#!/usr/bin/env node
/**
 * PreCompact Hook - 上下文压缩前自动保存会话状态
 * 将当前任务摘要写入 ~/.claude/session-state/handoff.json
 */
const fs = require('fs');
const path = require('path');

const CLAUDE_ROOT = require('./lib/root.js');
const readStdin = require('./lib/read-stdin.js');

const SESSION_STATE_DIR = path.join(CLAUDE_ROOT, 'session-state');
const HANDOFF_PATH = path.join(SESSION_STATE_DIR, 'handoff.json');

(async () => {
  try {
    let hookData = {};
    try { hookData = await readStdin(); } catch (_) {}

    // 确保目录存在
    if (!fs.existsSync(SESSION_STATE_DIR)) {
      fs.mkdirSync(SESSION_STATE_DIR, { recursive: true });
    }

    // TOOL_OUTPUT_TIER_V1 - 扫描 transcript 提取大工具输出分级摘要
    const toolOutputTiers = scanToolOutputTiers(hookData.transcript_path);

    // 构造 handoff 数据
    const handoff = {
      timestamp: new Date().toISOString(),
      session_id: hookData.session_id || `session-${Date.now()}`,
      context_hint: '会话因上下文压缩中断，以下是压缩前的状态摘要',
      conversation_summary: hookData.transcript_summary || '(由 PreCompact hook 自动捕获)',
      tool_call_count: hookData.tool_call_count || 'unknown',
      working_directory: process.cwd(),
      tool_output_tiers: toolOutputTiers,
      note: '此文件由 pre-compact-handoff.js 自动生成，SessionStart 时自动读取并注入恢复上下文'
    };

    const _tmpHandoff = HANDOFF_PATH + '.tmp.' + process.pid; // [PATCH-X13-HANDOFF-ATOMIC]
    fs.writeFileSync(_tmpHandoff, JSON.stringify(handoff, null, 2), 'utf8');
    fs.renameSync(_tmpHandoff, HANDOFF_PATH);

    // [PATCH-P2-HANDOFF-CLEANUP] 清理过期 handoff 时间戳文件, 保留最新 5 个
    try {
      const files = fs.readdirSync(SESSION_STATE_DIR)
        .filter(f => /^handoff-\d+\.json$/.test(f))
        .map(f => ({ name: f, time: parseInt(f.match(/\d+/)[0], 10) }))
        .sort((a, b) => b.time - a.time);
      const toDelete = files.slice(5);
      for (const f of toDelete) {
        try { fs.unlinkSync(path.join(SESSION_STATE_DIR, f.name)); } catch {}
      }
    } catch {}


    // 重置当前 session 的 heartbeat 计数器 (compact = 新起点) // [PATCH-X03-HANDOFF-RESET]
    const heartbeatPath = path.join(CLAUDE_ROOT, 'debug', 'session-heartbeat.json');
    if (fs.existsSync(heartbeatPath)) {
      try {
        const hbAll = JSON.parse(fs.readFileSync(heartbeatPath, 'utf8'));
        const hbSid = hookData.session_id || 'default';
        if (hbAll[hbSid]) {
          hbAll[hbSid] = { count: 0, lastActivity: Date.now(), notified: [] };
          const _tmpPch = heartbeatPath + '.tmp.' + process.pid; // [PATCH-X08-ATOMIC-WRITE]
          fs.writeFileSync(_tmpPch, JSON.stringify(hbAll), 'utf8');
          fs.renameSync(_tmpPch, heartbeatPath);
        }
      } catch { /* 损坏则跳过, heartbeat 超时会自然重置 */ }
    }

    // TSE_V2_RETENTION: 智能保留指令
    let _retMsg = '[PRE_COMPACT] 上下文即将压缩。handoff.json 已写入。';
    try {
      const _ret = require('./lib/tse-retention-extractor.js').extract(hookData.transcript_path);
      if (_ret) _retMsg += '\n' + _ret;
    } catch {}
    _retMsg += '\n请保留关键上下文: 当前任务目标、活跃文件路径、关键决策和待完成步骤。';
    console.log(JSON.stringify({
      continue: true,
      suppressOutput: false,
      systemMessage: _retMsg
    }));
  } catch {
    // fail-open
    console.log(JSON.stringify({ continue: true, suppressOutput: true }));
  }
  process.exit(0);
})();


// === TOOL_OUTPUT_TIER_V1 === // [PATCH-X04-STREAM-SCAN]
// 扫描 transcript JSONL, 按工具类型分级保留大输出, 输出 TOP-10 摘要
// X04: 流式逐行扫描, 避免大文件 OOM
function scanToolOutputTiers(transcriptPath) {
  if (!transcriptPath || !fs.existsSync(transcriptPath)) {
    return { applied: false, reason: 'no transcript_path' };
  }
  try {
    const stat = fs.statSync(transcriptPath);
    const MAX_FILE = 50 * 1024 * 1024; // 50MB 硬上限
    if (stat.size > MAX_FILE) {
      return { applied: false, reason: 'transcript_too_large: ' + (stat.size / 1024 / 1024).toFixed(1) + 'MB (limit 50MB)' };
    }

    const items = [];
    const MAX_ITEM_BYTES = 5 * 1024 * 1024;

