import { useEffect, useReducer, useState } from "react";
import { useSessionStore } from "../store/sessionStore";

/** Last few words of a string — a compact "what the model is doing now" tail. */
function lastWords(s: string, n = 8): string {
  const w = s.trim().split(/\s+/).filter(Boolean);
  return w.slice(-n).join(" ");
}

/** The minimal central view: the user's last input/choice, a live "working" indicator
 *  (elapsed time + a short tail of the model stream) while the model is busy, and the
 *  gate's curated messages for the current step. The full verbose stream lives in the
 *  left Model-activity panel. */
export function CentralStatus({ working }: { working: boolean }) {
  const lastUserEntry = useSessionStore((s) => s.lastUserEntry);
  const stepMessages = useSessionStore((s) => s.stepMessages);
  const transcript = useSessionStore((s) => s.transcript);

  const [startedAt, setStartedAt] = useState<number | null>(null);
  const [, tick] = useReducer((x: number) => x + 1, 0);

  // Start the per-step timer when work begins; tick once a second so the elapsed
  // display updates; clear it when work stops.
  useEffect(() => {
    if (!working) {
      setStartedAt(null);
      return;
    }
    setStartedAt((prev) => prev ?? Date.now());
    const id = setInterval(tick, 1000);
    return () => clearInterval(id);
  }, [working]);

  if (!working && !lastUserEntry && stepMessages.length === 0) return null;

  const elapsed = startedAt ? Math.max(0, Math.floor((Date.now() - startedAt) / 1000)) : 0;
  const tail = lastWords(transcript.at(-1)?.text ?? "");

  return (
    <div className="flex flex-col gap-3">
      {lastUserEntry && (
        <div className="rounded-lg border border-border/70 bg-card px-3 py-2">
          <span className="text-[0.65rem] font-semibold uppercase tracking-wide text-muted-foreground">
            {lastUserEntry.kind === "input" ? "You asked" : "You chose"}
          </span>
          <p className="mt-0.5 text-sm text-foreground">{lastUserEntry.text}</p>
        </div>
      )}

      {working && (
        <div className="flex min-w-0 items-center gap-2 text-sm text-muted-foreground">
          <span className="size-1.5 shrink-0 animate-pulse rounded-full bg-primary" aria-hidden />
          <span className="shrink-0 tabular-nums">{elapsed}s</span>
          {tail && <span className="min-w-0 truncate text-muted-foreground/70">· {tail}</span>}
          <span className="sr-only">ThothII is working</span>
        </div>
      )}

      {stepMessages.map((m, i) => (
        <p
          key={i}
          className={[
            "text-sm",
            m.level === "error" ? "text-destructive"
              : m.level === "warning" ? "text-amber-600"
              : "text-foreground/90",
          ].join(" ")}
        >
          {m.text}
        </p>
      ))}
    </div>
  );
}