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

/** Last few non-blank lines of a string — a compact "what the model is doing now"
 *  tail (mirrors ModelActivityPanel's tail-line logic, at a smaller size). Returned
 *  as an array so each line renders as its own formatted log row. */
function tailLines(s: string, n = 5): string[] {
  return s
    .split("\n")
    .map((l) => l.trimEnd())
    .filter((l) => l.trim() !== "")
    .slice(-n);
}

/** 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 tailRows = tailLines(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 flex-col gap-1.5">
          <div className="flex min-w-0 items-center gap-2 text-sm text-muted-foreground">
            {/* Pure status indicator — opening the activity panel now lives on the
                dedicated arrow toggle in the header, not on this spinner. */}
            <span className="grid size-5 shrink-0 place-items-center text-primary">
              <WorkingSpinner spinning className="size-3.5" />
            </span>
            <span className="shrink-0 tabular-nums">{elapsed}s</span>
            <span className="sr-only">ThothII is working</span>
          </div>
          {tailRows.length > 0 && (
            <ol className="ml-7 flex flex-col gap-0.5 overflow-hidden rounded-md border border-border/50 bg-muted/40 px-3 py-2">
              {tailRows.map((line, i) => {
                const isLast = i === tailRows.length - 1;
                return (
                  <li
                    key={i}
                    className={[
                      "flex items-baseline gap-2 font-mono text-[0.72rem] leading-relaxed",
                      isLast ? "text-foreground/80" : "text-muted-foreground/55",
                    ].join(" ")}
                  >
                    <span
                      aria-hidden
                      className={[
                        "shrink-0 select-none",
                        isLast ? "text-primary" : "text-muted-foreground/35",
                      ].join(" ")}
                    >
                      ›
                    </span>
                    <span className="min-w-0 flex-1 truncate">{line}</span>
                  </li>
                );
              })}
            </ol>
          )}
        </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>
  );
}