/*
 * 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_MEMOBJECT_H
#define SQUID_SRC_MEMOBJECT_H

#include "base/DelayedAsyncCalls.h"
#include "dlink.h"
#include "http/RequestMethod.h"
#include "HttpReply.h"
#include "RemovalPolicy.h"
#include "sbuf/SBuf.h"
#include "stmem.h"
#include "store/forward.h"
#include "StoreIOBuffer.h"
#include "StoreIOState.h"
#include "typedefs.h" //for IRCB

#if USE_DELAY_POOLS
#include "DelayId.h"
#endif

typedef void STMCB (void *data, StoreIOBuffer wroteBuffer);

class store_client;
class PeerSelector;

class MemObject
{
    MEMPROXY_CLASS(MemObject);

public:
    static size_t inUseCount();

    void dump() const;
    MemObject();
    ~MemObject();

    /// Sets store ID, log URI, and request method (unless already set). Does
    /// not clobber the method so that, say, a HEAD hit for a GET entry keeps
    /// the GET method that matches the entry key. Same for the other parts of
    /// the trio because the entry filling code may expect them to be constant.
    /// XXX: Avoid this method. We plan to remove it and make the trio constant
    /// after addressing the XXX in MemStore::get().
    void setUris(char const *aStoreId, char const *aLogUri, const HttpRequestMethod &aMethod);

    /// whether setUris() has been called
    bool hasUris() const;

    void write(const StoreIOBuffer &buf);
    void unlinkRequest() { request = nullptr; }

    /// HTTP response before 304 (Not Modified) updates
    /// starts "empty"; modified via replaceBaseReply() or adjustableBaseReply()
    const HttpReply &baseReply() const { return *reply_; }

    /// \returns nil -- if no 304 updates since replaceBaseReply()
    /// \returns combination of baseReply() and 304 updates -- after updates
    const HttpReplyPointer &updatedReply() const { return updatedReply_; }

    /// \returns the updated-by-304(s) response (if it exists)
    /// \returns baseReply() (otherwise)
    const HttpReply &freshestReply() const {
        if (updatedReply_)
            return *updatedReply_;
        else
            return baseReply();
    }

    /// \returns writable base reply for parsing and other initial modifications
    /// Base modifications can only be done when forming/loading the entry.
    /// After that, use replaceBaseReply() to reset all of the replies.
    HttpReply &adjustableBaseReply();

    /// (re)sets base reply, usually just replacing the initial/empty object
    /// also forgets the updated reply (if any)
    void replaceBaseReply(const HttpReplyPointer &r);

    /// (re)sets updated reply; \see updatedReply()
    void updateReply(const HttpReply &r) { updatedReply_ = &r; }

    /// reflects past Controller::updateOnNotModified(old, e304) calls:
    /// for HTTP 304 entries: whether our entry was used as "e304"
    /// for other entries: whether our entry was updated as "old"
    bool appliedUpdates = false;

    void stat (MemBuf * mb) const;

    /// The offset of the last memory-stored HTTP response byte plus one.
    /// * HTTP response headers (if any) are stored at offset zero.
    /// * HTTP response body byte[n] usually has offset (hdr_sz + n), where
    ///   hdr_sz is the size of stored HTTP response headers (zero if none); and
    ///   n is the corresponding byte offset in the whole resource body.
    ///   However, some 206 (Partial Content) response bodies are stored (and
    ///   retrieved) as regular 200 response bodies, disregarding offsets of
    ///   their body parts. \sa HttpStateData::decideIfWeDoRanges().
    int64_t endOffset () const;

    /// sets baseReply().hdr_sz (i.e. written reply headers size) to endOffset()
    void markEndOfReplyHeaders();

    /// negative if unknown; otherwise, expected object_sz, expected endOffset
    /// maximum, and stored reply headers+body size (all three are the same)
    int64_t expectedReplySize() const;
    int64_t size() const;
    void reset();
    int64_t lowestMemReaderOffset() const;
    bool readAheadPolicyCanRead() const;
    void addClient(store_client *);
    /* XXX belongs in MemObject::swapout, once swaphdrsz is managed
     * better
     */
    int64_t objectBytesOnDisk() const;
    int64_t policyLowestOffsetToKeep(bool swap) const;
    int64_t availableForSwapOut() const; ///< buffered bytes we have not swapped out yet
    void trimSwappable();
    void trimUnSwappable();
    bool isContiguous() const;
    int mostBytesWanted(int max, bool ignoreDelayPools) const;
    void setNoDelay(bool const newValue);
#if USE_DELAY_POOLS
    DelayId mostBytesAllowed() const;
#endif

