pushy/Pushy/Pushy/Grains/TextItemGrain.cs

using Orleans.Concurrency;

namespace Pushy.Grains;

public sealed class TextItem
{
    public string? Text { get; set; }
}

public interface ITextItem : IGrainWithStringKey
{
    [Alias("IsAvailable")]
    public ValueTask<bool> IsAvailable();

    [Alias("SetText")]
    public ValueTask SetText(string text);
    
    [ReadOnly]
    [return: Immutable]
    [AlwaysInterleave]
    [Alias("GetText")]
    ValueTask<string> GetText();
}

public sealed class TextItemGrain : Grain, ITextItem, IRemindable
{
    private readonly IPersistentState<TextItem> _state;
    private IGrainReminder _reminder;

    public TextItemGrain(
        [PersistentState("text")] IPersistentState<TextItem> state)
    {
        _state = state;
    }

    /// <inheritdoc />
    public override async Task OnActivateAsync(CancellationToken cancellationToken)
    {
        _reminder = await this.RegisterOrUpdateReminder("clear", TimeSpan.FromDays(10), TimeSpan.FromDays(10));
    }

    /// <inheritdoc />
    public ValueTask<bool> IsAvailable()
    {
        return ValueTask.FromResult(_state.State.Text is null);
    }

    /// <inheritdoc />
    public async ValueTask SetText(string text)
    {
        if(_state.State.Text is not null)
            throw new InvalidOperationException("Text is already set");
        
        _state.State.Text = text;
        await _state.WriteStateAsync();
    }

    /// <inheritdoc />
    public ValueTask<string> GetText()
    {
        return ValueTask.FromResult(_state.State.Text!);
    }

    /// <inheritdoc />
    public async Task ReceiveReminder(string reminderName, TickStatus status)
    {
        if (reminderName == "clear")
        {
            _state.State.Text = null;
            await _state.WriteStateAsync();
        }
    }
}