        });
+    });
+
+    // disallow message editing, with illegal edit limit value. should be fixed by admin.js
+    casper.waitForSelector('input[type="checkbox"][id="id_realm_allow_message_editing"]', function () {
+        casper.evaluate(function () {
+            $('input[type="text"][id="id_realm_message_content_edit_limit_minutes"]').val('moo');
+        });
+        casper.click('input[type="checkbox"][id="id_realm_allow_message_editing"]');
+        casper.click('form.admin-realm-form input.btn');
+        casper.waitUntilVisible('#admin-realm-message-editing-status', function () {
+            casper.test.assertSelectorHasText('#admin-realm-message-editing-status', 'Users can no longer edit their past messages!');
+            casper.test.assertEval(function () {
+                return !(document.querySelector('input[type="checkbox"][id="id_realm_allow_message_editing"]').checked);
+            }, 'Allow message editing Setting de-activated');
+            casper.test.assertEval(function () {
+                return $('input[type="text"][id="id_realm_message_content_edit_limit_minutes"]').val() === '10';
+            }, 'Message content edit limit has been reset to its default');
+        });
+    });
+});
+
+
 common.then_log_out();
 
 casper.run(function () {

static/js/admin.js

@@ -143,7 +143,8 @@ function _setup_page() {
         realm_invite_required:      page_params.realm_invite_required,
         realm_invite_by_admins_only: page_params.realm_invite_by_admins_only,
         realm_create_stream_by_admins_only: page_params.realm_create_stream_by_admins_only,
-        realm_allow_message_editing: page_params.realm_allow_message_editing
+        realm_allow_message_editing: page_params.realm_allow_message_editing,
+        realm_message_content_edit_limit_minutes: Math.ceil(page_params.realm_message_content_edit_limit_seconds / 60)
     };
     var admin_tab = templates.render('admin_tab', options);
     $("#administration").html(admin_tab);
@@ -340,6 +341,16 @@ function _setup_page() {
         }
     });
 
+    $("#id_realm_allow_message_editing").change(function () {
+        if (this.checked) {
+            $("#id_realm_message_content_edit_limit_minutes").removeAttr("disabled");
+            $("#id_realm_message_content_edit_limit_minutes_label").removeClass("control-label-disabled");
+        } else {
+            $("#id_realm_message_content_edit_limit_minutes").attr("disabled", true);
+            $("#id_realm_message_content_edit_limit_minutes_label").addClass("control-label-disabled");
+        }
+    });
+
     $(".administration").on("submit", "form.admin-realm-form", function (e) {
         var name_status = $("#admin-realm-name-status").expectOne();
         var restricted_to_domain_status = $("#admin-realm-restricted-to-domain-status").expectOne();
@@ -363,6 +374,19 @@ function _setup_page() {
         var new_invite_by_admins_only = $("#id_realm_invite_by_admins_only").prop("checked");
         var new_create_stream_by_admins_only = $("#id_realm_create_stream_by_admins_only").prop("checked");
         var new_allow_message_editing = $("#id_realm_allow_message_editing").prop("checked");
+        var new_message_content_edit_limit_minutes = $("#id_realm_message_content_edit_limit_minutes").val();
+
+        // If allow_message_editing is unchecked, message_content_edit_limit_minutes
+        // is irrelevant.  Hence if allow_message_editing is unchecked, and
+        // message_content_edit_limit_minutes is poorly formed, we set the latter to
+        // a default value to prevent the server from returning an error.
+        if (!new_allow_message_editing) {
+            if ((parseInt(new_message_content_edit_limit_minutes, 10).toString() !==
+                 new_message_content_edit_limit_minutes) ||
+                new_message_content_edit_limit_minutes < 0) {
+            new_message_content_edit_limit_minutes = 10; // Realm.DEFAULT_MESSAGE_CONTENT_EDIT_LIMIT_SECONDS / 60
+            }
+        }
 
