whereexpr 0.1.0

A fast, expressive rule-based filtering engine for Rust that evaluates boolean expressions over any data structure
Documentation 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190

    use super::{Token, TokenKind, TokenSpan};
    use crate::Error;
    use crate::condition_list::ConditionList;

    const MAX_PAREN_DEPTH: usize = 8;

    pub(crate) fn validate_parentheses(tokens: &[Token], condition: &str) -> Result<(), Error> {
        let mut depth: usize = 0;
        let mut stack = [TokenSpan::default(); MAX_PAREN_DEPTH];

        for token in tokens {
            match token.kind() {
                TokenKind::LParen => {
                    if depth == MAX_PAREN_DEPTH {
                        return Err(Error::MaxParenDepthExceeded(token.span().start() as u32, token.span().end() as u32, condition.to_string()));
                    }
                    stack[depth] = token.span();
                    depth += 1;
                }
                TokenKind::RParen => {
                    if depth == 0 {
                        return Err(Error::UnexpectedCloseParen(token.span().start() as u32, token.span().end() as u32, condition.to_string()));
                    }
                    depth -= 1;
                }
                _ => {}
            }
        }

        if depth > 0 {
            // report the innermost unclosed paren
            return Err(Error::UnclosedParenthesis(stack[depth - 1].start() as u32, stack[depth - 1].end() as u32, condition.to_string()));
        }

        Ok(())
    }

    pub(crate) fn resolve_rule_names(tokens: &mut [Token], input: &str, conditions: &ConditionList) -> Result<(), Error> {
        for token in tokens.iter_mut() {
            if token.kind() == TokenKind::ConditionIndex(u16::MAX) {
                let name = token.span().as_slice(input);
                match conditions.from_name(name) {
                    Some(idx) => *token = Token::new(TokenKind::ConditionIndex(idx), token.span().start(), token.span().end()),
                    None => return Err(Error::UnknownConditionName(token.span().start() as u32, token.span().end() as u32, input.to_string())),
                }
            }
        }
        Ok(())
    }

    pub(crate) fn validate_token_pairs(tokens: &[Token], condition: &str) -> Result<(), Error> {
        // check first token
        match tokens[0].kind() {
            TokenKind::ConditionIndex(_) | TokenKind::Not | TokenKind::LParen => {}
            _ => return Err(Error::UnexpectedTokenAtStart(tokens[0].span().start() as u32, tokens[0].span().end() as u32, condition.to_string())),
        }

        // check last token
        match tokens[tokens.len() - 1].kind() {
            TokenKind::ConditionIndex(_) | TokenKind::RParen => {}
            _ => return Err(Error::UnexpectedTokenAtEnd(tokens[tokens.len() - 1].span().start() as u32, tokens[tokens.len() - 1].span().end() as u32, condition.to_string())),
        }

        // check pairs
        for i in 0..tokens.len() - 1 {
            let current = tokens[i].kind();
            let next = tokens[i + 1].kind();

            match (current, next) {
                // after RuleName: only AND, OR, RParen allowed
                (TokenKind::ConditionIndex(_), TokenKind::And) => {}
                (TokenKind::ConditionIndex(_), TokenKind::Or) => {}
                (TokenKind::ConditionIndex(_), TokenKind::RParen) => {}
                (TokenKind::ConditionIndex(_), TokenKind::ConditionIndex(_)) => {
                    return Err(Error::MissingOperator(tokens[i + 1].span().start() as u32, tokens[i + 1].span().end() as u32, condition.to_string()));
                }
                (TokenKind::ConditionIndex(_), TokenKind::LParen) => {
                    return Err(Error::MissingOperator(tokens[i + 1].span().start() as u32, tokens[i + 1].span().end() as u32, condition.to_string()));
                }
                (TokenKind::ConditionIndex(_), TokenKind::Not) => {
                    return Err(Error::MissingOperator(tokens[i + 1].span().start() as u32, tokens[i + 1].span().end() as u32, condition.to_string()));
                }

                // after AND: only RuleName, NOT, LParen allowed
                (TokenKind::And, TokenKind::ConditionIndex(_)) => {}
                (TokenKind::And, TokenKind::Not) => {}
                (TokenKind::And, TokenKind::LParen) => {}
                (TokenKind::And, TokenKind::And) | (TokenKind::And, TokenKind::Or) => {
                    return Err(Error::MissingOperand(tokens[i + 1].span().start() as u32, tokens[i + 1].span().end() as u32, condition.to_string()));
                }
                (TokenKind::And, TokenKind::RParen) => {
                    return Err(Error::MissingOperand(tokens[i + 1].span().start() as u32, tokens[i + 1].span().end() as u32, condition.to_string()));
                }

