# src/rhosocial/activerecord/backend/base/returning.py
from typing import List, Optional, Union

from ..expression import bases, Column, Literal
from ..expression.statements import ReturningClause
from ..schema import StatementType


class ReturningClauseMixin:
    """Mixin for RETURNING clause processing."""
    def _process_returning_clause(self, returning: Optional[Union[bool, List[str], List["bases.BaseExpression"], ReturningClause]]) -> Optional[ReturningClause]:
        """
        Process RETURNING specification and create ReturningClause object.

        Args:
            returning: Can be a boolean flag, a list of column names, a list of expressions, or a ReturningClause object.

        Returns:
            ReturningClause object if returning is specified, None otherwise.
        """
        if returning is None:
            return None
        if isinstance(returning, bool):
            # If True, return all columns; if False, return None
            if returning:
                # Return a simple * literal for all columns
                return ReturningClause(self.dialect, expressions=[Literal(self.dialect, "*")])
            else:
                return None
        elif isinstance(returning, list):
            # List might contain column names (strings) or expressions
            expr_list = []
            for item in returning:
                if isinstance(item, str):
                    # String is a column name
                    expr_list.append(Column(self.dialect, item))
                elif isinstance(item, bases.BaseExpression):
                    # Item is already an expression
                    expr_list.append(item)
                else:
                    # Treat as literal value
                    expr_list.append(Literal(self.dialect, item))
            return ReturningClause(self.dialect, expressions=expr_list)
        elif isinstance(returning, ReturningClause):
            # Already a ReturningClause object
            return returning
        raise ValueError(f"Unsupported returning type: {type(returning)}")

    def _prepare_returning_clause(self, sql: str, returning_clause: Optional[ReturningClause], _stmt_type: StatementType) -> str:
        """
        Prepare SQL with RETURNING clause.

        Args:
            sql: Original SQL statement
            returning_clause: ReturningClause object to append, or None
            _stmt_type: Type of statement (SELECT, INSERT, UPDATE, DELETE) - reserved for future use

        Returns:
            Modified SQL with RETURNING clause appended if applicable.
        """
        # This is a placeholder for logic that would exist in a real implementation
        if returning_clause:
            returning_sql, _ = returning_clause.to_sql()
            return f"{sql} {returning_sql}"
        return sql