namespace GMap.NET.Internals
{
    using System;
    using System.Collections.Generic;
    using System.Diagnostics;
    using System.Threading;

    /// <summary>
    /// represent tile
    /// </summary>
    public struct Tile : IDisposable
    {
        public static readonly Tile Empty = new Tile();

        GPoint pos;
        int zoom;
        PureImage[] overlays;
        long OverlaysCount;

        public readonly bool NotEmpty;

        public Tile(int zoom, GPoint pos)
        {
            this.NotEmpty = true;
            this.zoom = zoom;
            this.pos = pos;
            this.overlays = null;
            this.OverlaysCount = 0;
        }

        public IEnumerable<PureImage> Overlays
        {
            get
            {
#if PocketPC
                for (long i = 0, size = OverlaysCount; i < size; i++)
#else
                for (long i = 0, size = Interlocked.Read(ref OverlaysCount); i < size; i++)
#endif
                {
                    yield return overlays[i];
                }
            }
        }

        internal void AddOverlay(PureImage i)
        {
            if (overlays == null)
            {
                overlays = new PureImage[4];
            }
#if !PocketPC
            overlays[Interlocked.Increment(ref OverlaysCount) - 1] = i;
#else
            overlays[++OverlaysCount - 1] = i;
#endif
        }

        internal bool HasAnyOverlays
        {
            get
            {
#if PocketPC
                return OverlaysCount > 0;
#else
                return Interlocked.Read(ref OverlaysCount) > 0;
#endif
            }
        }

        public int Zoom
        {
            get
            {
                return zoom;
            }
            private set
            {
                zoom = value;
            }
        }

        public GPoint Pos
        {
            get
            {
                return pos;
            }
            private set
            {
                pos = value;
            }
        }

        #region IDisposable Members

        public void Dispose()
        {
            if (overlays != null)
            {
#if PocketPC
                for (long i = OverlaysCount - 1; i >= 0; i--)

#else
                for (long i = Interlocked.Read(ref OverlaysCount) - 1; i >= 0; i--)
#endif
                {
#if !PocketPC
                    Interlocked.Decrement(ref OverlaysCount);
#else
                    OverlaysCount--;
#endif
                    overlays[i].Dispose();
                    overlays[i] = null;
                }
                overlays = null;
            }
        }

        #endregion

        public static bool operator ==(Tile m1, Tile m2)
        {
            return m1.pos == m2.pos && m1.zoom == m2.zoom;
        }

        public static bool operator !=(Tile m1, Tile m2)
        {
            return !(m1 == m2);
        }

        public override bool Equals(object obj)
        {
            return base.Equals(obj);
        }

        public override int GetHashCode()
        {
            return base.GetHashCode();
        }
    }
}