/* -*- Mode: C++; tab-width: 4; c-basic-offset: 4; indent-tabs-mode: nil -*- */
/*
 *   Copyright 2024-Present Couchbase, Inc.
 *
 *   Licensed under the Apache License, Version 2.0 (the "License");
 *   you may not use this file except in compliance with the License.
 *   You may obtain a copy of the License at
 *
 *       http://www.apache.org/licenses/LICENSE-2.0
 *
 *   Unless required by applicable law or agreed to in writing, software
 *   distributed under the License is distributed on an "AS IS" BASIS,
 *   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *   See the License for the specific language governing permissions and
 *   limitations under the License.
 */

#include "key_generator.hxx"

#include "core/topology/configuration.hxx"

#include <optional>
#include <spdlog/fmt/bundled/core.h>

#include <gsl/assert>
#include <gsl/span>

#include <array>
#include <random>
#include <stdexcept>

namespace cbc
{
namespace
{
constexpr std::array<std::uint32_t, 256> crc32_table_array = {
  0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419, 0x706af48f, 0xe963a535, 0x9e6495a3,
  0x0edb8832, 0x79dcb8a4, 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07, 0x90bf1d91,
  0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de, 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7,
  0x136c9856, 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9, 0xfa0f3d63, 0x8d080df5,
  0x3b6e20c8, 0x4c69105e, 0xd56041e4, 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
  0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3, 0x45df5c75, 0xdcd60dcf, 0xabd13d59,
  0x26d930ac, 0x51de003a, 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599, 0xb8bda50f,
  0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924, 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d,
  0x76dc4190, 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f, 0x9fbfe4a5, 0xe8b8d433,
  0x7807c9a2, 0x0f00f934, 0x9609a88e, 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
  0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed, 0x1b01a57b, 0x8208f4c1, 0xf50fc457,
  0x65b0d9c6, 0x12b7e950, 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3, 0xfbd44c65,
  0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2, 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb,
  0x4369e96a, 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5, 0xaa0a4c5f, 0xdd0d7cc9,
  0x5005713c, 0x270241aa, 0xbe0b1010, 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
  0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17, 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad,
  0xedb88320, 0x9abfb3b6, 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615, 0x73dc1683,
  0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8, 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1,
  0xf00f9344, 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb, 0x196c3671, 0x6e6b06e7,
  0xfed41b76, 0x89d32be0, 0x10da7a5a, 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
  0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1, 0xa6bc5767, 0x3fb506dd, 0x48b2364b,
  0xd80d2bda, 0xaf0a1b4c, 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef, 0x4669be79,
  0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236, 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f,
  0xc5ba3bbe, 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31, 0x2cd99e8b, 0x5bdeae1d,
  0x9b64c2b0, 0xec63f226, 0x756aa39c, 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
  0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b, 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21,
  0x86d3d2d4, 0xf1d4e242, 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1, 0x18b74777,
  0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c, 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45,
  0xa00ae278, 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7, 0x4969474d, 0x3e6e77db,
  0xaed16a4a, 0xd9d65adc, 0x40df0b66, 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
  0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605, 0xcdd70693, 0x54de5729, 0x23d967bf,
  0xb3667a2e, 0xc4614ab8, 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b, 0x2d02ef8d,
};

constexpr gsl::span crc32_table{ crc32_table_array };

auto
hash_crc32(const std::string& data) -> std::uint32_t
{
  std::uint32_t crc = std::numeric_limits<std::uint32_t>::max();

  for (const auto x : data) {
    crc = (crc >> 8) ^ crc32_table[(crc ^ static_cast<std::uint32_t>(x)) & 0xff];
  }
  return ((~crc) >> 16) & 0x7fff;
}

auto
map_key_to_vbucket_id(const std::string& key, std::size_t number_of_vbuckets) -> std::uint16_t
{
  auto digest = hash_crc32(key);
  return static_cast<std::uint16_t>(digest % number_of_vbuckets);
}

