/// Shared Flutter renderer shell for driving the Wolf3D engine from a widget tree.
library;

import 'package:flutter/material.dart';
import 'package:flutter/scheduler.dart';
import 'package:wolf_3d_dart/wolf_3d_engine.dart';

/// Base widget for renderers that present frames from a [WolfEngine].
abstract class BaseWolfRenderer extends StatefulWidget {
  /// Engine instance that owns world state and the shared framebuffer.
  final WolfEngine engine;

  /// Optional key handler invoked by the focused renderer shell.
  final void Function(KeyEvent event)? onKeyEvent;

  /// Creates a renderer bound to [engine].
  const BaseWolfRenderer({
    required this.engine,
    this.onKeyEvent,
    super.key,
  });
}

/// Base [State] implementation that provides a ticker-driven render loop.
abstract class BaseWolfRendererState<T extends BaseWolfRenderer>
    extends State<T>
    with SingleTickerProviderStateMixin {
  /// Per-frame ticker used to advance the engine and request renders.
  late final Ticker gameLoop;

  /// Focus node used by the enclosing [KeyboardListener].
  final FocusNode focusNode = FocusNode();

  Duration _lastTick = Duration.zero;

  @override
  void initState() {
    super.initState();
    gameLoop = createTicker(_tick)..start();
    focusNode.requestFocus();
  }

  void _tick(Duration elapsed) {
    if (!widget.engine.isInitialized) return;

    if (_lastTick == Duration.zero) {
      _lastTick = elapsed;
      return;
    }

    Duration delta = elapsed - _lastTick;
    _lastTick = elapsed;

    widget.engine.tick(delta);

    performRender();
  }

  @override
  void dispose() {
    gameLoop.dispose();
    focusNode.dispose();
    super.dispose();
  }

  /// Renders the latest engine state into the concrete renderer's output type.
  void performRender();

  /// Builds the visible viewport widget for the latest rendered frame.
  Widget buildViewport(BuildContext context);

  /// Background color used by the surrounding scaffold.
  Color get scaffoldColor;

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      backgroundColor: scaffoldColor,
      body: KeyboardListener(
        focusNode: focusNode,
        autofocus: true,
        onKeyEvent: (event) {
          widget.onKeyEvent?.call(event);
        },
        child: Center(
          child: buildViewport(context),
        ),
      ),
    );
  }
}