# dialects/postgresql/dml.py
# Copyright (C) 2005-2026 the SQLAlchemy authors and contributors
# <see AUTHORS file>
#
# This module is part of SQLAlchemy and is released under
# the MIT License: https://www.opensource.org/licenses/mit-license.php
from __future__ import annotations

from typing import Any
from typing import Dict
from typing import List
from typing import Optional
from typing import Union

from . import ext
from .._typing import _OnConflictConstraintT
from .._typing import _OnConflictIndexElementsT
from .._typing import _OnConflictIndexWhereT
from .._typing import _OnConflictSetT
from .._typing import _OnConflictWhereT
from ... import util
from ...sql import coercions
from ...sql import roles
from ...sql import schema
from ...sql._typing import _DMLTableArgument
from ...sql.base import _exclusive_against
from ...sql.base import ColumnCollection
from ...sql.base import ReadOnlyColumnCollection
from ...sql.base import SyntaxExtension
from ...sql.dml import _DMLColumnElement
from ...sql.dml import Insert as StandardInsert
from ...sql.elements import ClauseElement
from ...sql.elements import ColumnElement
from ...sql.elements import KeyedColumnElement
from ...sql.elements import TextClause
from ...sql.expression import alias
from ...sql.type_api import NULLTYPE
from ...sql.visitors import InternalTraversal
from ...util.typing import Self

__all__ = ("Insert", "insert")


def insert(table: _DMLTableArgument) -> Insert:
    """Construct a PostgreSQL-specific variant :class:`_postgresql.Insert`
    construct.

    .. container:: inherited_member

        The :func:`sqlalchemy.dialects.postgresql.insert` function creates
        a :class:`sqlalchemy.dialects.postgresql.Insert`.  This class is based
        on the dialect-agnostic :class:`_sql.Insert` construct which may
        be constructed using the :func:`_sql.insert` function in
        SQLAlchemy Core.

    The :class:`_postgresql.Insert` construct includes additional methods
    :meth:`_postgresql.Insert.on_conflict_do_update`,
    :meth:`_postgresql.Insert.on_conflict_do_nothing`.

    """
    return Insert(table)


class Insert(StandardInsert):
    """PostgreSQL-specific implementation of INSERT.

    Adds methods for PG-specific syntaxes such as ON CONFLICT.

    The :class:`_postgresql.Insert` object is created using the
    :func:`sqlalchemy.dialects.postgresql.insert` function.

    """

    stringify_dialect = "postgresql"
    inherit_cache = True

    @util.memoized_property
    def excluded(
        self,
    ) -> ReadOnlyColumnCollection[str, KeyedColumnElement[Any]]:
        """Provide the ``excluded`` namespace for an ON CONFLICT statement

        PG's ON CONFLICT clause allows reference to the row that would
        be inserted, known as ``excluded``.  This attribute provides
        all columns in this row to be referenceable.

        .. tip::  The :attr:`_postgresql.Insert.excluded` attribute is an
            instance of :class:`_expression.ColumnCollection`, which provides
            an interface the same as that of the :attr:`_schema.Table.c`
            collection described at :ref:`metadata_tables_and_columns`.
            With this collection, ordinary names are accessible like attributes
            (e.g. ``stmt.excluded.some_column``), but special names and
            dictionary method names should be accessed using indexed access,
            such as ``stmt.excluded["column name"]`` or
            ``stmt.excluded["values"]``.   See the docstring for
            :class:`_expression.ColumnCollection` for further examples.

        .. seealso::

            :ref:`postgresql_insert_on_conflict` - example of how
            to use :attr:`_expression.Insert.excluded`

        """
        return alias(self.table, name="excluded").columns

    _on_conflict_exclusive = _exclusive_against(
        "_post_values_clause",
        msgs={
            "_post_values_clause": "This Insert construct already has "
            "an ON CONFLICT clause established"
        },
    )

    @_on_conflict_exclusive
    def on_conflict_do_update(
        self,
        constraint: _OnConflictConstraintT = None,
        index_elements: _OnConflictIndexElementsT = None,
        index_where: _OnConflictIndexWhereT = None,
        set_: _OnConflictSetT = None,
        where: _OnConflictWhereT = None,
    ) -> Self:
        r"""
        Specifies a DO UPDATE SET action for ON CONFLICT clause.

        Either the ``constraint`` or ``index_elements`` argument is
        required, but only one of these can be specified.

        :param constraint:
         The name of a unique or exclusion constraint on the table,
         or the constraint object itself if it has a .name attribute.

        :param index_elements:
         A sequence consisting of string column names, :class:`_schema.Column`
         objects, or other column expression objects that will be used
         to infer a target index.

        :param index_where:
         Additional WHERE criterion that can be used to infer a
         conditional target index.

        :param set\_:
         A dictionary or other mapping object
         where the keys are either names of columns in the target table,
         or :class:`_schema.Column` objects or other ORM-mapped columns
         matching that of the target table, and expressions or literals
         as values, specifying the ``SET`` actions to take.

         .. versionadded:: 1.4 The
            :paramref:`_postgresql.Insert.on_conflict_do_update.set_`
            parameter supports :class:`_schema.Column` objects from the target
            :class:`_schema.Table` as keys.

         .. warning:: This dictionary does **not** take into account
            Python-specified default UPDATE values or generation functions,
            e.g. those specified using :paramref:`_schema.Column.onupdate`.
            These values will not be exercised for an ON CONFLICT style of
            UPDATE, unless they are manually specified in the
            :paramref:`.Insert.on_conflict_do_update.set_` dictionary.

        :param where:
         Optional argument. An expression object representing a ``WHERE``
         clause that restricts the rows affected by ``DO UPDATE SET``. Rows not
         meeting the ``WHERE`` condition will not be updated (effectively a
         ``DO NOTHING`` for those rows).


