be52af70
 tangwang
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"""
Boolean expression parser for search queries.
Supports: AND, OR, RANK, ANDNOT operators with parentheses.
Precedence (high to low): (), ANDNOT, AND, OR, RANK
"""
import re
from typing import List, Tuple, Optional
from dataclasses import dataclass
@dataclass
class QueryNode:
"""Represents a node in the parsed query tree."""
operator: str # 'AND', 'OR', 'RANK', 'ANDNOT', 'TERM'
terms: List['QueryNode'] = None # Child nodes for operators
value: str = None # Value for leaf nodes (TERM)
def __repr__(self):
if self.operator == 'TERM':
return f"TERM({self.value})"
else:
return f"{self.operator}({', '.join(str(t) for t in self.terms)})"
class BooleanParser:
"""
Parser for boolean search expressions.
Operator precedence (high to low):
1. () - Parentheses
2. ANDNOT - AND NOT (exclusion)
3. AND - All terms must match
4. OR - Any term must match
5. RANK - Scoring boost (like OR but affects ranking)
"""
OPERATORS = {'AND', 'OR', 'RANK', 'ANDNOT'}
PRECEDENCE = {
'ANDNOT': 3,
'AND': 2,
'OR': 1,
'RANK': 0
}
def __init__(self):
"""Initialize boolean parser."""
pass
def parse(self, expression: str) -> QueryNode:
"""
Parse boolean expression into query tree.
Args:
expression: Boolean expression string
Example: "laptop AND (gaming OR professional) ANDNOT cheap"
Returns:
Root QueryNode of parsed tree
"""
if not expression or not expression.strip():
return QueryNode(operator='TERM', value='')
# Tokenize
tokens = self._tokenize(expression)
if not tokens:
return QueryNode(operator='TERM', value='')
# Parse with precedence
return self._parse_expression(tokens)
def _tokenize(self, expression: str) -> List[str]:
"""
Tokenize expression into terms and operators.
Args:
expression: Expression string
Returns:
List of tokens
"""
# Pattern to match: operators, parentheses, or terms (with domain prefix support)
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be52af70
tangwang
first commit
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tokens = []
for match in re.finditer(pattern, expression):
token = match.group().strip()
if token:
tokens.append(token)
return tokens
def _parse_expression(self, tokens: List[str], start: int = 0) -> Tuple[QueryNode, int]:
"""
Parse expression with operator precedence.
Args:
tokens: List of tokens
start: Starting index
Returns:
Tuple of (QueryNode, next_index)
"""
# Start with lowest precedence (RANK)
return self._parse_rank(tokens, start)
def _parse_rank(self, tokens: List[str], start: int) -> Tuple[QueryNode, int]:
"""Parse RANK operator (lowest precedence)."""
left, pos = self._parse_or(tokens, start)
while pos < len(tokens) and tokens[pos] == 'RANK':
pos += 1 # Skip 'RANK'
right, pos = self._parse_or(tokens, pos)
left = QueryNode(operator='RANK', terms=[left, right])
return left, pos
def _parse_or(self, tokens: List[str], start: int) -> Tuple[QueryNode, int]:
"""Parse OR operator."""
left, pos = self._parse_and(tokens, start)
while pos < len(tokens) and tokens[pos] == 'OR':
pos += 1 # Skip 'OR'
right, pos = self._parse_and(tokens, pos)
left = QueryNode(operator='OR', terms=[left, right])
return left, pos
def _parse_and(self, tokens: List[str], start: int) -> Tuple[QueryNode, int]:
"""Parse AND operator."""
left, pos = self._parse_andnot(tokens, start)
while pos < len(tokens) and tokens[pos] == 'AND':
pos += 1 # Skip 'AND'
right, pos = self._parse_andnot(tokens, pos)
left = QueryNode(operator='AND', terms=[left, right])
return left, pos
def _parse_andnot(self, tokens: List[str], start: int) -> Tuple[QueryNode, int]:
"""Parse ANDNOT operator (highest precedence)."""
left, pos = self._parse_primary(tokens, start)
while pos < len(tokens) and tokens[pos] == 'ANDNOT':
pos += 1 # Skip 'ANDNOT'
right, pos = self._parse_primary(tokens, pos)
left = QueryNode(operator='ANDNOT', terms=[left, right])
return left, pos
def _parse_primary(self, tokens: List[str], start: int) -> Tuple[QueryNode, int]:
"""Parse primary expression (terms or parentheses)."""
if start >= len(tokens):
return QueryNode(operator='TERM', value=''), start
token = tokens[start]
# Handle parentheses
if token == '(':
# Find matching closing parenthesis
depth = 1
pos = start + 1
while pos < len(tokens) and depth > 0:
if tokens[pos] == '(':
depth += 1
elif tokens[pos] == ')':
depth -= 1
pos += 1
# Parse contents of parentheses
inner_tokens = tokens[start + 1:pos - 1]
if inner_tokens:
node, _ = self._parse_expression(inner_tokens, 0)
return node, pos
else:
return QueryNode(operator='TERM', value=''), pos
# Handle term
if token not in self.OPERATORS and token not in ['(', ')']:
return QueryNode(operator='TERM', value=token), start + 1
# Unexpected token
return QueryNode(operator='TERM', value=''), start + 1
def is_simple_query(self, expression: str) -> bool:
"""
Check if query is simple (no boolean operators).
Args:
expression: Query expression
Returns:
True if simple query (no operators)
"""
tokens = self._tokenize(expression)
for token in tokens:
if token in self.OPERATORS:
return False
return True
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