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use std::collections::HashMap; use proc_macro::TokenStream; use syn::{ parse_macro_input, braced, token, Ident, Result, Token }; use syn::parse::{ Parse, ParseStream }; use syn::punctuated::Punctuated; use quote::{quote, format_ident}; use convert_case::{Case, Casing}; struct Machine { name: Ident, shared_data_type: Option<Ident>, #[allow(dead_code)] brace_token: token::Brace, states: Punctuated<StateDefinition, Token![,]> } struct StateDefinition { init: bool, name: Ident, associated_data_type: Option<Ident>, #[allow(dead_code)] brace_token: token::Brace, transitions: Punctuated<StateTransition, Token![,]> } struct StateTransition { event: Ident, #[allow(dead_code)] separator: Token![=>], next_state: Ident } impl Parse for Machine { fn parse(input: ParseStream) -> Result<Self> { let name: Ident = input.parse()?; let mut shared_data_type: Option<Ident> = None; let colon: Result<Token![:]> = input.parse(); if let Ok(_) = colon { shared_data_type = Some(input.parse()?); } let content; Ok(Machine { name, shared_data_type, brace_token: braced!(content in input), states: content.parse_terminated(StateDefinition::parse)?, }) } } impl Parse for StateDefinition { fn parse(input: ParseStream) -> Result<Self> { let mut init = false; let name: Ident; let x: Ident = input.parse()?; if x == "init" { init = true; name = input.parse()?; } else { name = x; } let mut associated_data_type: Option<Ident> = None; let colon: Result<Token![:]> = input.parse(); if let Ok(_) = colon { associated_data_type = Some(input.parse()?); } let content; Ok(StateDefinition { init, name, associated_data_type, brace_token: braced!(content in input), transitions: content.parse_terminated(StateTransition::parse)?, }) } } impl Parse for StateTransition { fn parse(input: ParseStream) -> Result<Self> { Ok(StateTransition { event: input.parse()?, separator: input.parse()?, next_state: input.parse()? }) } } #[proc_macro] pub fn statemachine(input: TokenStream) -> TokenStream { let m = parse_macro_input!(input as Machine); let mut state_data_types = HashMap::new(); for state in m.states.iter() { if let Some(dt) = &state.associated_data_type { state_data_types.insert(&state.name, dt); } } let state_names: Vec<&Ident> = m.states.iter().map(|x| &x.name).collect(); let parent_name = &m.name; let wrapped_type = format_ident!("{}{}", "Wrapped", parent_name); let shared_data_type = &m.shared_data_type; let state_structs = m.states.iter().map(|x| { let state_name = &x.name; let data_type = &x.associated_data_type; match data_type { Some(dt) => quote! { pub struct #state_name { data: #dt } impl #state_name { fn new(data: #dt) -> Self { Self { data } } pub fn data(&self) -> &#dt { &self.data } } }, None => quote! { pub struct #state_name {} impl #state_name { fn new() -> Self { Self {} } } } } }); let transitions_block = m.states.iter().fold(quote!(), |acc, x| { let state_name = &x.name; let exit_fn_name = format_ident!("{}_{}", "on_exit", state_name.to_string().to_case(Case::Snake)); let transitions = x.transitions.iter().map(|y| { let event = &y.event; let next_state_name = &y.next_state; let arg = state_data_types.get(next_state_name); let enter_fn_name = format_ident!("{}_{}", "on_enter", next_state_name.to_string().to_case(Case::Snake)); let exit_call = match state_data_types.get(state_name) { Some(_) => quote! { let old_data = self.state.data(); self.observer.#exit_fn_name(State::#next_state_name, *old_data)?; }, None => quote! { self.observer.#exit_fn_name(State::#next_state_name)?; } }; match arg { Some(a) => match shared_data_type { Some(_) => quote! { impl<T: Observer> #parent_name<#state_name, T> { pub fn #event(mut self, data: #a) -> Result<#parent_name<#next_state_name, T>, T::Error> { self.observer.on_transition(State::#state_name, State::#next_state_name, Some(data))?; #exit_call self.observer.