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

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

namespace Microsoft.DotNet.Build.Tasks.Installers;

/// <summary>
/// Produce an md5sums file for a set of files.
/// </summary>
/// <remarks>
/// Emits a file of the format specified by https://manpages.debian.org/bookworm/dpkg-dev/deb-md5sums.5.en.html
/// </remarks>
[MSBuildMultiThreadableTask]
public sealed class CreateMD5SumsFile : Task, IMultiThreadableTask
{
    /// <summary>Injected by MSBuild so paths resolve against the project directory in multithreaded builds.</summary>
    public TaskEnvironment TaskEnvironment { get; set; } = TaskEnvironment.Fallback;

    [Required]
    public string RootDirectory { get; set; }
    [Required]
    public ITaskItem[] Files { get; set; }
    [Required]
    public string OutputFile { get; set; }

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

    public override bool Execute()
    {
        using FileStream outputFile = File.Create(TaskEnvironment.GetAbsolutePath(OutputFile));
        using StreamWriter writer = new(outputFile, Encoding.ASCII);
        ulong installedSize = 0;
        foreach (ITaskItem file in Files)
        {
            using MD5 md5 = MD5.Create();
            using FileStream fileStream = File.OpenRead(TaskEnvironment.GetAbsolutePath(file.ItemSpec));
            installedSize += (ulong)fileStream.Length;
            byte[] hash = md5.ComputeHash(fileStream);
            string relativePath = file.ItemSpec.Substring(RootDirectory.Length).TrimStart(Path.DirectorySeparatorChar).Replace('\\', '/');
            // Always use Linux line-endings
            writer.Write($"{Convert.ToHexStringLower(hash)}  {relativePath}\n");
        }

        InstalledSize = (installedSize / 1024).ToString();

        return true;
    }
}