using System;
using System.Runtime.InteropServices;
using System.Text;
using TBL.CSharp.Base;

namespace TBL.CSharp.Game.Server.Utilities;

/// <summary>
/// 字节块
/// </summary>
public readonly unsafe struct ByteBlock
{
    /// <summary>
    /// 空字节块
    /// </summary>
    public static readonly ByteBlock Empty = new ByteBlock((void*) 0, 0);
    
    /// <summary>
    /// 地址
    /// </summary>
    public readonly void* Address;

    /// <summary>
    /// 字节尺寸
    /// </summary>
    public readonly int Size;

    public ByteBlock(void* ptr, int size)
    {
        Address = ptr;
        Size = size;
    }

    /// <summary>
    /// 是否在空指针
    /// </summary>
    public bool IsNullPtr => (void*) 0 == Address;

    /// <summary>
    /// 释放
    /// <para>不要重复进行释放操作</para>
    /// </summary>
    public void Free()
    {
        Marshal.FreeHGlobal(new IntPtr(Address));
    }

    /// <summary>
    /// 分配所需尺寸的字节块
    /// </summary>
    public static ByteBlock Alloc(int size) => new ByteBlock(Marshal.AllocHGlobal(size).ToPointer(), size);

    /// <summary>
    /// 分配所需尺寸的字节块并复制指定内容
    /// </summary>
    public static ByteBlock AllocWithCopy(void* source, int size)
    {
        var block = Alloc(size);
        Buffer.MemoryCopy(source, block.Address, size, size);
        return block;
    }

    /// <summary>
    /// 分配装载一个非托管值的字节块
    /// </summary>
    public static ByteBlock AllocWithValue<T>(T value) where T : unmanaged
    {
        var block = Alloc(sizeof(T));
        *(T*) block.Address = value;
        return block;
    }

    /// <summary>
    /// 分配装载一个字符串的字节块
    /// </summary>
    public static ByteBlock AllocWithString(string str)
    {
        fixed(void* ptr = str)
        {
            return AllocWithCopy(ptr, Encoding.Default.GetByteCount(str));
        }
    }

    /// <summary>
    /// 分配所需尺寸的字节块并初始化内容
    /// </summary>
    public static ByteBlock AllocWithInitialize(int size, Extension.OnBufferUse initializer)
    {
        var block = Alloc(size);
        initializer(block.Address);
        return block;
    }
}