[PLT-6707] /header [text] slash command: Edit the channel header (#6566)

* add /header slash command

* update websocket

* updater per review

app/command_channel_header.go

@@ -0,0 +1,73 @@
+// Copyright (c) 2017-present Mattermost, Inc. All Rights Reserved.
+// See License.txt for license information.
+
+package app
+
+import (
+	l4g "github.com/alecthomas/log4go"
+	"github.com/mattermost/platform/model"
+
+	goi18n "github.com/nicksnyder/go-i18n/i18n"
+)
+
+type HeaderProvider struct {
+}
+
+const (
+	CMD_HEADER = "header"
+)
+
+func init() {
+	RegisterCommandProvider(&HeaderProvider{})
+}
+
+func (me *HeaderProvider) GetTrigger() string {
+	return CMD_HEADER
+}
+
+func (me *HeaderProvider) GetCommand(T goi18n.TranslateFunc) *model.Command {
+	return &model.Command{
+		Trigger:          CMD_HEADER,
+		AutoComplete:     true,
+		AutoCompleteDesc: T("api.command_channel_header.desc"),
+		AutoCompleteHint: T("api.command_channel_header.hint"),
+		DisplayName:      T("api.command_channel_header.name"),
+	}
+}
+
+func (me *HeaderProvider) DoCommand(args *model.CommandArgs, message string) *model.CommandResponse {
+	channel, err := GetChannel(args.ChannelId)
+	if err != nil {
+		return &model.CommandResponse{Text: args.T("api.command_channel_header.channel.app_error"), ResponseType: model.COMMAND_RESPONSE_TYPE_EPHEMERAL}
+	}
+
+	if channel.Type == model.CHANNEL_OPEN && !SessionHasPermissionToChannel(args.Session, args.ChannelId, model.PERMISSION_MANAGE_PUBLIC_CHANNEL_PROPERTIES) {
+		return &model.CommandResponse{Text: args.T("api.command_channel_header.permission.app_error"), ResponseType: model.COMMAND_RESPONSE_TYPE_EPHEMERAL}
+	}
+
+	if channel.Type == model.CHANNEL_PRIVATE && !SessionHasPermissionToChannel(args.Session, args.ChannelId, model.PERMISSION_MANAGE_PRIVATE_CHANNEL_PROPERTIES) {
+		return &model.CommandResponse{Text: args.T("api.command_channel_header.permission.app_error"), ResponseType: model.COMMAND_RESPONSE_TYPE_EPHEMERAL}
+	}
+
+	if len(message) == 0 {
+		return &model.CommandResponse{Text: args.T("api.command_channel_header.message.app_error"), ResponseType: model.COMMAND_RESPONSE_TYPE_EPHEMERAL}
+	}
+
+	oldChannelHeader := channel.Header
+	channel.Header = message
+
+	updateChannel, err := UpdateChannel(channel)
+	if err != nil {
+		return &model.CommandResponse{Text: args.T("api.command_channel_header.update_channel.app_error"), ResponseType: model.COMMAND_RESPONSE_TYPE_EPHEMERAL}
+	}
+
+	messageWs := model.NewWebSocketEvent(model.WEBSOCKET_EVENT_CHANNEL_UPDATED, "", channel.Id, "", nil)
+	messageWs.Add("channel", channel.ToJson())
+	Publish(messageWs)
+
+	if err := PostUpdateChannelHeaderMessage(args.Session.UserId, channel.Id, args.TeamId, oldChannelHeader, updateChannel.Header); err != nil {
+		l4g.Error(err.Error())
+	}
+
+	return &model.CommandResponse{}
+}