Build a Python Utility That Verifies Backup Integrity Automatically

import hashlib
import os
import json

def compute_checksum(filepath, algorithm='sha256'):
    """Compute checksum for the given file."""
    hash_func = hashlib.new(algorithm)
    with open(filepath, 'rb') as f:
        for chunk in iter(lambda: f.read(4096), b''):
            hash_func.update(chunk)
    return hash_func.hexdigest()

def verify_backup_integrity(backup_dir, manifest_file='integrity_check.json'):
    """Verify backup files against a stored manifest of checksums."""
    if not os.path.isfile(manifest_file):
        print(f"Manifest file {manifest_file} not found. Creating it now...")
        manifest = {}
        for root, _, files in os.walk(backup_dir):
            for file in files:
                filepath = os.path.join(root, file)
                manifest[filepath] = compute_checksum(filepath)
        with open(manifest_file, 'w') as f:
            json.dump(manifest, f, indent=2)
        print("Manifest created. Run again to verify.")
        return

    with open(manifest_file, 'r') as f:
        manifest = json.load(f)

    errors = []
    for filepath, expected_checksum in manifest.items():
        if not os.path.exists(filepath):
            errors.append(f"Missing: {filepath}")
            continue
        current_checksum = compute_checksum(filepath)
        if current_checksum != expected_checksum:
            errors.append(f"Corrupted: {filepath} (expected {expected_checksum}, got {current_checksum})")

    if errors:
        print("Integrity check failed:")
        for err in errors:
            print(f"  - {err}")
    else:
        print("Backup integrity verified successfully.")

if __name__ == "__main__":
    verify_backup_integrity('/path/to/backup')