/*
  Copyright (c) 2014-2015 DataStax

  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.
*/

// The FNV1a hash code is based on work found here:
// http://www.isthe.com/chongo/tech/comp/fnv/index.html
// and is therefore public domain.

#include "result_metadata.hpp"

#include "common.hpp"

#include <iterator>

// This can be decreased to reduce hash collisions, but it will require
// additional memory.
#define LOAD_FACTOR 0.75

#define FNV1_64_INIT 0xcbf29ce484222325ULL
#define FNV1_64_PRIME 0x100000001b3ULL

namespace cass {

uint64_t fnv1a_hash_lower(StringRef s) {
  uint64_t h = FNV1_64_INIT;
  for(StringRef::const_iterator i = s.begin(), end = s.end(); i != end; ++i) {
      h ^= static_cast<uint64_t>(static_cast<unsigned char>(::tolower(*i)));
      h *= FNV1_64_PRIME;
    }
    return h;
}

ResultMetadata::ResultMetadata(size_t column_count) {
  defs_.reserve(column_count);

  size_t index_size = next_pow_2(static_cast<size_t>(column_count / LOAD_FACTOR) + 1);
  index_.resize(index_size, NULL);
  index_mask_ = index_size - 1;
}


size_t ResultMetadata::get(StringRef name,
                           ResultMetadata::IndexVec* result) const{
  result->clear();
  bool is_case_sensitive = false;

  if (name.size() > 0 && name.front() == '"' && name.back() == '"') {
    is_case_sensitive = true;
    name = name.substr(1, name.size() - 2);
  }

  size_t h = fnv1a_hash_lower(name) & index_mask_;

  size_t start = h;
  while (index_[h] != NULL && !iequals(name, StringRef(index_[h]->name, index_[h]->name_size))) {
    h = (h + 1) & index_mask_;
    if (h == start) {
      return 0;
    }
  }

  const ColumnDefinition* def = index_[h];

  if (def == NULL) {
    return 0;
  }

  if (!is_case_sensitive) {
    while (def != NULL) {
      result->push_back(def->index);
      def = def->next;
    }
  } else {
    while (def != NULL) {
      if (name.compare(StringRef(def->name, def->name_size)) == 0) {
        result->push_back(def->index);
      }
      def = def->next;
    }
  }

  return result->size();
}

void ResultMetadata::insert(ColumnDefinition& def) {
  defs_.push_back(def);

  StringRef name(def.name, def.name_size);

  size_t h = fnv1a_hash_lower(name) & index_mask_;

  if (index_[h] == NULL) {
    index_[h] = &defs_.back();
  } else {
    // Use linear probing to find an open bucket
    while (index_[h] != NULL && !iequals(name, StringRef(index_[h]->name, index_[h]->name_size))) {
      h = (h + 1) & index_mask_;
    }
    if (index_[h] == NULL) {
      index_[h] = &defs_.back();
    } else {
      ColumnDefinition* curr = index_[h];
      while (curr->next != NULL) {
        curr = curr->next;
      }
      curr->next = &defs_.back();
    }
  }
}

} // namespace cass