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use proc_macro::TokenStream;
use quote::quote;
use syn::{Data, DeriveInput, Error, Expr, Field, Fields, Meta, parse_macro_input};
fn get_field_attrs<'a>(field: &'a Field) -> (bool, Option<&'a Expr>) {
let mut default_value = None;
let mut is_optional = false;
for attr in &field.attrs {
match &attr.meta {
Meta::NameValue(nv) => {
let Some(attr_ident) = nv.path.get_ident() else {
continue;
};
if attr_ident != "default_value" {
continue;
}
default_value = Some(&nv.value);
break;
},
Meta::Path(path) => {
let Some(ident) = path.get_ident() else {
continue;
};
if ident == "optional" {
is_optional = true;
break;
}
}
_ => ()
}
}
(is_optional, default_value)
}
#[proc_macro_derive(Cryptic, attributes(default_value, optional))]
/// Allows structs and enums to automatically be constructed from a
/// parsed crypt file.
///
/// Properties can additionally be given default values (via `default_value`) or
/// automatically be set to [None] when not found (via `optional`).
pub fn cryptic_derived(input: TokenStream) -> TokenStream {
let input = parse_macro_input!(input as DeriveInput);
let obj_name = input.ident;
let implementation = match &input.data {
Data::Struct(data_struct) => {
match &data_struct.fields {
Fields::Named(named_fields) => {
let field_construction = named_fields.named.iter().map(|f| {
let (is_optional, default_value) = get_field_attrs(f);
let ident = f.ident.as_ref().unwrap();
match default_value {
Some(def) => {
quote! {
#ident: mapping
.remove(stringify!(#ident))
.map(|i|
::crypt_configs::Cryptic::cryptic(i))
.unwrap_or(Ok(match #def.parse() { Ok(v) => v, Err(_) => panic!("Failed to parse the default value for {}", stringify!(#ident)) })
)?,
}
}
None => {
if is_optional {
quote! {
#ident: match mapping.remove(stringify!(#ident)) {
Some(v) => ::crypt_configs::Cryptic::cryptic(v)?,
None => None,
},
}
} else {
quote! {
#ident: match mapping.remove(stringify!(#ident)) {
Some(v) => ::crypt_configs::Cryptic::cryptic(v)?,
None => return Err(::crypt_configs::CryptError::cannot_find_ident(stringify!(#ident))),
},
}
}
}
}
});
quote! {
let mut mapping: ::std::collections::HashMap<String, ::crypt_configs::TracedObject> = ::crypt_configs::Cryptic::cryptic(object)?;
Ok(Self {
#(#field_construction)*
})
}
},
Fields::Unnamed(unnammed_fields) => {
let field_construction = unnammed_fields.unnamed.iter().map(|f| {
let (is_optional, default_value) = get_field_attrs(f);
match default_value {
Some(def) => {
quote! {
match it.next() {
Some(v) => ::crypt_configs::Cryptic::cryptic(v)?,
None => match #def.parse() { Ok(v) => v, Err(_) => panic!("Failed to parse default value") }
},
}
}
None => {
if is_optional {
quote! {
match it.next() {
Some(v) => ::crypt_configs::Cryptic::cryptic(v)?,
None => None,
},
}
} else {
quote! {
match it.next() {
Some(v) => ::crypt_configs::Cryptic::cryptic(v)?,
None => return Err(::crypt_configs::CryptError::not_enough_items())
},
}
}
}
}
});
quote! {
let items: Vec<::crypt_configs::TracedObject> = Cryptic::cryptic(object)?;
let mut it = items.into_iter();
Ok(Self(
#(#field_construction)*
))
}
},
Fields::Unit =>
return TokenStream::from(Error::new(obj_name.span(), "Struct must have at least one attribute").to_compile_error())
}
},
Data::Enum(data_enum) => {
let variant_bodies = data_enum.variants.iter().map(|var| {
let var_ident = &var.ident;
match &var.fields {
Fields::Named(named_fields) => {
let field_construction = named_fields.named.iter().map(|f| {
let (is_optional, default_value) = get_field_attrs(f);
let ident = f.ident.as_ref().unwrap();
match default_value {
Some(def) => {
quote! {
#ident: mapping
.remove(stringify!(#ident))
.map(|i|
::crypt_configs::Cryptic::cryptic(i))
.unwrap_or(Ok(match #def.parse() { Ok(v) => v, Err(_) => panic!("Failed to parse the default value for {}", stringify!(#ident)) })
)?,
}
}
None => {
if is_optional {
quote! {
#ident: match mapping.remove(stringify!(#ident)) {
Some(v) => ::crypt_configs::Cryptic::cryptic(v)?,
None => None,
},
}
} else {
quote! {
#ident: match mapping.remove(stringify!(#ident)) {
Some(v) => ::crypt_configs::Cryptic::cryptic(v)?,
None => return Err(::crypt_configs::CryptError::cannot_find_ident(stringify!(#ident))),
},
}
}
}
}
});
quote! {
{
let mut mapping: ::std::collections::HashMap<String, ::crypt_configs::TracedObject> = ::crypt_configs::Cryptic::cryptic(object)?;
Ok(Self::#var_ident {
#(#field_construction)*
})
}
}
},
Fields::Unnamed(unnammed_fields) => {
let field_construction = unnammed_fields.unnamed.iter().map(|f| {
let (is_optional, default_value) = get_field_attrs(f);
match default_value {
Some(def) => {
quote! {
match it.next() {
Some(v) => ::crypt_configs::Cryptic::cryptic(v)?,
None => match #def.parse() { Ok(v) => v, Err(_) => panic!("Failed to parse default value") }
},
}
}
None => {
if is_optional {
quote! {
match it.next() {
Some(v) => ::crypt_configs::Cryptic::cryptic(v)?,
None => None,
},
}
} else {
quote! {
match it.next() {
Some(v) => ::crypt_configs::Cryptic::cryptic(v)?,
None => return Err(::crypt_configs::CryptError::not_enough_items())
},
}
}
}
}
});
quote! {
{
let items: Vec<::crypt_configs::TracedObject> = Cryptic::cryptic(object)?;
let mut it = items.into_iter();
Ok(Self::#var_ident(
#(#field_construction)*
))
}
}
},
Fields::Unit => quote! {
Ok(Self::#var_ident),
}
}
});
let variant_patterns = data_enum.variants.iter().map(|var| {
let var_ident = &var.ident;
quote! {stringify!(#var_ident)}
});
quote! {
let obj: ::crypt_configs::Tagged<String, ::crypt_configs::TracedObject> = ::crypt_configs::Cryptic::cryptic(object)?;
let object = obj.object;
match obj.tag.as_str() {
#(
#variant_patterns => #variant_bodies
)*
_ => Err(::crypt_configs::CryptError::invalid_enum_variant(obj.tag))
}
}
},
Data::Union(_) => {
return TokenStream::from(Error::new(obj_name.span(), "Only structs and enums can derive Cryptic").to_compile_error())
}
};
TokenStream::from(quote! {
impl ::crypt_configs::Cryptic for #obj_name {
fn cryptic(object: ::crypt_configs::TracedObject) -> Result<Self, ::crypt_configs::CryptError> {
#implementation
}
}
})
}