/**
 * 会话时序分析器（只输出时间戳/事件类型/时延，不输出任何消息正文）
 * 用法：node analyze-session.mjs <session.jsonl.zstd>
 */
import { readFileSync } from 'node:fs'
import { zstdDecompressSync } from 'node:zlib'

const file = process.argv[2]
const raw = readFileSync(file)

// 可能是多帧拼接：按 zstd magic 切分逐帧解压
const MAGIC = Buffer.from([0x28, 0xb5, 0x2f, 0xfd])
const offsets = []
for (let i = 0; i + 4 <= raw.length; i++) {
  if (raw.compare(MAGIC, 0, 4, i, i + 4) === 0) offsets.push(i)
}
let text = ''
const frames = offsets.length > 0 ? offsets : [0]
for (let f = 0; f < frames.length; f++) {
  const start = frames[f]
  const end = f + 1 < frames.length ? frames[f + 1] : raw.length
  try {
    text += zstdDecompressSync(raw.subarray(start, end)).toString('utf8')
  } catch (e) {
    // 单帧整体解压兜底
  }
}
if (text === '') {
  try {
    text = zstdDecompressSync(raw).toString('utf8')
  } catch (e) {
    console.log('decompress failed:', e.message)
    process.exit(1)
  }
}

const lines = text.split('\n').filter((l) => l.trim() !== '')
console.log(`帧数=${frames.length} 行数=${lines.length} 解压字节=${text.length}`)

const pick = (obj, names, depth = 0) => {
  if (obj === null || typeof obj !== 'object' || depth > 3) return undefined
  for (const n of names) if (typeof obj[n] !== 'undefined') return obj[n]
  for (const v of Object.values(obj)) {
    const hit = pick(v, names, depth + 1)
    if (hit !== undefined) return hit
  }
  return undefined
}
const TS_KEYS = ['ts', 'time', 'timestamp', 'at', 'createdAt', 'created_at', 'mtime', 'date']
const KIND_KEYS = ['kind', 'type', 'event', 'role', 'name', 'tag']

const events = []
const kinds = new Map()
for (const line of lines) {
  let o
  try {
    o = JSON.parse(line)
  } catch {
    continue
  }
  const ts = pick(o, TS_KEYS)
  const kind = pick(o, KIND_KEYS)
  const k = typeof kind === 'string' ? kind : JSON.stringify(kind ?? '?')
  kinds.set(k, (kinds.get(k) ?? 0) + 1)
  const t = typeof ts === 'number' ? (ts < 1e12 ? ts * 1000 : ts) : typeof ts === 'string' ? Date.parse(ts) : NaN
  events.push({ t: Number.isNaN(t) ? undefined : t, k })
}

console.log('\n== 事件类型分布（TOP 20）==')
;[...kinds.entries()].sort((a, b) => b[1] - a[1]).slice(0, 20).forEach(([k, c]) => console.log(`  ${c}\t${k}`))

const withTs = events.filter((e) => e.t !== undefined)
console.log(`\n带时间戳事件: ${withTs.length}/${events.length}`)
if (withTs.length > 1) {
  const span = (withTs[withTs.length - 1].t - withTs[0].t) / 1000
  console.log(`时间跨度: ${span.toFixed(1)}s（约 ${(span / 60).toFixed(1)} 分钟）`)

  const gaps = []
  for (let i = 1; i < withTs.length; i++) gaps.push({ d: (withTs[i].t - withTs[i - 1].t) / 1000, a: withTs[i - 1].k, b: withTs[i].k })

  console.log('\n== 最大间隔 TOP 12（秒 | 前事件 → 后事件）==')
  gaps.sort((x, y) => y.d - x.d).slice(0, 12).forEach((g) => console.log(`  ${g.d.toFixed(1)}\t${g.a}  →  ${g.b}`))

  const over5 = gaps.filter((g) => g.d > 5)
  console.log(`\n>5s 的空档数: ${over5.length}；>30s: ${gaps.filter((g) => g.d > 30).length}；>60s: ${gaps.filter((g) => g.d > 60).length}`)

  // 会话首尾时间（便于与外部日志对齐）
  const fmt = (ms) => new Date(ms).toISOString().replace('T', ' ').slice(0, 19)
  console.log(`\n首事件: ${fmt(withTs[0].t)}  末事件: ${fmt(withTs[withTs.length - 1].t)}`)
}