modelverse/wrappers/modelverse.py

import urllib
import json
import random
import sys
import time
import threading
import uuid

from sccd.runtime.statecharts_core import Event

COMPILER_PATH = "interface/HUTN"

MODE_UNCONNECTED = 0
MODE_UNAUTHORIZED = 1
MODE_MODELLING = 2
MODE_MODIFY = 3
MODE_DIALOG = 4
MODE_MANUAL = 5
MODE_SERVICE = 6

# Bind to the compiler (might have to update path manually!)
sys.path.append(COMPILER_PATH)
from hutn_compiler.compiler import main as do_compile

import socket2event

# Exceptions
class ModelverseException(Exception):
    pass

class UnknownError(ModelverseException):
    pass

class UnknownIdentifier(ModelverseException):
    pass

class CompilationError(ModelverseException):
    pass

class NoSuchAttribute(ModelverseException):
    pass

class UnknownModel(ModelverseException):
    pass

class ConnectionError(ModelverseException):
    pass

class ModelExists(ModelverseException):
    pass

class PermissionDenied(ModelverseException):
    pass

class InvalidMode(ModelverseException):
    pass

class InterfaceMismatch(ModelverseException):
    pass

class UnknownMetamodellingHierarchy(ModelverseException):
    pass

# Helper functions and configuration: do not use yourself!
taskname = None
mode = MODE_UNCONNECTED
prev_mode = None
current_model = None
registered_metamodels = {}
outputs = [None]
ctrl_input = None
ctrl_output = None

def _output_thread(outputs, taskname):
    req_out = ctrl_output.addOutputListener("request_out")
    my_id = str(uuid.uuid4())

    try:
        while 1:
            ctrl_output.addInput(Event("HTTP_input", "request_in", [urllib.urlencode({"op": "get_output", "taskname": taskname}), my_id]))

            event = req_out.fetch(-1)
            if event.parameters[1] == my_id:
                outputs.append(json.loads(event.parameters[0]))
    except:
        pass

def _exec_on_statechart(statechart):
    def _exec_sc(controller, inport, outport):
        op = controller.addOutputListener(outport)

        while 1:
            if len(outputs) > 1:
                # Is an output message of the Mv, so put it in the SC
                del outputs[0]
                output_event = outputs[0]

                if output_event == "Success" or output_event == "Failure":
                    # Is a stop event!
                    controller.addInput(Event("terminate", inport, []))
                    break
                else:
                    # Is just a normal event!
                    controller.addInput(Event("input", inport, [output_event]))

            input_event = op.fetch(0)
            if input_event is not None:
                # Expand the event and make it HTTP input
                _input(input_event.parameters)
                
            time.sleep(0.02)
        
    thrd = threading.Thread(target=_exec_sc, args=statechart)
    thrd.daemon = True
    thrd.start()

    return None

def _get_metamodel(model):
    global registered_metamodels
    try:
        return registered_metamodels[model]
    except KeyError:
        raise UnknownMetamodellingHierarchy(model)

def _check_type(value):
    if not isinstance(value, (int, long, float, str, unicode, bool)):
        raise UnsupportedValue("%s : %s" % (value, str(type(value))))

def _check_type_list(value):
    if isinstance(value, list):
        [_check_type(i) for i in value]
    else:
        _check_type(value)

def _dict_to_list(python_dict):
    lst = []
    for k, v in python_dict.items():
        lst += [k, v]
    return lst

def _goto_mode(new_mode, model_name=None):
    global mode

    if mode == MODE_MANUAL and new_mode == MODE_MODIFY:
        if model_name != None and current_model != model_name:
            raise InvalidMode("Mode error: cannot modify other models!")
        else:
            return
    elif mode == MODE_MODELLING and new_mode == MODE_MODIFY:
        # Are in root view, but want to modify a model
        _model_modify(model_name, _get_metamodel(model_name))
    elif mode == MODE_MODIFY and new_mode == MODE_MODIFY and model_name != None and current_model != model_name:
        # Are in modify mode, but want to modify a different model
        mm = _get_metamodel(model_name)
        _model_exit()
        _model_modify(model_name, mm)
    elif mode == MODE_MODIFY and new_mode == MODE_MODELLING:
        _model_exit()
    elif mode == new_mode:
        return
    else:
        # Go to a mode that we have no automatic transfer to: raise exception
        raise InvalidMode("Required mode: %s, current mode: %s" % (new_mode, mode))

