[MM-20684] Slash Command Autocomplete (#14557)

* [MM-20684] Initial implementation of the Command Autocomplete (#13602)

* Implement Autocomplete Data

* Change CommandName to Trigger

* Fix Autocomplete test

* Make stylistic changes

* Rename a bunch of fields and methods

* Fix variable names, safer type assertions

* [MM-20684] plugin autocomplete implementation (#14259)

* Add an endpoint for command autocomplete suggestions

* Add full Suggestion to the AutocompleteSugestion struct

* Add Dynamic Argument support

* Tidy up things

* Fix missed test case

* Add support of the named arguments

* Update autocomplete API

Fix review issues

Implement dynamic args as a local request

* Fix ineffassign

* Add support of the uppercase letters in arguments

* Add support of the optional arguments

* Remove ineffectual assignment

* Add support for icons (#14489)

* Address couple of nits

* Add comment to IconData

* Add types to all consts

Co-authored-by: mattermod <mattermod@users.noreply.github.com>

api4/command.go

@@ -23,6 +23,7 @@ func (api *API) InitCommand() {
 	api.BaseRoutes.Command.Handle("", api.ApiSessionRequired(deleteCommand)).Methods("DELETE")
 
 	api.BaseRoutes.Team.Handle("/commands/autocomplete", api.ApiSessionRequired(listAutocompleteCommands)).Methods("GET")
+	api.BaseRoutes.Team.Handle("/commands/autocomplete_suggestions", api.ApiSessionRequired(listCommandAutocompleteSuggestions)).Methods("GET")
 	api.BaseRoutes.Command.Handle("/regen_token", api.ApiSessionRequired(regenCommandToken)).Methods("PUT")
 }
 
@@ -369,6 +370,39 @@ func listAutocompleteCommands(c *Context, w http.ResponseWriter, r *http.Request
 	w.Write([]byte(model.CommandListToJson(commands)))
 }
 
+func listCommandAutocompleteSuggestions(c *Context, w http.ResponseWriter, r *http.Request) {
+	c.RequireTeamId()
+	if c.Err != nil {
+		return
+	}
+	if !c.App.SessionHasPermissionToTeam(*c.App.Session(), c.Params.TeamId, model.PERMISSION_VIEW_TEAM) {
+		c.SetPermissionError(model.PERMISSION_VIEW_TEAM)
+		return
+	}
+
+	roleId := model.SYSTEM_USER_ROLE_ID
+	if c.IsSystemAdmin() {
+		roleId = model.SYSTEM_ADMIN_ROLE_ID
+	}
+
+	userInput := r.URL.Query().Get("user_input")
+	if userInput == "" {
+		c.SetInvalidParam("userInput")
+		return
+	}
+	userInput = strings.TrimPrefix(userInput, "/")
+
+	commands, err := c.App.ListAutocompleteCommands(c.Params.TeamId, c.App.T)
+	if err != nil {
+		c.Err = err
+		return
+	}
+
+	suggestions := c.App.GetSuggestions(commands, userInput, roleId)
+
+	w.Write(model.AutocompleteSuggestionsToJSON(suggestions))
+}
+
 func regenCommandToken(c *Context, w http.ResponseWriter, r *http.Request) {
 	c.RequireCommandId()
 	if c.Err != nil {