query/include/matador/orm/session.hpp

#ifndef QUERY_SESSION_HPP
#define QUERY_SESSION_HPP

#include "matador/orm/error_code.hpp"
#include "matador/orm/session_query_builder.hpp"

#include "matador/query/query.hpp"

#include "matador/sql/column_generator.hpp"
#include "matador/sql/connection.hpp"
#include "matador/sql/connection_pool.hpp"
#include "matador/sql/statement.hpp"

#include "matador/object/object_ptr.hpp"
#include "matador/object/object_definition.hpp"
#include "matador/object/schema.hpp"

#include <unordered_map>

namespace matador::orm {

utils::error make_error(error_code ec, const std::string &msg);

class session final {
public:
  explicit session(sql::connection_pool<sql::connection> &pool);

  template<typename Type>
  [[nodiscard]] utils::result<void, utils::error> attach(const std::string &table_name) const;

  utils::result<void, utils::error> create_schema() const;

  template<typename Type>
  utils::result<object::object_ptr<Type>, utils::error> insert(Type *obj);

  template< class Type, typename... Args >
  utils::result<object::object_ptr<Type>, utils::error> insert(Args&&... args) {
    return insert(new Type(std::forward<Args>(args)...));
  }

  template<typename Type, typename PrimaryKeyType>
  utils::result<object::object_ptr<Type>, utils::error> find(const PrimaryKeyType &pk) {
    auto c = pool_.acquire();
    if (!c.valid()) {
      return utils::failure(make_error(error_code::NoConnectionAvailable, "Failed to acquire connection."));
    }
    auto info = schema_->info<Type>();
    if (!info) {
      return utils::failure(make_error(error_code::UnknownType, "Failed to determine requested type."));
    }

    session_query_builder eqb(*schema_);
    auto data = eqb.build<Type>(pk);
    if (!data.is_ok()) {
      return utils::failure(make_error(error_code::FailedToBuildQuery, "Failed to build query for type " + info->get().name() + "."));
    }

    auto obj = build_select_query(data.release()).template fetch_one<Type>(*c);

    if (!obj) {
      return utils::failure(obj.err());
    }
    if (!obj->get()) {
      return utils::failure(make_error(error_code::FailedToFindObject, "Failed to find object of type " + info->get().name() + " with primary key " + std::to_string(pk) + "."));
    }
    return utils::ok(object::object_ptr<Type>{ obj.release() });
  }

  template<typename Type>
  utils::result<sql::query_result<Type>, utils::error> find() {
    auto c = pool_.acquire();
    if (!c.valid()) {
      return utils::failure(make_error(error_code::NoConnectionAvailable, "Failed to acquire connection."));
    }
    auto info = schema_->info<Type>();
    if (!info) {
      return utils::failure(make_error(error_code::UnknownType, "Failed to determine requested type."));
    }

    session_query_builder eqb(*schema_);
    auto data = eqb.build<Type>();
    if (!data.is_ok()) {
      return utils::failure(make_error(error_code::FailedToBuildQuery, "Failed to build query for type " + info->get().name() + "."));
    }

    return build_select_query(data.release()).template fetch_all<Type>(*c);
  }

  template<typename Type>
  utils::result<query::query_from_intermediate, utils::error> select() {
    auto c = pool_.acquire();
    if (!c.valid()) {
      return utils::failure(make_error(error_code::NoConnectionAvailable, "Failed to acquire connection."));
    }
    auto info = schema_->info<Type>();
    if (!info) {
      return utils::failure(make_error(error_code::UnknownType,  "Failed to determine requested type."));
    }

    session_query_builder eqb(*schema_);
    auto data = eqb.build<Type>();
    if (!data.is_ok()) {
      return utils::failure(make_error(error_code::FailedToBuildQuery, "Failed to build query for type " + info->get().name() + "."));
    }

    return utils::ok(build_select_query(data.release()).template fetch_all<Type>(*c));
  }

  template<typename Type>
  utils::result<void, utils::error> drop_table();
  utils::result<void, utils::error> drop_table(const std::string &table_name) const;

  [[nodiscard]] utils::result<sql::query_result<sql::record>, utils::error> fetch(const sql::query_context &q) const;
  [[nodiscard]] size_t execute(const std::string &sql) const;
  [[nodiscard]] sql::statement prepare(const sql::query_context& q) const;

  [[nodiscard]] std::vector<object::attribute_definition> describe_table(const std::string &table_name) const;
  [[nodiscard]] bool table_exists(const std::string &table_name) const;

  [[nodiscard]] const sql::dialect& dialect() const;

private:
  friend class query_select;

  static query::fetchable_query build_select_query(entity_query_data &&data);

private:
  sql::connection_pool<sql::connection> &pool_;
  const sql::dialect &dialect_;

  std::unique_ptr<object::schema> schema_;
  mutable std::unordered_map<std::string, object::object_definition> prototypes_;
};

template<typename Type>
[[nodiscard]] utils::result<void, utils::error> session::attach(const std::string &table_name) const {
  return schema_->attach<Type>(table_name);
}

template<typename Type>
utils::result<object::object_ptr<Type>, utils::error> session::insert(Type *obj)
{
  auto c = pool_.acquire();
  auto info = schema_->info<Type>();
  if (!info) {
    return utils::failure(info.err());
  }

  auto res = query::query::insert()
    .into(info->get().name(), sql::column_generator::generate<Type>(*schema_, true))
    .values(*obj)
    .execute(*c);
  if (!res) {
      return utils::failure(res.err());
  }

  return utils::ok(object::object_ptr{obj});
}

template<typename Type>
utils::result<void, utils::error> session::drop_table() {
  auto info = schema_->info<Type>();
  if (info) {
    return drop_table(info->get().name());
  }

  return utils::failure(info.err());
}

}
#endif //QUERY_SESSION_HPP