pex 0.2.4

A nightly parser combinator library for Rust.
Documentation 
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use super::*;
use crate::utils::hex_to_u8;

/// Parse the given state as a single quote string, all characters are allowed in strings except `'`, but including `\'`.
///
/// # Examples
pub fn surround_pair_with_escaper<'i>(state: ParseState<'i>, bound: char, escaper: char) -> ParseResult<&'i str> {
    let mut offset = 0;
    let mut rest = state.residual.chars().peekable();
    match rest.next() {
        Some(start) if start == bound => offset += bound.len_utf8(),
        _ => StopBecause::missing_character(bound, state.start_offset)?,
    }
    let mut closed = false;
    while let Some(c) = rest.next() {
        offset += c.len_utf8();
        match c {
            _ if c == bound => {
                closed = true;
                break;
            }
            _ if c == escaper => match rest.next() {
                Some(next) => offset += next.len_utf8(),
                None => StopBecause::missing_character_set("ANY", state.start_offset + offset)?,
            },
            _ => {}
        }
    }
    if !closed {
        StopBecause::missing_character(bound, state.start_offset + offset)?
    }
    state.advance_view(offset)
}

/// Parse the given state as a single quote string,
/// such strings are allowed to contain escape symbols `\\`,
/// if you want to disallow escape symbols, please use [surround_pair].
///
/// # Patterns
///
/// ```ygg
/// ''
/// 'TEXT'
/// 'TEXT \' TEXT'
/// ```
///
/// # Examples
///
/// ```
/// # use pex::{helpers::{quotation_pair}, ParseState};
/// let normal = ParseState::new("'hello'");
/// let escape = ParseState::new("'hello \\\' world'");
///
/// assert!(quotation_pair(normal, '\'', '\'').is_success());
/// assert!(quotation_pair(escape, '\'', '\'').is_success());
/// ```
pub fn quotation_pair(input: ParseState, lhs: char, rhs: char) -> ParseResult<SurroundPair> {
    let (s_lhs, left) = input.match_str_if(|c| c == lhs, "QUOTATION_LHS")?;
    let (s_body, body) = s_lhs.match_str_until(|c| c == rhs, "QUOTATION_RHS")?;
    let (s_rhs, right) = s_body.match_str_if(|c| c == rhs, "QUOTATION_RHS")?;
    s_rhs.finish(SurroundPair {
        head: StringView::new(left, input.start_offset),
        body: StringView::new(body, s_lhs.start_offset),
        tail: StringView::new(right, s_body.start_offset),
    })
}

/// Parse the given state as a single quote string,
/// such strings are allowed to contain escape symbols `\\`,
/// if you want to disallow escape symbols, please use [surround_pair].
///
/// # Patterns
///
/// ```ygg
/// ""
/// "TEXT"
/// "TEXT \" TEXT"
/// ```
///
/// # Examples
///
/// ```
/// # use pex::{helpers::{quotation_pair_escaped}, ParseState};
/// let normal = ParseState::new(r#""hello""#);
/// let escape = ParseState::new(r#""hello \" world""#);
///
/// assert!(quotation_pair_escaped(normal, '"').is_success());
/// assert!(quotation_pair_escaped(escape, '"').is_success());
/// ```
pub fn quotation_pair_escaped<'i>(state: ParseState<'i>, bound: char) -> ParseResult<&'i str> {
    surround_pair_with_escaper(state, bound, '\\')
}

