use std::collections::HashMap;
use std::str;
use winnow::prelude::*;
use winnow::{
ascii::float,
ascii::line_ending,
combinator::alt,
combinator::cut_err,
combinator::{delimited, preceded, separated_pair, terminated},
combinator::{repeat, separated},
error::{AddContext, ParserError},
stream::Partial,
token::{any, none_of, take, take_while},
};
#[derive(Debug, PartialEq, Clone)]
pub enum JsonValue {
Null,
Boolean(bool),
Str(String),
Num(f64),
Array(Vec<JsonValue>),
Object(HashMap<String, JsonValue>),
}
/// Use `Partial` to cause `ErrMode::Incomplete` while parsing
pub type Stream<'i> = Partial<&'i str>;
pub fn ndjson<'i, E: ParserError<Stream<'i>> + AddContext<Stream<'i>, &'static str>>(
input: &mut Stream<'i>,
) -> PResult<Option<JsonValue>, E> {
alt((
terminated(delimited(ws, json_value, ws), line_ending).map(Some),
line_ending.value(None),
))
.parse_next(input)
}
// --Besides `WS`, same as a regular json parser ----------------------------
/// `alt` is a combinator that tries multiple parsers one by one, until
/// one of them succeeds
fn json_value<'i, E: ParserError<Stream<'i>> + AddContext<Stream<'i>, &'static str>>(
input: &mut Stream<'i>,
) -> PResult<JsonValue, E> {
// `alt` combines the each value parser. It returns the result of the first
// successful parser, or an error
alt((
null.value(JsonValue::Null),
boolean.map(JsonValue::Boolean),
string.map(JsonValue::Str),
float.map(JsonValue::Num),
array.map(JsonValue::Array),
object.map(JsonValue::Object),
))
.parse_next(input)
}
/// `tag(string)` generates a parser that recognizes the argument string.
///
/// This also shows returning a sub-slice of the original input
fn null<'i, E: ParserError<Stream<'i>>>(input: &mut Stream<'i>) -> PResult<&'i str, E> {
// This is a parser that returns `"null"` if it sees the string "null", and
// an error otherwise
"null".parse_next(input)
}
/// We can combine `tag` with other functions, like `value` which returns a given constant value on
/// success.
fn boolean<'i, E: ParserError<Stream<'i>>>(input: &mut Stream<'i>) -> PResult<bool, E> {
// This is a parser that returns `true` if it sees the string "true", and
// an error otherwise
let parse_true = "true".value(true);
// This is a parser that returns `false` if it sees the string "false", and
// an error otherwise
let parse_false = "false".value(false);
alt((parse_true, parse_false)).parse_next(input)
}
/// This parser gathers all `char`s up into a `String`with a parse to recognize the double quote
/// character, before the string (using `preceded`) and after the string (using `terminated`).
fn string<'i, E: ParserError<Stream<'i>> + AddContext<Stream<'i>, &'static str>>(
input: &mut Stream<'i>,
) -> PResult<String, E> {
preceded(
'\"',
// `cut_err` transforms an `ErrMode::Backtrack(e)` to `ErrMode::Cut(e)`, signaling to
// combinators like `alt` that they should not try other parsers. We were in the
// right branch (since we found the `"` character) but encountered an error when
// parsing the string
cut_err(terminated(
repeat(0.., character).fold(String::new, |mut string, c| {
string.push(c);
string
}),
'\"',
)),
)
// `context` lets you add a static string to errors to provide more information in the
// error chain (to indicate which parser had an error)
.context("string")
.parse_next(input)
}
/// You can mix the above declarative parsing with an imperative style to handle more unique cases,
/// like escaping
fn character<'i, E: ParserError<Stream<'i>>>(input: &mut Stream<'i>) -> PResult<char, E> {
let c = none_of('"').parse_next(input)?;
if c == '\\' {
alt((
any.verify_map(|c| {
Some(match c {
'"' | '\\' | '/' => c,
'b' => '\x08',
'f' => '\x0C',
'n' => '\n',
'r' => '\r',
't' => '\t',
_ => return None,
})
}),
preceded('u', unicode_escape),
))
.parse_next(input)
} else {
Ok(c)
}
}
fn unicode_escape<'i, E: ParserError<Stream<'i>>>(input: &mut Stream<'i>) -> PResult<char, E> {
alt((
// Not a surrogate
u16_hex
.verify(|cp| !(0xD800..0xE000).contains(cp))
.map(|cp| cp as u32),
// See https://en.wikipedia.org/wiki/UTF-16#Code_points_from_U+010000_to_U+10FFFF for details
separated_pair(u16_hex, "\\u", u16_hex)
.verify(|(high, low)| (0xD800..0xDC00).contains(high) && (0xDC00..0xE000).contains(low))
.map(|(high, low)| {
let high_ten = (high as u32) - 0xD800;
let low_ten = (low as u32) - 0xDC00;
(high_ten << 10) + low_ten + 0x10000
}),
))
.verify_map(
// Could be probably replaced with .unwrap() or _unchecked due to the verify checks
std::char::from_u32,
)
.parse_next(input)
}
fn u16_hex<'i, E: ParserError<Stream<'i>>>(input: &mut Stream<'i>) -> PResult<u16, E> {
take(4usize)
.verify_map(|s| u16::from_str_radix(s, 16).ok())
.parse_next(input)
}
/// Some combinators, like `separated` or `repeat`, will call a parser repeatedly,
/// accumulating results in a `Vec`, until it encounters an error.
