1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156

use crate::error::Error;
use crate::prelude::{Delimiter, Group, Ident, Punct, TokenTree};
use std::iter::Peekable;

pub fn assume_group(t: Option<TokenTree>) -> Group {
    match t {
        Some(TokenTree::Group(group)) => group,
        _ => unreachable!(),
    }
}
pub fn assume_ident(t: Option<TokenTree>) -> Ident {
    match t {
        Some(TokenTree::Ident(ident)) => ident,
        _ => unreachable!(),
    }
}
pub fn assume_punct(t: Option<TokenTree>, punct: char) -> Punct {
    match t {
        Some(TokenTree::Punct(p)) => {
            debug_assert_eq!(punct, p.as_char());
            p
        }
        _ => unreachable!(),
    }
}

pub fn consume_ident(input: &mut Peekable<impl Iterator<Item = TokenTree>>) -> Option<Ident> {
    match input.peek() {
        Some(TokenTree::Ident(_)) => Some(super::utils::assume_ident(input.next())),
        Some(TokenTree::Group(group)) => {
            // When calling from a macro_rules!, sometimes an ident is defined as :
            // Group { delimiter: None, stream: TokenStream [Ident] }
            let mut stream = group.stream().into_iter();
            if let Some(TokenTree::Ident(i)) = stream.next() {
                if stream.next().is_none() {
                    let _ = input.next();
                    return Some(i);
                }
            }
            None
        }
        _ => None,
    }
}

pub fn consume_punct_if(
    input: &mut Peekable<impl Iterator<Item = TokenTree>>,
    punct: char,
) -> Option<Punct> {
    if let Some(TokenTree::Punct(p)) = input.peek() {
        if p.as_char() == punct {
            match input.next() {
                Some(TokenTree::Punct(p)) => return Some(p),
                _ => unreachable!(),
            }
        }
    }
    None
}

#[cfg(test)]
pub fn ident_eq(ident: &Ident, text: &str) -> bool {
    ident == text
}

#[cfg(not(test))]
pub fn ident_eq(ident: &Ident, text: &str) -> bool {
    ident.to_string() == text
}

fn check_if_arrow(tokens: &[TokenTree], punct: &Punct) -> bool {
    if punct.as_char() == '>' {
        if let Some(TokenTree::Punct(previous_punct)) = tokens.last() {
            if previous_punct.as_char() == '-' {
                return true;
            }
        }
    }
    false
}

const OPEN_BRACKETS: &[char] = &['<', '(', '[', '{'];
const CLOSING_BRACKETS: &[char] = &['>', ')', ']', '}'];
const BRACKET_DELIMITER: &[Option<Delimiter>] = &[
    None,
    Some(Delimiter::Parenthesis),
    Some(Delimiter::Bracket),
    Some(Delimiter::Brace),
];

pub fn read_tokens_until_punct(
    input: &mut Peekable<impl Iterator<Item = TokenTree>>,
    expected_puncts: &[char],
) -> Result<Vec<TokenTree>, Error> {
    let mut result = Vec::new();
    let mut open_brackets = Vec::<char>::new();
    'outer: loop {
        match input.peek() {
            Some(TokenTree::Punct(punct)) => {
                if check_if_arrow(&result, punct) {
                    // do nothing
                } else if OPEN_BRACKETS.contains(&punct.as_char()) {
                    open_brackets.push(punct.as_char());
                } else if let Some(index) =
                    CLOSING_BRACKETS.iter().position(|c| c == &punct.as_char())
                {
                    let last_bracket = match open_brackets.pop() {
                        Some(bracket) => bracket,
                        None => {
                            if expected_puncts.contains(&punct.as_char()) {
                                break;
                            }
                            return Err(Error::InvalidRustSyntax {
                                span: punct.span(),
                                expected: format!(
                                    "one of {:?}, got '{}'",
                                    expected_puncts,
                                    punct.as_char()
                                ),
                            });
                        }
                    };
                    let expected = OPEN_BRACKETS[index];
                    assert_eq!(
                        expected,
                        last_bracket,
                        "Unexpected closing bracket: found {}, expected {}",
                        punct.as_char(),
                        expected
                    );
                } else if expected_puncts.contains(&punct.as_char()) && open_brackets.is_empty() {
                    break;
                }
                result.push(input.next().unwrap());
            }
            Some(TokenTree::Group(g)) if open_brackets.is_empty() => {
                for punct in expected_puncts {
                    if let Some(idx) = OPEN_BRACKETS.iter().position(|c| c == punct) {
                        if let Some(delim) = BRACKET_DELIMITER[idx] {
                            if delim == g.delimiter() {
                                // we need to split on this delimiter
                                break 'outer;
                            }
                        }
                    }
                }
                result.push(input.next().unwrap());
            }
            Some(_) => result.push(input.next().unwrap()),
            None => {
                break;
            }
        }
    }
    Ok(result)
}