import { moment } from "obsidian";
import type { M } from "./types";

/**
 * Parse a date-ish input (frontmatter Date object, "YYYY-MM-DD" string, or any
 * moment-parseable string) into a moment. Returns null if unparseable.
 */
export function parseMoment(input: unknown): M | null {
  if (input == null || input === "") return null;

  if (input instanceof Date) {
    if (Number.isNaN(input.getTime())) return null;

    const isUtcMidnight =
      input.getUTCHours() === 0 &&
      input.getUTCMinutes() === 0 &&
      input.getUTCSeconds() === 0 &&
      input.getUTCMilliseconds() === 0;

    if (isUtcMidnight) {
      return moment({
        year: input.getUTCFullYear(),
        month: input.getUTCMonth(),
        day: input.getUTCDate(),
      }).startOf("day");
    }

    return moment(input);
  }

  const s = String(input).trim();
  const dateOnly = moment(s, "YYYY-MM-DD", true);
  if (dateOnly.isValid()) return dateOnly.startOf("day");

  const any = moment(s);
  return any.isValid() ? any : null;
}

/** Break the span between two moments into years/months/days/hours/minutes. */
export function formatSpan(
  from: M,
  to: M,
  verbose: boolean
): { text: string; isNegative: boolean } {
  let a = from.clone();
  let b = to.clone();

  const isNegative = b.isBefore(a);
  if (isNegative) [a, b] = [b, a];

  const years = b.diff(a, "years"); a.add(years, "years");
  const months = b.diff(a, "months"); a.add(months, "months");
  const days = b.diff(a, "days"); a.add(days, "days");
  const hours = b.diff(a, "hours"); a.add(hours, "hours");
  const minutes = b.diff(a, "minutes");

  if (verbose) {
    const parts: string[] = [];
    if (years) parts.push(`${years} year${years === 1 ? "" : "s"}`);
    if (months) parts.push(`${months} month${months === 1 ? "" : "s"}`);
    if (days) parts.push(`${days} day${days === 1 ? "" : "s"}`);
    if (hours && parts.length < 3) parts.push(`${hours} hour${hours === 1 ? "" : "s"}`);
    if (minutes && parts.length < 3) parts.push(`${minutes} minute${minutes === 1 ? "" : "s"}`);
    return { text: parts.join(", ") || "0 minutes", isNegative };
  } else {
    const parts: string[] = [];
    if (years) parts.push(`${years}y`);
    if (months) parts.push(`${months}mo`);
    if (days) parts.push(`${days}d`);
    if (hours && parts.length < 3) parts.push(`${hours}h`);
    if (minutes && parts.length < 3) parts.push(`${minutes}m`);
    return { text: parts.join(" ") || "0m", isNegative };
  }
}