using System.Collections.Generic;

namespace Chernobyl.Threading
{
    /// <summary>
    /// A <see cref="DataAccessor"/> for value types. Use this for simple, small
    /// value types (like char, float, small structs, etc) or if you don't have
    /// the time/need for a faster, more powerful <see cref="DataAccessor"/>.
    /// </summary>
    class ValueTypeAccessor<DataType> : DataAccessor<DataType> where DataType : struct
    {
        /// <summary>
        /// Constructor.
        /// </summary>
        /// <param name="attachTo">The <see cref="DataSafe"/> to attach to.</param>
        /// <param name="accessRights">The rights granted to this accessor.</param>
        public ValueTypeAccessor(DataSafe<DataType> attachTo, AccessRights accessRights) : base(attachTo, accessRights)
        {
        }

        /// <summary>
        /// Returns the current value of the held data.
        /// </summary>
        public DataType Read()
        {
            return _theData;
        }

        /// <summary>
        /// Sets the current value of the held data. Only 
        /// call this method when you have to. Fewer calls
        /// to this method will help performance.
        /// </summary>
        public void Write(DataType newValue)
        {
            _theData = newValue;
            MyDataSafe.RecordChange(this, (ref DataType oldValue) => oldValue = _theData);
        }

        /// <summary>
        /// This method is called when the DataSafe is synchronized.
        /// The passed in changeRecords are to be run on the accessors
        /// data so that it can have it's data synchronized with the other
        /// accessors.
        /// </summary>
        /// <param name="changeRecords">The change records to run on the internal
        /// data.</param>
        public override void Synchronize(Queue<DataSafe<DataType>.ChangeRecord> changeRecords)
        {
            foreach (DataSafe<DataType>.ChangeRecord cr in changeRecords)
            {
                cr(ref _theData);
            }
        }

        /// <summary>
        /// A copy of the data in the DataSafe.
        /// </summary>
        DataType _theData;
    }
}