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

extern crate proc_macro;

use quote::quote;
use std::collections::HashMap;
use syn::{Ident, Token, Type};

struct TranslationParameters {
    pub arguments: Vec<(Ident, Type)>,
}

impl Default for TranslationParameters {
    fn default() -> Self {
        TranslationParameters {
            arguments: Vec::new(),
        }
    }
}

impl syn::parse::Parse for TranslationParameters {
    fn parse(input: syn::parse::ParseStream) -> syn::Result<Self> {
        let mut arguments = Vec::new();
        while !input.is_empty() {
            let param_name = input.parse::<syn::Ident>()?;
            input.parse::<Token![:]>()?;
            let type_name = input.parse::<syn::Type>()?;
            arguments.push((param_name, type_name));

            if input.peek(Token![,]) {
                input.parse::<Token![,]>().unwrap();
            }
        }
        Ok(TranslationParameters { arguments })
    }
}

struct TranslationParse {
    pub translation_keys: HashMap<Ident, TranslationParameters>,
}

impl syn::parse::Parse for TranslationParse {
    fn parse(input: syn::parse::ParseStream) -> syn::Result<Self> {
        let mut translation_keys = HashMap::new();
        while !input.is_empty() {
            let next_translation = input.parse::<syn::Ident>()?;

            if input.peek(Token![,]) || input.is_empty() {
                translation_keys.insert(next_translation, TranslationParameters::default());
            } else {
                let content;
                syn::parenthesized!(content in input);
                translation_keys
                    .insert(next_translation, content.parse::<TranslationParameters>()?);
            }

            if input.peek(Token![,]) {
                input.parse::<Token![,]>().unwrap();
            }
        }

        Ok(TranslationParse { translation_keys })
    }
}

#[proc_macro]
pub fn generate_translation(input: proc_macro::TokenStream) -> proc_macro::TokenStream {
    let translation_parse = syn::parse_macro_input!(input as TranslationParse);

    let mut str_gen = quote! {};
    let mut fn_gen = quote! {};

    for (translation_key, translation_arguments) in translation_parse.translation_keys {
        // generates a unique field which is stored internally in the struct
        let internal_field_name = Ident::new(
            &(translation_key.to_string() + "_implementation_name_plz_dont_use_this_name_plz"),
            proc_macro2::Span::call_site(),
        );
        let external_name = translation_key.to_string();

        // ... but we still want to ser/deser using the normal name!
        let serde_rename_field = if cfg!(feature = "serde") {
            quote! {
                #[serde(rename = #external_name)]
            }
        } else {
            quote! {}
        };

        str_gen = quote! {
            #str_gen
            #serde_rename_field
            #internal_field_name: String,
        };

        let mut param_decl = quote! { &self, };
        let mut param_call = quote! {};

        // We branch here because returning a Result<T, E> makes no sense if the translation is only a string
        // and not a formatting
        fn_gen = if translation_arguments.arguments.is_empty() {
            quote! {
                #fn_gen

                pub fn #translation_key ( #param_decl ) -> &str {
                    &self.#internal_field_name
                }
            }
        } else {
            for (id, ty) in translation_arguments.arguments {
                param_decl = quote! {
                    #param_decl
                    #id: #ty,
                };

                param_call = quote! {
                    #param_call
                    params.insert(stringify!(#id).to_owned(), #id.to_string());
                };
            }
            quote! {
                #fn_gen

                pub fn #translation_key ( #param_decl ) -> Result<String, strfmt::FmtError> {
                    use std::collections::HashMap;
                    let mut params : HashMap<String, String> = HashMap::new();
                    #param_call
                    strfmt::strfmt(&self.#internal_field_name, &params)
                }
            }
        };
    }

    let serde_derive = if cfg!(feature = "serde") {
        quote! {
         #[derive(serde::Serialize, serde::Deserialize)]
        }
    } else {
        quote! {}
    };

    let final_generated_struct = quote! {
        #serde_derive
        pub struct TranslationProvider {
            #str_gen
        }

        impl TranslationProvider {
            #fn_gen
        }
    };

    let final_output = quote! {
        #final_generated_struct

        impl TranslationProvider {
            fn generated_code() -> String {
                stringify!(#final_generated_struct).to_owned()
            }
        }
    };

    proc_macro::TokenStream::from(final_output)
}