// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.

namespace Microsoft.AspNetCore.Components.Forms;

internal sealed class FieldState
{
    private readonly FieldIdentifier _fieldIdentifier;

    // We track which ValidationMessageStore instances have a nonempty set of messages for this field so that
    // we can quickly evaluate the list of messages for the field without having to query all stores. This is
    // relevant because each validation component may define its own message store, so there might be as many
    // stores are there are fields or UI elements.
    private HashSet<ValidationMessageStore>? _validationMessageStores;

    public FieldState(FieldIdentifier fieldIdentifier)
    {
        _fieldIdentifier = fieldIdentifier;
    }

    public bool IsModified { get; set; }

    // Async validation tracking: the currently-tracked async validation task for this field,
    // the CancellationTokenSource that can cancel it, and whether the last task faulted.
    // EditContext is dispatcher-bound (see remarks on EditContext), so plain reads/writes are
    // sufficient — the dispatcher serializes access and provides the necessary happens-before.
    internal Task? PendingValidationTask { get; set; }
    internal CancellationTokenSource? PendingValidationCts { get; set; }
    internal bool IsValidationFaulted { get; set; }

    public IEnumerable<string> GetValidationMessages()
    {
        if (_validationMessageStores != null)
        {
            foreach (var store in _validationMessageStores)
            {
                foreach (var message in store[_fieldIdentifier])
                {
                    yield return message;
                }
            }
        }
    }

    public void AssociateWithValidationMessageStore(ValidationMessageStore validationMessageStore)
    {
        if (_validationMessageStores == null)
        {
            _validationMessageStores = new HashSet<ValidationMessageStore>();
        }

        _validationMessageStores.Add(validationMessageStore);
    }

    public void DissociateFromValidationMessageStore(ValidationMessageStore validationMessageStore)
        => _validationMessageStores?.Remove(validationMessageStore);
}