use quote::quote;

use crate::reflection::field::{generate as generate_field, ReflectionFieldGenOptions};
use crate::util::find_engine_crate_path;

pub fn generate(input: syn::ItemStruct) -> proc_macro2::TokenStream
{
    let engine_crate_path = find_engine_crate_path().unwrap();

    let input_ident = input.ident;

    let (impl_generics, type_generics, where_clause) = input.generics.split_for_impl();

    let fields = input
        .fields
        .into_iter()
        .enumerate()
        .map(|(field_index, field)| {
            generate_field(
                &field,
                field_index,
                &engine_crate_path,
                ReflectionFieldGenOptions {
                    field_vis_override: None,
                    gen_get_byte_offset: &|field| {
                        if let Some(field_ident) = &field.ident {
                            quote! { std::mem::offset_of!(Self, #field_ident) }
                        } else {
                            quote! { std::mem::offset_of!(Self, #field_index) }
                        }
                    },
                },
            )
        });

    quote! {
        unsafe impl #impl_generics #engine_crate_path::reflection::Reflection for
            #input_ident #type_generics #where_clause
        {
            const TYPE_REFLECTION: &#engine_crate_path::reflection::Type =
                &const {
                    #engine_crate_path::reflection::Type::Struct(
                        #engine_crate_path::reflection::Struct {
                            fields: &[
                                #(#fields),*
                            ]
                        }
                    )
                };
        }
    }
}