using System;
using System.Collections;
using System.Collections.Generic;
using System.Linq;
using System.Runtime.InteropServices;
using Vanara.PInvoke;
using static Vanara.PInvoke.Ole32;
using static Vanara.PInvoke.PropSys;

namespace Vanara.Windows.Shell
{
	/// <summary>Encapsulates the IPropertyStore object.</summary>
	/// <seealso cref="IDictionary{PROPERTYKEY, Object}"/>
	/// <seealso cref="System.IDisposable"/>
	public abstract class ReadOnlyPropertyStore : IReadOnlyDictionary<PROPERTYKEY, object>, IDisposable
	{
		/// <summary>The IPropertyStore instance.</summary>
		protected IPropertyStore iPropertyStore;

		private PropertyDescriptionDictionary descriptions;

		/// <summary>Initializes a new instance of the <see cref="PropertyStore"/> class.</summary>
		protected ReadOnlyPropertyStore() { }

		/// <summary>Gets the number of properties in the current property store.</summary>
		public int Count => Run(ps => (int)(ps?.GetCount() ?? 0));

		/// <summary>Value that allows matching this property store's keys to their property descriptions.</summary>
		/// <value>The property descriptions.</value>
		public virtual IReadOnlyDictionary<PROPERTYKEY, PropertyDescription> Descriptions => descriptions ??= new PropertyDescriptionDictionary(this);

		/// <summary>Gets a value indicating whether the <see cref="ICollection{T}"/> is read-only.</summary>
		public virtual bool IsReadOnly => true;

		/// <summary>Gets an <see cref="IEnumerable{T}"/> containing the keys of the <see cref="IReadOnlyDictionary{PROPERTYKEY, Object}"/>.</summary>
		public IEnumerable<PROPERTYKEY> Keys => Run(ps => GetKeyEnum(ps).ToList());

		/// <summary>Gets an <see cref="IEnumerable{T}"/> containing the values in the <see cref="IReadOnlyDictionary{PROPERTYKEY, Object}"/>.</summary>
		public IEnumerable<object> Values => Run(ps => GetKeyEnum(ps).Select(k => TryGetValue(ps, k, out object v) ? v : null).ToList());

		/// <summary>Gets or sets the value of the property with the specified known key.</summary>
		/// <value>The value.</value>
		/// <param name="knownKey">The known key of the property (e.g. "System.Title"}.</param>
		/// <returns>The value of the property.</returns>
		public virtual object this[string knownKey] => this[GetPropertyKeyFromName(knownKey)];

		/// <summary>Gets or sets the value of the property with the specified PROPERTYKEY.</summary>
		/// <value>The value.</value>
		/// <param name="key">The PROPERTYKEY of the property.</param>
		/// <returns>The value of the property.</returns>
		public virtual object this[PROPERTYKEY key] => TryGetValue(key, out var r) ? r : null;

		/// <summary>Gets the property key for a canonical property name.</summary>
		/// <param name="name">A property name.</param>
		/// <returns>The requested property key.</returns>
		public static PROPERTYKEY GetPropertyKeyFromName(string name)
		{
			if (name is null) throw new ArgumentNullException(nameof(name));
			var hr = PSGetPropertyKeyFromName(name, out var pk);
			if (hr == HRESULT.TYPE_E_ELEMENTNOTFOUND) throw new ArgumentOutOfRangeException(nameof(name));
			hr.ThrowIfFailed();
			return pk;
		}

		/// <summary>Determines whether the <see cref="IDictionary{PROPERTYKEY, Object}"/> contains an element with the specified key.</summary>
		/// <param name="key">The key to locate in the <see cref="IDictionary{PROPERTYKEY, Object}"/>.</param>
		/// <returns>true if the <see cref="IDictionary{PROPERTYKEY, Object}"/> contains an element with the key; otherwise, false.</returns>
		public bool ContainsKey(PROPERTYKEY key) => Keys.Contains(key);

