"""One-shot Linux Pi-child fault. No environment reads; never targets a worker.

The caller is the nonce-bound remote observer. Its already admitted lease and
run root are rechecked here, then pidfd pins the exact child across PID reuse.
This helper does not relax provider admission or manufacture runtime events.
"""
import base64
import hashlib
import json
import os
from pathlib import Path
import re
import signal
import stat
import sys

PACK = '/opt/paperclip-runner/provider-pack'
ENTRY = 'node_modules/@earendil-works/pi-coding-agent/dist/cli.js'
NODE = 'node/bin/node'
EXTENSION = 'extensions/paperclip.js'
GUARD = '.paperclip-native-module-guard.cjs'


def require(value, code):
    if not value:
        raise RuntimeError('pi_provider_fault:' + code)


def proc(pid, boot):
    raw = Path(f'/proc/{pid}/stat').read_text()
    require(raw.startswith(f'{pid} ('), 'stat_pid')
    fields = raw.rsplit(') ', 1)[1].split()
    require(fields[0] != 'Z', 'dead_process')
    return {'pid': pid, 'ppid': int(fields[1]), 'startTicks': fields[19], 'bootId': boot}


def argv(pid):
    raw = Path(f'/proc/{pid}/cmdline').read_bytes()
    require(0 < len(raw) <= 32768, 'argv_bound')
    return raw.decode().rstrip('\0').split('\0')


def flag(args, name):
    require(args.count(name) == 1 and args.index(name) + 1 < len(args), 'flag_' + name)
    return args[args.index(name) + 1]


def checked_file(path, maximum, sealed=False):
    require(os.path.realpath(path) == path, 'file_realpath')
    fd = os.open(path, os.O_RDONLY | os.O_NOFOLLOW)
    try:
        before = os.fstat(fd)
        require(stat.S_ISREG(before.st_mode) and before.st_nlink == 1 and 0 < before.st_size <= maximum, 'file_shape')
        if sealed:
            require(before.st_mode & 0o222 == 0, 'file_writable')
        chunks = []
        while True:
            chunk = os.read(fd, min(1024 * 1024, maximum + 1))
            if not chunk:
                break
            chunks.append(chunk)
            require(sum(map(len, chunks)) <= maximum, 'file_bound')
        after, named = os.fstat(fd), os.lstat(path)
        identity = lambda s: (s.st_dev, s.st_ino, s.st_size, s.st_mtime_ns, s.st_ctime_ns, s.st_mode, s.st_nlink)
        require(identity(before) == identity(after) == identity(named), 'file_changed')
        return b''.join(chunks), (before.st_dev, before.st_ino)
    finally:
        os.close(fd)


def digest(data):
    return hashlib.sha256(data).hexdigest()


def checked_runner_executable(path):
    # Production stages a verified preinstalled runner with ln -sfn. Admit
    # that named link only while its identity and resolved regular file remain
    # stable; inspect still requires both the pinned hash and /proc/exe inode.
    before = os.lstat(path)
    require(stat.S_ISREG(before.st_mode) or stat.S_ISLNK(before.st_mode), 'runner_file_shape')
    resolved = os.path.realpath(path)
    content, inode = checked_file(resolved, 256 * 1024 * 1024)
    after = os.lstat(path)
    identity = lambda s: (s.st_dev, s.st_ino, s.st_mode, s.st_mtime_ns, s.st_ctime_ns)
    require(identity(before) == identity(after) and os.path.realpath(path) == resolved, 'runner_link_changed')
    return content, inode


