diet-guard/app/lib/widgets/day_status_calendar.dart

/// Monthly calendar colored by daily budget-adherence status.
library;

import 'package:diet_guard_app/models/day_status.dart';
import 'package:diet_guard_app/ui/theme.dart';
import 'package:flutter/material.dart';

/// Monthly calendar widget that colors each day by its [DayStatus].
///
/// Mirrors the diet_guard gate's calendar tab (`_gatelock_calendar.py` /
/// `_calendar_view.py`): not-logged renders as a black cell with a visible
/// outline (so it doesn't vanish into the dark background); a day after
/// [today] -- nothing has happened yet to judge -- renders neutrally,
/// never as a false "not logged" black cell.
class DayStatusCalendar extends StatelessWidget {
  /// Creates a [DayStatusCalendar].
  const DayStatusCalendar({
    required this.statusByDate,
    required this.month,
    required this.today,
    required this.onPrevMonth,
    required this.onNextMonth,
    this.onDaySelected,
    super.key,
  });

  /// Per-day status, keyed `YYYY-MM-DD`. A past-or-today date absent from
  /// this map is treated as [DayStatus.notLogged].
  final Map<String, DayStatus> statusByDate;

  /// Only the year and month of this DateTime are used.
  final DateTime month;

  /// The reference "today"; days after this render neutrally.
  final DateTime today;

  /// Called when the user taps the previous-month chevron.
  final VoidCallback onPrevMonth;

  /// Called when the user taps the next-month chevron.
  final VoidCallback onNextMonth;

  /// Called with a day's date when the user taps that day's cell.
  ///
  /// Null disables tapping (cells render but do not respond). A cell
  /// outside the displayed month is never tappable regardless.
  final void Function(DateTime day)? onDaySelected;

  static const _weekHeaders = ['Mo', 'Tu', 'We', 'Th', 'Fr', 'Sa', 'Su'];

  static const _monthNames = [
    'January',
    'February',
    'March',
    'April',
    'May',
    'June',
    'July',
    'August',
    'September',
    'October',
    'November',
    'December',
  ];

  String _dateKey(int year, int m, int day) =>
      '$year-${m.toString().padLeft(2, '0')}-${day.toString().padLeft(2, '0')}';

  /// Returns the status to render for [year]/[m]/[day], or null for a
  /// future day (nothing to judge yet).
  DayStatus? _statusFor(int year, int m, int day) {
    final date = DateTime(year, m, day);
    final todayOnly = DateTime(today.year, today.month, today.day);
    if (date.isAfter(todayOnly)) return null;
    return statusByDate[_dateKey(year, m, day)] ?? DayStatus.notLogged;
  }

  Color _cellColor(
    DayStatus? status,
    ColorScheme scheme,
    AppStatusColors statusColors,
  ) => switch (status) {
    // Future day: nothing to judge yet, so it reads as part of the
    // panel rather than an empty/failed slot.
    null => scheme.surfaceContainerHigh,
    // Recessed below the panel (darker than the surrounding
    // ink-raised-1 container) with a visible outline, so it reads as
    // "empty" without vanishing into the background.
    DayStatus.notLogged => scheme.surface,
    DayStatus.red => scheme.error,
    DayStatus.yellow => statusColors.warning,
    DayStatus.green => statusColors.success,
  };

  Color _textColor(DayStatus? status, ColorScheme scheme) => switch (status) {
    null => scheme.onSurfaceVariant,
    DayStatus.notLogged => scheme.onSurface,
    // Status colors sit at mid brightness, so the near-black `ink` role
    // (not a separate pure black) gives strong, on-palette contrast.
    DayStatus.red || DayStatus.yellow || DayStatus.green => scheme.surface,
  };

