import 'package:flutter/material.dart';
import 'package:syncfusion_flutter_calendar/calendar.dart';

import '../data/arbitrary_appointment.dart';
import '../data/calendar_layout.dart';
import 'cross_painter.dart';

class AppointmentTile extends StatelessWidget {
  static const _radius = BorderRadius.all(Radius.circular(7));

  final Appointment appointment;
  final bool crossedOut;

  const AppointmentTile({super.key, required this.appointment, this.crossedOut = false});

  @override
  Widget build(BuildContext context) {
    final isPast = appointment.endTime.isBefore(DateTime.now());
    final color = appointment.color.withAlpha(isPast ? 160 : 255);
    final isCustom = appointment.id is CustomAppointment;
    final description = appointment.location ?? '';

    return Padding(
      padding: const EdgeInsets.all(1),
      child: Stack(
        children: [
          Positioned.fill(
            child: Container(
              padding: const EdgeInsets.symmetric(horizontal: 4, vertical: 2),
              alignment: Alignment.topLeft,
              decoration: BoxDecoration(
                shape: BoxShape.rectangle,
                borderRadius: _radius,
                color: color,
              ),
              child: Column(
                crossAxisAlignment: CrossAxisAlignment.stretch,
                mainAxisSize: MainAxisSize.max,
                children: [
                  _AdaptiveTitle(
                    text: appointment.subject,
                    fontSize: kAppointmentTitleFontSize,
                    minFontSize: kAppointmentTitleMinFontSize,
                    fontWeight: FontWeight.w500,
                  ),
                  if (isCustom) ...[
                    if (description.isNotEmpty)
                      Expanded(
                        child: Padding(
                          padding: const EdgeInsets.only(top: 1),
                          child: _WrappingBody(
                            text: description,
                            fontSize: kAppointmentBodyFontSize,
                            lineHeight: kAppointmentBodyLineHeight,
                          ),
                        ),
                      ),
                  ] else ...[
                    for (final line in description
                        .split('\n')
                        .where((p) => p.isNotEmpty)
                        .take(2))
                      _ScaledLine(text: line, fontSize: kAppointmentBodyFontSize),
                  ],
                ],
              ),
            ),
          ),
          if (crossedOut)
            Positioned.fill(
              child: ClipRRect(
                borderRadius: _radius,
                child: DecoratedBox(
                  decoration: BoxDecoration(
                    border: Border.all(width: 2, color: Colors.red.withAlpha(200)),
                    borderRadius: _radius,
                  ),
                  child: CustomPaint(painter: CrossPainter()),
                ),
              ),
            ),
        ],
      ),
    );
  }
}

/// Renders the appointment title. Scales down to fit the available width via
/// [FittedBox], but never below [minFontSize] — when even the minimum size
/// overflows, the text is rendered at [minFontSize] with an ellipsis.
class _AdaptiveTitle extends StatelessWidget {
  final String text;
  final double fontSize;
  final double minFontSize;
  final FontWeight? fontWeight;

  const _AdaptiveTitle({
    required this.text,
    required this.fontSize,
    required this.minFontSize,
    this.fontWeight,
  });

  @override
  Widget build(BuildContext context) {
    final baseStyle = TextStyle(
      color: Colors.white,
      fontSize: fontSize,
      fontWeight: fontWeight,
      height: 1.1,
    );
    final textScaler = MediaQuery.textScalerOf(context);
    return LayoutBuilder(
      builder: (context, constraints) {
        // Probe at the minimum size: if even that overflows, we have to ellipsize.
        final probe = TextPainter(
          text: TextSpan(text: text, style: baseStyle.copyWith(fontSize: minFontSize)),
          textDirection: TextDirection.ltr,
          maxLines: 1,
          textScaler: textScaler,
        )..layout();
        if (probe.width > constraints.maxWidth) {
          return Text(
            text,
            style: baseStyle.copyWith(fontSize: minFontSize),
            maxLines: 1,
            softWrap: false,
            overflow: TextOverflow.ellipsis,
          );
        }
        return FittedBox(
          fit: BoxFit.scaleDown,
          alignment: Alignment.centerLeft,
          child: Text(
            text,
            style: baseStyle,
            maxLines: 1,
            softWrap: false,
          ),
        );
      },
    );
  }
}

/// Body text for custom events. Wraps to fill the available height and clips
/// trailing content with an ellipsis if there is more than fits.
class _WrappingBody extends StatelessWidget {
  final String text;
  final double fontSize;
  final double lineHeight;

  const _WrappingBody({
    required this.text,
    required this.fontSize,
    required this.lineHeight,
  });

  @override
  Widget build(BuildContext context) {
    final style = TextStyle(
      color: Colors.white,
      fontSize: fontSize,
      height: lineHeight,
    );
    final textScaler = MediaQuery.textScalerOf(context);
    return LayoutBuilder(
      builder: (context, constraints) {
        final lineBox = textScaler.scale(fontSize) * lineHeight;
        final maxLines = (constraints.maxHeight / lineBox).floor().clamp(1, 99);
        return Text(
          text,
          style: style,
          maxLines: maxLines,
          overflow: TextOverflow.ellipsis,
          softWrap: true,
        );
      },
    );
  }
}

/// One row of appointment text. The FittedBox scales **only this line** down
/// when the text is wider than the tile, so a long teacher name does not
/// shrink the room number above it.
class _ScaledLine extends StatelessWidget {
  final String text;
  final double fontSize;

  const _ScaledLine({
    required this.text,
    required this.fontSize,
  });

  @override
  Widget build(BuildContext context) => FittedBox(
        fit: BoxFit.scaleDown,
        alignment: Alignment.centerLeft,
        child: Text(
          text,
          style: TextStyle(
            color: Colors.white,
            fontSize: fontSize,
            height: 1.1,
          ),
          maxLines: 1,
          softWrap: false,
        ),
      );
}