state_m_macro/

lib.rs

use macro_tools::{
    Assign, AttributeComponent, AttributePropertyComponent, AttributePropertyOptionalSyn, ct, qt,
    return_syn_err, syn_err,
};
use proc_macro::TokenStream;
use proc_macro2::TokenStream as TokenStream2;
use quote::{format_ident, quote};
use syn::{
    Attribute, DeriveInput, Expr, Ident, Index, LitInt, Type,
    parse::{Parse, ParseStream},
    parse_macro_input,
};

#[derive(Clone, Debug, Default)]
struct KvAssocArgs {
    pub assoc: AttributePropertyAssoc,
    pub label: AttributePropertyLabel,
}

impl AttributeComponent for KvAssocArgs {
    const KEYWORD: &'static str = "kv_assoc";

    fn from_meta(attr: &syn::Attribute) -> syn::Result<Self> {
        match attr.meta {
            syn::Meta::Path(ref _path) => Ok(Default::default()),
            syn::Meta::List(ref meta_list) => syn::parse2::<KvAssocArgs>(meta_list.tokens.clone()),
            syn::Meta::NameValue(_) => return_syn_err!(
                attr,
                "Expects an attribute of format `#[kv_assoc(assoc = AssocType, label = \"AssocLabel\")]`. \nGot: {}",
                qt! { #attr }
            ),
        }
    }
}

impl Parse for KvAssocArgs {
    fn parse(input: ParseStream) -> syn::Result<Self> {
        let mut result = Self::default();
        let error = |ident: &syn::Ident| -> syn::Error {
            let known = ct::str::format!(
                "Known entries of attribute {} are: {}, {}[optional].",
                KvAssocArgs::KEYWORD,
                AttributePropertyAssocMarker::KEYWORD,
                AttributePropertyLabelMarker::KEYWORD,
            );
            syn_err!(
                ident,
                r#"Expects an attribute of format '#[kv_assoc(assoc = AssocType, label = \"AssocLabel\")]'
                {known}
                But got:
                '{}'"#,
                qt! { #ident }
            )
        };
        while !input.is_empty() {
            let lookahead = input.lookahead1();
            if lookahead.peek(syn::Ident) {
                let ident: syn::Ident = input.parse()?;
                match ident.to_string().as_str() {
                    AttributePropertyAssoc::KEYWORD => {
                        result.assign(AttributePropertyAssoc::parse(input)?)
                    }
                    AttributePropertyLabel::KEYWORD => {
                        result.assign(AttributePropertyLabel::parse(input)?)
                    }
                    _ => return Err(error(&ident)),
                }
            } else {
                return Err(lookahead.error());
            }
            // optional trailing comma
            if input.peek(syn::Token![,]) {
                input.parse::<syn::Token![,]>()?;
            }
        }
        Ok(result)
    }
}

impl<IntoT> Assign<AttributePropertyAssoc, IntoT> for KvAssocArgs
where
    IntoT: Into<AttributePropertyAssoc>,
{
    #[inline(always)]
    fn assign(&mut self, component: IntoT) {
        self.assoc = component.into()
    }
}

impl<IntoT> Assign<AttributePropertyLabel, IntoT> for KvAssocArgs
where
    IntoT: Into<AttributePropertyLabel>,
{
    #[inline(always)]
    fn assign(&mut self, component: IntoT) {
        self.label = component.into()
    }
}

type AttributePropertyAssoc = AttributePropertyOptionalSyn<Type, AttributePropertyAssocMarker>;

#[derive(Clone, Copy, Debug, Default)]
struct AttributePropertyAssocMarker;

impl AttributePropertyComponent for AttributePropertyAssocMarker {
    const KEYWORD: &'static str = "assoc";
}

type AttributePropertyLabel = AttributePropertyOptionalSyn<Expr, AttributePropertyLabelMarker>;

