Initial Commit

base.py

@@ -0,0 +1,45 @@
+from abc import abstractmethod
+from typing import Any, Protocol, runtime_checkable
+from itertools import chain
+from psycopg import sql
+
+
+@runtime_checkable
+class Expression(Protocol):
+    __slots__ = ()
+
+    @abstractmethod
+    def as_tuple(self) -> tuple[sql.Composable, tuple[Any, ...]]:
+        raise NotImplementedError
+
+
+class RawExpr(Expression):
+    __slots__ = ('expr', 'values')
+
+    expr: sql.Composable
+    values: tuple[Any, ...]
+
+    def __init__(self, expr: sql.Composable, values: tuple[Any, ...] = ()):
+        self.expr = expr
+        self.values = values
+
+    def as_tuple(self):
+        return (self.expr, self.values)
+
+    @classmethod
+    def join(cls, *expressions: Expression, joiner: sql.SQL = sql.SQL(' ')):
+        """
+        Join a sequence of Expressions into a single RawExpr.
+        """
+        tups = (
+            expression.as_tuple()
+            for expression in expressions
+        )
+        return cls.join_tuples(*tups, joiner=joiner)
+
+    @classmethod
+    def join_tuples(cls, *tuples: tuple[sql.Composable, tuple[Any, ...]], joiner: sql.SQL = sql.SQL(' ')):
+        exprs, values = zip(*tuples)
+        expr = joiner.join(exprs)
+        value = tuple(chain(*values))
+        return cls(expr, value)