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
157
158
159
160
161
162
163

use proc_macro::TokenStream;
use proc_macro2::Span;
use proc_macro_crate::FoundCrate;
use syn::{Attribute, Data, DeriveInput, Meta};

fn find_serde_crate() -> proc_macro2::TokenStream {
    match proc_macro_crate::crate_name("serde") {
        Ok(FoundCrate::Itself) => quote::quote!(crate),
        Ok(FoundCrate::Name(name)) => {
            let ident = syn::Ident::new(name.as_str(), Span::call_site());
            quote::quote!(::#ident)
        }
        Err(_) => {
            panic!("serde is a co-dependency of serde-split")
        }
    }
}

fn filter_attrs(attrs: &mut Vec<Attribute>, is_json: bool) {
    let (remove, replace) = if is_json {
        ("bin", "json")
    } else {
        ("json", "bin")
    };

    let mut current = 0;
    while current < attrs.len() {
        if attrs[current].path().is_ident(remove) {
            attrs.remove(current);
            continue;
        } else if attrs[current].path().is_ident(replace) {
            match &mut attrs[current].meta {
                Meta::Path(path) => *path = syn::parse_quote!(serde),
                Meta::List(list) => list.path = syn::parse_quote!(serde),
                Meta::NameValue(name_value) => name_value.path = syn::parse_quote!(serde),
            }
        }

        current += 1;
    }
}

fn filter_data(input: &mut DeriveInput, is_json: bool) {
    filter_attrs(&mut input.attrs, is_json);

    match &mut input.data {
        Data::Struct(data) => {
            data.fields
                .iter_mut()
                .for_each(|field| filter_attrs(&mut field.attrs, is_json));
        }
        Data::Enum(data) => {
            data.variants.iter_mut().for_each(|variant| {
                filter_attrs(&mut variant.attrs, is_json);
                variant
                    .fields
                    .iter_mut()
                    .for_each(|field| filter_attrs(&mut field.attrs, is_json));
            });
        }
        Data::Union(data) => {
            data.fields.named.iter_mut().for_each(|field| {
                filter_attrs(&mut field.attrs, is_json);
            });
        }
    }
}

#[proc_macro_derive(Serialize, attributes(json, bin, serde))]
pub fn derive_serialize(tokens: TokenStream) -> TokenStream {
    let input = syn::parse_macro_input!(tokens as syn::DeriveInput);

    let ident = input.ident.clone();

    let mut json = input.clone();
    let mut bin = input;

    filter_data(&mut json, true);
    filter_data(&mut bin, false);

    json.ident = quote::format_ident!("{}JsonImpl", ident);
    bin.ident = quote::format_ident!("{}BinaryImpl", ident);

    let json_ident = &json.ident;
    let bin_ident = &bin.ident;

    let ident_str = syn::LitStr::new(ident.to_string().as_str(), ident.span());

    let serde = find_serde_crate();

    quote::quote! {
        const _: () = {
            #[derive(#serde::Serialize)]
            #[serde(remote = #ident_str)]
            #json

            #[derive(#serde::Serialize)]
            #[serde(remote = #ident_str)]
            #bin

            impl #serde::Serialize for #ident {
                fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
                    where S: #serde::Serializer
                {
                    if serializer.is_human_readable() {
                        #json_ident::serialize(self, serializer)
                    } else {
                        #bin_ident::serialize(self, serializer)
                    }
                }
            }
        };
    }
    .into()
}

#[proc_macro_derive(Deserialize, attributes(json, bin, serde))]
pub fn derive_deserialize(tokens: TokenStream) -> TokenStream {
    let input = syn::parse_macro_input!(tokens as syn::DeriveInput);

    let ident = input.ident.clone();

    let mut json = input.clone();
    let mut bin = input;

    filter_data(&mut json, true);
    filter_data(&mut bin, true);

    json.ident = quote::format_ident!("{}JsonImpl", ident);
    bin.ident = quote::format_ident!("{}BinaryImpl", ident);

    let json_ident = &json.ident;
    let bin_ident = &bin.ident;

    let ident_str = syn::LitStr::new(ident.to_string().as_str(), ident.span());

    let serde = find_serde_crate();

    quote::quote! {
        const _: () = {
            #[derive(#serde::Deserialize)]
            #[serde(remote = #ident_str)]
            #json

            #[derive(#serde::Deserialize)]
            #[serde(remote = #ident_str)]
            #bin

            impl<'de> #serde::Deserialize<'de> for #ident {
                fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
                    where D: #serde::Deserializer<'de>
                {
                    if deserializer.is_human_readable() {
                        #json_ident::deserialize(deserializer)
                    } else {
                        #bin_ident::deserialize(deserializer)
                    }
                }
            }
        };
    }
    .into()
}