78 lines
2.1 KiB
Rust
78 lines
2.1 KiB
Rust
/*
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* SPDX-FileCopyrightText: 2020 Stalwart Labs LLC <hello@stalw.art>
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*
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* SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-SEL
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*/
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use proc_macro::TokenStream;
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use quote::quote;
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use syn::{Data, DeriveInput, parse_macro_input};
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#[proc_macro_derive(EnumMethods)]
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pub fn enum_id(input: TokenStream) -> TokenStream {
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let input = parse_macro_input!(input as DeriveInput);
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let name = &input.ident;
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let variants = match input.data {
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Data::Enum(ref data) => &data.variants,
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_ => panic!("EnumMethods only works on enums"),
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};
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let variant_count = variants.len();
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let variant_names: Vec<_> = variants.iter().map(|v| &v.ident).collect();
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let variant_ids: Vec<u32> = (0..(variant_count as u32)).collect();
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let snake_case_names: Vec<String> = variant_names
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.iter()
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.map(|name| to_snake_case(&name.to_string()))
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.collect();
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let expanded = quote! {
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impl #name {
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pub const COUNT: usize = #variant_count;
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pub const fn id(&self) -> u32 {
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match self {
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#(#name::#variant_names => #variant_ids,)*
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}
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}
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pub fn from_id(id: u32) -> Option<Self> {
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match id {
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#(#variant_ids => Some(#name::#variant_names),)*
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_ => None,
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}
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}
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pub fn name(&self) -> &'static str {
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match self {
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#(#name::#variant_names => #snake_case_names,)*
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}
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}
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pub fn from_name(name: &str) -> Option<Self> {
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match name {
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#(#snake_case_names => Some(#name::#variant_names),)*
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_ => None,
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}
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}
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}
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};
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TokenStream::from(expanded)
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}
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fn to_snake_case(s: &str) -> String {
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let mut result = String::new();
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for (i, ch) in s.char_indices() {
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if ch.is_uppercase() {
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if i > 0 {
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result.push('-');
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}
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result.push(ch.to_ascii_lowercase());
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} else {
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result.push(ch);
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}
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}
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result
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}
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