ODrive/tools/odrive/remote_object.py

"""
Provides functions for the discovery of ODrive devices
"""

import sys
import json
import struct
import threading
import odrive.protocol

#class ObjectDisappearedError(Exception):
#    def __init__(self, channel):
#        self._obj = obj
#    pass

class ObjectDefinitionError(Exception):
    pass

class RemoteProperty():
    """
    Used internally by dynamically created objects to translate
    property assignments and fetches into endpoint operations on the
    object's associated channel
    """
    def __init__(self, json_data, parent):
        self._parent = parent
        id_str = json_data.get("id", None)
        if id_str is None:
            raise ObjectDefinitionError("unspecified endpoint ID")
        self._id = int(id_str)

        self._name = json_data.get("name", None)
        if self._name is None:
            self._name = "[anonymous]"

        type_str = json_data.get("type", None)
        if type_str is None:
            raise ObjectDefinitionError("unspecified type")

        if type_str == "float":
            self._property_type = float
            self._struct_format = "<f"
        elif type_str == "bool":
            self._property_type = bool
            self._struct_format = "<?"
        elif type_str == "int8":
            self._property_type = int
            self._struct_format = "<b"
        elif type_str == "uint8":
            self._property_type = int
            self._struct_format = "<B"
        elif type_str == "int16":
            self._property_type = int
            self._struct_format = "<h"
        elif type_str == "uint16":
            self._property_type = int
            self._struct_format = "<H"
        elif type_str == "int32":
            self._property_type = int
            self._struct_format = "<i"
        elif type_str == "uint32":
            self._property_type = int
            self._struct_format = "<I"
        elif type_str == "int64":
            self._property_type = int
            self._struct_format = "<q"
        elif type_str == "uint64":
            self._property_type = int
            self._struct_format = "<Q"
        else:
            raise ObjectDefinitionError("unsupported type {}".format(type_str))

        access_mode = json_data.get("access", "r")
        self._can_read = 'r' in access_mode
        self._can_write = 'w' in access_mode

    def get_value(self):
        size = struct.calcsize(self._struct_format)
        buffer = self._parent.__channel__.remote_endpoint_operation(self._id, None, True, size)
        return struct.unpack(self._struct_format, buffer)[0]

    def set_value(self, value):
        value = self._property_type(value)
        buffer = struct.pack(self._struct_format, value)
        # TODO: Currenly we wait for an ack here. Settle on the default guarantee.
        self._parent.__channel__.remote_endpoint_operation(self._id, buffer, True, 0)

class RemoteFunction(object):
    """
    Represents a callable function that maps to a function call on a remote object
    """
    def __init__(self, json_data, parent):
        self._parent = parent
        id_str = json_data.get("id", None)
        if id_str is None:
            raise ObjectDefinitionError("unspecified endpoint ID")
        self._trigger_id = int(id_str)

        self._inputs = []
        for param_json in json_data.get("arguments", []) + json_data.get("inputs", []): # TODO: deprecate "arguments" keyword
            param_json["mode"] = "r"
            self._inputs.append(RemoteProperty(param_json, parent))

    def __call__(self, *args):
        if (len(self._inputs) != len(args)):
            raise TypeError("expected {} arguments but have {}".format(len(self._inputs), len(args)))
        for i in range(len(args)):
            self._inputs[i].set_value(args[i])
        self._parent.__channel__.remote_endpoint_operation(self._trigger_id, None, True, 0)

class RemoteObject(object):
    """
    Object with functions and properties that map to remote endpoints
    """
    def __init__(self, json_data, parent, channel, printer):
        """
        Creates an object that implements the specified JSON type description by
        communicating over the provided channel
        """
        # Directly write to __dict__ to avoid calling __setattr__ too early
        object.__getattribute__(self, "__dict__")["_remote_attributes"] = {}
        object.__getattribute__(self, "__dict__")["__sealed__"] = False
        # Assign once more to make linter happy
        self._remote_attributes = {}
        self.__sealed__ = False

        self.__channel__ = channel
        self.__parent__ = parent

        # Build attribute list from JSON
        for member_json in json_data.get("members", []):
            member_name = member_json.get("name", None)
            if member_name is None:
                printer("ignoring unnamed attribute")
                continue

            try:
                type_str = member_json.get("type", None)
                if type_str == "object":
                    attribute = RemoteObject(member_json, self, channel, printer)
                elif type_str == "function":
                    attribute = RemoteFunction(member_json, self)
                elif type_str != None:
                    attribute = RemoteProperty(member_json, self)
                else:
                    raise ObjectDefinitionError("no type information")
            except ObjectDefinitionError as ex:
                printer("malformed member {}: {}".format(member_name, str(ex)))
                continue

            self._remote_attributes[member_name] = attribute
            self.__dict__[member_name] = attribute

        # Ensure that from here on out assignments to undefined attributes
        # raise an exception
        self.__sealed__ = True
        channel._channel_broken.subscribe(self._tear_down)

    def __str__(self):
        return str(dir(self)) # TODO: improve print output
    def __repr__(self):
        return self.__str__()

    def __getattribute__(self, name):
        attr = object.__getattribute__(self, "_remote_attributes").get(name, None)
        if isinstance(attr, RemoteProperty):
            if attr._can_read:
                return attr.get_value()
            else:
                raise Exception("Cannot read from property {}".format(name))
        elif attr != None:
            return attr
        else:
            return object.__getattribute__(self, name)
            #raise AttributeError("Attribute {} not found".format(name))

    def __setattr__(self, name, value):
        attr = object.__getattribute__(self, "_remote_attributes").get(name, None)
        if isinstance(attr, RemoteProperty):
            if attr._can_write:
                attr.set_value(value)
            else:
                raise Exception("Cannot write to property {}".format(name))
        elif not object.__getattribute__(self, "__sealed__") or name in object.__getattribute__(self, "__dict__"):
            object.__getattribute__(self, "__dict__")[name] = value
        else:
            raise AttributeError("Attribute {} not found".format(name))

    def _tear_down(self):
        # Clear all remote members
        for k in self._remote_attributes.keys():
            self.__dict__.pop(k)
        self._remote_attributes = {}