MM-11384: Add system install date information to the client config (#9218)

* MM-11384: Add system install date information to the client config

* Fixing translation text

* Fixes from Peer Review

app/config_test.go

@@ -4,11 +4,15 @@
 package app
 
 import (
+	"strconv"
 	"testing"
+	"time"
 
 	"github.com/stretchr/testify/assert"
 
 	"github.com/mattermost/mattermost-server/model"
+	"github.com/mattermost/mattermost-server/store/sqlstore"
+	"github.com/mattermost/mattermost-server/utils"
 )
 
 func TestConfigListener(t *testing.T) {
@@ -76,3 +80,80 @@ func TestClientConfigWithComputed(t *testing.T) {
 		t.Fatal("expected MaxPostSize in returned config")
 	}
 }
+
+func TestEnsureInstallationDate(t *testing.T) {
+	th := Setup()
+	defer th.TearDown()
+
+	tt := []struct {
+		Name                     string
+		PrevInstallationDate     *int64
+		UsersCreationDates       []int64
+		ExpectedInstallationDate *int64
+	}{
+		{
+			Name:                     "New installation: no users, no installation date",
+			PrevInstallationDate:     nil,
+			UsersCreationDates:       nil,
+			ExpectedInstallationDate: model.NewInt64(utils.MillisFromTime(time.Now())),
+		},
+		{
+			Name:                     "Old installation: users, no installation date",
+			PrevInstallationDate:     nil,
+			UsersCreationDates:       []int64{10000000000, 30000000000, 20000000000},
+			ExpectedInstallationDate: model.NewInt64(10000000000),
+		},
+		{
+			Name:                     "New installation, second run: no users, installation date",
+			PrevInstallationDate:     model.NewInt64(80000000000),
+			UsersCreationDates:       []int64{10000000000, 30000000000, 20000000000},
+			ExpectedInstallationDate: model.NewInt64(80000000000),
+		},
+		{
+			Name:                     "Old installation already updated: users, installation date",
+			PrevInstallationDate:     model.NewInt64(90000000000),
+			UsersCreationDates:       []int64{10000000000, 30000000000, 20000000000},
+			ExpectedInstallationDate: model.NewInt64(90000000000),
+		},
+	}
+
+	for _, tc := range tt {
+		t.Run(tc.Name, func(t *testing.T) {
+			sqlStore := th.App.Srv.Store.User().(*sqlstore.SqlUserStore)
+			sqlStore.GetMaster().Exec("DELETE FROM Users")
+
+			var users []*model.User
+			for _, createAt := range tc.UsersCreationDates {
+				user := th.CreateUser()
+				user.CreateAt = createAt
+				sqlStore.GetMaster().Exec("UPDATE Users SET CreateAt = :CreateAt WHERE Id = :UserId", map[string]interface{}{"CreateAt": createAt, "UserId": user.Id})
+				users = append(users, user)
+			}
+
+			if tc.PrevInstallationDate == nil {
+				<-th.App.Srv.Store.System().PermanentDeleteByName(model.SYSTEM_INSTALLATION_DATE_KEY)
+			} else {
+				<-th.App.Srv.Store.System().SaveOrUpdate(&model.System{
+					Name:  model.SYSTEM_INSTALLATION_DATE_KEY,
+					Value: strconv.FormatInt(*tc.PrevInstallationDate, 10),
+				})
+			}
+
+			err := th.App.ensureInstallationDate()
+
+			if tc.ExpectedInstallationDate == nil {
+				assert.Error(t, err)
+			} else {
+				assert.NoError(t, err)
+
+				result := <-th.App.Srv.Store.System().GetByName(model.SYSTEM_INSTALLATION_DATE_KEY)
+				assert.Nil(t, result.Err)
+				data, _ := result.Data.(*model.System)
+				value, _ := strconv.ParseInt(data.Value, 10, 64)
+				assert.True(t, *tc.ExpectedInstallationDate <= value && *tc.ExpectedInstallationDate+1000 >= value)
+			}
+
+			sqlStore.GetMaster().Exec("DELETE FROM Users")
+		})
+	}
+}