#[derive(Clone, Copy, Debug, Default)]
struct AttributePropertyLabelMarker;

impl AttributePropertyComponent for AttributePropertyLabelMarker {
    const KEYWORD: &'static str = "label";
}

fn kv_assoc_args(attrs: &Vec<Attribute>) -> KvAssocArgs {
    let mut args = KvAssocArgs::default();
    for attr in attrs {
        if attr.path().is_ident(KvAssocArgs::KEYWORD) {
            args = KvAssocArgs::from_meta(attr).unwrap_or_else(|e| {
                panic!(
                    "Unable to parse attribute [{}] : {}",
                    KvAssocArgs::KEYWORD,
                    e
                )
            });
        }
    }
    args
}

fn attrs_except(attrs: &Vec<Attribute>, except: &str) -> Vec<Attribute> {
    attrs
        .iter()
        .filter(|v| !v.path().is_ident(except))
        .cloned()
        .collect()
}

fn q_attrs_except(attrs: &Vec<Attribute>, except: &str) -> TokenStream2 {
    let attrs_n: Vec<_> = attrs_except(attrs, except);
    let mut qs: Vec<_> = Vec::new();
    for attr in attrs_n {
        qs.push(quote! { #attr });
    }
    quote! {
        #(#qs)*
    }
}

#[proc_macro_attribute]
pub fn state_tag(_attr: TokenStream, item: TokenStream) -> TokenStream {
    let input = parse_macro_input!(item as DeriveInput);
    if !input.generics.params.is_empty() {
        panic!("Generics not supported.");
    }
    let i_attrs = &input.attrs;
    let i_ident = &input.ident;
    let i_vis = &input.vis;
    let impl_display = |ident: &Ident, args: KvAssocArgs, quotes: &mut Vec<TokenStream2>| match args
        .label
        .internal()
    {
        Some(expr) => {
            quotes.push(quote! {
                impl std::fmt::Display for #ident {
                    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
                        write!(f, "{}", #expr)
                    }
                }
            });
        }
        None => {
            quotes.push(quote! {
                impl std::fmt::Display for #ident {
                    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
                        write!(f, "{:?}", self)
                    }
                }
            });
        }
    };
    let mut quotes: Vec<_> = Vec::new();
    match input.data {
        syn::Data::Enum(data_enum) => {
            for item in &data_enum.variants {
                let q_attrs = q_attrs_except(&item.attrs, KvAssocArgs::KEYWORD);
                let v_ident = &item.ident;
                let v_fields = &item.fields;
                let t_name = format_ident!("{}{}", i_ident, v_ident);
                let q = match v_fields {
                    syn::Fields::Named(fields_named) => quote! {
                        #[derive(Clone, Debug)]
                        #q_attrs #i_vis struct #t_name #fields_named
                    },
                    syn::Fields::Unnamed(fields_unnamed) => quote! {
                        #[derive(Clone, Debug)]
                        #q_attrs #i_vis struct #t_name #fields_unnamed;
                    },
                    syn::Fields::Unit => quote! {
                        #[derive(Clone, Debug)]
                        #q_attrs #i_vis struct #t_name;
                    },
                };
                quotes.push(q);

                let q_fr = match v_fields {
                    syn::Fields::Named(fields_named) => {
                        let q_params: Vec<_> = itertools::intersperse(
                            fields_named.named.iter().map(|field| {
                                let ident = match field.ident {
                                    Some(ref ident) => ident.clone(),
                                    None => panic!("field should be named"),
                                };
                                quote! {#ident: value.#ident}
                            }),
                            quote! {,},
                        )
                        .collect();
                        quote! {
                            #i_ident::#v_ident{#(#q_params)*}
                        }
                    }
                    syn::Fields::Unnamed(fields_unnamed) => {
                        let len = fields_unnamed.unnamed.len();
                        let q_params: Vec<_> = itertools::intersperse(
                            (0..len).map(|i| {
                                let idx = Index::from(i);
                                quote! {value.#idx}
                            }),
                            quote! {,},
                        )
                        .collect();
                        quote! {
                            #i_ident::#v_ident(#(#q_params)*)
                        }
                    }
                    syn::Fields::Unit => quote! {
                        #i_ident::#v_ident
                    },
                };
                let q_f = quote! {
                    impl From<#t_name> for #i_ident {
                        fn from(value: #t_name) -> #i_ident {
                            #q_fr
                        }
                    }
                };
                quotes.push(q_f);

