import { useState } from "react";
import { useTranslation } from "react-i18next";
import { useMutation, useQuery, useQueryClient } from "@tanstack/react-query";
import { fetchActiveSessions, reopenBarrier, type ActiveSession } from "./api.js";
import { qk } from "./lib/query.js";
import { useShift } from "./lib/use-shift.js";
import { formatDuration, formatRelativeDateTime } from "./lib/format.js";
import { Panel } from "./ui/Panel.js";

// Active Sessions panel. A session is "active" while still inside OR exited-but-
// within-grace (the barrier is UNCONFIRMED, so a paid/exited car is presumed
// possibly-present until grace runs out). Lets the operator find a stuck car —
// damaged ticket, dead scanner, or a phantom barrier re-close — without a scan:
//   - click a row → the pay/exit modal (pay an unpaid car, or review),
//   - "Open barrier" (PAID sessions only) → an audited human-intervention re-pulse.
// No payment → no Open barrier button (the no-unpaid-bypass rule).
// See wiki/concepts/booth-exit-flow.md.

function statusBadge(s: ActiveSession): { key: string; cls: string } {
  if (s.subscription) return { key: "booth.badgeSubscription", cls: "text-term-cyan" };
  if (!s.open && s.withinGrace) return { key: "booth.badgeExiting", cls: "text-term-cyan" };
  if (s.paidAt) return { key: "booth.badgePaid", cls: "text-term-green" };
  return { key: "booth.badgeUnpaid", cls: "text-term-amber" };
}

export function ActiveSessions({ onPick }: { onPick: (identity: string) => void }) {
  const { t } = useTranslation();
  const qc = useQueryClient();
  // The audited barrier re-open is a money-path action (server-gated on an open
  // shift); disable it unless this operator's shift is open.
  const { isOpen: shiftOpen, isMine: shiftMine } = useShift();
  const shiftReady = shiftOpen && shiftMine;
  const { data, isLoading } = useQuery({
    queryKey: qk.activeSessions,
    queryFn: fetchActiveSessions,
    // Belt-and-braces refresh in case a grace window expires with no ledger event
    // to invalidate the cache (the WS only pushes on appends).
    refetchInterval: 15_000,
  });

  const reopen = useMutation({
    mutationFn: (identity: string) => reopenBarrier(identity),
    onSettled: () => {
      void qc.invalidateQueries({ queryKey: qk.activeSessions });
      void qc.invalidateQueries({ queryKey: qk.events });
    },
  });
  const [reopenMsg, setReopenMsg] = useState<{ id: string; text: string; ok: boolean } | null>(null);

  const sessions = data?.sessions ?? [];

  async function handleReopen(s: ActiveSession) {
    setReopenMsg(null);
    try {
      const r = await reopen.mutateAsync(s.identity);
      setReopenMsg({
        id: s.identity,
        ok: r.opened,
        text: r.opened ? t("booth.barrierOpened") : r.reason ?? t("booth.openManually"),
      });
    } catch (e) {
      setReopenMsg({ id: s.identity, ok: false, text: (e as Error).message });
    }
  }

  return (
    <Panel
      title={t("booth.activeSessions")}
      right={
        <span className="text-[10px] uppercase tracking-wider text-term-muted">
          {sessions.length} {t("booth.insideCount")}
        </span>
      }
      className="min-h-0"
    >
      <div className="h-full overflow-y-auto pr-1">
        {sessions.length === 0 ? (
          <div className="text-term-muted">{isLoading ? t("common.loading") : t("booth.noActiveSessions")}</div>
        ) : (
          sessions.map((s) => {
            const badge = statusBadge(s);
            const msg = reopenMsg?.id === s.identity ? reopenMsg : null;
            return (
              <div
                key={s.identity}
                className="flex items-center gap-3 border-b border-term-border/50 py-1.5 text-[12px] tabular-nums"
              >
                <button
                  type="button"
                  onClick={() => onPick(s.identity)}
                  className="flex flex-1 items-center gap-3 text-left hover:text-term-amber"
                  title={t("booth.openPayExit")}
                >
                  <span className="text-term-text">
                    {s.subscription ? `★ ${s.subscriptionHolder ?? t("subs.unnamed")}` : s.identity}
                  </span>
                  <span className="text-term-muted">{formatRelativeDateTime(s.enteredAt, t)}</span>
                  <span className="text-term-muted">{formatDuration(s.enteredAt, new Date().toISOString())}</span>
                  <span className={`ml-auto w-16 text-right font-semibold uppercase ${badge.cls}`}>{t(badge.key)}</span>
                </button>

                {/* Open barrier — PAID transient OR a SUBSCRIPTION (prepaid). An
                    unpaid transient has no button (no-unpaid-bypass). */}
                {s.paidAt || s.subscription ? (
                  <button
                    type="button"
                    disabled={reopen.isPending || !shiftReady}
                    onClick={() => handleReopen(s)}
                    className="btn btn-pay btn-sm shrink-0"
                    title={shiftReady ? t("booth.openBarrierTitle") : t("shift.gateTitle")}
                  >
                    {t("booth.openBarrier")}
                  </button>
                ) : (
                  <span className="w-[88px] shrink-0" />
                )}

                {msg && (
                  <span className={`shrink-0 text-[10px] ${msg.ok ? "text-term-green" : "text-term-red"}`}>
                    {msg.text}
                  </span>
                )}
              </div>
            );
          })
        )}
      </div>
    </Panel>
  );
}