         var url = "/json/realm";
         var data = {
@@ -371,7 +395,8 @@ function _setup_page() {
             invite_required: JSON.stringify(new_invite),
             invite_by_admins_only: JSON.stringify(new_invite_by_admins_only),
             create_stream_by_admins_only: JSON.stringify(new_create_stream_by_admins_only),
-            allow_message_editing: JSON.stringify(new_allow_message_editing)
+            allow_message_editing: JSON.stringify(new_allow_message_editing),
+            message_content_edit_limit_seconds: JSON.stringify(parseInt(new_message_content_edit_limit_minutes, 10) * 60)
         };
 
         channel.patch({
@@ -410,11 +435,23 @@ function _setup_page() {
                     }
                 }
                 if (response_data.allow_message_editing !== undefined) {
+                    // We expect message_content_edit_limit_seconds was sent in the
+                    // response as well
+                    var data_message_content_edit_limit_minutes = Math.ceil(response_data.message_content_edit_limit_seconds / 60);
                     if (response_data.allow_message_editing) {
-                        ui.report_success(i18n.t("Users can now edit the content and topics of all their past messages!"), message_editing_status);
+                        if (response_data.message_content_edit_limit_seconds > 0) {
+                            ui.report_success(i18n.t("Users can now edit topics for all their messages, and the content of messages which are less than __num_minutes__ minutes old.",
+                                                     {'num_minutes' : data_message_content_edit_limit_minutes}),
+                                              message_editing_status);
+                        } else {
+                            ui.report_success(i18n.t("Users can now edit the content and topics of all their past messages!"), message_editing_status);
+                        }
                     } else {
                         ui.report_success(i18n.t("Users can no longer edit their past messages!"), message_editing_status);
                     }
+                    // message_content_edit_limit_seconds could have been changed earlier
+                    // in this function, so update the field just in case
+                    $("#id_realm_message_content_edit_limit_minutes").val(data_message_content_edit_limit_minutes);
                 }
             },
             error: function (xhr, error) {

static/js/message_edit.js

@@ -86,6 +86,17 @@ function handle_edit_keydown(from_topic_edited_only, e) {
     }
 }
 
+function timer_text(seconds_left) {
+    var minutes = Math.floor(seconds_left / 60);
+    var seconds = seconds_left % 60;
+    if (minutes >= 1) {
+        return i18n.t("__minutes__ min to edit", {'minutes': minutes.toString()});
+    } else if (seconds_left >= 10) {
+        return i18n.t("__seconds__ sec to edit", {'seconds': (seconds - seconds % 5).toString()});
+    }
+    return i18n.t("__seconds__ sec to edit", {'seconds': seconds.toString()});
+}
+
 function edit_message (row, raw_content) {
     var content_top = row.find('.message_content')[0]
         .getBoundingClientRect().top;
@@ -95,7 +106,8 @@ function edit_message (row, raw_content) {
     var form = $(templates.render('message_edit_form',
                                   {is_stream: message.is_stream,
                                    topic: message.subject,
-                                   content: raw_content}));
+                                   content: raw_content,
+                                   minutes_to_edit: Math.floor(page_params.realm_message_content_edit_limit_seconds / 60)}));
 
     var edit_obj = {form: form, raw_content: raw_content};
     var original_topic = message.subject;
@@ -104,8 +116,69 @@ function edit_message (row, raw_content) {
 
     form.keydown(_.partial(handle_edit_keydown, false));
 
