using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Linq;

namespace Vanara.Windows.Shell
{
	/// <summary>A dictionary of Command Verbs defined in the Windows Registry.</summary>
	/// <seealso cref="Vanara.Windows.Shell.RegBasedDictionary{T}"/>
	public class CommandVerbDictionary : RegBasedDictionary<CommandVerb>
	{
		private const string rootKeyName = "shell";
		private readonly RegBasedSettings parent;

		internal CommandVerbDictionary(RegBasedSettings parent, bool readOnly) : base(parent.key.OpenSubKey(rootKeyName, !readOnly), readOnly) => this.parent = parent;

		/// <summary>Gets or sets the default verb.</summary>
		/// <value>The default verb.</value>
		[DefaultValue(null)]
		public string DefaultVerb
		{
			get => key.GetValue(null)?.ToString();
			set { if (ContainsKey(value)) key.SetValue(null, value); else throw new KeyNotFoundException("The command verb specified is not defined."); }
		}

		/// <summary>Get the filtered list of keys under the base.</summary>
		[Browsable(false)]
		public override IEnumerable<string> Keys => key?.GetSubKeyNames() ?? new string[0];

		/// <summary>Gets or sets the order of the command verbs.</summary>
		/// <value>The ordered list of command verbs.</value>
		[Browsable(false)]
		public IList<CommandVerb> Order
		{
			get
			{
				var order = key.GetValue("", null)?.ToString();
				var vals = Values.ToList();
				if (order != null)
				{
					var orderedItems = order.Split(new[] { ',' }, StringSplitOptions.RemoveEmptyEntries);
					for (var i = orderedItems.Length - 1; i >= 0; i--)
					{
						var match = vals.Find(c =>
							string.Equals(c.Name, orderedItems[i], StringComparison.InvariantCultureIgnoreCase));
						if (match == null) continue;
						vals.Remove(match);
						vals.Insert(0, match);
					}
				}
				return vals;
			}
			set
			{
				switch (value?.Count ?? 0)
				{
					case 0:
						key.DeleteValue("", false);
						break;

					case 1:
						key.SetValue("", value.First().Name);
						break;

					default:
						key.SetValue("", string.Join(",", value.Select(c => c.Name).ToArray()));
						break;
				}
			}
		}

		/// <summary>Adds the specified command verb.</summary>
		/// <param name="verb">The command verb name.</param>
		/// <param name="displayName">
		/// The command verb display name. This is the string shown to the user when requesting a context menu for a shell item.
		/// </param>
		/// <param name="command">The command to execute.</param>
		/// <param name="setAsDefault">if set to <see langword="true"/> set this verb as default.</param>
		/// <returns>A <see cref="CommandVerb"/> instance which has been added to the registry.</returns>
		public CommandVerb Add(string verb, string displayName = null, string command = null, bool setAsDefault = false)
		{
			if (key == null && !readOnly)
				key = parent.key.CreateSubKey(rootKeyName);
			var vkey = key.CreateSubKey(verb) ?? throw new InvalidOperationException("Unable to create required key in registry.");
			var v = new CommandVerb(vkey, verb, false) { DisplayName = displayName, Command = command };
			if (setAsDefault) key.SetValue(null, verb);
			return v;
		}

		/// <summary>Determines if a specified key is in the filtered list of keys under the base.</summary>
		/// <param name="verb">The name of the key to check.</param>
		/// <returns><see langword="true" /> if the key is found; otherwise <see langword="false" />.</returns>
		public override bool ContainsKey(string verb) => key?.HasSubKey(verb) ?? false;

		/// <summary>Removes the specified key from this dictionary and the registry.</summary>
		/// <param name="verb">The name of the command verb to remove.</param>
		/// <returns>A value indicating success (<see langword="true"/>) or failure (<see langword="false"/>).</returns>
		public bool Remove(string verb)
		{
			try
			{
				key.DeleteSubKeyTree(verb);
				return true;
			}
			catch
			{
				return false;
			}
		}

		/// <summary>Tries to get the <see cref="CommandVerb"/> with the name <paramref name="verb"/>.</summary>
		/// <param name="verb">The verb name.</param>
		/// <param name="value">On success, the corresponding <see cref="CommandVerb"/> instance; <see langword="null"/> on failure.</param>
		/// <returns>A value indicating if <paramref name="verb"/> was found.</returns>
		public override bool TryGetValue(string verb, out CommandVerb value)
		{
			value = null;
			if (!ContainsKey(verb)) return false;
			value = new CommandVerb(key.OpenSubKey(verb, !readOnly), verb, readOnly);
			return true;
		}
	}
}