ranty 1.0.0

The Ranty procedural templating language
Documentation 
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use super::lexer::RantyToken;
use crate::InternalString;
use logos::*;
use std::ops::Range;

#[derive(Clone)]
pub struct RantyTokenReader<'source> {
    lexer: Lexer<'source, RantyToken>,
    peeked: Option<(RantyToken, Range<usize>)>,
}

impl<'source> RantyTokenReader<'source> {
    pub fn new(src: &'source str) -> Self {
        Self {
            lexer: RantyToken::lexer(src),
            peeked: None,
        }
    }

    pub fn next(&mut self) -> Option<(RantyToken, Range<usize>)> {
        // Consume any peeked token before iterating lexer again
        self.peeked
            .take()
            .or_else(|| self.lexer.next().map(|token| (token, self.lexer.span())))
    }

    pub fn skip_one(&mut self) {
        self.next();
    }

    // Consumes the next token if it satisfies the predicate and returns a bool indicating whether any token was eaten.
    pub fn eat_where<F: FnOnce(Option<&(RantyToken, Range<usize>)>) -> bool>(
        &mut self,
        predicate: F,
    ) -> bool {
        if predicate(self.peek()) {
            self.skip_one();
            return true;
        }
        false
    }

    /// Consumes the next token if it's equal to the specified token and returns a bool indicating whether any token was eaten.
    pub fn eat(&mut self, token: RantyToken) -> bool {
        if let Some((peeked, _span)) = self.peek() {
            if peeked.eq(&token) {
                self.skip_one();
                return true;
            }
        }
        false
    }

    pub fn eat_kw(&mut self, kwname: &str) -> bool {
        self.eat_where(|t| {
            if let Some((RantyToken::Keyword(kw), _)) = t.as_ref() {
                return kw.name.as_str() == kwname;
            }
            false
        })
    }

    // Consumes the next token if it satisfies the predicate and returns it if the predicate was satisfied; otherwise, returns `None`.
    pub fn take_where<F: FnOnce(Option<&(RantyToken, Range<usize>)>) -> bool>(
        &mut self,
        predicate: F,
    ) -> Option<(RantyToken, Range<usize>)> {
        if predicate(self.peek()) {
            self.next()
        } else {
            None
        }
    }

    /// Gets the last token string that was read.
    pub fn last_token_string(&self) -> InternalString {
        InternalString::from(self.lexer.slice())
    }

    /// Gets the next non-whitespace token.
    pub fn next_solid(&mut self) -> Option<(RantyToken, Range<usize>)> {
        loop {
            match self.next() {
                Some((RantyToken::Whitespace, _)) => continue,
                Some((token, span)) => return Some((token, span)),
                None => return None,
            }
        }
    }

    /// Skips past whitespace tokens.
    pub fn skip_ws(&mut self) {
        while let Some((RantyToken::Whitespace, _)) = self.peek() {
            self.next();
        }
    }

    /// Gets the starting position of the most recently read token.
    pub fn last_token_pos(&self) -> usize {
        self.lexer.span().start
    }

    /// Gets the span of the most recently read token.
    pub fn last_token_span(&self) -> Range<usize> {
        self.lexer.span()
    }

    /// Returns a reference to the next token without consuming it.
    pub fn peek(&mut self) -> Option<&(RantyToken, Range<usize>)> {
        // If a peek was already performed, return a reference to it
        if self.peeked.is_some() {
            return self.peeked.as_ref();
        }

        // If no previous peek was performed for the current iteration, iterate, store, and return reference to token
        let token = self.next();
        self.peeked = token;
        self.peeked.as_ref()
    }
}