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//! This example tokenizes a slightly modified form of JSON.
#![allow(missing_docs)]
use alkale::{
common::string::{ParseCharError, StringTokenError},
format_notification, map_single_char_token,
notification::{NotificationBuilder, NotificationSeverity},
span::Spanned,
token::Token,
LexerResult, SourceCodeScanner,
};
#[derive(Debug, Clone)]
pub enum JsonToken {
OpenBrace,
CloseBrace,
OpenBracket,
CloseBracket,
Colon,
Comma,
Null,
Bool(bool),
Str(String),
Number(f64),
}
pub fn main() {
use JsonToken::{
Bool, CloseBrace, CloseBracket, Colon, Comma, Null, Number, OpenBrace, OpenBracket, Str,
};
let code = r##"
{
"a": "Assigned to the \"a\" property!",
"b" : 25.2,
"c": false,
"d": true,
"12": null,
"list": [
1,
-2e+2,
3.1
]
}
"##;
let context = SourceCodeScanner::new(code);
let mut result = LexerResult::<JsonToken, ()>::new();
while context.has_next() {
// Map single-character tokens to their data.
map_single_char_token!(&context, &mut result,
'{' => OpenBrace,
'}' => CloseBrace,
'[' => OpenBracket,
']' => CloseBracket,
':' => Colon,
',' => Comma,
);
// Attempt to parse an identifier for certain tokens.
if let Some(Spanned { data, span }) = context.try_consume_standard_identifier() {
let tk = match data {
"null" => Some(Null),
"true" => Some(Bool(true)),
"false" => Some(Bool(false)),
_ => None,
};
// If the above table mapped the identifier to valid token data, push a token.
// If it didn't report an error— either way restart the loop.
if let Some(tk) = tk {
result.push_token(Token::new(tk, span));
} else {
format_notification!("Unexpected identifier {data}")
.span(span)
.severity(NotificationSeverity::Error)
.report(&mut result);
}
continue;
}
// If the next element in the source code is a string, parse it and report errors as necessary.
if let Some(Spanned { data, span }) = context.try_parse_strict_string() {
match data {
Ok(string) => {
// Push the valid string.
result.push_token(Token::new(Str(string), span));
}
Err(errors) => {
// Create a notification for every error.
for error in errors {
use ParseCharError::{
IllegalEscape, NoCharFound, NoEscape, UnescapedDelimiter,
};
use StringTokenError::{CharError, NoClosingDelimiter};
let builder = match error {
CharError(NoEscape(span)) => {
NotificationBuilder::new("Missing escape code after backslash")
.span(span)
}
CharError(IllegalEscape(char, span)) => {
format_notification!("Illegal escape code '{char}'").span(span)
}
CharError(NoCharFound) => {
unreachable!("Strings will never create this error")
}
CharError(UnescapedDelimiter(_)) => {
unreachable!("String methods cannot create this error")
}
NoClosingDelimiter => {
NotificationBuilder::new("Missing closing delimiter on string")
.span(span)
}
_ => NotificationBuilder::new("Unknown error").span(span),
};
builder
.severity(NotificationSeverity::Error)
.report(&mut result);
}
}
}
continue;
}
// If the next character is a minus sign, skip it and set
// this variable to its span. Otherwise, set it to None.
//
// Note: Negatives are parsed during lexing because no subtraction
// exists in JSON, every - sign is unary so there's no ambiguity.
let negative_sign_span = if context.peek_is('-') {
let span = context.next_span().unwrap().span;
context.skip_whitespace();
Some(span)
} else {
None
};
// Attempt to parse a floating point number. If one was found and it was valid, push
// a token for it, otherwise report a parsing error.
if let Some(Spanned { data, span }) = context.try_parse_float() {
if let Ok(mut number) = data {
// If a negative sign was found prior, negate the number.
// This is completely lossless because floating point numbers use a sign bit.
negative_sign_span.is_some().then(|| number = -number);
result.push_token(Token::new(Number(number), span));
} else {
NotificationBuilder::new("Floating-point number is malformed")
.severity(NotificationSeverity::Error)
.span(span)
.report(&mut result);
}
continue;
} else if let Some(span) = negative_sign_span {
// If no number was found, but we DID find a negative sign, then that negative sign is alone and
// is thus invalid.
NotificationBuilder::new("Negative sign should have a number after it")
.severity(NotificationSeverity::Error)
.span(span)
.report(&mut result);
continue;
}
// If whitespace is found, skip it and continue, otherwise throw an error indicating this
// is an unknown character.
if context.peek_is_map(char::is_whitespace) {
context.skip_whitespace();
} else {
let Spanned { data, span } = context.next_span().unwrap();
format_notification!("Unexpected character '{data}'")
.severity(NotificationSeverity::Error)
.span(span)
.report(&mut result);
}
}
println!("{:#?}", result.finalize());
}