                let args = kv_assoc_args(&item.attrs);
                match args.clone().assoc.internal() {
                    Some(typ) => {
                        quotes.push(quote! {
                            impl state_m::KvAssoc for #t_name {
                                type Value = #typ;
                            }
                        });
                    }
                    None => {
                        panic!("Expects an attribute of format `#[kv_assoc(assoc = AssocType)]`.")
                    }
                }
                impl_display(&t_name, args, &mut quotes);
            }
            let q_attrs = q_attrs_except(i_attrs, KvAssocArgs::KEYWORD);
            let mut variants = data_enum.variants.clone();
            for item in variants.iter_mut() {
                item.attrs = attrs_except(&item.attrs, KvAssocArgs::KEYWORD);
            }
            quotes.push(quote! {
                #q_attrs #i_vis enum #i_ident {
                    #variants
                }
            });
        }
        syn::Data::Struct(data_struct) => {
            let q_attrs = q_attrs_except(i_attrs, KvAssocArgs::KEYWORD);
            let fields = data_struct.fields;
            let semi_colon = match data_struct.semi_token {
                Some(_) => quote! {;},
                None => quote! {},
            };
            let args = kv_assoc_args(&input.attrs);
            match args.clone().assoc.internal() {
                Some(typ) => {
                    quotes.push(quote! {
                        #q_attrs #i_vis struct #i_ident #fields #semi_colon
                        impl state_m::KvAssoc for #i_ident {
                            type Value = #typ;
                        }
                    });
                }
                None => {
                    panic!("Expects an attribute of format `#[kv_assoc(assoc = AssocType)]`.")
                }
            }
            impl_display(i_ident, args, &mut quotes);
        }
        _ => panic!("Not supported."),
    };
    quote! {
        #(#quotes)*
    }
    .into()
}

#[proc_macro]
pub fn sm_watch(input: TokenStream) -> TokenStream {
    let lit_n = parse_macro_input!(input as LitInt);
    let n = lit_n
        .base10_parse::<usize>()
        .expect("Input can only be a number");
    assert!(n > 0, "Input number should larger than zero.");
    let method_name = format_ident!("watch_{n}");
    let tag_typs: Vec<_> = itertools::intersperse(
        (0..n).map(|i| {
            let typ = format_ident!("T{}", i);
            quote! {#typ}
        }),
        quote! {,},
    )
    .collect();
    let tag_params: Vec<_> = itertools::intersperse(
        (0..n).map(|i| {
            let name = format_ident!("tag_{}", i);
            let typ = format_ident!("T{}", i);
            quote! {
                #name: #typ
            }
        }),
        quote! {,},
    )
    .collect();
    let tag_typ_cons: Vec<_> = (0..n)
        .map(|i| {
            let typ = format_ident!("T{}", i);
            quote! {
                #typ: 'static + Clone + Debug + Into<K> + KvAssoc + Send + Sync,
                #typ::Value: 'static + AsState + Send + Sync,
            }
        })
        .collect();
    let fn_params_typ: Vec<_> = (0..n)
        .map(|i| {
            let typ = format_ident!("T{}", i);
            quote! {
                StateChange<#typ>,
            }
        })
        .collect();
    let vec_tags: Vec<_> = itertools::intersperse(
        (0..n).map(|i| {
            let name = format_ident!("tag_{}", i);
            quote! {
                #name.clone().into()
            }
        }),
        quote! {,},
    )
    .collect();
    let decl_vars: Vec<_> = (0..n)
        .map(|i| {
            let tag_name = format_ident!("tag_{}", i);
            let handle_name = format_ident!("handle_{}", i);
            let rx_name = format_ident!("rx_{}", i);
            let token_name = format_ident!("token_{}", i);
            quote! {
                    let #handle_name = self.get_handle(#tag_name.clone())?;
                    let (mut #rx_name, #token_name) = #handle_name.fanout();
            }
        })
        .collect();
    let all_state_names: Vec<_> = itertools::intersperse(
        (0..n).map(|i| {
            let name = format_ident!("state_{}", i);
            quote! {
                #name
            }
        }),
        quote! {,},
    )
    .collect();
    let calc_all_states = |idx: usize| {
        itertools::intersperse(
            (0..n).map(|i| {
                if i != idx {
                    let handle_name = format_ident!("handle_{}", i);
                    quote! {
                        StateChange::UnChange(#handle_name.state())
                    }
                } else {
                    quote! {
                        StateChange::Change(s_cur, s_old)
                    }
                }
            }),
            quote! {,},
        )
        .collect::<Vec<_>>()
    };
    let sel_tokens: Vec<_> = (0..n)
        .map(|i| {
            let token_name = format_ident!("token_{}", i);
            quote! {
                _ = #token_name.cancelled() => break,
            }
        })
        .collect();
    let sel_recvs: Vec<_> = (0..n)
        .map(|i| {
            let all_states = calc_all_states(i);
            let tag_name = format_ident!("tag_{}", i);
            let rx_name = format_ident!("rx_{}", i);
            quote! {
                r = #rx_name.recv() => {
                    match r {
                        Ok((s_cur, s_old)) => {
                            let mut states = (#(#all_states)*);
                            let (#(#all_state_names)*) = states;
                            if let Err(e) = func(#(#all_state_names)*, #tag_name.clone().into()).await {
                                tracing::error!("watch error -- {e:?}");
                            }
                        }
                        Err(_) => break,
                    }
                }
            }
        })
        .collect();
    quote! {
        async fn #method_name<#(#tag_typs)*, F>(&self, #(#tag_params)*, func: F) -> Result<(), GetHandleError<K>>
        where
            #(#tag_typ_cons)*
            F: 'static
                + Fn(
                    #(#fn_params_typ)* K
                ) -> Pin<Box<dyn Future<Output = anyhow::Result<()>> + Send>>
                + Send,
        {
            let tags: Vec<K> = vec![#(#vec_tags)*];
            assert!(
                tags.iter().duplicates().collect::<Vec<_>>().is_empty(),
                "Should not use duplicate tags."
            );
            #(#decl_vars)*
            tokio::spawn(async move {
                tracing::info!("watch_{} | {tags:?} -- start", #n);
                loop {
                    tokio::select! {
                        biased;
                        #(#sel_tokens)*
                        #(#sel_recvs)*
                    }
                }
                tracing::info!("watch_{} | {tags:?} -- close", #n);
            });
            Ok(())
        }
    }
    .into()
}

