using System;
using System.Collections.Generic;

namespace Sog
{
    //结构对象需要实现这个接口
    public interface IStructObject
    {
        int GetObjectID();
        void SetObjectID(int id);
        bool IsNull();//空结构，代替空指针，表示无效
    }

    public class StructMemoryCache<ST> where ST : struct, IStructObject
    {
        //数组
        private ST m_empty;
        private ST[] m_array;
        private int[] m_indexStat;

        public Queue<long> m_freeQueue = new Queue<long>();

        public StructMemoryCache(long count)
        {
            m_empty.SetObjectID(-1);

            m_array = new ST[count];
            m_indexStat = new int[count];

            //第一个默认为空，不要动了

            ref ST tobject1 = ref m_array[0];
            tobject1.SetObjectID(-1);

            for (int i = 1; i < m_array.Length; i++)
            {
                //设置ID
                ref ST tobject = ref m_array[i];
                tobject.SetObjectID(i);

                //对象id为0的不要了，方便代码处理,0表示无效
                m_freeQueue.Enqueue(i);

            }
        }

        public int GetTotalCount()
        {
            return m_array.Length;
        }       
        public int GetFreeCount()
        {
            return m_freeQueue.Count;
        }

        public int GetUsedCount()
        {
            return GetTotalCount() - GetFreeCount();
        }

        public ref ST Malloc()
        {
            if (m_freeQueue.Count == 0)
            {
                TraceLog.Error("StructMemoryCache.Malloc no free space");
                return ref m_empty;
            }

            long index = m_freeQueue.Dequeue();
            if (m_indexStat[index] == 1)
            {
                TraceLog.Error("StructMemoryCache.Malloc index {0} already be used", index);
                return ref m_empty;
            }

            m_indexStat[index] = 1;
            m_array[index].SetObjectID((int)index);

            return ref m_array[index];
        }

        // 自己管理index时, 不要调用Free, 也不要和Malloc()混用
        // 最好不要自己管理index
        public ref ST Malloc(long index)
        {
            if (m_freeQueue.Count == 0)
            {
                TraceLog.Error("StructMemoryCache.Malloc no free space");
                return ref m_empty;
            }

            if (m_indexStat[index] == 1)
            {
                TraceLog.Error("StructMemoryCache.Malloc index {0} already be used", index);
                return ref m_empty;
            }

            m_indexStat[index] = 1;
            m_array[index].SetObjectID((int)index);

            return ref m_array[index];
        }

        public void Free(ref ST tobject)
        {
            int index = tobject.GetObjectID();
            if (m_indexStat[index] == 0)
            {
                return;
            }

            // objectId也必须清空
            m_array[index].SetObjectID(-1);

            m_indexStat[index] = 0;

            m_freeQueue.Enqueue(index);
        }

        public void Free(long index)
        {
            if (m_indexStat[index] == 0)
            {
                return;
            }

            // objectId也必须清空
            m_array[index].SetObjectID(-1);

            m_indexStat[index] = 0;

            m_freeQueue.Enqueue(index);
        }

        public ref ST GetByIndex(long index)
        {
            if (index >= m_indexStat.Length)
            {
                TraceLog.Trace("StructMemoryCache.GetByIndex index {0} is too large", index);
                return ref m_empty;
            }
            if (m_indexStat[index] == 0)
            {
                //太多日志了
                //TraceLog.Error("StructMemoryCache.GetByIndex index {0} is free, invalid", index);
                return ref m_empty;
            }
            return ref m_array[index];
        }

        public int GetUsedPercent()
        {
            if (GetTotalCount() > 0)
            {
                return Convert.ToInt32(GetUsedCount() * 100.0 / GetTotalCount());
            }

            return 0;
        }

        public int GetUsedIndex(int startIdx)
        {
            for (int i = startIdx; i < m_indexStat.Length; i++)
            {
                if (m_indexStat[i] > 0)
                {
                    return i;
                }
            }

            return 0;
        }
    }
}