/*
  ==============================================================================

   This file is part of the JUCE library.
   Copyright (c) 2016 - ROLI Ltd.

   Permission is granted to use this software under the terms of the ISC license
   http://www.isc.org/downloads/software-support-policy/isc-license/

   Permission to use, copy, modify, and/or distribute this software for any
   purpose with or without fee is hereby granted, provided that the above
   copyright notice and this permission notice appear in all copies.

   THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES WITH REGARD
   TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND
   FITNESS. IN NO EVENT SHALL ISC BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT,
   OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF
   USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER
   TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE
   OF THIS SOFTWARE.

   -----------------------------------------------------------------------------

   To release a closed-source product which uses other parts of JUCE not
   licensed under the ISC terms, commercial licenses are available: visit
   www.juce.com for more information.

  ==============================================================================
*/

enum { magicMastSlaveConnectionHeader = 0x712baf04 };

static const char* startMessage = "__ipc_st";
static const char* killMessage  = "__ipc_k_";
static const char* pingMessage  = "__ipc_p_";
enum { specialMessageSize = 8, defaultTimeoutMs = 8000 };

static String getCommandLinePrefix (const String& commandLineUniqueID)
{
    return "--" + commandLineUniqueID + ":";
}

//==============================================================================
// This thread sends and receives ping messages every second, so that it
// can find out if the other process has stopped running.
struct ChildProcessPingThread  : public Thread,
                                 private AsyncUpdater
{
    ChildProcessPingThread (int timeout)  : Thread ("IPC ping"), timeoutMs (timeout)
    {
        pingReceived();
    }

    static bool isPingMessage (const MemoryBlock& m) noexcept
    {
        return memcmp (m.getData(), pingMessage, specialMessageSize) == 0;
    }

    void pingReceived() noexcept            { countdown = timeoutMs / 1000 + 1; }
    void triggerConnectionLostMessage()     { triggerAsyncUpdate(); }

    virtual bool sendPingMessage (const MemoryBlock&) = 0;
    virtual void pingFailed() = 0;

    int timeoutMs;

private:
    Atomic<int> countdown;

    void handleAsyncUpdate() override   { pingFailed(); }

    void run() override
    {
        while (! threadShouldExit())
        {
            if (--countdown <= 0 || ! sendPingMessage (MemoryBlock (pingMessage, specialMessageSize)))
            {
                triggerConnectionLostMessage();
                break;
            }

            wait (1000);
        }
    }

    JUCE_DECLARE_NON_COPYABLE_WITH_LEAK_DETECTOR (ChildProcessPingThread)
};

//==============================================================================
struct ChildProcessMaster::Connection  : public InterprocessConnection,
                                         private ChildProcessPingThread
{
    Connection (ChildProcessMaster& m, const String& pipeName, int timeout)
        : InterprocessConnection (false, magicMastSlaveConnectionHeader),
          ChildProcessPingThread (timeout),
          owner (m)
    {
        if (createPipe (pipeName, timeoutMs))
            startThread (4);
    }

    ~Connection()
    {
        stopThread (10000);
    }

private:
    void connectionMade() override  {}
    void connectionLost() override  { owner.handleConnectionLost(); }

    bool sendPingMessage (const MemoryBlock& m) override    { return owner.sendMessageToSlave (m); }
    void pingFailed() override                              { connectionLost(); }

    void messageReceived (const MemoryBlock& m) override
    {
        pingReceived();

        if (m.getSize() != specialMessageSize || ! isPingMessage (m))
            owner.handleMessageFromSlave (m);
    }

    ChildProcessMaster& owner;

    JUCE_DECLARE_NON_COPYABLE_WITH_LEAK_DETECTOR (Connection)
};

//==============================================================================
ChildProcessMaster::ChildProcessMaster() {}

