Research: Meta type system

[xlc]

In order for XCQ to be generic, we need to have a meta type system to describe types. This is required to support chains with different type definitions for common operation. For example, the AssetId for a fungible extension could be a numeric ID (asset hub), or a xcm::Location (also asset hub), or an enum (Acala). Therefore we need to allow the chain to describe such type and then the client can decode the output correctly using the type information.

We could either build a simple one, or use scale-info

enum PrimitiveType {
  /// Unsigned Integer up to 128 bits
  Unsigned,
  /// Signed Integer up to 128 bigs
  Signed,
  U256,
  I256,
  Bool,
  /// Vec<u8>
  Bytes,
  /// [u8; 32]
  H256,
}

struct Field {
  iden: Vec<u8>,
  type: Type,
}

struct StructType {
  iden: Vec<u8>,
  fields: Vec<Field>,
}

enum VariantField {
  Unnamed(Vec<Type>),
  Named(Vec<Field>),
}

struct Variant {
  iden: Vec<u8>,
  fields: Vec<VariantField>
}

struct EnumType {
  iden: Vec<u8>,
  variants: Vec<Variant>
}

enum Type {
  Primitive(PrimitiveType),
  Struct(StructType),
  Enum(EnumType),
}