simdnbt/simdnbt-derive/src/lib.rs

mod attrs;

use attrs::{parse_field_attrs, parse_unit_attrs};
use quote::quote;
use syn::{parse_macro_input, DeriveInput};

#[proc_macro_derive(Deserialize, attributes(simdnbt))]
pub fn deserialize_derive(input: proc_macro::TokenStream) -> proc_macro::TokenStream {
    let input = parse_macro_input!(input as DeriveInput);

    let ident = input.ident;

    let mut field_deserializers = Vec::<proc_macro2::TokenStream>::new();

    match input.data {
        syn::Data::Struct(syn::DataStruct { fields, .. }) => match fields {
            syn::Fields::Named(syn::FieldsNamed { named, .. }) => {
                for field in named {
                    let struct_field_name = field.ident.unwrap();

                    let mut field_attrs = parse_field_attrs(&field.attrs);

                    let field_name = field_attrs
                        .rename
                        .take()
                        .unwrap_or_else(|| struct_field_name.to_string());

                    if field_attrs.flatten {
                        field_deserializers.push(quote! {
                            #struct_field_name: simdnbt::Deserialize::from_compound(nbt)?,
                        })
                    } else {
                        let debug_ident = format!("{ident}::{struct_field_name}");

                        field_deserializers.push(quote! {
                            #struct_field_name: simdnbt::FromNbtTag::from_optional_nbt_tag(
                                nbt.get(#field_name)
                            )?.ok_or(simdnbt::DeserializeError::MismatchedFieldType(#debug_ident.to_owned()))?
                        });
                    }
                }
            }
            syn::Fields::Unnamed(_) => todo!(),
            syn::Fields::Unit => todo!(),
        },
        syn::Data::Enum(_) => todo!(),
        syn::Data::Union(_) => todo!(),
    }

    let generics = input.generics;
    let where_clause = &generics.where_clause;

    let struct_attrs = attrs::parse_struct_attrs(&input.attrs);

    let extra_checks = if struct_attrs.deny_unknown_fields {
        quote! {
            if !nbt.is_empty() {
                return Err(simdnbt::DeserializeError::UnknownField(nbt.keys().next().unwrap().to_string()));
            }
        }
    } else {
        quote! {}
    };

    let output = quote! {
        impl #generics simdnbt::Deserialize for #ident #generics #where_clause {
            fn from_compound(mut nbt: simdnbt::borrow::NbtCompound) -> Result<Self, simdnbt::DeserializeError> {
                let value = Self {
                    #(#field_deserializers),*
                };
                #extra_checks
                Ok(value)
            }
        }
    };

    output.into()
}

#[proc_macro_derive(Serialize, attributes(simdnbt))]
pub fn serialize_derive(input: proc_macro::TokenStream) -> proc_macro::TokenStream {
    let input = parse_macro_input!(input as DeriveInput);

    let ident = input.ident;

    let mut field_serializers = Vec::<proc_macro2::TokenStream>::new();

    match input.data {
        syn::Data::Struct(syn::DataStruct { fields, .. }) => match fields {
            syn::Fields::Named(syn::FieldsNamed { named, .. }) => {
                for field in named {
                    let struct_field_name = field.ident.unwrap();

                    let mut field_attrs = parse_field_attrs(&field.attrs);

                    let field_name = field_attrs
                        .rename
                        .take()
                        .unwrap_or_else(|| struct_field_name.to_string());

                    field_serializers.push(quote! {
                        if let Some(item) = simdnbt::ToNbtTag::to_optional_nbt_tag(self.#struct_field_name) {
                            nbt.insert(#field_name, item);
                        }
                    });
                }
            }
            syn::Fields::Unnamed(_) => todo!(),
            syn::Fields::Unit => todo!(),
        },
        syn::Data::Enum(_) => todo!(),
        syn::Data::Union(_) => todo!(),
    }

    let generics = input.generics;
    let where_clause = &generics.where_clause;

    let output = quote! {
        impl #generics simdnbt::Serialize for #ident #generics #where_clause {
            fn to_compound(self) -> simdnbt::owned::NbtCompound {
                let mut nbt = simdnbt::owned::NbtCompound::new();
                #(#field_serializers)*
                nbt
            }
        }
    };

    output.into()
}

#[proc_macro_derive(FromNbtTag, attributes(simdnbt))]
pub fn from_nbt_tag_derive(input: proc_macro::TokenStream) -> proc_macro::TokenStream {
    let input = parse_macro_input!(input as DeriveInput);

    let ident = input.ident;

    let mut matchers = Vec::<proc_macro2::TokenStream>::new();

    match input.data {
        syn::Data::Struct(_) => panic!("Use #[derive(Deserialize)] instead"),
        syn::Data::Enum(syn::DataEnum { variants, .. }) => {
            for variant in variants {
                match variant.fields {
                    syn::Fields::Named(_) => todo!(),
                    syn::Fields::Unnamed(_) => todo!(),
                    syn::Fields::Unit => {
                        let enum_variant_name = variant.ident;

                        let mut unit_attrs = parse_unit_attrs(&variant.attrs);

                        let variant_name = unit_attrs
                            .rename
                            .take()
                            .unwrap_or_else(|| enum_variant_name.to_string());

                        matchers.push(quote! {
                            #variant_name => Some(Self::#enum_variant_name),
                        });
                    }
                }
            }
        }
        syn::Data::Union(_) => todo!(),
    }

    let generics = input.generics;
    let where_clause = &generics.where_clause;

    let output = quote! {
        impl #generics simdnbt::FromNbtTag for #ident #generics #where_clause {
            fn from_nbt_tag(tag: simdnbt::borrow::NbtTag) -> Option<Self> {
                match tag.string()?.to_str().as_ref() {
                    #(#matchers)*
                    _ => None,
                }
            }
        }
    };

    output.into()
}

#[proc_macro_derive(ToNbtTag, attributes(simdnbt))]
pub fn to_nbt_tag_derive(input: proc_macro::TokenStream) -> proc_macro::TokenStream {
    let input = parse_macro_input!(input as DeriveInput);

    let ident = input.ident;

    let mut field_matchers = Vec::<proc_macro2::TokenStream>::new();

    match input.data {
        syn::Data::Struct(_) => panic!("Use #[derive(Serialize)] instead"),
        syn::Data::Enum(syn::DataEnum { variants, .. }) => {
            for variant in variants {
                match variant.fields {
                    syn::Fields::Named(_) => todo!(),
                    syn::Fields::Unnamed(_) => todo!(),
                    syn::Fields::Unit => {
                        let enum_variant_name = variant.ident;

                        let mut unit_attrs = parse_unit_attrs(&variant.attrs);

                        let variant_name = unit_attrs
                            .rename
                            .take()
                            .unwrap_or_else(|| enum_variant_name.to_string());

                        field_matchers.push(quote! {
                            Self::#enum_variant_name => simdnbt::owned::NbtTag::String(#variant_name.into()),
                        });
                    }
                }
            }
        }
        syn::Data::Union(_) => todo!(),
    }

    let generics = input.generics;
    let where_clause = &generics.where_clause;

    let output = quote! {
        impl #generics simdnbt::ToNbtTag for #ident #generics #where_clause {
            fn to_nbt_tag(self) -> simdnbt::owned::NbtTag {
                match self {
                    #(#field_matchers)*
                }
            }
        }
    };

    output.into()
}