using System;
using System.Runtime.InteropServices;
using Vanara.Extensions;
using Vanara.InteropServices;

namespace Vanara.PInvoke
{
	public static partial class Shell32
	{
		/// <summary>Describes how a property should be treated.</summary>
		[PInvokeData("Shtypes.h")]
		[Flags]
		public enum SHCOLSTATE
		{
			/// <summary>The value is displayed according to default settings for the column.</summary>
			SHCOLSTATE_DEFAULT = 0x00000000,

			/// <summary>The value is displayed as a string.</summary>
			SHCOLSTATE_TYPE_STR = 0x00000001,

			/// <summary>The value is displayed as an integer.</summary>
			SHCOLSTATE_TYPE_INT = 0x00000002,

			/// <summary>The value is displayed as a date/time.</summary>
			SHCOLSTATE_TYPE_DATE = 0x00000003,

			/// <summary>A mask for display type values SHCOLSTATE_TYPE_STR, SHCOLSTATE_TYPE_STR, and SHCOLSTATE_TYPE_DATE.</summary>
			SHCOLSTATE_TYPEMASK = 0x0000000f,

			/// <summary>The column should be on by default in Details view.</summary>
			SHCOLSTATE_ONBYDEFAULT = 0x00000010,

			/// <summary>Will be slow to compute. Perform on a background thread.</summary>
			SHCOLSTATE_SLOW = 0x00000020,

			/// <summary>Provided by a handler, not the folder.</summary>
			SHCOLSTATE_EXTENDED = 0x00000040,

			/// <summary>Not displayed in the context menu, but is listed in the More... dialog.</summary>
			SHCOLSTATE_SECONDARYUI = 0x00000080,

			/// <summary>Not displayed in the UI.</summary>
			SHCOLSTATE_HIDDEN = 0x00000100,

			/// <summary>VarCmp produces same result as IShellFolder::CompareIDs.</summary>
			SHCOLSTATE_PREFER_VARCMP = 0x00000200,

			/// <summary>PSFormatForDisplay produces same result as IShellFolder::CompareIDs.</summary>
			SHCOLSTATE_PREFER_FMTCMP = 0x00000400,

			/// <summary>Do not sort folders separately.</summary>
			SHCOLSTATE_NOSORTBYFOLDERNESS = 0x00000800,

			/// <summary>Only displayed in the UI.</summary>
			SHCOLSTATE_VIEWONLY = 0x00010000,

			/// <summary>Marks columns with values that should be read in a batch.</summary>
			SHCOLSTATE_BATCHREAD = 0x00020000,

			/// <summary>Grouping is disabled for this column.</summary>
			SHCOLSTATE_NO_GROUPBY = 0x00040000,

			/// <summary>Can't resize the column.</summary>
			SHCOLSTATE_FIXED_WIDTH = 0x00001000,

			/// <summary>The width is the same in all dpi.</summary>
			SHCOLSTATE_NODPISCALE = 0x00002000,

			/// <summary>Fixed width and height ratio.</summary>
			SHCOLSTATE_FIXED_RATIO = 0x00004000,

			/// <summary>Filters out new display flags.</summary>
			SHCOLSTATE_DISPLAYMASK = 0x0000F000,
		}

		/// <summary>A value that specifies the desired format of the string.</summary>
		[PInvokeData("Shtypes.h", MSDNShortId = "bb759820")]
		public enum STRRET_TYPE : uint
		{
			/// <summary>The string is at the address specified by pOleStr member.</summary>
			STRRET_WSTR = 0x0000,

			/// <summary>
			/// The uOffset member value indicates the number of bytes from the beginning of the item identifier list where the string is located.
			/// </summary>
			STRRET_OFFSET = 0x0001,

			/// <summary>The string is returned in the cStr member.</summary>
			STRRET_CSTR = 0x0002,
		}

		/// <summary>Contains a list of item identifiers.</summary>
		[StructLayout(LayoutKind.Sequential)]
		[PInvokeData("Shtypes.h", MSDNShortId = "bb773321")]
		public struct ITEMIDLIST
		{
			/// <summary>A list of item identifiers.</summary>
			public SHITEMID mkid;
		}

