# Copyright (c) 2017 Ultimaker B.V.
# Uranium is released under the terms of the LGPLv3 or higher.

from enum import IntEnum

from UM.Backend.SignalSocket import SignalSocket
from UM.Preferences import Preferences
from UM.Logger import Logger
from UM.Signal import Signal, signalemitter
from UM.Application import Application
from UM.PluginObject import PluginObject
from UM.Platform import Platform

import Arcus

import struct
import subprocess
import threading
import sys
from time import sleep

##  The current processing state of the backend.
class BackendState(IntEnum):
    NotStarted = 1
    Processing = 2
    Done = 3
    Error = 4
    Disabled = 5


##      Base class for any backend communication (separate piece of software).
#       It makes use of the Socket class from libArcus for the actual communication bits.
#       The message_handlers dict should be filled with string (full name of proto message), function pairs.
@signalemitter
class Backend(PluginObject):
    def __init__(self):
        super().__init__()  # Call super to make multiple inheritance work.
        self._supported_commands = {}

        self._message_handlers = {}

        self._socket = None
        self._port = 49674
        self._process = None
        self._backend_log = []
        self._backend_log_max_lines = None

        Application.getInstance().callLater(self._createSocket)

    processingProgress = Signal()
    backendStateChange = Signal()
    backendConnected = Signal()
    backendQuit = Signal()

    ##   \brief Start the backend / engine.
    #   Runs the engine, this is only called when the socket is fully opened & ready to accept connections
    def startEngine(self):
        try:
            command = self.getEngineCommand()
            if not command:
                self._createSocket()
                return

            if not self._backend_log_max_lines:
                self._backend_log = []

            # Double check that the old process is indeed killed.
            if self._process is not None:
                self._process.terminate()
                Logger.log("d", "Engine process is killed. Received return code %s", self._process.wait())

            self._process = self._runEngineProcess(command)
            if self._process is None: #Failed to start engine.
                return
            Logger.log("i", "Started engine process: %s", self.getEngineCommand()[0])
            self._backendLog(bytes("Calling engine with: %s\n" % self.getEngineCommand(), "utf-8"))
            t = threading.Thread(target = self._storeOutputToLogThread, args = (self._process.stdout,))
            t.daemon = True
            t.start()
            t = threading.Thread(target = self._storeStderrToLogThread, args = (self._process.stderr,))
            t.daemon = True
            t.start()
        except FileNotFoundError as e:
            Logger.log("e", "Unable to find backend executable: %s", self.getEngineCommand()[0])

    def close(self):
        if self._socket:
            while self._socket.getState() == Arcus.SocketState.Opening:
                sleep(0.1)
            self._socket.close()

    def _backendLog(self, line):
        Logger.log('d', "[Backend] " + str(line, encoding="utf-8").strip())
        self._backend_log.append(line)

    ##  Get the logging messages of the backend connection.
    #   \returns  
    def getLog(self):
        if self._backend_log_max_lines and type(self._backend_log_max_lines) == int:
            while len(self._backend_log) >= self._backend_log_max_lines:
                del(self._backend_log[0])
        return self._backend_log

    ##  \brief Convert byte array containing 3 floats per vertex
    def convertBytesToVerticeList(self, data):
        result = []
        if not (len(data) % 12):
            if data is not None:
                for index in range(0, int(len(data) / 12)):  # For each 12 bits (3 floats)
                    result.append(struct.unpack("fff", data[index * 12: index * 12 + 12]))
                return result
        else:
            Logger.log("e", "Data length was incorrect for requested type")
            return None
    
    ##  \brief Convert byte array containing 6 floats per vertex
    def convertBytesToVerticeWithNormalsList(self,data):
        result = []
        if not (len(data) % 24):
            if data is not None:
                for index in range(0,int(len(data)/24)):  # For each 24 bits (6 floats)
                    result.append(struct.unpack("ffffff", data[index * 24: index * 24 + 24]))
                return result
        else:
            Logger.log("e", "Data length was incorrect for requested type")
            return None
    
    ##  Get the command used to start the backend executable 
    def getEngineCommand(self):
        return [Preferences.getInstance().getValue("backend/location"), "--port", str(self._socket.getPort())]

