/*
 * Read MaxMind DB files
 *
 * Copyright (C) 2025 Andreas Vögele
 *
 * This module is free software; you can redistribute it and/or modify it
 * under the same terms as Perl itself.
 */

/* SPDX-License-Identifier: Artistic-1.0-Perl OR GPL-1.0-or-later */

#define PERL_NO_GET_CONTEXT
#include "EXTERN.h"
#include "perl.h"
#include "XSUB.h"

#include <maxminddb.h>

#ifdef MULTIPLICITY
#define storeTHX(var) (var) = aTHX
#define dTHXfield(var) tTHX var;
#else
#define storeTHX(var) dNOOP
#define dTHXfield(var)
#endif

#define is_ipv6_database(mmdb) (6 == (mmdb)->metadata.ip_version)

typedef struct ip_geolocation_mmdb {
    MMDB_s mmdb;
    SV *file;
    SV *selfrv;
    dTHXfield(perl)
} *IP__Geolocation__MMDB;

typedef struct {
    IP__Geolocation__MMDB self;
    SV *data_callback;
    SV *node_callback;
    int max_depth;
} iterate_data;

static void
init_iterate_data(iterate_data *data, IP__Geolocation__MMDB self,
                  SV *data_callback, SV *node_callback)
{
    data->self = self;
    data->data_callback = data_callback;
    data->node_callback = node_callback;
    data->max_depth = is_ipv6_database(&self->mmdb) ? 128 : 32;
}

static SV *
to_bigint(IP__Geolocation__MMDB self, const char *bytes, size_t size)
{
    dTHXa(self->perl);

    dSP;
    int count;
    SV *err_tmp;
    SV *retval;

    ENTER;
    SAVETMPS;

    PUSHMARK(SP);
    EXTEND(SP, 2);
    mPUSHs(newRV_inc(self->selfrv));
    mPUSHp(bytes, size);
    PUTBACK;
    count = call_method("_to_bigint", G_SCALAR | G_EVAL);
    SPAGAIN;
    err_tmp = ERRSV;
    if (SvTRUE(err_tmp)) {
        (void) POPs;
        retval = newSVpvn(bytes, size);
    }
    else {
        if (1 == count) {
            retval = newSVsv(POPs);
        }
        else {
            retval = newSVpvn(bytes, size);
        }
    }
    PUTBACK;

    FREETMPS;
    LEAVE;

    return retval;
}

typedef struct {
    char bytes[16];
} numeric_ip;

static void
init_numeric_ip(numeric_ip *ipnum)
{
    Zero(ipnum, sizeof(*ipnum), char);
}

static void
numeric_ip_set_bit(numeric_ip *ipnum, int bit)
{
    int quot = bit / (8 * sizeof(char));
    int rem = bit % (8 * sizeof(char));
    ipnum->bytes[15 - quot] |= (128 >> (7 - rem));
}

static SV *
numeric_ip_to_bigint(IP__Geolocation__MMDB self, const numeric_ip *ipnum)
{
    return to_bigint(self, ipnum->bytes, sizeof(ipnum->bytes));
}

#if MMDB_UINT128_IS_BYTE_ARRAY
static SV *
createSVu128(IP__Geolocation__MMDB self, uint8_t u[16])
{
    char bytes[16];
    size_t n;
    for (n = 0; n < 16; ++n) {
        bytes[n] = (char) u[n];
    }
    return to_bigint(self, bytes, sizeof(bytes));
}
#else
static SV *
createSVu128(IP__Geolocation__MMDB self, mmdb_uint128_t u)
{
#ifdef WORDS_BIGENDIAN
    return to_bigint(self, (const char *) &u, sizeof(u));
#else
    char bytes[sizeof(u)];
    size_t n;
    for (n = 0; n < sizeof(u); ++n) {
        bytes[n] = ((const char *) &u)[sizeof(u) - n - 1];
    }
    return to_bigint(self, bytes, sizeof(bytes));
#endif
}
#endif