#enter_fn_name(Some(State::#state_name), data)?; Ok(#parent_name::<#next_state_name, T>::new(#next_state_name::new(data), self.data, self.observer)) } } }, None => quote! { impl<T: Observer> #parent_name<#state_name, T> { pub fn #event(mut self, data: #a) -> Result<#parent_name<#next_state_name, T>, T::Error> { self.observer.on_transition(State::#state_name, State::#next_state_name, Some(data))?; #exit_call self.observer.#enter_fn_name(Some(State::#state_name), data)?; Ok(#parent_name::<#next_state_name, T>::new(#next_state_name::new(data), self.observer)) } } } }, None => match shared_data_type { Some(_) => quote! { impl<T: Observer> #parent_name<#state_name, T> { pub fn #event(mut self) -> Result<#parent_name<#next_state_name, T>, T::Error> { self.observer.on_transition(State::#state_name, State::#next_state_name, Option::<()>::None)?; #exit_call self.observer.#enter_fn_name(Some(State::#state_name))?; Ok(#parent_name::<#next_state_name, T>::new(#next_state_name::new(), self.data, self.observer)) } } }, None => quote! { impl<T: Observer> #parent_name<#state_name, T> { pub fn #event(mut self) -> Result<#parent_name<#next_state_name, T>, T::Error> { self.observer.on_transition(State::#state_name, State::#next_state_name, Option::<()>::None)?; #exit_call self.observer.#enter_fn_name(Some(State::#state_name))?; Ok(#parent_name::<#next_state_name, T>::new(#next_state_name::new(), self.observer)) } } } } } }); quote! { #acc #(#transitions)* } }); let parent_state_impls = m.states.iter().map(|x| { let state_name = &x.name; let enter_fn_name = format_ident!("{}_{}", "on_enter", state_name.to_string().to_case(Case::Snake)); match shared_data_type { Some(sdt) => { let constructor = quote! { impl<T: Observer> #parent_name<#state_name, T> { fn new(state: #state_name, data: #sdt, observer: T) -> Self { Self { state, data, observer } } pub fn data(&self) -> &#sdt { &self.data } } }; match x.init { false => constructor, true => match &x.associated_data_type { Some(dt) => quote! { #constructor impl<T: Observer> #parent_name<#state_name, T> { pub fn init(data: #sdt, state_data: #dt, mut observer: T) -> Result<Self, T::Error> { observer.on_init(State::#state_name, Some(data), Some(state_data))?; observer.#enter_fn_name(None, state_data)?; Ok(Self::new(#state_name::new(state_data), data, observer)) } } }, None => quote! { #constructor impl<T: Observer> #parent_name<#state_name, T> { pub fn init(data: #sdt, mut observer: T) -> Result<Self, T::Error> { observer.on_init(State::#state_name, Some(data), Option::<()>::None)?; observer.#enter_fn_name(None)?; Ok(Self::new(#state_name::new(), data, observer)) } } } } } }, None => { let constructor = quote! { impl<T: Observer> #parent_name<#state_name, T> { fn new(state: #state_name, observer: T) -> Self { Self { state, observer } } } }; match x.init { false => constructor, true => match &x.associated_data_type { Some(dt) => quote! { #constructor impl<T: Observer> #parent_name<#state_name, T> { pub fn init(state_data: #dt, mut observer: T) -> Result<Self, T::Error> { observer.on_init(State::#state_name, Option::<()>::None, Some(state_data))?; observer.#enter_fn_name(None, state_data)?; Ok(Self::new(#state_name::new(state_data), observer)) } } }, None => quote! { #constructor impl<T: Observer> #parent_name<#state_name, T> { pub fn init(mut observer: T) -> Result<Self, T::Error> { observer.on_init(State::#state_name, Option::<()>::None, Option::<()>::None)?; observer.#enter_fn_name(None)?; Ok(Self::new(#state_name::new(), observer)) } } } } } } } }); let parent_struct = match shared_data_type { Some(sdt) => quote! { pub struct #parent_name<T, U: Observer> { pub state: T, data: #sdt, observer: U } }, None => quote! { pub struct #parent_name<T, U: Observer> { pub state: T, observer: U } } }; let restore_fns = m.states.iter().map(|x| { let state_name = &x.name; let expected_state_dt = state_data_types.get(state_name); let fn_name = format_ident!