-- Change only hierarchy fields, preserving location details and aliases.
CREATE OR ALTER PROCEDURE dbo.Location_Reparent
    @ProjectID int,
    @LocationID int,
    @ParentLocationID int,
    @ExpectedParentLocationID int = NULL,
    @UserID int = NULL
AS
BEGIN
    SET NOCOUNT ON;
    SET XACT_ABORT ON;
    BEGIN TRY
        BEGIN TRANSACTION;
        DECLARE @LockedProjectID int, @OldParentID int, @Name nvarchar(200), @ParentName nvarchar(200);
        SELECT @LockedProjectID=ProjectID FROM dbo.Projects WITH (UPDLOCK,HOLDLOCK) WHERE ProjectID=@ProjectID AND IsArchived=0;
        IF @LockedProjectID IS NULL OR @UserID IS NULL OR NOT EXISTS
            (SELECT 1 FROM dbo.ProjectUserAccess WHERE ProjectID=@ProjectID AND UserID=@UserID AND IsActive=1)
            THROW 51000, 'You do not have access to this project.', 1;
        SELECT @Name=LocationName,@OldParentID=ParentLocationID FROM dbo.Locations WITH (UPDLOCK,HOLDLOCK)
        WHERE LocationID=@LocationID AND ProjectID=@ProjectID AND IsArchived=0;
        SELECT @ParentName=LocationName FROM dbo.Locations WITH (UPDLOCK,HOLDLOCK)
        WHERE LocationID=@ParentLocationID AND ProjectID=@ProjectID AND IsArchived=0;
        IF @Name IS NULL OR @ParentName IS NULL
            THROW 51000, 'Choose active locations from the same project.', 1;
        IF ISNULL(@OldParentID,0)<>ISNULL(@ExpectedParentLocationID,0)
            THROW 51000, 'The parent has changed since this page was loaded. Review the updated tree and try again.', 1;
        IF @OldParentID=@ParentLocationID
            THROW 51000, 'This location already has that parent.', 1;
        DECLARE @AncestorID int=@ParentLocationID;
        DECLARE @Visited TABLE (LocationID int PRIMARY KEY);
        WHILE @AncestorID IS NOT NULL
        BEGIN
            IF @AncestorID=@LocationID OR EXISTS (SELECT 1 FROM @Visited WHERE LocationID=@AncestorID)
                THROW 51000, 'A location cannot be its own parent or be moved beneath one of its descendants.', 1;
            INSERT @Visited VALUES (@AncestorID);
            DECLARE @NextAncestorID int=NULL;
            SELECT @NextAncestorID=ParentLocationID FROM dbo.Locations WITH (UPDLOCK,HOLDLOCK) WHERE LocationID=@AncestorID;
            SET @AncestorID=@NextAncestorID;
        END;
        UPDATE dbo.Locations SET ParentLocationID=@ParentLocationID,UpdatedDate=SYSUTCDATETIME(),
            ModifiedDateUTC=SYSUTCDATETIME(),ModifiedByUserID=@UserID WHERE LocationID=@LocationID;
        DECLARE @Description nvarchar(1000)=CONCAT(N'Parent changed from ',
            COALESCE((SELECT LocationName FROM dbo.Locations WHERE LocationID=@OldParentID),N'top level'),N' to ',@ParentName,N'.');
        EXEC dbo.ProjectAudit_Record @ProjectID=@ProjectID,@UserID=@UserID,@ActivityType=N'Updated',
            @EntityType=N'Location',@EntityID=@LocationID,@EntityName=@Name,@Description=@Description;
        COMMIT TRANSACTION;
    END TRY
    BEGIN CATCH
        IF XACT_STATE()<>0 ROLLBACK TRANSACTION;
        THROW;
    END CATCH;
END;
GO