#if UVSIZE >= 8
#define createSVu64(self, u) newSVuv(u)
#else
static SV *
createSVu64(IP__Geolocation__MMDB self, uint64_t u)
{
#ifdef WORDS_BIGENDIAN
    return to_bigint(self, (const char *) &u, sizeof(u));
#else
    char bytes[sizeof(u)];
    size_t n;
    for (n = 0; n < sizeof(u); ++n) {
        bytes[n] = ((const char *) &u)[sizeof(u) - n - 1];
    }
    return to_bigint(self, bytes, sizeof(bytes));
#endif
}
#endif

static MMDB_entry_data_list_s *
decode_entry_data_list(IP__Geolocation__MMDB self,
                       MMDB_entry_data_list_s *list, SV **sv, int *mmdb_error)
{
    dTHXa(self->perl);
    MMDB_entry_data_s *data = &list->entry_data;
    switch (data->type) {
    case MMDB_DATA_TYPE_MAP: {
        uint32_t size = data->data_size;
        HV *hv = newHV();
        hv_ksplit(hv, size);
        for (list = list->next; size > 0 && NULL != list; size--) {
            if (MMDB_DATA_TYPE_UTF8_STRING != list->entry_data.type) {
                *mmdb_error = MMDB_INVALID_DATA_ERROR;
                return NULL;
            }
            const char *key = list->entry_data.utf8_string;
            uint32_t key_size = list->entry_data.data_size;
            list = list->next;
            if (NULL == list) {
                *mmdb_error = MMDB_INVALID_DATA_ERROR;
                return NULL;
            }
            SV *val = &PL_sv_undef;
            list = decode_entry_data_list(self, list, &val, mmdb_error);
            if (MMDB_SUCCESS != *mmdb_error) {
                return NULL;
            }
            (void) hv_store(hv, key, key_size, val, 0);
        }
        *sv = newRV_noinc((SV *) hv);
        }
        break;

    case MMDB_DATA_TYPE_ARRAY: {
        uint32_t size = data->data_size;
        AV *av = newAV();
        av_extend(av, size);
        for (list = list->next; size > 0 && NULL != list; size--) {
            SV *val = &PL_sv_undef;
            list = decode_entry_data_list(self, list, &val, mmdb_error);
            if (MMDB_SUCCESS != *mmdb_error) {
                return NULL;
            }
            av_push(av, val);
        }
        *sv = newRV_noinc((SV *) av);
        }
        break;

    case MMDB_DATA_TYPE_UTF8_STRING:
        *sv = newSVpvn_utf8(data->utf8_string, data->data_size, 1);
        list = list->next;
        break;

    case MMDB_DATA_TYPE_BYTES:
        *sv = newSVpvn((const char *) data->bytes, data->data_size);
        list = list->next;
        break;

    case MMDB_DATA_TYPE_DOUBLE:
        *sv = newSVnv(data->double_value);
        list = list->next;
        break;

    case MMDB_DATA_TYPE_FLOAT:
        *sv = newSVnv(data->float_value);
        list = list->next;
        break;

    case MMDB_DATA_TYPE_UINT16:
        *sv = newSVuv(data->uint16);
        list = list->next;
        break;

    case MMDB_DATA_TYPE_UINT32:
        *sv = newSVuv(data->uint32);
        list = list->next;
        break;

    case MMDB_DATA_TYPE_BOOLEAN:
        *sv = newSViv(data->boolean);
        list = list->next;
        break;

    case MMDB_DATA_TYPE_UINT64:
        *sv = createSVu64(self, data->uint64);
        list = list->next;
        break;

    case MMDB_DATA_TYPE_UINT128:
        *sv = createSVu128(self, data->uint128);
        list = list->next;
        break;

    case MMDB_DATA_TYPE_INT32:
        *sv = newSViv(data->int32);
        list = list->next;
        break;

    default:
        *mmdb_error = MMDB_INVALID_DATA_ERROR;
        return NULL;
    }

    *mmdb_error = MMDB_SUCCESS;
    return list;
}

static void
call_node_callback(iterate_data *data, uint32_t node_num,
                   MMDB_search_node_s *node)
{
    IP__Geolocation__MMDB self = data->self;
    dTHXa(self->perl);

    if (!SvOK(data->node_callback)) {
        return;
    }

    dSP;
    SV *left_record = createSVu64(self, node->left_record);
    SV *right_record = createSVu64(self, node->right_record);

    ENTER;
    SAVETMPS;

    PUSHMARK(SP);
    EXTEND(SP, 3);
    mPUSHu(node_num);
    mPUSHs(left_record);
    mPUSHs(right_record);
    PUTBACK;
    (void) call_sv(data->node_callback, G_VOID);