		/// <summary>
		/// Copies the elements of the <see cref="ICollection{T}"/> to an <see cref="T:System.Array"/>, starting at a particular <see
		/// cref="T:System.Array"/> index.
		/// </summary>
		/// <param name="array">
		/// The one-dimensional <see cref="T:System.Array"/> that is the destination of the elements copied from <see
		/// cref="ICollection{T}"/>. The <see cref="T:System.Array"/> must have zero-based indexing.
		/// </param>
		/// <param name="arrayIndex">The zero-based index in <paramref name="array"/> at which copying begins.</param>
		/// <exception cref="ArgumentOutOfRangeException">arrayIndex - The number of items exceeds the length of the supplied array.</exception>
		/// <exception cref="ArgumentNullException">array</exception>
		public void CopyTo(KeyValuePair<PROPERTYKEY, object>[] array, int arrayIndex)
		{
			if (array.Length < (arrayIndex + Count))
				throw new ArgumentOutOfRangeException(nameof(arrayIndex), "The number of items exceeds the length of the supplied array.");
			if (array is null)
				throw new ArgumentNullException(nameof(array));
			var i = arrayIndex;
			foreach (var kv in this)
				array[i++] = kv;
		}

		/// <summary>Performs application-defined tasks associated with freeing, releasing, or resetting unmanaged resources.</summary>
		public virtual void Dispose()
		{
			if (iPropertyStore is not null)
			{
				Marshal.FinalReleaseComObject(iPropertyStore);
				iPropertyStore = null;
			}
		}

		/// <summary>Gets the property.</summary>
		/// <typeparam name="TVal">The type of the value.</typeparam>
		/// <param name="key">The key.</param>
		/// <returns>The cast value of the property.</returns>
		/// <exception cref="ArgumentOutOfRangeException">key</exception>
		public TVal GetProperty<TVal>(PROPERTYKEY key) => TryGetValue<TVal>(key, out var ret) ? ret : throw new ArgumentOutOfRangeException(nameof(key));

		/// <summary>Gets the property description related to a property key.</summary>
		/// <param name="key">The key.</param>
		/// <returns>The related property description, if one exists; otherwise <see langword="null"/>.</returns>
		public PropertyDescription GetPropertyDescription(PROPERTYKEY key) => PropertyDescription.Create(key);

		/// <summary>Gets the string value of the property.</summary>
		/// <param name="key">The key.</param>
		/// <param name="flags">The formatting flags.</param>
		/// <returns>The string value of the property.</returns>
		/// <exception cref="ArgumentOutOfRangeException">key</exception>
		public string GetPropertyString(PROPERTYKEY key, PROPDESC_FORMAT_FLAGS flags = PROPDESC_FORMAT_FLAGS.PDFF_DEFAULT)
		{
			using var pv = GetPropVariant(key);
			return PropertyDescription.Create(key)?.FormatForDisplay(pv, flags);
		}

		/// <summary>Gets the PROPVARIANT value for a key.</summary>
		/// <param name="key">The key.</param>
		/// <returns>The PROPVARIANT value.</returns>
		/// <exception cref="ArgumentOutOfRangeException">key</exception>
		public PROPVARIANT GetPropVariant(PROPERTYKEY key)
		{
			return Run(ps =>
			{
				var pv = new PROPVARIANT();
				ps.GetValue(key, pv);
				return pv;
			});
		}

		/// <summary>Gets the value associated with the specified key.</summary>
		/// <param name="key">The key whose value to get.</param>
		/// <param name="value">
		/// When this method returns, the value associated with the specified key, if the key is found; otherwise, the default value for the
		/// type of the <paramref name="value"/> parameter. This parameter is passed uninitialized.
		/// </param>
		/// <returns>
		/// <see langword="true"/> if the object that implements <see cref="IDictionary{PROPERTYKEY, Object}"/> contains an element with the
		/// specified key; otherwise, <see langword="false"/>.
		/// </returns>
		public bool TryGetValue(PROPERTYKEY key, out object value) => TryGetValue<object>(key, out value);

		/// <summary>Gets the value associated with the specified key.</summary>
		/// <typeparam name="TVal">The type of the returned value.</typeparam>
		/// <param name="key">The key whose value to get.</param>
		/// <param name="value">
		/// When this method returns, the value associated with the specified key, if the key is found; otherwise, the default value for the
		/// type of the <paramref name="value"/> parameter. This parameter is passed uninitialized.
		/// </param>
		/// <returns>
		/// <see langword="true"/> if the object that implements <see cref="IDictionary{PROPERTYKEY, Object}"/> contains an element with the
		/// specified key; otherwise, <see langword="false"/>.
		/// </returns>
		public virtual bool TryGetValue<TVal>(PROPERTYKEY key, out TVal value)
		{
			var result = Run(ps =>
			{
				var ret = TryGetValue<TVal>(ps, key, out var val);
				return (ret, ret ? val : default);
			});
			value = result.Item2;
			return result.ret;
		}

