#!/usr/bin/env python3
"""Format-5 exchange across frozen V5/V7 writers and the current V8 engine."""
import hashlib
import importlib.util
import json
from pathlib import Path
import sys
import tempfile

HERE = Path(__file__).resolve().parent
ROOT = HERE.parent
sys.dont_write_bytecode = True


def load(name, path):
    spec = importlib.util.spec_from_file_location(name, path)
    module = importlib.util.module_from_spec(spec)
    sys.modules[name] = module
    spec.loader.exec_module(module)
    return module


def main():
    paths = {'v5': HERE / 'baselines/v5.py', 'v7': HERE / 'baselines/v7.py',
             'v8': ROOT / 'pagefs.py'}
    hashes = {name: hashlib.sha256(path.read_bytes()).hexdigest() for name, path in paths.items()}
    modules = {name: load('compat_' + name, path) for name, path in paths.items()}
    checks = []
    for origin in ('v5', 'v7'):
        expected = {f'/entry/{i:04d}': bytes([i % 251]) * 128 for i in range(128)}
        receipts = {}
        with tempfile.TemporaryDirectory(prefix='nyarion-v8-compatible-') as tmp:
            image = Path(tmp) / 'compatible.img'
            with modules[origin].PageStore.create(image, initial_files=expected, pool_blocks=2048) as store:
                for i in range(100):
                    key, data, token = f'/entry/{i:04d}', bytes([i]) * 1024, f'old-{i}'
                    receipts[token] = store.transact({key: data}, token)
                    expected[key] = data
                store.checkpoint()
            with modules['v8'].PageStore(image) as store:
                for key, data in expected.items():
                    assert store.get(key) == data
                for i in range(100):
                    key, data, token = f'/entry/{i:04d}', bytes([i + 1]) * 128, f'new-{i}'
                    receipts[token] = store.transact({key: data}, token)
                    expected[key] = data
                store.checkpoint()
            for reader in ('v5', 'v7', 'v8'):
                with modules[reader].PageStore(image, writable=False) as store:
                    assert store.epoch == 200
                    assert store.files() == sorted(expected)
                    for key, data in expected.items():
                        assert store.get(key) == data
                    for token, epoch in receipts.items():
                        assert store.query(token)['epoch'] == epoch
                checks.append({'initial_writer': origin, 'subsequent_writer': 'v8',
                               'reader': reader, 'transactions': 200,
                               'exact_receipt_epochs_and_contents_verified': True})
    assert {name: hashlib.sha256(path.read_bytes()).hexdigest() for name, path in paths.items()} == hashes
    result = {'passed': True, 'persistent_format': 5, 'source_sha256': hashes,
              'volumes': 2, 'transactions_per_volume': 200, 'reader_checks': checks,
              'scope': 'format compatibility; older writers do not inherit V8 admission guarantees'}
    (HERE / 'compatibility_results.json').write_text(json.dumps(result, indent=2) + '\n')
    print(json.dumps(result, indent=2))


if __name__ == '__main__':
    main()