#if URL_CHECKSUM_DEBUG

    void checkUrlChecksum() const;
#endif

    /// Before StoreID, code assumed that MemObject stores Request URI.
    /// After StoreID, some old code still incorrectly assumes that.
    /// Use this method to mark that incorrect assumption.
    const char *urlXXX() const { return storeId(); }

    /// Entry StoreID (usually just Request URI); if a buggy code requests this
    /// before the information is available, returns an "[unknown_URI]" string.
    const char *storeId() const;

    /// client request URI used for logging; storeId() by default
    const char *logUri() const;

    HttpRequestMethod method;
    mem_hdr data_hdr;
    int64_t inmem_lo = 0;
    dlink_list clients;

    size_t clientCount() const {return nclients;}

    bool clientIsFirst(void *sc) const {return (clients.head && sc == clients.head->data);}

    int nclients = 0;

    class SwapOut
    {
    public:
        int64_t queue_offset = 0; ///< number of bytes sent to SwapDir for writing
        StoreIOState::Pointer sio;

        /// Decision states for StoreEntry::swapoutPossible() and related code.
        typedef enum { swNeedsCheck = 0, swImpossible = -1, swPossible = +1, swStarted } Decision;
        Decision decision = swNeedsCheck; ///< current decision state
    };

    SwapOut swapout;

    /* TODO: Remove this change-minimizing hack */
    using Io = Store::IoStatus;
    static constexpr Io ioUndecided = Store::ioUndecided;
    static constexpr Io ioReading = Store::ioReading;
    static constexpr Io ioWriting = Store::ioWriting;
    static constexpr Io ioDone = Store::ioDone;

    /// State of an entry with regards to the [shared] in-transit table.
    class XitTable
    {
    public:
        /// associate our StoreEntry with a Transients entry at the given index
        void open(const int32_t anIndex, const Io anIo)
        {
            index = anIndex;
            io = anIo;
        }

        /// stop associating our StoreEntry with a Transients entry
        void close()
        {
            index = -1;
            io = Store::ioDone;
        }

        int32_t index = -1; ///< entry position inside the in-transit table
        Io io = ioUndecided; ///< current I/O state
    };
    XitTable xitTable; ///< current [shared] memory caching state for the entry

    /// State of an entry with regards to the [shared] memory caching.
    class MemCache
    {
    public:
        int32_t index = -1; ///< entry position inside the memory cache
        int64_t offset = 0; ///< bytes written/read to/from the memory cache so far

        Io io = ioUndecided; ///< current I/O state
    };
    MemCache memCache; ///< current [shared] memory caching state for the entry

    HttpRequestPointer request;

    struct timeval start_ping;
    IRCB *ping_reply_callback;
    PeerSelector *ircb_data = nullptr;

    /// used for notifying StoreEntry writers about 3rd-party initiated aborts
    AsyncCallPointer abortCallback;
    RemovalPolicyNode repl;
    int id = 0;
    int64_t object_sz = -1;
    size_t swap_hdr_sz = 0;
#if URL_CHECKSUM_DEBUG
    unsigned int chksum = 0;
#endif

    SBuf vary_headers;

    void delayRead(const AsyncCallPointer &);
    void kickReads();

private:
    HttpReplyPointer reply_; ///< \see baseReply()
    HttpReplyPointer updatedReply_; ///< \see updatedReply()

    mutable SBuf storeId_; ///< StoreId for our entry (usually request URI)
    mutable SBuf logUri_;  ///< URI used for logging (usually request URI)

    DelayedAsyncCalls deferredReads;
};

/** global current memory removal policy */
extern RemovalPolicy *mem_policy;

#endif /* SQUID_SRC_MEMOBJECT_H */