[MM-53454] Add export file settings + slash command for public link (#23915)

Co-authored-by: Mattermost Build <build@mattermost.com>

server/channels/app/slashcommands/command_exportlink.go

@@ -0,0 +1,120 @@
+// Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
+// See LICENSE.txt for license information.
+
+package slashcommands
+
+import (
+	"path"
+	"strings"
+	"time"
+
+	"github.com/mattermost/logr/v2"
+	"github.com/mattermost/mattermost/server/public/model"
+	"github.com/mattermost/mattermost/server/public/shared/i18n"
+	"github.com/mattermost/mattermost/server/v8/channels/app"
+	"github.com/mattermost/mattermost/server/v8/channels/app/request"
+	"github.com/mattermost/mattermost/server/v8/platform/shared/filestore"
+)
+
+type ExportLinkProvider struct {
+}
+
+const (
+	CmdExportLink       = "exportlink"
+	LatestExportMessage = "latest"
+)
+
+func init() {
+	app.RegisterCommandProvider(&ExportLinkProvider{})
+}
+
+func (*ExportLinkProvider) GetTrigger() string {
+	return CmdExportLink
+}
+
+func (*ExportLinkProvider) GetCommand(a *app.App, T i18n.TranslateFunc) *model.Command {
+	if !a.Config().FeatureFlags.EnableExportDirectDownload {
+		return nil
+	}
+
+	if !*a.Config().FileSettings.DedicatedExportStore {
+		return nil
+	}
+
+	b := a.ExportFileBackend()
+	_, ok := b.(filestore.FileBackendWithLinkGenerator)
+	if !ok {
+		return nil
+	}
+
+	return &model.Command{
+		Trigger:          CmdExportLink,
+		AutoComplete:     true,
+		AutoCompleteDesc: T("api.command_exportlink.desc"),
+		AutoCompleteHint: T("api.command_exportlink.hint", map[string]any{
+			"LatestMsg": LatestExportMessage,
+		}),
+		DisplayName: T("api.command_exportlink.name"),
+	}
+}
+
+func (*ExportLinkProvider) DoCommand(a *app.App, c request.CTX, args *model.CommandArgs, message string) *model.CommandResponse {
+	if !a.SessionHasPermissionTo(*c.Session(), model.PermissionManageSystem) {
+		return &model.CommandResponse{ResponseType: model.CommandResponseTypeEphemeral, Text: args.T("api.command_exportlink.permission.app_error")}
+	}
+
+	b := a.ExportFileBackend()
+	_, ok := b.(filestore.FileBackendWithLinkGenerator)
+	if !ok {
+		return &model.CommandResponse{ResponseType: model.CommandResponseTypeEphemeral, Text: args.T("api.command_exportlink.driver.app_error")}
+	}
+
+	file := ""
+	if message == LatestExportMessage {
+		files, err := b.ListDirectory(*a.Config().ExportSettings.Directory)
+		if err != nil {
+			return &model.CommandResponse{ResponseType: model.CommandResponseTypeEphemeral, Text: args.T("api.command_exportlink.list.app_error")}
+		}
+		if len(files) == 0 {
+			return &model.CommandResponse{ResponseType: model.CommandResponseTypeEphemeral, Text: args.T("api.command_exportlink.empty.app_error")}
+		}
+		latestFound := time.Time{}
+		for _, f := range files {
+			// find the latest file
+			if !strings.HasSuffix(f, "_export.zip") {
+				continue
+			}
+			t, err := b.FileModTime(f)
+			if err != nil {
+				a.Log().Warn("Failed to get file mod time", logr.String("file", f), logr.Err(err))
+				continue
+			}
+			if t.After(latestFound) {
+				file = path.Base(f)
+				latestFound = t
+			}
+		}
+	}
+
+	if model.IsValidId(message) {
+		file = message + "_export.zip"
+	}
+
+	if file == "" {
+		file = message
+	}
+	if !strings.HasSuffix(file, "_export.zip") {
+		return &model.CommandResponse{ResponseType: model.CommandResponseTypeEphemeral, Text: args.T("api.command_exportlink.invalid.app_error")}
+	}
+
+	res, err := a.GeneratePresignURLForExport(file)
+	if err != nil {
+		return &model.CommandResponse{ResponseType: model.CommandResponseTypeEphemeral, Text: args.T("api.command_exportlink.presign.app_error")}
+	}
+
+	// return link
+	return &model.CommandResponse{ResponseType: model.CommandResponseTypeEphemeral, Text: args.T("api.command_exportlink.link.text", map[string]interface{}{
+		"Link":       res.URL,
+		"Expiration": res.Expiration.String(),
+	})}
+}