constexpr std::array default_alphabet = {
  '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'A', 'B', 'C', 'D', 'E', 'F',
  'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V',
  'W', 'X', 'Y', 'Z', 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l',
  'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z',
};

void
update_state(gsl::span<char> alphabet, std::string& state, bool can_grow)
{
  for (char& symbol : state) {
    const auto it = std::find(alphabet.begin(), alphabet.end(), symbol);
    if (it == alphabet.end() - 1) {
      symbol = alphabet.front();
    } else {
      symbol = *(it + 1);
      return;
    }
  }

  if (can_grow) {
    state.push_back(alphabet.front());
  } else {
    // shift state to the right and overwrite first symbol
    std::rotate(state.rbegin(), state.rbegin() + 1, state.rend());
    state[0] = alphabet.front();
  }
}

} // namespace

key_generator::key_generator(const key_generator_options& options)
  : prefix_{ options.prefix }
  , number_of_vbuckets_{ options.number_of_vbuckets }
  , alphabet_{ default_alphabet.begin(), default_alphabet.end() }
  , fixed_length_{ options.fixed_length }
{
  if (!prefix_.empty() && fixed_length_ <= prefix_.length()) {
    throw std::invalid_argument("prefix length must be less than fixed length");
  }

  if (fixed_length_ > 0) {
    state_.resize(fixed_length_ - prefix_.size(), default_alphabet[0]);
  }

  if (options.randomize) {
    std::random_device rnd_dev;
    std::default_random_engine rnd(rnd_dev());
    std::shuffle(alphabet_.begin(), alphabet_.end(), rnd);
  }
}

auto
key_generator::next_key() -> std::string
{
  update_state(alphabet_, state_, fixed_length_ == 0);
  return fmt::format("{}{}", prefix_, state_);
}

auto
key_generator::next_keys(std::size_t count, bool skip_duplicates) -> std::vector<std::string>
{
  if (skip_duplicates) {
    std::set<std::string> result;
    while (result.size() < count) {
      result.insert(next_key());
    }
    return { result.begin(), result.end() };
  }

  std::vector<std::string> result;
  result.reserve(count);
  for (std::size_t i = 0; i < count; ++i) {
    result.push_back(next_key());
  }
  return result;
}

auto
key_generator::next_key_for_vbucket(std::uint16_t vbucket) -> std::string
{
  std::string result;
  do {
    result = next_key();
  } while (map_key_to_vbucket_id(result, number_of_vbuckets_) != vbucket);
  return result;
}

auto
key_generator::next_keys_for_vbucket(std::size_t count, std::uint16_t vbucket, bool skip_duplicates)
  -> std::vector<std::string>
{
  if (skip_duplicates) {
    std::set<std::string> result;
    while (result.size() < count) {
      result.insert(next_key_for_vbucket(vbucket));
    }
    return { result.begin(), result.end() };
  }

  std::vector<std::string> result;
  result.reserve(count);
  for (std::size_t i = 0; i < count; ++i) {
    result.push_back(next_key_for_vbucket(vbucket));
  }
  return result;
}

auto
key_generator::next_key_for_vbucket_set(const std::set<std::uint16_t>& vbuckets) -> std::string
{
  std::string result;
  do {
    result = next_key();
  } while (vbuckets.find(map_key_to_vbucket_id(result, number_of_vbuckets_)) == vbuckets.end());
  return result;
}

auto
key_generator::next_keys_for_vbucket_set(std::size_t count,
                                         const std::set<std::uint16_t>& vbuckets,
                                         bool skip_duplicates) -> std::vector<std::string>
{
  if (skip_duplicates) {
    std::set<std::string> result;
    while (result.size() < count) {
      result.insert(next_key_for_vbucket_set(vbuckets));
    }
    return { result.begin(), result.end() };
  }

  std::vector<std::string> result;
  result.reserve(count);
  for (std::size_t i = 0; i < count; ++i) {
    result.push_back(next_key_for_vbucket_set(vbuckets));
  }
  return result;
}