		/// <summary>Returns an enumerator that iterates through the collection.</summary>
		/// <returns>A <see cref="T:System.Collections.Generic.IEnumerator`1"/> that can be used to iterate through the collection.</returns>
		IEnumerator<KeyValuePair<PROPERTYKEY, object>> IEnumerable<KeyValuePair<PROPERTYKEY, object>>.GetEnumerator() => (Run(ps => GetKeyEnum(ps).Select(k => new KeyValuePair<PROPERTYKEY, object>(k, TryGetValue(ps, k, out object pv) ? pv : null))) ?? new KeyValuePair<PROPERTYKEY, object>[0]).GetEnumerator();

		/// <summary>Returns an enumerator that iterates through a collection.</summary>
		/// <returns>An <see cref="T:System.Collections.IEnumerator"/> object that can be used to iterate through the collection.</returns>
		IEnumerator IEnumerable.GetEnumerator() => ((IEnumerable<KeyValuePair<PROPERTYKEY, object>>)this).GetEnumerator();

		/// <summary>Gets the value associated with the specified key.</summary>
		/// <param name="ps">The IPropertyStore instance.</param>
		/// <param name="key">The key whose value to get.</param>
		/// <param name="value">
		/// When this method returns, the value associated with the specified key, if the key is found; otherwise, <c>default(T)</c>.
		/// </param>
		/// <returns><see langword="true"/> if the property store contains an element with the specified key; otherwise, <see langword="false"/>.</returns>
		protected static bool TryGetValue<T>(IPropertyStore ps, PROPERTYKEY key, out T value)
		{
			var ret = ps.GetValue(key);
			value = ret is null ? default : (T)ret;
			return ret is not null;
		}

		/// <summary>The IPropertyStore instance. This can be null.</summary>
		protected virtual IPropertyStore GetIPropertyStore() => iPropertyStore;

		/// <summary>Gets an enumeration of the keys in the property store.</summary>
		/// <returns>Keys in the property store.</returns>
		protected virtual IEnumerable<PROPERTYKEY> GetKeyEnum(IPropertyStore ps)
		{
			if (ps is null) yield break;
			for (uint i = 0; i < Count; i++)
				yield return ps.GetAt(i);
		}

		/// <summary>Runs the specified action with a retrived IPropertyStore instance.</summary>
		/// <param name="action">The action to run.</param>
		protected void Run(Action<IPropertyStore> action)
		{
			iPropertyStore ??= GetIPropertyStore();
			if (iPropertyStore is null) return;
			action(iPropertyStore);
		}

		/// <summary>Runs the specified action with a retrived IPropertyStore instance.</summary>
		/// <typeparam name="T">The return type of the action and method.</typeparam>
		/// <param name="action">The action to run.</param>
		/// <returns>The return value from <paramref name="action"/>.</returns>
		protected T Run<T>(Func<IPropertyStore, T> action)
		{
			iPropertyStore ??= GetIPropertyStore();
			return iPropertyStore is null ? default : action.Invoke(iPropertyStore);
		}

		private class PropertyDescriptionDictionary : IReadOnlyDictionary<PROPERTYKEY, PropertyDescription>
		{
			private ReadOnlyPropertyStore store;

			public PropertyDescriptionDictionary(ReadOnlyPropertyStore ps) => store = ps;

			public IEnumerable<PropertyDescription> Values => store.Keys.Select(k => store.GetPropertyDescription(k)).ToList();

			public int Count => store.Count;

			public IEnumerable<PROPERTYKEY> Keys => store.Keys;

			public PropertyDescription this[PROPERTYKEY key] => store.GetPropertyDescription(key);

			public bool ContainsKey(PROPERTYKEY key) => store.ContainsKey(key);

			public IEnumerator<KeyValuePair<PROPERTYKEY, PropertyDescription>> GetEnumerator() =>
				store.Keys.Select(k => new KeyValuePair<PROPERTYKEY, PropertyDescription>(k, store.GetPropertyDescription(k))).ToList().GetEnumerator();

			public bool TryGetValue(PROPERTYKEY key, out PropertyDescription value)
			{
				if (store.ContainsKey(key))
				{
					value = this[key];
					return true;
				}
				value = null;
				return false;
			}

			IEnumerator IEnumerable.GetEnumerator() => GetEnumerator();
		}
	}
}