engine/transaction_derive/src/lib.rs

use proc_macro::TokenStream;

use quote::{format_ident, quote, ToTokens};
use syn::{parse_macro_input, Data, DeriveInput, Fields, Ident};

mod apply_transaction;
mod attribute_info;
mod attribute_token_type;
mod data_type;
mod get_transaction;
mod tracker_field;
mod transaction_field;

use apply_transaction::*;
use attribute_info::*;
use data_type::*;
use get_transaction::*;
use tracker_field::*;
use transaction_field::*;

/// # Attributes
///
/// * #[transaction(pre_setter_exec = `Function Name`)] ``` Fn(&mut self, t: T) -> T ```
/// * #[transaction(setter_exec = `Function Name`)] ``` Fn(&mut self, t: T) -> Result<()> ```
/// * #[transaction(apply_exec = `Function Name`)] ``` Fn(&self, old: T, i: usize, multi_mut: &mut MultiMut<'_>, scene: &mut Scene) -> Result<()> ```
/// * #[transaction(convert_as = `Data Type`)]
/// * #[transaction(skip_getter)]
/// * #[transaction(private_setter)]
/// * #[transaction(from = `Function Name`)] ``` Fn(t: T) -> U ```
/// * #[transaction(into = `Function Name`)] ``` Fn(&self, u: U) -> T ```
/// * #[transaction(feature = `Feature Name`)]
/// * #[transaction(not_feature = `Feature Name`)]
///
/// # Examples
///
/// ```
/// #[derive(Transaction)]
/// struct Test {
///     #[transaction]
///     test: u32,
///
///     #[tracker]
///     tracker: TestTransactionTracker,
/// }
/// ```
///
#[proc_macro_derive(Transaction, attributes(transaction, tracker))]
pub fn transaction_builder(item: TokenStream) -> TokenStream {
    let ast = parse_macro_input!(item as DeriveInput);

    let struct_name = ast.ident;
    let generics = ast.generics.to_token_stream();

    let mut tracker = None;
    let mut transactions = Vec::new();

    match ast.data {
        Data::Struct(data_struct) => match data_struct.fields {
            Fields::Named(named_fields) => {
                for field in named_fields.named.iter() {
                    let attribute_infos: Vec<AttributeInfo> = field
                        .attrs
                        .iter()
                        .filter_map(|attribute| AttributeInfo::from_attribute(attribute))
                        .collect();

                    if attribute_infos.is_empty() {
                        continue;
                    }

                    AttributeInfo::check_duplicate(&attribute_infos);

                    let transaction_field = TransactionField {
                        variable_name: field
                            .ident
                            .as_ref()
                            .expect("named field should have a name")
                            .clone(),
                        data_type: DataType::new(&field.ty),
                        attribute_infos,

                        tracker: None,
                    };

                    if AttributeInfo::is_transaction(&transaction_field.attribute_infos) {
                        transactions.push(transaction_field);
                    } else if AttributeInfo::is_tracker(&transaction_field.attribute_infos) {
                        assert!(tracker.is_none(), "Only one tracker allowed");

                        tracker = Some(transaction_field);
                    }
                }
            }
            Fields::Unnamed(_) => {
                todo!("Unnamed Field")
            }
            Fields::Unit => {
                todo!("Unit Field")
            }
        },
        Data::Enum(_) => {
            todo!("Data Type Enum")
        }
        Data::Union(_) => {
            todo!("Data Type Union")
        }
    }

    if transactions.is_empty() {
        build_empty(struct_name, generics)
    } else {
        build_default(
            struct_name.clone(),
            generics,
            tracker.expect(&format!(
                "a tracker of type {}TransactionTracker is required",
                struct_name
            )),
            transactions,
        )
    }
}

fn build_empty(struct_name: Ident, generics: proc_macro2::TokenStream) -> TokenStream {
    TokenStream::from(quote! {
        impl #generics Transaction for #struct_name #generics {
            fn get_transactions(&mut self) -> anyhow::Result<Option<String>> {
                Ok(None)
            }

            fn apply_transactions(
                &mut self,
                mut _transactions: &str,
                _time: std::time::Duration,
                _multi_mut: &mut MultiMut<'_>,
                _scene: &mut Scene,
            ) -> anyhow::Result<()> {
                Ok(())
            }
        }
    })
}

fn build_default(
    struct_name: Ident,
    generics: proc_macro2::TokenStream,
    tracker: TransactionField,
    mut transactions: Vec<TransactionField>,
) -> TokenStream {
    let helper_struct = format_ident!("{}TransactionTracker", struct_name);

    let tracker_variable_name = tracker.variable_name;
    let mut variable_name_list = String::new();

    for transaction in transactions.iter_mut() {
        transaction.tracker = Some(tracker_variable_name.clone());
        variable_name_list += (transaction.variable_name.to_string() + ",").as_str();
    }

    variable_name_list.pop();

    let tracker_fields: Vec<TrackerField> = transactions
        .iter()
        .map(|transaction| TrackerField::from(transaction))
        .collect();

    let data_types: Vec<TrackerDataType> = tracker_fields
        .iter()
        .map(|tracker| TrackerDataType::from(tracker))
        .collect();

    let default_type: Vec<TrackerDefault> = data_types
        .iter()
        .map(|tracker| TrackerDefault::from(tracker))
        .collect();

    let get_transactions: Vec<GetTransaction<'_>> = transactions
        .iter()
        .map(|t| GetTransaction::from(t))
        .collect();

    let apply_transactions: Vec<ApplyTransaction<'_>> = transactions
        .iter()
        .map(|t| ApplyTransaction::from(t))
        .collect();

    TokenStream::from(quote! {
        #[derive(Debug)]
        struct #helper_struct {
            #(
                #data_types
            )*
        }

        impl Clone for #helper_struct {
            fn clone(&self) -> Self {
                Self::default()
            }
        }

        impl Default for #helper_struct {
            fn default() -> Self {
                Self {
                    #(
                        #default_type
                    )*
                }
            }
        }

        impl #generics #struct_name #generics {
            #(
                #transactions
            )*
        }

        impl #generics Transaction for #struct_name #generics {
            fn get_transactions(&mut self) -> anyhow::Result<Option<String>> {
                let mut serialized_transactions = String::new();

                #(
                    #get_transactions
                )*

                // remove the last ';'
                serialized_transactions.pop();

                Ok(
                    if serialized_transactions.is_empty() {
                        None
                    } else {
                        Some(serialized_transactions)
                    }
                )
            }

            fn apply_transactions(
                &mut self,
                mut transactions: &str,
                time: std::time::Duration,
                multi_mut: &mut MultiMut<'_>,
                scene: &mut Scene,
            ) -> anyhow::Result<()> {
                let mut splits = transactions.split(';');

                for split in splits {
                    let pos = split.find(':').ok_or(
                        anyhow::Error::msg(format!(
                            "Failed parsing in ApplyTransaction ':' split. Found {}",
                            stringify!(#struct_name)
                        )))?;

                    let (var, value) = split.split_at(pos);
                    let value = value.trim_start_matches(':');

                    unsafe { multi_mut.clear_all_usages() };

                    match var {
                        #(
                            #apply_transactions
                        )*

                        _ => return Err(
                            anyhow::Error::msg(format!(
                                "Unsupported Transaction {} in {}",
                                var.to_string(),
                                stringify!(#struct_name)
                            ))
                        ),
                    }
                }

                Ok(())
            }
        }
    })
}