Set backupSchedule as required in MongoDB Flex instance (#96)

* Set backupSchedule as required in MongoDB Flex instance

* Update example and generate docs

* Add regex explanation comment

* Fix acceptance test

* Fix map fields

stackit/internal/services/mongodbflex/instance/resource.go

@@ -21,7 +21,6 @@ import (
 	"github.com/hashicorp/terraform-plugin-framework/resource"
 	"github.com/hashicorp/terraform-plugin-framework/resource/schema"
 	"github.com/hashicorp/terraform-plugin-framework/resource/schema/planmodifier"
-	"github.com/hashicorp/terraform-plugin-framework/resource/schema/stringdefault"
 	"github.com/hashicorp/terraform-plugin-framework/resource/schema/stringplanmodifier"
 	"github.com/hashicorp/terraform-plugin-framework/types"
 	"github.com/stackitcloud/stackit-sdk-go/core/config"
@@ -206,11 +205,7 @@ func (r *instanceResource) Schema(_ context.Context, _ resource.SchemaRequest, r
 				Required:    true,
 			},
 			"backup_schedule": schema.StringAttribute{
-				Computed: true, // Update functionality for this field is currently not working properly on the API side
-				PlanModifiers: []planmodifier.String{
-					stringplanmodifier.UseStateForUnknown(),
-				},
-				Default: stringdefault.StaticString(DefaultBackupSchedule), // Using the same default value as the Portal, as the field is required
+				Required: true,
 			},
 			"flavor": schema.SingleNestedAttribute{
 				Required: true,
@@ -637,6 +632,13 @@ func mapFields(resp *mongodbflex.GetInstanceResponse, model *Model, flavor *flav
 		return fmt.Errorf("creating options: %w", core.DiagsToError(diags))
 	}
 
+	simplifiedModelBackupSchedule := simplifyBackupSchedule(model.BackupSchedule.ValueString())
+	// If the value returned by the API is different from the one in the model after simplification,
+	// we update the model so that it causes an error in Terraform
+	if simplifiedModelBackupSchedule != types.StringPointerValue(instance.BackupSchedule).ValueString() {
+		model.BackupSchedule = types.StringPointerValue(instance.BackupSchedule)
+	}
+
 	idParts := []string{
 		model.ProjectId.ValueString(),
 		instanceId,
@@ -647,7 +649,6 @@ func mapFields(resp *mongodbflex.GetInstanceResponse, model *Model, flavor *flav
 	model.InstanceId = types.StringValue(instanceId)
 	model.Name = types.StringPointerValue(instance.Name)
 	model.ACL = aclList
-	model.BackupSchedule = types.StringPointerValue(instance.BackupSchedule)
 	model.Flavor = flavorObject
 	model.Replicas = conversion.ToTypeInt64(instance.Replicas)
 	model.Storage = storageObject
@@ -781,3 +782,17 @@ func loadFlavorId(ctx context.Context, client mongoDBFlexClient, model *Model, f
 
 	return nil
 }
+
+// Remove leading 0s from backup schedule numbers (e.g. "00 00 * * *" becomes "0 0 * * *")
+// Needed as the API does it internally and would otherwise cause inconsistent result in Terraform
+func simplifyBackupSchedule(schedule string) string {
+	regex := regexp.MustCompile(`0+\d+`) // Matches series of one or more zeros followed by a series of one or more digits
+	simplifiedSchedule := regex.ReplaceAllStringFunc(schedule, func(match string) string {
+		simplified := strings.TrimLeft(match, "0")
+		if simplified == "" {
+			simplified = "0"
+		}
+		return simplified
+	})
+	return simplifiedSchedule
+}

stackit/internal/services/mongodbflex/instance/resource_test.go

@@ -748,3 +748,75 @@ func TestLoadFlavorId(t *testing.T) {
 		})
 	}
 }
+
+func TestSimplifyBackupSchedule(t *testing.T) {
+	tests := []struct {
+		description string
+		input       string
+		expected    string
+	}{
+		{
+			"simple schedule",
+			"0 0 * * *",
+			"0 0 * * *",
+		},
+		{
+			"schedule with leading zeros",
+			"00 00 * * *",
+			"0 0 * * *",
+		},
+		{
+			"schedule with leading zeros 2",
+			"00 001 * * *",
+			"0 1 * * *",
+		},
+		{
+			"schedule with leading zeros 3",
+			"00 0010 * * *",
+			"0 10 * * *",
+		},
+		{
+			"simple schedule with slash",
+			"0 0/6 * * *",
+			"0 0/6 * * *",
+		},
+		{
+			"schedule with leading zeros and slash",
+			"00 00/6 * * *",
+			"0 0/6 * * *",
+		},
+		{
+			"schedule with leading zeros and slash 2",
+			"00 001/06 * * *",
+			"0 1/6 * * *",
+		},
+		{
+			"simple schedule with comma",
+			"0 10,15 * * *",
+			"0 10,15 * * *",
+		},
+		{
+			"schedule with leading zeros and comma",
+			"0 010,0015 * * *",
+			"0 10,15 * * *",
+		},
+		{
+			"simple schedule with comma and slash",
+			"0 0-11/10 * * *",
+			"0 0-11/10 * * *",
+		},
+		{
+			"schedule with leading zeros, comma, and slash",
+			"00 000-011/010 * * *",
+			"0 0-11/10 * * *",
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.description, func(t *testing.T) {
+			output := simplifyBackupSchedule(tt.input)
+			if output != tt.expected {
+				t.Fatalf("Data does not match: %s", output)
+			}
+		})
+	}
+}