("{}_{}", "restore", state_name.to_string().to_lowercase()); match shared_data_type { Some(shared_dt) => { match expected_state_dt { Some(state_dt) => quote! { fn #fn_name<T: Observer>(shared_d_enc: Option<Encoded>, state_d_enc: Option<Encoded>, observer: T) -> Result<#wrapped_type<T>, ()> { let shared_d_enc_some = shared_d_enc.ok_or(())?; let shared_d: #shared_dt = match shared_d_enc_some { Encoded::Json(data) => serde_json::from_str(&data).ok().ok_or(())?, _ => return Err(()) }; let state_d_enc_some = state_d_enc.ok_or(())?; let state_d: #state_dt = match state_d_enc_some { Encoded::Json(data) => serde_json::from_str(&data).ok().ok_or(())?, _ => return Err(()) }; Ok(#wrapped_type::#state_name(#parent_name::<#state_name, T>::new(#state_name::new(state_d), shared_d, observer))) } }, None => quote! { fn #fn_name<T: Observer>(shared_d_enc: Option<Encoded>, state_d_enc: Option<Encoded>, observer: T) -> Result<#wrapped_type<T>, ()> { let shared_d_enc_some = shared_d_enc.ok_or(())?; let shared_d: #shared_dt = match shared_d_enc_some { Encoded::Json(data) => serde_json::from_str(&data).ok().ok_or(())?, _ => return Err(()) }; if state_d_enc.is_some() { return Err(()) }; Ok(#wrapped_type::#state_name(#parent_name::<#state_name, T>::new(#state_name::new(), shared_d, observer))) } } } }, None => { match expected_state_dt { Some(state_dt) => quote! { fn #fn_name<T: Observer>(shared_d_enc: Option<Encoded>, state_d_enc: Option<Encoded>, observer: T) -> Result<#wrapped_type<T>, ()> { if shared_d_enc.is_some() { return Err(()) }; let state_d_enc_some = state_d_enc.ok_or(())?; let state_d: #state_dt = match state_d_enc_some { Encoded::Json(data) => serde_json::from_str(&data).ok().ok_or(())?, _ => return Err(()) }; Ok(#wrapped_type::#state_name(#parent_name::<#state_name, T>::new(#state_name::new(state_d), observer))) } }, None => quote! { fn #fn_name<T: Observer>(shared_d_enc: Option<Encoded>, state_d_enc: Option<Encoded>, observer: T) -> Result<#wrapped_type<T>, ()> { if shared_d_enc.is_some() { return Err(()) }; if state_d_enc.is_some() { return Err(()) }; Ok(#wrapped_type::#state_name(#parent_name::<#state_name, T>::new(#state_name::new(), observer))) } } } } } }); let restore_arms = m.states.iter().map(|x| { let state_name = &x.name; let fn_name = format_ident!("{}_{}", "restore", state_name.to_string().to_lowercase()); quote!(stringify!(#state_name) => #fn_name(data, state_data, observer)) }); let listeners = m.states.iter().map(|x| { let state_name = &x.name; let enter_fn_name = format_ident!("{}_{}", "on_enter", state_name.to_string().to_case(Case::Snake)); let exit_fn_name = format_ident!("{}_{}", "on_exit", state_name.to_string().to_case(Case::Snake)); let maybe_data_type = state_data_types.get(state_name); match maybe_data_type { Some(data_type) => quote! { fn #enter_fn_name(&self, from: Option<State>, data: #data_type) -> Result<(), Self::Error> { Ok(()) } fn #exit_fn_name(&self, to: State, data: #data_type) -> Result<(), Self::Error> { Ok(()) } }, None => quote! { fn #enter_fn_name(&self, from: Option<State>) -> Result<(), Self::Error> { Ok(()) } fn #exit_fn_name(&self, to: State) -> Result<(), Self::Error> { Ok(()) } } } }); let out = quote! { pub enum State { #(#state_names),* } impl State { pub fn to_string(&self) -> String { match self { #(State::#state_names => String::from(stringify!(#state_names))),* } } } pub trait Observer { type Error; fn on_init<T: Serialize, U: Serialize>(&mut self, to: State, data: Option<T>, state_data: Option<U>) -> Result<(), Self::Error> { Ok(()) } fn on_transition<T: Serialize>(&mut self, from: State, to: State, data: Option<T>) -> Result<(), Self::Error> { Ok(()) } #(#listeners)* } #parent_struct #(#state_structs)* #(#parent_state_impls)* #transitions_block pub enum #wrapped_type<T: Observer> { #(#state_names(#parent_name<#state_names, T>)),* } pub enum Encoded<'a> { Json(&'a str) } #(#restore_fns)* pub fn restore<T: Observer>(state_str: &str, data: Option<Encoded>, state_data: Option<Encoded>, observer: T) -> Result<#wrapped_type<T>, ()> { match state_str { #(#restore_arms,)* _ => Err(()) } } }; out.into() }