using System;
using System.Text.Json;
using System.Text.Json.Serialization;
using System.Threading.Tasks;

namespace Kruzya.TelegramBot.Core.Option;

public class OptionItem<T> : IOptionItem<T>
{
    public IOptionKey Key { get; }

    public T Value
    {
        get => _value;

        set
        {
            _value = value;
            _isChanged = true;
        }
    }

    public bool IsChanged => _isChanged;

    private T _value;
    private bool _isChanged;

    public OptionItem(IOptionKey key, T value)
    {
        Key = key;
        Value = value;
    }

    public async Task LoadAsync(IOptionStorageAdapter adapter)
    {
        var savedValue = await adapter.LoadValueAsync(Key);
        if (savedValue == null)
        {
            return;
        }

        // This property changed when we're loaded default value. Reset here.
        _isChanged = false;
        _value = JsonSerializer.Deserialize<T>(new ReadOnlySpan<byte>(savedValue));
    }

    public async Task SaveAsync(IOptionStorageAdapter adapter)
    {
        var data = JsonSerializer.SerializeToUtf8Bytes(Value, new JsonSerializerOptions { WriteIndented = false, 
            DefaultIgnoreCondition = JsonIgnoreCondition.WhenWritingNull });
        await adapter.SaveValueAsync(Key, data);
    }
}