Custom storage layout.

[zie1ony]

Casper Node doesn't offer the ability to query the getter entry point. It forced (as I predicted long time ago) developers to use internal storage structure to obtain data from the contract. It means it's not enough to know entry points of a contract, also storage structure should be specified.

One of a Casper DEXs, https://friendly.market, allows to add custom tokens. I added a token implemented in Odra, but even, that it has all the right entry points, it can't be used, because they require name, symbol and balances exactly like it is implemented in https://github.com/casper-ecosystem/cep18 using named keys.

Having that said I propose to allow for custom data layouts to be ecosystem-compatible. It could look like:

pub struct CustomStorageLayout;

#[odra::module(layout = CustomStorageLayout)]
pub struct CasperEcosystemCep18 {
   #[transparent]
   pub token: odra_modules::erc20::Erc20
}

More exploration is needed.

[zie1ony]

One possible idea:

enum StorageKind {
    NamedKey(String), // named key
    Disctionary(String, String) // named key, key
}

trait StorageLayout {
    fn key(&self, index: u32, name: &str) -> StorageKind;
}

struct Cep18CasperLabsStorage;

impl StorageLayout for Cep18CasperLabsStorage {
    fn key(&self, index: u32, name: &str) -> StorageKind {
        match index {
            0 => StorageKind::NamedKey("total_supply".to_string()),
            1 => StorageKind::Disctionary("balances".to_string(), name.to_string()),
            _ => panic!("Invalid index")
        }
    }
}