/// UI-03: the expanding-ring-plus-glow-dot user-location marker from the Plan/Route
/// Planning exports. Values (sizes, colours, the scale/opacity curve) are lifted from
/// the exports' own `pulse-ring` keyframes, not guessed -- see
/// `docs/design/stitch-export/screens/route-planning-dark.html`.
library;

import 'package:flutter/material.dart';

class PulsingLocationMarker extends StatefulWidget {
  const PulsingLocationMarker({super.key});

  @override
  State<PulsingLocationMarker> createState() => _PulsingLocationMarkerState();
}

class _PulsingLocationMarkerState extends State<PulsingLocationMarker>
    with SingleTickerProviderStateMixin {
  late final _controller = AnimationController(
    vsync: this,
    duration: const Duration(seconds: 2),
  );

  @override
  void didChangeDependencies() {
    super.didChangeDependencies();
    _syncWithReducedMotion();
  }

  /// A static dot -- the ring never expands -- when the platform has reduced motion
  /// enabled, the same accessibility setting `prefers-reduced-motion` maps to on the
  /// web this component's design came from.
  void _syncWithReducedMotion() {
    final reduceMotion = MediaQuery.maybeOf(context)?.disableAnimations ?? false;
    if (reduceMotion) {
      _controller.stop();
    } else if (!_controller.isAnimating) {
      _controller.repeat();
    }
  }

  @override
  void dispose() {
    _controller.dispose();
    super.dispose();
  }

  @override
  Widget build(BuildContext context) {
    final colors = Theme.of(context).colorScheme;
    return SizedBox(
      width: 40,
      height: 40,
      child: AnimatedBuilder(
        animation: _controller,
        builder: (context, child) {
          // The keyframes' own 0%/70%/100% easing: scale 0.8 -> 1.0 and opacity
          // 0.8 -> 0, both eased out rather than linear, so the ring visibly slows as
          // it fades rather than looking like it's cut off mid-motion.
          final t = Curves.easeOut.transform(_controller.value);
          final scale = 0.8 + (0.2 * t);
          final opacity = 0.8 * (1 - t);
          return Stack(
            alignment: Alignment.center,
            children: [
              // The faint, static outer ring -- always present, pulse or no pulse.
              Container(
                width: 16,
                height: 16,
                decoration: BoxDecoration(
                  color: colors.primary.withValues(alpha: 0.3),
                  shape: BoxShape.circle,
                ),
              ),
              Transform.scale(
                scale: scale,
                child: Opacity(
                  opacity: opacity,
                  child: Container(
                    width: 12,
                    height: 12,
                    decoration: BoxDecoration(
                      color: colors.primary,
                      shape: BoxShape.circle,
                    ),
                  ),
                ),
              ),
              Container(
                width: 8,
                height: 8,
                decoration: BoxDecoration(
                  color: colors.primary,
                  shape: BoxShape.circle,
                  boxShadow: [
                    BoxShadow(
                      color: colors.primary.withValues(alpha: 0.5),
                      blurRadius: 10,
                      spreadRadius: 1,
                    ),
                  ],
                ),
              ),
            ],
          );
        },
      ),
    );
  }
}