kash_macros 0.1.0

Function and method cache and memoization
Documentation 
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use super::macro_args::MacroArgs;
use crate::common::{gen_cache_ident, get_input_names, get_input_types, make_cache_key_type};
use crate::io_kash::{
    gen_cache_create, gen_return_cache_block, gen_set_cache_block, gen_set_return_block,
    gen_use_trait,
};
use proc_macro2::TokenStream;
use quote::{quote, ToTokens};
use syn::{parse_str, ExprClosure, Ident, ItemFn};

#[derive(Debug, Clone)]
pub struct CacheFn<'a> {
    input: &'a ItemFn,
    args: &'a MacroArgs,
}

impl<'a> CacheFn<'a> {
    pub fn new(input: &'a ItemFn, args: &'a MacroArgs) -> Self {
        Self { input, args }
    }
}

impl ToTokens for CacheFn<'_> {
    fn to_tokens(&self, tokens: &mut TokenStream) {
        let signature = &self.input.sig;
        let fn_ident = &signature.ident;
        let asyncness = &signature.asyncness;
        let cache_fn_ident_doc = format!("Caches the function [`{}`].", fn_ident);
        let attributes = &self.input.attrs;
        let visibility = &self.input.vis;
        let inputs = &self.input.sig.inputs;

        let (_, without_self_types) = get_input_types(inputs);
        let (_, without_self_names) = get_input_names(inputs);

        let fn_cache_ident = Ident::new(&format!("{}_get_cache_ident", fn_ident), fn_ident.span());
        let cache_ident = gen_cache_ident(&self.args.name, fn_ident);

        let call_prefix = if self.args.in_impl {
            quote! { Self:: }
        } else {
            quote! {}
        };
        let no_cache_fn_ident = Ident::new(&format!("{}_no_cache", fn_ident), fn_ident.span());

        let init_cache_ident = if self.args.in_impl {
            quote! {
                &#call_prefix #fn_cache_ident()
            }
        } else {
            quote! {
                &#call_prefix #cache_ident
            }
        };

        let map_error = &self.args.map_error;
        let map_error =
            parse_str::<ExprClosure>(map_error).expect("unable to parse map_error block");
        let (_, key_convert_block) = make_cache_key_type(
            &self.args.convert,
            &self.args.key,
            without_self_types,
            &without_self_names,
        );
        let cache_name = cache_ident.to_string();

        let return_cache_block = gen_return_cache_block(self.args.wrap_return);
        let set_cache_block =
            gen_set_cache_block(self.args.wrap_return, self.args.disk, asyncness, &map_error);

        let cache_create = gen_cache_create(self.args, asyncness, &cache_ident, cache_name);

        let init = if asyncness.is_some() {
            quote! { let init = || async { #cache_create }; }
        } else {
            quote! {}
        };
        let use_trait = gen_use_trait(asyncness, self.args.disk);
        let async_cache_get_return = if asyncness.is_some() && !self.args.disk {
            quote! {
                if let Some(result) = cache.get(&key).await.map_err(#map_error)? {
                    #return_cache_block
                }
            }
        } else {
            quote! {
                if let Some(result) = cache.get(&key).map_err(#map_error)? {
                    #return_cache_block
                }
            }
        };
        let logic = if asyncness.is_some() {
            quote! {
                let cache = #init_cache_ident.get_or_init(init).await;
                #async_cache_get_return
            }
        } else {
            quote! {
                let cache = #init_cache_ident;
                if let Some(result) = cache.get(&key).map_err(#map_error)? {
                    #return_cache_block
                }
            }
        };
        let set_cache_and_return = quote! {
            #set_cache_block
            result
        };
        let function_call = if asyncness.is_some() {
            quote! {
                let result = #call_prefix #no_cache_fn_ident(#(#without_self_names),*).await;
            }
        } else {
            quote! {
                let result = #call_prefix #no_cache_fn_ident(#(#without_self_names),*);
            }
        };

        let do_set_return_block = gen_set_return_block(
            asyncness,
            init_cache_ident,
            function_call,
            set_cache_and_return,
        );

        let expanded = quote! {
            #[doc = #cache_fn_ident_doc]
            #(#attributes)*
             #visibility #signature {
                 #init
                 #use_trait
                 let key = #key_convert_block;
                 {
                     // check if the result is kash
                     #logic
                 }
                 #do_set_return_block
             }
        };

        tokens.extend(expanded);
    }
}