using System.Text;
using System;
using System.Diagnostics;
using System.Threading.Tasks;

namespace Terminal.Gui;

/// <summary>
/// Provides cut, copy, and paste support for the OS clipboard.
/// </summary>
/// <remarks>
/// <para>
/// On Windows, the <see cref="Clipboard"/> class uses the Windows Clipboard APIs via P/Invoke.
/// </para>
/// <para>
/// On Linux, when not running under Windows Subsystem for Linux (WSL),
/// the <see cref="Clipboard"/> class uses the xclip command line tool. If xclip is not installed,
/// the clipboard will not work.
/// </para>
/// <para>
/// On Linux, when running under Windows Subsystem for Linux (WSL),
/// the <see cref="Clipboard"/> class launches Windows' powershell.exe via WSL interop and uses the
/// "Set-Clipboard" and "Get-Clipboard" Powershell CmdLets. 
/// </para>
/// <para>
/// On the Mac, the <see cref="Clipboard"/> class uses the MacO OS X pbcopy and pbpaste command line tools
/// and the Mac clipboard APIs vai P/Invoke.
/// </para>
/// </remarks>
public static class Clipboard {
	static string _contents = string.Empty;

		/// <summary>
		/// Gets (copies from) or sets (pastes to) the contents of the OS clipboard.
		/// </summary>
		public static string Contents {
			get {
				try {
					if (IsSupported) {
						var clipData = Application.Driver.Clipboard.GetClipboardData ();
						if (clipData == null) {
							// throw new InvalidOperationException ($"{Application.Driver.GetType ().Name}.GetClipboardData returned null instead of string.Empty");
							clipData = string.Empty;
						}
						_contents = clipData;
					}
				} catch (Exception) {
					_contents = string.Empty;
				}
				return _contents;
			}
			set {
				try {
					if (IsSupported) {
						if (value == null) {
							value = string.Empty;
						}
						Application.Driver.Clipboard.SetClipboardData (value);
					}
					_contents = value;
				} catch (NotSupportedException e) {
					throw e;
				} catch (Exception) {
					_contents = value;
				}
			}
		}

	/// <summary>
	/// Returns true if the environmental dependencies are in place to interact with the OS clipboard.
	/// </summary>
	/// <remarks>
	/// </remarks>
	public static bool IsSupported { get => Application.Driver.Clipboard.IsSupported; }

	/// <summary>
	/// Copies the _contents of the OS clipboard to <paramref name="result"/> if possible.
	/// </summary>
	/// <param name="result">The _contents of the OS clipboard if successful, <see cref="string.Empty"/> if not.</param>
	/// <returns><see langword="true"/> the OS clipboard was retrieved, <see langword="false"/> otherwise.</returns>
	public static bool TryGetClipboardData (out string result)
	{
		if (IsSupported && Application.Driver.Clipboard.TryGetClipboardData (out result)) {
			if (_contents != result) {
				_contents = result;
			}
			return true;
		}
		result = string.Empty;
		return false;
	}

	/// <summary>
	/// Pastes the <paramref name="text"/> to the OS clipboard if possible.
	/// </summary>
	/// <param name="text">The text to paste to the OS clipboard.</param>
	/// <returns><see langword="true"/> the OS clipboard was set, <see langword="false"/> otherwise.</returns>
	public static bool TrySetClipboardData (string text)
	{
		if (IsSupported && Application.Driver.Clipboard.TrySetClipboardData (text)) {
			_contents = text;
			return true;
		}
		return false;
	}
}

/// <summary>
/// Helper class for console drivers to invoke shell commands to interact with the clipboard.
/// Used primarily by CursesDriver, but also used in Unit tests which is why it is in
/// ConsoleDriver.cs.
/// </summary>
internal static class ClipboardProcessRunner {
	public static (int exitCode, string result) Bash (string commandLine, string inputText = "", bool waitForOutput = false)
	{
		var arguments = $"-c \"{commandLine}\"";
		var (exitCode, result) = Process ("bash", arguments, inputText, waitForOutput);

		return (exitCode, result.TrimEnd ());
	}

	public static (int exitCode, string result) Process (string cmd, string arguments, string input = null, bool waitForOutput = true)
	{
		var output = string.Empty;

		using (Process process = new Process {
			StartInfo = new ProcessStartInfo {
				FileName = cmd,
				Arguments = arguments,
				RedirectStandardOutput = true,
				RedirectStandardError = true,
				RedirectStandardInput = true,
				UseShellExecute = false,
				CreateNoWindow = true,
			}
		}) {
			var eventHandled = new TaskCompletionSource<bool> ();
			process.Start ();
			if (!string.IsNullOrEmpty (input)) {
				process.StandardInput.Write (input);
				process.StandardInput.Close ();
			}

			if (!process.WaitForExit (5000)) {
				var timeoutError = $@"Process timed out. Command line: {process.StartInfo.FileName} {process.StartInfo.Arguments}.";
				throw new TimeoutException (timeoutError);
			}

			if (waitForOutput && process.StandardOutput.Peek () != -1) {
				output = process.StandardOutput.ReadToEnd ();
			}

			if (process.ExitCode > 0) {
				output = $@"Process failed to run. Command line: {cmd} {arguments}.
										Output: {output}
										Error: {process.StandardError.ReadToEnd ()}";
			}

			return (process.ExitCode, output);
		}
	}

	public static bool DoubleWaitForExit (this System.Diagnostics.Process process)
	{
		var result = process.WaitForExit (500);
		if (result) {
			process.WaitForExit ();
		}
		return result;
	}

	public static bool FileExists (this string value)
	{
		return !string.IsNullOrEmpty (value) && !value.Contains ("not found");
	}
}