using System;
using System.Collections.Generic;
using System.Numerics;

namespace AcDream.App.UI;

/// <summary>
/// Editable one-line chat input. Port of retail <c>UIElement_Text</c> editable
/// one-line mode + <c>ChatInterface</c>'s 100-entry command history. Caret is a
/// glyph index; the caret pixel-X is Σ glyph advances (UiDatFont) to the caret.
/// Submit (Enter / Send) fires <see cref="OnSubmit"/>, clears, and pushes history.
/// Decomp: UIElement_Text MoveCursor @0x468d00, FindPixelsFromPos @0x472b40;
/// ChatInterface ProcessCommand @0x4f5100 (history cap 100, sentinel 0xFFFFFFFF).
/// </summary>
public sealed class UiChatInput : UiElement
{
    public UiDatFont? DatFont { get; set; }
    public AcDream.App.Rendering.BitmapFont? Font { get; set; }
    public Vector4 TextColor { get; set; } = new(1f, 1f, 1f, 1f);
    public Vector4 BackgroundColor { get; set; } = new(0f, 0f, 0f, 0.35f);
    public float Padding { get; set; } = 4f;
    public int MaxCharacters { get; set; } = 0xFFFF;

    public Action<string>? OnSubmit { get; set; }

    private string _text = "";
    private int _caret;
    public string Text => _text;
    public int CaretPos => _caret;

    private readonly List<string> _history = new();
    private int _historyIndex = -1;
    public int HistoryCount => _history.Count;

    public UiChatInput()
    {
        AcceptsFocus = true;
        IsEditControl = true;
        CapturesPointerDrag = true;
    }

    public void InsertChar(char c)
    {
        if (c < 0x20 || c == 0x7F) return;
        if (_text.Length >= MaxCharacters) return;
        _text = _text.Insert(_caret, c.ToString());
        _caret++;
        _historyIndex = -1;
    }

    public void Backspace()
    {
        if (_caret == 0) return;
        _text = _text.Remove(_caret - 1, 1);
        _caret--;
    }

    public void DeleteForward()
    {
        if (_caret >= _text.Length) return;
        _text = _text.Remove(_caret, 1);
    }

    public void MoveCaret(int delta) => _caret = Math.Clamp(_caret + delta, 0, _text.Length);
    public void CaretHome() => _caret = 0;
    public void CaretEnd() => _caret = _text.Length;

    public void Submit()
    {
        var t = _text;
        if (t.Trim().Length == 0) { Clear(); return; }
        OnSubmit?.Invoke(t);
        PushHistory(t);
        Clear();
    }

    private void Clear() { _text = ""; _caret = 0; _historyIndex = -1; }

    private void PushHistory(string t)
    {
        _history.Add(t);
        if (_history.Count > 100) _history.RemoveAt(0);
        _historyIndex = -1;
    }

    public void HistoryPrev()
    {
        if (_history.Count == 0) return;
        _historyIndex = _historyIndex < 0 ? _history.Count - 1 : Math.Max(0, _historyIndex - 1);
        SetTextFromHistory();
    }

    public void HistoryNext()
    {
        if (_historyIndex < 0) return;
        _historyIndex++;
        if (_historyIndex >= _history.Count) { _historyIndex = -1; Clear(); return; }
        SetTextFromHistory();
    }

    private void SetTextFromHistory()
    {
        _text = _history[_historyIndex];
        _caret = _text.Length;
    }

    public float CaretPixelX()
        => DatFont is { } df ? df.MeasureWidth(_text.Substring(0, _caret))
         : Font is { } bf ? bf.MeasureWidth(_text.Substring(0, _caret)) : 0f;

    private bool _focused;

    protected override void OnDraw(UiRenderContext ctx)
    {
        ctx.DrawRect(0, 0, Width, Height, BackgroundColor);
        float lh = DatFont?.LineHeight ?? Font?.LineHeight ?? 14f;
        float ty = (Height - lh) * 0.5f;
        if (DatFont is { } df) ctx.DrawStringDat(df, _text, Padding, ty, TextColor);
        else ctx.DrawString(_text, Padding, ty, TextColor, Font);

        if (_focused)
        {
            float cx = Padding + CaretPixelX();
            ctx.DrawRect(cx, ty, 1f, lh, TextColor);
        }
    }

    public override bool OnEvent(in UiEvent e)
    {
        switch (e.Type)
        {
            case UiEventType.FocusGained: _focused = true; return true;
            case UiEventType.FocusLost: _focused = false; _historyIndex = -1; return true;
            case UiEventType.Char:
                InsertChar((char)e.Data0);
                return true;
            case UiEventType.KeyDown:
            {
                var key = (Silk.NET.Input.Key)e.Data0;
                switch (key)
                {
                    case Silk.NET.Input.Key.Enter:
                    case Silk.NET.Input.Key.KeypadEnter: Submit(); return true;
                    case Silk.NET.Input.Key.Backspace: Backspace(); return true;
                    case Silk.NET.Input.Key.Delete: DeleteForward(); return true;
                    case Silk.NET.Input.Key.Left: MoveCaret(-1); return true;
                    case Silk.NET.Input.Key.Right: MoveCaret(1); return true;
                    case Silk.NET.Input.Key.Home: CaretHome(); return true;
                    case Silk.NET.Input.Key.End: CaretEnd(); return true;
                    case Silk.NET.Input.Key.Up: HistoryPrev(); return true;
                    case Silk.NET.Input.Key.Down: HistoryNext(); return true;
                }
                return false;
            }
        }
        return false;
    }
}