auto
key_generator::next_key_for_parent(const std::string& parent_key) -> std::string
{
  auto parent_vbucket = map_key_to_vbucket_id(parent_key, number_of_vbuckets_);
  return next_key_for_vbucket(parent_vbucket);
}

auto
key_generator::next_keys_for_parent(std::size_t count,
                                    const std::string& parent_key,
                                    bool skip_duplicates) -> std::vector<std::string>
{
  auto parent_vbucket = map_key_to_vbucket_id(parent_key, number_of_vbuckets_);
  return next_keys_for_vbucket(count, parent_vbucket, skip_duplicates);
}

auto
key_generator::next_key_for_node(const key_value_node& node, const std::string& type) -> std::string
{
  return next_key_for_vbucket_set(node.vbuckets(type));
}

auto
key_generator::next_keys_for_node(std::size_t count,
                                  const key_value_node& node,
                                  const std::string& type,
                                  bool skip_duplicates) -> std::vector<std::string>
{
  return next_keys_for_vbucket_set(count, node.vbuckets(type), skip_duplicates);
}

namespace
{
auto
extract_endpoints(const couchbase::core::topology::configuration& config)
  -> std::vector<std::string>
{
  std::vector<std::string> default_plain_endpoints;
  std::vector<std::string> default_tls_endpoints;
  std::vector<std::string> external_plain_endpoints;
  std::vector<std::string> external_tls_endpoints;

  for (const auto& node : config.nodes) {
    if (auto port = node.services_plain.key_value; port) {
      default_plain_endpoints.push_back(fmt::format("{}:{}", node.hostname, *port));
    }
    if (auto port = node.services_tls.key_value; port) {
      default_tls_endpoints.push_back(fmt::format("{}:{}", node.hostname, *port));
    }
    if (auto external = node.alt.find("external"); external != node.alt.end()) {
      const auto& alt_node = external->second;
      if (auto port = alt_node.services_plain.key_value; port) {
        external_plain_endpoints.push_back(fmt::format("{}:{}", alt_node.hostname, *port));
      }
      if (auto port = alt_node.services_tls.key_value; port) {
        external_tls_endpoints.push_back(fmt::format("{}:{}", alt_node.hostname, *port));
      }
    }
  }

  // prefer external addresses if all nodes have them
  if (external_tls_endpoints.size() >= default_plain_endpoints.size()) {
    return external_tls_endpoints;
  }
  if (external_plain_endpoints.size() >= default_plain_endpoints.size()) {
    return external_plain_endpoints;
  }
  // prefer TLS addresses if all nodes have them
  if (default_tls_endpoints.size() >= default_plain_endpoints.size()) {
    return default_tls_endpoints;
  }
  return default_plain_endpoints;
}
} // namespace

auto
extract_vbucket_map(const couchbase::core::topology::configuration& config)
  -> std::map<std::string, key_value_node>
{

  auto vbmap_opt = config.vbmap;
  if (!vbmap_opt) {
    return {};
  }
  const auto& vbmap = *vbmap_opt;

  std::map<std::string, key_value_node> result;

  auto endpoints = extract_endpoints(config);
  for (std::size_t node_idx = 0; node_idx < endpoints.size(); ++node_idx) {
    const auto& endpoint = endpoints[node_idx];
    key_value_node node(node_idx, endpoint);

    auto this_node_idx = static_cast<std::int16_t>(node_idx);
    for (std::uint16_t vb = 0; vb < static_cast<std::uint16_t>(vbmap.size()); ++vb) {
      if (vbmap[vb][0] == this_node_idx) {
        node.add_active(vb);
      }
      if (vbmap[vb][1] == this_node_idx) {
        node.add_replica_1(vb);
      }
      if (vbmap[vb][2] == this_node_idx) {
        node.add_replica_2(vb);
      }
      if (vbmap[vb][3] == this_node_idx) {
        node.add_replica_3(vb);
      }
    }

    result.emplace(endpoint, node);
  }

  return result;
}
} // namespace cbc