+    // We potentially got to this function by clicking a button that implied the
+    // user would be able to edit their message.  Give a little bit of buffer in
+    // case the button has been around for a bit, e.g. we show the
+    // edit_content_button (hovering pencil icon) as long as the user would have
+    // been able to click it at the time the mouse entered the message_row. Also
+    // a buffer in case their computer is slow, or stalled for a second, etc
+    // If you change this number also change edit_limit_buffer in
+    // zerver.views.messages.update_message_backend
+    var seconds_left_buffer = 5;
+
+    var now = new XDate();
+    var seconds_left = page_params.realm_message_content_edit_limit_seconds +
+        now.diffSeconds(message.timestamp * 1000);
+    var can_edit_content = (page_params.realm_message_content_edit_limit_seconds === 0) ||
+        (seconds_left + seconds_left_buffer > 0);
+    if (!can_edit_content) {
+        row.find('textarea.message_edit_content').attr("disabled","disabled");
+    }
+
+    // If we allow editing at all, give them at least 10 seconds to do it.
+    // If you change this number also change edit_limit_buffer in
+    // zerver.views.messages.update_message_backend
+    var min_seconds_to_edit = 10;
+    seconds_left = Math.floor(Math.max(seconds_left, min_seconds_to_edit));
+
+    // Add a visual timer if appropriate
+    if (can_edit_content && page_params.realm_message_content_edit_limit_seconds > 0) {
+        row.find('.message-edit-timer-control-group').show();
+        $('#message_edit_tooltip').tooltip({ animation: false, placement: 'left',
+                                             template: '<div class="tooltip" role="tooltip"><div class="tooltip-arrow"></div><div class="tooltip-inner message-edit-tooltip-inner"></div></div>'});
+        // I believe these need to be defined outside the countdown_timer, since
+        // row just refers to something like the currently selected message, and
+        // can change out from under us
+        var message_content_row = row.find('textarea.message_edit_content');
+        var message_topic_row, message_topic_propagate_row;
+        if (message.is_stream) {
+            message_topic_row = row.find('input.message_edit_topic');
+            message_topic_propagate_row = row.find('select.message_edit_topic_propagate');
+        }
+        var message_save_row = row.find('button.message_edit_save');
+        var timer_row = row.find('.message_edit_countdown_timer');
+        // Do this right away, rather than waiting for the timer to do its first update,
+        // since otherwise there is a noticeable lag
+        timer_row.text(timer_text(seconds_left));
+        var countdown_timer = setInterval(function () {
+            if (--seconds_left <= 0) {
+                clearInterval(countdown_timer);
+                message_content_row.attr("disabled","disabled");
+                if (message.is_stream) {
+                    message_topic_row.attr("disabled","disabled");
+                    message_topic_propagate_row.hide();
+                }
+                message_save_row.addClass("disabled");
+                timer_row.text(i18n.t("Time's up!"));
+            } else {
+                timer_row.text(timer_text(seconds_left));
+            }
+        }, 1000);
+    }
+
     currently_editing_messages[message.id] = edit_obj;
-    if (message.type === 'stream' && message.subject === compose.empty_subject_placeholder()) {
+    if ((message.type === 'stream' && message.subject === compose.empty_subject_placeholder()) ||
+        !can_edit_content) {
         edit_row.find(".message_edit_topic").focus();
     } else {
         edit_row.find(".message_edit_content").focus();
@@ -128,6 +201,7 @@ function edit_message (row, raw_content) {
     }
 
     composebox_typeahead.initialize_compose_typeahead("#message_edit_content", {emoji: true});
+
 }
 
 function start_edit_maintaining_scroll(row, content) {

static/js/ui.js

@@ -118,7 +118,12 @@ function message_hover(message_row) {
     message = current_msg_list.get(rows.id(message_row));
     message_unhover();
     message_row.addClass('message_hovered');
-    if (message && message.sent_by_me && !message.status_message && page_params.realm_allow_message_editing) {
+    var now = new XDate();
+    if (message && message.sent_by_me && !message.status_message &&
+        page_params.realm_allow_message_editing &&
+        (page_params.realm_message_content_edit_limit_seconds === 0 ||
+         page_params.realm_message_content_edit_limit_seconds + now.diffSeconds(message.timestamp * 1000) > 0))
+    {
         message_row.find('.message_content').find('p:last').append(edit_content_button);
     }
     current_message_hover = message_row;

static/styles/settings.css

@@ -345,6 +345,11 @@ form.admin-realm .control-label {
     color: #d3d3d3;
 }
 
+.admin-realm-message-content-edit-limit-minutes {
+    width: 5ch;
+    text-align: right;
+}
+
 #settings-status {
     text-align: center;
     width: 50%;

static/styles/zulip.css

@@ -321,6 +321,7 @@ a:hover code {
     display: inline;
 }
 
+#message_edit_tooltip,
 #streams_inline_cog,
 #streams_filter_icon {
     float: right;
@@ -331,11 +332,19 @@ a:hover code {
     opacity: 0.5;
 }
 