#[proc_macro]
pub fn watch_decl(input: TokenStream) -> TokenStream {
    let lit_n = parse_macro_input!(input as LitInt);
    let n = lit_n
        .base10_parse::<usize>()
        .expect("Input can only be a number");
    assert!(n > 0, "Input number should larger than zero.");
    let method_name = format_ident!("watch_{n}");
    let tag_typs: Vec<_> = itertools::intersperse(
        (0..n).map(|i| {
            let typ = format_ident!("T{}", i);
            quote! {#typ}
        }),
        quote! {,},
    )
    .collect();
    let tag_params: Vec<_> = itertools::intersperse(
        (0..n).map(|i| {
            let name = format_ident!("tag_{}", i);
            let typ = format_ident!("T{}", i);
            quote! {
                #name: #typ
            }
        }),
        quote! {,},
    )
    .collect();
    let tag_typ_cons: Vec<_> = (0..n)
        .map(|i| {
            let typ = format_ident!("T{}", i);
            quote! {
                #typ: 'static + Clone + Debug + Into<Self::K> + KvAssoc + Send + Sync,
                #typ::Value: 'static + AsState + Send + Sync,
            }
        })
        .collect();
    let fn_params_typ: Vec<_> = (0..n)
        .map(|i| {
            let typ = format_ident!("T{}", i);
            quote! {
                StateChange<#typ>,
            }
        })
        .collect();
    quote! {
        /// Watch multiple state readers simultaneously, state events from these readers arrived in queue.
        async fn #method_name<#(#tag_typs)*, F>(&self, #(#tag_params)*, func: F) -> Result<(), GetHandleError<Self::K>>
        where
            #(#tag_typ_cons)*
            F: 'static
                + Fn(
                    #(#fn_params_typ)* Self::K
                ) -> Pin<Box<dyn Future<Output = anyhow::Result<()>> + Send>>
                + Send;
    }
    .into()
}

