import 'package:flutter/material.dart';
import 'package:professional_repository/professional_repository.dart';
import 'package:prosappco/utils/time_of_day_extension.dart';
import 'package:prosappco/utils/time_of_day_utils.dart';

/// Minimum notice a patient has to give before an appointment.
///
/// It used to live only in the patient's calendar, so the professional's own
/// agenda generated a different list: at 15:00 a professional working
/// 08:00-18:00 with hourly slots saw "3 libres" (15:00, 16:00, 17:00) while
/// the patient could only book 18:00. Both screens now go through
/// [SlotGenerator], so the two lists always agree.
const Duration kBookingLeadTime = Duration(hours: 3);

/// The single source of truth for "which times exist on this day".
class SlotGenerator {
  const SlotGenerator._();

  /// Times offered on [day] for [schedule].
  ///
  /// [notBefore] drops the slots that are already in the past (or inside the
  /// lead time). Pass it as `DateTime.now().add(kBookingLeadTime)` for the
  /// patient flow and `DateTime.now()` for the professional's own agenda,
  /// where the professional may still block the next hour.
  static List<TimeOfDay> forDay({
    required ScheduleEntity? schedule,
    required DateTime day,
    required int slotDurationMinutes,
    DateTime? notBefore,
  }) {
    final raw = _rawSlots(schedule, slotDurationMinutes);
    if (notBefore == null) return raw;
    return raw.where((t) {
      final at = DateTime(day.year, day.month, day.day, t.hour, t.minute);
      return !at.isBefore(notBefore);
    }).toList();
  }

  /// Where a slot starting at [start] ends.
  ///
  /// Clamped to 23:59: a 120-minute slot starting at 23:00 used to produce
  /// "25:00", which is not a real time and the backend stored verbatim.
  static TimeOfDay endOf(TimeOfDay start, int slotDurationMinutes) {
    final total = start.hour * 60 + start.minute + slotDurationMinutes;
    if (total >= 24 * 60) return const TimeOfDay(hour: 23, minute: 59);
    return TimeOfDay(hour: total ~/ 60, minute: total % 60);
  }

  static List<TimeOfDay> _rawSlots(ScheduleEntity? s, int stepMinutes) {
    if (s == null || !s.enabled) return [];
    if (s.continuousDay) {
      if (s.range1Hour1 == null || s.range2Hour2 == null) return [];
      if (s.range1Hour1!.compareTo(s.range2Hour2!) >= 0) return [];
      return TimeOfDayUtils.genRanges(s.range1Hour1!, s.range2Hour2!,
          stepMinutes: stepMinutes);
    }
    if (s.range1Hour1 == null ||
        s.range1Hour2 == null ||
        s.range2Hour1 == null ||
        s.range2Hour2 == null) {
      return [];
    }
    if (s.range1Hour1!.compareTo(s.range1Hour2!) >= 0 ||
        s.range2Hour1!.compareTo(s.range2Hour2!) >= 0) {
      return [];
    }
    return [
      ...TimeOfDayUtils.genRanges(s.range1Hour1!, s.range1Hour2!,
          stepMinutes: stepMinutes),
      ...TimeOfDayUtils.genRanges(s.range2Hour1!, s.range2Hour2!,
          stepMinutes: stepMinutes),
    ];
  }
}