// This file Copyright © 2007-2022 Mnemosyne LLC.
// It may be used under GPLv2 (SPDX: GPL-2.0-only), GPLv3 (SPDX: GPL-3.0-only),
// or any future license endorsed by Mnemosyne LLC.
// License text can be found in the licenses/ folder.

#include <ctime>
#include <string>

#include "transmission.h"

#include "log.h"
#include "session.h"
#include "stats.h"
#include "tr-strbuf.h"
#include "utils.h"
#include "variant.h"

using namespace std::literals;

/***
****
***/

/** @brief Opaque, per-session data structure for bandwidth use statistics */
struct tr_stats_handle
{
    tr_session_stats single;
    tr_session_stats old;
    time_t startTime;
    bool isDirty;
};

static void loadCumulativeStats(tr_session const* session, tr_session_stats* setme)
{
    auto top = tr_variant{};

    auto filename = tr_pathbuf{ session->config_dir, "/stats.json"sv };
    bool loaded = tr_variantFromFile(&top, TR_VARIANT_PARSE_JSON, filename.sv(), nullptr);

    if (!loaded)
    {
        // maybe the user just upgraded from an old version of Transmission
        // that was still using stats.benc
        filename.assign(session->config_dir, "/stats.benc");
        loaded = tr_variantFromFile(&top, TR_VARIANT_PARSE_BENC, filename.sv(), nullptr);
    }

    if (loaded)
    {
        auto i = int64_t{};

        if (tr_variantDictFindInt(&top, TR_KEY_downloaded_bytes, &i))
        {
            setme->downloadedBytes = (uint64_t)i;
        }

        if (tr_variantDictFindInt(&top, TR_KEY_files_added, &i))
        {
            setme->filesAdded = (uint64_t)i;
        }

        if (tr_variantDictFindInt(&top, TR_KEY_seconds_active, &i))
        {
            setme->secondsActive = (uint64_t)i;
        }

        if (tr_variantDictFindInt(&top, TR_KEY_session_count, &i))
        {
            setme->sessionCount = (uint64_t)i;
        }

        if (tr_variantDictFindInt(&top, TR_KEY_uploaded_bytes, &i))
        {
            setme->uploadedBytes = (uint64_t)i;
        }

        tr_variantFree(&top);
    }
}

static void saveCumulativeStats(tr_session const* session, tr_session_stats const* s)
{
    auto const filename = tr_pathbuf{ session->config_dir, "/stats.json"sv };
    auto top = tr_variant{};
    tr_variantInitDict(&top, 5);
    tr_variantDictAddInt(&top, TR_KEY_downloaded_bytes, s->downloadedBytes);
    tr_variantDictAddInt(&top, TR_KEY_files_added, s->filesAdded);
    tr_variantDictAddInt(&top, TR_KEY_seconds_active, s->secondsActive);
    tr_variantDictAddInt(&top, TR_KEY_session_count, s->sessionCount);
    tr_variantDictAddInt(&top, TR_KEY_uploaded_bytes, s->uploadedBytes);
    tr_variantToFile(&top, TR_VARIANT_FMT_JSON, filename.sv());
    tr_variantFree(&top);
}

/***
****
***/

void tr_statsInit(tr_session* session)
{
    auto* const stats = tr_new0(struct tr_stats_handle, 1);

    loadCumulativeStats(session, &stats->old);
    stats->single.sessionCount = 1;
    stats->startTime = tr_time();
    session->sessionStats = stats;
}

static tr_stats_handle* getStats(tr_session const* session)
{
    return session != nullptr ? session->sessionStats : nullptr;
}

void tr_statsSaveDirty(tr_session* session)
{
    auto* const h = getStats(session);

    if (h != nullptr && h->isDirty)
    {
        auto cumulative = tr_session_stats{};
        tr_sessionGetCumulativeStats(session, &cumulative);
        saveCumulativeStats(session, &cumulative);
        h->isDirty = false;
    }
}

void tr_statsClose(tr_session* session)
{
    tr_statsSaveDirty(session);

    tr_free(session->sessionStats);
    session->sessionStats = nullptr;
}

/***
****
***/

static void updateRatio(tr_session_stats* setme)
{
    setme->ratio = tr_getRatio(setme->uploadedBytes, setme->downloadedBytes);
}

static void addStats(tr_session_stats* setme, tr_session_stats const* a, tr_session_stats const* b)
{
    setme->uploadedBytes = a->uploadedBytes + b->uploadedBytes;
    setme->downloadedBytes = a->downloadedBytes + b->downloadedBytes;
    setme->filesAdded = a->filesAdded + b->filesAdded;
    setme->sessionCount = a->sessionCount + b->sessionCount;
    setme->secondsActive = a->secondsActive + b->secondsActive;
    updateRatio(setme);
}

void tr_sessionGetStats(tr_session const* session, tr_session_stats* setme)
{
    struct tr_stats_handle const* stats = getStats(session);

    if (stats != nullptr)
    {
        *setme = stats->single;
        setme->secondsActive = tr_time() - stats->startTime;
        updateRatio(setme);
    }
}

void tr_sessionGetCumulativeStats(tr_session const* session, tr_session_stats* setme)
{
    struct tr_stats_handle const* stats = getStats(session);
    auto current = tr_session_stats{};

    if (stats != nullptr)
    {
        tr_sessionGetStats(session, &current);
        addStats(setme, &stats->old, &current);
    }
}

void tr_sessionClearStats(tr_session* session)
{
    tr_session_stats zero;

    zero.uploadedBytes = 0;
    zero.downloadedBytes = 0;
    zero.ratio = TR_RATIO_NA;
    zero.filesAdded = 0;
    zero.sessionCount = 0;
    zero.secondsActive = 0;

    session->sessionStats->isDirty = true;
    session->sessionStats->single = session->sessionStats->old = zero;
    session->sessionStats->startTime = tr_time();
}

/**
***
**/

void tr_statsAddUploaded(tr_session* session, uint32_t bytes)
{
    auto* const s = getStats(session);

    if (s != nullptr)
    {
        s->single.uploadedBytes += bytes;
        s->isDirty = true;
    }
}

void tr_statsAddDownloaded(tr_session* session, uint32_t bytes)
{
    auto* const s = getStats(session);

    if (s != nullptr)
    {
        s->single.downloadedBytes += bytes;
        s->isDirty = true;
    }
}

void tr_statsFileCreated(tr_session* session)
{
    auto* const s = getStats(session);

    if (s != nullptr)
    {
        s->single.filesAdded++;
    }
}