#!/usr/bin/env python3
"""Assemble an Alpine-derived, shell-free runtime from an explicit ELF allowlist."""
import os
from pathlib import Path
import shutil
import subprocess
import sys

root = Path(sys.argv[1])
root.mkdir(parents=True, exist_ok=True)

copied = set()

def copy(source):
    source = Path(os.path.normpath(source))
    if source in copied:
        return
    copied.add(source)
    target = root / str(source).lstrip('/')
    target.parent.mkdir(parents=True, exist_ok=True)
    if source.is_symlink():
        link = os.readlink(source)
        if not target.is_symlink():
            target.symlink_to(link)
        # Preserve every hop, not just the final file in a multi-link chain.
        copy(link if os.path.isabs(link) else source.parent / link)
    elif source.is_dir():
        target.mkdir(exist_ok=True)
        for child in source.iterdir():
            copy(child)
    else:
        shutil.copy2(source, target)

for executable in sys.argv[2:]:
    result = subprocess.run(['lddtreepax', '-l', executable], check=True, text=True, capture_output=True)
    paths = result.stdout.splitlines()
    if not paths or any(not p.startswith('/') or not Path(p).exists() for p in paths):
        raise SystemExit(f'Unresolved runtime dependency for {executable}: {result.stdout}')
    copy(executable)
    for path in paths:
        copy(path)

# musl uses this file for nonstandard library directories (for example Lua).
for search_path in Path('/etc').glob('ld-musl-*.path'):
    copy(search_path)

for data in ['/etc/ssl/certs/ca-certificates.crt', '/etc/ssl/cert.pem',
             '/etc/ssl/openssl.cnf', '/usr/lib/ossl-modules', '/usr/share/zoneinfo',
             '/etc/terminfo', '/usr/share/terminfo', '/etc/services', '/etc/protocols',
             '/etc/alpine-release', '/etc/os-release']:
    if Path(data).exists():
        copy(data)
for directory in ['tmp', 'root', 'myconfig', 'home/nfs_download/rsession', 'server/db', 'config', 'etc']:
    (root / directory).mkdir(parents=True, exist_ok=True)
os.chmod(root / 'tmp', 0o1777)
(root / 'root/.rtorrent.rc').touch()
(root / 'etc/passwd').write_text('root:x:0:0:root:/root:/sbin/nologin\n')
(root / 'etc/group').write_text('root:x:0:\n')
for forbidden in ['bin/sh', 'bin/bash', 'bin/busybox', 'sbin/apk', 'usr/bin/apk',
                  'usr/bin/npm', 'usr/local/bin/npm', 'usr/bin/python3']:
    assert not (root / forbidden).exists(), f'Unexpected runtime tool: {forbidden}'