def _input(value, port=None):
    # Ugly json encoding of primitives
    #print("[IN] %s" % value)
    if port is None:
        port = taskname
    if isinstance(value, type([])):
        value = json.dumps(value)
        ctrl_input.addInput(Event("HTTP_input", "request_in", [urllib.urlencode({"op": "set_input", "taskname": port, "data": value}), None]))
    else:
        value = json.dumps(value)
        ctrl_input.addInput(Event("HTTP_input", "request_in", [urllib.urlencode({"op": "set_input", "taskname": port, "value": value}), None]))

def _input_raw(value, taskname):
    # Ugly json encoding of primitives
    ctrl_input.addInput(Event("HTTP_input", "request_in", [urllib.urlencode({"op": "set_input", "taskname": taskname, "value": value}), None]))

def _compile_AL(code):
    # Compile an action language file and send the compiled code
    code_fragments = code.split("\n")
    code_fragments = [i for i in code_fragments if i.strip() != ""]
    code_fragments = [i.replace("    ", "\t") for i in code_fragments]
    initial_tabs = min([len(i) - len(i.lstrip("\t")) for i in code_fragments])
    code_fragments = [i[initial_tabs:] for i in code_fragments]
    code_fragments.append("")
    code = "\n".join(code_fragments)

    with open(".code.alc", "w") as f:
        f.write(code)
        f.flush()

    compiled = do_compile(".code.alc", COMPILER_PATH + "/grammars/actionlanguage.g", "CS")
    return compiled

def _compile_model(code):
    # Compile a model and send the compiled graph
    # First change multiple spaces to a tab
    code_fragments = code.split("\n")
    code_fragments = [i for i in code_fragments if i.strip() != ""]
    code_fragments = [i.replace("    ", "\t") for i in code_fragments]
    initial_tabs = min([len(i) - len(i.lstrip("\t")) for i in code_fragments])
    code_fragments = [i[initial_tabs:] for i in code_fragments]
    code_fragments.append("")
    code = "\n".join(code_fragments)

    with open(".model.mvc", "w") as f:
        f.write(code)
        f.flush()

    return do_compile(".model.mvc", COMPILER_PATH + "/grammars/modelling.g", "M")

def _output(expected=None):
    try:
        while len(outputs) < 2:
            time.sleep(0.02)

        del outputs[0]
        #print("[OUT] %s" % outputs[0])
    except:
        raise UnknownError()

    if expected is not None and _last_output() != expected:
        raise InterfaceMismatch(_last_output(), expected)
    return _last_output()

def _last_output():
    return outputs[0]

# Raise common exceptions
def _handle_output(requested=None, split=False):
    value = _output()
    if value.startswith("Model exists: "):
        raise ModelExists(value.split(": ", 1)[1])
    elif value.startswith("Permission denied"):
        raise PermissionDenied(value.split(": ", 1)[1])
    elif value.startswith("Model not found: "):
        raise UnknownModel(value.split(": ", 1)[1])
    elif value.startswith("Element not found: "):
        raise UnknownIdentifier(value.split(": ", 1)[1])
    elif value.startswith("Element exists: "):
        raise ElementExists(value.split(": ", 1)[1])
    elif value.startswith("Attribute not found: "):
        raise NoSuchAttribute(value.split(": ", 1)[1])
    elif requested is not None and value.startswith(requested):
        if not split:
            return value
        else:
            splitted = value.strip().split(" ", 1)
            if len(splitted) > 1:
                return splitted[1].split("\n")
            else:
                return []
    else:
        raise InterfaceMismatch(value)
    
def _model_modify(model_name, metamodel_name):
    """Modify an existing model."""
    global mode
    global prev_mode

    if mode == MODE_MANUAL:
        prev_mode = MODE_MANUAL
        mode = MODE_MODIFY
        return None

