using System;
using System.Collections.Generic;
using System.IO;
using System.Text;
using System.Windows.Forms;

namespace FontPreview
{
	/// <summary>
	/// 字体清单缓存：首次扫描后落盘，后续启动直接读缓存秒显，
	/// 后台再按 文件路径/大小/修改时间 做增量对比，未变化的不重新解析。
	/// </summary>
	public class FontCache
	{
		public struct Stamp
		{
			public long Size;
			public long Mtime;
		}

		public string RootDir;
		public List<FontItem> Items = new List<FontItem>();
		public Dictionary<string, Stamp> Stamps = new Dictionary<string, Stamp>(StringComparer.OrdinalIgnoreCase);

		private static string CachePath => Path.Combine(Path.GetDirectoryName(Application.ExecutablePath), "fontcache.txt");

		public static bool TryLoad(string rootDir, out FontCache cache)
		{
			cache = null;
			try
			{
				if (!File.Exists(CachePath)) return false;
				string[] lines = File.ReadAllLines(CachePath, Encoding.UTF8);
				if (lines.Length < 2 || lines[0] != "#FontCache v1") return false;
				string rd = null;
				for (int i = 0; i < lines.Length; i++)
				{
					if (lines[i].StartsWith("rootdir=")) { rd = lines[i].Substring(8).Trim(); break; }
				}
				if (rd == null || !string.Equals(rd, rootDir.Trim(), StringComparison.OrdinalIgnoreCase)) return false;

				FontCache c = new FontCache();
				c.RootDir = rootDir;
				for (int i = 0; i < lines.Length; i++)
				{
					string l = lines[i];
					if (string.IsNullOrEmpty(l) || l[0] == '#' || l.StartsWith("rootdir=")) continue;
					string[] p = l.Split('\t');
					if (p.Length < 6) continue;
					FontItem it = new FontItem { Cat = p[0], Path = p[1], Name = p[2], DisplayName = p[3] };
					c.Items.Add(it);
					long size, mt;
					if (long.TryParse(p[4], out size) && long.TryParse(p[5], out mt))
					{
						c.Stamps[it.Path] = new Stamp { Size = size, Mtime = mt };
					}
				}
				if (c.Items.Count == 0) return false;
				cache = c;
				return true;
			}
			catch { return false; }
		}

		public static void Save(FontCache c)
		{
			try
			{
				StringBuilder sb = new StringBuilder();
				sb.AppendLine("#FontCache v1");
				sb.AppendLine("rootdir=" + c.RootDir);
				foreach (FontItem it in c.Items)
				{
					Stamp st;
					c.Stamps.TryGetValue(it.Path, out st);
					string dn = (it.DisplayName ?? "").Replace("\t", " ");
					sb.Append(it.Cat).Append('\t').Append(it.Path).Append('\t')
					  .Append(it.Name).Append('\t').Append(dn).Append('\t')
					  .Append(st.Size).Append('\t').Append(st.Mtime).Append('\n');
				}
				string tmp = CachePath + ".tmp";
				File.WriteAllText(tmp, sb.ToString(), new UTF8Encoding(false));
				if (File.Exists(CachePath)) { File.Copy(tmp, CachePath, true); File.Delete(tmp); }
				else { File.Move(tmp, CachePath); }
			}
			catch { }
		}
	}
}