"use client";

import { useEffect, useRef, useState } from "react";
import { useRouter } from "next/navigation";
import Link from "next/link";
import { CheckCircle2Icon, XCircleIcon, ScanLineIcon, DownloadIcon } from "lucide-react";
import { Button } from "@/components/ui/button";
import { Skeleton } from "@/components/ui/skeleton";
import { useEvents } from "@/hooks/use-events";
import { countdownRender } from "@/lib/qr-dedupe";

type PairingState =
  | { phase: "waiting" }
  | { phase: "qr"; qrUrl: string }
  | { phase: "connected"; phoneNumber: string }
  | { phase: "timeout" };

interface PairLiveProps {
  accountId: string;
  label: string;
}

function CountdownBar({ seconds, total }: { seconds: number; total: number }) {
  const { pct, danger, expired } = countdownRender(seconds, total);
  const mm = Math.floor(seconds / 60);
  const ss = String(seconds % 60).padStart(2, "0");
  return (
    <div className="flex w-full max-w-64 flex-col gap-1">
      <div className="flex items-center justify-between text-xs">
        <span className="text-muted-foreground">
          {expired ? "Pairing window expired" : "Pairing expires in"}
        </span>
        {!expired && (
          <span
            className={`font-mono tabular-nums font-medium ${
              danger ? "text-destructive" : "text-foreground"
            }`}
          >
            {mm}:{ss}
          </span>
        )}
      </div>
      <div className="h-1 w-full overflow-hidden rounded-full bg-muted">
        <div
          className={`h-full transition-[width] duration-1000 ease-linear ${
            danger ? "bg-destructive" : "bg-foreground/70"
          }`}
          style={{ width: `${pct}%` }}
          aria-hidden
        />
      </div>
    </div>
  );
}

// Match the bot's PAIR_TIMEOUT_MS — 5 minutes — so the pairing-window
// timer is the single source of truth for "you have to scan by then".
// Individual QR rotations (~5 s each from Baileys) refresh the displayed
// QR but do NOT reset this timer — that would punish the user with a
// constantly-resetting countdown.
const PAIRING_WINDOW_SEC = 5 * 60;

export function PairLive({ accountId, label }: PairLiveProps) {
  const router = useRouter();
  const [pairingState, setPairingState] = useState<PairingState>({ phase: "waiting" });
  const [countdown, setCountdown] = useState(PAIRING_WINDOW_SEC);
  const timerRef = useRef<ReturnType<typeof setInterval> | null>(null);
  const startedRef = useRef(false);

  /** Start the pairing-window countdown once. Subsequent QR refreshes do
   *  not restart this — only mount/connect/timeout/unmount touches it. */
  const startCountdown = () => {
    if (startedRef.current) return;
    startedRef.current = true;
    if (timerRef.current) clearInterval(timerRef.current);
    setCountdown(PAIRING_WINDOW_SEC);
    timerRef.current = setInterval(() => {
      setCountdown((c) => {
        if (c <= 1) {
          if (timerRef.current) clearInterval(timerRef.current);
          return 0;
        }
        return c - 1;
      });
    }, 1000);
  };

  useEvents({
    "session.qr": (data) => {
      if (data.accountId !== accountId) return;
      // Bust the URL with the timestamp so the browser refetches each time.
      setPairingState({ phase: "qr", qrUrl: `/api/qr/${accountId}?t=${data.ts}` });
      // Idempotent — only the first QR starts the global pairing-window
      // timer; later QR rotations leave it ticking.
      startCountdown();
    },
    "session.connected": (data) => {
      if (data.accountId !== accountId) return;
      if (timerRef.current) clearInterval(timerRef.current);
      setPairingState({
        phase: "connected",
        phoneNumber: data.phoneNumber ?? "",
      });
    },
    "session.timeout": (data) => {
      if (data.accountId !== accountId) return;
      if (timerRef.current) clearInterval(timerRef.current);
      setPairingState({ phase: "timeout" });
    },
  });

