#!/usr/bin/env python3
"""Bounded private telemetry jobs for an external scheduler/executor."""
import argparse
from datetime import datetime, timezone
import hashlib
import json
import os
from pathlib import Path
import sqlite3
import stat
import sys
import tempfile
import uuid
from platform_event import translate
from receiver import Receiver, read_json, instant


def private_directory(directory):
    directory.mkdir(mode=0o700, parents=False, exist_ok=True)
    info = directory.lstat()
    if not stat.S_ISDIR(info.st_mode) or info.st_uid != os.getuid() or info.st_mode & 0o077:
        raise ValueError('private owned directory required')


def atomic_json(path, value):
    temporary = None
    try:
        with tempfile.NamedTemporaryFile(mode='w', dir=path.parent, delete=False) as out:
            temporary = out.name
            json.dump(value, out)
            out.flush(); os.fsync(out.fileno())
        os.replace(temporary, path)
        temporary = None
        fd = os.open(path.parent, os.O_RDONLY | os.O_DIRECTORY)
        try: os.fsync(fd)
        finally: os.close(fd)
    finally:
        if temporary: os.unlink(temporary)


def ingest_report(receiver, report, now):
    event = translate(report, receiver.contract)
    # Identical producer reports survive process retries without new identities.
    fingerprint = hashlib.sha256(json.dumps(report, sort_keys=True).encode()).hexdigest()
    event['id'] = str(uuid.uuid5(uuid.NAMESPACE_URL,
        receiver.contract['stream'] + ':' + fingerprint))
    return receiver.ingest(event, now)


def snapshot(receiver, output):
    # SQLite backup includes committed transactions; never copy an open DB file.
    fd = os.open(output, os.O_CREAT | os.O_EXCL | os.O_WRONLY, 0o600)
    os.close(fd)
    target = sqlite3.connect(output)
    try:
        receiver.db.backup(target)
        if target.execute('PRAGMA quick_check').fetchone() != ('ok',):
            raise ValueError('snapshot integrity failed')
        events = target.execute('SELECT COUNT(*) FROM events').fetchone()[0]
        pending = target.execute('SELECT COUNT(*) FROM notices WHERE acknowledged IS NULL').fetchone()[0]
    finally:
        target.close()
    with output.open('rb') as source:
        os.fsync(source.fileno())
        digest = hashlib.file_digest(source, 'sha256').hexdigest()
    return {'status': 'local-snapshot-verified', 'sha256': digest,
            'events': events, 'pending_notices': pending, 'off_host': False}


def watchdog_health(receipt, now):
    if set(receipt) != {'state', 'recipient', 'delivery', 'pending_notices', 'checked_at'}:
        raise ValueError('watchdog receipt fields')
    age = (now - instant(receipt['checked_at'])).total_seconds()
    if age < 0: raise ValueError('future watchdog receipt')
    return {'state': 'watchdog-current' if age <= 180 else 'watchdog-stale',
            'delivery': 'local-check-only'}


def main():
    p = argparse.ArgumentParser(description=__doc__)
    p.add_argument('--contract', required=True, type=Path)
    p.add_argument('--state-dir', required=True, type=Path)
    sub = p.add_subparsers(dest='command', required=True)
    sub.add_parser('ingest-report').add_argument('report', type=Path)
    sub.add_parser('check')
    sub.add_parser('health')
    sub.add_parser('snapshot').add_argument('output', type=Path)
    a = p.parse_args()
    receiver = None
    os.umask(0o077)
    try:
        if a.command == 'health':
            result = watchdog_health(read_json(a.state_dir / 'watchdog-receipt.json'), datetime.now(timezone.utc))
            print(json.dumps(result))
            return 0 if result['state'] == 'watchdog-current' else 1
        private_directory(a.state_dir)
        db = a.state_dir / 'receiver.db'
        # The private directory is the trust boundary. Do not follow existing links.
        if db.is_symlink(): raise ValueError('database symlink')
        receiver = Receiver(db, read_json(a.contract))
        now = datetime.now(timezone.utc)
        if a.command == 'ingest-report': result = ingest_report(receiver, read_json(a.report), now)
        elif a.command == 'snapshot': result = snapshot(receiver, a.output)
        else:
            result = receiver.check(now)
            result['pending_notices'] = len(receiver.inbox()['notices'])
            # A successful invocation is a heartbeat, not a declaration of health.
            atomic_json(a.state_dir / 'watchdog-receipt.json',
                        dict(result, checked_at=now.isoformat()))
        print(json.dumps(result))
        return 0
    except (ValueError, TypeError, KeyError, AttributeError, OSError, sqlite3.Error):
        print(json.dumps({'status': 'failed', 'error': 'runtime-unavailable-or-invalid-input'}))
        return 2
    finally:
        if receiver is not None: receiver.close()


if __name__ == '__main__': sys.exit(main())