[wip]

Author: chfanghr

.gitignore

@@ -2,3 +2,4 @@ result
 .direnv
 .pre-commit-config.yaml
 .DS_Store
+target

flake.nix

@@ -23,6 +23,7 @@
         ./hercules-ci.nix
 
         ./plutus-ledger-api/build.nix
+        ./is-plutus-data-derive/build.nix
       ];
       debug = true;
       systems = [ "x86_64-linux" "x86_64-darwin" ];

is-plutus-data-derive/Cargo.lock

@@ -0,0 +1,13 @@
+[package]
+name = "plutus-data-derive"
+version = "0.1.0"
+edition = "2021"
+
+[dependencies]
+proc-macro2 = "1.0.87"
+quote = "1.0.37"
+syn = { version = "2.0.79", features = ["full"]}
+thiserror = "1.0.64"
+
+[lib]
+proc-macro = true

is-plutus-data-derive/Cargo.toml

@@ -0,0 +1,17 @@
+{ inputs, ... }: {
+  perSystem = { config, system, ... }:
+    let
+      rustFlake =
+        inputs.flake-lang.lib.${system}.rustFlake {
+          src = ./.;
+          version = "0";
+          crateName = "is-plutus-data-derive";
+          devShellHook = config.settings.shell.hook;
+          cargoNextestExtraArgs = "--all-features";
+        };
+
+    in
+    {
+      inherit (rustFlake) packages checks devShells;
+    };
+}