    FREETMPS;
    LEAVE;
}

static void
call_data_callback(iterate_data *data, numeric_ip ipnum, int depth,
                   MMDB_entry_s *record_entry)
{
    IP__Geolocation__MMDB self = data->self;
    dTHXa(self->perl);

    if (!SvOK(data->data_callback)) {
      return;
    }

    SV *decoded_entry = &PL_sv_undef;
    MMDB_entry_data_list_s *list = NULL;
    int mmdb_error = MMDB_get_entry_data_list(record_entry, &list);
    if (MMDB_SUCCESS == mmdb_error) {
        (void) decode_entry_data_list(self, list, &decoded_entry,
                                      &mmdb_error);
    }
    MMDB_free_entry_data_list(list);
    if (MMDB_SUCCESS != mmdb_error) {
        const char *error = MMDB_strerror(mmdb_error);
        croak("Entry data error looking at offset %u: %s",
              (unsigned int) record_entry->offset, error);
    }

    SV *ip = numeric_ip_to_bigint(self, &ipnum);

    dSP;

    ENTER;
    SAVETMPS;

    PUSHMARK(SP);
    EXTEND(SP, 3);
    mPUSHs(ip);
    mPUSHi(depth);
    mPUSHs(decoded_entry);
    PUTBACK;

    (void) call_sv(data->data_callback, G_VOID);

    FREETMPS;
    LEAVE;
}

static void iterate_search_nodes(iterate_data *, uint32_t, numeric_ip, int);

static void
iterate_record_entry(iterate_data *data, numeric_ip ipnum, int depth,
                     uint64_t record, uint8_t record_type,
                     MMDB_entry_s *record_entry)
{
    switch (record_type) {
    case MMDB_RECORD_TYPE_INVALID:
        croak("%s", "Invalid record when reading node");
        break;
    case MMDB_RECORD_TYPE_SEARCH_NODE:
        iterate_search_nodes(data, (uint32_t) record, ipnum, depth + 1);
        break;
    case MMDB_RECORD_TYPE_EMPTY:
        /* Empty branches are ignored. */
        break;
    case MMDB_RECORD_TYPE_DATA:
        call_data_callback(data, ipnum, depth, record_entry);
        break;
    default:
        croak("Unknown record type: %u", (unsigned int) record_type);
        break;
    }
}

static void
iterate_search_nodes(iterate_data *data, uint32_t node_num, numeric_ip ipnum,
                     int depth)
{
    MMDB_search_node_s node;
    int mmdb_error = MMDB_read_node(&data->self->mmdb, node_num, &node);
    if (MMDB_SUCCESS != mmdb_error) {
        const char *error = MMDB_strerror(mmdb_error);
        croak("Error reading node %u: %s", (unsigned int) node_num, error);
    }

    if (depth > data->max_depth) {
        croak("Invalid depth when reading node %u: %d", (unsigned int)
              node_num, depth);
    }

    call_node_callback(data, node_num, &node);

    iterate_record_entry(data, ipnum, depth, node.left_record,
                         node.left_record_type, &node.left_record_entry);

    numeric_ip_set_bit(&ipnum, data->max_depth - depth);

    iterate_record_entry(data, ipnum, depth, node.right_record,
                         node.right_record_type, &node.right_record_entry);
}

MODULE = IP::Geolocation::MMDB PACKAGE = IP::Geolocation::MMDB

PROTOTYPES: DISABLE

SV *
new(klass, ...)
    SV *klass
  INIT:
    IP__Geolocation__MMDB self;
    SV *file = NULL;
    U32 flags = 0;
    I32 i;
    const char *key;
    SV *value;
    const char *filename;
    int mmdb_error;
    const char *error;
  CODE:
    if ((items - 1) % 2 != 0) {
        warn("Odd-length list passed to %" SVf " constructor", SVfARG(klass));
    }

    for (i = 1; i < items; i += 2) {
        key = SvPV_nolen_const(ST(i));
        value = ST(i + 1);
        if (strEQ(key, "file")) {
            file = value;
        }
    }

    if (NULL == file) {
        croak("The \"file\" parameter is mandatory");
    }

    filename = SvPVbyte_nolen(file);

    Newxz(self, 1, struct ip_geolocation_mmdb);
    storeTHX(self->perl);
    self->file = SvREFCNT_inc(file);

    mmdb_error = MMDB_open(filename, flags, &self->mmdb);
    if (MMDB_SUCCESS != mmdb_error) {
        Safefree(self);
        error = MMDB_strerror(mmdb_error);
        croak("Error opening database file \"%" SVf "\": %s", SVfARG(file),
              error);
    }

