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#[derive(Copy, Clone, Debug, PartialEq)]
pub enum Token<'a> {
OpeningBrace,
ClosingBrace,
Op(Operator),
Number(f64),
StringLiteral(&'a str),
Identifier(&'a str),
Raw(&'a str),
}
#[derive(Copy, Clone, Debug, PartialEq)]
pub enum Operator {
Plus,
Dash,
Slash,
Asterisk,
OpeningParen,
ClosingParen,
Pipe,
}
impl Operator {
pub fn value(&self) -> u32 {
use self::Operator::*;
match *self {
Pipe => 0,
Plus => 1,
Dash => 2,
Asterisk => 3,
Slash => 4,
OpeningParen => 5,
ClosingParen => 5,
}
}
}
#[derive(Clone, Debug, PartialEq)]
pub struct Tokenizer<'a> {
source: &'a str,
in_template: bool,
}
impl<'a> Tokenizer<'a> {
pub fn new(source: &'a str) -> Tokenizer<'a> {
Tokenizer {
source,
in_template: false,
}
}
}
impl<'a> Iterator for Tokenizer<'a> {
type Item = Result<Token<'a>, String>;
fn next(&mut self) -> Option<Result<Token<'a>, String>> {
use self::Operator::*;
use self::Token::*;
if self.source.len() == 0 {
return None;
}
if !self.in_template {
let index = self.source.find("{{").unwrap_or_else(|| self.source.len());
if index == 0 {
self.source = &self.source[2..];
self.in_template = true;
return Some(Ok(OpeningBrace));
} else {
let (next, source) = self.source.split_at(index);
self.source = source;
return Some(Ok(Raw(next)));
}
} else {
let word = self.source.split_whitespace().next()?;
let word_start = self.source.find(word.chars().next().unwrap()).unwrap();
self.source = &self.source[word_start..];
let word_len = word.len();
let mut end = self.source[..word_len].find("}}").unwrap_or(word_len);
if end == 0 {
self.source = &self.source[2..];
self.in_template = false;
return Some(Ok(ClosingBrace));
}
if let Some(operator) =
self.source[..end].find(&['|', '*', '+', '-', '/', '(', ')', '"'] as &[char])
{
if operator == 0 {
let op = &self.source[0..1];
self.source = &self.source[1..];
return Some(match op {
"+" => Ok(Op(Plus)),
"-" => Ok(Op(Dash)),
"/" => Ok(Op(Slash)),
"*" => Ok(Op(Asterisk)),
"|" => Ok(Op(Pipe)),
"(" => Ok(Op(OpeningParen)),
")" => Ok(Op(ClosingParen)),
"\"" => {
if let Some(end) = self.source.find('"') {
let quote = &self.source[..end];
self.source = &self.source[end + 1..];
Ok(StringLiteral(quote))
} else {
Err("No closing quotation mark".to_string())
}
}
op => Err(format!("invalid operator {}", op)),
});
}
end = operator;
}
let word = &word[..end];
self.source = &self.source[end..];
if let Ok(num) = word[..end].parse() {
return Some(Ok(Number(num)));
}
if word.contains('"') {
self.source = "";
return Some(Err("Badly placed quotation mark".to_string()));
}
Some(Ok(Identifier(word)))
}
}
}
#[cfg(test)]
mod tests {
use super::Operator::*;
use super::Token::*;
use super::Tokenizer;
#[test]
fn tokens() {
let source = r#"this is a very {{ adjective | to_upper }} system of extra {{super}}ness.
{{2+2/1}}
{{ some_var | concat "various tests " }}
{{ -3.4 * -count }}"#;
assert_eq!(
Tokenizer::new(source)
.collect::<Result<Vec<_>, String>>()
.unwrap(),
vec![
Raw("this is a very "),
OpeningBrace,
Identifier("adjective"),
Op(Pipe),
Identifier("to_upper"),
ClosingBrace,
Raw(" system of extra "),
OpeningBrace,
Identifier("super"),
ClosingBrace,
Raw("ness.\n "),
OpeningBrace,
Number(2.0),
Op(Plus),
Number(2.0),
Op(Slash),
Number(1.0),
ClosingBrace,
Raw("\n "),
OpeningBrace,
Identifier("some_var"),
Op(Pipe),
Identifier("concat"),
StringLiteral("various tests "),
ClosingBrace,
Raw("\n "),
OpeningBrace,
Op(Dash),
Number(3.4),
Op(Asterisk),
Op(Dash),
Identifier("count"),
ClosingBrace,
]
);
}
}