/**
 * Central date/time formatting — pinned to Israel time (Asia/Jerusalem).
 *
 * WHY THIS EXISTS (INV-UI9 / G2):
 * Storage stays UTC end-to-end (Postgres TIMESTAMPTZ, API returns ISO-UTC).
 * Only the *display* layer is localized, and it is localized **deterministically**:
 * every human-facing timestamp renders in `Asia/Jerusalem`, regardless of the
 * host/container/browser timezone. The legal-ai container runs in UTC, so an
 * ad-hoc `new Date(iso).toLocaleDateString("he-IL")` shows UTC under SSR (and
 * UTC again on any non-Israel runtime) — that drift is exactly what this module
 * removes. Pinning `timeZone: "Asia/Jerusalem"` makes SSR and the browser agree.
 *
 * This is the ONE date formatter for the UI. Do not format timestamps ad-hoc
 * with `new Date(...).toLocaleDateString(...)` / `.toLocaleString(...)` /
 * `.getHours()` rendering elsewhere — route through these helpers so the tz is
 * always Israel and nothing drifts.
 *
 * Number formatting (e.g. `n.toLocaleString("he-IL")`) is NOT a timestamp and is
 * intentionally out of scope here.
 */

const TZ = "Asia/Jerusalem";
const LOCALE = "he-IL";

/** Coerce an ISO string / epoch-ms / Date into a valid Date, or null. */
function toDate(value: string | number | Date | null | undefined): Date | null {
  if (value == null) return null;
  const d = value instanceof Date ? value : new Date(value);
  return Number.isNaN(d.getTime()) ? null : d;
}

/**
 * Date only — `dd/MM/yyyy` in Israel time (e.g. "30/06/2026").
 * Matches the prior `toLocaleDateString("he-IL", {day,month:"2-digit",year:"numeric"})`.
 */
export function formatDate(
  value: string | number | Date | null | undefined,
  fallback = "—",
): string {
  const d = toDate(value);
  if (!d) return fallback;
  return new Intl.DateTimeFormat(LOCALE, {
    timeZone: TZ,
    day: "2-digit",
    month: "2-digit",
    year: "numeric",
  }).format(d);
}

/**
 * Date only — long month form (e.g. "30 ביוני 2026") in Israel time.
 * Matches the prior `toLocaleDateString("he-IL", {day:"numeric",month:"long",year:"numeric"})`.
 */
export function formatDateLong(
  value: string | number | Date | null | undefined,
  fallback = "",
): string {
  const d = toDate(value);
  if (!d) return fallback;
  return new Intl.DateTimeFormat(LOCALE, {
    timeZone: TZ,
    day: "numeric",
    month: "long",
    year: "numeric",
  }).format(d);
}

/**
 * Date only — short form, locale default (e.g. "30.6.2026") in Israel time.
 * Matches the prior bare `toLocaleDateString("he-IL")`.
 */
export function formatDateShort(
  value: string | number | Date | null | undefined,
  fallback = "—",
): string {
  const d = toDate(value);
  if (!d) return fallback;
  return new Intl.DateTimeFormat(LOCALE, { timeZone: TZ }).format(d);
}

/**
 * Date + time — `d בMMM yyyy, HH:mm` style in Israel time.
 * Matches the prior `{day:"numeric",month:"short",year:"numeric",hour,minute}`.
 */
export function formatDateTime(
  value: string | number | Date | null | undefined,
  fallback = "—",
): string {
  const d = toDate(value);
  if (!d) return fallback;
  return new Intl.DateTimeFormat(LOCALE, {
    timeZone: TZ,
    day: "numeric",
    month: "short",
    year: "numeric",
    hour: "2-digit",
    minute: "2-digit",
  }).format(d);
}

/**
 * Full date + time — locale default with time, Israel time.
 * Matches the prior bare `toLocaleString("he-IL")`.
 */
export function formatDateTimeFull(
  value: string | number | Date | null | undefined,
  fallback = "—",
): string {
  const d = toDate(value);
  if (!d) return fallback;
  return new Intl.DateTimeFormat(LOCALE, {
    timeZone: TZ,
    dateStyle: "short",
    timeStyle: "short",
  }).format(d);
}

/**
 * Time only — `HH:mm` in Israel time (e.g. "14:05").
 * Matches the prior `toLocaleTimeString("he-IL", {hour,minute})`.
 */
export function formatTime(
  value: string | number | Date | null | undefined,
  fallback = "—",
): string {
  const d = toDate(value);
  if (!d) return fallback;
  return new Intl.DateTimeFormat(LOCALE, {
    timeZone: TZ,
    hour: "2-digit",
    minute: "2-digit",
  }).format(d);
}

/**
 * ISO calendar date `YYYY-MM-DD` for the Israel-time day of the instant.
 * Deterministic replacement for `new Date(iso).toISOString().slice(0,10)`,
 * which yields the UTC day (off-by-one near midnight Israel time).
 */
export function formatIsoDate(
  value: string | number | Date | null | undefined,
  fallback = "—",
): string {
  const d = toDate(value);
  if (!d) return fallback;
  // en-CA's short date is ISO-shaped (YYYY-MM-DD); pin the tz so it's the Israel day.
  return new Intl.DateTimeFormat("en-CA", {
    timeZone: TZ,
    year: "numeric",
    month: "2-digit",
    day: "2-digit",
  }).format(d);
}