    RETVAL = sv_bless(newRV_noinc(newSViv(PTR2IV(self))),
                      gv_stashsv(klass, GV_ADD));
    self->selfrv = SvRV(RETVAL); /* no inc */
  OUTPUT:
    RETVAL

void
DESTROY(self)
    IP::Geolocation::MMDB self
  CODE:
    MMDB_close(&self->mmdb);
    SvREFCNT_dec(self->file);
    Safefree(self);

void
get(self, ...)
    IP::Geolocation::MMDB self
  ALIAS:
    record_for_address = 1
  INIT:
    const char *ip_address;
    int gai_error, mmdb_error;
    const char *error;
    MMDB_lookup_result_s result;
    MMDB_entry_data_list_s *list;
    SV *data = &PL_sv_undef;
    int wants_prefix_length = 0;
    uint16_t prefix_length = 0;
    U8 gimme = GIMME_V;
  PPCODE:
    ip_address = NULL;
    if (items > 1) {
        ip_address = SvPVbyte_nolen(ST(1));
    }
    if (NULL == ip_address || '\0' == *ip_address) {
        croak("%s", "You must provide an IP address to look up");
    }
    result =
        MMDB_lookup_string(&self->mmdb, ip_address, &gai_error, &mmdb_error);
    if (0 != gai_error) {
        croak("The IP address you provided (%s) is not a valid IPv4 or IPv6 "
              "address", ip_address);
    }
    if (MMDB_SUCCESS != mmdb_error) {
        error = MMDB_strerror(mmdb_error);
        croak("Error looking up IP address \"%s\": %s", ip_address, error);
    }
    if (result.found_entry) {
        list = NULL;
        mmdb_error = MMDB_get_entry_data_list(&result.entry, &list);
        if (MMDB_SUCCESS == mmdb_error) {
            (void) decode_entry_data_list(self, list, &data, &mmdb_error);
        }
        MMDB_free_entry_data_list(list);
        if (MMDB_SUCCESS != mmdb_error) {
            error = MMDB_strerror(mmdb_error);
            croak("Entry data error looking up \"%s\": %s", ip_address,
                  error);
        }
        if (0 == ix && G_SCALAR != gimme) {
            wants_prefix_length = 1;
            if (instr(ip_address, ".") && is_ipv6_database(&self->mmdb)) {
                prefix_length = result.netmask - 96;
            }
            else {
                prefix_length = result.netmask;
            }
        }
    }
    XPUSHs(sv_2mortal(data));
    if (wants_prefix_length) {
        XPUSHs(sv_2mortal(newSVuv(prefix_length)));
    }

void
iterate_search_tree(self, ...)
    IP::Geolocation::MMDB self
  INIT:
    SV *data_callback;
    SV *node_callback;
    iterate_data data;
    numeric_ip ipnum;
  CODE:
    data_callback = &PL_sv_undef;
    node_callback = &PL_sv_undef;
    if (items > 1) {
        data_callback = ST(1);
        if (items > 2) {
            node_callback = ST(2);
        }
    }
    init_iterate_data(&data, self, data_callback, node_callback);
    init_numeric_ip(&ipnum);
    iterate_search_nodes(&data, 0, ipnum, 1);

SV *
_metadata(self)
    IP::Geolocation::MMDB self
  INIT:
    int mmdb_error;
    const char *error;
    MMDB_entry_data_list_s *list;
  CODE:
    RETVAL = &PL_sv_undef;
    list = NULL;
    mmdb_error = MMDB_get_metadata_as_entry_data_list(&self->mmdb, &list);
    if (MMDB_SUCCESS == mmdb_error) {
        (void) decode_entry_data_list(self, list, &RETVAL, &mmdb_error);
    }
    MMDB_free_entry_data_list(list);
    if (MMDB_SUCCESS != mmdb_error) {
        error = MMDB_strerror(mmdb_error);
        croak("Error getting metadata: %s", error);
    }
  OUTPUT:
    RETVAL

SV *
file(self)
    IP::Geolocation::MMDB self
  CODE:
    RETVAL = SvREFCNT_inc(self->file);
  OUTPUT:
    RETVAL

const char *
libmaxminddb_version()
  CODE:
    RETVAL = MMDB_lib_version();
  OUTPUT:
    RETVAL