/**
 * mirror-bridge.mjs — 独立镜像桥（不依赖 DSH 插件重启）
 *
 * 为什么不走插件：桌面壳（DSH Desktop）的 HTTP 网关对未认证请求一律 403，浮窗是独立进程拿不到
 * cookie；而插件要重启 DSH 才会加载新版。所以这里直接读宿主自己的落盘数据：
 *
 *   %DSH_HOME%/storages/session_projcache.json   ← 每个会话的投影：标题 / 轮步 / 令牌 / 上下文压力
 *   %DSH_HOME%/sessions/<proj>/<sid>/session.jsonl.zstd ← 会话事件流（多帧 zstd）→ 消息行
 *
 * 产物：%DSH_HOME%/float-window/snapshot.json（与插件写的同一份 schema），浮窗每秒读它渲染。
 * 只有当插件没在写（mtime 超过 3s）时才写，避免两边打架。
 *
 * 用法：node tools/mirror-bridge.mjs [--home <DSH_HOME>] [--interval 1200] [--once]
 */
import fs from 'node:fs'
import path from 'node:path'
import os from 'node:os'
import zlib from 'node:zlib'

const argv = process.argv.slice(2)
const arg = (name, def) => {
  const i = argv.indexOf(name)
  return i >= 0 && argv[i + 1] ? argv[i + 1] : def
}
const HOME = arg('--home', process.env.DSH_HOME || path.join(os.homedir(), '.dsh'))
const INTERVAL = Number(arg('--interval', '1200'))
const ONCE = argv.includes('--once')
const STATE_DIR = path.join(HOME, 'float-window')
const SNAPSHOT = path.join(STATE_DIR, 'snapshot.json')
const SNAPSHOT_BRIDGE = path.join(STATE_DIR, 'snapshot-bridge.json')
const WATCH = path.join(STATE_DIR, 'watch.json')

const log = (...a) => { if (!argv.includes('--quiet')) console.log('[bridge]', ...a) }

const ZSTD_MAGIC = Buffer.from([0x28, 0xb5, 0x2f, 0xfd])

/** DSH 往同一个 .zstd 文件追加多个帧，zstdDecompressSync 只吃第一帧 → 按魔数切开逐帧解 */
function decompressFrames(buf) {
  let out = ''
  let idx = buf.indexOf(ZSTD_MAGIC)
  while (idx !== -1) {
    const next = buf.indexOf(ZSTD_MAGIC, idx + 4)
    const end = next === -1 ? buf.length : next
    try { out += zlib.zstdDecompressSync(buf.subarray(idx, end)).toString('utf8') } catch { }
    idx = next
  }
  return out
}

function readJson(file) {
  try { return JSON.parse(fs.readFileSync(file, 'utf8')) } catch { return null }
}

function listSessionLogs() {
  const root = path.join(HOME, 'sessions')
  const out = []
  if (!fs.existsSync(root)) return out
  for (const proj of fs.readdirSync(root)) {
    const pdir = path.join(root, proj)
    let isDir = false
    try { isDir = fs.statSync(pdir).isDirectory() } catch { }
    if (!isDir) continue
    for (const sid of fs.readdirSync(pdir)) {
      const f = path.join(pdir, sid, 'session.jsonl.zstd')
      try { out.push({ file: f, sid, mtime: fs.statSync(f).mtimeMs }) } catch { }
    }
  }
  return out.sort((a, b) => b.mtime - a.mtime)
}

function textOf(content) {
  if (typeof content === 'string') return content
  if (Array.isArray(content)) return content.map((c) => (typeof c === 'string' ? c : (c?.text ?? ''))).join('')
  return ''
}
const clip = (s, n = 4000) => (s.length > n ? s.slice(0, n) + '…' : s)

/** 事件流 → 浮窗消息行 + 实时指标（轮/步精确；token 用字符估算，标 ≈） */
function rowsFromLog(text) {
  const rows = []
  const titles = new Map()
  let turns = 0
  let steps = 0
  let outChars = 0
  let userChars = 0
  let contextWindow = null
  let streamStart = 0
  let streamChars = 0
  let lastChunkAt = 0
  const est = (chars) => Math.round(chars / 3.2) // 中英混排的粗略 token 估算