                // after OR: only RuleName, NOT, LParen allowed
                (TokenKind::Or, TokenKind::ConditionIndex(_)) => {}
                (TokenKind::Or, TokenKind::Not) => {}
                (TokenKind::Or, TokenKind::LParen) => {}
                (TokenKind::Or, TokenKind::And) | (TokenKind::Or, TokenKind::Or) => {
                    return Err(Error::MissingOperand(tokens[i + 1].span().start() as u32, tokens[i + 1].span().end() as u32, condition.to_string()));
                }
                (TokenKind::Or, TokenKind::RParen) => {
                    return Err(Error::MissingOperand(tokens[i + 1].span().start() as u32, tokens[i + 1].span().end() as u32, condition.to_string()));
                }

                // after NOT: only RuleName, LParen allowed
                (TokenKind::Not, TokenKind::ConditionIndex(_)) => {}
                (TokenKind::Not, TokenKind::LParen) => {}
                (TokenKind::Not, TokenKind::Not) => {
                    return Err(Error::DoubleNegation(tokens[i + 1].span().start() as u32, tokens[i + 1].span().end() as u32, condition.to_string()));
                }
                (TokenKind::Not, TokenKind::And) | (TokenKind::Not, TokenKind::Or) => {
                    return Err(Error::NegationOfOperator(tokens[i + 1].span().start() as u32, tokens[i + 1].span().end() as u32, condition.to_string()));
                }
                (TokenKind::Not, TokenKind::RParen) => {
                    return Err(Error::NegationOfCloseParen(tokens[i + 1].span().start() as u32, tokens[i + 1].span().end() as u32, condition.to_string()));
                }

                // after LParen: only RuleName, NOT, LParen allowed
                (TokenKind::LParen, TokenKind::ConditionIndex(_)) => {}
                (TokenKind::LParen, TokenKind::Not) => {}
                (TokenKind::LParen, TokenKind::LParen) => {}
                (TokenKind::LParen, TokenKind::RParen) => {
                    return Err(Error::EmptyParenthesis(tokens[i + 1].span().start() as u32, tokens[i + 1].span().end() as u32, condition.to_string()));
                }
                (TokenKind::LParen, TokenKind::And) | (TokenKind::LParen, TokenKind::Or) => {
                    return Err(Error::OperatorAfterOpenParen(tokens[i + 1].span().start() as u32, tokens[i + 1].span().end() as u32, condition.to_string()));
                }

                // after RParen: only AND, OR, RParen allowed
                (TokenKind::RParen, TokenKind::And) => {}
                (TokenKind::RParen, TokenKind::Or) => {}
                (TokenKind::RParen, TokenKind::RParen) => {}
                (TokenKind::RParen, TokenKind::ConditionIndex(_)) => {
                    return Err(Error::MissingOperator(tokens[i + 1].span().start() as u32, tokens[i + 1].span().end() as u32, condition.to_string()));
                }
                (TokenKind::RParen, TokenKind::LParen) => {
                    return Err(Error::MissingOperator(tokens[i + 1].span().start() as u32, tokens[i + 1].span().end() as u32, condition.to_string()));
                }
                (TokenKind::RParen, TokenKind::Not) => {
                    return Err(Error::MissingOperator(tokens[i + 1].span().start() as u32, tokens[i + 1].span().end() as u32, condition.to_string()));
                }
            }
        }

        Ok(())
    }

    #[derive(Copy, Clone, Default)]
    struct NestedDepth {
        uses_and: bool,
        uses_or: bool,
    }

    pub(crate) fn validate_same_operation_per_level(tokens: &[Token], condition: &str) -> Result<(), Error> {
        let mut nested_level: [NestedDepth; MAX_PAREN_DEPTH + 2] = [NestedDepth::default(); MAX_PAREN_DEPTH + 2];
        let mut index = 1; // root is consdered level 1
        for tok in tokens {
            match tok.kind() {
                TokenKind::And => {
                    if nested_level[index].uses_or {
                        return Err(Error::MixedOperators(tok.span().start() as u32, tok.span().end() as u32, condition.to_string()));
                    }
                    nested_level[index].uses_and = true;
                }
                TokenKind::Or => {
                    if nested_level[index].uses_and {
                        return Err(Error::MixedOperators(tok.span().start() as u32, tok.span().end() as u32, condition.to_string()));
                    }                
                    nested_level[index].uses_or = true;
                }
                TokenKind::LParen => {
                    index += 1;
                    nested_level[index] = NestedDepth::default();
                }
                TokenKind::RParen => index -= 1,
                _ => {}
            }
        }
        Ok(())
    }

    pub(crate) fn validate(tokens: &mut [Token], input: &str, conditions: &ConditionList) -> Result<(), Error> {
        validate_parentheses(tokens, input)?;
        resolve_rule_names(tokens, input, conditions)?;
        validate_token_pairs(tokens, input)?;
        // must be called after the depth is being tested
        validate_same_operation_per_level(tokens, input)?;
        Ok(())
    }