+#message_edit_tooltip:hover,
 #streams_inline_cog:hover,
 #streams_filter_icon:hover {
    opacity: 1.0;
 }
 
+.message-edit-tooltip-inner {
+    width: 200px;
+    position: absolute;
+    right: 7px;
+    top: -18px;
+}
+
 #streams_header a {
     color: inherit;
     text-decoration: none;
@@ -1406,6 +1415,22 @@ div.focused_table {
     line-height: 18px;
 }
 
+.message_edit_countdown_timer {
+    text-align: right;
+    display: inline;
+    color: #a1a1a1;
+}
+
+.message_edit_tooltip {
+    display: inline;
+    color: #a1a1a1;
+}
+
+.message-edit-timer-control-group {
+    float: right;
+    display: none;
+}
+
 .topic_edit {
     display: none;
     line-height: 22px;

static/templates/admin_tab.handlebars

@@ -101,6 +101,21 @@
                     {{#if realm_allow_message_editing}}checked="checked"{{/if}} />
                 </div>
               </div>
+              <div class="control-group">
+                <label for="realm_message_content_edit_limit_minutes"
+                  id="id_realm_message_content_edit_limit_minutes_label"
+                  title="{{t 'If non-zero, users can edit their message for this many minutes after it is sent. If zero, users can edit all their past messages.' }}"
+                  class="control-label{{#unless realm_allow_message_editing}} control-label-disabled{{/unless}}">
+                  {{t 'Message edit limit in minutes (0 for no limit)' }}
+                </label>
+                <div class="controls">
+                  <input type="text" id="id_realm_message_content_edit_limit_minutes"
+                         name="realm_message_content_edit_limit_minutes"
+                         class="admin-realm-message-content-edit-limit-minutes"
+                         value="{{ realm_message_content_edit_limit_minutes }}"
+                    {{#unless realm_allow_message_editing}}disabled="disabled"{{/unless}} />
+                </div>
+              </div>
               <div class="controls organization-submission">
               <input type="submit" class="btn btn-big btn-primary" value="{{t 'Save changes' }}" />
               </div>

static/templates/message_edit_form.handlebars

@@ -14,6 +14,7 @@
         </div>
     </div>
 {{/if}}
+
     <div class="control-group">
         <div class="controls edit-controls">
             <textarea class="message_edit_content" id="message_edit_content">{{content}}</textarea>
@@ -23,6 +24,12 @@
         <div class="controls edit-controls">
             <button type="button" class="message_edit_save btn btn-primary btn-small">{{t "Save" }}</button>
             <button type="button" class="message_edit_cancel btn btn-default btn-small">{{t "Cancel" }}</button>
+            <div class="message-edit-timer-control-group">
+                <span class="message_edit_countdown_timer"></span>
+                <span><i id="message_edit_tooltip" class="message_edit_tooltip icon-vector-question-sign" data-toggle="tooltip"
+                         title="Message content can only be edited for {{minutes_to_edit}} minutes after it is sent."></i>
+                </span>
+            </div>
         </div>
     </div>
     <div class="alert alert-error edit_error hide"></div>

zerver/lib/actions.py

@@ -412,15 +412,17 @@ def do_set_realm_create_stream_by_admins_only(realm, create_stream_by_admins_onl
     )
     send_event(event, active_user_ids(realm))
 
