using System;
using System.Collections.Generic;
using iTextSharp.text.pdf;
using Microsoft.Win32;
using CharSet = System.Runtime.InteropServices.CharSet;
using DllImport = System.Runtime.InteropServices.DllImportAttribute;

namespace PDFPatcher.Common
{
	static class FontHelper
	{
		public static string FontDirectory { get; } = System.IO.Path.GetFullPath(Environment.GetFolderPath(Environment.SpecialFolder.System) + "\\..\\fonts\\");

		/// <summary>
		/// 列出已安装的字体及其路径。
		/// </summary>
		/// <param name="includeFamilyName">是否包含字体组名称</param>
		public static Dictionary<string, string> GetInstalledFonts(bool includeFamilyName) {
			var d = new Dictionary<string, string>(50);
			using (var k = Registry.LocalMachine.OpenSubKey(@"SOFTWARE\Microsoft\Windows NT\CurrentVersion\Fonts")) {
				GetFontsFromRegistryKey(includeFamilyName, d, k);
			}
			using (var k = Registry.CurrentUser.OpenSubKey(@"SOFTWARE\Microsoft\Windows NT\CurrentVersion\Fonts")) {
				GetFontsFromRegistryKey(includeFamilyName, d, k);
			}
			return d;
		}

		static void GetFontsFromRegistryKey(bool includeFamilyName, Dictionary<string, string> d, RegistryKey k) {
			if (k is null) {
				return;
			}
			foreach (var name in k.GetValueNames()) {
				if (name is null) {
					continue;
				}
				var p = k.GetValue(name) as string;
				if (String.IsNullOrEmpty(p)) {
					continue;
				}
				if (p.IndexOf('\\') == -1) {
					p = FontDirectory + p;
				}
				var fp = new FilePath(p);
				try {
					if (fp.HasExtension(Constants.FileExtensions.Ttf)
						|| fp.HasExtension(Constants.FileExtensions.Otf)) {
						AddFontNames(d, p, includeFamilyName);
					}
					else if (fp.HasExtension(Constants.FileExtensions.Ttc)) {
						var nl = BaseFont.EnumerateTTCNames(p).Length;
						for (int i = 0; i < nl; i++) {
							AddFontNames(d, p + "," + i.ToText(), includeFamilyName);
						}
					}
				}
				catch (System.IO.IOException) {
					// ignore
				}
				catch (NullReferenceException) {
				}
				catch (iTextSharp.text.DocumentException) {
					// ignore
				}
			}
		}

		static void AddFontNames(Dictionary<string, string> fontNames, string fontPath, bool includeFamilyName) {
			var nl = BaseFont.GetAllFontNames(fontPath, "Cp936", null);
			if (includeFamilyName) {
				AddFontName(fontNames, nl[0] as string, fontPath);
			}
			var ffn = nl[2] as string[][];
			string n = null;
			string nn = null, cn = null;
			foreach (var fn in ffn) {
				var enc = fn[2];
				n = fn[3];
				if ("2052" == enc) {
					cn = n;
					break;
				}
				if ("1033" == enc) {
					nn = n;
				}
				else if ("0" == enc && nn == null) {
					nn = n;
				}
			}
			if (n != null) {
				AddFontName(fontNames, cn ?? nn ?? n, fontPath);
			}
		}

		static void AddFontName(Dictionary<string, string> fontNames, string name, string path) {
			if (!String.IsNullOrEmpty(name)) {
				fontNames[name] = path;
			}
		}

		static class NativeMethods
		{
			[DllImport("Gdi32.dll", CharSet = CharSet.Unicode)]
			private static extern int AddFontResourceEx(string fontPath, int flag, IntPtr preserved);
			[DllImport("Gdi32.dll", CharSet = CharSet.Unicode)]
			private static extern int RemoveFontResourceEx(string fontPath, int flag, IntPtr preserved);

			internal static int LoadFont(string path) {
				return AddFontResourceEx(path, 0x10, IntPtr.Zero);
			}
			internal static int RemoveFont(string path) {
				return RemoveFontResourceEx(path, 0x10, IntPtr.Zero);
			}
		}
	}
}