#include "autoconfig.h"

#ifdef RCL_MONITOR
/* Copyright (C) 2006-2022 J.F.Dockes 
 *   This program is free software; you can redistribute it and/or modify
 *   it under the terms of the GNU General Public License as published by
 *   the Free Software Foundation; either version 2 of the License, or
 *   (at your option) any later version.
 *
 *   This program is distributed in the hope that it will be useful,
 *   but WITHOUT ANY WARRANTY; without even the implied warranty of
 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *   GNU General Public License for more details.
 *
 *   You should have received a copy of the GNU General Public License
 *   along with this program; if not, write to the
 *   Free Software Foundation, Inc.,
 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 */

/**
 * Recoll real time monitor processing. This file has the code to retrieve
 * event from the event queue and do the database-side processing. Also the 
 * initialization function.
 */

#include <errno.h>
#include <fnmatch.h>
#include "safeunistd.h"

#include <cstring>
#include <cstdio>
#include <cstdlib>
#include <list>
#include <vector>
#include <thread>
#include <mutex>
#include <condition_variable>
#include <chrono>

using std::list;
using std::vector;

#include "log.h"
#include "rclmon.h"
#include "log.h"

#include "execmd.h"
#include "recollindex.h"
#include "pathut.h"
#ifndef _WIN32
#include "x11mon.h"
#endif
#include "subtreelist.h"

typedef unsigned long mttcast;

// Seconds between auxiliary db (stem, spell) updates:
static const int dfltauxinterval = 60 *60;
static int auxinterval = dfltauxinterval;

// Seconds between indexing queue processing: for merging events to 
// fast changing files and saving some of the indexing overhead.
static const int dfltixinterval = 30;
static int ixinterval = dfltixinterval;

static RclMonEventQueue rclEQ;

// 
// Delayed events: this is a special feature for fast changing files.
// A list of pattern/delays can be specified in the configuration so
// that they don't get re-indexed before some timeout is elapsed. Such
// events are kept on a separate queue (m_dqueue) with an auxiliary
// list in time-to-reindex order, while the normal events are on
// m_iqueue.

// Queue management performance: on a typical recoll system there will
// be only a few entries on the event queues and no significant time
// will be needed to manage them. Even on a busy system, the time used
// would most probably be negligible compared to the actual processing
// of the indexing events. So this is just for reference. Let I be the
// number of immediate events and D the number of delayed ones, N
// stands for either.
//
// Periodic timeout polling: the recollindex process periodically (2S)
// wakes up to check for exit requests. At this time it also checks
// the queues for new entries (should not happen because the producer
// would normally wake up the consumer threads), or ready entries
// among the delayed ones. At this time it calls the "empty()"
// routine. This has constant time behaviour (checks for stl container
// emptiness and the top entry of the delays list).
//
// Adding a new event (pushEvent()): this performs a search for an
// existing event with the same path (O(log(N)), then an insert on the
// appropriate queue (O(log(N))) and an insert on the times list (O(D)). 
//  
// Popping an event: this is constant time as it just looks at the
// tops of the normal and delayed queues.


// Indexing event container: a map indexed by file path for fast
// insertion of duplicate events to the same file
typedef map<string, RclMonEvent> queue_type;

// Entries for delayed events are duplicated (as iterators) on an
// auxiliary, sorted by time-to-reindex list. We could get rid of
// this, the price would be that the RclEQ.empty() call would have to
// walk the whole queue instead of only looking at the first delays
// entry.
typedef list<queue_type::iterator> delays_type;

// DelayPat stores a path wildcard pattern and a minimum time between
// reindexes, it is read from the recoll configuration
struct DelayPat {
    string pattern;
    int    seconds;
    DelayPat() : seconds(0) {}
};

