sketchy attempt at parsing expressions using pypeg2

Author: nickzoic

countess/utils/expression_to_sql.py

@@ -0,0 +1,146 @@
+import re
+
+import pypeg2
+
+class SqlTemplatingSymbol(pypeg2.Symbol):
+    def sql(self):
+        return str(self.name)
+
+class IntegerLiteral(SqlTemplatingSymbol):
+    regex = re.compile(r'[0-9]+')
+
+class DecimalLiteral(SqlTemplatingSymbol):
+    regex = re.compile(r'[0-9]+\.[0-9]+')
+
+    def sql(self):
+        return str(self.name) + "::DECIMAL"
+
+class SingleQuotedStringLiteral(SqlTemplatingSymbol):
+    regex = re.compile(r"'(?:\\.|[^'\n])*'")
+
+class DoubleQuotedStringLiteral(SqlTemplatingSymbol):
+    regex = re.compile(r'"(?:\\.|[^"\n])*"')
+
+class Label(SqlTemplatingSymbol):
+    regex = re.compile(r"[A-Za-z_][A-Za-z_0-9]*")
+
+class SqlTemplatingList(pypeg2.List):
+    before = ''
+    between = ''
+    after = ''
+
+    def sql(self):
+        return self.before + self.between.join(s.sql() for s in self) + self.after
+
+class ParenExpr(SqlTemplatingList):
+    grammar = None  # filled in later
+    before = "("
+    after = ")"
+
+class FunctionName(SqlTemplatingSymbol):
+    regex = re.compile(r'[a-z]+')
+
+    def __init__(self, name, namespace=None):
+        print(f"FUNCTION NAME CHECK: {name}")
+        if name not in ('hello'):
+            raise ValueError("unknown function")
+        super().__init__(name, namespace)
+
+class FunctionCall(pypeg2.Concat):
+    grammar = None  # filled in later
+
+    def sql(self):
+        return f"{self[0].sql()}({self[1].sql()})"
+
+class Value(pypeg2.Concat):
+    grammar = [FunctionCall, Label, DecimalLiteral, IntegerLiteral, SingleQuotedStringLiteral, DoubleQuotedStringLiteral, ParenExpr]
+
+    def sql(self):
+        return self[0].sql()
+
+FunctionCall.grammar = FunctionName, "(", Value, ")"
+
+class UnaOp(SqlTemplatingSymbol):
+    regex = re.compile(r"[+-]")
+
+class UnaExpr(SqlTemplatingList):
+    grammar = pypeg2.optional(UnaOp), Value
+
+class PowOp(SqlTemplatingSymbol):
+    regex = re.compile(r"\*\*")
+
+class PowExpr(SqlTemplatingList):
+    grammar = UnaExpr, pypeg2.maybe_some((PowOp, UnaExpr))
+
+class MulOp(SqlTemplatingSymbol):
+    regex = re.compile(r"[*/]")
+
+class MulExpr(SqlTemplatingList):
+    grammar = PowExpr, pypeg2.maybe_some((MulOp, PowExpr))
+
+class AddOp(SqlTemplatingSymbol):
+    regex = re.compile(r"[+-]")
+
+class AddExpr(SqlTemplatingList):
+    grammar = MulExpr, pypeg2.maybe_some((AddOp, MulExpr))
+
+class NotOp(SqlTemplatingSymbol):
+    regex = re.compile(r"not")
+
+class NotExpr(SqlTemplatingList):
+    grammar = pypeg2.maybe_some(NotOp), AddExpr
+
+class AndExpr(SqlTemplatingList):
+    grammar = NotExpr, pypeg2.maybe_some("and", NotExpr)
+    between = ' AND '
+
+class OrExpr(SqlTemplatingList):
+    grammar = AndExpr, pypeg2.maybe_some("or", AndExpr)
+    between = ' OR '
+
+ParenExpr.grammar = "(", OrExpr, ")"
+
+class Assignment(pypeg2.Concat):
+    grammar = Label, "=", OrExpr
+
+    def sql(self):
+        return self[1].sql() + " AS " + self[0].sql()
+
+class Filter(pypeg2.Concat):
+    # for backwards compatibility
+    grammar = "__filter", "=", OrExpr
+
+    def sql(self):
+        return self[0].sql()
+
+class Block(pypeg2.Concat):
+    grammar = pypeg2.some([Filter, Assignment, OrExpr])
+
+    def sql(self):
+        selects = []
+        wheres = []
+        for s in self:
+            if isinstance(s, Assignment):
+                selects.append(s.sql())
+            else:
+                wheres.append(s.sql())
+
+        sql = f"SELECT {', '.join(selects)}"
+        if wheres:
+            sql += "WHERE { ' AND '.join(wheres) }"
+        return sql
+
+
+block = r"""
+hello = "world"
+foo = 107+42/3.001
+baz = hello("quuux")
+ford = 10**2
+sdfklsdf = 10**-2
+"""
+
+pp = pypeg2.parse(block, Block)
+
+print(pp)
+print(pp.sql())
+