    ##  Start the (external) backend process.
    def _runEngineProcess(self, command_list):
        kwargs = {}
        if sys.platform == "win32":
            su = subprocess.STARTUPINFO()
            su.dwFlags |= subprocess.STARTF_USESHOWWINDOW
            su.wShowWindow = subprocess.SW_HIDE
            kwargs["startupinfo"] = su
            kwargs["creationflags"] = 0x00004000  # BELOW_NORMAL_PRIORITY_CLASS
        try:
            return subprocess.Popen(command_list, stdin = subprocess.DEVNULL, stdout = subprocess.PIPE, stderr = subprocess.PIPE, **kwargs)
        except PermissionError:
            Logger.log("e", "Couldn't start back-end: No permission to execute process.")

    def _storeOutputToLogThread(self, handle):
        while True:
            line = handle.readline()
            if line == b"":
                self.backendQuit.emit()
                break
            self._backendLog(line)

    def _storeStderrToLogThread(self, handle):
        while True:
            line = handle.readline()
            if line == b"":
                break
            self._backendLog(line)

    ##  Private socket state changed handler.
    def _onSocketStateChanged(self, state):
        self._logSocketState(state)
        if state == Arcus.SocketState.Listening:
            if not Application.getInstance().getCommandLineOption("external-backend", False):
                self.startEngine()
        elif state == Arcus.SocketState.Connected:
            Logger.log("d", "Backend connected on port %s", self._port)
            self.backendConnected.emit()

    ## Debug function created to provide more info for CURA-2127
    def _logSocketState(self, state):
        if state == Arcus.SocketState.Listening:
            Logger.log("d", "Socket state changed to Listening")
        elif state == Arcus.SocketState.Connecting:
            Logger.log("d", "Socket state changed to Connecting")
        elif state == Arcus.SocketState.Connected:
            Logger.log("d", "Socket state changed to Connected")
        elif state == Arcus.SocketState.Error:
            Logger.log("d", "Socket state changed to Error")
        elif state == Arcus.SocketState.Closing:
            Logger.log("d", "Socket state changed to Closing")
        elif state == Arcus.SocketState.Closed:
            Logger.log("d", "Socket state changed to Closed")

    ##  Private message handler
    def _onMessageReceived(self):
        message = self._socket.takeNextMessage()

        if message.getTypeName() not in self._message_handlers:
            Logger.log("e", "No handler defined for message of type %s", message.getTypeName())
            return

        self._message_handlers[message.getTypeName()](message)
    
    ##  Private socket error handler   
    def _onSocketError(self, error):
        if error.getErrorCode() == Arcus.ErrorCode.BindFailedError:
            self._port += 1
            Logger.log("d", "Socket was unable to bind to port, increasing port number to %s", self._port)
        elif error.getErrorCode() == Arcus.ErrorCode.ConnectionResetError:
            Logger.log("i", "Backend crashed or closed.")
        elif error.getErrorCode() == Arcus.ErrorCode.Debug:
            Logger.log("d", "Socket debug: %s", str(error))
            return
        else:
            Logger.log("w", "Unhandled socket error %s", str(error))

        self._createSocket()

    ##  Creates a socket and attaches listeners.
    def _createSocket(self, protocol_file):
        if self._socket:
            Logger.log("d", "Previous socket existed. Closing that first.") # temp debug logging
            self._socket.stateChanged.disconnect(self._onSocketStateChanged)
            self._socket.messageReceived.disconnect(self._onMessageReceived)
            self._socket.error.disconnect(self._onSocketError)
            # Hack for (at least) Linux. If the socket is connecting, the close will deadlock.
            while self._socket.getState() == Arcus.SocketState.Opening:
                sleep(0.1)
            # If the error occurred due to parsing, both connections believe that connection is okay.
            # So we need to force a close.
            self._socket.close()

        self._socket = SignalSocket()
        self._socket.stateChanged.connect(self._onSocketStateChanged)
        self._socket.messageReceived.connect(self._onMessageReceived)
        self._socket.error.connect(self._onSocketError)
        
        if Platform.isWindows():
            # On Windows, the Protobuf DiskSourceTree does stupid things with paths.
            # So convert to forward slashes here so it finds the proto file properly.
            protocol_file = protocol_file.replace("\\", "/")

        if not self._socket.registerAllMessageTypes(protocol_file):
            Logger.log("e", "Could not register Uranium protocol messages: %s", self._socket.getLastError())

        if Application.getInstance().getCommandLineOption("external-backend", False):
            Logger.log("i", "Listening for backend connections on %s", self._port)

        self._socket.listen("127.0.0.1", self._port)