    // 20MB 以下: 同步读取 (性能优先)
    // 20MB 以上: 逐行流式读取 (内存安全)
    const STREAM_THRESHOLD = 20 * 1024 * 1024;

    if (stat.size <= STREAM_THRESHOLD) {
      const raw = fs.readFileSync(transcriptPath, 'utf8');
      const lines = raw.split('\n').filter(Boolean);
      for (const line of lines) {
        processLine(line, items, MAX_ITEM_BYTES);
      }
    } else {
      // 流式: 逐块读取, 按换行切割
      const fd = fs.openSync(transcriptPath, 'r');
      const CHUNK = 4 * 1024 * 1024; // 4MB 块
      const buf = Buffer.alloc(CHUNK);
      let remainder = '';
      let pos = 0;
      while (pos < stat.size) {
        const n = fs.readSync(fd, buf, 0, CHUNK, pos);
        if (n <= 0) break;
        const chunk = remainder + buf.toString('utf8', 0, n);
        const parts = chunk.split('\n');
        remainder = parts.pop() || '';
        for (const line of parts) {
          if (!line) continue;
          processLine(line, items, MAX_ITEM_BYTES);
        }
        pos += n;
      }
      if (remainder) processLine(remainder, items, MAX_ITEM_BYTES);
      fs.closeSync(fd);
    }

    items.sort((a, b) => b.size - a.size);
    const top = items.slice(0, 10).map(it => tierize(it));
    const totalBytes = items.reduce((s, it) => s + it.size, 0);
    return {
      applied: true,
      total_tool_results_scanned: items.length,
      total_bytes: totalBytes,
      top_offenders: top,
      mode: stat.size > STREAM_THRESHOLD ? 'stream' : 'sync'
    };
  } catch (e) {
    return { applied: false, reason: 'scan_error: ' + (e.message || e) };
  }
}

function processLine(line, items, MAX_ITEM_BYTES) {
  let obj;
  try { obj = JSON.parse(line); } catch { return; }
  const content = obj?.message?.content || obj?.content;
  if (!Array.isArray(content)) return;
  for (const part of content) {
    if (part?.type !== 'tool_result') continue;
    const text = typeof part.content === 'string'
      ? part.content
      : Array.isArray(part.content) ? part.content.map(c => c?.text || '').join('') : '';
    const size = Buffer.byteLength(text, 'utf8');
    if (size < 500) continue; // [PATCH-X06-CONTINUE]
    const safeText = size > MAX_ITEM_BYTES ? text.slice(0, MAX_ITEM_BYTES) : text;
    items.push({ size, text: safeText, tool_use_id: part.tool_use_id, capped: size > MAX_ITEM_BYTES });
  }
}

function tierize(item) {
  const { size, text, tool_use_id } = item;
  // 启发式工具类型判定 (transcript 不直接含工具名, 用文本特征)
  let kind = 'other';
  if (/^(File created successfully|Wrote \d+ lines|The file .* has been (created|updated))/m.test(text)) kind = 'write';
  else if (/^\s*\d+→/m.test(text) || text.startsWith('     1\t')) kind = 'read';
  else if (/<tool_use_error>|^bash:|stderr:/m.test(text) || /\$ /m.test(text.slice(0, 100))) kind = 'bash';
  else if (/^(Found \d+ files?|^[a-zA-Z]:\\.*\.(ts|js|md|json))/m.test(text)) kind = 'glob_grep';
  else if (size > 3000 && text.includes('agent')) kind = 'agent';

  let summary;
  switch (kind) {
    case 'write':
      summary = text.split('\n').slice(0, 2).join(' | ').slice(0, 200);
      break;
    case 'read':
      summary = '[Read] ' + text.slice(0, 200) + ' ... [+' + (size - 200) + ' bytes]';
      break;
    case 'bash':
      summary = text.slice(0, 1500) + '\n... [truncated ' + Math.max(0, size - 2000) + ' bytes] ...\n' + text.slice(-500);
      break;
    case 'agent':
      summary = text.slice(0, 1000) + '\n... [Agent 完整结果已截断 ' + (size - 1000) + ' bytes]';
      break;
    case 'glob_grep':
      summary = '[Glob/Grep] ' + text.split('\n').slice(0, 8).join(' | ').slice(0, 400);
      break;
    default:
      summary = text.slice(0, 2000) + '\n... [+' + Math.max(0, size - 2500) + ' bytes] ...\n' + text.slice(-500);
  }
  return { tool_use_id, kind, original_bytes: size, summary };
}