    _goto_mode(MODE_MODELLING)
    prev_mode = MODE_MODELLING

    _input(["model_modify", model_name, metamodel_name])
    _handle_output("Success")
    global current_model
    current_model = model_name
    # Mode has changed
    mode = MODE_MODIFY
    _output("Model loaded, ready for commands!")

def _model_exit():
    """Leave model modify mode."""
    global mode
    global prev_mode

    if prev_mode == MODE_MANUAL:
        mode = MODE_MANUAL
        return

    if mode != MODE_MODIFY:
        raise InvalidMode()

    _input("exit")
    _output("Success")
    mode = MODE_MODELLING

def alter_context(model_name, metamodel_name):
    global registered_metamodels
    registered_metamodels[model_name] = metamodel_name

# Main MvC operations
def init(address_param="127.0.0.1:8001", timeout=20.0):
    """Starts up the connection to the Modelverse."""
    # Start up the HTTP Client SC
    import http_client
    global ctrl_input
    global ctrl_output

    if ctrl_input is not None:
        ctrl_input.stop()
    if ctrl_output is not None:
        ctrl_output.stop()

    ctrl_input = http_client.Controller()
    ctrl_output = http_client.Controller()
    controllers = [ctrl_input, ctrl_output]

    addr, port = address_param.split(":", 1)
    port = int(port)

    for ctrl in controllers:
        listener = ctrl.addOutputListener("request_out")
        socket2event.boot_translation_service(ctrl)
        thrd = threading.Thread(target=ctrl.start)
        thrd.daemon = True
        thrd.start()

        evt = listener.fetch(-1)
        if evt.name != "http_client_initialized":
            raise Exception("HTTP client did not behave as expected during init: " + str(evt.name))

        ctrl.addInput(Event("connect", "request_in", [(addr, port), timeout]))

        evt = listener.fetch(-1)

        if evt.name == "http_client_timeout":
            raise Exception("HTTP client timeout")
        if evt.name != "http_client_ready":
            raise Exception("HTTP client did not behave as expected during connect: " + str(evt.name))

    global mode
    start_time = time.time()
    task = random.random()

    _input_raw('"%s"' % task, "task_manager")

    mode = MODE_UNAUTHORIZED

    global outputs
    global taskname

    outputs = [None]
    taskname = task

    # This re-assign also diconnects the previous get_output connections to the outputs variable
    thrd = threading.Thread(target=_output_thread, args=[outputs, task])
    thrd.daemon = True
    thrd.start()

def login(username, password):
    """Log in a user, if user doesn't exist, it is created."""
    global mode
    _goto_mode(MODE_UNAUTHORIZED)

    _output("Log on as which user?")
    _input(username)
    if _output() == "Password for existing user?":
        _input(password)
        if _output() == "Welcome to the Model Management Interface v2.0!":
            _output("Use the 'help' command for a list of possible commands")
            _input("quiet")
            mode = MODE_MODELLING
        elif _last_output() == "Wrong password!":
            raise PermissionDenied()
        else:
            raise InterfaceMismatch(_last_output())
    elif _last_output() == "This is a new user: please give password!":
        _input(password)
        _output("Please repeat the password")
        _input(password)
        if _output() == "Passwords match!":
            _output("Welcome to the Model Management Interface v2.0!")
            _output("Use the 'help' command for a list of possible commands")
            _input("quiet")
            mode = MODE_MODELLING
        elif _last_output() == "Not the same password!":
            # We just sent the same password, so it should be identical, unless the interface changed
            raise InterfaceMismatch(_last_output())
        else:
            raise InterfaceMismatch(_last_output())
    else:
        raise InterfaceMismatch(_last_output())

def model_add(model_name, metamodel_name, model_code=None):
    """Instantiate a new model."""
    _goto_mode(MODE_MODELLING)

