// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.

using Microsoft.Build.Framework;
using Microsoft.Build.Utilities;
using System;
using System.Security.Cryptography;

namespace Microsoft.DotNet.Build.Tasks.Installers;

[MSBuildMultiThreadableTask]
public class GenerateGuidFromName : Task
{
    [Required]
    public string Name { get; set; }

    [Output]
    public string GeneratedGuid { get; set; }

    // Generate a Version 5 (SHA1 Name Based) Guid from a name.
    public override bool Execute()
    {
        // Any fixed GUID will do for a namespace.
        Guid namespaceId = new Guid("28F1468D-672B-489A-8E0C-7C5B3030630C");

        using (SHA1 hasher = SHA1.Create()) // lgtm [cs/weak-crypto] Algorithm is required by UUIDv5 spec
        {
            var nameBytes = System.Text.Encoding.UTF8.GetBytes(Name ?? string.Empty);
            var namespaceBytes = namespaceId.ToByteArray();

            SwapGuidByteOrder(namespaceBytes);

            var streamToHash = new byte[namespaceBytes.Length + nameBytes.Length];

            Array.Copy(namespaceBytes, streamToHash, namespaceBytes.Length);
            Array.Copy(nameBytes, 0, streamToHash, namespaceBytes.Length, nameBytes.Length);

            var hashResult = hasher.ComputeHash(streamToHash);

            var res = new byte[16];

            Array.Copy(hashResult, res, res.Length);

            unchecked { res[6] = (byte)(0x50 | (res[6] & 0x0F)); }
            unchecked { res[8] = (byte)(0x40 | (res[8] & 0x3F)); }

            SwapGuidByteOrder(res);

            GeneratedGuid = (new Guid(res)).ToString();
        }

        return true;
    }

    // Do a byte order swap, .NET GUIDs store multi byte components in little
    // endian.
    private static void SwapGuidByteOrder(byte[] b)
    {
        Swap(b, 0, 3);
        Swap(b, 1, 2);
        Swap(b, 5, 6);
        Swap(b, 7, 8);
    }

    private static void Swap(byte[] b, int x, int y)
    {
        byte t = b[x];
        b[x] = b[y];
        b[y] = t;
    }
}