/// If you want more control on the parser application, check out the `iterator`
/// combinator (cf `examples/iterator.rs`)
fn array<'i, E: ParserError<Stream<'i>> + AddContext<Stream<'i>, &'static str>>(
input: &mut Stream<'i>,
) -> PResult<Vec<JsonValue>, E> {
preceded(
('[', ws),
cut_err(terminated(
separated(0.., json_value, (ws, ',', ws)),
(ws, ']'),
)),
)
.context("array")
.parse_next(input)
}
fn object<'i, E: ParserError<Stream<'i>> + AddContext<Stream<'i>, &'static str>>(
input: &mut Stream<'i>,
) -> PResult<HashMap<String, JsonValue>, E> {
preceded(
('{', ws),
cut_err(terminated(
separated(0.., key_value, (ws, ',', ws)),
(ws, '}'),
)),
)
.context("object")
.parse_next(input)
}
fn key_value<'i, E: ParserError<Stream<'i>> + AddContext<Stream<'i>, &'static str>>(
input: &mut Stream<'i>,
) -> PResult<(String, JsonValue), E> {
separated_pair(string, cut_err((ws, ':', ws)), json_value).parse_next(input)
}
/// Parser combinators are constructed from the bottom up:
/// first we write parsers for the smallest elements (here a space character),
/// then we'll combine them in larger parsers
fn ws<'i, E: ParserError<Stream<'i>>>(input: &mut Stream<'i>) -> PResult<&'i str, E> {
// Combinators like `take_while` return a function. That function is the
// parser,to which we can pass the input
take_while(0.., WS).parse_next(input)
}
const WS: &[char] = &[' ', '\t'];
#[cfg(test)]
mod test {
#[allow(clippy::useless_attribute)]
#[allow(dead_code)] // its dead for benches
use super::*;
#[allow(clippy::useless_attribute)]
#[allow(dead_code)] // its dead for benches
type Error<'i> = winnow::error::InputError<Partial<&'i str>>;
#[test]
fn json_string() {
assert_eq!(
string::<Error<'_>>.parse_peek(Partial::new("\"\"")),
Ok((Partial::new(""), "".to_string()))
);
assert_eq!(
string::<Error<'_>>.parse_peek(Partial::new("\"abc\"")),
Ok((Partial::new(""), "abc".to_string()))
);
assert_eq!(
string::<Error<'_>>.parse_peek(Partial::new(
"\"abc\\\"\\\\\\/\\b\\f\\n\\r\\t\\u0001\\u2014\u{2014}def\""
)),
Ok((
Partial::new(""),
"abc\"\\/\x08\x0C\n\r\t\x01——def".to_string()
)),
);
assert_eq!(
string::<Error<'_>>.parse_peek(Partial::new("\"\\uD83D\\uDE10\"")),
Ok((Partial::new(""), "ðŸ˜".to_string()))
);
assert!(string::<Error<'_>>.parse_peek(Partial::new("\"")).is_err());
assert!(string::<Error<'_>>
.parse_peek(Partial::new("\"abc"))
.is_err());
assert!(string::<Error<'_>>
.parse_peek(Partial::new("\"\\\""))
.is_err());
assert!(string::<Error<'_>>
.parse_peek(Partial::new("\"\\u123\""))
.is_err());
assert!(string::<Error<'_>>
.parse_peek(Partial::new("\"\\uD800\""))
.is_err());
assert!(string::<Error<'_>>
.parse_peek(Partial::new("\"\\uD800\\uD800\""))
.is_err());
assert!(string::<Error<'_>>
.parse_peek(Partial::new("\"\\uDC00\""))
.is_err());
}
#[test]
fn json_object() {
use JsonValue::{Num, Object, Str};
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!(
ndjson::<Error<'_>>.parse_peek(Partial::new(input)),
Ok((Partial::new(""), Some(expected)))
);
}
#[test]
fn json_array() {
use JsonValue::{Array, Num, Str};
let input = r#"[42,"x"]
"#;
let expected = Array(vec![Num(42.0), Str("x".to_string())]);
assert_eq!(
ndjson::<Error<'_>>.parse_peek(Partial::new(input)),
Ok((Partial::new(""), Some(expected)))
);
}
#[test]
fn json_whitespace() {
use JsonValue::{Array, Boolean, Null, Num, Object, Str};
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!(
ndjson::<Error<'_>>.parse_peek(Partial::new(input)),
Ok((
Partial::new(""),
Some(Object(
vec![
("null".to_string(), Null),
("true".to_string(), Boolean(true)),
("false".to_string(), Boolean(false)),
("number".to_string(), Num(123e4)),
("string".to_string(), Str(" abc 123 ".to_string())),
(
"array".to_string(),
Array(vec![Boolean(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()
))
))
);
}
}