#[proc_macro]
pub fn watch_impl(input: TokenStream) -> TokenStream {
    let lit_n = parse_macro_input!(input as LitInt);
    let n = lit_n
        .base10_parse::<usize>()
        .expect("Input can only be a number");
    assert!(n > 0, "Input number should larger than zero.");
    let method_name = format_ident!("watch_{n}");
    let tag_typs: Vec<_> = itertools::intersperse(
        (0..n).map(|i| {
            let typ = format_ident!("T{}", i);
            quote! {#typ}
        }),
        quote! {,},
    )
    .collect();
    let tag_params: Vec<_> = itertools::intersperse(
        (0..n).map(|i| {
            let name = format_ident!("tag_{}", i);
            let typ = format_ident!("T{}", i);
            quote! {
                #name: #typ
            }
        }),
        quote! {,},
    )
    .collect();
    let tag_typ_cons: Vec<_> = (0..n)
        .map(|i| {
            let typ = format_ident!("T{}", i);
            quote! {
                #typ: 'static + Clone + Debug + Into<Self::K> + KvAssoc + Send + Sync,
                #typ::Value: 'static + AsState + Send + Sync,
            }
        })
        .collect();
    let fn_params_typ: Vec<_> = (0..n)
        .map(|i| {
            let typ = format_ident!("T{}", i);
            quote! {
                StateChange<#typ>,
            }
        })
        .collect();
    let tag_names: Vec<_> = itertools::intersperse(
        (0..n).map(|i| {
            let name = format_ident!("tag_{}", i);
            quote! {
                #name
            }
        }),
        quote! {,},
    )
    .collect();
    quote! {
        async fn #method_name<#(#tag_typs)*, F>(&self, #(#tag_params)*, func: F) -> Result<(), GetHandleError<Self::K>>
        where
            #(#tag_typ_cons)*
            F: 'static
                + Fn(
                    #(#fn_params_typ)* Self::K
                ) -> Pin<Box<dyn Future<Output = anyhow::Result<()>> + Send>>
                + Send {
                    self.state_machine().#method_name(#(#tag_names)*, func).await
                }
    }
    .into()
}

#[proc_macro]
pub fn sm_merge_reader(input: TokenStream) -> TokenStream {
    let lit_n = parse_macro_input!(input as LitInt);
    let n = lit_n
        .base10_parse::<usize>()
        .expect("Input can only be a number");
    assert!(n > 1, "Input number should larger than one.");
    let method_name = format_ident!("merge_reader_{n}");
    let tag_typs: Vec<_> = itertools::intersperse(
        (0..n).map(|i| {
            let typ = format_ident!("T{}", i);
            quote! {#typ}
        }),
        quote! {,},
    )
    .collect();
    let tag_params: Vec<_> = itertools::intersperse(
        (0..n).map(|i| {
            let name = format_ident!("tag_{}", i);
            let typ = format_ident!("T{}", i);
            quote! {
                #name: #typ
            }
        }),
        quote! {,},
    )
    .collect();
    let tag_typ_cons: Vec<_> = (0..n)
        .map(|i| {
            let typ = format_ident!("T{}", i);
            quote! {
                #typ: 'static + Clone + Debug + Into<K> + KvAssoc + Send + Sync,
                #typ::Value: 'static + AsState + Send + Sync,
            }
        })
        .collect();
    let fn_params_typ: Vec<_> = (0..n)
        .map(|i| {
            let typ = format_ident!("T{}", i);
            quote! {
                #typ::Value,
            }
        })
        .collect();
    let vec_tags: Vec<_> = itertools::intersperse(
        (0..n).map(|i| {
            let name = format_ident!("tag_{}", i);
            quote! {
                #name.clone().into()
            }
        }),
        quote! {,},
    )
    .collect();
    let decl_vars: Vec<_> = (0..n)
        .map(|i| {
            let tag_name = format_ident!("tag_{}", i);
            let handle_name = format_ident!("handle_{}", i);
            let rx_name = format_ident!("rx_{}", i);
            let token_name = format_ident!("token_{}", i);
            quote! {
                    let #handle_name = self.get_handle(#tag_name.clone())?;
                    let (mut #rx_name, #token_name) = #handle_name.fanout();
            }
        })
        .collect();
    let chan_decl = {
        let all_capacities: Vec<_> = itertools::intersperse(
            (0..n).map(|i| {
                let handle_name = format_ident!("handle_{}", i);
                quote! {
                    #handle_name.capacity()
                }
            }),
            quote! {,},
        )
        .collect();
        quote! {
            let capacity = itertools::max(vec![#(#all_capacities)*]).expect("Should not happen.");
            let (tx, _) = tokio::sync::broadcast::channel(capacity);
            let tx_c = tx.clone();
        }
    };
    let sel_tokens: Vec<_> = (0..n)
        .map(|i| {
            let token_name = format_ident!("token_{}", i);
            quote! {
                _ = #token_name.cancelled() => break,
            }
        })
        .collect();
    let calc_state_decls = |idx| {
        (0..n)
            .map(|i| {
                let handle_name = format_ident!("handle_{}", i);
                let state_name = format_ident!("state_{}", i);
                if i != idx {
                    quote! {
                        let #state_name = #handle_name.state();
                    }
                } else {
                    quote! {
                        let #state_name = s_cur;
                    }
                }
            })
            .collect::<Vec<_>>()
    };
    let all_state_names: Vec<_> = itertools::intersperse(
        (0..n).map(|i| {
            let state_name = format_ident!("state_{}", i);
            quote! {
                #state_name.value
            }
        }),
        quote! {,},
    )
    .collect();
    let sel_recvs: Vec<_> = (0..n)
        .map(|i| {
            let state_decls = calc_state_decls(i);
            let rx_name = format_ident!("rx_{}", i);
            quote! {
                r = #rx_name.recv() => {
                    match r {
                        Ok((s_cur, _)) => {
                            #(#state_decls)*
                            let value = func(#(#all_state_names)*);
                            let event = StateEvent {
                                state: State {
                                    value,
                                    timestamp: chrono::Utc::now(),
                                },
                                is_touch: false,
                                close_handle: None,
                            };
                            if tx_c.send(event).is_err() {
                                break;
                            }
                        }
                        Err(_) => break,
                    }
                }
            }
        })
        .collect();
    quote! {
        async fn #method_name<#(#tag_typs)*, S, F>(&self, #(#tag_params)*, func: F) -> Result<Reader<S>, GetHandleError<K>>
        where
            #(#tag_typ_cons)*
            S: 'static + AsState + Send,
            F: 'static + Fn(#(#fn_params_typ)*) -> S + Send,
        {
            let tags: Vec<K> = vec![#(#vec_tags)*];
            assert!(
                tags.iter().duplicates().collect::<Vec<_>>().is_empty(),
                "Should not use duplicate tags."
            );
            #(#decl_vars)*
            #chan_decl
            tokio::spawn(async move {
                tracing::info!("merge_reader_{} | {tags:?} -- start", #n);
                loop {
                    tokio::select! {
                        biased;
                        #(#sel_tokens)*
                        #(#sel_recvs)*
                    }
                }
                tracing::info!("merge_reader_{} | {tags:?} -- close", #n);
            });
            Ok(Reader::new(capacity, tx))
        }
    }.into()
}

