/****************************************************************************
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** Public License version 3.0 as published by the Free Software Foundation
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****************************************************************************/

#include "qwindowspipereader_p.h"
#include <qdebug.h>
#include <qelapsedtimer.h>
#include <qeventloop.h>
#include <qtimer.h>
#include <qwineventnotifier.h>

QT_BEGIN_NAMESPACE

QWindowsPipeReader::QWindowsPipeReader(QObject *parent)
    : QObject(parent),
      handle(INVALID_HANDLE_VALUE),
      readBufferMaxSize(0),
      actualReadBufferSize(0),
      emitReadyReadTimer(new QTimer(this)),
      pipeBroken(false)
{
    emitReadyReadTimer->setSingleShot(true);
    connect(emitReadyReadTimer, SIGNAL(timeout()), SIGNAL(readyRead()));

    ZeroMemory(&overlapped, sizeof(overlapped));
    overlapped.hEvent = CreateEvent(NULL, TRUE, FALSE, NULL);
    dataReadNotifier = new QWinEventNotifier(overlapped.hEvent, this);
    connect(dataReadNotifier, SIGNAL(activated(HANDLE)), SLOT(readEventSignalled()));
}

QWindowsPipeReader::~QWindowsPipeReader()
{
    CloseHandle(overlapped.hEvent);
}

/*!
    Sets the handle to read from. The handle must be valid.
 */
void QWindowsPipeReader::setHandle(HANDLE hPipeReadEnd)
{
    readBuffer.clear();
    actualReadBufferSize = 0;
    handle = hPipeReadEnd;
    pipeBroken = false;
    dataReadNotifier->setEnabled(true);
}

/*!
    Stops the asynchronous read sequence.
    This function assumes that the file already has been closed.
    It does not cancel any I/O operation.
 */
void QWindowsPipeReader::stop()
{
    dataReadNotifier->setEnabled(false);
    readSequenceStarted = false;
    handle = INVALID_HANDLE_VALUE;
    ResetEvent(overlapped.hEvent);
}

/*!
    Returns the number of bytes we've read so far.
 */
qint64 QWindowsPipeReader::bytesAvailable() const
{
    return actualReadBufferSize;
}

/*!
    Stops the asynchronous read sequence.
 */
qint64 QWindowsPipeReader::read(char *data, qint64 maxlen)
{
    if (pipeBroken && actualReadBufferSize == 0)
        return -1;  // signal EOF

    qint64 readSoFar;
    // If startAsyncRead() has read data, copy it to its destination.
    if (maxlen == 1 && actualReadBufferSize > 0) {
        *data = readBuffer.getChar();
        actualReadBufferSize--;
        readSoFar = 1;
    } else {
        qint64 bytesToRead = qMin(qint64(actualReadBufferSize), maxlen);
        readSoFar = 0;
        while (readSoFar < bytesToRead) {
            const char *ptr = readBuffer.readPointer();
            int bytesToReadFromThisBlock = qMin(bytesToRead - readSoFar,
                                                qint64(readBuffer.nextDataBlockSize()));
            memcpy(data + readSoFar, ptr, bytesToReadFromThisBlock);
            readSoFar += bytesToReadFromThisBlock;
            readBuffer.free(bytesToReadFromThisBlock);
            actualReadBufferSize -= bytesToReadFromThisBlock;
        }
    }

    if (!pipeBroken) {
        if (!actualReadBufferSize)
            emitReadyReadTimer->stop();
        if (!readSequenceStarted)
            startAsyncRead();
    }

    return readSoFar;
}

bool QWindowsPipeReader::canReadLine() const
{
    return readBuffer.indexOf('\n', actualReadBufferSize) >= 0;
}

/*!
    \internal
    Will be called whenever the read operation completes.
    Returns true, if readyRead() has been emitted.
 */
bool QWindowsPipeReader::readEventSignalled()
{
    if (!completeAsyncRead()) {
        pipeBroken = true;
        emit pipeClosed();
        return false;
    }
    startAsyncRead();
    emitReadyReadTimer->stop();
    emit readyRead();
    return true;
}