-def do_set_realm_message_editing(realm, allow_message_editing):
+def do_set_realm_message_editing(realm, allow_message_editing, message_content_edit_limit_seconds):
-    # type: (Realm, bool) -> None
+    # type: (Realm, bool, int) -> None
     realm.allow_message_editing = allow_message_editing
-    realm.save(update_fields=['allow_message_editing'])
+    realm.message_content_edit_limit_seconds = message_content_edit_limit_seconds
+    realm.save(update_fields=['allow_message_editing', 'message_content_edit_limit_seconds'])
     event = dict(
         type="realm",
         op="update_dict",
         property="default",
-        data=dict(allow_message_editing=allow_message_editing),
+        data=dict(allow_message_editing=allow_message_editing,
+                  message_content_edit_limit_seconds=message_content_edit_limit_seconds),
     )
     send_event(event, active_user_ids(realm))
 
@@ -2388,7 +2390,7 @@ def do_update_message(user_profile, message_id, subject, propagate_mode, content
     edit_history_event = {}
     changed_messages = [message]
 
-    # You can only edit a message if:
+    # You only have permission to edit a message if:
     # 1. You sent it, OR:
     # 2. This is a topic-only edit for a (no topic) message, OR:
     # 3. This is a topic-only edit and you are an admin.
@@ -2400,6 +2402,20 @@ def do_update_message(user_profile, message_id, subject, propagate_mode, content
     else:
         raise JsonableError(_("You don't have permission to edit this message"))
 
+    # We already check for realm.allow_message_editing in
+    # zerver.views.messages.update_message_backend
+    # If there is a change to the content, we also need to check it hasn't been
+    # too long
+
+    # Allow an extra 20 seconds since we potentially allow editing 15 seconds
+    # past the limit, and in case there are network issues, etc. The 15 comes
+    # from (min_seconds_to_edit + seconds_left_buffer) in message_edit.js; if
+    # you change this value also change those two parameters in message_edit.js.
+    edit_limit_buffer = 20
+    if content is not None and user_profile.realm.message_content_edit_limit_seconds > 0 and \
+       (now() - message.pub_date) > datetime.timedelta(seconds=user_profile.realm.message_content_edit_limit_seconds + edit_limit_buffer):
+        raise JsonableError(_("The time limit for editing this message has past"))
+
     # Set first_rendered_content to be the oldest version of the
     # rendered content recorded; which is the current version if the
     # content hasn't been edited before.  Note that because one could
@@ -2708,6 +2724,7 @@ def fetch_initial_state_data(user_profile, event_types, queue_id):
         state['realm_invite_by_admins_only'] = user_profile.realm.invite_by_admins_only
         state['realm_create_stream_by_admins_only'] = user_profile.realm.create_stream_by_admins_only
         state['realm_allow_message_editing'] = user_profile.realm.allow_message_editing
+        state['realm_message_content_edit_limit_seconds'] = user_profile.realm.message_content_edit_limit_seconds
 
     if want('realm_domain'):
         state['realm_domain'] = user_profile.realm.domain

zerver/migrations/0025_realm_message_content_edit_limit.py

@@ -0,0 +1,19 @@
+# -*- coding: utf-8 -*-
+from __future__ import unicode_literals
+
+from django.db import models, migrations
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('zerver', '0024_realm_allow_message_editing'),
+    ]
+
+    operations = [
+        migrations.AddField(
+            model_name='realm',
+            name='message_content_edit_limit_seconds',
+            field=models.IntegerField(default=600),
+        ),
+    ]

zerver/models.py

@@ -143,7 +143,10 @@ class Realm(ModelReprMixin, models.Model):
     mandatory_topics = models.BooleanField(default=False) # type: bool
     show_digest_email = models.BooleanField(default=True) # type: bool
     name_changes_disabled = models.BooleanField(default=False) # type: bool
+
     allow_message_editing = models.BooleanField(default=True) # type: bool
+    DEFAULT_MESSAGE_CONTENT_EDIT_LIMIT_SECONDS = 600 # if changed, also change in admin.js
+    message_content_edit_limit_seconds = models.IntegerField(default=DEFAULT_MESSAGE_CONTENT_EDIT_LIMIT_SECONDS) # type: int
 