#[proc_macro]
pub fn merge_reader_decl(input: TokenStream) -> TokenStream {
    let lit_n = parse_macro_input!(input as LitInt);
    let n = lit_n
        .base10_parse::<usize>()
        .expect("Input can only be a number");
    assert!(n > 1, "Input number should larger than zero.");
    let method_name = format_ident!("merge_reader_{n}");
    let tag_typs: Vec<_> = itertools::intersperse(
        (0..n).map(|i| {
            let typ = format_ident!("T{}", i);
            quote! {#typ}
        }),
        quote! {,},
    )
    .collect();
    let tag_params: Vec<_> = itertools::intersperse(
        (0..n).map(|i| {
            let name = format_ident!("tag_{}", i);
            let typ = format_ident!("T{}", i);
            quote! {
                #name: #typ
            }
        }),
        quote! {,},
    )
    .collect();
    let tag_typ_cons: Vec<_> = (0..n)
        .map(|i| {
            let typ = format_ident!("T{}", i);
            quote! {
                #typ: 'static + Clone + Debug + Into<Self::K> + KvAssoc + Send + Sync,
                #typ::Value: 'static + AsState + Send + Sync,
            }
        })
        .collect();
    let fn_params_typ: Vec<_> = (0..n)
        .map(|i| {
            let typ = format_ident!("T{}", i);
            quote! {
                #typ::Value,
            }
        })
        .collect();
    quote! {
        /// Merge multiple state readers into one.
        async fn #method_name<#(#tag_typs)*, S, F>(&self, #(#tag_params)*, func: F) -> Result<Reader<S>, GetHandleError<Self::K>>
        where
            #(#tag_typ_cons)*
            S: 'static + AsState + Send,
            F: 'static + Fn(#(#fn_params_typ)*) -> S + Send;
    }.into()
}

