/*
 * This file Copyright (C) Mnemosyne LLC
 *
 * This file is licensed by the GPL version 2. Works owned by the
 * Transmission project are granted a special exemption to clause 2 (b)
 * so that the bulk of its code can remain under the MIT license.
 * This exemption does not extend to derived works not owned by
 * the Transmission project.
 *
 * $Id$
 */

#include <assert.h>
#include <errno.h>
#include <stdio.h>
#include <stdlib.h> /* bsearch (), qsort () */
#include <string.h>

#include <unistd.h> /* unlink () */

#ifdef WIN32
 #include <w32api.h>
 #define WINVER  WindowsXP
 #include <windows.h>
 #define PROT_READ      PAGE_READONLY
 #define MAP_PRIVATE    FILE_MAP_COPY
#endif

#ifndef WIN32
 #include <sys/mman.h>
#endif
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>

#include "transmission.h"
#include "blocklist.h"
#include "net.h"
#include "utils.h"

#ifndef O_BINARY
 #define O_BINARY 0
#endif


/***
****  PRIVATE
***/

struct tr_ipv4_range
{
    uint32_t    begin;
    uint32_t    end;
};

struct tr_blocklist
{
    bool                   isEnabled;
    int                    fd;
    size_t                 ruleCount;
    size_t                 byteCount;
    char *                 filename;
    struct tr_ipv4_range * rules;
};

static void
blocklistClose (tr_blocklist * b)
{
    if (b->rules)
    {
        munmap (b->rules, b->byteCount);
        close (b->fd);
        b->rules = NULL;
        b->ruleCount = 0;
        b->byteCount = 0;
        b->fd = -1;
    }
}

static void
blocklistLoad (tr_blocklist * b)
{
    int fd;
    size_t byteCount;
    struct stat st;
    const char * err_fmt = _("Couldn't read \"%1$s\": %2$s");

    blocklistClose (b);

    if (stat (b->filename, &st) == -1)
        return;

    fd = open (b->filename, O_RDONLY | O_BINARY);
    if (fd == -1)
    {
        tr_err (err_fmt, b->filename, tr_strerror (errno));
        return;
    }

    byteCount = (size_t) st.st_size;
    b->rules = mmap (NULL, byteCount, PROT_READ, MAP_PRIVATE, fd, 0);
    if (!b->rules)
    {
        tr_err (err_fmt, b->filename, tr_strerror (errno));
        close (fd);
        return;
    }

    b->fd = fd;
    b->byteCount = byteCount;
    b->ruleCount = byteCount / sizeof (struct tr_ipv4_range);

    {
        char * base = tr_basename (b->filename);
        tr_inf (_("Blocklist \"%s\" contains %zu entries"), base, b->ruleCount);
        tr_free (base);
    }
}

static void
blocklistEnsureLoaded (tr_blocklist * b)
{
    if (!b->rules)
        blocklistLoad (b);
}

static int
compareAddressToRange (const void * va,
                       const void * vb)
{
    const uint32_t *             a = va;
    const struct tr_ipv4_range * b = vb;

    if (*a < b->begin) return -1;
    if (*a > b->end) return 1;
    return 0;
}

static void
blocklistDelete (tr_blocklist * b)
{
    blocklistClose (b);
    unlink (b->filename);
}

/***
****  PACKAGE-VISIBLE
***/

tr_blocklist *
_tr_blocklistNew (const char * filename, bool isEnabled)
{
    tr_blocklist * b;

    b = tr_new0 (tr_blocklist, 1);
    b->fd = -1;
    b->filename = tr_strdup (filename);
    b->isEnabled = isEnabled;

    return b;
}

const char*
_tr_blocklistGetFilename (const tr_blocklist * b)
{
    return b->filename;
}

void
_tr_blocklistFree (tr_blocklist * b)
{
    blocklistClose (b);
    tr_free (b->filename);
    tr_free (b);
}

int
_tr_blocklistExists (const tr_blocklist * b)
{
    struct stat st;

    return !stat (b->filename, &st);
}

int
_tr_blocklistGetRuleCount (const tr_blocklist * b)
{
    blocklistEnsureLoaded ((tr_blocklist*)b);

    return b->ruleCount;
}

int
_tr_blocklistIsEnabled (tr_blocklist * b)
{
    return b->isEnabled;
}

void
_tr_blocklistSetEnabled (tr_blocklist * b, bool isEnabled)
{
    b->isEnabled = isEnabled ? 1 : 0;
}

int
_tr_blocklistHasAddress (tr_blocklist * b, const tr_address * addr)
{
    uint32_t                     needle;
    const struct tr_ipv4_range * range;

    assert (tr_address_is_valid (addr));

    if (!b->isEnabled || addr->type == TR_AF_INET6)
        return 0;

    blocklistEnsureLoaded (b);

    if (!b->rules || !b->ruleCount)
        return 0;

    needle = ntohl (addr->addr.addr4.s_addr);

    range = bsearch (&needle,
                     b->rules,
                     b->ruleCount,
                     sizeof (struct tr_ipv4_range),
                     compareAddressToRange);

    return range != NULL;
}

/*
 * P2P plaintext format: "comment:x.x.x.x-y.y.y.y"
 * http://wiki.phoenixlabs.org/wiki/P2P_Format
 * http://en.wikipedia.org/wiki/PeerGuardian#P2P_plaintext_format
 */
static bool
parseLine1 (const char * line, struct tr_ipv4_range * range)
{
    char * walk;
    int b[4];
    int e[4];
    char str[64];
    tr_address addr;