     date_created = models.DateTimeField(default=timezone.now) # type: datetime.datetime
     notifications_stream = models.ForeignKey('Stream', related_name='+', null=True, blank=True) # type: Optional[Stream]

zerver/tests/test_events.py

@@ -512,12 +512,16 @@ class EventsRegisterTest(AuthedTestCase):
             ('type', equals('realm')),
             ('op', equals('update_dict')),
             ('property', equals('default')),
-            ('data', check_dict([('allow_message_editing', check_bool)])),
+            ('data', check_dict([('allow_message_editing', check_bool),
+                                 ('message_content_edit_limit_seconds', check_int)])),
         ])
-        # The first False is probably a noop, then we get transitions in both directions.
+        # Test every transition among the four possibilities {T,F} x {0, non-0}
-        for allow_message_editing in [False, True, False]:
+        for (allow_message_editing, message_content_edit_limit_seconds) in \
+            ((True, 0), (False, 0), (True, 0), (False, 1234), (True, 0), (True, 1234), (True, 0),
+             (False, 0), (False, 1234), (False, 0), (True, 1234), (False, 0),
+             (True, 1234), (True, 600), (False, 600), (False, 1234), (True, 600)):
             events = self.do_test(lambda: do_set_realm_message_editing(self.user_profile.realm,
-                                                                       allow_message_editing))
+                                      allow_message_editing, message_content_edit_limit_seconds))
             error = schema_checker('events[0]', events[0])
             self.assert_on_error(error)
 

zerver/tests/test_messages.py

@@ -779,6 +779,72 @@ class EditMessageTest(AuthedTestCase):
         })
         self.assert_json_error(result, "Content can't be empty")
 
+    def test_edit_message_content_limit(self):
+        def set_message_editing_params(allow_message_editing,
+                                       message_content_edit_limit_seconds):
+            result = self.client_patch("/json/realm", {
+                'allow_message_editing': ujson.dumps(allow_message_editing),
+                'message_content_edit_limit_seconds': message_content_edit_limit_seconds
+            })
+            self.assert_json_success(result)
+
+        def do_edit_message_assert_success(id_, unique_str, topic_only = False):
+            new_subject = 'subject' + unique_str
+            new_content = 'content' + unique_str
+            params_dict = { 'message_id': id_, 'subject': new_subject }
+            if not topic_only:
+                params_dict['content'] = new_content
+            result = self.client.post("/json/update_message", params_dict)
+            self.assert_json_success(result)
+            if topic_only:
+                self.check_message(id_, subject=new_subject)
+            else:
+                self.check_message(id_, subject=new_subject, content=new_content)
+
+        def do_edit_message_assert_error(id_, unique_str, error, topic_only = False):
+            message = Message.objects.get(id=id_)
+            old_subject = message.subject
+            old_content = message.content
+            new_subject = 'subject' + unique_str
+            new_content = 'content' + unique_str
+            params_dict = { 'message_id': id_, 'subject': new_subject }
+            if not topic_only:
+                params_dict['content'] = new_content
+            result = self.client.post("/json/update_message", params_dict)
+            message = Message.objects.get(id=id_)
+            self.assert_json_error(result, error)
+            self.check_message(id_, subject=old_subject, content=old_content)
+
+        self.login("iago@zulip.com")
+        # send a message in the past
+        id_ = self.send_message("iago@zulip.com", "Scotland", Recipient.STREAM,
+                                content="content", subject="subject")
+        message = Message.objects.get(id=id_)
+        message.pub_date = message.pub_date - datetime.timedelta(seconds=180)
+        message.save()
+
+        # test the various possible message editing settings
+        # high enough time limit, all edits allowed
+        set_message_editing_params(True, 240)
+        do_edit_message_assert_success(id_, 'A')
+
+        # out of time, only topic editing allowed
+        set_message_editing_params(True, 120)
+        do_edit_message_assert_success(id_, 'B', True)
+        do_edit_message_assert_error(id_, 'C', "The time limit for editing this message has past")
+
+        # infinite time, all edits allowed
+        set_message_editing_params(True, 0)
+        do_edit_message_assert_success(id_, 'D')
+
+        # without allow_message_editing, nothing is allowed
+        set_message_editing_params(False, 240)
+        do_edit_message_assert_error(id_, 'E', "Your organization has turned off message editing.", True)
+        set_message_editing_params(False, 120)
+        do_edit_message_assert_error(id_, 'F', "Your organization has turned off message editing.", True)
+        set_message_editing_params(False, 0)
+        do_edit_message_assert_error(id_, 'G', "Your organization has turned off message editing.", True)
+
     def test_propagate_topic_forward(self):
         self.login("hamlet@zulip.com")
         id1 = self.send_message("hamlet@zulip.com", "Scotland", Recipient.STREAM,
@@ -982,4 +1048,3 @@ class CheckMessageTest(AuthedTestCase):
         new_count = message_stream_count(parent)
         self.assertEqual(new_count, old_count + 1)
         self.assertEqual(ret['message'].sender.email, 'othello-bot@zulip.com')
-

