using System;
using System.Text;

namespace YesNt.CodeEditor;

internal class InputHandler(TextEditor textEditor)
{
    private readonly TextEditor textEditor = textEditor;

    public bool HandleInput()
    {
        while (Console.KeyAvailable)
        {
            _ = Console.ReadKey(true);
        }
        if (textEditor.EditMode == Mode.Edit)
        {
            ConsoleKeyInfo keyInfo = Console.ReadKey(true);

            if ((ConsoleModifiers.Alt & keyInfo.Modifiers) == ConsoleModifiers.Alt)
            {
                switch (keyInfo.Key)
                {
                    case ConsoleKey.C:
                        textEditor.EditMode = Mode.Command;
                        return true;

                    case ConsoleKey.B:
                        int position = textEditor.Lines.Count;
                        textEditor.CursorPosition.Y = position - 1;
                        textEditor.LineOffset = Math.Max(position - Console.WindowHeight + 3, 0);

                        textEditor.Display(true);
                        return true;

                    case ConsoleKey.T:
                        textEditor.CursorPosition.Y = 0;
                        textEditor.LineOffset = 0;

                        textEditor.Display(true);
                        return true;

                    case ConsoleKey.S:
                        textEditor.CursorPosition.X = 0;
                        return true;

                    case ConsoleKey.E:
                        textEditor.CursorPosition.X = textEditor.Lines.Count > textEditor.CursorPosition.Y ? textEditor.Lines[textEditor.CursorPosition.Y].TrimEnd().Length : 0;
                        return true;
                }
            }
            if (keyInfo.Key == ConsoleKey.DownArrow)
            {
                textEditor.CursorPosition.Y++;
                if (textEditor.CursorPosition.Y - textEditor.LineOffset >= Console.WindowHeight - 3)
                {
                    textEditor.LineOffset++;
                    textEditor.Display(true);
                }
            }
            else if (keyInfo.Key == ConsoleKey.UpArrow)
            {
                if (textEditor.CursorPosition.Y > 0)
                {
                    textEditor.CursorPosition.Y--;
                    if (textEditor.CursorPosition.Y - textEditor.LineOffset < 0 && textEditor.LineOffset > 0)
                    {
                        textEditor.LineOffset--;
                        textEditor.Display(true);
                    }
                }
            }
            else if (keyInfo.Key == ConsoleKey.LeftArrow)
            {
                if (textEditor.CursorPosition.X > 0)
                {
                    textEditor.CursorPosition.X--;
                }
            }
            else if (keyInfo.Key == ConsoleKey.RightArrow)
            {
                if (textEditor.CursorPosition.X + textEditor.GetSpacing() + 3 < Console.WindowWidth)
                {
                    textEditor.CursorPosition.X++;
                }
            }
            else if (keyInfo.Key == ConsoleKey.Enter)
            {
                while (textEditor.Lines.Count <= textEditor.CursorPosition.Y)
                {
                    textEditor.Lines.Add("");
                }
                textEditor.Lines.Insert(textEditor.CursorPosition.Y, "");

                string line = textEditor.Lines[textEditor.CursorPosition.Y + 1];

                textEditor.Lines[textEditor.CursorPosition.Y] = line[..Math.Min(textEditor.CursorPosition.X, line.Length)];
                textEditor.Lines[textEditor.CursorPosition.Y + 1] = line[Math.Min(textEditor.CursorPosition.X, line.Length)..];

                textEditor.CursorPosition.X = 0;
                textEditor.CursorPosition.Y++;

                if (textEditor.CursorPosition.Y - textEditor.LineOffset >= Console.WindowHeight - 3)
                {
                    textEditor.LineOffset++;
                }
                textEditor.Display(true);
            }
            else
            {
                while (textEditor.Lines.Count <= textEditor.CursorPosition.Y)
                {
                    textEditor.Lines.Add("");
                }

                StringBuilder lineBuilder = new StringBuilder(textEditor.Lines[textEditor.CursorPosition.Y]);
                while (lineBuilder.Length <= textEditor.CursorPosition.X)
                {
                    _ = lineBuilder.Append(' ');
                }

                textEditor.Lines[textEditor.CursorPosition.Y] = lineBuilder.ToString();

                if (keyInfo.Key is ConsoleKey.Backspace or ConsoleKey.Delete)
                {
                    if (keyInfo.Key == ConsoleKey.Delete)
                    {
                        textEditor.CursorPosition.X++;
                    }

                    if (textEditor.CursorPosition.X > 0)
                    {
                        if (textEditor.Lines[textEditor.CursorPosition.Y][textEditor.CursorPosition.X - 1] == ' ' && textEditor.CursorPosition.X > textEditor.Lines[textEditor.CursorPosition.Y].TrimEnd().Length)
                        {
                            textEditor.Lines[textEditor.CursorPosition.Y] = textEditor.Lines[textEditor.CursorPosition.Y].TrimEnd();
                            textEditor.CursorPosition.X = textEditor.Lines[textEditor.CursorPosition.Y].Length;
                        }
                        else
                        {
                            textEditor.Lines[textEditor.CursorPosition.Y] = textEditor.Lines[textEditor.CursorPosition.Y].Remove(textEditor.CursorPosition.X - 1, 1);
                            textEditor.CursorPosition.X--;
                        }
                    }
                    else
                    {
                        if (textEditor.CursorPosition.Y > 0)
                        {
                            if (string.IsNullOrWhiteSpace(textEditor.Lines[textEditor.CursorPosition.Y - 1]))
                            {
                                textEditor.Lines.RemoveAt(--textEditor.CursorPosition.Y);
                            }
                            else
                            {
                                textEditor.CursorPosition.Y--;
                                textEditor.CursorPosition.X = textEditor.Lines[textEditor.CursorPosition.Y].TrimEnd().Length;
                                textEditor.Lines[textEditor.CursorPosition.Y] += textEditor.Lines[textEditor.CursorPosition.Y + 1];
                                textEditor.Lines.RemoveAt(textEditor.CursorPosition.Y + 1);
                            }
                            if (textEditor.CursorPosition.Y - textEditor.LineOffset < 0 && textEditor.LineOffset > 0)
                            {
                                textEditor.LineOffset--;
                            }
                            textEditor.Display(true);
                        }
                    }

