[MM-25659] ability to permanent delete channel through client (#15202)

Summary

    Ability to permanent delete channel through client

Ticket Link

    https://mattermost.atlassian.net/browse/MM-25659

api4/channel.go

@@ -1074,7 +1074,15 @@ func deleteChannel(c *Context, w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
-	err = c.App.DeleteChannel(channel, c.App.Session().UserId)
+	if c.Params.Permanent {
+		if *c.App.Config().ServiceSettings.EnableAPIChannelDeletion {
+			err = c.App.PermanentDeleteChannel(channel)
+		} else {
+			err = model.NewAppError("deleteChannel", "api.user.delete_channel.not_enabled.app_error", nil, "channelId="+c.Params.ChannelId, http.StatusUnauthorized)
+		}
+	} else {
+		err = c.App.DeleteChannel(channel, c.App.Session().UserId)
+	}
 	if err != nil {
 		c.Err = err
 		return

api4/channel_local.go

@@ -15,7 +15,7 @@ func (api *API) InitChannelLocal() {
 	api.BaseRoutes.Channels.Handle("", api.ApiLocal(localCreateChannel)).Methods("POST")
 	api.BaseRoutes.Channel.Handle("", api.ApiLocal(getChannel)).Methods("GET")
 	api.BaseRoutes.ChannelByName.Handle("", api.ApiLocal(getChannelByName)).Methods("GET")
-	api.BaseRoutes.Channel.Handle("", api.ApiLocal(deleteChannel)).Methods("DELETE")
+	api.BaseRoutes.Channel.Handle("", api.ApiLocal(localDeleteChannel)).Methods("DELETE")
 	api.BaseRoutes.Channel.Handle("/patch", api.ApiLocal(localPatchChannel)).Methods("PUT")
 	api.BaseRoutes.Channel.Handle("/move", api.ApiLocal(localMoveChannel)).Methods("POST")
 
@@ -277,3 +277,40 @@ func localMoveChannel(c *Context, w http.ResponseWriter, r *http.Request) {
 
 	w.Write([]byte(channel.ToJson()))
 }
+
+func localDeleteChannel(c *Context, w http.ResponseWriter, r *http.Request) {
+	c.RequireChannelId()
+	if c.Err != nil {
+		return
+	}
+
+	channel, err := c.App.GetChannel(c.Params.ChannelId)
+	if err != nil {
+		c.Err = err
+		return
+	}
+
+	auditRec := c.MakeAuditRecord("localDeleteChannel", audit.Fail)
+	defer c.LogAuditRec(auditRec)
+	auditRec.AddMeta("channeld", channel)
+
+	if channel.Type == model.CHANNEL_DIRECT || channel.Type == model.CHANNEL_GROUP {
+		c.Err = model.NewAppError("localDeleteChannel", "api.channel.delete_channel.type.invalid", nil, "", http.StatusBadRequest)
+		return
+	}
+
+	if c.Params.Permanent {
+		err = c.App.PermanentDeleteChannel(channel)
+	} else {
+		err = c.App.DeleteChannel(channel, "")
+	}
+	if err != nil {
+		c.Err = err
+		return
+	}
+
+	auditRec.Success()
+	c.LogAudit("name=" + channel.Name)
+
+	ReturnStatusOK(w)
+}

api4/channel_test.go

@@ -1629,6 +1629,45 @@ func TestDeleteChannel2(t *testing.T) {
 	CheckForbiddenStatus(t, resp)
 }
 
+func TestPermanentDeleteChannel(t *testing.T) {
+	th := Setup(t).InitBasic()
+	defer th.TearDown()
+
+	enableAPIChannelDeletion := *th.App.Config().ServiceSettings.EnableAPIChannelDeletion
+	defer func() {
+		th.App.UpdateConfig(func(cfg *model.Config) { cfg.ServiceSettings.EnableAPIChannelDeletion = &enableAPIChannelDeletion })
+	}()
+
+	th.App.UpdateConfig(func(cfg *model.Config) { *cfg.ServiceSettings.EnableAPIChannelDeletion = false })
+
+	publicChannel1 := th.CreatePublicChannel()
+	t.Run("Permanent deletion not available through API if EnableAPIChannelDeletion is not set", func(t *testing.T) {
+		_, resp := th.SystemAdminClient.PermanentDeleteChannel(publicChannel1.Id)
+		CheckUnauthorizedStatus(t, resp)
+	})
+
+	t.Run("Permanent deletion available through local mode even if EnableAPIChannelDeletion is not set", func(t *testing.T) {
+		ok, resp := th.LocalClient.PermanentDeleteChannel(publicChannel1.Id)
+		CheckNoError(t, resp)
+		assert.True(t, ok)
+	})
+
+	th.App.UpdateConfig(func(cfg *model.Config) { *cfg.ServiceSettings.EnableAPIChannelDeletion = true })
+	th.TestForSystemAdminAndLocal(t, func(t *testing.T, c *model.Client4) {
+		publicChannel := th.CreatePublicChannel()
+		ok, resp := c.PermanentDeleteChannel(publicChannel.Id)
+		CheckNoError(t, resp)
+		assert.True(t, ok)
+
+		_, err := th.App.GetChannel(publicChannel.Id)
+		assert.NotNil(t, err)
+
+		ok, resp = c.PermanentDeleteChannel("junk")
+		CheckBadRequestStatus(t, resp)
+		require.False(t, ok, "should have returned false")
+	}, "Permanent deletion with EnableAPIChannelDeletion set")
+}
+
 func TestConvertChannelToPrivate(t *testing.T) {
 	th := Setup(t).InitBasic()
 	defer th.TearDown()