// 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 NuGet.Frameworks;
using System;
using System.Collections.Generic;
using System.Linq;

namespace Microsoft.DotNet.Build.Tasks.Packaging;

public class SplitReferences : Task
{
    [Required]
    public ITaskItem[] References
    {
        get;
        set;
    }

    public string TargetFramework
    {
        get;
        set;
    }

    public ITaskItem[] PackageIndexes
    {
        get;
        set;
    }

    [Output]
    public ITaskItem[] PackageReferences
    {
        get;
        set;
    }

    [Output]
    public ITaskItem[] FrameworkReferences
    {
        get;
        set;
    }

    public override bool Execute()
    {
        if (References == null || References.Length == 0)
            return true;

        PackageIndex index = PackageIndexes != null && PackageIndexes.Length > 0 ?
            PackageIndex.Load(PackageIndexes.Select(pi => pi.GetMetadata("FullPath"))) :
            null;

        Dictionary<string, ITaskItem> packageReferences = new Dictionary<string, ITaskItem>();
        Dictionary<string, ITaskItem> assemblyReferences = new Dictionary<string, ITaskItem>();

        bool referencesMscorlib = false;

        NuGetFramework targetFx = NuGetFramework.Parse(TargetFramework);

        foreach (var reference in References)
        {
            string referenceName = reference.ItemSpec;
            referencesMscorlib |= referenceName.Equals("mscorlib");
            string referenceVersion = reference.GetMetadata("Version");
            reference.SetMetadata("TargetFramework", TargetFramework);
            if (!string.IsNullOrEmpty(TargetFramework) && index != null && index.IsInbox(referenceName, targetFx, referenceVersion))
            {
                AddReference(assemblyReferences, reference);
            }
            else
            {
                AddReference(packageReferences, reference);
            }
        }

        if (referencesMscorlib)
        {
            // only add framework references for mscorlib-based assemblies.
            FrameworkReferences = assemblyReferences.Values.ToArray();
        }

        if (packageReferences.Count == 0)
        {
            var emptyItem = new TaskItem("_._");
            emptyItem.SetMetadata("TargetFramework", TargetFramework);
            packageReferences.Add(emptyItem.ItemSpec, emptyItem);
        }

        PackageReferences = packageReferences.Values.ToArray();


        return true;
    }

    private static void AddReference(Dictionary<string, ITaskItem> collection, ITaskItem item)
    {
        ITaskItem existingItem;

        if (collection.TryGetValue(item.ItemSpec, out existingItem))
        {
            Version existingVersion = Version.Parse(existingItem.GetMetadata("Version"));
            Version newVersion = Version.Parse(existingItem.GetMetadata("Version"));

            if (newVersion > existingVersion)
            {
                collection[item.ItemSpec] = item;
            }
        }
        else
        {
            collection[item.ItemSpec] = item;
        }
    }
}