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# to you under the Apache License, Version 2.0 (the
# "License"); you may not use this file except in compliance
# with the License.  You may obtain a copy of the License at
#
#   http://www.apache.org/licenses/LICENSE-2.0
#
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# software distributed under the License is distributed on an
# "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
# KIND, either express or implied.  See the License for the
# specific language governing permissions and limitations
# under the License.

from abc import ABC, abstractmethod


class Instant(ABC):
    """Table rollback instant.

    Supports polymorphic JSON serialization via to_dict/from_dict

    Serialization format:
        SnapshotInstant: {"type": "snapshot", "snapshotId": 123}
        TagInstant:      {"type": "tag", "tagName": "test_tag"}
    """

    FIELD_TYPE = "type"
    TYPE_SNAPSHOT = "snapshot"
    TYPE_TAG = "tag"

    @staticmethod
    def snapshot(snapshot_id):
        """Create a SnapshotInstant.

        Args:
            snapshot_id: The snapshot ID to rollback to.

        Returns:
            A SnapshotInstant instance.
        """
        return SnapshotInstant(snapshot_id)

    @staticmethod
    def tag(tag_name):
        """Create a TagInstant.

        Args:
            tag_name: The tag name to rollback to.

        Returns:
            A TagInstant instance.
        """
        return TagInstant(tag_name)

    @abstractmethod
    def to_dict(self):
        """Serialize this Instant to a dictionary for JSON output."""

    @staticmethod
    def from_dict(data):
        """Deserialize an Instant from a dictionary.

        Args:
            data: A dictionary with a 'type' field indicating the instant type.

        Returns:
            A SnapshotInstant or TagInstant instance.

        Raises:
            ValueError: If the type field is missing or unknown.
        """
        instant_type = data.get(Instant.FIELD_TYPE)
        if instant_type == Instant.TYPE_SNAPSHOT:
            return SnapshotInstant(data[SnapshotInstant.FIELD_SNAPSHOT_ID])
        elif instant_type == Instant.TYPE_TAG:
            return TagInstant(data[TagInstant.FIELD_TAG_NAME])
        else:
            raise ValueError("Unknown instant type: {}".format(instant_type))


class SnapshotInstant(Instant):
    """Snapshot instant for table rollback."""

    FIELD_SNAPSHOT_ID = "snapshotId"

    def __init__(self, snapshot_id):
        self.snapshot_id = snapshot_id

    def to_dict(self):
        return {
            Instant.FIELD_TYPE: Instant.TYPE_SNAPSHOT,
            self.FIELD_SNAPSHOT_ID: self.snapshot_id,
        }

    def __eq__(self, other):
        if not isinstance(other, SnapshotInstant):
            return False
        return self.snapshot_id == other.snapshot_id

    def __hash__(self):
        return hash(self.snapshot_id)

    def __repr__(self):
        return "SnapshotInstant(snapshot_id={})".format(self.snapshot_id)


class TagInstant(Instant):
    """Tag instant for table rollback."""

    FIELD_TAG_NAME = "tagName"

    def __init__(self, tag_name):
        self.tag_name = tag_name

    def to_dict(self):
        return {
            Instant.FIELD_TYPE: Instant.TYPE_TAG,
            self.FIELD_TAG_NAME: self.tag_name,
        }

    def __eq__(self, other):
        if not isinstance(other, TagInstant):
            return False
        return self.tag_name == other.tag_name

    def __hash__(self):
        return hash(self.tag_name)

    def __repr__(self):
        return "TagInstant(tag_name={})".format(self.tag_name)
