using System.Collections.Generic;
using System.Numerics;
using AcDream.App.Rendering;
using Silk.NET.Input;
using Silk.NET.OpenGL;

namespace AcDream.App.UI;

/// <summary>
/// Packages the <see cref="UiRoot"/>, the 2D sprite batcher
/// (<see cref="Rendering.TextRenderer"/>), and a default font so
/// <c>GameWindow</c> can wire the retail-style UI in with one
/// construction and a handful of input callbacks.
///
/// Usage (from <c>GameWindow.OnLoad</c>):
/// <code>
///   _uiHost = new UiHost(_gl, shadersDir, _debugFont);
///   _uiHost.Root.WorldMouseFallThrough += (btn, x, y, f) => HandleWorldClick(btn, x, y);
///   _uiHost.Root.WorldKeyFallThrough   += (vk, lp) => HandleHotkey(vk);
///
///   foreach (var mouse in _input.Mice)
///       _uiHost.WireMouse(mouse);
///   foreach (var kb in _input.Keyboards)
///       _uiHost.WireKeyboard(kb);
/// </code>
///
/// And per frame (from <c>GameWindow.OnRender</c>):
/// <code>
///   _uiHost.Tick(deltaSeconds);
///   _uiHost.Draw(new Vector2(_window!.Size.X, _window.Size.Y));
/// </code>
///
/// Retail analog: the trio of <c>DAT_00870340</c> (Core, owns fonts/atlases),
/// <c>DAT_00837ff4</c> (Device, owns input state), <c>DAT_00870c2c</c>
/// (Keystone root, widget tree). We fuse them into a single host class
/// because we're not linking to Keystone.
/// </summary>
public sealed class UiHost : System.IDisposable
{
    public UiRoot Root { get; } = new();
    public RetailWindowManager WindowManager => Root.WindowManager;
    public TextRenderer TextRenderer { get; }
    public BitmapFont? DefaultFont { get; set; }

    /// <summary>The last wired keyboard. Exposed so widgets that need clipboard
    /// access (<see cref="IKeyboard.ClipboardText"/>) or modifier-key state
    /// (<see cref="IKeyboard.IsKeyPressed"/>) — e.g. <see cref="UiText"/>'s
    /// Ctrl+C copy — can reach the device. One-keyboard desktop: last wins.</summary>
    public IKeyboard? Keyboard { get; private set; }

    private long _startTicks = System.Environment.TickCount64;
    private readonly List<System.Action> _inputUnsubscribers = new();
    private bool _disposed;

    public UiHost(GL gl, string shaderDir, BitmapFont? defaultFont = null)
    {
        TextRenderer = new TextRenderer(gl, shaderDir);
        DefaultFont = defaultFont;
    }

    // ── Per-frame ──────────────────────────────────────────────────────

    public void Tick(double deltaSeconds)
    {
        long now = System.Environment.TickCount64 - _startTicks;
        Root.Tick(deltaSeconds, now);
    }

    public void Draw(Vector2 screenSize)
    {
        // Set UiRoot bounds to full screen so HitTestTopDown works.
        Root.Width = screenSize.X;
        Root.Height = screenSize.Y;
        var ctx = new UiRenderContext(TextRenderer, screenSize, DefaultFont);
        TextRenderer.Begin(screenSize);
        Root.Draw(ctx);
        TextRenderer.Flush(DefaultFont);
    }

    // ── Input wiring helpers ───────────────────────────────────────────

    public void WireMouse(IMouse mouse)
    {
        System.ObjectDisposedException.ThrowIf(_disposed, this);
        System.ArgumentNullException.ThrowIfNull(mouse);

        void OnMouseDown(IMouse sender, MouseButton button) =>
            Root.OnMouseDown(MapButton(button), (int)sender.Position.X, (int)sender.Position.Y);
        void OnMouseUp(IMouse sender, MouseButton button) =>
            Root.OnMouseUp(MapButton(button), (int)sender.Position.X, (int)sender.Position.Y);
        void OnMouseMove(IMouse sender, Vector2 position) =>
            Root.OnMouseMove((int)position.X, (int)position.Y);
        void OnScroll(IMouse sender, ScrollWheel scroll) => Root.OnScroll((int)scroll.Y);

        mouse.MouseDown += OnMouseDown;
        mouse.MouseUp += OnMouseUp;
        mouse.MouseMove += OnMouseMove;
        mouse.Scroll += OnScroll;
        _inputUnsubscribers.Add(() =>
        {
            mouse.MouseDown -= OnMouseDown;
            mouse.MouseUp -= OnMouseUp;
            mouse.MouseMove -= OnMouseMove;
            mouse.Scroll -= OnScroll;
        });
    }

    public void WireKeyboard(IKeyboard kb)
    {
        System.ObjectDisposedException.ThrowIf(_disposed, this);
        System.ArgumentNullException.ThrowIfNull(kb);
        Keyboard = kb;   // last wired keyboard wins (one-keyboard desktop)
        void OnKeyDown(IKeyboard sender, Key key, int scanCode) => Root.OnKeyDown((int)key);
        void OnKeyUp(IKeyboard sender, Key key, int scanCode) => Root.OnKeyUp((int)key);
        void OnKeyChar(IKeyboard sender, char value) => Root.OnChar(value);

        kb.KeyDown += OnKeyDown;
        kb.KeyUp += OnKeyUp;
        kb.KeyChar += OnKeyChar;
        _inputUnsubscribers.Add(() =>
        {
            kb.KeyDown -= OnKeyDown;
            kb.KeyUp -= OnKeyUp;
            kb.KeyChar -= OnKeyChar;
        });
    }

    private static UiMouseButton MapButton(MouseButton b) => b switch
    {
        MouseButton.Left   => UiMouseButton.Left,
        MouseButton.Right  => UiMouseButton.Right,
        MouseButton.Middle => UiMouseButton.Middle,
        _                  => UiMouseButton.Left,
    };

    // ── Window manager forwarders (delegate to UiRoot) ─────────────────

    /// <summary>Register a top-level window for Show/Hide/Toggle. See <see cref="UiRoot.RegisterWindow"/>.</summary>
    public RetailWindowHandle RegisterWindow(
        string name,
        UiElement window,
        UiElement? contentRoot = null,
        IRetainedPanelController? controller = null,
        IRetainedWindowStateController? stateController = null)
        => Root.RegisterWindow(name, window, contentRoot, controller, stateController);

    public bool UnregisterWindow(string name) => Root.UnregisterWindow(name);

    /// <summary>Show a registered window; returns false if the name is unknown.</summary>
    public bool ShowWindow(string name) => Root.ShowWindow(name);

    /// <summary>Hide a registered window; returns false if the name is unknown.</summary>
    public bool HideWindow(string name) => Root.HideWindow(name);

    public bool CloseWindow(string name) => Root.CloseWindow(name);

    /// <summary>Return the current visibility of a registered window.</summary>
    public bool IsWindowVisible(string name) => Root.IsWindowVisible(name);

    /// <summary>Toggle a registered window's visibility; returns the new IsVisible.</summary>
    public bool ToggleWindow(string name) => Root.ToggleWindow(name);

    public void Dispose()
    {
        if (_disposed) return;
        _disposed = true;
        for (int i = _inputUnsubscribers.Count - 1; i >= 0; i--)
            _inputUnsubscribers[i]();
        _inputUnsubscribers.Clear();
        Keyboard = null;
        WindowManager.Dispose();
        TextRenderer.Dispose();
    }
}