法令改正チェックを定期実行する：e-Gov法令API law_revisions の差分検知とClaude Code連携

{
  "law_ids": ["322AC0000000049", "331AC0000000120", "417AC0000000086"]
}

// e-Gov 法令API v2 の law_revisions を定期取得し、前回スナップショットとの差分を報告する
// 使い方: node watch-revisions.mjs            (watch.json の law_ids を監視)
// 終了コード: 0 = 変化なし / 2 = 変化あり(diff.json を出力) / 1 = エラー
import { readFile, writeFile } from 'node:fs/promises';

const BASE = 'https://laws.e-gov.go.jp/api/2';
const CONFIG = new URL('./watch.json', import.meta.url);
const STATE = new URL('./state.json', import.meta.url);
const DIFF = new URL('./diff.json', import.meta.url);

const config = JSON.parse(await readFile(CONFIG, 'utf8'));
let state = {};
try { state = JSON.parse(await readFile(STATE, 'utf8')); } catch { /* 初回 */ }

const changes = [];
const errors = [];
const next = {};

for (const lawId of config.law_ids) {
  const res = await fetch(`${BASE}/law_revisions/${lawId}`, {
    headers: { Accept: 'application/json' },
    signal: AbortSignal.timeout(30_000),
  });
  if (!res.ok) {
    // 存在しない ID は 404 {"code":"404001"} で返る。前回の状態を保持して次へ
    errors.push({ law_id: lawId, status: res.status, body: (await res.text()).slice(0, 120) });
    if (state[lawId]) next[lawId] = state[lawId];
    continue;
  }
  const data = await res.json();

  // 比較に使う項目だけ残す(本文は取らない)
  const revisions = data.revisions.map((r) => ({
    law_revision_id: r.law_revision_id,
    law_title: r.law_title,
    amendment_enforcement_date: r.amendment_enforcement_date,
    amendment_law_num: r.amendment_law_num,
    current_revision_status: r.current_revision_status,
    updated: r.updated,
  }));
  next[lawId] = { law_num: data.law_info.law_num, revisions };

  const prev = state[lawId];
  if (!prev) { changes.push({ law_id: lawId, kind: 'initial', title: revisions[0]?.law_title, count: revisions.length }); continue; }

  const prevById = new Map(prev.revisions.map((r) => [r.law_revision_id, r]));
  for (const r of revisions) {
    const p = prevById.get(r.law_revision_id);
    if (!p) { changes.push({ law_id: lawId, kind: 'new_revision', ...r }); continue; }
    if (p.current_revision_status !== r.current_revision_status)
      changes.push({ law_id: lawId, kind: 'status_changed', law_revision_id: r.law_revision_id, from: p.current_revision_status, to: r.current_revision_status, title: r.law_title });
    else if (p.updated !== r.updated)
      changes.push({ law_id: lawId, kind: 'updated', law_revision_id: r.law_revision_id, from: p.updated, to: r.updated, title: r.law_title });
  }
  for (const p of prev.revisions) if (!revisions.some((r) => r.law_revision_id === p.law_revision_id))
    changes.push({ law_id: lawId, kind: 'removed', law_revision_id: p.law_revision_id });
}

await writeFile(STATE, JSON.stringify(next, null, 2), 'utf8');
const checkedAt = new Date().toISOString();
const real = changes.filter((c) => c.kind !== 'initial');

for (const e of errors) console.error(`[error] ${e.law_id} HTTP ${e.status} ${e.body}`);
if (changes.length === 0) {
  console.log(`${checkedAt} 変化なし (${config.law_ids.length - errors.length} 法令)`);
} else {
  await writeFile(DIFF, JSON.stringify({ checked_at: checkedAt, changes }, null, 2), 'utf8');
  for (const c of changes) console.log(`[${c.kind}] ${c.law_id} ${c.law_revision_id ?? ''} ${c.title ?? ''} ${c.from ? `${c.from} -> ${c.to}` : ''}`.trim());
}
process.exitCode = errors.length > 0 ? 1 : real.length > 0 ? 2 : 0;

### 初回（state.json なし）
[initial] 322AC0000000049  労働基準法
[initial] 331AC0000000120  製造委託等に係る中小受託事業者に対する代金の支払の遅延等の防止に関する法律
[initial] 417AC0000000086  会社法
exit=0

### 2回目（変化なし）
2026-09-14T04:37:09.167Z 変化なし (3 法令)
exit=0

### state.json から最新履歴を1件消して再実行（改正公布を模擬）
[new_revision] 322AC0000000049 322AC0000000049_20281223_508AC0000000046
exit=2

### 存在しないIDを watch.json に混ぜる
[error] 999AC9999999999 HTTP 404 {"code":"404001","message":"取得結果が０件です。"}
2026-09-14T04:37:10.961Z 変化なし (1 法令)
exit=1

{
  "checked_at": "2026-09-14T04:37:09.943Z",
  "changes": [
    {
      "law_id": "322AC0000000049",
      "kind": "new_revision",
      "law_revision_id": "322AC0000000049_20281223_508AC0000000046",
      "law_title": "労働基準法",
      "amendment_enforcement_date": "2028-12-23",
      "amendment_law_num": "令和八年法律第四十六号",
      "current_revision_status": "UnEnforced",
      "updated": "2026-07-23T15:54:56+09:00"
    }
  ]
}

#!/usr/bin/env bash
# run-watch.sh : 差分検知 → 変化があれば claude -p で要約
cd "$(dirname "$0")"
node watch-revisions.mjs >> watch.log 2>&1
code=$?
if [ "$code" -eq 2 ]; then
  claude --bare -p "以下は e-Gov 法令API の law_revisions の差分（JSON）です。法令ごとに、何が起きたか（新しい版の追加 / 施行状態の変化 / 更新日時のみ）と施行日を日本語で3行以内に要約してください。差分に含まれない情報は書かないでください。" \
    --output-format json < diff.json > summary.json
  jq -r '.result' summary.json >> watch.log
fi
exit "$code"

# Linux / macOS: crontab -e
0 7 * * * cd /opt/egov-watch && bash run-watch.sh