/** Private part of RclEQ: things that we don't wish to exist in the interface
 *  include file.
 */
class RclEQData {
public:
    int        m_opts{0};
    // Queue for normal files (unlimited reindex)
    queue_type m_iqueue;
    // Queue for delayed reindex files
    queue_type m_dqueue;
    // The delays list stores pointers (iterators) to elements on
    // m_dqueue.  The list is kept in time-to-index order. Elements of
    // m_dqueue which are also in m_delays can only be deleted while
    // walking m_delays, so we are certain that the m_dqueue iterators
    // stored in m_delays remain valid.
    delays_type m_delays;
    // Configured intervals for path patterns, read from the configuration.
    vector<DelayPat> m_delaypats;
    RclConfig *m_config{nullptr};
    bool       m_ok{true};

    std::mutex m_mutex;
    std::condition_variable m_cond;

    void readDelayPats(int dfltsecs);
    DelayPat searchDelayPats(const string& path) {
        for (const auto& dpat: m_delaypats) {
            if (fnmatch(dpat.pattern.c_str(), path.c_str(), 0) == 0) {
                return dpat;
            }
        }
        return DelayPat();
    }
    void delayInsert(const queue_type::iterator &qit);
};

void RclEQData::readDelayPats(int dfltsecs)
{
    if (m_config == 0)
        return;
    string patstring;
    if (!m_config->getConfParam("mondelaypatterns", patstring) || 
        patstring.empty())
        return;

    vector<string> dplist;
    if (!stringToStrings(patstring, dplist)) {
        LOGERR("rclEQData: bad pattern list: [" << patstring << "]\n");
        return;
    }

    for (const auto& entry : dplist) {
        string::size_type pos = entry.find_last_of(":");
        DelayPat dp;
        dp.pattern = entry.substr(0, pos);
        if (pos != string::npos && pos != entry.size() - 1) {
            dp.seconds = atoi(entry.substr(pos+1).c_str());
        } else {
            dp.seconds = dfltsecs;
        }
        m_delaypats.push_back(dp);
        LOGDEB2("rclmon::readDelayPats: add [" << dp.pattern << "] " << dp.seconds << "\n");
    }
}

// Insert event (as queue iterator) into delays list, in time order,
// We DO NOT take care of duplicate qits. erase should be called first
// when necessary.
void RclEQData::delayInsert(const queue_type::iterator &qit)
{
    MONDEB("RclEQData::delayInsert: minclock " << qit->second.m_minclock << "\n");
    for (delays_type::iterator dit = m_delays.begin(); dit != m_delays.end(); dit++) {
        queue_type::iterator qit1 = *dit;
        if ((*qit1).second.m_minclock > qit->second.m_minclock) {
            m_delays.insert(dit, qit);
            return;
        }
    }
    m_delays.push_back(qit);
}

RclMonEventQueue::RclMonEventQueue()
{
    m_data = new RclEQData;
}

RclMonEventQueue::~RclMonEventQueue()
{
    delete m_data;
}

void RclMonEventQueue::setopts(int opts)
{
    if (m_data)
        m_data->m_opts = opts;
}

/** Wait until there is something to process on the queue, or timeout.
 *  returns a queue lock
 */
std::unique_lock<std::mutex> RclMonEventQueue::wait(int seconds, bool *top)
{
    std::unique_lock<std::mutex> lock(m_data->m_mutex);
    
    MONDEB("RclMonEventQueue::wait, seconds: " << seconds << "\n");
    if (!empty()) {
        MONDEB("RclMonEventQueue:: immediate return\n");
        return lock;
    }

    int err;
    if (seconds > 0) {
        if (top)
            *top = false;
        if (m_data->m_cond.wait_for(lock, std::chrono::seconds(seconds)) ==
            std::cv_status::timeout) {
            *top = true;
            MONDEB("RclMonEventQueue:: timeout\n");
            return lock;
        }
    } else {
        m_data->m_cond.wait(lock);
    }
    MONDEB("RclMonEventQueue:: non-timeout return\n");
    return lock;
}

void RclMonEventQueue::setConfig(RclConfig *cnf)
{
    m_data->m_config = cnf;
    // Don't use ixinterval here, could be 0 ! Base the default
    // delayed reindex delay on the default ixinterval delay
    m_data->readDelayPats(10 * dfltixinterval);
}

