from PyQt5.QtCore import QTextStream, pyqtSignal
from PyQt5.QtNetwork import QLocalServer, QLocalSocket
from PyQt5.QtWidgets import QApplication


class QtSingleApplication(QApplication):
    """
    Adapted from https://stackoverflow.com/a/12712362/11038610

    Copyright 2013 Johan Råde

    Redistribution and use in source and binary forms, with or without
    modification, are permitted provided that the following conditions
    are met:

    1. Redistributions of source code must retain the above copyright
    notice, this list of conditions and the following disclaimer.

    2. Redistributions in binary form must reproduce the above
    copyright notice, this list of conditions and the following
    disclaimer in the documentation and/or other materials provided
    with the distribution.

    THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
    CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
    INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
    MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
    DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS
    BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
    EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED
    TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
    DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
    ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR
    TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF
    THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
    SUCH DAMAGE.

    """

    message_received_event = pyqtSignal(str)

    def __init__(self, id, *argv):

        super().__init__(*argv)
        self._id = id

        # Is there another instance running?
        self._outSocket = QLocalSocket()
        self._outSocket.connectToServer(self._id)
        self._isRunning = self._outSocket.waitForConnected()

        if self._isRunning:
            # Yes, there is.
            self._outStream = QTextStream(self._outSocket)
            self._outStream.setCodec('UTF-8')
        else:
            # No, there isn't.
            self._outSocket = None
            self._outStream = None
            self._inSocket = None
            self._inStream = None
            self._server = QLocalServer()
            self._server.removeServer(self._id)
            self._server.listen(self._id)
            self._server.newConnection.connect(self._onNewConnection)

    def isRunning(self):
        return self._isRunning

    def id(self):
        return self._id

    def sendMessage(self, msg):
        if not self._outStream:
            return False
        self._outStream << msg << '\n'
        self._outStream.flush()
        return self._outSocket.waitForBytesWritten()

    def _onNewConnection(self):
        if self._inSocket:
            self._inSocket.readyRead.disconnect(self._onReadyRead)
        self._inSocket = self._server.nextPendingConnection()
        if not self._inSocket:
            return
        self._inStream = QTextStream(self._inSocket)
        self._inStream.setCodec('UTF-8')
        self._inSocket.readyRead.connect(self._onReadyRead)

    def _onReadyRead(self):
        while True:
            msg = self._inStream.readLine()
            if not msg:
                break
            self.message_received_event.emit(msg)
