'use client';

import { useEffect, useState } from 'react';
import { cn } from '@/lib/cn';

interface Probe {
  name: string;
  url: string;
  description: string;
}

const PROBES: Probe[] = [
  {
    name: 'Dashboard',
    url: '/login',
    description: 'Web frontend (Next.js)',
  },
  {
    name: 'Control plane API',
    url: '/api/health',
    description: 'Fastify control plane via /api proxy',
  },
];

type State = 'pending' | 'ok' | 'down';

interface Result {
  state: State;
  latencyMs: number | null;
  detail: string | null;
}

export default function Status() {
  const [results, setResults] = useState<Record<string, Result>>(() =>
    Object.fromEntries(PROBES.map((p) => [p.name, { state: 'pending', latencyMs: null, detail: null }])),
  );

  useEffect(() => {
    let cancelled = false;
    async function probe() {
      const next: Record<string, Result> = {};
      for (const p of PROBES) {
        const start = performance.now();
        try {
          const res = await fetch(p.url, { cache: 'no-store' });
          const latency = Math.round(performance.now() - start);
          next[p.name] = {
            state: res.ok ? 'ok' : 'down',
            latencyMs: latency,
            detail: res.ok ? `HTTP ${res.status}` : `HTTP ${res.status}`,
          };
        } catch (e) {
          next[p.name] = {
            state: 'down',
            latencyMs: null,
            detail: (e as Error).message,
          };
        }
      }
      if (!cancelled) setResults(next);
    }
    probe();
    const interval = setInterval(probe, 10_000);
    return () => {
      cancelled = true;
      clearInterval(interval);
    };
  }, []);

  const anyDown = Object.values(results).some((r) => r.state === 'down');
  const allPending = Object.values(results).every((r) => r.state === 'pending');

  return (
    <div className="mx-auto max-w-3xl px-6 py-16">
      <header className="mb-10">
        <div className="text-[11px] uppercase tracking-[0.16em] text-[--color-fg-subtle]">
          System status
        </div>
        <h1 className="mt-2 text-[32px] font-semibold tracking-tight">
          {allPending ? 'Checking…' : anyDown ? 'Partial outage' : 'All systems operational'}
        </h1>
        <p className="mt-3 text-[14px] leading-relaxed text-[--color-fg-muted]">
          Live health probes against each service. Refreshes every 10 seconds.
        </p>
      </header>

      <div className="panel divide-y divide-[--color-border]">
        {PROBES.map((p) => {
          const r = results[p.name]!;
          return (
            <div key={p.name} className="flex items-center justify-between px-4 py-3">
              <div>
                <div className="text-[13.5px] font-medium">{p.name}</div>
                <div className="text-[12px] text-[--color-fg-subtle]">{p.description}</div>
              </div>
              <div className="flex items-center gap-3 text-[12px]">
                {r.latencyMs !== null && (
                  <span className="mono text-[--color-fg-subtle]">{r.latencyMs}ms</span>
                )}
                <Dot state={r.state} />
                <span className={cn(stateClass(r.state), 'font-medium tabular-nums')}>
                  {stateLabel(r.state)}
                </span>
              </div>
            </div>
          );
        })}
      </div>

      <p className="mt-8 text-[12px] text-[--color-fg-subtle]">
        Production status board: BetterStack-hosted at status.buildmymcpserver.com (set up
        post-launch).
      </p>
    </div>
  );
}

function Dot({ state }: { state: State }) {
  const color =
    state === 'ok' ? 'bg-emerald-400' : state === 'down' ? 'bg-red-400' : 'bg-zinc-400';
  return (
    <span
      className={cn('size-2 rounded-full', color)}
      style={state === 'ok' ? { animation: 'pulse-dot 1.6s ease-in-out infinite' } : undefined}
    />
  );
}

function stateLabel(state: State): string {
  if (state === 'ok') return 'Operational';
  if (state === 'down') return 'Down';
  return 'Checking';
}

function stateClass(state: State): string {
  if (state === 'ok') return 'text-emerald-300';
  if (state === 'down') return 'text-red-300';
  return 'text-[--color-fg-subtle]';
}