RclConfig *RclMonEventQueue::getConfig()
{
    return m_data->m_config;
}

bool RclMonEventQueue::ok()
{
    if (m_data == 0) {
        LOGINFO("RclMonEventQueue: not ok: bad state\n" );
        return false;
    }
    if (stopindexing) {
        LOGINFO("RclMonEventQueue: not ok: stop request\n" );
        return false;
    }
    if (!m_data->m_ok) {
        LOGINFO("RclMonEventQueue: not ok: queue terminated\n" );
        return false;
    }
    return true;
}

void RclMonEventQueue::setTerminate()
{
    MONDEB("RclMonEventQueue:: setTerminate\n");
    std::unique_lock<std::mutex> lock(m_data->m_mutex);
    m_data->m_ok = false;
    m_data->m_cond.notify_all();
}

// Must be called with the queue locked
bool RclMonEventQueue::empty()
{
    if (m_data == 0) {
        MONDEB("RclMonEventQueue::empty(): true (m_data==0)\n");
        return true;
    }
    if (!m_data->m_iqueue.empty()) {
        MONDEB("RclMonEventQueue::empty(): false (m_iqueue not empty)\n");
        return true;
    }
    if (m_data->m_dqueue.empty()) {
        MONDEB("RclMonEventQueue::empty(): true (m_Xqueue both empty)\n");
        return true;
    }
    // Only dqueue has events. Have to check the delays (only the
    // first, earliest one):
    queue_type::iterator qit = *(m_data->m_delays.begin());
    if (qit->second.m_minclock > time(0)) {
        MONDEB("RclMonEventQueue::empty(): true (no delay ready " <<
               qit->second.m_minclock << ")\n");
        return true;
    }
    MONDEB("RclMonEventQueue::empty(): returning false (delay expired)\n");
    return false;
}

// Retrieve indexing event for processing. Returns empty event if
// nothing interesting is found
// Must be called with the queue locked
RclMonEvent RclMonEventQueue::pop()
{
    time_t now = time(0);
    MONDEB("RclMonEventQueue::pop(), now " << now << "\n");

    // Look at the delayed events, get rid of the expired/unactive
    // ones, possibly return an expired/needidx one.
    while (!m_data->m_delays.empty()) {
        delays_type::iterator dit = m_data->m_delays.begin();
        queue_type::iterator qit = *dit;
        MONDEB("RclMonEventQueue::pop(): in delays: evt minclock " << 
               qit->second.m_minclock << "\n");
        if (qit->second.m_minclock <= now) {
            if (qit->second.m_needidx) {
                RclMonEvent ev = qit->second;
                qit->second.m_minclock = time(0) + qit->second.m_itvsecs;
                qit->second.m_needidx = false;
                m_data->m_delays.erase(dit);
                m_data->delayInsert(qit);
                return ev;
            } else {
                // Delay elapsed without new update, get rid of event.
                m_data->m_dqueue.erase(qit);
                m_data->m_delays.erase(dit);
            }
        } else {
            // This and following events are for later processing, we
            // are done with the delayed event list.
            break;
        }
    }

    // Look for non-delayed event 
    if (!m_data->m_iqueue.empty()) {
        queue_type::iterator qit = m_data->m_iqueue.begin();
        RclMonEvent ev = qit->second;
        m_data->m_iqueue.erase(qit);
        return ev;
    }

    return RclMonEvent();
}

// Add new event (update or delete) to the processing queue.
// It seems that a newer event is always correct to override any
// older. TBVerified ?
// Some conf-designated files, supposedly updated at a high rate get
// special processing to limit their reindexing rate.
bool RclMonEventQueue::pushEvent(const RclMonEvent &ev)
{
    MONDEB("RclMonEventQueue::pushEvent for " << ev.m_path << "\n");
    std::unique_lock<std::mutex> lock(m_data->m_mutex);

