using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Drawing;
using System.Data;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.Runtime.InteropServices;

namespace IconFreeArrangementPanel
{
    public partial class FreeListView : ListView
    {
        [DllImport("comctl32.dll")]
        private static extern bool ImageList_BeginDrag(IntPtr imageList,
                                                       int index, int x, int y);
        [DllImport("comctl32.dll")]
        private static extern void ImageList_EndDrag();
        [DllImport("comctl32.dll")]
        private static extern bool ImageList_DragEnter(IntPtr window, int x, int y);
        [DllImport("comctl32.dll")]
        private static extern bool ImageList_DragLeave(IntPtr window);
        [DllImport("comctl32.dll")]
        private static extern bool ImageList_DragMove(int x, int y);
        [DllImport("comctl32.dll")]
        private static extern bool ImageList_Destroy(IntPtr imgaeList);
        [DllImport("comctl32.dll")]
        private static extern IntPtr ImageList_Merge(IntPtr imgaeList1, int index1,
                                                     IntPtr imageList2, int index2,
                                                     int x, int y);
        private IntPtr dragImage;
        /// <summary> ドラッグする前のクリック位置(X座標) </summary>
        private int pointX;
        /// <summary> ドラッグする前のクリック位置(Y座標) </summary>
        private int pointY;
        
        /// <summary>
        /// コンストラクタ
        /// </summary>
        public FreeListView()
        {
            InitializeComponent();
        }

        public FreeListView(string imageDir)
            : this()
        {
            string[] jpgFiles =
              System.IO.Directory.GetFiles(imageDir, "*.jpg");

            int width = 100;
            int height = 80;

            imageList1.ImageSize = new Size(width, height);
            this.LargeImageList = imageList1;

            Image original = null;
            Image thumbnail = null;

            for (int i = 0; i < jpgFiles.Length; i++)
            {
                original = Bitmap.FromFile(jpgFiles[i]);
                thumbnail = this.createThumbnail(original, width, height);

                // ImageListのImage設定
                imageList1.Images.Add(thumbnail);
                // ListViewのラベル設定
                this.Items.Add("Item" + i, i);

                original.Dispose();
                //thumbnail.Dispose();
            }
        }

        /// <summary>
        /// 幅w、高さhのImageオブジェクトを作成
        /// </summary>
        /// <param name="image"></param>
        /// <param name="w"></param>
        /// <param name="h"></param>
        /// <returns></returns>
        public Image createThumbnail(Image image, int w, int h)
        {
            Bitmap canvas = new Bitmap(w, h);

            Graphics g = Graphics.FromImage(canvas);
            g.FillRectangle(new SolidBrush(Color.White), 0, 0, w, h);

            float fw = (float)w / (float)image.Width;
            float fh = (float)h / (float)image.Height;

            float scale = Math.Min(fw, fh);
            fw = image.Width * scale;
            fh = image.Height * scale;

            g.DrawImage(image, (w - fw) / 2, (h - fh) / 2, fw, fh);
            g.Dispose();

            return canvas;
        }

        /// <summary>
        /// ドラッグ開始
        /// </summary>
        /// <param name="e"></param>
        protected override void OnItemDrag(ItemDragEventArgs e)
        {
            base.OnItemDrag(e);
            const int LvmCreateDragImage = 0x1000 + 33;
            Point pos = Point.Empty;
            foreach (ListViewItem item in this.SelectedItems)
            {                
                IntPtr pp = Marshal.AllocCoTaskMem(Marshal.SizeOf(typeof(Point)));
                Message m = Message.Create(this.Handle, LvmCreateDragImage,
                                           new IntPtr(item.Index), pp);
                this.WndProc(ref m);
                Point p = (Point)Marshal.PtrToStructure(pp, typeof(Point));
                Marshal.FreeCoTaskMem(pp);
                if (this.dragImage.Equals(IntPtr.Zero))
                {
                    this.dragImage = m.Result;
                    pos = p;
                }
                else
                {
                    IntPtr old = this.dragImage;
                    this.dragImage = ImageList_Merge(old, 0, m.Result, 0,
                                                     p.X - pos.X, p.Y - pos.Y);
                    ImageList_Destroy(old);
                    ImageList_Destroy(m.Result);
                }
            }
            Point view = this.PointToClient(Control.MousePosition);
            ImageList_BeginDrag(dragImage, 0, view.X - pos.X, view.Y - pos.Y);
            ImageList_DragEnter(this.Handle, view.X, view.Y);
        }

        /// <summary>
        /// コントロール上を移動
        /// </summary>
        /// <param name="e"></param>
        protected override void OnMouseMove(MouseEventArgs e)
        {
            base.OnMouseMove(e);
            if (dragImage != IntPtr.Zero)
            {
                ImageList_DragMove(e.X, e.Y);
            }
        }

        /// <summary>
        /// マウスボタンが離された(ドラッグ終了)
        /// </summary>
        /// <param name="e"></param>
        protected override void OnMouseUp(MouseEventArgs e)
        {
            base.OnMouseUp(e);
            if (dragImage != IntPtr.Zero)
            {
                ImageList_DragLeave(this.Handle);
                ImageList_EndDrag();
                ImageList_Destroy(dragImage);
                dragImage = IntPtr.Zero;
                
                foreach (ListViewItem srcItem in this.SelectedItems)
                {
                    // ドロップ位置から挿入位置となるインデックス値を決定する
                    ListViewItem item = this.GetItemAt(e.X, e.Y);
                    int destIndex = this.Items.IndexOf(item);

                    // 項目の範囲外でドロップしたときは、最後尾に追加する様にインデックス値を設定
                    if (destIndex < 0)
                    {
                        destIndex = this.Items.Count;
                    }
                    else if (destIndex > srcItem.Index)
                    {                        
                        destIndex++;
                    }

                    ListViewItem newItem = this.Items.Insert(destIndex, (ListViewItem)srcItem.Clone());
                    newItem.Selected = true;
                    this.Items.Remove(srcItem);
                }
            }
        }
    }
}