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

/// A minute-of-day picker: a 15-minute dropdown plus a "Custom…" escape.
library;

import 'dart:async';

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

/// The dropdown value standing for "Custom…". Negative, so it can never
/// collide with a real minute of day (`0..1439`).
const int _customValue = -1;

/// Picks a minute of day, offering the 15-minute grid within
/// [minMinute]..[maxMinute] and a "Custom…" item that opens a time picker
/// for any minute in that range.
///
/// The grid is what most people want and keeps the list short; "Custom…"
/// exists because an endpoint may legitimately sit off the grid (07:23 to
/// match a train), and because the PC can set such a value and sync it here.
/// That second case is why the current [value] is always offered as an item
/// even when it is off-grid or outside the range: a [DropdownButton] whose
/// value matches no item asserts, which would take the settings screen down
/// over a value another device wrote.
class MealTimeDropdown extends StatelessWidget {
  /// Creates a [MealTimeDropdown].
  const MealTimeDropdown({
    required this.label,
    required this.value,
    required this.minMinute,
    required this.maxMinute,
    required this.onChanged,
    this.gridMaxMinute,
    super.key,
  });

  /// The field label, e.g. "First meal".
  final String label;

  /// The current minute of day.
  final int value;

  /// Earliest minute offered (inclusive).
  final int minMinute;

  /// Latest minute offered (inclusive), through "Custom…" if not the grid.
  final int maxMinute;

  /// Latest grid mark listed, when it must stop short of [maxMinute] (the
  /// first meal's grid ends at 23:30 so a grid-aligned last meal still fits,
  /// while "Custom…" may go to 23:44). Defaults to [maxMinute].
  final int? gridMaxMinute;

  /// Called with the chosen minute, already clamped into
  /// [minMinute]..[maxMinute]. Not called when the picker is dismissed.
  final ValueChanged<int> onChanged;

  /// The minutes listed, ascending: the grid marks in range plus [value].
  List<int> get options {
    final first =
        (minMinute + kSlotGridMinutes - 1) ~/
        kSlotGridMinutes *
        kSlotGridMinutes;
    return {
      for (
        var m = first;
        m <= (gridMaxMinute ?? maxMinute);
        m += kSlotGridMinutes
      )
        m,
      value,
    }.toList()..sort();
  }

  int _clampToRange(int minute) => minute < minMinute
      ? minMinute
      : (minute > maxMinute ? maxMinute : minute);

  Future<void> _pickCustom(BuildContext context) async {
    final picked = await showTimePicker(
      context: context,
      initialTime: TimeOfDay(hour: value ~/ 60, minute: value % 60),
      helpText: label,
      // The rest of the app writes times as HH:MM; an AM/PM dial here would
      // be the one place that reads differently.
      builder: (context, child) => MediaQuery(
        data: MediaQuery.of(context).copyWith(alwaysUse24HourFormat: true),
        child: child!,
      ),
    );
    if (picked == null) return;
    // Clamped rather than rejected: the picker cannot be told the range, and
    // the nearest legal minute is what `MealSchedule.normalized` would
    // produce anyway -- doing it here keeps the dropdown's own contract.
    onChanged(_clampToRange(picked.hour * 60 + picked.minute));
  }

  @override
  Widget build(BuildContext context) => ConstrainedBox(
    constraints: const BoxConstraints(maxWidth: AppWidth.field),
    child: InputDecorator(
      decoration: InputDecoration(labelText: label),
      child: DropdownButtonHideUnderline(
        child: DropdownButton<int>(
          value: value,
          isDense: true,
          isExpanded: true,
          // "Custom…" first: at the end it sat ~95 grid items down.
          items: [
            const DropdownMenuItem(value: _customValue, child: Text('Custom…')),
            for (final minute in options)
              DropdownMenuItem(value: minute, child: Text(slotLabel(minute))),
          ],
          onChanged: (minute) {
            if (minute == null) return;
            if (minute == _customValue) {
              unawaited(_pickCustom(context));
            } else {
              onChanged(minute);
            }
          },
        ),
      ),
    ),
  );
}