/**
 * NEON SURVIVORS — Leaderboard Worker (Cloudflare Workers + KV)
 *
 * Deploy:
 *   1. wrangler kv:namespace create LB
 *   2. paste the returned id into wrangler.toml
 *   3. wrangler deploy
 *
 * Endpoints:
 *   GET  /top?scope=daily:20260822|stage:frostcave:2&n=10
 *   POST /submit { name, time, kills, gold, lv, stageId, grade, endless, daily, win, day, sig }
 *
 * `sig` is a lightweight checksum (same algorithm as the client) that deters
 * casual tampering. True server authority would require session validation.
 */

const SALT = 'NSv1-lb-salt-v1';

async function lbSig(obj) {
  const data = new TextEncoder().encode(SALT + JSON.stringify(obj));
  let h = 2166136261 >>> 0;
  const view = data;
  for (let i = 0; i < view.length; i++) {
    h ^= view[i];
    h = Math.imul(h, 16777619) >>> 0;
  }
  // second avalanche pass so short payloads spread
  h ^= h >>> 13; h = Math.imul(h, 1274126177) >>> 0; h ^= h >>> 16;
  return ('0000000' + h.toString(36)).slice(-8);
}

function jsonRes(data, status = 200) {
  return new Response(JSON.stringify(data), {
    status,
    headers: {
      'content-type': 'application/json; charset=utf-8',
      'access-control-allow-origin': '*',
      'access-control-allow-headers': 'content-type',
      'access-control-allow-methods': 'GET,POST,OPTIONS'
    }
  });
}

export default {
  async fetch(req, env) {
    const url = new URL(req.url);
    if (req.method === 'OPTIONS') return new Response(null, { status: 204 });

    if (url.pathname === '/top' && req.method === 'GET') {
      const scope = (url.searchParams.get('scope') || '').slice(0, 48);
      const n = Math.min(50, Math.max(1, parseInt(url.searchParams.get('n') || '10', 10)));
      if (!scope) return jsonRes({ ok: false, error: 'scope' }, 400);
      const raw = await env.LB.get('b:' + scope);
      const rows = raw ? JSON.parse(raw) : [];
      return jsonRes({ ok: true, scope, rows: rows.slice(0, n) });
    }

    if (url.pathname === '/submit' && req.method === 'POST') {
      let b;
      try { b = await req.json(); } catch (e) { return jsonRes({ ok: false, error: 'json' }, 400); }
      const time = Math.floor(+b.time || 0);
      const entry = {
        n: String(b.name || 'Anon').slice(0, 16),
        t: time,
        k: Math.max(0, Math.min(999999, Math.floor(+b.kills || 0))),
        g: Math.max(0, Math.min(9999999, Math.floor(+b.gold || 0))),
        lv: Math.max(1, Math.min(200, Math.floor(+b.lv || 1))),
        w: b.win ? 1 : 0,
        st: String(b.stageId || '').slice(0, 24),
        gr: Math.max(0, Math.min(3, +b.grade | 0))
      };
      // scope: daily board uses UTC day; stage boards keyed by stage+grade
      const day = new Date().toISOString().slice(0, 10).replace(/-/g, '');
      let scope;
      if (b.daily) scope = 'daily:' + day;
      else if (time >= 60) scope = 'stage:' + (entry.st || 'graveyard') + ':' + entry.gr;
      else return jsonRes({ ok: false, error: 'too_short' }, 400);

      // verify checksum over the signed fields only
      const payload = {
        name: b.name, time, kills: entry.k, gold: entry.g, lv: entry.lv,
        stageId: b.stageId, grade: entry.gr, endless: !!b.endless, daily: !!b.daily,
        win: !!b.win, day
      };
      if ((await lbSig(payload)) !== b.sig) return jsonRes({ ok: false, error: 'sig' }, 403);
      if (time < 30 || time > 86400) return jsonRes({ ok: false, error: 'range' }, 400);

      const key = 'b:' + scope;
      const raw = await env.LB.get(key);
      const rows = raw ? JSON.parse(raw) : [];
      rows.push(entry);
      rows.sort((a, z) => z.t - a.t || z.k - a.k);
      await env.LB.put(key, JSON.stringify(rows.slice(0, 100)));
      return jsonRes({ ok: true, rank: rows.findIndex(r => r === entry) + 1 });
    }

    return jsonRes({ ok: false, error: 'route' }, 404);
  }
};