using System.Threading;
using WIDESEAWCS_S7Simulator.Core.Interfaces;

namespace WIDESEAWCS_S7Simulator.Core.Memory
{
    /// <summary>
    /// 内存区域基类
    /// </summary>
    public abstract class MemoryRegion : IMemoryRegion
    {
        /// <summary>
        /// 内存数据
        /// </summary>
        protected readonly byte[] _memory;

        /// <summary>
        /// 读写锁（支持并发访问）
        /// </summary>
        protected readonly ReaderWriterLockSlim _lock;

        /// <summary>
        /// 释放状态标志
        /// </summary>
        protected bool _disposed = false;

        /// <summary>
        /// 区域类型
        /// </summary>
        public abstract string RegionType { get; }

        /// <summary>
        /// 区域大小（字节）
        /// </summary>
        public int Size { get; }

        /// <summary>
        /// 构造函数
        /// </summary>
        /// <param name="size">区域大小</param>
        protected MemoryRegion(int size)
        {
            Size = size;
            _memory = new byte[size];
            _lock = new ReaderWriterLockSlim(LockRecursionPolicy.SupportsRecursion);
        }

        /// <summary>
        /// 读取字节数据
        /// </summary>
        public virtual byte[] Read(ushort offset, ushort length)
        {
            if (_disposed)
                throw new ObjectDisposedException(nameof(MemoryRegion));

            _lock.EnterReadLock();
            try
            {
                if (offset + length > Size)
                    throw new ArgumentOutOfRangeException(
                        $"读取超出{RegionType}区范围: offset={offset}, length={length}, size={Size}");

                byte[] result = new byte[length];
                Array.Copy(_memory, offset, result, 0, length);
                return result;
            }
            finally
            {
                _lock.ExitReadLock();
            }
        }

        /// <summary>
        /// 写入字节数据
        /// </summary>
        public virtual void Write(ushort offset, byte[] data)
        {
            if (_disposed)
                throw new ObjectDisposedException(nameof(MemoryRegion));

            if (data == null)
                throw new ArgumentNullException(nameof(data));

            _lock.EnterWriteLock();
            try
            {
                if (offset + data.Length > Size)
                    throw new ArgumentOutOfRangeException(
                        $"写入超出{RegionType}区范围: offset={offset}, length={data.Length}, size={Size}");

                Array.Copy(data, 0, _memory, offset, data.Length);
            }
            finally
            {
                _lock.ExitWriteLock();
            }
        }

        /// <summary>
        /// 清空区域
        /// </summary>
        public virtual void Clear()
        {
            if (_disposed)
                throw new ObjectDisposedException(nameof(MemoryRegion));

            _lock.EnterWriteLock();
            try
            {
                Array.Clear(_memory, 0, Size);
            }
            finally
            {
                _lock.ExitWriteLock();
            }
        }

        /// <summary>
        /// 释放资源
        /// </summary>
        public void Dispose()
        {
            Dispose(true);
            GC.SuppressFinalize(this);
        }

        /// <summary>
        /// 释放资源
        /// </summary>
        /// <param name="disposing">是否正在释放托管资源</param>
        protected virtual void Dispose(bool disposing)
        {
            if (!_disposed)
            {
                if (disposing)
                {
                    _lock?.Dispose();
                }
                _disposed = true;
            }
        }
    }
}