using Netcode;

namespace StardewModdingAPI.Framework.StateTracking.FieldWatchers
{
    /// <summary>A watcher which detects changes to a net value field.</summary>
    /// <typeparam name="TValue">The value type wrapped by the net field.</typeparam>
    /// <typeparam name="TNetField">The net field type.</typeparam>
    internal class NetValueWatcher<TValue, TNetField> : BaseDisposableWatcher, IValueWatcher<TValue> where TNetField : NetFieldBase<TValue, TNetField>
    {
        /*********
        ** Fields
        *********/
        /// <summary>The field being watched.</summary>
        private readonly NetFieldBase<TValue, TNetField> Field;


        /*********
        ** Accessors
        *********/
        /// <summary>Whether the value changed since the last reset.</summary>
        public bool IsChanged { get; private set; }

        /// <summary>The field value at the last reset.</summary>
        public TValue PreviousValue { get; private set; }

        /// <summary>The latest value.</summary>
        public TValue CurrentValue { get; private set; }


        /*********
        ** Public methods
        *********/
        /// <summary>Construct an instance.</summary>
        /// <param name="field">The field to watch.</param>
        public NetValueWatcher(NetFieldBase<TValue, TNetField> field)
        {
            this.Field = field;
            this.PreviousValue = field.Value;
            this.CurrentValue = field.Value;

            field.fieldChangeVisibleEvent += this.OnValueChanged;
            field.fieldChangeEvent += this.OnValueChanged;
        }

        /// <summary>Update the current value if needed.</summary>
        public void Update()
        {
            this.AssertNotDisposed();
        }

        /// <summary>Set the current value as the baseline.</summary>
        public void Reset()
        {
            this.AssertNotDisposed();

            this.PreviousValue = this.CurrentValue;
            this.IsChanged = false;
        }

        /// <summary>Stop watching the field and release all references.</summary>
        public override void Dispose()
        {
            if (!this.IsDisposed)
            {
                this.Field.fieldChangeEvent -= this.OnValueChanged;
                this.Field.fieldChangeVisibleEvent -= this.OnValueChanged;
            }
            base.Dispose();
        }


        /*********
        ** Private methods
        *********/
        /// <summary>A callback invoked when the field's value changes.</summary>
        /// <param name="field">The field being watched.</param>
        /// <param name="oldValue">The old field value.</param>
        /// <param name="newValue">The new field value.</param>
        private void OnValueChanged(TNetField field, TValue oldValue, TValue newValue)
        {
            this.CurrentValue = newValue;
            this.IsChanged = true;
        }
    }
}