export type ReminderOffsetUnit = "minutes" | "hours" | "days" | "weeks";

export type ReminderPreset = {
  label: string;
  offsetMinutes: number;
};

export const REMINDER_PRESETS: ReminderPreset[] = [
  { label: "At event time", offsetMinutes: 0 },
  { label: "5 minutes before", offsetMinutes: 5 },
  { label: "15 minutes before", offsetMinutes: 15 },
  { label: "30 minutes before", offsetMinutes: 30 },
  { label: "1 hour before", offsetMinutes: 60 },
  { label: "2 hours before", offsetMinutes: 120 },
  { label: "1 day before", offsetMinutes: 1440 },
  { label: "2 days before", offsetMinutes: 2880 },
  { label: "1 week before", offsetMinutes: 10080 },
];

export function formatReminderOffset(offsetMinutes: number): string {
  const preset = REMINDER_PRESETS.find((p) => p.offsetMinutes === offsetMinutes);
  if (preset) return preset.label;

  if (offsetMinutes === 0) return "At event time";
  if (offsetMinutes % 10080 === 0) {
    const weeks = offsetMinutes / 10080;
    return weeks === 1 ? "1 week before" : `${weeks} weeks before`;
  }
  if (offsetMinutes % 1440 === 0) {
    const days = offsetMinutes / 1440;
    return days === 1 ? "1 day before" : `${days} days before`;
  }
  if (offsetMinutes % 60 === 0) {
    const hours = offsetMinutes / 60;
    return hours === 1 ? "1 hour before" : `${hours} hours before`;
  }
  return offsetMinutes === 1 ? "1 minute before" : `${offsetMinutes} minutes before`;
}

export function customOffsetToMinutes(value: number, unit: ReminderOffsetUnit): number {
  const safe = Math.max(0, Math.floor(value));
  switch (unit) {
    case "minutes":
      return safe;
    case "hours":
      return safe * 60;
    case "days":
      return safe * 1440;
    case "weeks":
      return safe * 10080;
  }
}

export function normalizeReminderOffsets(offsets: number[]): number[] {
  return [...new Set(offsets.filter((n) => Number.isFinite(n) && n >= 0))].toSorted(
    (a, b) => b - a,
  );
}

export function fireAtForEventStart(startAt: Date, offsetMinutes: number): Date {
  return new Date(startAt.getTime() - offsetMinutes * 60_000);
}