is-plutus-data-derive/build.nix

@@ -0,0 +1,274 @@
+use std::str::FromStr;
+
+use quote::ToTokens;
+use syn::{
+    ext::IdentExt,
+    parse::{Parse, ParseStream},
+    parse_macro_input, parse_quote,
+    punctuated::Punctuated,
+    spanned::Spanned,
+    token::Impl,
+    Attribute, Block, Data, DataEnum, DeriveInput, Error, Expr, Fields, FieldsNamed, FieldsUnnamed,
+    Ident, ImplGenerics, LitStr, Meta, Result, Stmt, TypeGenerics, WhereClause,
+};
+
+#[proc_macro_derive(IsPlutusData, attributes(plutus_data_derive_strategy))]
+pub fn derive_is_plutus_data(input: proc_macro::TokenStream) -> proc_macro::TokenStream {
+    let input = parse_macro_input!(input as DeriveInput);
+    get_is_plutus_data_instance(input)
+        .unwrap()
+        .into_token_stream()
+        .into()
+}
+
+fn get_is_plutus_data_instance(input: DeriveInput) -> Result<Impl> {
+    let type_name = &input.ident;
+
+    let strategy = get_derive_strategy(&input)?;
+
+    let (encoder, decoder) = match strategy {
+        DeriveStrategy::Newtype => get_newtype_encoder_decoder(&input),
+        DeriveStrategy::List => get_list_encoder_decoder(&input),
+        DeriveStrategy::Constr => get_constr_encoder_decoder(&input),
+    }?;
+
+    let mut generics = input.generics;
+
+    // TODO(chfanghr): Do we care about type role?
+    generics.type_params_mut().for_each(|param| {
+        param
+            .bounds
+            .push(parse_quote!(plutus_ledger_api::plutus_Data::IsPlutusData));
+    });
+
+    let (impl_generics, type_generics, where_clause) = generics.split_for_impl();
+
+    Ok(parse_quote!(
+        impl #impl_generics plutus_ledger_api::plutus_data::IsPlutusData for #type_name #type_generics #where_clause {
+            fn to_plutus_data(&self) -> plutus_ledger_api::plutus_data::PlutusData {
+                #encoder
+            }
+
+            fn from_plutus_data(plutus_data: &plutus_ledger_api::plutus_data::PlutusData) -> Result<Self, plutus_ledger_api::plutus_data::PlutusDataError>
+                where Self: Sized; {
+                #decoder
+            }
+        }
+    ))
+}
+
+#[derive(Debug)]
+enum DeriveStrategy {
+    Newtype,
+    List,
+    Constr,
+}
+
+#[derive(Debug, thiserror::Error)]
+enum DeriveStrategyError {
+    #[error("Unknown strategy {0}. Should be one of Newtype, List and Constr.")]
+    UnknownStrategy(String),
+    #[error("Unable to parse strategy. Should be an Ident.")]
+    UnexpectedToken,
+    #[error("More than one strategies specified.")]
+    MoreThanOneSpecified,
+}
+
+impl Default for DeriveStrategy {
+    fn default() -> Self {
+        Self::Constr
+    }
+}
+
+impl FromStr for DeriveStrategy {
+    type Err = DeriveStrategyError;
+
+    fn from_str(s: &str) -> std::result::Result<Self, Self::Err> {
+        match s {
+            "Newtype" => Ok(Self::Newtype),
+            "List" => Ok(Self::List),
+            "Constr" => Ok(Self::Constr),
+            _ => Err(DeriveStrategyError::UnknownStrategy(s.into())),
+        }
+    }
+}
+impl Parse for DeriveStrategy {
+    fn parse(input: ParseStream) -> Result<Self> {
+        let ident = input.call(Ident::parse)?;
+        Self::from_str(&ident.to_string()).map_err(|unknown_strategy| {
+            Error::new(
+                ident.span(),
+                format!("unknown strategy: {}", unknown_strategy),
+            )
+        })
+    }
+}
+
+fn try_parse_derive_strategy(attr: &Attribute) -> Option<Result<DeriveStrategy>> {
+    let value = match &attr.meta {
+        Meta::NameValue(name_value) => name_value
+            .path
+            .is_ident("plutus_data_derive_strategy")
+            .then_some(&name_value.value),
+        _ => None,
+    }?;
+
+    Some(match &value {
+        Expr::Path(path) => (|| -> Result<DeriveStrategy> {
+            let ident = path.path.require_ident()?;
+            DeriveStrategy::from_str(&ident.to_string())
+                .map_err(|err| Error::new(ident.span(), err))
+        })(),
+        _ => Err(Error::new(
+            value.span(),
+            DeriveStrategyError::UnexpectedToken,
+        )),
+    })
+}
+
+fn get_derive_strategy(input: &DeriveInput) -> Result<DeriveStrategy> {
+    let mut derive_strategy_results: Vec<_> = input
+        .attrs
+        .iter()
+        .map(try_parse_derive_strategy)
+        .flatten()
+        .collect();
+
+    match derive_strategy_results.len() {
+        0 => Ok(DeriveStrategy::default()),
+        1 => derive_strategy_results.remove(0),
+        _ => Err(Error::new(
+            input.span(),
+            DeriveStrategyError::MoreThanOneSpecified,
+        )),
+    }
+}
+
+#[derive(Debug, thiserror::Error)]
+enum NewtypeStrategyError {
+    #[error("Only struct types are supported by newtype strategy")]
+    UnexpectedDataVariant,
+    #[error("Newtype derivation expects exactly one filed")]
+    NotSingleField,
+}
+
+fn get_newtype_encoder_decoder(input: &DeriveInput) -> Result<(Block, Block)> {
+    let s = match &input.data {
+        Data::Struct(s) => Ok(s),
+        _ => Err(Error::new(
+            input.span(),
+            NewtypeStrategyError::UnexpectedDataVariant,
+        )),
+    }?;
+
+    if s.fields.len() != 1 {
+        Err(Error::new(
+            input.span(),
+            NewtypeStrategyError::NotSingleField,
+        ))?
+    }
+
+    let field = s.fields.iter().next().unwrap();
+
+    let encoder = parse_quote!({
+        self.#field.to_plutus_data()
+    });
+
+    let decoder = match &field.ident {
+        Some(field_name) => {
+            parse_quote!({
+                Ok(Self {
+                    #field_name: plutus_ledger_api::plutus_data::IsPlutusData::from_plutus_data(plutus_data)?
+                })
+            })
+        }
+        None => {
+            parse_quote!({
+                Ok(Self(
+                    plutus_ledger_api::plutus_data::IsPlutusData::from_plutus_data(plutus_data)?,
+                ))
+            })
+        }
+    };
+
+    Ok((encoder, decoder))
+}
+
+#[derive(Debug, thiserror::Error)]
+enum ListStrategyError {
+    #[error("Only struct types are supported by list strategy")]
+    UnexpectedDataVariant,
+}
+
+fn get_list_encoder_decoder(input: &DeriveInput) -> Result<(Block, Block)> {
+    match &input.data {
+        Data::Struct(s) => {
+            let fields = &s.fields;
+
+            let encode_field_stmts = fields
+                .iter()
+                .map(|f| -> Stmt { parse_quote!(self.#f.to_plutus_data()) });
+
+            let encoder: Block = parse_quote!({
+                plutus_ledger_api::plutus_data::PlutusData::List(vec![ #(#encode_field_stmts),*])
+            });
+
+            let decoder: Block = match &fields {
+                Fields::Named(named_fields) => get_list_decoder_for_named_struct(named_fields),
+                Fields::Unnamed(unnamed_fields) => {
+                    get_list_decoder_for_unnamed_struct(unnamed_fields)
+                }
+                Fields::Unit => parse_quote!({ Self }),
+            };
+
+            Ok((encoder, decoder))
+        }
+        _ => Err(Error::new(
+            input.span(),
+            ListStrategyError::UnexpectedDataVariant,
+        )),
+    }
+}
+
+fn get_list_decoder_for_named_struct(fields: &FieldsNamed) -> Block {
+    let len = fields.named.len();
+
+    let decode_field_stmts = fields.named.iter().enumerate().map(|(i, f)| -> Stmt {
+        parse_quote!(
+            #f: plutus_ledger_api::plutus_data::IsPlutusData::from_plutus_data(fields[#i])?
+        )
+    });
+
+    parse_quote!({
+        let fields = plutus_ledger_api::plutus_data::parse_list(plutus_data)?; // TODO(chfanghr): implement parse_list
+        let fields = plutus_ledger_api::plutus_data::parse_constr_with_tag::parse_fixed_len_plutus_data_list::<#len>(fields.as_slice())?;
+
+        Ok(Self {
+            #(#decode_field_stmts),*
+        })
+    })
+}
+
+fn get_list_decoder_for_unnamed_struct(fields: &FieldsUnnamed) -> Block {
+    let len = fields.unnamed.len();
+    let indexes = 0..len;
+
+    parse_quote!({
+        let fields = plutus_ledger_api::plutus_data::parse_list(plutus_data)?;
+        let fields = plutus_ledger_api::plutus_data::parse_constr_with_tag::parse_fixed_len_plutus_data_list::<#len>(fields.as_slice())?;
+
+        Ok(Self (
+            #(plutus_ledger_api::plutus_data::IsPlutusData::from_plutus_data(fields[#indexes])?),*
+        ))
+    })
+}
+
+#[derive(Debug, thiserror::Error)]
+enum ConstrStrategyError {
+    #[error("Union types are supported by constr strategy")]
+    UnexpectedDataVariant,
+}
+
+fn get_constr_encoder_decoder(input: &DeriveInput) -> Result<(Block, Block)> {
+    todo!()
+}