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#[derive(Clone, Debug)]
pub(crate) enum Token {
OpenBrace {
line: usize,
column: usize,
},
CloseBrace {
line: usize,
column: usize,
},
Identifier {
value: String,
line: usize,
column: usize,
},
String {
value: String,
line: usize,
column: usize,
},
Keyword {
value: String,
line: usize,
column: usize,
},
Number {
value: i32,
line: usize,
column: usize,
},
}
impl Token {
pub(crate) fn line_column(&self) -> (usize, usize) {
match self {
Token::OpenBrace { line, column }
| Token::CloseBrace { line, column }
| Token::Identifier { line, column, .. }
| Token::String { line, column, .. }
| Token::Keyword { line, column, .. }
| Token::Number { line, column, .. } => (*line, *column),
}
}
}
pub(crate) fn lex(input: &str) -> Vec<Token> {
let mut tokens = Vec::new();
let mut chars = input.chars().peekable();
let mut line = 1;
let mut column = 1;
while let Some(&c) = chars.peek() {
if c.is_whitespace() {
if c == '\n' {
line += 1;
column = 1;
} else {
column += 1;
}
chars.next();
} else if c == '#' {
// Consume characters until newline.
while let Some(&c) = chars.peek() {
if c == '\n' {
break;
}
chars.next();
}
} else if c.is_ascii_digit() {
let mut s = String::new();
while let Some(&c) = chars.peek() {
if c.is_ascii_digit() {
s.push(c);
chars.next();
column += 1;
} else {
break;
}
}
// Check the next character.
if let Some(&c) = chars.peek() {
if c.is_alphanumeric() || c == '-' {
// If the next character is a letter or a hyphen, treat the
// whole sequence as a string.
s.push(c);
chars.next();
column += 1;
while let Some(&c) = chars.peek() {
if c.is_alphanumeric() || c == '-' {
s.push(c);
chars.next();
column += 1;
} else {
break;
}
}
tokens.push(Token::String {
value: s,
line,
column,
});
} else {
// If the next character is not a letter or a hyphen, treat
// the sequence as a number.
tokens.push(Token::Number {
value: s.parse().unwrap(),
line,
column,
});
}
} else {
// If there is no next character, treat the sequence as a
// number.
tokens.push(Token::Number {
value: s.parse().unwrap(),
line,
column,
});
}
} else if c.is_alphanumeric() || c == '-' {
let mut s = String::new();
while let Some(&c) = chars.peek() {
if c.is_alphanumeric() || c == '-' {
s.push(c);
chars.next();
column += 1;
} else {
break;
}
}
if [
"state",
"start-state",
"start-pattern",
"sample",
"pattern",
"sequence",
"state-table",
]
.contains(&s.as_str())
{
tokens.push(Token::Keyword {
value: s.clone(),
line,
column,
});
if s == "sample" {
let Some(_) = chars.peek() else {
panic!("{line}:{column}: expected a string after 'sample', found 'EOF'");
};
// After a keyword "sample", expect a string.
while let Some(&c) = chars.peek() {
if c.is_whitespace() {
if c == '\n' {
panic!(
"{line}:{column}: expected a string after 'sample', found '{c}'",
);
} else {
column += 1;
}
chars.next();
} else if c.is_alphanumeric() || c == '-' {
let mut s = String::new();
while let Some(&c) = chars.peek() {
if c.is_alphanumeric() || c == '-' {
s.push(c);
chars.next();
column += 1;
} else {
break;
}
}
tokens.push(Token::String {
value: s,
line,
column,
});
break;
}
}
let Some(_) = chars.peek() else {
panic!(
"{line}:{column}: expected an identifier after 'sample' string, found 'EOF'",
);
};
// After a string, expect an identifier.
while let Some(&c) = chars.peek() {
if c.is_whitespace() {
if c == '\n' {
panic!(
"{line}:{column}: expected an identifier after 'sample' string, found '{c}'",
);
} else {
column += 1;
}
chars.next();
} else if c.is_alphanumeric() || c == '-' {
let mut s = String::new();
while let Some(&c) = chars.peek() {
if c.is_alphanumeric() || c == '-' {
s.push(c);
chars.next();
column += 1;
} else {
break;
}
}
tokens.push(Token::Identifier {
value: s,
line,
column,
});
break;
}
}
}
} else {
tokens.push(Token::String {
value: s,
line,
column,
});
}
} else if c == '{' {
tokens.push(Token::OpenBrace { line, column });
chars.next();
column += 1;
} else if c == '}' {
tokens.push(Token::CloseBrace { line, column });
chars.next();
column += 1;
} else {
panic!("{line}:{column}: unexpected '{c}'");
}
}
tokens
}