// Copyright (c) Microsoft Corporation
// The Microsoft Corporation licenses this file to you under the MIT license.
// See the LICENSE file in the project root for more information.

using System.Text.Json.Serialization;
using CommunityToolkit.Mvvm.ComponentModel;

namespace Microsoft.CmdPal.UI.ViewModels;

public partial class RecentCommandsManager : ObservableObject, IRecentCommandsManager
{
    [JsonInclude]
    internal List<HistoryItem> History { get; set; } = [];

    private readonly Lock _lock = new();

    public RecentCommandsManager()
    {
    }

    public int GetCommandHistoryWeight(string commandId)
    {
        lock (_lock)
        {
            var entry = History
            .Index()
            .Where(item => item.Item.CommandId == commandId)
            .FirstOrDefault();

            // These numbers are vaguely scaled so that "VS" will make "Visual Studio" the
            // match after one use.
            // Usually it has a weight of 84, compared to 109 for the VS cmd prompt
            if (entry.Item is not null)
            {
                var index = entry.Index;

                // First, add some weight based on how early in the list this appears
                var bucket = index switch
                {
                    var i when index <= 2 => 35,
                    var i when index <= 10 => 25,
                    var i when index <= 15 => 15,
                    var i when index <= 35 => 10,
                    _ => 5,
                };

                // Then, add weight for how often this is used, but cap the weight from usage.
                var uses = Math.Min(entry.Item.Uses * 5, 35);

                return bucket + uses;
            }

            return 0;
        }
    }

    public void AddHistoryItem(string commandId)
    {
        lock (_lock)
        {
            var entry = History
            .Where(item => item.CommandId == commandId)
            .FirstOrDefault();
            if (entry is null)
            {
                var newitem = new HistoryItem() { CommandId = commandId, Uses = 1 };
                History.Insert(0, newitem);
            }
            else
            {
                History.Remove(entry);
                entry.Uses++;
                History.Insert(0, entry);
            }

            if (History.Count > 50)
            {
                History.RemoveRange(50, History.Count - 50);
            }
        }
    }
}

public interface IRecentCommandsManager
{
    int GetCommandHistoryWeight(string commandId);

    void AddHistoryItem(string commandId);
}