using System;
using System.IO;
using System.IO.Abstractions;
using System.Text;

namespace Terminal.Gui {
	/// <summary>
	/// Determines which symbol to use to represent files and directories.
	/// </summary>
	public class FileSystemIconProvider {
		/// <summary>
		/// <para>
		/// Gets or sets a flag indicating whether to use Nerd Font icons.
		/// Defaults to <see cref="NerdFonts.Enable"/> which can be configured
		/// by end users from their <c>./.tui/config.json</c> 
		/// via <see cref="ConfigurationManager"/>.
		/// </para>
		/// <remarks>Enabling <see cref="UseNerdIcons"/> implicitly
		/// disables <see cref="UseUnicodeCharacters"/>.</remarks>
		/// </summary>
		public bool UseNerdIcons {
			get => _useNerdIcons; set {
				_useNerdIcons = value;
				if (value) {
					UseUnicodeCharacters = false;
				}
			}
		}
		/// <summary>
		/// Gets or sets a flag indicating whether to use common unicode
		/// characters for file/directory icons.
		/// </summary>
		public bool UseUnicodeCharacters {
			get => _useUnicodeCharacters;
			set { 
				_useUnicodeCharacters = value;
				if (value) {
					UseNerdIcons = false;
				}
			}
		}

		private NerdFonts _nerd = new NerdFonts ();
		private bool _useNerdIcons = NerdFonts.Enable;
		private bool _useUnicodeCharacters;

		/// <summary>
		/// Gets or sets the delegate to be used to determine opened state of directories
		/// when resolving <see cref="GetIcon(IFileSystemInfo)"/>.  Defaults to always false.
		/// </summary>
		public Func<IDirectoryInfo, bool> IsOpenGetter { get; set; } = (d) => false;

		/// <summary>
		/// Returns the character to use to represent <paramref name="fileSystemInfo"/> or an empty
		/// space if no icon should be used.
		/// </summary>
		/// <param name="fileSystemInfo">The file or directory requiring an icon.</param>
		/// <returns></returns>
		public Rune GetIcon (IFileSystemInfo fileSystemInfo)
		{
			if (UseNerdIcons) {
				return new Rune (
					_nerd.GetNerdIcon (
						fileSystemInfo,
						fileSystemInfo is IDirectoryInfo dir ? IsOpenGetter (dir) : false
					));
			}

			if (fileSystemInfo is IDirectoryInfo) {
				return UseUnicodeCharacters ? ConfigurationManager.Glyphs.Folder : new Rune (Path.DirectorySeparatorChar);
			}

			return UseUnicodeCharacters ? ConfigurationManager.Glyphs.File : new Rune (' ');
		}
		
		/// <summary>
		/// Returns <see cref="GetIcon(IFileSystemInfo)"/> with an extra
		/// space on the end if icon is likely to overlap adjacent cells.
		/// </summary>
		public string GetIconWithOptionalSpace(IFileSystemInfo fileSystemInfo)
		{
			var space = UseNerdIcons ? " " : "";
			return GetIcon(fileSystemInfo) + space;
		}
	}
}