    # Do this before creating the model, as otherwise compilation errors would make us inconsistent
    if model_code is not None:
        try:
            compiled = _compile_model(model_code)
        except Exception as e:
            raise CompilationError(e)
    else:
        compiled = [0]

    _input(["model_add", metamodel_name, model_name])
    _handle_output("Waiting for model constructors...")
    _input(compiled)
    _output("Success")

    global registered_metamodels
    registered_metamodels[model_name] = metamodel_name

def upload_code(code):
    try:
        compiled = _compile_AL(code)
    except Exception as e:
        raise CompilationError(e)

    _input(compiled)

def model_delete(model_name):
    """Delete an existing model."""
    _goto_mode(MODE_MODELLING)

    _input(["model_delete", model_name])
    _handle_output("Success")

def model_list(location):
    """List all models."""
    _goto_mode(MODE_MODELLING)
    _input(["model_list", location])
    return set(_handle_output("Success: ", split=True))

def model_list_full(location):
    """List full information on all models."""
    _goto_mode(MODE_MODELLING)
    _input(["model_list_full", location])
    output = _handle_output("Success: ", split=True)

    lst = set([])
    for v in output:
        m = v.strip()
        perm, own, grp, m = m.split(" ", 3)
        lst.add((m, own, grp, perm))

    return lst

def verify(model_name, metamodel_name=None):
    """Verify if a model conforms to its metamodel."""
    _goto_mode(MODE_MODELLING)

    if metamodel_name is None:
        metamodel_name = _get_metamodel(model_name)

    _input(["verify", model_name, metamodel_name])
    return _handle_output("Success: ", split=True)[0]

def model_overwrite(model_name, new_model=None, metamodel_name=None):
    """Upload a new model and overwrite an existing model."""
    _goto_mode(MODE_MODIFY, model_name)

    if new_model is not None:
        try:
            compiled = _compile_model(new_model)
        except Exception as e:
            raise CompilationError(e)
    else:
        compiled = [0]

    _input("upload")
    _handle_output("Waiting for model constructors...")
    _input(compiled)
    _output("Success")

    if metamodel_name is not None:
        global registered_metamodels
        registered_metamodels[model_name] = metamodel_name

def user_logout():
    """Log out the current user and break the connection."""
    global mode
    _goto_mode(MODE_MODELLING)
    _input("exit")
    mode = MODE_UNCONNECTED

def user_delete():
    """Removes the current user and break the connection."""
    global mode
    _goto_mode(MODE_MODELLING)
    _input("self-destruct")
    mode = MODE_UNCONNECTED

def model_render(model_name, mapper_name):
    """Fetch a rendered verion of a model."""
    _goto_mode(MODE_MODELLING)

    _input(["model_render", model_name, mapper_name])
    return json.loads(_handle_output("Success: ", split=True)[0])

def transformation_between(source, target):
    _goto_mode(MODE_MODELLING)

    _input(["transformation_between", source, target])
    output = _handle_output("Success: ", split=True)
    return set(output)

def transformation_add_MT(source_metamodels, target_metamodels, operation_name, code, callback=lambda: None):
    """Create a new model transformation."""
    global mode
    _goto_mode(MODE_MODELLING)
    import time

    start = time.time()
    try:
        compiled = _compile_model(code)
    except Exception as e:
        raise CompilationError(e)
    #print("Compilation took: %ss" % (time.time() - start))
    start = time.time()

    mv_dict_rep = _dict_to_list(source_metamodels) + [""] + _dict_to_list(target_metamodels) + [""]
    _input(["transformation_add_MT"] + mv_dict_rep + [operation_name])

    # Possibly modify the merged metamodel first (add tracability links)
    if len(source_metamodels) + len(target_metamodels) > 0:
        mode = MODE_MANUAL
        _output("Model loaded, ready for commands!")
        callback()
        _input("exit")
        mode = MODE_MODELLING
    #print("Callbacks took: %ss" % (time.time() - start))
    start = time.time()

