// 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.IO;
using System.Security.Cryptography;

namespace Microsoft.DotNet.Arcade.Sdk;

[MSBuildMultiThreadableTask]
public class GenerateChecksums : Task, IMultiThreadableTask
{
    /// <summary>Injected by MSBuild so paths resolve against the project directory in multithreaded builds.</summary>
    public TaskEnvironment TaskEnvironment { get; set; } = TaskEnvironment.Fallback;

    /// <summary>
    /// An item collection of files for which to generate checksums.  Each item must have metadata
    /// 'DestinationPath' that specifies the path of the checksum file to create.
    /// </summary>
    [Required]
    public ITaskItem[] Items { get; set; }

    public override bool Execute()
    {
        foreach (ITaskItem item in Items)
        {
            try
            {
                string destinationPath = item.GetMetadata("DestinationPath");
                if (string.IsNullOrEmpty(destinationPath))
                {
                    Log.LogError($"Metadata 'DestinationPath' is missing for item '{item.ItemSpec}'.");
                    return !Log.HasLoggedErrors;
                }

                // GetAbsolutePath rejects an empty item spec, whereas the File.Exists probe it feeds
                // used to simply report the file as missing.
                if (string.IsNullOrEmpty(item.ItemSpec))
                {
                    Log.LogError($"The file '{item.ItemSpec}' does not exist.");
                    return !Log.HasLoggedErrors;
                }

                AbsolutePath itemPath = TaskEnvironment.GetAbsolutePath(item.ItemSpec);
                if (!File.Exists(itemPath))
                {
                    Log.LogError($"The file '{item.ItemSpec}' does not exist.");
                    return !Log.HasLoggedErrors;
                }

                Log.LogMessage(MessageImportance.High, $"Generating checksum for '{item.ItemSpec}' into '{destinationPath}'...");

                using (FileStream stream = File.OpenRead(itemPath))
                {
                    using(HashAlgorithm hashAlgorithm = SHA512.Create())
                    {
                        byte[] hash = hashAlgorithm.ComputeHash(stream);
                        string checksum = BitConverter.ToString(hash).Replace("-", string.Empty);
                        File.WriteAllText(TaskEnvironment.GetAbsolutePath(destinationPath), checksum);
                    }
                }
            }
            catch (Exception e)
            {
                Log.LogErrorFromException(e);
                return !Log.HasLoggedErrors;
            }
        }

        return !Log.HasLoggedErrors;
    }
}