'use strict';
// Per-session JSON-lines logger shared across all variants. Writes to
// rfid-daemon/diagnostics/run-<variant>-<YYYYMMDD-HHMMSS>.log so we can
// compare variants apples-to-apples after a session.

const fs = require('fs');
const path = require('path');

const pad2 = n => n.toString().padStart(2, '0');
function tsForFilename(d = new Date()) {
  return `${d.getFullYear()}${pad2(d.getMonth()+1)}${pad2(d.getDate())}-${pad2(d.getHours())}${pad2(d.getMinutes())}${pad2(d.getSeconds())}`;
}

function createLogger(variant, diagDir) {
  fs.mkdirSync(diagDir, { recursive: true });
  const logPath = path.join(diagDir, `run-${variant}-${tsForFilename()}.log`);
  const stream = fs.createWriteStream(logPath, { flags: 'a' });

  const counters = {
    write_ok: 0, write_failed: 0,
    read_ok: 0, read_failed: 0,
    inventory_ok: 0, inventory_failed: 0,
    timeout: 0,
    keepalive_sent: 0, preflight_run: 0,
    recover_attempted: 0,
    lockups: 0,
  };
  let lastSuccessAt = null;
  let inLockupSince = null;
  const startedAt = Date.now();

  function writeLine(obj) {
    stream.write(JSON.stringify(obj) + '\n');
  }

  function event(name, data = {}) {
    const obj = { ts: new Date().toISOString(), ev: name, ...data };
    writeLine(obj);

    if (name in counters) counters[name]++;

    const isSuccess = (name === 'write_ok' || name === 'read_ok' || name === 'inventory_ok');
    if (isSuccess) {
      lastSuccessAt = Date.now();
      if (inLockupSince) {
        writeLine({ ts: obj.ts, ev: 'recovered', afterMs: Date.now() - inLockupSince });
        inLockupSince = null;
      }
    }
    if (name === 'timeout' && !inLockupSince) {
      inLockupSince = Date.now();
      counters.lockups++;
      writeLine({ ts: obj.ts, ev: 'lockup_detected', sinceLastSuccessMs: lastSuccessAt ? Date.now() - lastSuccessAt : null });
    }
  }

  function summary() {
    return {
      variant,
      runtimeMs: Date.now() - startedAt,
      counters: { ...counters },
      lastSuccessAgoMs: lastSuccessAt ? Date.now() - lastSuccessAt : null,
      currentlyLocked: !!inLockupSince,
    };
  }

  function close() {
    writeLine({ ts: new Date().toISOString(), ev: 'end', ...summary() });
    stream.end();
  }

  return { event, summary, close, logPath };
}

module.exports = { createLogger };