    # Done, so RAMify and upload the model
    _handle_output("Waiting for model constructors...")
    _input(compiled)
    _handle_output("Success")
    #print("Upload and RAMify took: %ss" % (time.time() - start))

def transformation_add_AL(source_metamodels, target_metamodels, operation_name, code, callback=lambda: None):
    """Create a new action language model, which can be executed."""
    global mode
    _goto_mode(MODE_MODELLING)

    try:
        compiled = _compile_AL(code)
    except Exception as e:
        raise CompilationError(e)

    mv_dict_rep = _dict_to_list(source_metamodels) + [""] + _dict_to_list(target_metamodels) + [""]
    _input(["transformation_add_AL"] + mv_dict_rep + [operation_name])

    # Possibly modify the merged metamodel first (add tracability links)
    if len(source_metamodels) + len(target_metamodels) > 0:
        mode = MODE_MANUAL
        _output("Model loaded, ready for commands!")
        callback()
        _input("exit")
        mode = MODE_MODELLING

    _handle_output("Waiting for code constructors...")
    _input(compiled)
    _output("Success")

def transformation_add_MANUAL(source_metamodels, target_metamodels, operation_name, callback=lambda: None):
    """Create a new manual model operation."""
    global mode
    _goto_mode(MODE_MODELLING)

    mv_dict_rep = _dict_to_list(source_metamodels) + [""] + _dict_to_list(target_metamodels) + [""]
    _input(["transformation_add_MANUAL"] + mv_dict_rep + [operation_name])

    # Possibly modify the merged metamodel first (add tracability links)
    if len(source_metamodels) + len(target_metamodels) > 0:
        mode = MODE_MANUAL
        _output("Model loaded, ready for commands!")
        callback()
        _input("exit")
        mode = MODE_MODELLING

    _handle_output("Success")

def transformation_execute_AL(operation_name, input_models_dict, output_models_dict, statechart=None):
    """Execute an existing model operation."""
    global mode
    _goto_mode(MODE_MODELLING)

    mv_dict_rep = _dict_to_list(input_models_dict) + [""] + _dict_to_list(output_models_dict) + [""]

    _input(["transformation_execute", operation_name] + mv_dict_rep)
    _handle_output("Success: ready for AL execution")

    if statechart is not None:
        # We are to delegate this information to another statechart, which wants interaction
        # As such, we continue on a different thread, where we pipe the information, and let this call return immediately
        mode = MODE_DIALOG
        _exec_on_statechart(statechart)
        mode = MODE_MODELLING
        return None
    else:
        # No statechart associated, so just wait until we are finished
        while _output() not in ["Success", "Failure"]:
            pass
        if _last_output() == "Success":
            return True
        else:
            return False

def transformation_execute_MANUAL(operation_name, input_models_dict, output_models_dict, callback=lambda i: None):
    """Execute an existing model operation."""
    global mode
    _goto_mode(MODE_MODELLING)

    mv_dict_rep = _dict_to_list(input_models_dict) + [""] + _dict_to_list(output_models_dict) + [""]

    _input(["transformation_execute", operation_name] + mv_dict_rep)
    _handle_output("Success: ready for MANUAL execution")

    # Skip over the begin of mini_modify
    _handle_output("Please perform manual operation ")
    _output("Model loaded, ready for commands!")

    # We are now executing, so everything we get is part of the dialog, except if it is the string for transformation termination
    mode = MODE_MANUAL
    callback()
    # Finished, so leave
    _input("exit")
    mode = MODE_MODELLING

    # Got termination message, so we are done!
    if _output() == "Success":
        return True
    else:
        return False

def transformation_execute_MT(operation_name, input_models_dict, output_models_dict, statechart=None):
    """Execute an existing model operation."""
    global mode
    _goto_mode(MODE_MODELLING)

    mv_dict_rep = _dict_to_list(input_models_dict) + [""] + _dict_to_list(output_models_dict) + [""]