ChildProcessMaster::~ChildProcessMaster()
{
    if (connection != nullptr)
    {
        sendMessageToSlave (MemoryBlock (killMessage, specialMessageSize));
        connection->disconnect();
        connection = nullptr;
    }
}

void ChildProcessMaster::handleConnectionLost() {}

bool ChildProcessMaster::sendMessageToSlave (const MemoryBlock& mb)
{
    if (connection != nullptr)
        return connection->sendMessage (mb);

    jassertfalse; // this can only be used when the connection is active!
    return false;
}

bool ChildProcessMaster::launchSlaveProcess (const File& executable, const String& commandLineUniqueID, int timeoutMs, int streamFlags)
{
    connection = nullptr;
    jassert (childProcess.kill());

    const String pipeName ("p" + String::toHexString (Random().nextInt64()));

    StringArray args;
    args.add (executable.getFullPathName());
    args.add (getCommandLinePrefix (commandLineUniqueID) + pipeName);

    if (childProcess.start (args, streamFlags))
    {
        connection = new Connection (*this, pipeName, timeoutMs <= 0 ? defaultTimeoutMs : timeoutMs);

        if (connection->isConnected())
        {
            sendMessageToSlave (MemoryBlock (startMessage, specialMessageSize));
            return true;
        }

        connection = nullptr;
    }

    return false;
}

//==============================================================================
struct ChildProcessSlave::Connection  : public InterprocessConnection,
                                        private ChildProcessPingThread
{
    Connection (ChildProcessSlave& p, const String& pipeName, int timeout)
        : InterprocessConnection (false, magicMastSlaveConnectionHeader),
          ChildProcessPingThread (timeout),
          owner (p)
    {
        connectToPipe (pipeName, timeoutMs);
        startThread (4);
    }

    ~Connection()
    {
        stopThread (10000);
    }

private:
    ChildProcessSlave& owner;

    void connectionMade() override  {}
    void connectionLost() override  { owner.handleConnectionLost(); }

    bool sendPingMessage (const MemoryBlock& m) override    { return owner.sendMessageToMaster (m); }
    void pingFailed() override                              { connectionLost(); }

    void messageReceived (const MemoryBlock& m) override
    {
        pingReceived();

        if (m.getSize() == specialMessageSize)
        {
            if (isPingMessage (m))
                return;

            if (memcmp (m.getData(), killMessage, specialMessageSize) == 0)
            {
                triggerConnectionLostMessage();
                return;
            }

            if (memcmp (m.getData(), startMessage, specialMessageSize) == 0)
            {
                owner.handleConnectionMade();
                return;
            }
        }

        owner.handleMessageFromMaster (m);
    }

    JUCE_DECLARE_NON_COPYABLE_WITH_LEAK_DETECTOR (Connection)
};

//==============================================================================
ChildProcessSlave::ChildProcessSlave() {}
ChildProcessSlave::~ChildProcessSlave() {}

void ChildProcessSlave::handleConnectionMade() {}
void ChildProcessSlave::handleConnectionLost() {}

bool ChildProcessSlave::sendMessageToMaster (const MemoryBlock& mb)
{
    if (connection != nullptr)
        return connection->sendMessage (mb);

    jassertfalse; // this can only be used when the connection is active!
    return false;
}

bool ChildProcessSlave::initialiseFromCommandLine (const String& commandLine,
                                                   const String& commandLineUniqueID,
                                                   int timeoutMs)
{
    String prefix (getCommandLinePrefix (commandLineUniqueID));

    if (commandLine.trim().startsWith (prefix))
    {
        String pipeName (commandLine.fromFirstOccurrenceOf (prefix, false, false)
                                    .upToFirstOccurrenceOf (" ", false, false).trim());

        if (pipeName.isNotEmpty())
        {
            connection = new Connection (*this, pipeName, timeoutMs <= 0 ? defaultTimeoutMs : timeoutMs);

            if (! connection->isConnected())
                connection = nullptr;
        }
    }

    return connection != nullptr;
}