import dayjs from "dayjs";
import customParseFormat from "dayjs/plugin/customParseFormat";
import utc from "dayjs/plugin/utc";

dayjs.extend(utc);
dayjs.extend(customParseFormat);

const DATE_ONLY_RE = /^\d{4}-\d{2}-\d{2}$/;
const NUMERIC_RE = /^-?\d+$/;

export const nowMs = (): number => dayjs().valueOf();

export const parseToMs = (input: string | number): number => {
  if (typeof input === "number") {
    if (!Number.isFinite(input)) throw new Error(`Invalid numeric timestamp: ${input}`);
    return input;
  }
  const trimmed = input.trim();
  if (trimmed === "") throw new Error("Empty date input");
  if (NUMERIC_RE.test(trimmed)) {
    const n = Number(trimmed);
    if (!Number.isFinite(n)) throw new Error(`Invalid numeric timestamp: ${input}`);
    return n;
  }
  const d = dayjs.utc(trimmed);
  if (!d.isValid()) throw new Error(`Cannot parse date: ${input}`);
  return d.valueOf();
};

export interface RangeBounds {
  sinceMs?: number;
  untilMs?: number;
}

export const parseRangeBounds = (since?: string, until?: string): RangeBounds => {
  const out: RangeBounds = {};
  if (since !== undefined && since !== "") {
    out.sinceMs = parseToMs(since);
  }
  if (until !== undefined && until !== "") {
    const trimmed = until.trim();
    out.untilMs = DATE_ONLY_RE.test(trimmed)
      ? dayjs.utc(trimmed).endOf("day").valueOf()
      : parseToMs(trimmed);
  }
  if (out.sinceMs !== undefined && out.untilMs !== undefined && out.sinceMs > out.untilMs) {
    throw new Error(`Invalid range: since (${since ?? ""}) is after until (${until ?? ""})`);
  }
  return out;
};

export const formatDate = (ms: number): string => dayjs(ms).format("YYYY-MM-DD");

export const formatIso = (ms: number): string => dayjs(ms).format();

export const formatDateTime = (ms: number): string => dayjs(ms).format("YYYY-MM-DD HH:mm:ss");

/** Parse Y/M/D (single or zero-padded) in UTC. Returns null on failure. */
export const parseYmdUtc = (year: string, month: string, day: string): number | null => {
  const d = dayjs.utc(`${year}-${month}-${day}`, "YYYY-M-D", true);
  return d.isValid() ? d.valueOf() : null;
};