    _input(["transformation_execute", operation_name] + mv_dict_rep)
    _handle_output("Success: ready for MT execution")

    if statechart is not None:
        # We are to delegate this information to another statechart, which wants interaction
        # As such, we continue on a different thread, where we pipe the information, and let this call return immediately
        mode = MODE_DIALOG
        _exec_on_statechart(statechart)
        mode = MODE_MODELLING
        return None
    else:
        # No statechart associated, so just wait until we are finished
        while _output() not in ["Success", "Failure"]:
            pass
        if _last_output() == "Success":
            return True
        else:
            return False

def transformation_list():
    """List existing model operations."""
    _goto_mode(MODE_MODELLING)

    _input("transformation_list")
    output = _handle_output("Success: ", split=True)

    lst = set([])
    for v in output:
        t, m = v.strip().split(" ", 1)
        t = t[1:-1].strip()
        m = m.strip().split(":")[0].strip()
        lst.add((t, m))

    return lst

def process_execute(process_name, prefix, callbacks):
    """Execute a process model."""
    global mode
    _goto_mode(MODE_MODELLING)

    _input(["process_execute", process_name, prefix])
    _handle_output("Success")

    reuse = False
    while reuse or _output() != "Success":
        reuse = False
        output = _last_output()
        if output.startswith("Enacting "):
            # Next activity!
            t = output.split(" ", 1)[1].split(":", 1)[0]
            name = output.split(": ", 1)[1]
            if name in callbacks:
                callback = callbacks[name]
                if t == "ModelTransformation" or t == "ActionLanguage":
                    while not (_output().startswith("Enacting ") or _last_output() == "Success"):
                        mode = MODE_DIALOG
                        reply = callback(_last_output())
                        mode = MODE_MODELLING
                        if reply is not None:
                            _input(reply)
                    if _last_output().startswith("Enacting "):
                        reuse = True
                elif t == "ManualOperation":
                    _handle_output("Please perform manual operation ")
                    _output("Model loaded, ready for commands!")
                    mode = MODE_MANUAL
                    callback()
                    _input("exit")
                    mode = MODE_MODELLING

def permission_modify(model_name, permissions):
    """Modify permissions of a model."""
    _goto_mode(MODE_MODELLING)
    _input(["permission_modify", model_name, permissions])
    _handle_output("Success")

def permission_owner(model_name, owner):
    """Modify the owning user of a model."""
    _goto_mode(MODE_MODELLING)
    _input(["permission_owner", model_name, owner])
    _handle_output("Success")

def permission_group(model_name, group):
    """Modify the owning group of a model."""
    _goto_mode(MODE_MODELLING)
    _input(["permission_group", model_name, group])
    _handle_output("Success")

def group_create(group_name):
    """Create a new group."""
    _goto_mode(MODE_MODELLING)
    _input(["group_create", group_name])
    _handle_output("Success")

def group_delete(group_name):
    """Delete a group of which you are an owner."""
    _goto_mode(MODE_MODELLING)
    _input(["group_delete", group_name])
    _handle_output("Success")

def group_owner_add(group_name, user_name):
    """Add a new owning user to a group you own."""
    _goto_mode(MODE_MODELLING)
    _input(["owner_add", group_name, user_name])
    _handle_output("Success")

def group_owner_delete(group_name, user_name):
    """Delete an owning user to a group you own."""
    _goto_mode(MODE_MODELLING)
    _input(["owner_delete", group_name, user_name])
    _handle_output("Success")

def group_join(group_name, user_name):
    """Add a new user to a group you own."""
    _goto_mode(MODE_MODELLING)
    _input(["group_join", group_name, user_name])
    _handle_output("Success")

def group_kick(group_name, user_name):
    """Delete a user from a group you own."""
    _goto_mode(MODE_MODELLING)
    _input(["group_kick", group_name, user_name])
    _handle_output("Success")

def group_list():
    """List existing groups."""
    _goto_mode(MODE_MODELLING)
    _input(["group_list"])
    _handle_output("Success")

def admin_promote(user_name):
    """Promote a user to admin status."""
    _goto_mode(MODE_MODELLING)
    _input(["admin_promote", user_name])
    _handle_output("Success")

def admin_demote():
    """Demote a user from admin status."""
    _goto_mode(MODE_MODELLING)
    _input(["admin_demote", user_name])
    _handle_output("Success")

