export type EventAvailabilityInput = {
  status?: string | null;
  registration_start_date?: string | null;
  registration_end_date?: string | null;
  start_time?: string | null;
  end_time?: string | null;
  capacity?: number | null;
  registration_count?: number | null;
};

export function getEventPath(event: { id: number; slug?: string | null }) {
  const segment = event.slug?.trim() || String(event.id);
  return `/events/${encodeURIComponent(segment)}`;
}

export type EventRegistrationState =
  | "open"
  | "not_started"
  | "closed"
  | "full"
  | "unavailable";

function timestamp(value?: string | null) {
  if (!value) return null;
  const parsed = new Date(value).getTime();
  return Number.isFinite(parsed) ? parsed : null;
}

export function getEventRegistrationState(
  event: EventAvailabilityInput,
  now = Date.now(),
): { state: EventRegistrationState; remaining: number | null } {
  if (event.status !== "published") {
    return { state: "unavailable", remaining: null };
  }

  const endsAt = timestamp(event.registration_end_date);
  if (endsAt !== null && now > endsAt) {
    return { state: "closed", remaining: getRemainingCapacity(event) };
  }

  const startsAt = timestamp(event.registration_start_date);
  if (startsAt !== null && now < startsAt) {
    return { state: "not_started", remaining: getRemainingCapacity(event) };
  }

  const remaining = getRemainingCapacity(event);
  if (remaining !== null && remaining <= 0) {
    return { state: "full", remaining: 0 };
  }

  return { state: "open", remaining };
}

function getRemainingCapacity(event: EventAvailabilityInput) {
  if (event.capacity == null || !Number.isFinite(Number(event.capacity))) {
    return null;
  }

  const used = Number.isFinite(Number(event.registration_count))
    ? Number(event.registration_count)
    : 0;
  return Math.max(0, Number(event.capacity) - used);
}

export function getEventCardState(
  event: EventAvailabilityInput,
  now = Date.now(),
): "past" | "full" | "upcoming" {
  const endsAt = timestamp(event.end_time);
  if (event.status === "completed" || (endsAt !== null && endsAt < now)) {
    return "past";
  }

  if (getEventRegistrationState(event, now).state === "full") {
    return "full";
  }

  return "upcoming";
}

export function getEventBrowseLabel(event: EventAvailabilityInput, now = Date.now()) {
  if (getEventCardState(event, now) === "past") return "برگزار شده";
  if (getEventRegistrationState(event, now).state === "open") return "درحال برگزاری";
  const startsAt = timestamp(event.start_time);
  if (startsAt !== null && startsAt <= now) return "درحال برگزاری";
  return "به‌زودی";
}

export function getEventRegistrationMessage(event: EventAvailabilityInput, now = Date.now()) {
  if (getEventCardState(event, now) === "past") return "این رویداد برگزار شده است";
  const registration = getEventRegistrationState(event, now);
  if (registration.state === "not_started") return "ثبت‌نام هنوز آغاز نشده است";
  if (registration.state === "closed") return "زمان ثبت‌نام به پایان رسیده است";
  if (registration.state === "full") return "ظرفیت ثبت‌نام تکمیل شده است";
  if (registration.state === "unavailable") return "امکان ثبت‌نام وجود ندارد";
  if (registration.remaining === null) return "ثبت‌نام در حال انجام است";
  return `${registration.remaining.toLocaleString("fa-IR")} نفر ظرفیت باقی‌مانده`;
}

export type RegistrationErrorKind =
  | "already_registered"
  | "not_started"
  | "closed"
  | "full"
  | "unknown";

function normalizeApiMessage(message: unknown) {
  return String(message ?? "")
    .replace(/[يى]/g, "ی")
    .replace(/\u200c/g, " ")
    .replace(/\s+/g, " ")
    .trim()
    .toLocaleLowerCase();
}

export function classifyRegistrationError(message: unknown): RegistrationErrorKind {
  const normalized = normalizeApiMessage(message);
  if (normalized.includes("already registered") || normalized.includes("قبلا در این ایونت ثبت نام کرده اید")) {
    return "already_registered";
  }
  if (normalized.includes("زمان ثبت نام هنوز آغاز نشده") || normalized.includes("registration has not started")) {
    return "not_started";
  }
  if (normalized.includes("مهلت ثبت نام به پایان رسیده") || normalized.includes("registration period has ended")) {
    return "closed";
  }
  if (normalized.includes("ظرفیت شرکت کنندگان تکمیل است") || normalized.includes("event is full")) {
    return "full";
  }
  return "unknown";
}

export type PaymentOutcome = "paid" | "pending" | "failed" | "canceled" | "unknown";

export function getPaymentOutcome(status: unknown): PaymentOutcome {
  const normalized = normalizeApiMessage(status);
  if (["success", "paid", "ok", "پرداخت شده", "تایید شده"].includes(normalized)) {
    return "paid";
  }
  if (["pending", "initiated", "init", "در انتظار", "در حال پردازش"].includes(normalized)) {
    return "pending";
  }
  if (["canceled", "cancelled", "لغو شده"].includes(normalized)) {
    return "canceled";
  }
  if (["failed", "failure", "ناموفق"].includes(normalized)) {
    return "failed";
  }
  return "unknown";
}

export type RegistrationOutcome = "confirmed" | "pending" | "canceled" | "unknown";

export function getRegistrationOutcome(status: unknown): RegistrationOutcome {
  const normalized = normalizeApiMessage(status);
  if (["confirmed", "attended", "approved", "تایید شده"].includes(normalized)) {
    return "confirmed";
  }
  if (["pending", "در انتظار"].includes(normalized)) {
    return "pending";
  }
  if (["canceled", "cancelled", "لغو شده"].includes(normalized)) {
    return "canceled";
  }
  return "unknown";
}