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use proc_macro::TokenStream;
use quote::quote;
use syn::*;
fn parse_path(path: Path) -> String {
path.segments.first().unwrap().ident.to_string()
}
fn parse_lit(lit: Lit) -> String {
match lit {
Lit::Str(s) => s.value(),
Lit::ByteStr(s) => match String::from_utf8(s.value()) {
Ok(v) => v,
Err(e) => panic!("Invalid UTF-8 sequence: {}", e),
},
Lit::Int(i) => i.base10_digits().to_owned(),
Lit::Float(f) => f.base10_digits().to_owned(),
Lit::Bool(b) => b.value.to_string(),
Lit::Char(c) => c.value().to_string(),
Lit::Byte(b) => (b.value() as char).to_string(),
Lit::Verbatim(_) => panic!("Salak not support Verbatim"),
}
}
fn parse_attribute_prefix(attrs: &[Attribute]) -> Option<String> {
for attr in attrs {
if let Ok(Meta::List(list)) = attr.parse_meta() {
if !is_salak(&list) {
continue;
}
for m in list.nested {
if let NestedMeta::Meta(Meta::NameValue(nv)) = m {
if parse_path(nv.path) == "prefix" {
match nv.lit {
Lit::Str(s) => return Some(s.value()),
_ => panic!("Only support string"),
}
} else {
panic!("Only support prefix");
}
} else {
panic!("Only support prefix=\"xxx\"");
}
}
}
}
None
}
fn is_salak(list: &MetaList) -> bool {
if let Some(v) = list.path.segments.iter().next() {
return v.ident == "salak";
}
false
}
fn parse_field_attribute(attrs: Vec<Attribute>, name: &mut Ident) -> quote::__private::TokenStream {
let mut def = None;
let mut rename = None;
for attr in attrs {
if let Ok(Meta::List(list)) = attr.parse_meta() {
if !is_salak(&list) {
continue;
}
for m in list.nested {
if let NestedMeta::Meta(Meta::NameValue(nv)) = m {
match &parse_path(nv.path)[..] {
"default" => def = Some(parse_lit(nv.lit)),
"name" => rename = Some(parse_lit(nv.lit)),
_ => panic!("Only support default/name/required"),
}
} else {
panic!("Only support NestedMeta::Meta(Meta::NameValue)");
}
}
}
}
if let Some(rename) = rename {
*name = quote::format_ident!("{}", rename);
}
match def {
Some(def) => quote! {
Some(Property::S(#def))
},
_ => quote! {
None
},
}
}
fn derive_field(field: Field) -> quote::__private::TokenStream {
let name = field.ident.expect("Not possible");
let ty = field.ty;
let mut rename = name.clone();
let def = parse_field_attribute(field.attrs, &mut rename);
quote! {
#name: env.require_def::<#ty, &str>(key, stringify!(#rename), #def)?
}
}
fn derive_fields(fields: Fields) -> Vec<quote::__private::TokenStream> {
if let Fields::Named(fields) = fields {
let mut v = vec![];
for field in fields.named {
v.push(derive_field(field));
}
return v;
}
panic!("Only support named body");
}
fn derive_struct(name: &Ident, data: DataStruct) -> quote::__private::TokenStream {
let field = derive_fields(data.fields);
quote! {
impl FromEnvironment for #name {
fn from_env<'a>(
key: &mut Key<'a>,
val: Option<Property<'_>>,
env: &'a impl Environment,
) -> Result<Self, PropertyError> {
Ok(Self {
#(#field),*
})
}
}
}
}
fn derive_enum(type_name: &Ident, data: &DataEnum) -> quote::__private::TokenStream {
let mut vs = vec![];
for variant in &data.variants {
let lname = quote::format_ident!("{}", format!("{}", variant.ident).to_lowercase());
let name = &variant.ident;
let body = match variant.fields {
Fields::Unit => {
quote! {
stringify!(#lname) => Ok(#type_name::#name),
}
}
_ => panic!("Enum only support no field pattern."),
};
vs.push(body);
}
quote! {
impl EnumProperty for #type_name {
#[inline]
fn str_to_enum(val: &str) -> Result<#type_name, PropertyError>{
match &val.to_lowercase()[..] {
#(#vs)*
_ => Err(PropertyError::parse_fail("invalid enum value")),
}
}
}
}
}
#[proc_macro_derive(FromEnvironment, attributes(salak))]
pub fn from_env_derive(input: TokenStream) -> TokenStream {
let input: DeriveInput = parse_macro_input!(input as DeriveInput);
let name = input.ident;
let (head, body) = match input.data {
Data::Struct(d) => (
if let Some(prefix) = parse_attribute_prefix(&input.attrs) {
quote! {
impl DefaultSourceFromEnvironment for #name {
fn prefix() -> &'static str {
#prefix
}
}
}
} else {
quote! {}
},
derive_struct(&name, d),
),
Data::Enum(d) => (quote! {}, derive_enum(&name, &d)),
_ => panic!("union is not supported"),
};
TokenStream::from(quote! {
impl AutoDeriveFromEnvironment for #name {}
#head
#body
})
}