function_call.fbs

include "function_types.fbs";

namespace Hyperlight.Generated;

enum FunctionCallType : ubyte {
    // none is invalid, its the default, its only here to ensure that the type is explicitly set to guest or host as none should fail validation if a buffer using it is written to memory
    none,
    guest,
    host,
}

// Flatbuffers rust generator doesn't support vectors of unions so we have to wrap them in a table
// see https://github.com/google/flatbuffers/issues/5024

table Parameter {
    value:ParameterValue(required);
}

table FunctionCall {
    function_name:string(required, key);
    parameters:[Parameter];
    function_call_type:FunctionCallType;
    // For dynamic calls such as WASM functions we need to know the expected return type
    // as these functions are not registered in the guest then there is no way of knowing what the return type is expected to be 
    // we could register all the WASM functions in the guest by examining the WASM module 
    // but even if we did this we would still not know the return type of the function as WASM metadata does not contain this information
    // so we have to rely on the host to tell us what the return type is
    // we can also use this to validate what the host expects where we have a statically registered function.
    // If we ultimately adopt WIT for IDL then we might not need this any longer
    expected_return_type:ReturnType;
}

root_type FunctionCall;