/**
 * Cron utilities
 * Parse schedules and estimate next run times
 */
import type { CronSchedule } from '@lib/cron-types';

export type ScheduleType = 'daily' | 'weekly' | 'monthly' | 'interval' | 'custom';

export interface SchedulePreset {
  key: string;
  value: string;
  type: ScheduleType;
}

export const schedulePresets: SchedulePreset[] = [
  { key: 'everyMinute', value: '* * * * *', type: 'interval' },
  { key: 'every5Min', value: '*/5 * * * *', type: 'interval' },
  { key: 'every15Min', value: '*/15 * * * *', type: 'interval' },
  { key: 'everyHour', value: '0 * * * *', type: 'interval' },
  { key: 'daily9am', value: '0 9 * * *', type: 'daily' },
  { key: 'daily6pm', value: '0 18 * * *', type: 'daily' },
  { key: 'weeklyMon', value: '0 9 * * 1', type: 'weekly' },
  { key: 'monthly1st', value: '0 9 1 * *', type: 'monthly' },
];

// Parse cron schedule to human-readable format
// Handles both plain cron strings and Gateway CronSchedule objects
export function parseCronSchedule(
  schedule: unknown,
  t: (key: string, interpolations?: Record<string, unknown>) => string,
): string {
  if (schedule && typeof schedule === 'object') {
    const s = schedule as { kind?: string; expr?: string; tz?: string; everyMs?: number; at?: string };
    if (s.kind === 'cron' && typeof s.expr === 'string') {
      return parseCronExpr(s.expr, t);
    }
    if (s.kind === 'every' && typeof s.everyMs === 'number') {
      const ms = s.everyMs;
      if (ms < 60_000) return t('cron.schedule.everySeconds', { count: Math.round(ms / 1000) });
      if (ms < 3_600_000) return t('cron.schedule.everyMinutes', { count: Math.round(ms / 60_000) });
      if (ms < 86_400_000) return t('cron.schedule.everyHours', { count: Math.round(ms / 3_600_000) });
      return t('cron.schedule.everyDays', { count: Math.round(ms / 86_400_000) });
    }
    if (s.kind === 'at' && typeof s.at === 'string') {
      try {
        return t('cron.schedule.onceAt', { time: new Date(s.at).toLocaleString() });
      } catch {
        return t('cron.schedule.onceAt', { time: s.at });
      }
    }
    return String(schedule);
  }

  if (typeof schedule === 'string') {
    return parseCronExpr(schedule, t);
  }

  return String(schedule ?? t('cron.schedule.unknown'));
}

export function parseCronExpr(
  cron: string,
  t: (key: string, interpolations?: Record<string, unknown>) => string,
): string {
  const preset = schedulePresets.find((p) => p.value === cron);
  if (preset) return t(`cron.presets.${preset.key}` as const);

  const parts = cron.split(' ');
  if (parts.length !== 5) return cron;

  const [minute, hour, dayOfMonth, , dayOfWeek] = parts;

  if (minute === '*' && hour === '*') return t('cron.presets.everyMinute');
  if (minute.startsWith('*/')) return t('cron.schedule.everyMinutes', { count: Number(minute.slice(2)) });
  if (hour === '*' && minute === '0') return t('cron.presets.everyHour');
  if (dayOfWeek !== '*' && dayOfMonth === '*') {
    return t('cron.schedule.weeklyAt', { day: dayOfWeek, time: `${hour}:${minute.padStart(2, '0')}` });
  }
  if (dayOfMonth !== '*') {
    return t('cron.schedule.monthlyAtDay', { day: dayOfMonth, time: `${hour}:${minute.padStart(2, '0')}` });
  }
  if (hour !== '*') {
    return t('cron.schedule.dailyAt', { time: `${hour}:${minute.padStart(2, '0')}` });
  }

  return cron;
}

export function estimateNextRun(scheduleExpr: string): string | null {
  const now = new Date();
  const next = new Date(now.getTime());

  if (scheduleExpr === '* * * * *') {
    next.setSeconds(0, 0);
    next.setMinutes(next.getMinutes() + 1);
    return formatLocaleDateTime(next);
  }

  if (scheduleExpr === '*/5 * * * *') {
    const delta = 5 - (next.getMinutes() % 5 || 5);
    next.setSeconds(0, 0);
    next.setMinutes(next.getMinutes() + delta);
    return formatLocaleDateTime(next);
  }

  if (scheduleExpr === '*/15 * * * *') {
    const delta = 15 - (next.getMinutes() % 15 || 15);
    next.setSeconds(0, 0);
    next.setMinutes(next.getMinutes() + delta);
    return formatLocaleDateTime(next);
  }

  if (scheduleExpr === '0 * * * *') {
    next.setMinutes(0, 0, 0);
    next.setHours(next.getHours() + 1);
    return formatLocaleDateTime(next);
  }

  if (scheduleExpr === '0 9 * * *' || scheduleExpr === '0 18 * * *') {
    const targetHour = scheduleExpr === '0 9 * * *' ? 9 : 18;
    next.setSeconds(0, 0);
    next.setHours(targetHour, 0, 0, 0);
    if (next <= now) next.setDate(next.getDate() + 1);
    return formatLocaleDateTime(next);
  }

  if (scheduleExpr === '0 9 * * 1') {
    next.setSeconds(0, 0);
    next.setHours(9, 0, 0, 0);
    const day = next.getDay();
    const daysUntilMonday = day === 1 ? 7 : (8 - day) % 7;
    next.setDate(next.getDate() + daysUntilMonday);
    return formatLocaleDateTime(next);
  }

  if (scheduleExpr === '0 9 1 * *') {
    next.setSeconds(0, 0);
    next.setDate(1);
    next.setHours(9, 0, 0, 0);
    if (next <= now) next.setMonth(next.getMonth() + 1);
    return formatLocaleDateTime(next);
  }

  return null;
}

function formatLocaleDateTime(date: Date): string {
  try {
    return new Intl.DateTimeFormat(undefined, {
      month: 'short',
      day: 'numeric',
      hour: '2-digit',
      minute: '2-digit',
    }).format(date);
  } catch {
    return date.toLocaleString();
  }
}