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import json
from typing import Optional

from pypaimon.pynative.common.file_io import FileIO
from pypaimon.pynative.table.snapshot import Snapshot


class SnapshotManager:
    """Manager for snapshot files using unified FileIO."""

    def __init__(self, table):
        from pypaimon.pynative.table.file_store_table import FileStoreTable

        self.table: FileStoreTable = table
        self.file_io: FileIO = self.table.file_io
        self.snapshot_dir = self.table.table_path / "snapshot"

    def get_latest_snapshot(self) -> Optional[Snapshot]:
        latest_file = self.snapshot_dir / "LATEST"
        if not self.file_io.exists(latest_file):
            return None

        latest_content = self.file_io.read_file_utf8(latest_file)
        latest_snapshot_id = int(latest_content.strip())

        snapshot_file = self.snapshot_dir / f"snapshot-{latest_snapshot_id}"
        if not self.file_io.exists(snapshot_file):
            return None

        snapshot_content = self.file_io.read_file_utf8(snapshot_file)
        snapshot_data = json.loads(snapshot_content)
        return Snapshot.from_json(snapshot_data)

    def commit_snapshot(self, snapshot_id: int, snapshot_data: Snapshot):
        snapshot_file = self.snapshot_dir / f"snapshot-{snapshot_id}"
        latest_file = self.snapshot_dir / "LATEST"

        try:
            snapshot_json = json.dumps(snapshot_data.to_json(), indent=2)
            snapshot_success = self.file_io.try_to_write_atomic(snapshot_file, snapshot_json)
            if not snapshot_success:
                self.file_io.write_file(snapshot_file, snapshot_json, overwrite=True)

            latest_success = self.file_io.try_to_write_atomic(latest_file, str(snapshot_id))
            if not latest_success:
                self.file_io.write_file(latest_file, str(snapshot_id), overwrite=True)

        except Exception as e:
            self.file_io.delete_quietly(snapshot_file)
            raise RuntimeError(f"Failed to commit snapshot {snapshot_id}: {e}") from e