def parse_closure_metadata(content, expected_pin):
    # Match production parseNativeAcpxDistributionEntries: the profile pins
    # canonical entries, not the formatting or outer JSON file bytes.
    manifest = json.loads(content)
    entries = manifest.get('entries') if isinstance(manifest, dict) else None
    require(isinstance(entries, list) and 0 < len(entries) <= 30000, 'closure_inventory')
    normalized, previous, total = [], '', 0
    for entry in entries:
        require(isinstance(entry, dict) and set(entry) == {'path', 'sha256', 'size', 'executable'}, 'closure_entry_shape')
        path = entry['path']
        require(isinstance(path, str) and 0 < len(path) <= 4096 and not os.path.isabs(path)
                and not re.search(r'[\x00-\x1f\x7f\\]', path)
                and all(part not in ('', '.', '..') for part in path.split('/'))
                and path > previous and path != 'manifest.json' and not path.startswith('.paperclip-'), 'closure_entry_path')
        require(isinstance(entry['sha256'], str) and re.fullmatch(r'[a-f0-9]{64}', entry['sha256'])
                and type(entry['size']) is int and 0 <= entry['size'] <= 384 * 1024 * 1024
                and type(entry['executable']) is bool, 'closure_entry_metadata')
        total += entry['size']; require(total <= 1024 * 1024 * 1024, 'closure_tree_bound')
        previous = path
        normalized.append({key: entry[key] for key in ('path', 'sha256', 'size', 'executable')})
    canonical = json.dumps(normalized, separators=(',', ':'), ensure_ascii=False).encode('utf8')
    require(re.fullmatch(r'[a-f0-9]{64}', expected_pin) and digest(canonical) == expected_pin, 'closure_pin')
    return normalized


def inspect(config):
    require(set(config) == {'root', 'binding', 'runtimeEnvironmentLeaseId', 'runnerdSha256', 'closureSha256'}, 'config_keys')
    binding, expected = config['binding'], config['root']
    boot = Path('/proc/sys/kernel/random/boot_id').read_text().strip()
    require(re.fullmatch(r'[a-f0-9-]{36}', boot) and boot == expected['bootId'], 'boot_changed')
    root = proc(expected['pid'], boot)
    require(root == expected and os.getpgid(root['pid']) == root['pid'], 'root_changed')
    root_args = argv(root['pid'])
    runtime_root = binding['remoteCwd'] + '/.paperclip-runtime/paperclip-runner'
    runner = runtime_root + '/bin/paperclip-runnerd'
    require(root_args[0] == runner and flag(root_args, '--run-id') == binding['runId']
            and flag(root_args, '--environment-lease-id') == config['runtimeEnvironmentLeaseId']
            and flag(root_args, '--lifecycle-mode') == 'per_turn', 'root_binding')
    require(re.fullmatch(re.escape(runtime_root) + r'/sessions/[a-f0-9]{64}/runner', flag(root_args, '--state-dir')), 'root_session')
    runner_bytes, runner_inode = checked_runner_executable(runner)
    executable = os.stat(f'/proc/{root["pid"]}/exe')
    require((executable.st_dev, executable.st_ino) == runner_inode and 'sha256:' + digest(runner_bytes) == config['runnerdSha256'], 'runner_executable')
    closure_bytes, _ = checked_file(PACK + '/provider-assets/pi/linux-x64/native-closure.json', 4 * 1024 * 1024)
    admitted_entries = parse_closure_metadata(closure_bytes, config['closureSha256'])
    entries = {e['path']: e for e in admitted_entries}
    for name in (NODE, ENTRY, EXTENSION, 'pi-entry.cjs', 'node_modules/pi-acp/dist/index.js', 'node_modules/pi-acp/dist/paperclip-runtime.js'):
        require(name in entries and re.fullmatch(r'[a-f0-9]{64}', entries[name]['sha256']), 'closure_entry')
    pids = [int(p) for p in os.listdir('/proc') if p.isdigit() and int(p) > 1]
    require(len(pids) <= 4096, 'process_bound')
    table = {}
    for pid in pids:
        try:
            table[pid] = proc(pid, boot)
        except (FileNotFoundError, ProcessLookupError):
            continue
        except RuntimeError as error:
            if str(error).endswith(':dead_process'):
                continue
            raise
    def ancestry(pid):
        chain = []
        while pid != root['pid']:
            require(pid in table and len(chain) < 64 and pid not in [p['pid'] for p in chain], 'ancestry')
            chain.append(table[pid]); pid = table[pid]['ppid']
        return chain + [root]
    matches = []
    for pid in table:
        try:
            chain = ancestry(pid)
        except RuntimeError:
            continue
        parent = table[pid]['ppid']
        if parent not in table:
            continue
        parent_args = argv(parent)
        if len(parent_args) != 4 or not parent_args[3].endswith('/distribution/pi-entry.cjs'):
            continue
        distribution = parent_args[3][:-len('/pi-entry.cjs')]
        require(re.fullmatch(r'/tmp/paperclip-acpx-native-[A-Za-z0-9_-]+/distribution', distribution), 'snapshot_path')
        require(parent_args[1:] == ['--require', distribution + '/' + GUARD, distribution + '/pi-entry.cjs'], 'wrapper_parent')
        descriptor = None
        if parent_args[0] != distribution + '/' + NODE:
            # Production nativeBootstrap executes the held Node through child
            # FD 3 (unfenced) or 7 (guardian/credential fences). The child's
            # cmdline retains /proc/self/fd/N; it does not name the source path.
            match = re.fullmatch(r'/proc/self/fd/(3|7)', parent_args[0])
            require(match is not None, 'wrapper_parent')
            descriptor = f'/proc/{parent}/fd/{match.group(1)}'
        # Pi sets process.title and overwrites Linux argv. The exact pinned
        # parent's launch code attests the entrypoint; title alone never selects.
        require(argv(pid) == ['pi'], 'pi_process_title')
        for directory in (distribution, os.path.dirname(distribution)):
            st = os.lstat(directory)
            require(stat.S_ISDIR(st.st_mode) and not st.st_mode & 0o222 and os.path.realpath(directory) == directory, 'snapshot_seal')
        require(os.readlink(f'/proc/{pid}/cwd') == binding['remoteCwd'], 'cwd')
        identities = {}
        for name in (NODE, ENTRY, EXTENSION, 'pi-entry.cjs', 'node_modules/pi-acp/dist/index.js', 'node_modules/pi-acp/dist/paperclip-runtime.js'):
            content, inode = checked_file(distribution + '/' + name, 256 * 1024 * 1024, True)
            require(len(content) == entries[name]['size'] and digest(content) == entries[name]['sha256'], 'snapshot_digest')
            identities[name] = inode
        exe = os.stat(f'/proc/{pid}/exe')
        require((exe.st_dev, exe.st_ino) == identities[NODE], 'pi_executable')
        parent_exe = os.stat(f'/proc/{parent}/exe')
        require((parent_exe.st_dev, parent_exe.st_ino) == identities[NODE], 'wrapper_executable')
        if descriptor is not None:
            held_exe = os.stat(descriptor)
            require((held_exe.st_dev, held_exe.st_ino) == identities[NODE], 'wrapper_descriptor')
        for identity in chain:
            require(proc(identity['pid'], boot) == identity, 'ancestry_changed')
        matches.append({'target': table[pid], 'ancestry': chain, 'nodeSha256': 'sha256:' + entries[NODE]['sha256'],
                        'entrypointSha256': 'sha256:' + entries[ENTRY]['sha256'], 'closureSha256': config['closureSha256'],
                        'entrypointAttribution': 'pinned_wrapper_parent', 'originalChildArgvAvailable': False, 'observedChildTitle': 'pi'})
    require(len(matches) == 1, 'unique_pi_child')
    return matches[0]


