ドキュメントのないコードを仕様書に起こす前に、読ませる順番を fan-in で決めておく

#!/usr/bin/env python3
"""reading_order.py — 既存コードの「読ませる順番」を fan-in とエントリポイントで出す。標準ライブラリのみ。"""
import os, re, sys, json, collections
root = os.path.abspath(sys.argv[1]); top_n = int(sys.argv[2]) if len(sys.argv) > 2 else 12
SKIP = {"node_modules", ".git", ".next", "dist", "build", "public", "content", "__pycache__"}
EXT = (".ts", ".tsx", ".js", ".mjs", ".jsx")
ENTRY = re.compile(r"(^|/)(page|route|layout|middleware|proxy)\.(t|j)sx?$")
IMP = re.compile(r"""(?:from|import)\s*\(?\s*['"]([^'"]+)['"]""")
files, size = [], {}
for d, ds, fs in os.walk(root):
    ds[:] = [x for x in ds if x not in SKIP]
    for f in fs:
        if f.endswith(EXT):
            p = os.path.relpath(os.path.join(d, f), root); files.append(p); size[p] = os.path.getsize(os.path.join(root, p))
fset = set(files)
def resolve(src, spec):
    if spec.startswith("@/"): base = os.path.join("src", spec[2:])
    elif spec.startswith("."): base = os.path.normpath(os.path.join(os.path.dirname(src), spec))
    else: return None
    for c in [base] + [base + e for e in EXT] + [os.path.join(base, "index" + e) for e in EXT]:
        if c in fset: return c
fan = collections.Counter()
for p in files:
    try: t = open(os.path.join(root, p), encoding="utf-8").read()
    except Exception: continue
    for m in set(IMP.findall(t)):
        r = resolve(p, m)
        if r and r != p: fan[r] += 1
entries = [p for p in files if ENTRY.search(p)]
total = sum(size.values())
ranked = [p for p, _ in fan.most_common(top_n)]
pick = list(dict.fromkeys(ranked + entries[:top_n]))
pb = sum(size[p] for p in pick)
print(json.dumps({"files": len(files), "total_bytes": total, "entries": len(entries),
  "picked": len(pick), "picked_bytes": pb, "ratio_pct": round(pb * 100 / total, 1)}, ensure_ascii=False))
for p in ranked: print(f"fan-in {fan[p]:>3}  {size[p]:>6}B  {p}")