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#![cfg(feature = "alloc")]
use nom::{
branch::alt,
bytes::complete::{tag, take},
character::complete::{anychar, char, multispace0, none_of},
combinator::{map, map_opt, map_res, value, verify},
error::ParseError,
multi::{fold_many0, separated_list0},
number::complete::double,
sequence::{delimited, preceded, separated_pair},
IResult, Parser,
};
use std::collections::HashMap;
#[derive(Debug, PartialEq, Clone)]
pub enum JsonValue {
Null,
Bool(bool),
Str(String),
Num(f64),
Array(Vec<JsonValue>),
Object(HashMap<String, JsonValue>),
}
fn boolean(input: &str) -> IResult<&str, bool> {
alt((value(false, tag("false")), value(true, tag("true"))))(input)
}
fn u16_hex(input: &str) -> IResult<&str, u16> {
map_res(take(4usize), |s| u16::from_str_radix(s, 16))(input)
}
fn unicode_escape(input: &str) -> IResult<&str, char> {
map_opt(
alt((
// Not a surrogate
map(verify(u16_hex, |cp| !(0xD800..0xE000).contains(cp)), |cp| {
cp as u32
}),
map(
verify(
separated_pair(u16_hex, tag("\\u"), u16_hex),
|(high, low)| (0xD800..0xDC00).contains(high) && (0xDC00..0xE000).contains(low),
),
|(high, low)| {
let high_ten = (high as u32) - 0xD800;
let low_ten = (low as u32) - 0xDC00;
(high_ten << 10) + low_ten + 0x10000
},
),
)),
// Could be probably replaced with .unwrap() or _unchecked due to the verify checks
std::char::from_u32,
)(input)
}
fn character(input: &str) -> IResult<&str, char> {
let (input, c) = none_of("\"")(input)?;
if c == '\\' {
alt((
map_res(anychar, |c| {
Ok(match c {
'"' | '\\' | '/' => c,
'b' => '\x08',
'f' => '\x0C',
'n' => '\n',
'r' => '\r',
't' => '\t',
_ => return Err(()),
})
}),
preceded(char('u'), unicode_escape),
))(input)
} else {
Ok((input, c))
}
}
fn string(input: &str) -> IResult<&str, String> {
delimited(
char('"'),
fold_many0(character, String::new, |mut string, c| {
string.push(c);
string
}),
char('"'),
)(input)
}
fn ws<'a, O, E: ParseError<&'a str>, F: Parser<&'a str, O, E>>(f: F) -> impl Parser<&'a str, O, E> {
delimited(multispace0, f, multispace0)
}
fn array(input: &str) -> IResult<&str, Vec<JsonValue>> {
delimited(
char('['),
ws(separated_list0(ws(char(',')), json_value)),
char(']'),
)(input)
}
fn object(input: &str) -> IResult<&str, HashMap<String, JsonValue>> {
map(
delimited(
char('{'),
ws(separated_list0(
ws(char(',')),
separated_pair(string, ws(char(':')), json_value),
)),
char('}'),
),
|key_values| key_values.into_iter().collect(),
)(input)
}
fn json_value(input: &str) -> IResult<&str, JsonValue> {
use JsonValue::*;
alt((
value(Null, tag("null")),
map(boolean, Bool),
map(string, Str),
map(double, Num),
map(array, Array),
map(object, Object),
))(input)
}
fn json(input: &str) -> IResult<&str, JsonValue> {
ws(json_value).parse(input)
}
#[test]
fn json_string() {
assert_eq!(string("\"\""), Ok(("", "".to_string())));
assert_eq!(string("\"abc\""), Ok(("", "abc".to_string())));
assert_eq!(
string("\"abc\\\"\\\\\\/\\b\\f\\n\\r\\t\\u0001\\u2014\u{2014}def\""),
Ok(("", "abc\"\\/\x08\x0C\n\r\t\x01——def".to_string())),
);
assert_eq!(string("\"\\uD83D\\uDE10\""), Ok(("", "😐".to_string())));
assert!(string("\"").is_err());
assert!(string("\"abc").is_err());
assert!(string("\"\\\"").is_err());
assert!(string("\"\\u123\"").is_err());
assert!(string("\"\\uD800\"").is_err());
assert!(string("\"\\uD800\\uD800\"").is_err());
assert!(string("\"\\uDC00\"").is_err());
}
#[test]
fn json_object() {
use JsonValue::*;
let input = r#"{"a":42,"b":"x"}"#;
let expected = Object(
vec![
("a".to_string(), Num(42.0)),
("b".to_string(), Str("x".to_string())),
]
.into_iter()
.collect(),
);
assert_eq!(json(input), Ok(("", expected)));
}
#[test]
fn json_array() {
use JsonValue::*;
let input = r#"[42,"x"]"#;
let expected = Array(vec![Num(42.0), Str("x".to_string())]);
assert_eq!(json(input), Ok(("", expected)));
}
#[test]
fn json_whitespace() {
use JsonValue::*;
let input = r#"
{
"null" : null,
"true" :true ,
"false": false ,
"number" : 123e4 ,
"string" : " abc 123 " ,
"array" : [ false , 1 , "two" ] ,
"object" : { "a" : 1.0 , "b" : "c" } ,
"empty_array" : [ ] ,
"empty_object" : { }
}
"#;
assert_eq!(
json(input),
Ok((
"",
Object(
vec![
("null".to_string(), Null),
("true".to_string(), Bool(true)),
("false".to_string(), Bool(false)),
("number".to_string(), Num(123e4)),
("string".to_string(), Str(" abc 123 ".to_string())),
(
"array".to_string(),
Array(vec![Bool(false), Num(1.0), Str("two".to_string())])
),
(
"object".to_string(),
Object(
vec![
("a".to_string(), Num(1.0)),
("b".to_string(), Str("c".to_string())),
]
.into_iter()
.collect()
)
),
("empty_array".to_string(), Array(vec![]),),
("empty_object".to_string(), Object(HashMap::new()),),
]
.into_iter()
.collect()
)
))
);
}