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 TextRenderer TextRenderer { get; }
    public BitmapFont? DefaultFont { get; set; }
    private long _startTicks = System.Environment.TickCount64;

    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)
    {
        mouse.MouseDown += (_, b) =>
            Root.OnMouseDown(MapButton(b), (int)mouse.Position.X, (int)mouse.Position.Y);
        mouse.MouseUp += (_, b) =>
            Root.OnMouseUp(MapButton(b), (int)mouse.Position.X, (int)mouse.Position.Y);
        mouse.MouseMove += (_, p) =>
            Root.OnMouseMove((int)p.X, (int)p.Y);
        mouse.Scroll += (_, s) =>
            Root.OnScroll((int)s.Y);
    }

    public void WireKeyboard(IKeyboard kb)
    {
        kb.KeyDown += (_, k, _) => Root.OnKeyDown((int)k);
        kb.KeyUp   += (_, k, _) => Root.OnKeyUp((int)k);
        kb.KeyChar += (_, c) => Root.OnChar(c);
    }

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

    public void Dispose()
    {
        TextRenderer.Dispose();
    }
}