from modelverse_kernel.primitives import PrimitiveFinished

def reverseKeyLookup(a, b, **remainder):
    edges = yield [("RO", [a])]
    expanded_edges = yield [("RE", [i]) for i in edges]
    for i, edge in enumerate(expanded_edges):
        if b == edge[1]:
            # Found our edge: edges[i]
            outgoing = yield [("RO", [edges[i]])]
            result = yield [("RE", [outgoing[0]])]
            raise PrimitiveFinished(result[1])

    result = yield [("CNV", ["(unknown: %s)" % b])]
    raise PrimitiveFinished(result)

def read_attribute(a, b, c, **remainder):
    #TODO this can be optimized even further...
    model_dict, b_val, type_mapping = \
                    yield [("RD", [a, "model"]),
                           ("RV", [b]),
                           ("RD", [a, "type_mapping"]),
                           ]
    model_instance, edges = \
                    yield [("RD", [model_dict, b]),
                           ("RO", [a]),
                           ]
    edge_types =    yield [("RDN", [type_mapping, i]) for i in edges]
    type_edge_val = yield [("RE", [i]) for i in edge_types]

    src_nodes = set([i[0] for i in type_edge_val])

    found_edges =   yield [("RDE", [i, b_val]) for i in src_nodes]

    if len(src_nodes) == 1:
        found_edges = [found_edges]

    for e1 in found_edges:
        if e1 is not None:
            # Found an edge!
            for i, e2 in enumerate(edge_types):
                if e1 == e2:
                    # The instance of this edge is the one we want!
                    edge = edges[i]
                    edge_val = yield [("RE", [edge])]
                    result = edge_val[1]
                    raise PrimitiveFinished(result)
    else:
        result = yield [("RR", [])]
        raise PrimitiveFinished(result)

    raise Exception("Error in reading edge!")