/**
 * The calendar year (number) of the Israel-time day for an instant.
 * Deterministic replacement for `new Date(iso).getFullYear()` (which uses the
 * runtime tz). Returns null when the value is absent/unparseable.
 */
export function getIsraelYear(
  value: string | number | Date | null | undefined,
): number | null {
  const d = toDate(value);
  if (!d) return null;
  const y = new Intl.DateTimeFormat("en-CA", { timeZone: TZ, year: "numeric" }).format(d);
  const n = Number(y);
  return Number.isNaN(n) ? null : n;
}

/**
 * The Israel-time calendar day of an instant as a sortable integer YYYYMMDD,
 * or null when absent/unparseable. Use this to compare two dates at *day*
 * precision in Israel time (e.g. hearing-date vs. today) without runtime-tz drift.
 */
export function israelDayKey(
  value: string | number | Date | null | undefined,
): number | null {
  const iso = formatIsoDate(value, ""); // "YYYY-MM-DD" or ""
  if (!iso) return null;
  const n = Number(iso.replace(/-/g, ""));
  return Number.isNaN(n) ? null : n;
}

/** Today's Israel-time calendar day as a sortable integer YYYYMMDD. */
export function todayIsraelDayKey(): number {
  return israelDayKey(new Date()) as number;
}

/**
 * The UTC-ms of midnight (00:00) of the instant's *Israel* calendar day.
 * Day-precision pivot for ms-based comparisons/diffs (e.g. hearing date vs.
 * today) that must not drift with the runtime timezone. Returns null when the
 * value is absent/unparseable. Built from the en-CA YYYY-MM-DD of the Israel day
 * combined with the Israel UTC offset at that instant, so two values from the
 * same Israel day always reduce to the same ms.
 */
export function israelMidnightMs(
  value: string | number | Date | null | undefined,
): number | null {
  const d = toDate(value);
  if (!d) return null;
  const iso = formatIsoDate(d, ""); // YYYY-MM-DD of the Israel day
  if (!iso) return null;
  const [y, m, day] = iso.split("-").map(Number);
  // Israel wall-clock midnight as a UTC instant: take naive UTC midnight of that
  // calendar day and subtract Israel's offset (Israel is ahead of UTC).
  const naiveUtcMidnight = Date.UTC(y, m - 1, day);
  const utc = new Date(d.toLocaleString("en-US", { timeZone: "UTC" }));
  const isr = new Date(d.toLocaleString("en-US", { timeZone: TZ }));
  const offsetMs = isr.getTime() - utc.getTime();
  return naiveUtcMidnight - offsetMs;
}

/** UTC-ms of midnight of *today's* Israel calendar day. */
export function todayIsraelMidnightMs(): number {
  return israelMidnightMs(new Date()) as number;
}

/**
 * Numeric date/time components of an instant in Israel time. For the rare call
 * site that builds a bespoke string from parts (e.g. a custom weekday + dd/MM
 * HH:mm deadline label) and must do so in Israel time rather than the runtime
 * tz. `weekday` is 0=Sunday … 6=Saturday (matching `Date.getDay()`).
 * Returns null when the value is absent/unparseable.
 */
export function israelParts(
  value: string | number | Date | null | undefined,
): { year: number; month: number; day: number; hour: number; minute: number; weekday: number } | null {
  const d = toDate(value);
  if (!d) return null;
  const parts = new Intl.DateTimeFormat("en-US", {
    timeZone: TZ,
    year: "numeric",
    month: "2-digit",
    day: "2-digit",
    hour: "2-digit",
    minute: "2-digit",
    weekday: "short",
    hour12: false,
  }).formatToParts(d);
  const get = (t: string) => parts.find((p) => p.type === t)?.value ?? "";
  const WD: Record<string, number> = { Sun: 0, Mon: 1, Tue: 2, Wed: 3, Thu: 4, Fri: 5, Sat: 6 };
  let hour = Number(get("hour"));
  if (hour === 24) hour = 0; // some engines emit "24" for midnight under hour12:false
  return {
    year: Number(get("year")),
    month: Number(get("month")),
    day: Number(get("day")),
    hour,
    minute: Number(get("minute")),
    weekday: WD[get("weekday")] ?? 0,
  };
}

/**
 * Relative "time ago" in Hebrew. Timezone-agnostic (it's a diff between two
 * absolute instants), but centralized here so all relative rendering lives in
 * one place. `units` selects the existing wording per call site so visible text
 * is unchanged:
 *   - "long":  עכשיו / לפני N דקות / לפני N שעות / לפני N ימים
 *   - "short": עכשיו / לפני N דק׳ / לפני N שע׳ / לפני N ימים
 *   - "tight": לפני Nד' / לפני Nש' / לפני N ימים  (no "now" bucket)
 */
export function formatRelative(
  value: string | number | Date | null | undefined,
  opts: { units?: "long" | "short" | "tight"; fallback?: string } = {},
): string {
  const { units = "short", fallback = "" } = opts;
  const d = toDate(value);
  if (!d) return fallback;

  const diffMs = Date.now() - d.getTime();
  const mins = Math.floor(diffMs / 60_000);
  const hours = Math.floor(mins / 60);
  const days = Math.floor(hours / 24);

  if (units === "tight") {
    if (mins < 60) return `לפני ${mins}ד'`;
    if (hours < 24) return `לפני ${hours}ש'`;
    return `לפני ${days} ימים`;
  }

  const now = "עכשיו";
  if (units === "long") {
    if (mins < 1) return now;
    if (mins < 60) return `לפני ${mins} דקות`;
    if (hours < 24) return `לפני ${hours} שעות`;
    return `לפני ${days} ימים`;
  }

  // "short"
  if (mins < 1) return now;
  if (mins < 60) return `לפני ${mins} דק׳`;
  if (hours < 24) return `לפני ${hours} שע׳`;
  return `לפני ${days} ימים`;
}