#include "leveldb/write_batch.h"

#include "db/dbformat.h"
#include "leveldb/db.h"
#include "util/coding.h"
#include "leveldb/my_leveldb.h"
#include "unordered_map"
#include <sstream>
namespace leveldb {
//反序列化为字段数组
void MyLevelDB::ParseValue(const std::string& value_str,
                           FieldArray& resFieldArray) {
  std::stringstream ss(value_str);
  std::string segment;

  // 按逗号分割字符串
  while (std::getline(ss, segment, ',')) {
    std::string key;
    std::string value;
    std::stringstream kv(segment);

    if (std::getline(kv, key, ':') && std::getline(kv, value, ':')) {
      if (!key.empty() && !value.empty()) {
        resFieldArray.push_back(std::make_pair(key, value));
        // std::cout << ((resFieldArray.back()).first).data() << std::endl;
      } else {
        std::cerr << "Invalid key-value pair: " << segment << std::endl;
      }
    } else {
      std::cerr << "Failed to parse segment: " << segment << std::endl;
    }
  }
}


//序列化为字符串
void MyLevelDB::SerializeValue(const FieldArray& fields,
                               std::string& resString) {
  resString.clear();
  for (int i = 0; i < fields.size(); i++) {
    const std::string& key = fields[i].first;
    const std::string& value = fields[i].second;

    resString += key + ":" +value;
    if (i != fields.size() - 1) {
      resString += ",";
    }
  }
}

Status MyLevelDB::PutWithFields(const WriteOptions& options,
                                const std::string& key,
                                const FieldArray& fields) {
  std::string value;
  SerializeValue(fields, value);  // 将 fields 序列化为字符串
  auto slice_key = Slice(key.c_str());
  auto slice_value = Slice(value.c_str());

  WriteBatch batch;
  Status s = _fields_db->Put(options, slice_key, slice_value);  // 写入数据
  if (!s.ok()) {
    return s;  // 如果写入失败，直接返回错误
  }

  // 记录所有操作，以便失败时可以回滚
  std::vector<std::pair<std::string, std::string>> changes;
  changes.push_back({key, value});  // 记录字段数据的变化

  // 更新索引
  std::unordered_map<int, int> match;
  std::unique_lock<std::mutex> l(mutex_);
  for (int i = 0; i < fields.size(); i++) {
    for (size_t idx = 0; idx < index_list_.size(); idx++) {
      const auto& i_name = index_list_[idx];
      if (fields[i].first == i_name) {
        match[i] = idx;  // 找到匹配的字段
        break;
      }
    }
  }

  // 生成索引的键值对
  for (auto item : match) {
    std::string composed_key;
    composed_key += fields[item.first].second + ":" + key;
    batch.Put(Slice(composed_key.c_str()), Slice());  // 将索引数据加入批处理中
    changes.push_back({composed_key, ""});            // 记录索引的变化
  }

  // 提交批处理
  s = _fields_db->Write(options, &batch);
  if (!s.ok()) {
    // 如果批处理写入失败，回滚之前的操作
    std::cerr << "Failed to commit batch, rolling back." << std::endl;

    // 执行回滚：撤销所有已经提交的变更
    for (const auto& change : changes) {
      _fields_db->Delete(WriteOptions(),
                         Slice(change.first));  // 删除已修改的键值对
    }

    return s;  // 返回错误，表示操作失败
  }

  return Status::OK();  // 一切正常，返回成功
}



Status MyLevelDB::FindKeysByField(const ReadOptions& options, const Field field,
                                  std::vector<std::string>* keys) {
  auto it = _fields_db->NewIterator(options);
  it->SeekToFirst();
  keys->clear();
  while (it->Valid()) {
    auto val = it->value();
    FieldArray arr;
    auto str_val = std::string(val.data(), val.size());
    ParseValue(str_val, arr);
    for (auto pr : arr) {
      if (pr.first == field.first && pr.second == field.second) {
        Slice key = it->key();
        keys->push_back(std::string(key.data(), key.size()));
        break;
      }
    }
    it->Next();
  }
  delete it;
  return Status::OK();
}

Status MyLevelDB::CreateIndexOnField(const std::string& field_name) {
  // 检查索引是否已经存在
  for (const auto& field : this->index_list_) {
    if (field == field_name) {
      return Status::InvalidArgument(field_name,
                                     "Index already exists for this field");
    }
  }

  // 将新的索引字段添加到索引列表
  index_list_.push_back(field_name);

  Options op = _op;
  DB* field_db;
  op.index_mode = true;