    DelayPat pat = m_data->searchDelayPats(ev.m_path);
    if (pat.seconds != 0) {
        // Using delayed reindex queue. Need to take care of minclock and also
        // insert into the in-minclock-order list
        queue_type::iterator qit = m_data->m_dqueue.find(ev.m_path);
        if (qit == m_data->m_dqueue.end()) {
            // Not there yet, insert new
            qit = m_data->m_dqueue.insert(queue_type::value_type(ev.m_path, ev)).first;
            // Set the time to next index to "now" as it has not been
            // indexed recently (otherwise it would still be in the
            // queue), and add the iterator to the delay queue.
            qit->second.m_minclock = time(0);
            qit->second.m_needidx = true;
            qit->second.m_itvsecs = pat.seconds;
            m_data->delayInsert(qit);
        } else {
            // Already in queue. Possibly update type but save minclock
            // (so no need to touch m_delays). Flag as needing indexing
            time_t saved_clock = qit->second.m_minclock;
            qit->second = ev;
            qit->second.m_minclock = saved_clock;
            qit->second.m_needidx = true;
        }
    } else {
        // Immediate event: just insert it, erasing any previously
        // existing entry
        m_data->m_iqueue[ev.m_path] = ev;
    }

    m_data->m_cond.notify_all();
    return true;
}

static bool checkfileanddelete(const string& fname)
{
    bool ret;
    ret = path_exists(fname);
    unlink(fname.c_str());
    return ret;
}

// It's possible to override the normal indexing delay by creating a
// file in the config directory (which we then remove). And yes there
// is definitely a race condition (we can suppress the delay and file
// before the target doc is queued), and we can't be sure that the
// delay suppression will be used for the doc the user intended it
// for. But this is used for non-critical function and the race
// condition should happen reasonably seldom.
// We check for the request file in all possible user config dirs
// (usually, there is only the main one)
static bool expeditedIndexingRequested(RclConfig *conf)
{
    static vector<string> rqfiles;
    if (rqfiles.empty()) {
        rqfiles.push_back(path_cat(conf->getConfDir(), "rclmonixnow"));
        const char *cp;
        if ((cp = getenv("RECOLL_CONFTOP"))) {
            rqfiles.push_back(path_cat(cp, "rclmonixnow"));
        } 
        if ((cp = getenv("RECOLL_CONFMID"))) {
            rqfiles.push_back(path_cat(cp, "rclmonixnow"));
        } 
    }
    bool found  = false;
    for (vector<string>::const_iterator it = rqfiles.begin(); 
         it != rqfiles.end(); it++) {
        found = found || checkfileanddelete(*it);
    }
    return found;
}

bool startMonitor(RclConfig *conf, int opts)
{
    if (!conf->getConfParam("monauxinterval", &auxinterval))
        auxinterval = dfltauxinterval;
    if (!conf->getConfParam("monixinterval", &ixinterval))
        ixinterval = dfltixinterval;
    bool doweb{false};
    conf->getConfParam("processwebqueue", &doweb);

    rclEQ.setConfig(conf);
    rclEQ.setopts(opts);

    std::thread treceive(rclMonRcvRun, &rclEQ);
    treceive.detach();
    
    LOGDEB("start_monitoring: entering main loop\n" );

    bool timedout;
    time_t lastauxtime = time(0);
    time_t lastixtime = lastauxtime;
    time_t lastmovetime = 0;
    bool didsomething = false;
    list<string> modified;
    list<string> deleted;

    while (true) {
        time_t now = time(0);
#ifndef DISABLE_WEB_INDEXER
        if (doweb && (now - lastmovetime > ixinterval)) {
            lastmovetime = now;
            runWebFilesMoverScript(conf);
        }
#endif // DISABLE_WEB_INDEXER
        
        {
            // Wait for event or timeout.
            // Set a relatively short timeout for better monitoring of
            // exit requests.
            std::unique_lock<std::mutex> lock = rclEQ.wait(2, &timedout);