#[proc_macro]
pub fn merge_reader_impl(input: TokenStream) -> TokenStream {
    let lit_n = parse_macro_input!(input as LitInt);
    let n = lit_n
        .base10_parse::<usize>()
        .expect("Input can only be a number");
    assert!(n > 1, "Input number should larger than zero.");
    let method_name = format_ident!("merge_reader_{n}");
    let tag_typs: Vec<_> = itertools::intersperse(
        (0..n).map(|i| {
            let typ = format_ident!("T{}", i);
            quote! {#typ}
        }),
        quote! {,},
    )
    .collect();
    let tag_params: Vec<_> = itertools::intersperse(
        (0..n).map(|i| {
            let name = format_ident!("tag_{}", i);
            let typ = format_ident!("T{}", i);
            quote! {
                #name: #typ
            }
        }),
        quote! {,},
    )
    .collect();
    let tag_typ_cons: Vec<_> = (0..n)
        .map(|i| {
            let typ = format_ident!("T{}", i);
            quote! {
                #typ: 'static + Clone + Debug + Into<Self::K> + KvAssoc + Send + Sync,
                #typ::Value: 'static + AsState + Send + Sync,
            }
        })
        .collect();
    let fn_params_typ: Vec<_> = (0..n)
        .map(|i| {
            let typ = format_ident!("T{}", i);
            quote! {
                #typ::Value,
            }
        })
        .collect();
    let tag_names: Vec<_> = itertools::intersperse(
        (0..n).map(|i| {
            let name = format_ident!("tag_{}", i);
            quote! {
                #name
            }
        }),
        quote! {,},
    )
    .collect();
    quote! {
        async fn #method_name<#(#tag_typs)*, S, F>(&self, #(#tag_params)*, func: F) -> Result<Reader<S>, GetHandleError<Self::K>>
        where
            #(#tag_typ_cons)*
            S: 'static + AsState + Send,
            F: 'static + Fn(#(#fn_params_typ)*) -> S + Send {
                self.state_machine().#method_name(#(#tag_names)*, func).await
            }
    }.into()
}

#[proc_macro]
pub fn sm_split_reader(input: TokenStream) -> TokenStream {
    let lit_n = parse_macro_input!(input as LitInt);
    let n = lit_n
        .base10_parse::<usize>()
        .expect("Input can only be a number");
    assert!(n > 1, "Input number should larger than one.");
    let method_name = format_ident!("split_reader_{n}");
    let state_typs: Vec<_> = itertools::intersperse(
        (0..n).map(|i| {
            let typ = format_ident!("S{}", i);
            quote! {#typ}
        }),
        quote! {,},
    )
    .collect();
    let reader_typs: Vec<_> = itertools::intersperse(
        (0..n).map(|i| {
            let typ = format_ident!("S{}", i);
            quote! {Reader<#typ>}
        }),
        quote! {,},
    )
    .collect();
    let state_typ_cons: Vec<_> = (0..n)
        .map(|i| {
            let typ = format_ident!("S{}", i);
            quote! {
                #typ: 'static + AsState + Send,
            }
        })
        .collect();
    let decl_vars: Vec<_> = (0..n)
        .map(|i| {
            let tx_name = format_ident!("tx_{}", i);
            let tx_name_c = format_ident!("tx_{}_c", i);
            quote! {
                let (#tx_name, _) = tokio::sync::broadcast::channel(capacity);
                let #tx_name_c = #tx_name.clone();
            }
        })
        .collect();
    let value_names: Vec<_> = itertools::intersperse(
        (0..n).map(|i| {
            let value_name = format_ident!("v_{}", i);
            quote! { #value_name }
        }),
        quote! {,},
    )
    .collect();
    let send_states: Vec<_> = (0..n)
        .map(|i| {
            let value_name = format_ident!("v_{}", i);
            let event_name = format_ident!("e_{}", i);
            let tx_name_c = format_ident!("tx_{}_c", i);
            quote! {
                let #event_name = StateEvent {
                    state: State {
                        value: #value_name,
                        timestamp: s_cur.timestamp.clone(),
                    },
                    is_touch: false,
                    close_handle: None,
                };
                if #tx_name_c.send(#event_name).is_err() {
                    break;
                }
            }
        })
        .collect();
    let res_readers: Vec<_> = itertools::intersperse(
        (0..n).map(|i| {
            let tx_name = format_ident!("tx_{}", i);
            quote! {
                Reader::new(capacity, #tx_name)
            }
        }),
        quote! {,},
    )
    .collect();
    quote!{
        async fn #method_name<T, F, #(#state_typs)*>(&self, tag: T, func: F) -> Result<(#(#reader_typs)*), GetHandleError<K>>
        where
            T: 'static + Clone + Debug + Into<K> + KvAssoc + Send,
            T::Value: 'static + AsState + Send + Sync,
            F: 'static + Fn(T::Value) -> (#(#state_typs)*) + Send,
            #(#state_typ_cons)*
        {
            let handle = self.get_handle(tag.clone())?;
            let capacity = handle.capacity();
            let (mut rx, token) = handle.fanout();
            #(#decl_vars)*
            let res_typ_name = std::any::type_name::<(#(#reader_typs)*)>();
            tokio::spawn(async move {
                tracing::info!("split_reader_{} | {tag:?} | {res_typ_name} -- start", #n);
                loop {
                    tokio::select! {
                        biased;
                        _ = token.cancelled() => break,
                        r = rx.recv() => {
                            match r {
                                Ok((s_cur, _)) => {
                                    let (#(#value_names)*) = func(s_cur.value);
                                    #(#send_states)*
                                },
                                Err(_) => break,
                            }
                        }
                    }
                }
                tracing::info!("split_reader_{} | {tag:?} | {res_typ_name} -- start", #n);
            });
            Ok((#(#res_readers)*))
        }
    }.into()
}

