MM-16819 Helper function to build path to plugin asset (#13626)

Implement helper method to create a URL to the resource from a directory

plugin/helpers_plugin_test.go

@@ -103,3 +103,74 @@ func TestInstallPluginFromURL(t *testing.T) {
 		assert.Equal(t, "received 404 status code while downloading plugin from server", err.Error())
 	})
 }
+
+func TestGetPluginAssetURL(t *testing.T) {
+	siteURL := "https://mattermost.example.com"
+	api := &plugintest.API{}
+	api.On("GetConfig").Return(&model.Config{ServiceSettings: model.ServiceSettings{SiteURL: &siteURL}})
+
+	p := &plugin.HelpersImpl{API: api}
+
+	t.Run("Valid asset directory was provided", func(t *testing.T) {
+		pluginID := "mattermost-1234"
+		dir := "assets"
+		wantedURL := "https://mattermost.example.com/mattermost-1234/assets"
+		gotURL, err := p.GetPluginAssetURL(pluginID, dir)
+
+		assert.Equalf(t, wantedURL, gotURL, "GetPluginAssetURL(%q, %q) got=%q; want=%v", pluginID, dir, gotURL, wantedURL)
+		assert.NoError(t, err)
+	})
+
+	t.Run("Valid asset directory path was provided", func(t *testing.T) {
+		pluginID := "mattermost-1234"
+		dirPath := "/mattermost/assets"
+		wantedURL := "https://mattermost.example.com/mattermost-1234/mattermost/assets"
+		gotURL, err := p.GetPluginAssetURL(pluginID, dirPath)
+
+		assert.Equalf(t, wantedURL, gotURL, "GetPluginAssetURL(%q, %q) got=%q; want=%q", pluginID, dirPath, gotURL, wantedURL)
+		assert.NoError(t, err)
+	})
+
+	t.Run("Valid pluginID was provided", func(t *testing.T) {
+		pluginID := "mattermost-1234"
+		dir := "assets"
+		wantedURL := "https://mattermost.example.com/mattermost-1234/assets"
+		gotURL, err := p.GetPluginAssetURL(pluginID, dir)
+
+		assert.Equalf(t, wantedURL, gotURL, "GetPluginAssetURL(%q, %q) got=%q; want=%q", pluginID, dir, gotURL, wantedURL)
+		assert.NoError(t, err)
+	})
+
+	t.Run("Invalid asset directory name was provided", func(t *testing.T) {
+		pluginID := "mattermost-1234"
+		dir := ""
+		want := ""
+		gotURL, err := p.GetPluginAssetURL(pluginID, dir)
+
+		assert.Emptyf(t, gotURL, "GetPluginAssetURL(%q, %q) got=%s; want=%q", pluginID, dir, gotURL, want)
+		assert.Error(t, err)
+	})
+
+	t.Run("Invalid pluginID was provided", func(t *testing.T) {
+		pluginID := ""
+		dir := "assets"
+		want := ""
+		gotURL, err := p.GetPluginAssetURL(pluginID, dir)
+
+		assert.Emptyf(t, gotURL, "GetPluginAssetURL(%q, %q) got=%q; want=%q", pluginID, dir, gotURL, want)
+		assert.Error(t, err)
+	})
+
+	siteURL = ""
+	api.On("GetConfig").Return(&model.Config{ServiceSettings: model.ServiceSettings{SiteURL: &siteURL}})
+
+	t.Run("Empty SiteURL was configured", func(t *testing.T) {
+		pluginID := "mattermost-1234"
+		dir := "assets"
+		want := ""
+		gotURL, err := p.GetPluginAssetURL(pluginID, dir)
+
+		assert.Emptyf(t, gotURL, "GetPluginAssetURL(%q, %q) got=%q; want=%q", pluginID, dir, gotURL, want)
+		assert.Error(t, err)
+	})
+}