        .. seealso::

            :ref:`postgresql_insert_on_conflict`

        """
        return self.ext(
            OnConflictDoUpdate(
                constraint, index_elements, index_where, set_, where
            )
        )

    @_on_conflict_exclusive
    def on_conflict_do_nothing(
        self,
        constraint: _OnConflictConstraintT = None,
        index_elements: _OnConflictIndexElementsT = None,
        index_where: _OnConflictIndexWhereT = None,
    ) -> Self:
        """
        Specifies a DO NOTHING action for ON CONFLICT clause.

        The ``constraint`` and ``index_elements`` arguments
        are optional, but only one of these can be specified.

        :param constraint:
         The name of a unique or exclusion constraint on the table,
         or the constraint object itself if it has a .name attribute.

        :param index_elements:
         A sequence consisting of string column names, :class:`_schema.Column`
         objects, or other column expression objects that will be used
         to infer a target index.

        :param index_where:
         Additional WHERE criterion that can be used to infer a
         conditional target index.

        .. seealso::

            :ref:`postgresql_insert_on_conflict`

        """
        return self.ext(
            OnConflictDoNothing(constraint, index_elements, index_where)
        )


class OnConflictClause(SyntaxExtension, ClauseElement):
    stringify_dialect = "postgresql"

    constraint_target: Optional[str]
    inferred_target_elements: Optional[List[Union[str, schema.Column[Any]]]]
    inferred_target_whereclause: Optional[
        Union[ColumnElement[Any], TextClause]
    ]

    _traverse_internals = [
        ("constraint_target", InternalTraversal.dp_string),
        ("inferred_target_elements", InternalTraversal.dp_multi_list),
        ("inferred_target_whereclause", InternalTraversal.dp_clauseelement),
    ]

    def __init__(
        self,
        constraint: _OnConflictConstraintT = None,
        index_elements: _OnConflictIndexElementsT = None,
        index_where: _OnConflictIndexWhereT = None,
    ):
        if constraint is not None:
            if not isinstance(constraint, str) and isinstance(
                constraint,
                (schema.Constraint, ext.ExcludeConstraint),
            ):
                constraint = getattr(constraint, "name") or constraint

        if constraint is not None:
            if index_elements is not None:
                raise ValueError(
                    "'constraint' and 'index_elements' are mutually exclusive"
                )

            if isinstance(constraint, str):
                self.constraint_target = constraint
                self.inferred_target_elements = None
                self.inferred_target_whereclause = None
            elif isinstance(constraint, schema.Index):
                index_elements = constraint.expressions
                index_where = constraint.dialect_options["postgresql"].get(
                    "where"
                )
            elif isinstance(constraint, ext.ExcludeConstraint):
                index_elements = constraint.columns
                index_where = constraint.where
            else:
                index_elements = constraint.columns
                index_where = constraint.dialect_options["postgresql"].get(
                    "where"
                )

        if index_elements is not None:
            self.constraint_target = None
            self.inferred_target_elements = [
                coercions.expect(roles.DDLConstraintColumnRole, column)
                for column in index_elements
            ]

            self.inferred_target_whereclause = (
                coercions.expect(
                    (
                        roles.StatementOptionRole
                        if isinstance(constraint, ext.ExcludeConstraint)
                        else roles.WhereHavingRole
                    ),
                    index_where,
                )
                if index_where is not None
                else None
            )

        elif constraint is None:
            self.constraint_target = self.inferred_target_elements = (
                self.inferred_target_whereclause
            ) = None

    def apply_to_insert(self, insert_stmt: StandardInsert) -> None:
        insert_stmt.apply_syntax_extension_point(
            self.append_replacing_same_type, "post_values"
        )


class OnConflictDoNothing(OnConflictClause):
    __visit_name__ = "on_conflict_do_nothing"

    inherit_cache = True


class OnConflictDoUpdate(OnConflictClause):
    __visit_name__ = "on_conflict_do_update"

    update_values_to_set: Dict[_DMLColumnElement, ColumnElement[Any]]
    update_whereclause: Optional[ColumnElement[Any]]

    _traverse_internals = OnConflictClause._traverse_internals + [
        ("update_values_to_set", InternalTraversal.dp_dml_values),
        ("update_whereclause", InternalTraversal.dp_clauseelement),
    ]

    def __init__(
        self,
        constraint: _OnConflictConstraintT = None,
        index_elements: _OnConflictIndexElementsT = None,
        index_where: _OnConflictIndexWhereT = None,
        set_: _OnConflictSetT = None,
        where: _OnConflictWhereT = None,
    ):
        super().__init__(
            constraint=constraint,
            index_elements=index_elements,
            index_where=index_where,
        )

        if (
            self.inferred_target_elements is None
            and self.constraint_target is None
        ):
            raise ValueError(
                "Either constraint or index_elements, "
                "but not both, must be specified unless DO NOTHING"
            )

        if isinstance(set_, dict):
            if not set_:
                raise ValueError("set parameter dictionary must not be empty")
        elif isinstance(set_, ColumnCollection):
            set_ = dict(set_)
        else:
            raise ValueError(
                "set parameter must be a non-empty dictionary "
                "or a ColumnCollection such as the `.c.` collection "
                "of a Table object"
            )

        self.update_values_to_set = {
            coercions.expect(roles.DMLColumnRole, k): coercions.expect(
                roles.ExpressionElementRole, v, type_=NULLTYPE, is_crud=True
            )
            for k, v in set_.items()
        }
        self.update_whereclause = (
            coercions.expect(roles.WhereHavingRole, where)
            if where is not None
            else None
        )
