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|
/* ANCHOR: all */
use std::collections::HashMap;
use logos::{Lexer, Logos};
/* ANCHOR: lexers */
type SymbolTable = HashMap<String, String>;
#[derive(Logos, Debug, PartialEq, Clone)]
#[logos(skip r"\s+")]
#[logos(extras = SymbolTable)]
enum VariableDefinitionContext {
#[regex(r"[[:alpha:]][[:alnum:]]*", variable_definition)]
Id((String /* variable name */, String /* value */)),
#[token("=")]
Equals,
#[token("'")]
Quote,
}
#[derive(Logos, Debug, PartialEq, Clone)]
#[logos(extras = SymbolTable)]
enum StringContext {
#[token("'")]
Quote,
#[regex("[^'$]+")]
Content,
#[token("${", evaluate_interpolation)]
InterpolationStart(String /* evaluated value of the interpolation */),
#[token("$")]
DollarSign,
}
#[derive(Logos, Debug, PartialEq, Clone)]
#[logos(skip r"\s+")]
#[logos(extras = SymbolTable)]
enum StringInterpolationContext {
#[regex(r"[[:alpha:]][[:alnum:]]*", get_variable_value)]
Id(String /* value for the given id */),
#[token("'")]
Quote,
#[token("}")]
InterpolationEnd,
}
/* ANCHOR_END: lexers */
/* ANCHOR: variable_definition */
fn get_string_content(lex: &mut Lexer<StringContext>) -> String {
let mut s = String::new();
while let Some(Ok(token)) = lex.next() {
match token {
StringContext::Content => s.push_str(lex.slice()),
StringContext::DollarSign => s.push('$'),
StringContext::InterpolationStart(value) => s.push_str(&value),
StringContext::Quote => break,
}
}
s
}
fn variable_definition(lex: &mut Lexer<VariableDefinitionContext>) -> Option<(String, String)> {
let id = lex.slice().to_string();
if let Some(Ok(VariableDefinitionContext::Equals)) = lex.next() {
if let Some(Ok(VariableDefinitionContext::Quote)) = lex.next() {
let mut lex2 = lex.clone().morph::<StringContext>();
let value = get_string_content(&mut lex2);
*lex = lex2.morph();
lex.extras.insert(id.clone(), value.clone());
return Some((id, value));
}
}
None
}
/* ANCHOR_END: variable_definition */
/* ANCHOR: evaluate_interpolation */
fn evaluate_interpolation(lex: &mut Lexer<StringContext>) -> Option<String> {
let mut lex2 = lex.clone().morph::<StringInterpolationContext>();
let mut interpolation = String::new();
while let Some(result) = lex2.next() {
match result {
Ok(token) => match token {
StringInterpolationContext::Id(value) => interpolation.push_str(&value),
StringInterpolationContext::Quote => {
*lex = lex2.morph();
interpolation.push_str(&get_string_content(lex));
lex2 = lex.clone().morph();
}
StringInterpolationContext::InterpolationEnd => break,
},
Err(()) => panic!("Interpolation error"),
}
}
*lex = lex2.morph();
Some(interpolation)
}
/* ANCHOR_END: evaluate_interpolation */
/* ANCHOR: get_variable_value */
fn get_variable_value(lex: &mut Lexer<StringInterpolationContext>) -> Option<String> {
if let Some(value) = lex.extras.get(lex.slice()) {
return Some(value.clone());
}
None
}
/* ANCHOR_END: get_variable_value */
/* ANCHOR: main */
fn test_variable_definition(
expeected_id: &str,
expeected_value: &str,
token: Option<Result<VariableDefinitionContext, ()>>,
) {
if let Some(Ok(VariableDefinitionContext::Id((id, value)))) = token {
assert_eq!(id, expeected_id);
assert_eq!(value, expeected_value);
} else {
panic!("Expected key: {} not found", expeected_id);
}
}
fn main() {
let mut lex = VariableDefinitionContext::lexer(
"\
name = 'Mark'\n\
greeting = 'Hi ${name}!'\n\
surname = 'Scott'\n\
greeting2 = 'Hi ${name ' ' surname}!'\n\
greeting3 = 'Hi ${name ' ${surname}!'}!'\n\
",
);
test_variable_definition("name", "Mark", lex.next());
test_variable_definition("greeting", "Hi Mark!", lex.next());
test_variable_definition("surname", "Scott", lex.next());
test_variable_definition("greeting2", "Hi Mark Scott!", lex.next());
test_variable_definition("greeting3", "Hi Mark Scott!!", lex.next());
}
/* ANCHOR_END: main */
/* ANCHOR_END: all */
|