                    while (textEditor.Lines.Count > 0 && string.IsNullOrWhiteSpace(textEditor.Lines[^1]))
                    {
                        textEditor.Lines.RemoveAt(textEditor.Lines.Count - 1);
                    }
                }
                else if (textEditor.CursorPosition.X + textEditor.GetSpacing() + 3 < Console.WindowWidth)
                {
                    char input = keyInfo.KeyChar;
                    if (!char.IsControl(input))
                    {
                        textEditor.Lines[textEditor.CursorPosition.Y] = textEditor.Lines[textEditor.CursorPosition.Y].Insert(textEditor.CursorPosition.X, input.ToString());
                        textEditor.CursorPosition.X++;
                    }
                }
            }
        }
        else if (textEditor.EditMode == Mode.Command)
        {
            Console.SetCursorPosition(3, Console.WindowHeight - 2);

            string input = Console.ReadLine() ?? string.Empty;
            string command = input.Split(' ')[0].Trim();
            string path;

            Console.CursorVisible = false;

            switch (command)
            {
                case "edit":
                    WriteStatus(string.Empty);
                    textEditor.EditMode = Mode.Edit;
                    break;

                case "line":
                    WriteStatus(string.Empty);

                    bool success = false;
                    int lineNumber = 0;
                    if (input.Split(' ').Length == 2)
                    {
                        success = int.TryParse(input.Split(' ')[1], out lineNumber);
                    }

                    if (success && lineNumber > 0)
                    {
                        textEditor.CursorPosition.Y = lineNumber - 1;
                        textEditor.CursorPosition.X = 0;
                        textEditor.LineOffset = lineNumber - 1;
                        textEditor.EditMode = Mode.Edit;
                    }
                    else
                    {
                        WriteStatus("Invalid line number!");
                    }
                    break;

                case "save":
                    _ = textEditor.Save(input, false);
                    break;

                case "run":
                    ExecuteWithDebugScreen(input, false, false);
                    break;

                case "debug":
                    if (TryParseDebugCommand(input, out bool stepMode, out string parsedPath))
                    {
                        string saveInput = string.IsNullOrWhiteSpace(parsedPath) ? "debug" : $"debug {parsedPath}";
                        ExecuteWithDebugScreen(saveInput, true, stepMode);
                    }
                    else
                    {
                        WriteStatus("Invalid arguments!");
                    }
                    break;

                case "load":
                    if (input.Split(' ').Length == 2)
                    {
                        path = input.Split(' ')[1];
                    }
                    else
                    {
                        WriteStatus("Invalid arguments!");
                        break;
                    }

                    try
                    {
                        _ = textEditor.Load(path);
                    }
                    catch (Exception ex)
                    {
                        WriteStatus(ex.Message);
                    }
                    textEditor.LineOffset = 0;
                    textEditor.CursorPosition.X = 0;
                    textEditor.CursorPosition.Y = 0;
                    break;

                case "new":

                    textEditor.LineOffset = 0;
                    textEditor.CursorPosition.X = 0;
                    textEditor.CursorPosition.Y = 0;
                    textEditor.CurrentPath = string.Empty;
                    textEditor.Lines.Clear();
                    WriteStatus(string.Empty);
                    break;

                case "exit":
                    return false;

                default:
                    WriteStatus("Command not found!");
                    break;
            }
            textEditor.Display(true);
        }
        return true;
    }

    internal static void WriteStatus(string input)
    {
        Console.SetCursorPosition(0, Console.WindowHeight - 1);
        Console.Write(input + new string(' ', Console.WindowWidth - input.Length - 1));
    }

    private static bool TryParseDebugCommand(string input, out bool stepMode, out string path)
    {
        stepMode = false;
        path = string.Empty;

        string[] parts = input.Split(' ', StringSplitOptions.RemoveEmptyEntries);
        if (parts.Length == 0 || !parts[0].Equals("debug", StringComparison.OrdinalIgnoreCase))
        {
            return false;
        }

        for (int i = 1; i < parts.Length; i++)
        {
            string token = parts[i];
            if (token.Equals("step", StringComparison.OrdinalIgnoreCase))
            {
                if (stepMode)
                {
                    return false;
                }

                stepMode = true;
                continue;
            }

            if (string.IsNullOrWhiteSpace(path))
            {
                path = token;
                continue;
            }

            return false;
        }

        return true;
    }

    private void ExecuteWithDebugScreen(string saveInput, bool debugMode, bool stepMode)
    {
        if (textEditor.Save(saveInput, true))
        {
            textEditor.EditMode = Mode.Debug;
            textEditor.IsStepDebugMode = stepMode;
            Console.Clear();
            Console.CursorVisible = true;

            if (debugMode)
            {
                textEditor.YesNtInterpreter.Execute(textEditor.CurrentPath, true);
            }
            else
            {
                textEditor.YesNtInterpreter.Execute(textEditor.CurrentPath);
            }

            while (Console.KeyAvailable)
            {
                _ = Console.ReadKey(true);
            }
            _ = Console.ReadKey();
            WriteStatus(string.Empty);
            textEditor.IsStepDebugMode = false;
            textEditor.EditMode = Mode.Command;
        }
    }
}