  WriteBatch batch;  // 创建批处理操作
  Status status = DB::Open(op, _db_name + "_index_" + field_name, &field_db);
  if (!status.ok()) {
    std::cerr << "Failed to open index DB: " << status.ToString() << std::endl;
    return status;  // 如果打开数据库失败，返回错误
  }

  index_db.push_back(field_db);  // 将新创建的索引数据库添加到列表

  // 记录所有变更
  std::vector<std::string> changes;
  changes.push_back("index_" + field_name);  // 记录索引字段的变更

  // 在批处理中添加索引数据
  batch.Put(Slice(("index_" + field_name).c_str()),
            Slice());  // 添加索引记录到批处理中

  // 提交批处理
  status = _fields_db->Write(WriteOptions(), &batch);
  if (!status.ok()) {
    // 如果写入失败，执行回滚操作
    std::cerr << "Failed to commit index: " << status.ToString() << std::endl;

    // 执行回滚：撤销所有已做的更改
    for (const auto& change : changes) {
      _fields_db->Delete(WriteOptions(),
                         Slice(change.c_str()));  // 删除已创建的索引
    }

    return status;  // 返回失败状态，确保不会提交任何变更
  }

  return Status::OK();  // 操作成功，返回成功状态
}


Status MyLevelDB::DeleteIndex(std::string& field_name) {
  // 查找索引字段
  auto it = std::find(index_list_.begin(), index_list_.end(), field_name);
  if (it == index_list_.end()) {
    return Status::NotFound("Index not found for this field");
  }

  WriteBatch batch;  // 创建批处理操作

  // 删除索引字段
  index_list_.erase(it);

  batch.Delete(Slice(("index_" + field_name).c_str()));  // 删除索引字段记录

  // 记录已删除的索引
  std::vector<std::string> changes;
  changes.push_back("index_" + field_name);

  // 提交批处理
  Status s = _fields_db->Write(WriteOptions(), &batch);
  if (!s.ok()) {
    // 如果删除操作失败，回滚事务
    std::cerr << "Failed to delete index: " << s.ToString() << std::endl;

    // 执行回滚：恢复删除的索引
    for (const auto& change : changes) {
      batch.Put(Slice(change.c_str()), Slice());  // 恢复索引记录
    }

    _fields_db->Write(WriteOptions(), &batch);  // 再次提交恢复的批处理
    return s;  // 返回失败，确保不会提交任何变化
  }

  return Status::OK();  // 删除成功，返回成功状态
}


void MyLevelDB::QueryByIndex(const ReadOptions& options, Field& field,
                             std::vector<std::string>& keys) {
  int i = 0;
  for (; i < index_list_.size(); i++) {
    if (index_list_[i] == field.first) {
      break;
    }
  }
  assert(i != index_list_.size());

  auto it = index_db[i]->NewIterator(options);
  it->SeekToFirst();
  while (it->Valid()) {
    auto val = it->key();
    auto str_val = std::string(val.data(), val.size());

    std::string key;
    std::string value;
    std::stringstream kv(str_val);

    std::getline(kv, key, ':');
    std::getline(kv, value, ':');
    if (key == field.second) {
      keys.push_back(value);
    }
    it->Next();
  }
  delete it;
}


Status MyLevelDB::Put(const WriteOptions& options, const Slice& key,
                    const Slice& value) {
  return _fields_db->Put(options, key, value);
}

Status MyLevelDB::Delete(const WriteOptions& options, const Slice& key) {
  return _fields_db->Delete(options, key);
}

Status MyLevelDB::Write(const WriteOptions& options, WriteBatch* updates) {
  assert(0);
  return Status();
}

Status MyLevelDB::Get(const ReadOptions& options, const Slice& key,
                    std::string* value) {
  return _fields_db->Get(options, key, value);
}

Iterator* MyLevelDB::NewIterator(const ReadOptions& options) {
  return _fields_db->NewIterator(options);
}

const Snapshot* MyLevelDB::GetSnapshot() { return _fields_db->GetSnapshot(); }

void MyLevelDB::ReleaseSnapshot(const Snapshot* snapshot) {
  return _fields_db->ReleaseSnapshot(snapshot);
}

bool MyLevelDB::GetProperty(const Slice& property, std::string* value) {
  return false;
}

void MyLevelDB::GetApproximateSizes(const Range* range, int n,
                                    uint64_t* sizes) {
  /* uint64_t temp = 0;
  _main_db->GetApproximateSizes(range, n, sizes);
  for (auto& index_db : field_db_) {
    index_db->GetApproximateSizes(range, n, &temp);
    *sizes += temp;
  }*/
}

void MyLevelDB::CompactRange(const Slice* begin, const Slice* end) {
  _fields_db->CompactRange(begin, end);
}
}