# Actual operations on the model
def element_list(model_name):
    """Return a list of all IDs and the type of the element"""
    _goto_mode(MODE_MODIFY, model_name)

    _input("list_full")
    lst = set([])
    output = _handle_output("Success: ", split=True)
    for v in output:
        m, mm = v.split(":")
        m = m.strip()
        mm = mm.strip()
        lst.add((m, mm))
    return lst

def types(model_name):
    """Return a list of all types usable in the model"""
    _goto_mode(MODE_MODIFY, model_name)

    _input("types")
    lst = set([])
    output = _handle_output("Success: ", split=True)
    for v in output:
        m, mm = v.split(":")
        m = m.strip()
        lst.add(m)
    return lst

def types_full(model_name):
    """Return a list of full types usable in the model"""
    _goto_mode(MODE_MODIFY, model_name)

    _input("types")
    lst = set([])
    output = _handle_output("Success: ", split=True)
    for v in output:
        m, mm = v.split(":")
        m = m.strip()
        mm = mm.strip()
        lst.add((m, mm))
    return lst

def read(model_name, ID):
    """Return a tuple of information on the element: its type and source/target (None if not an edge)"""
    _goto_mode(MODE_MODIFY, model_name)

    _input(["read", ID])
    v = _handle_output("Success: ", split=True)
    t = v[1].split(":")[1].strip()
    if (not v[2].startswith("Source:")):
        rval = (t, None)
    else:
        src = v[2].split(":")[1].strip()
        trg = v[3].split(":")[1].strip()
        rval = (t, (src, trg))
    return rval

def read_attrs(model_name, ID):
    """Return a dictionary of attribute value pairs"""
    _goto_mode(MODE_MODIFY, model_name)

    _input(["read", ID])
    output = _handle_output("Success: ", split=True)
    searching = True
    rval = {}
    for r in output:
        if searching:
            if r == "Attributes:":
                # Start working on attributes
                searching = False
        else:
            key, value = r.split(":", 1)
            _, value = value.split("=", 1)
            key = json.loads(key.strip())
            value = value.strip()
            if value == "None":
                value = None
            elif value == "True":
                value = True
            elif value == "False":
                value = False
            else:
                value = json.loads(value)
            rval[key] = value
    return rval

def instantiate(model_name, typename, edge=None, ID=""):
    """Create a new instance of the specified typename, between the selected elements (if not None), and with the provided ID (if any)"""
    _goto_mode(MODE_MODIFY, model_name)

    if edge is None:
        _input(["instantiate_node", typename, ID])
    else:
        _input(["instantiate_edge", typename, ID, edge[0], edge[1]])
    return _handle_output("Success: ", split=True)[0]

def delete_element(model_name, ID):
    """Delete the element with the given ID"""
    _goto_mode(MODE_MODIFY, model_name)

    _input(["delete", ID])
    _handle_output("Success")

def attr_assign(model_name, ID, attr, value):
    """Assign a value to an attribute"""
    _check_type(value)
    _goto_mode(MODE_MODIFY, model_name)

    _input(["attr_add", ID, attr, value])
    _handle_output("Success")

def attr_assign_code(model_name, ID, attr, code):
    """Assign a piece of Action Language code to the attribute"""
    _check_type(code)
    try:
        compiled = _compile_AL(code)
    except Exception as e:
        raise CompilationError(e)

    _goto_mode(MODE_MODIFY, model_name)

    _input(["attr_add", ID, attr])
    _handle_output("Waiting for code constructors...")
    _input(compiled)
    _output("Success")

def attr_delete(model_name, ID, attr):
    """Remove an attribute."""
    _goto_mode(MODE_MODIFY, model_name)

    _input(["attr_del", ID, attr])
    _handle_output("Success")

def read_outgoing(model_name, ID, typename):
    """Returns a list of all outgoing associations of a specific type ("" = all)"""
    _goto_mode(MODE_MODIFY, model_name)

