using System.Text;
using TinyTUI.Input;
using TinyTUI.Rendering;
using TinyTUI.Text;
using TinyTUI.Theme;

namespace TinyTUI.Components;

/// <summary>
/// 支持文本输入 提交和取消的单行输入组件
/// </summary>
public sealed class Input(
    ITextMeasurer? textMeasurer = null,
    KeybindingRegistry? keybindings = null,
    ITuiTheme? theme = null) : IInputComponent, IFocusableComponent, IKeybindingComponent
{
    private readonly ITextMeasurer _textMeasurer = textMeasurer ?? new TerminalTextMeasurer();
    private readonly ITuiTheme _theme = theme ?? TuiTheme.Default;
    private KeybindingRegistry _keybindings = keybindings ?? KeybindingRegistry.CreateDefault();

    /// <summary>
    /// 获取或设置输入框前缀
    /// </summary>
    public string Prompt { get; set; } = "> ";

    /// <summary>
    /// 获取当前输入值
    /// </summary>
    public string Value { get; private set; } = string.Empty;

    /// <inheritdoc />
    public bool Focused { get; set; }

    /// <summary>
    /// 在输入值变化时触发
    /// </summary>
    public Action<string>? OnChanged { get; set; }

    /// <summary>
    /// 在用户提交输入时触发
    /// </summary>
    public Action<string>? OnSubmitted { get; set; }

    /// <summary>
    /// 在用户取消输入时触发
    /// </summary>
    public Action? OnCanceled { get; set; }

    /// <inheritdoc />
    public IReadOnlyList<string> Render(int width)
    {
        // 只有运行时确认获得焦点后才发出 marker 避免多个输入组件争抢硬件光标
        var marker = Focused ? CursorMarker.Marker : string.Empty;
        var cursor = Focused ? _theme.InputCursor(" ") : string.Empty;
        var visible = $"{Prompt}{Value}{marker}{cursor}";
        return [_textMeasurer.Truncate(visible, width)];
    }

    /// <inheritdoc />
    public void SetKeybindings(KeybindingRegistry keybindings)
        => _keybindings = keybindings ?? throw new ArgumentNullException(nameof(keybindings));

    /// <inheritdoc />
    public void HandleInput(TuiInputEvent input)
    {
        switch (input)
        {
            case { Kind: TuiInputEventKind.Text }:
                SetValue(Value + input.Value);
                break;
            case { Kind: TuiInputEventKind.Paste }:
                SetValue(Value + input.Value.Replace("\r\n", "\n").Replace('\n', ' '));
                break;
            case { Kind: TuiInputEventKind.Key }:
                HandleKey(input);
                break;
        }
    }

    /// <summary>
    /// 清空当前输入值
    /// </summary>
    public void Clear() => SetValue(string.Empty);

    /// <summary>
    /// 根据动作映射处理单行输入快捷键
    /// </summary>
    private void HandleKey(TuiInputEvent input)
    {
        if (_keybindings.Matches(input, TuiKeybindings.EditorDeleteCharBackward))
        {
            Backspace();
            return;
        }

        if (_keybindings.Matches(input, TuiKeybindings.InputSubmit))
        {
            OnSubmitted?.Invoke(Value);
            return;
        }

        if (_keybindings.Matches(input, TuiKeybindings.InputCancel))
            OnCanceled?.Invoke();
    }

    private void SetValue(string value)
    {
        Value = value;
        OnChanged?.Invoke(Value);
    }

    /// <summary>
    /// 删除最后一个 Unicode Rune
    /// </summary>
    private void Backspace()
    {
        if (Value.Length == 0)
            return;

        var builder = new StringBuilder();
        var runes = Value.EnumerateRunes().ToArray();

        // 用 Rune 删除避免把 emoji 或代理对拆坏
        foreach (var rune in runes[..^1]) builder.Append(rune);

        SetValue(builder.ToString());
    }
}