		/// <summary>Reports detailed information on an item in a Shell folder.</summary>
		[StructLayout(LayoutKind.Sequential)]
		[PInvokeData("Shtypes.h", MSDNShortId = "bb759781")]
		public struct SHELLDETAILS
		{
			/// <summary>The alignment of the column heading and the subitem text in the column.</summary>
			public ComCtl32.ListViewColumnFormat fmt;

			/// <summary>he number of average-sized characters in the header.</summary>
			public int cxChar;

			/// <summary>
			/// An STRRET structure that includes a string with the requested information. To convert this structure to a string, use
			/// StrRetToBuf or StrRetToStr.
			/// </summary>
			public STRRET str;
		}

		/// <summary>Defines an item identifier.</summary>
		[StructLayout(LayoutKind.Sequential)]
		[PInvokeData("Shtypes.h", MSDNShortId = "bb759800")]
		public struct SHITEMID
		{
			/// <summary>The size of identifier, in bytes, including <see cref="cb"/> itself.</summary>
			public ushort cb;

			/// <summary>A variable-length item identifier.</summary>
			public byte[] abID;
		}

		/// <summary>Contains strings returned from the IShellFolder interface methods.</summary>
		[StructLayout(LayoutKind.Explicit, Size = 264)]
		[PInvokeData("Shtypes.h", MSDNShortId = "bb759820")]
		public struct STRRET
		{
			/// <summary>A value that specifies the desired format of the string.</summary>
			[FieldOffset(0)]
			public STRRET_TYPE uType;

			/// <summary>
			/// A pointer to the string. This memory must be allocated with CoTaskMemAlloc. It is the calling application's responsibility to
			/// free this memory with CoTaskMemFree when it is no longer needed.
			/// </summary>
			[FieldOffset(4)]
			public StrPtrUni pOleStr; // must be freed by caller of GetDisplayNameOf

			/// <summary>The offset into the item identifier list.</summary>
			[FieldOffset(4)]
			public uint uOffset; // Offset into SHITEMID

			/// <summary>The buffer to receive the display name. CHAR[MAX_PATH]</summary>
			[FieldOffset(4)]
			public StrPtrAnsi cStr;

			/// <summary>Performs an implicit conversion from <see cref="STRRET"/> to <see cref="System.String"/>.</summary>
			/// <param name="s">The <see cref="STRRET"/> instance.</param>
			/// <returns>The result of the conversion.</returns>
			public static implicit operator string(in STRRET s) => 
				ShlwApi.StrRetToBSTR(new PinnedObject(s), default, out var ret).Succeeded ? ret : null;

			/// <summary>Returns a <see cref="string"/> that represents this instance.</summary>
			/// <returns>A <see cref="string"/> that represents this instance.</returns>
			public override string ToString() => (string)this ?? "";
		}

		internal class STRRETMarshaler : ICustomMarshaler
		{
			public static ICustomMarshaler GetInstance(string cookie) => new STRRETMarshaler();

			public void CleanUpManagedData(object ManagedObj)
			{
			}

			public void CleanUpNativeData(IntPtr pNativeData)
			{
				if (pNativeData == IntPtr.Zero) return;
				pNativeData.ToStructure<STRRET>().pOleStr.Free();
				Marshal.FreeCoTaskMem(pNativeData);
			}

			public int GetNativeDataSize() => Marshal.SizeOf(typeof(STRRET));

			public IntPtr MarshalManagedToNative(object ManagedObj)
			{
				if (!(ManagedObj is string s)) throw new InvalidCastException();
				var sr = new STRRET { uType = STRRET_TYPE.STRRET_WSTR };
				sr.pOleStr.Assign(s);
				return sr.MarshalToPtr(Marshal.AllocCoTaskMem, out var _);
			}

			public object MarshalNativeToManaged(IntPtr pNativeData) => 
				pNativeData != IntPtr.Zero && ShlwApi.StrRetToBSTR(pNativeData, default, out var ret).Succeeded ? ret : null;
		}
	}
}