/*!
    \internal
    Reads data from the socket into the readbuffer
 */
void QWindowsPipeReader::startAsyncRead()
{
    do {
        DWORD bytesToRead = checkPipeState();
        if (pipeBroken)
            return;

        if (bytesToRead == 0) {
            // There are no bytes in the pipe but we need to
            // start the overlapped read with some buffer size.
            bytesToRead = initialReadBufferSize;
        }

        if (readBufferMaxSize && bytesToRead > (readBufferMaxSize - readBuffer.size())) {
            bytesToRead = readBufferMaxSize - readBuffer.size();
            if (bytesToRead == 0) {
                // Buffer is full. User must read data from the buffer
                // before we can read more from the pipe.
                return;
            }
        }

        char *ptr = readBuffer.reserve(bytesToRead);

        readSequenceStarted = true;
        if (ReadFile(handle, ptr, bytesToRead, NULL, &overlapped)) {
            completeAsyncRead();
        } else {
            switch (GetLastError()) {
                case ERROR_IO_PENDING:
                    // This is not an error. We're getting notified, when data arrives.
                    return;
                case ERROR_MORE_DATA:
                    // This is not an error. The synchronous read succeeded.
                    // We're connected to a message mode pipe and the message
                    // didn't fit into the pipe's system buffer.
                    completeAsyncRead();
                    break;
                case ERROR_PIPE_NOT_CONNECTED:
                    {
                        // It may happen, that the other side closes the connection directly
                        // after writing data. Then we must set the appropriate socket state.
                        pipeBroken = true;
                        emit pipeClosed();
                        return;
                    }
                default:
                    emit winError(GetLastError(), QLatin1String("QWindowsPipeReader::startAsyncRead"));
                    return;
            }
        }
    } while (!readSequenceStarted);
}

/*!
    \internal
    Sets the correct size of the read buffer after a read operation.
    Returns false, if an error occurred or the connection dropped.
 */
bool QWindowsPipeReader::completeAsyncRead()
{
    ResetEvent(overlapped.hEvent);
    readSequenceStarted = false;

    DWORD bytesRead;
    if (!GetOverlappedResult(handle, &overlapped, &bytesRead, TRUE)) {
        switch (GetLastError()) {
        case ERROR_MORE_DATA:
            // This is not an error. We're connected to a message mode
            // pipe and the message didn't fit into the pipe's system
            // buffer. We will read the remaining data in the next call.
            break;
        case ERROR_BROKEN_PIPE:
        case ERROR_PIPE_NOT_CONNECTED:
            return false;
        default:
            emit winError(GetLastError(), QLatin1String("QWindowsPipeReader::completeAsyncRead"));
            return false;
        }
    }

    actualReadBufferSize += bytesRead;
    readBuffer.truncate(actualReadBufferSize);
    if (!emitReadyReadTimer->isActive())
        emitReadyReadTimer->start();
    return true;
}

/*!
    \internal
    Returns the number of available bytes in the pipe.
    Sets QWindowsPipeReader::pipeBroken to true if the connection is broken.
 */
DWORD QWindowsPipeReader::checkPipeState()
{
    DWORD bytes;
    if (PeekNamedPipe(handle, NULL, 0, NULL, &bytes, NULL)) {
        return bytes;
    } else {
        if (!pipeBroken) {
            pipeBroken = true;
            emit pipeClosed();
        }
    }
    return 0;
}

/*!
    Waits for the completion of the asynchronous read operation.
    Returns true, if we've emitted the readyRead signal.
 */
bool QWindowsPipeReader::waitForReadyRead(int msecs)
{
    Q_ASSERT(readSequenceStarted);
    DWORD result = WaitForSingleObject(overlapped.hEvent, msecs == -1 ? INFINITE : msecs);
    switch (result) {
        case WAIT_OBJECT_0:
            return readEventSignalled();
        case WAIT_TIMEOUT:
            return false;
    }

    qWarning("QWindowsPipeReader::waitForReadyRead WaitForSingleObject failed with error code %d.", int(GetLastError()));
    return false;
}

/*!
    Waits until the pipe is closed.
 */
bool QWindowsPipeReader::waitForPipeClosed(int msecs)
{
    const int sleepTime = 10;
    QElapsedTimer stopWatch;
    stopWatch.start();
    forever {
        checkPipeState();
        if (pipeBroken)
            return true;
        if (stopWatch.hasExpired(msecs - sleepTime))
            return false;
        Sleep(sleepTime);
    }
}

QT_END_NAMESPACE