/*
 * Copyright (C) 1996-2023 The Squid Software Foundation and contributors
 *
 * Squid software is distributed under GPLv2+ license and includes
 * contributions from numerous individuals and organizations.
 * Please see the COPYING and CONTRIBUTORS files for details.
 */

#ifndef SQUID_SRC_BODYPIPE_H
#define SQUID_SRC_BODYPIPE_H

#include "base/AsyncJob.h"
#include "base/CbcPointer.h"
#include "MemBuf.h"

class BodyPipe;

/** Interface for those who want to produce body content for others.
 * BodyProducer is expected to create the BodyPipe.
 * One pipe cannot have more than one producer.
 */
class BodyProducer: virtual public AsyncJob
{
public:
    typedef CbcPointer<BodyProducer> Pointer;

    BodyProducer():AsyncJob("BodyProducer") {}
    ~BodyProducer() override {}

    virtual void noteMoreBodySpaceAvailable(RefCount<BodyPipe> bp) = 0;
    virtual void noteBodyConsumerAborted(RefCount<BodyPipe> bp) = 0;

protected:
    void stopProducingFor(RefCount<BodyPipe> &, bool atEof);
};

/** Interface for those who want to consume body content from others.
 * BodyConsumer is expected to register with an existing BodyPipe
 * by calling BodyPipe::setConsumer().
 * One pipe cannot have more than one consumer.
 */
class BodyConsumer: virtual public AsyncJob
{
public:
    typedef CbcPointer<BodyConsumer> Pointer;

    BodyConsumer():AsyncJob("BodyConsumer") {}
    ~BodyConsumer() override {}

    virtual void noteMoreBodyDataAvailable(RefCount<BodyPipe> bp) = 0;
    virtual void noteBodyProductionEnded(RefCount<BodyPipe> bp) = 0;
    virtual void noteBodyProducerAborted(RefCount<BodyPipe> bp) = 0;

protected:
    void stopConsumingFrom(RefCount<BodyPipe> &);
};

/** Makes raw buffer checkin/checkout interface efficient and exception-safe.
 * Either append or consume operations can be performed on a checkedout buffer.
 */
class BodyPipeCheckout
{
public:
    friend class BodyPipe;

public:
    BodyPipeCheckout(BodyPipe &); // checks out
    ~BodyPipeCheckout(); // aborts checkout unless checkedIn

    void checkIn();

public:
    BodyPipe &thePipe;
    MemBuf &buf;
    const uint64_t offset; // of current content, relative to the body start

protected:
    const size_t checkedOutSize;
    bool checkedIn;

private:
    BodyPipeCheckout(const BodyPipeCheckout &); // prevent copying
    BodyPipeCheckout &operator =(const BodyPipeCheckout &); // prevent assignment
};

/** Connects those who produces message body content with those who
 * consume it. For example, connects ConnStateData with FtpStateData OR
 * ICAPModXact with HttpStateData.
 */
class BodyPipe: public RefCountable
{
    MEMPROXY_CLASS(BodyPipe);

public:
    typedef RefCount<BodyPipe> Pointer;
    typedef BodyProducer Producer;
    typedef BodyConsumer Consumer;
    typedef BodyPipeCheckout Checkout;

    static constexpr size_t MaxCapacity = 64*1024;

    friend class BodyPipeCheckout;

public:
    BodyPipe(Producer *aProducer);
    ~BodyPipe() override; // asserts that producer and consumer are cleared

    void setBodySize(uint64_t aSize); // set body size
    bool bodySizeKnown() const { return theBodySize >= 0; }
    uint64_t bodySize() const;
    uint64_t consumedSize() const { return theGetSize; }
    uint64_t producedSize() const { return thePutSize; }
    bool productionEnded() const { return !theProducer; }

    // called by producers
    void clearProducer(bool atEof); // aborts or sends eof
    size_t putMoreData(const char *buf, size_t size);
    bool mayNeedMoreData() const { return !bodySizeKnown() || needsMoreData(); }
    bool needsMoreData() const { return bodySizeKnown() && unproducedSize() > 0; }
    uint64_t unproducedSize() const; // size of still unproduced data
    bool stillProducing(const Producer::Pointer &producer) const { return theProducer == producer; }
    void expectProductionEndAfter(uint64_t extraSize); ///< sets or checks body size

    // called by consumers
    bool setConsumerIfNotLate(const Consumer::Pointer &aConsumer);
    void clearConsumer(); // aborts if still piping
    void expectNoConsumption(); ///< there will be no more setConsumer() calls
    size_t getMoreData(MemBuf &buf);
    void consume(size_t size);
    bool expectMoreAfter(uint64_t offset) const;
    bool exhausted() const; // saw eof/abort and all data consumed
    bool stillConsuming(const Consumer::Pointer &consumer) const { return theConsumer == consumer; }

    /// start or continue consuming when producing without consumer
    void enableAutoConsumption();

    const MemBuf &buf() const { return theBuf; }

    const char *status() const; // for debugging only

protected:
    // lower-level interface used by Checkout
    MemBuf &checkOut(); // obtain raw buffer
    void checkIn(Checkout &checkout); // return updated raw buffer
    void undoCheckOut(Checkout &checkout); // undo checkout efffect

    void scheduleBodyDataNotification();
    void scheduleBodyEndNotification();

    // keep counters in sync and notify producer or consumer
    void postConsume(size_t size);
    void postAppend(size_t size);

    void startAutoConsumptionIfNeeded();

private:
    int64_t  theBodySize;   // expected total content length, if known
    Producer::Pointer theProducer; // content producer, if any
    Consumer::Pointer theConsumer; // content consumer, if any

    uint64_t thePutSize; // ever-increasing total
    uint64_t theGetSize; // ever-increasing total

    MemBuf theBuf; // produced but not yet consumed content, if any

    bool mustAutoConsume; ///< keep theBuf empty when producing without consumer
    bool abortedConsumption; ///< called BodyProducer::noteBodyConsumerAborted
    bool isCheckedOut; // to keep track of checkout violations
};

#endif /* SQUID_SRC_BODYPIPE_H */