ewasm 0.1.0

use wasmi::{
    Error as InterpreterError, FuncInstance, FuncRef, ModuleImportResolver, Signature, ValueType,
};

pub const LOADPRESTATEROOT_FUNC_INDEX: usize = 0;
pub const BLOCKDATASIZE_FUNC_INDEX: usize = 1;
pub const BLOCKDATACOPY_FUNC_INDEX: usize = 2;
pub const SAVEPOSTSTATEROOT_FUNC_INDEX: usize = 3;
pub const PUSHNEWDEPOSIT_FUNC_INDEX: usize = 4;
pub const USETICKS_FUNC_INDEX: usize = 5;

pub struct RuntimeModuleImportResolver;

impl<'a> ModuleImportResolver for RuntimeModuleImportResolver {
    fn resolve_func(
        &self,
        field_name: &str,
        _signature: &Signature,
    ) -> Result<FuncRef, InterpreterError> {
        let func_ref = match field_name {
            "eth2_useTicks" => FuncInstance::alloc_host(
                Signature::new(&[ValueType::I32][..], None),
                USETICKS_FUNC_INDEX,
            ),
            "eth2_loadPreStateRoot" => FuncInstance::alloc_host(
                Signature::new(&[ValueType::I32][..], None),
                LOADPRESTATEROOT_FUNC_INDEX,
            ),
            "eth2_blockDataSize" => FuncInstance::alloc_host(
                Signature::new(&[][..], Some(ValueType::I32)),
                BLOCKDATASIZE_FUNC_INDEX,
            ),
            "eth2_blockDataCopy" => FuncInstance::alloc_host(
                Signature::new(&[ValueType::I32, ValueType::I32, ValueType::I32][..], None),
                BLOCKDATACOPY_FUNC_INDEX,
            ),
            "eth2_savePostStateRoot" => FuncInstance::alloc_host(
                Signature::new(&[ValueType::I32][..], None),
                SAVEPOSTSTATEROOT_FUNC_INDEX,
            ),
            "eth2_pushNewDeposit" => FuncInstance::alloc_host(
                Signature::new(&[ValueType::I32][..], None),
                PUSHNEWDEPOSIT_FUNC_INDEX,
            ),
            _ => {
                return Err(InterpreterError::Function(format!(
                    "host module doesn't export function with name {}",
                    field_name
                )))
            }
        };
        Ok(func_ref)
    }
}