    _input(["read_outgoing", ID, typename])
    output = _handle_output("Success: ", split=True)
    return set(output)

def read_incoming(model_name, ID, typename):
    """Returns a list of all incoming associations of a specific type ("" = all)"""
    _goto_mode(MODE_MODIFY, model_name)

    _input(["read_incoming", ID, typename])
    output = _handle_output("Success: ", split=True)
    return set(output)

def read_association_source(model_name, ID):
    """Returns the source of an association."""
    _goto_mode(MODE_MODIFY, model_name)

    _input(["read_association_source", ID])
    return _handle_output("Success: ", split=True)[0]

def read_association_destination(model_name, ID):
    """Returns the destination of an association."""
    _goto_mode(MODE_MODIFY, model_name)

    _input(["read_association_destination", ID])
    return _handle_output("Success: ", split=True)[0]

##### To document:

def service_register(name, function):
    """Register a function as a service with a specific name."""

    def service_process(port):
        while 1:
            thrd = threading.Thread(target=function, args=[service_get(port)])
            thrd.daemon = True
            thrd.start()

    global mode
    _goto_mode(MODE_MODELLING)

    _input(["service_register", name])

    # Now we are in service-mode
    mode = MODE_SERVICE
    port = _handle_output("Success: ", split=True)[0]

    # Process events in the background!
    threading.Thread(target=service_process, args=[port]).start()

def service_stop():
    """Stop the currently executing process."""
    _goto_mode(MODE_SERVICE)
    _input("service_stop")
    _handle_output("Success")

    global mode
    mode = MODE_MODELLING

def service_get(port):
    """Get the values on the specified port."""
    _goto_mode(MODE_SERVICE)

    return _output(port=port)

def service_set(port, value):
    """Set a value on a specified port."""
    _check_type_list(value)
    _goto_mode(MODE_SERVICE)

    _input(value, port=port)

def user_password(user, password):
    """Change a user's password."""
    raise NotImplementedError()

def transformation_read_signature(transformation):
    """Reads an operation's signature, specifying the names and their required types."""
    raise NotImplementedError()

def element_list_nice(model_name):
    """Fetches a nice representation of models."""
    _goto_mode(MODE_MODELLING)

    _input(["element_list_nice", model_name, _get_metamodel(model_name)])

    data = _handle_output("Success: ", split=True)[0]
    try:
        return json.loads(data)
    except:
        print(data)
        raise

def connections_between(model_name, source_element, target_element):
    """Gets a list of all allowed connections between the source and target element in the model."""
    _goto_mode(MODE_MODIFY, model_name)

    _input(["connections_between", source_element, target_element])
    output = _handle_output("Success: ", split=True)
    return set(output)

def define_attribute(model_name, node, attr_name, attr_type):
    """Create a new attribute, which can be instantiated one meta-level below."""
    _goto_mode(MODE_MODIFY, model_name)

    _input(["define_attribute", node, attr_name, attr_type])
    return _handle_output("Success: ", split=True)[0]

def all_instances(model_name, type_name):
    """Returns a list of all elements of a specific type."""
    _goto_mode(MODE_MODIFY, model_name)

    _input(["all_instances", type_name])
    output = _handle_output("Success: ", split=True)
    return set(output)

def service_poll(port):
    """Checks whether or not the Modelverse side has any input ready to be processed."""
    raise NotImplementedError()

def user_name(user, username):
    """Change a user's name."""
    raise NotImplementedError()

def remove_conformance(model_name, metamodel_name):
    """Remove a metamodel for a model."""
    _goto_mode(MODE_MODELLING)
    _input(["remove_conformance", model_name, metamodel_name])
    _handle_output("Success")

def add_conformance(model_name, metamodel_name, partial_type_mapping=None):
    """Add a metamodel for a model."""
    raise NotImplementedError()
    _goto_mode(MODE_MODELLING)
    _input(["add_conformance", model_name, metamodel_name])
    _handle_output("Success")

def folder_create(folder_name):
    _goto_mode(MODE_MODELLING)
    _input(["folder_create", folder_name])
    _handle_output("Success")