def terminate(config):
    require(sys.platform == 'linux' and hasattr(os, 'pidfd_open') and hasattr(signal, 'pidfd_send_signal'), 'pidfd_required')
    before = inspect(config)
    pid = before['target']['pid']
    require(pid != os.getpid() and pid != config['root']['pid'], 'not_worker')
    fd = os.pidfd_open(pid)
    try:
        require(inspect(config) == before, 'identity_changed_after_pidfd')
        fields = dict(line.split(':', 1) for line in Path(f'/proc/self/fdinfo/{fd}').read_text().splitlines() if ':' in line)
        require(int(fields.get('Pid', '-1').strip()) == pid, 'pidfd_retired')
        signal.pidfd_send_signal(fd, signal.SIGKILL, None, 0)
        return {'schema': 'paperclip.e2e.pi-provider-death.v1', 'binding': config['binding'], 'runtimeEnvironmentLeaseId': config['runtimeEnvironmentLeaseId'],
                **before, 'signalled': True, 'signal': 'SIGKILL', 'targetKind': 'pi_native_child', 'workerSignalled': False}
    finally:
        os.close(fd)


if __name__ == '__main__':
    try:
        require(len(sys.argv) == 2 and len(sys.argv[1]) <= 8192, 'input_bound')
        print(json.dumps(terminate(json.loads(base64.b64decode(sys.argv[1], validate=True))), separators=(',', ':')))
    except Exception:
        # Never print process arguments, filesystem paths, or inherited context.
        print(json.dumps({'ok': False, 'code': 'pi_provider_identity_or_signal_failed'}))
        sys.exit(1)