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

use syn::ext::IdentExt as _;
use syn::parse::{Parse, ParseStream};
use syn::punctuated::Punctuated;

use crate::ast;

mod kw {
    syn::custom_keyword!(DOCTYPE);
    syn::custom_keyword!(doctype);
    syn::custom_keyword!(html);
}

impl Parse for ast::DashIdent {
    fn parse(input: ParseStream) -> syn::Result<Self> {
        // Parse a non-empty sequence of identifiers separated by dashes.
        Ok(Self(
            Punctuated::<syn::Ident, syn::Token![-]>::parse_separated_nonempty_with(
                input,
                syn::Ident::parse_any,
            )?,
        ))
    }
}

impl Parse for ast::Doctype {
    fn parse(input: ParseStream) -> syn::Result<Self> {
        input.parse::<syn::Token![<]>()?;
        input.parse::<syn::Token![!]>()?;
        if input.peek(kw::doctype) {
            input.parse::<kw::doctype>()?;
        } else {
            input.parse::<kw::DOCTYPE>()?;
        }
        input.parse::<kw::html>()?;
        input.parse::<syn::Token![>]>()?;

        Ok(Self)
    }
}

impl Parse for ast::Tag {
    fn parse(input: ParseStream) -> syn::Result<Self> {
        input.parse::<syn::Token![<]>()?;

        if input.peek(syn::Token![/]) {
            input.parse::<syn::Token![/]>()?;
            let name = input.parse()?;
            input.parse::<syn::Token![>]>()?;

            return Ok(Self::End { name });
        }

        let name = input.parse()?;

        let mut attributes = Vec::new();
        while !(input.peek(syn::Token![>])
            || (input.peek(syn::Token![/]) && input.peek2(syn::Token![>])))
        {
            attributes.push(input.parse()?);
        }

        let self_closing = input.parse::<Option<syn::Token![/]>>()?.is_some();

        input.parse::<syn::Token![>]>()?;

        Ok(Self::Start {
            name,
            attributes,
            self_closing,
        })
    }
}

impl Parse for ast::Attr {
    fn parse(input: ParseStream) -> syn::Result<Self> {
        let name = input.parse()?;
        input.parse::<syn::Token![=]>()?;
        let value = input.parse()?;

        Ok(Self { name, value })
    }
}

impl Parse for ast::Value {
    fn parse(input: ParseStream) -> syn::Result<Self> {
        let lookahead = input.lookahead1();
        if lookahead.peek(syn::LitStr) {
            Ok(Self::Text(input.parse()?))
        } else if lookahead.peek(syn::token::Brace) {
            let content;
            syn::braced!(content in input);

            Ok(Self::Braced(content.parse()?))
        } else {
            Err(lookahead.error())
        }
    }
}

impl Parse for ast::Segment {
    fn parse(input: ParseStream) -> syn::Result<Self> {
        let lookahead = input.lookahead1();
        if lookahead.peek(syn::Token![<])
            && input.peek2(syn::Token![!])
            && (input.peek3(kw::DOCTYPE) || input.peek3(kw::doctype))
        {
            Ok(Self::Doctype(input.parse()?))
        } else if lookahead.peek(syn::Token![<]) {
            Ok(Self::Tag(input.parse()?))
        } else if lookahead.peek(syn::LitStr)
            || lookahead.peek(syn::token::Brace)
        {
            Ok(Self::Value(input.parse()?))
        } else {
            Err(lookahead.error())
        }
    }
}

#[cfg(test)]
mod tests {
    use quote::quote;

    use super::*;

    #[test]
    fn parse_doctype() {
        syn::parse2::<ast::Doctype>(quote! {
            <!DOCTYPE html>
        })
        .unwrap();

        syn::parse2::<ast::Doctype>(quote! {
            <!doctype html>
        })
        .unwrap();
    }
}