zerver/views/__init__.py

@@ -946,6 +946,7 @@ def home(request):
         realm_invite_by_admins_only = register_ret['realm_invite_by_admins_only'],
         realm_create_stream_by_admins_only = register_ret['realm_create_stream_by_admins_only'],
         realm_allow_message_editing = register_ret['realm_allow_message_editing'],
+        realm_message_content_edit_limit_seconds = register_ret['realm_message_content_edit_limit_seconds'],
         realm_restricted_to_domain = register_ret['realm_restricted_to_domain'],
         enter_sends           = user_profile.enter_sends,
         left_side_userlist    = register_ret['left_side_userlist'],
@@ -1103,8 +1104,9 @@ def update_realm(request, user_profile, name=REQ(validator=check_string, default
                  invite_required=REQ(validator=check_bool, default=None),
                  invite_by_admins_only=REQ(validator=check_bool, default=None),
                  create_stream_by_admins_only=REQ(validator=check_bool, default=None),
-                 allow_message_editing=REQ(validator=check_bool, default=None)):
+                 allow_message_editing=REQ(validator=check_bool, default=None),
-    # type: (HttpRequest, UserProfile, Optional[str], Optional[bool], Optional[bool], Optional[bool], Optional[bool], Optional[bool]) -> HttpResponse
+                 message_content_edit_limit_seconds=REQ(converter=to_non_negative_int, default=None)):
+    # type: (HttpRequest, UserProfile, Optional[str], Optional[bool], Optional[bool], Optional[bool], Optional[bool], Optional[bool], Optional[int]) -> HttpResponse
     realm = user_profile.realm
     data = {} # type: Dict[str, Any]
     if name is not None and realm.name != name:
@@ -1122,9 +1124,15 @@ def update_realm(request, user_profile, name=REQ(validator=check_string, default
     if create_stream_by_admins_only is not None and realm.create_stream_by_admins_only != create_stream_by_admins_only:
         do_set_realm_create_stream_by_admins_only(realm, create_stream_by_admins_only)
         data['create_stream_by_admins_only'] = create_stream_by_admins_only
-    if allow_message_editing is not None and realm.allow_message_editing != allow_message_editing:
+    if (allow_message_editing is not None and realm.allow_message_editing != allow_message_editing) or \
-        do_set_realm_message_editing(realm, allow_message_editing)
+       (message_content_edit_limit_seconds is not None and realm.message_content_edit_limit_seconds != message_content_edit_limit_seconds):
+        if allow_message_editing is None:
+            allow_message_editing = realm.allow_message_editing
+        if message_content_edit_limit_seconds is None:
+            message_content_edit_limit_seconds = realm.message_content_edit_limit_seconds
+        do_set_realm_message_editing(realm, allow_message_editing, message_content_edit_limit_seconds)
         data['allow_message_editing'] = allow_message_editing
+        data['message_content_edit_limit_seconds'] = message_content_edit_limit_seconds
     return json_success(data)
 
 @csrf_exempt