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# to you under the Apache License, Version 2.0 (the
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#
#   http://www.apache.org/licenses/LICENSE-2.0
#
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from pypaimon.table.row.offset_row import OffsetRow
from pypaimon.table.row.row_kind import RowKind


class KeyValue:
    """A key value, including user key, sequence number, value kind and value."""

    def __init__(self, key_arity: int, value_arity: int):
        self.key_arity = key_arity
        self.value_arity = value_arity

        self._row_tuple = None
        self._reused_key = OffsetRow(None, 0, key_arity)
        self._reused_value = OffsetRow(None, key_arity + 2, value_arity)

    def replace(self, row_tuple: tuple):
        self._row_tuple = row_tuple
        self._reused_key.replace(row_tuple)
        self._reused_value.replace(row_tuple)
        return self

    def copy(self) -> 'KeyValue':
        """Return an independent KeyValue carrying the current row tuple.

        ``replace`` swaps the tuple reference rather than mutating it, so a
        copy stays valid even if a pooled/reused source KeyValue is later
        replaced again. Callers that need to hold onto a kv past the next
        ``replace`` (e.g. FirstRowMergeFunction keeping the first row while
        the writer folds with a single pooled KeyValue) use this.
        """
        new = KeyValue(self.key_arity, self.value_arity)
        if self._row_tuple is not None:
            new.replace(self._row_tuple)
        return new

    def is_add(self) -> bool:
        return RowKind.is_add_byte(self.value_row_kind_byte)

    @property
    def key(self) -> OffsetRow:
        return self._reused_key

    @property
    def value(self) -> OffsetRow:
        return self._reused_value

    @property
    def sequence_number(self) -> int:
        return self._row_tuple[self.key_arity]

    @property
    def value_row_kind_byte(self) -> int:
        return self._row_tuple[self.key_arity + 1]