  @override
  Widget build(BuildContext context) {
    final scheme = Theme.of(context).colorScheme;
    // A `!` here would crash in any context that doesn't build its theme
    // from buildAppTheme() -- most widget tests just wrap in a bare
    // MaterialApp(home: ...). Falling back to the app's own dark instance
    // matches production exactly when the extension is genuinely absent.
    final statusColors =
        Theme.of(context).extension<AppStatusColors>() ?? AppStatusColors.dark;
    final year = month.year;
    final m = month.month;
    final daysInMonth = DateTime(year, m + 1, 0).day;
    // weekday: 1=Mon..7=Sun -> offset 0..6
    final firstWeekday = DateTime(year, m).weekday - 1;
    final totalCells = firstWeekday + daysInMonth;
    final rows = (totalCells / 7).ceil();

    return Container(
      padding: const EdgeInsets.all(AppSpacing.md),
      decoration: BoxDecoration(
        color: scheme.surfaceContainerHigh,
        borderRadius: BorderRadius.circular(AppRadius.md),
      ),
      child: Column(
        children: [
          Row(
            mainAxisAlignment: MainAxisAlignment.spaceBetween,
            children: [
              IconButton(
                icon: Icon(Icons.chevron_left, color: scheme.onSurfaceVariant),
                visualDensity: VisualDensity.compact,
                padding: EdgeInsets.zero,
                onPressed: onPrevMonth,
              ),
              Text(
                '${_monthNames[m - 1]} $year',
                style: TextStyle(
                  color: scheme.onSurface,
                  fontWeight: FontWeight.bold,
                  fontSize: AppTextSize.body,
                ),
              ),
              IconButton(
                icon: Icon(Icons.chevron_right, color: scheme.onSurfaceVariant),
                visualDensity: VisualDensity.compact,
                padding: EdgeInsets.zero,
                onPressed: onNextMonth,
              ),
            ],
          ),
          const SizedBox(height: AppSpacing.xs + 2),
          Row(
            mainAxisAlignment: MainAxisAlignment.spaceAround,
            children: _weekHeaders
                .map(
                  (h) => SizedBox(
                    width: 30,
                    child: Text(
                      h,
                      textAlign: TextAlign.center,
                      // Two-letter day abbreviations are UI chrome (like a
                      // badge/tag), deliberately kept below the 16px body
                      // floor rather than forced to grow past their slot.
                      style: TextStyle(
                        color: scheme.onSurfaceVariant,
                        fontSize: AppTextSize.label - 2,
                        fontWeight: FontWeight.bold,
                      ),
                    ),
                  ),
                )
                .toList(),
          ),
          const SizedBox(height: AppSpacing.xs),
          ...List.generate(rows, (row) {
            return Row(
              mainAxisAlignment: MainAxisAlignment.spaceAround,
              children: List.generate(7, (col) {
                final cell = row * 7 + col;
                final day = cell - firstWeekday + 1;
                if (day < 1 || day > daysInMonth) {
                  return const SizedBox(width: 30, height: 30);
                }
                final status = _statusFor(year, m, day);
                final cellWidget = Container(
                  width: 30,
                  height: 30,
                  margin: const EdgeInsets.symmetric(vertical: 2),
                  decoration: BoxDecoration(
                    shape: BoxShape.circle,
                    color: _cellColor(status, scheme, statusColors),
                    border: status == DayStatus.notLogged
                        ? Border.all(color: scheme.outline)
                        : null,
                  ),
                  alignment: Alignment.center,
                  child: Text(
                    '$day',
                    // A fixed 30px circle can't fit 16px bold digits for
                    // two-digit days without overflowing — kept as a
                    // deliberate chrome exception (rule 4), not accidental.
                    style: TextStyle(
                      color: _textColor(status, scheme),
                      fontSize: AppTextSize.label - 2,
                      fontWeight:
                          status != null && status != DayStatus.notLogged
                          ? FontWeight.bold
                          : FontWeight.normal,
                    ),
                  ),
                );
                if (onDaySelected == null) return cellWidget;
                // InkWell, not a bare GestureDetector: tapping a day navigates
                // to the date-filtered history, and a GestureDetector is not
                // focusable, so that navigation had no keyboard route at all
                // and no semantics for a screen reader. InkWell is a focus
                // stop and is activated by Enter/Space.
                final date = DateTime(year, m, day);
                return Semantics(
                  button: true,
                  label: 'View $day/$m/$year',
                  child: InkWell(
                    onTap: () => onDaySelected!(date),
                    customBorder: const CircleBorder(),
                    child: cellWidget,
                  ),
                );
              }),
            );
          }),
        ],
      ),
    );
  }
}