using System;
using System.Collections.Generic;
using System.Windows.Forms;
using DevExpress.XtraEditors;

namespace Lskj.Control.Model
{
    /// <summary>
    /// 将按钮原有的 &amp; 助记键改为必须按 Alt 才能触发的快捷键。
    /// </summary>
    public sealed class AltButtonShortcutManager
    {
        private sealed class ShortcutItem
        {
            public SimpleButton Button;
            public Keys Key;
        }

        private readonly List<ShortcutItem> mShortcutItems =
            new List<ShortcutItem>();
        private bool mUpdatingText;

        /// <summary>
        /// 注册按钮快捷键，并移除标题中的 &amp;，保持界面显示为“按钮名(X)”。
        /// </summary>
        public void Register(SimpleButton button, Keys defaultKey)
        {
            if (button == null)
            {
                return;
            }

            ShortcutItem item = mShortcutItems.Find(
                shortcut => ReferenceEquals(shortcut.Button, button));
            if (item == null)
            {
                item = new ShortcutItem { Button = button, Key = defaultKey };
                mShortcutItems.Add(item);
                button.TextChanged += OnButtonTextChanged;
            }

            UpdateShortcut(item, defaultKey);
        }

        /// <summary>
        /// 只响应 Alt+原助记键；未按 Alt、同时按下其他修饰键时均不处理。
        /// </summary>
        public bool ProcessKey(Keys keyData)
        {
            if ((keyData & Keys.Modifiers) != Keys.Alt)
            {
                return false;
            }

            Keys keyCode = keyData & Keys.KeyCode;
            foreach (ShortcutItem item in mShortcutItems)
            {
                SimpleButton button = item.Button;
                if (item.Key == keyCode && button != null &&
                    !button.IsDisposed && button.Visible && button.Enabled)
                {
                    button.PerformClick();
                    return true;
                }
            }

            return false;
        }

        private void OnButtonTextChanged(object sender, EventArgs e)
        {
            if (mUpdatingText)
            {
                return;
            }

            SimpleButton button = sender as SimpleButton;
            ShortcutItem item = mShortcutItems.Find(
                shortcut => ReferenceEquals(shortcut.Button, button));
            if (item != null)
            {
                UpdateShortcut(item, item.Key);
            }
        }

        private void UpdateShortcut(ShortcutItem item, Keys defaultKey)
        {
            string text = item.Button.Text ?? string.Empty;
            int mnemonicIndex = FindMnemonicIndex(text);
            if (mnemonicIndex >= 0)
            {
                item.Key = (Keys)char.ToUpperInvariant(text[mnemonicIndex + 1]);
                mUpdatingText = true;
                try
                {
                    item.Button.Text = text.Remove(mnemonicIndex, 1);
                }
                finally
                {
                    mUpdatingText = false;
                }
            }
            else
            {
                item.Key = defaultKey;
            }
        }

        private static int FindMnemonicIndex(string text)
        {
            for (int index = 0; index < text.Length - 1; index++)
            {
                if (text[index] == '&' && char.IsLetterOrDigit(text[index + 1]))
                {
                    return index;
                }
            }

            return -1;
        }
    }
}