import 'package:flutter/material.dart';

import '../theme/m3_motion.dart';

/// Standardized M3 Expressive page header with animated entrance.
///
/// Replaces the ad-hoc `Padding(Align(Text(...)))` pattern found across
/// screens. Provides:
/// * `headlineSmall` typography — correct M3 size for a top-level page title.
/// * [M3FadeSlideIn] entrance animation — 400 ms with emphasized easing.
/// * Optional [subtitle] in `bodyMedium` / `onSurfaceVariant`.
/// * Optional [actions] row rendered at the trailing end.
/// * Responsive alignment: left-aligned on desktop (≥600 dp), centered on
///   mobile to match the existing navigation-bar-centric layout.
class AppPageHeader extends StatelessWidget {
  const AppPageHeader({
    super.key,
    required this.title,
    this.subtitle,
    this.actions,
    this.padding = const EdgeInsets.only(top: 20, bottom: 12),
  });

  final String title;
  final String? subtitle;

  /// Optional trailing action widgets (e.g. filter chip, icon button).
  final List<Widget>? actions;

  /// Vertical padding around the header. Horizontal padding is handled by
  /// the parent [ResponsiveBody] so only top/bottom should be set here.
  final EdgeInsetsGeometry padding;

  @override
  Widget build(BuildContext context) {
    final tt = Theme.of(context).textTheme;
    final cs = Theme.of(context).colorScheme;

    final titleWidget = Text(
      title,
      style: tt.headlineSmall?.copyWith(
        fontWeight: FontWeight.w700,
        letterSpacing: -0.3,
        color: cs.onSurface,
      ),
      textAlign: TextAlign.center,
    );

    final subtitleWidget = subtitle == null
        ? null
        : Text(
            subtitle!,
            style: tt.bodyMedium?.copyWith(color: cs.onSurfaceVariant),
            textAlign: TextAlign.center,
          );

    final hasActions = actions != null && actions!.isNotEmpty;

    Widget content;
    if (!hasActions) {
      content = Column(
        crossAxisAlignment: CrossAxisAlignment.center,
        mainAxisSize: MainAxisSize.min,
        children: [
          titleWidget,
          if (subtitleWidget != null) ...[
            const SizedBox(height: 4),
            subtitleWidget,
          ],
        ],
      );
    } else {
      // With actions — centered title/subtitle, actions sit to the right.
      content = Row(
        crossAxisAlignment: CrossAxisAlignment.center,
        children: [
          Expanded(
            child: Column(
              crossAxisAlignment: CrossAxisAlignment.center,
              mainAxisSize: MainAxisSize.min,
              children: [
                titleWidget,
                if (subtitleWidget != null) ...[
                  const SizedBox(height: 4),
                  subtitleWidget,
                ],
              ],
            ),
          ),
          const SizedBox(width: 8),
          Row(mainAxisSize: MainAxisSize.min, children: actions!),
        ],
      );
    }

    return M3FadeSlideIn(
      duration: M3Motion.standard,
      child: Padding(padding: padding, child: content),
    );
  }
}