/// Parse the given state as a single quote string,
/// such strings are allowed to contain escape symbols `\\`,
/// if you want to disallow escape symbols, please use [surround_pair].
///
/// # Patterns
///
/// ```ygg
/// ""
/// "TEXT"
/// "TEXT \" TEXT"
/// ```
///
/// # Examples
///
/// ```
/// # use pex::{helpers::{quotation_pair_escaped}, ParseState};
/// let normal = ParseState::new(r#""hello""#);
/// let escape = ParseState::new(r#""hello \" world""#);
///
/// assert!(quotation_pair_escaped(normal, '"').is_success());
/// assert!(quotation_pair_escaped(escape, '"').is_success());
/// ```
pub fn quotation_pair_nested(input: ParseState, delimiter: char) -> ParseResult<SurroundPair> {
    let (state, bound) = input.match_str_if(|c| c == delimiter, "QUOTE")?;
    match bound.len() {
        0 => StopBecause::missing_character(delimiter, input.start_offset)?,
        2 => state.finish(SurroundPair {
            head: StringView::new(bound, input.start_offset),
            body: StringView::new("", input.start_offset + 1),
            tail: StringView::new(bound, input.start_offset + 1),
        }),
        n => {
            match state.residual.find(bound) {
                Some(s) => state.advance(n + s).finish(SurroundPair {
                    head: StringView::new(bound, input.start_offset),
                    // SAFETY: `lhs` is a substring of `state.residual`
                    body: unsafe {
                        let text = state.residual.get_unchecked(0..s);
                        StringView::new(text, input.start_offset + n)
                    },
                    tail: StringView::new(bound, input.start_offset + n + s),
                }),
                None => StopBecause::missing_character(delimiter, state.start_offset)?,
            }
        }
    }
}

/// Parse the given state as a single quote string, `\u1234`
///
///
/// # Patterns
///
/// ```ygg
/// ""
/// "TEXT"
/// "TEXT \" TEXT"
/// ```
///
/// # Examples
///
/// ```
/// # use pex::{helpers::{quotation_pair_escaped}, ParseState};
/// let normal = ParseState::new(r#""hello""#);
/// let escape = ParseState::new(r#""hello \" world""#);
///
/// assert!(quotation_pair_escaped(normal, '"').is_success());
/// assert!(quotation_pair_escaped(escape, '"').is_success());
/// ```
#[derive(Copy, Clone, Debug)]
pub struct UnicodeUnescape {
    /// Whether the string is insensitive to case
    pub insensitive: bool,
    /// Whether the string is surrounded by braces, e.g. `\\u{1234}`
    pub curly_brace: bool,
}

impl Default for UnicodeUnescape {
    fn default() -> Self {
        Self { insensitive: false, curly_brace: true }
    }
}

impl<'i> FnOnce<(ParseState<'i>,)> for UnicodeUnescape {
    type Output = ParseResult<'i, char>;
    #[inline]
    extern "rust-call" fn call_once(self, (input,): (ParseState<'i>,)) -> Self::Output {
        let (state, _) = match self.insensitive {
            true => input.match_str_insensitive("\\u"),
            false => input.match_str("\\u"),
        }?;
        match self.curly_brace {
            true => unescape_us(state),
            false => unescape_u(state),
        }
    }
}

/// `\u1234`
fn unescape_u(input: ParseState) -> ParseResult<char> {
    match input.residual.as_bytes() {
        [c1, c2, c3, c4] => match hex4_to_char(*c1, *c2, *c3, *c4) {
            Some(c) => input.advance(4).finish(c),
            None => StopBecause::custom_error("Invalid unicode escape sequence", input.start_offset, input.start_offset + 4)?,
        },
        _ => StopBecause::custom_error("Invalid unicode escape sequence", input.start_offset, input.start_offset + 4)?,
    }
}

/// `\u{}, \u{0}, \u{1234}, \u{123456}`
pub fn unescape_us(input: ParseState) -> ParseResult<char> {
    let (start, _) = input.match_str_if(|c| c == '{', "BRACE")?;
    let (state, text) = start.match_str_until(|c| c == '}', "BRACE").map_inner(|s| s.trim())?;
    if text.len() > 6 {
        StopBecause::custom_error("Escape characters must be 0-6 characters", start.start_offset, state.start_offset)?
    }
    let mut digit: u32 = 0;
    for byte in text.as_bytes() {
        match hex_to_u8(*byte) {
            Some(d) => digit = digit * 16 + d as u32,
            None => StopBecause::custom_error("Escape characters must in 0-9a-fA-F", start.start_offset, state.start_offset)?,
        }
    }
    match char::from_u32(digit) {
        Some(c) => state.advance(1).finish(c),
        None => StopBecause::custom_error("Characters must not beyond U+10FFFF", start.start_offset, state.start_offset)?,
    }
}