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use super::generate_fields;
use proc_macro2::{Ident, Literal, TokenStream};
use quote::quote;
use syn::{DataEnum, Variant};
fn variant_weight(variant: &Variant) -> Literal {
for attr in variant.attrs.iter() {
if attr.path.is_ident("weight") {
return attr
.parse_args::<Literal>()
.expect("expected literal for `#[weight(...)]`");
}
}
Literal::u64_suffixed(1)
}
pub fn generate(name: &Ident, ty: DataEnum) -> TokenStream {
let variant_weights = ty
.variants
.into_iter()
.enumerate()
.map(|(i, variant)| (i, variant_weight(&variant), variant));
let mut arms = TokenStream::new();
let mut arms_variant = TokenStream::new();
let mut arms_variant_name = TokenStream::new();
let mut num_variants: usize = 0;
let mut total_weight = quote! { 0 };
for (index, weight, variant) in variant_weights {
let variant_name = variant.ident;
arms.extend(quote! {
let start = end;
let end = start + #weight;
if start <= value && value < end {
return generate_random::GenerateRandomVariant::generate_random_variant(rng, #index);
}
});
let fields = generate_fields(variant.fields);
arms_variant.extend(quote! {
#index => Self::#variant_name #fields,
});
let variant_str = variant_name.to_string();
arms_variant_name.extend(quote! {
#index => #variant_str,
});
total_weight = quote! { #total_weight + #weight };
num_variants += 1;
}
quote! {
impl generate_random::GenerateRandom for #name {
fn generate_random<R: rand::Rng + ?Sized>(rng: &mut R) -> Self {
let total_weight = #total_weight;
let value = rng.gen_range(0..total_weight);
let end = 0;
#arms
unreachable!()
}
}
impl generate_random::GenerateRandomVariant for #name {
fn num_variants() -> usize {
#num_variants
}
fn variant_name(variant: usize) -> &'static str {
match variant {
#arms_variant_name
_ => "",
}
}
fn generate_random_variant<R: rand::Rng + ?Sized>(rng: &mut R, variant: usize) -> Self {
match variant {
#arms_variant
_ => generate_random::GenerateRandom::generate_random(rng),
}
}
}
}
}
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