  // Auto-redirect on connected
  useEffect(() => {
    if (pairingState.phase !== "connected") return;
    const t = setTimeout(() => {
      router.push(`/accounts/${accountId}` as never);
    }, 3000);
    return () => clearTimeout(t);
  }, [pairingState.phase, accountId, router]);

  // Cleanup interval on unmount
  useEffect(() => {
    return () => {
      if (timerRef.current) clearInterval(timerRef.current);
    };
  }, []);

  return (
    <div className="flex flex-col items-center gap-6 py-4">
      {/* Label chip */}
      <div className="flex items-center gap-1.5 rounded-full border border-border bg-muted/50 px-3 py-1 text-xs font-medium text-muted-foreground">
        <ScanLineIcon className="size-3" />
        {label}
      </div>

      {/* State display */}
      {pairingState.phase === "waiting" && (
        <div className="flex flex-col items-center gap-3">
          <Skeleton className="size-64 rounded-lg" />
          <p className="text-sm text-muted-foreground">Generating QR…</p>
        </div>
      )}

      {pairingState.phase === "qr" && (
        <div className="flex flex-col items-center gap-4">
          {/* Pairing-window countdown — single source of truth.
              The QR image rotates every ~5 s but this timer keeps ticking
              against the bot's PAIR_TIMEOUT (5 min). */}
          <CountdownBar seconds={countdown} total={PAIRING_WINDOW_SEC} />

          {/* QR image */}
          {/* eslint-disable-next-line @next/next/no-img-element */}
          <img
            src={pairingState.qrUrl}
            alt="WhatsApp QR code"
            width={256}
            height={256}
            className="rounded-lg ring-1 ring-foreground/10"
          />

          <div className="flex flex-col items-center gap-2 text-center">
            <p className="text-sm font-medium">Scan with WhatsApp → Linked Devices</p>
            <p className="text-xs text-muted-foreground">
              Open WhatsApp → tap ⋮ → Linked Devices → Link a device
            </p>
            <p className="text-xs text-muted-foreground/80 italic">
              The QR rotates automatically every few seconds — scan whichever one is showing.
            </p>
            <Button asChild variant="outline" size="sm" className="mt-1">
              <a
                href={pairingState.qrUrl}
                download={`whatsapp-qr-${label.replace(/\s+/g, "-").toLowerCase() || accountId}.png`}
              >
                <DownloadIcon />
                Save QR
              </a>
            </Button>
          </div>
        </div>
      )}

      {pairingState.phase === "connected" && (
        <div className="flex flex-col items-center gap-4 text-center">
          <div className="flex size-16 items-center justify-center rounded-full bg-green-500/10">
            <CheckCircle2Icon className="size-8 text-green-600 dark:text-green-400" />
          </div>
          <div className="space-y-1">
            <p className="text-base font-semibold">Account connected!</p>
            {pairingState.phoneNumber && (
              <p className="text-sm text-muted-foreground">
                Connected as{" "}
                <span className="font-mono font-medium text-foreground">
                  +{pairingState.phoneNumber.replace(/^\+/, "")}
                </span>
              </p>
            )}
            <p className="text-xs text-muted-foreground">Redirecting in 3 seconds…</p>
          </div>
        </div>
      )}

      {pairingState.phase === "timeout" && (
        <div className="flex flex-col items-center gap-4 text-center">
          <div className="flex size-16 items-center justify-center rounded-full bg-destructive/10">
            <XCircleIcon className="size-8 text-destructive" />
          </div>
          <div className="space-y-1">
            <p className="text-base font-semibold">Pairing timed out</p>
            <p className="text-xs text-muted-foreground">
              The QR window closed before a device was linked.
            </p>
          </div>
          <Button asChild size="sm">
            {/* eslint-disable-next-line @typescript-eslint/no-explicit-any */}
            <Link href={`/accounts/${accountId}` as any}>
              Back to account — try again
            </Link>
          </Button>
        </div>
      )}
    </div>
  );
}