IdShiftGenerator.cs

// Copyright (c) 2026 Phoenix Contact GmbH & Co. KG
// Licensed under the Apache License, Version 2.0

namespace Moryx.ControlSystem.ProcessEngine;

/// <summary>
/// Generates database ids for processes and activities based on their
/// parents id and children count at the time of creation
/// </summary>
internal static class IdShiftGenerator
{
    /// <summary>
    /// Number of bits for each generation shift (parent id -> child id)
    /// </summary>
    public const int ShiftSpace = 14;

    /// <summary>
    /// Maximum amount of children is limited by the shift space
    /// </summary>
    public const int MaxAmount = (int.MaxValue >> (31 - ShiftSpace));

    /// <summary>
    /// Shifts the parent id to the left and adds the children count
    /// </summary>
    public static long Generate(long parentId, int count)
    {
#pragma warning disable CS0675 // Bitwise-or operator used on a sign-extended operand
        return parentId << ShiftSpace | count;
#pragma warning restore CS0675 // Bitwise-or operator used on a sign-extended operand
    }

    /// <summary>
    /// Extract the parent id from a combined key
    /// </summary>
    public static long ExtractParent(long combinedKey)
    {
        return combinedKey >> ShiftSpace;
    }

    /// <summary>
    /// Extract the child index from the combined key
    /// </summary>
    public static long ExtractChild(long combinedKey)
    {
        var mask = uint.MaxValue;
        mask >>= (32 - ShiftSpace);
        return combinedKey & mask;
    }
}