#[proc_macro]
pub fn split_reader_decl(input: TokenStream) -> TokenStream {
    let lit_n = parse_macro_input!(input as LitInt);
    let n = lit_n
        .base10_parse::<usize>()
        .expect("Input can only be a number");
    assert!(n > 1, "Input number should larger than one.");
    let method_name = format_ident!("split_reader_{n}");
    let state_typs: Vec<_> = itertools::intersperse(
        (0..n).map(|i| {
            let typ = format_ident!("S{}", i);
            quote! {#typ}
        }),
        quote! {,},
    )
    .collect();
    let reader_typs: Vec<_> = itertools::intersperse(
        (0..n).map(|i| {
            let typ = format_ident!("S{}", i);
            quote! {Reader<#typ>}
        }),
        quote! {,},
    )
    .collect();
    let state_typ_cons: Vec<_> = (0..n)
        .map(|i| {
            let typ = format_ident!("S{}", i);
            quote! {
                #typ: 'static + AsState + Send,
            }
        })
        .collect();
    quote!{
        /// Split a state reader into multiple state readers.
        async fn #method_name<T, F, #(#state_typs)*>(&self, tag: T, func: F) -> Result<(#(#reader_typs)*), GetHandleError<Self::K>>
        where
            T: 'static + Clone + Debug + Into<Self::K> + KvAssoc + Send,
            T::Value: 'static + AsState + Send + Sync,
            F: 'static + Fn(T::Value) -> (#(#state_typs)*) + Send,
            #(#state_typ_cons)*;
    }.into()
}

#[proc_macro]
pub fn split_reader_impl(input: TokenStream) -> TokenStream {
    let lit_n = parse_macro_input!(input as LitInt);
    let n = lit_n
        .base10_parse::<usize>()
        .expect("Input can only be a number");
    assert!(n > 1, "Input number should larger than one.");
    let method_name = format_ident!("split_reader_{n}");
    let state_typs: Vec<_> = itertools::intersperse(
        (0..n).map(|i| {
            let typ = format_ident!("S{}", i);
            quote! {#typ}
        }),
        quote! {,},
    )
    .collect();
    let reader_typs: Vec<_> = itertools::intersperse(
        (0..n).map(|i| {
            let typ = format_ident!("S{}", i);
            quote! {Reader<#typ>}
        }),
        quote! {,},
    )
    .collect();
    let state_typ_cons: Vec<_> = (0..n)
        .map(|i| {
            let typ = format_ident!("S{}", i);
            quote! {
                #typ: 'static + AsState + Send,
            }
        })
        .collect();
    quote!{
        async fn #method_name<T, F, #(#state_typs)*>(&self, tag: T, func: F) -> Result<(#(#reader_typs)*), GetHandleError<Self::K>>
        where
            T: 'static + Clone + Debug + Into<Self::K> + KvAssoc + Send,
            T::Value: 'static + AsState + Send + Sync,
            F: 'static + Fn(T::Value) -> (#(#state_typs)*) + Send,
            #(#state_typ_cons)* {
                self.state_machine().#method_name(tag, func).await
            }
    }.into()
}