sad_machine 1.0.0

Sad Machine - a static State Machine macro
Documentation 
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use proc_macro2::{Ident, Span, TokenStream};
use quote::{quote, ToTokens};

use crate::{
    state::States,
    transition::{Transition, Transitions},
};

#[derive(Debug, PartialEq)]
#[allow(single_use_lifetimes)]
pub(crate) struct StateTransitions<'a> {
    pub enum_name: &'a Ident,
    pub states: &'a States,
    pub transitions: &'a Transitions,
}

#[allow(single_use_lifetimes)]
impl<'a> ToTokens for StateTransitions<'a> {
    fn to_tokens(&self, tokens: &mut TokenStream) {
        for s in self.states {
            let struct_name = Ident::new(&format!("{}State", s.name), Span::call_site());

            let transitions = self
                .transitions
                .0
                .iter()
                .filter(|t| t.from.name.to_string() == s.name.to_string())
                .cloned()
                .collect::<Vec<Transition>>();

            if transitions.is_empty() {
                continue;
            }

            let transitions = Transitions(transitions).to_fns(&self.enum_name);

            tokens.extend(quote! {
                impl #struct_name {
                    #transitions
                }
            })
        }
    }
}

#[cfg(test)]
mod tests {
    use crate::{event::Event, state::State};

    use super::*;
    use syn::parse_quote;

    #[test]
    fn state_transition_tokens() {
        let state_transitions = StateTransitions {
            enum_name: &parse_quote! { TurnStile },
            states: &States(vec![parse_quote!(Locked), parse_quote!(Unlocked)]),
            transitions: &Transitions(vec![
                Transition {
                    event: Event {
                        name: parse_quote! { Coin },
                    },
                    from: State {
                        name: parse_quote! { Locked },
                    },
                    to: State {
                        name: parse_quote! { Unlocked },
                    },
                },
                Transition {
                    event: Event {
                        name: parse_quote! { Push },
                    },
                    from: State {
                        name: parse_quote! { Unlocked },
                    },
                    to: State {
                        name: parse_quote! { Locked },
                    },
                },
            ]),
        };

        let left = quote! {
            impl LockedState {
                pub fn coin(&self) -> TurnStile {
                    TurnStile::Unlocked(UnlockedState::FromCoin)
                }
            }

            impl UnlockedState {
                pub fn push(&self) -> TurnStile {
                    TurnStile::Locked(LockedState::FromPush)
                }
            }
        };

        let mut right = TokenStream::new();
        state_transitions.to_tokens(&mut right);

        assert_eq!(format!("{}", left), format!("{}", right))
    }
}