            // x11IsAlive() can't be called from ok() because both
            // threads call it and Xlib is not multithreaded.
#ifndef _WIN32
            bool x11dead = !(opts & RCLMON_NOX11) && !x11IsAlive();
            if (x11dead)
                LOGDEB("RclMonprc: x11 is dead\n");
#else
            bool x11dead = false;
#endif
            if (!rclEQ.ok() || x11dead) {
                break;
            }
        
            // Process event queue
            for (;;) {
                // Retrieve event
                RclMonEvent ev = rclEQ.pop();
                if (ev.m_path.empty())
                    break;
                switch (ev.evtype()) {
                case RclMonEvent::RCLEVT_MODIFY:
                case RclMonEvent::RCLEVT_DIRCREATE:
                    LOGDEB0("Monitor: Modify/Check on "  << ev.m_path << "\n");
                    modified.push_back(ev.m_path);
                    break;
                case RclMonEvent::RCLEVT_DELETE:
                    LOGDEB0("Monitor: Delete on "  << ev.m_path << "\n");
                    // If this is for a directory (which the caller should tell us because he
                    // knows), we should purge the db of all the subtree entries, because on a
                    // directory rename, inotify will only generate one event for the renamed top,
                    // not the subentries. The entries from the new subtree are updated when the
                    // monitor walks it on the DIRCREATE event.
                    // If the monitor does not have the ISDIR info, we'll just wait for a restart to
                    // do a full run and purge, no big deal.
                    deleted.push_back(ev.m_path);
                    if (ev.evflags() & RclMonEvent::RCLEVT_ISDIR) {
                        vector<string> paths;
                        if (subtreelist(conf, ev.m_path, paths)) {
                            deleted.insert(deleted.end(), paths.begin(), paths.end());
                        }
                    }
                    break;
                default:
                    LOGDEB("Monitor: got Other on [" << ev.m_path << "]\n");
                }
            }
        }

        now = time(0);
        // Process. We don't do this every time but let the lists accumulate
        // a little, this saves processing. Start at once if list is big.
        if (expeditedIndexingRequested(conf) ||
            (now - lastixtime > ixinterval) || 
            (deleted.size() + modified.size() > 20)) {
            lastixtime = now;
            // Used to do the modified list first, but it does seem
            // smarter to make room first...
            if (!deleted.empty()) {
                deleted.sort();
                deleted.unique();
                if (!purgefiles(conf, deleted))
                    break;
                deleted.clear();
                didsomething = true;
            }
            if (!modified.empty()) {
                modified.sort();
                modified.unique();
                if (!indexfiles(conf, modified))
                    break;
                modified.clear();
                didsomething = true;
            }
        }

        // Recreate the auxiliary dbs every hour at most.
        now = time(0);
        if (didsomething && now - lastauxtime > auxinterval) {
            lastauxtime = now;
            didsomething = false;
            if (!createAuxDbs(conf)) {
                // We used to bail out on error here. Not anymore,
                // because this is most of the time due to a failure
                // of aspell dictionary generation, which is not
                // critical.
            }
        }

#ifndef _WIN32
        // Check for a config change
        if (!(opts & RCLMON_NOCONFCHECK) && o_reexec && conf->sourceChanged()) {
            LOGDEB("Rclmonprc: config changed, reexecuting myself\n");
            // We never want to have a -n option after a config
            // change. -n was added by the reexec after the initial
            // pass even if it was not given on the command line
            o_reexec->removeArg("-n");
            o_reexec->reexec();
        }
#endif // ! _WIN32
    }
    LOGDEB("Rclmonprc: calling queue setTerminate\n");
    rclEQ.setTerminate();

    // We used to wait for the receiver thread here before returning,
    // but this is not useful and may waste time / risk problems
    // during our limited time window for exiting. To be reviewed if
    // we ever need several monitor invocations in the same process
    // (can't foresee any reason why we'd want to do this).
    LOGDEB("Monitor: returning\n");
    return true;
}

#endif // RCL_MONITOR