  for (const line of text.split('\n')) {
    if (!line) continue
    let e
    try { e = JSON.parse(line) } catch { continue }
    const type = String(e?.type || '')
    const d = e?.data || e || {}
    const t = e?.time || 0
    if (type === 'turn/start') turns++
    else if (type === 'step/start') steps++
    else if (type === 'request/context' && d.contextWindow) contextWindow = d.contextWindow
    else if (type === 'session/title' && d.title) titles.set('title', String(d.title))
    else if (type === 'user/message') {
      if (d.source?.kind && d.source.kind !== 'user') continue
      const s = textOf(d.content)
      if (s) { userChars += s.length; rows.push({ role: 'user', text: clip(s) }) }
    } else if (type === 'assistant/message') {
      const s = textOf(d.content ?? d.message?.content)
      if (s) { outChars += s.length; rows.push({ role: 'assistant', text: clip(s) }) }
    } else if (type === 'assistant/chunk') {
      const c = d.chunk || {}
      const kind = String(c.type || '')
      const piece = c.text ?? c.delta ?? (kind.includes('text') ? c.content : '')
      if (piece) {
        const now = t || Date.now()
        if (!streamStart || now - lastChunkAt > 8000) { streamStart = now; streamChars = 0 }
        lastChunkAt = now
        streamChars += String(piece).length
        outChars += String(piece).length
        const last = rows[rows.length - 1]
        if (last && last.role === 'assistant' && last.streaming) last.text += piece
        else rows.push({ role: 'assistant', text: String(piece), streaming: true })
      } else if (kind === 'finish' && c.reason?.kind === 'error') {
        rows.push({ role: 'assistant', text: '⚠️ ' + String(c.reason.failure?.message || c.reason.failure || 'error').slice(0, 300) })
      }
    } else if (type === 'tool/call') {
      rows.push({ role: 'tool', text: `${d.name || 'tool'}(${JSON.stringify(d.args ?? '').slice(0, 120)})` })
    }
  }
  for (const r of rows) delete r.streaming
  const streaming = lastChunkAt && Date.now() - lastChunkAt < 8000
  const tps = streaming && streamStart ? est(streamChars) / Math.max(0.5, (lastChunkAt - streamStart) / 1000) : null
  return {
    rows, titles, turns, steps, streaming,
    metrics: {
      turns,
      steps,
      tps,
      tokens: outChars ? est(outChars + userChars) : null,
      cacheHit: null,
      contextUsed: contextWindow ? Math.min(1, est(userChars + outChars) / contextWindow) : null,
    },
  }
}

function buildSnapshot() {
  const cache = readJson(path.join(HOME, 'storages', 'session_projcache.json'))
  const table = cache?.tables?.sessions || {}
  const watch = readJson(WATCH)
  const logs = listSessionLogs()

  // 会话清单：以**日志**为主（实时 mtime），投影缓存只用于补标题/历史统计
  const entries = []
  for (const l of logs) {
    const rows = table[l.sid]?.rows || table[l.sid.replace(/^session-/, '')]?.rows || {}
    const stats = rows.sessionStats?.val || {}
    entries.push({
      id: l.sid,
      title: rows.title?.val || null,
      cacheTurns: stats.turns ?? null,
      cacheSteps: stats.steps ?? null,
      mtime: l.mtime,
      log: l,
    })
  }

  // 当前会话：watch.json 指定优先，否则"日志最新"（真正在跑的那个）
  let active = null
  if (watch?.sessionId) active = entries.find((e) => e.id === watch.sessionId || e.id.replace(/^session-/, '') === watch.sessionId) || null
  if (!active) active = entries.sort((a, b) => b.mtime - a.mtime)[0] || null
  if (!active) return null

  let rows = []
  let title = active.title
  let metrics = { turns: active.cacheTurns, steps: active.cacheSteps, tps: null, tokens: null, cacheHit: null, contextUsed: null }
  let streaming = false
  try {
    const parsed = rowsFromLog(decompressFrames(fs.readFileSync(active.log.file)))
    rows = parsed.rows.slice(-40)
    title = title || parsed.titles.get('title') || null
    streaming = parsed.streaming
    // 轮/步取实时计数（缓存的那份是周期性落盘的，可能滞后）
    metrics = {
      ...parsed.metrics,
      turns: Math.max(parsed.metrics.turns, active.cacheTurns || 0),
      steps: Math.max(parsed.metrics.steps, active.cacheSteps || 0),
    }
  } catch (e) { log('log read failed:', String(e?.message || e)) }

  return {
    ok: true,
    at: Date.now(),
    source: 'mirror-bridge',
    approx: true, // token/上下文是字符估算，界面上会带 ≈
    streaming,
    sessionId: active.id,
    pinned: watch?.sessionId || null,
    title,
    messages: rows,
    metrics,
    sessions: entries.slice(0, 20).map((e) => ({ id: e.id, title: e.title, turns: e.cacheTurns || 0, steps: e.cacheSteps || 0, messages: 0, active: e.id === active.id })),
  }
}

function writeSnapshot() {
  try {
    const snap = buildSnapshot()
    if (!snap) return
    fs.mkdirSync(STATE_DIR, { recursive: true })
    // 兜底文件总是写：插件缺的字段（token/上下文估算、标题）由浮窗用它补齐
    fs.writeFileSync(SNAPSHOT_BRIDGE, JSON.stringify(snap))
    // 插件在写就不抢 snapshot.json：mtime 3 秒内视为它的
    try {
      const st = fs.statSync(SNAPSHOT)
      if (Date.now() - st.mtimeMs < 3000 && readJson(SNAPSHOT)?.source !== 'mirror-bridge') return
    } catch { }
    fs.writeFileSync(SNAPSHOT, JSON.stringify(snap))
    log(`snapshot: ${snap.sessionId} "${(snap.title || '').slice(0, 24)}" turns=${snap.metrics.turns} steps=${snap.metrics.steps} rows=${snap.messages.length} ctx=${snap.metrics.contextUsed == null ? '-' : Math.round(snap.metrics.contextUsed * 100) + '%'}`)
  } catch (e) { log('write failed:', String(e?.message || e)) }
}

writeSnapshot()
if (!ONCE) setInterval(writeSnapshot, INTERVAL)