    walk = strrchr (line, ':');
    if (!walk)
        return false;
    ++walk; /* walk past the colon */

    if (sscanf (walk, "%d.%d.%d.%d-%d.%d.%d.%d",
                &b[0], &b[1], &b[2], &b[3],
                &e[0], &e[1], &e[2], &e[3]) != 8)
        return false;

    tr_snprintf (str, sizeof (str), "%d.%d.%d.%d", b[0], b[1], b[2], b[3]);
    if (!tr_address_from_string (&addr, str))
        return false;
    range->begin = ntohl (addr.addr.addr4.s_addr);

    tr_snprintf (str, sizeof (str), "%d.%d.%d.%d", e[0], e[1], e[2], e[3]);
    if (!tr_address_from_string (&addr, str))
        return false;
    range->end = ntohl (addr.addr.addr4.s_addr);

    return true;
}

/*
 * DAT format: "000.000.000.000 - 000.255.255.255 , 000 , invalid ip"
 * http://wiki.phoenixlabs.org/wiki/DAT_Format
 */
static bool
parseLine2 (const char * line, struct tr_ipv4_range * range)
{
    int unk;
    int a[4];
    int b[4];
    char str[32];
    tr_address addr;

    if (sscanf (line, "%3d.%3d.%3d.%3d - %3d.%3d.%3d.%3d , %3d , ",
                &a[0], &a[1], &a[2], &a[3],
                &b[0], &b[1], &b[2], &b[3],
                &unk) != 9)
        return false;

    tr_snprintf (str, sizeof (str), "%d.%d.%d.%d", a[0], a[1], a[2], a[3]);
    if (!tr_address_from_string (&addr, str))
        return false;
    range->begin = ntohl (addr.addr.addr4.s_addr);

    tr_snprintf (str, sizeof (str), "%d.%d.%d.%d", b[0], b[1], b[2], b[3]);
    if (!tr_address_from_string (&addr, str))
        return false;
    range->end = ntohl (addr.addr.addr4.s_addr);

    return true;
}

static int
parseLine (const char * line, struct tr_ipv4_range * range)
{
    return parseLine1 (line, range)
        || parseLine2 (line, range);
}

static int
compareAddressRangesByFirstAddress (const void * va, const void * vb)
{
    const struct tr_ipv4_range * a = va;
    const struct tr_ipv4_range * b = vb;
    if (a->begin != b->begin)
        return a->begin < b->begin ? -1 : 1;
    return 0;
}

int
_tr_blocklistSetContent (tr_blocklist * b, const char * filename)
{
    FILE * in;
    FILE * out;
    int inCount = 0;
    char line[2048];
    const char * err_fmt = _("Couldn't read \"%1$s\": %2$s");
    struct tr_ipv4_range * ranges = NULL;
    size_t ranges_alloc = 0;
    size_t ranges_count = 0;

    if (!filename)
    {
        blocklistDelete (b);
        return 0;
    }

    in = fopen (filename, "rb");
    if (!in)
    {
        tr_err (err_fmt, filename, tr_strerror (errno));
        return 0;
    }

    blocklistClose (b);

    out = fopen (b->filename, "wb+");
    if (!out)
    {
        tr_err (err_fmt, b->filename, tr_strerror (errno));
        fclose (in);
        return 0;
    }

    /* load the rules into memory */
    while (fgets (line, sizeof (line), in) != NULL)
    {
        char * walk;
        struct tr_ipv4_range range;

        ++inCount;

        /* zap the linefeed */
        if ((walk = strchr (line, '\r'))) *walk = '\0';
        if ((walk = strchr (line, '\n'))) *walk = '\0';

        if (!parseLine (line, &range))
        {
            /* don't try to display the actual lines - it causes issues */
            tr_err (_("blocklist skipped invalid address at line %d"), inCount);
            continue;
        }

        if (ranges_alloc == ranges_count)
        {
            ranges_alloc += 4096; /* arbitrary */
            ranges = tr_renew (struct tr_ipv4_range, ranges, ranges_alloc);
        }

        ranges[ranges_count++] = range;
    }

    if (ranges_count > 0) /* sort and merge */
    {
        struct tr_ipv4_range * r;
        struct tr_ipv4_range * keep = ranges;
        const struct tr_ipv4_range * end;

        /* sort */
        qsort (ranges, ranges_count, sizeof (struct tr_ipv4_range),
               compareAddressRangesByFirstAddress);

        /* merge */
        for (r=ranges+1, end=ranges+ranges_count; r!=end; ++r) {
            if (keep->end < r->begin)
                *++keep = *r;
            else if (keep->end < r->end)
                keep->end = r->end;
        }

        ranges_count = keep + 1 - ranges;

#ifndef NDEBUG
        /* sanity checks: make sure the rules are sorted
         * in ascending order and don't overlap */
        {
            size_t i;

            for (i=0; i<ranges_count; ++i)
                assert (ranges[i].begin <= ranges[i].end);

            for (i=1; i<ranges_count; ++i)
                assert (ranges[i-1].end < ranges[i].begin);
        }
#endif
    }

    if (fwrite (ranges, sizeof (struct tr_ipv4_range), ranges_count, out) != ranges_count)
        tr_err (_("Couldn't save file \"%1$s\": %2$s"), b->filename, tr_strerror (errno));
    else {
        char * base = tr_basename (b->filename);
        tr_inf (_("Blocklist \"%s\" updated with %zu entries"), base, ranges_count);
        tr_free (base);
    }

    tr_free (ranges);
    fclose (out);
    fclose (in);

    blocklistLoad (b);

    return ranges_count;
}