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/executor.hpp"
#include "matador/sql/statement.hpp"
#include "matador/sql/statement_cache.hpp"

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

#include <unordered_map>

namespace matador::orm {

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

struct session_context {
  utils::message_bus &bus;
  sql::connection_pool &pool;
  size_t cache_size{500};
};

template<typename Type>
class lazy_object_resolver final : public object::object_resolver<Type> {
public:
    explicit lazy_object_resolver(sql::statement &&stmt) : stmt_(std::move(stmt)) {}

    Type* resolve(const object::object_proxy<Type>& proxy) const override {
        return proxy.resolve();
    }

private:
    sql::statement stmt_;
};

class prototype_builder final {
public:
  explicit prototype_builder(const std::unordered_map<std::string, sql::statement> &statements_per_column)
  : statements_per_column_(statements_per_column) {}


  template < typename Type >
  Type build() const {
      Type obj;
      access::process(*this, obj);

      return obj;
  }

  template < class V >
  static void on_primary_key(const char * /*id*/, V &/*pk*/, const utils::primary_key_attribute& /*attr*/ = utils::default_pk_attributes) {}
  static void on_revision(const char * /*id*/, unsigned long long &/*rev*/) {}
  template<typename Type>
  static void on_attribute(const char * /*id*/, Type &/*obj*/, const utils::field_attributes &/*attr*/ = utils::null_attributes) {}
  template<class Pointer>
  void on_belongs_to(const char *id, Pointer &obj, const utils::foreign_attributes &attr) {
      const auto it = statements_per_column_.find(id);
      if (it == statements_per_column_.end()) {
          return;
      }


  }
  template<class Pointer>
  void on_has_one(const char *id, Pointer &obj, const utils::foreign_attributes &attr) {

  }
  template<class ContainerType>
  void on_has_many(const char * /*id*/, ContainerType &, const char *join_column, const utils::foreign_attributes &attr) {
  }
  template<class ContainerType>
  void on_has_many_to_many(const char *id, ContainerType &/*cont*/, const char *join_column, const char *inverse_join_column, const utils::foreign_attributes &attr) {

  }
  template<class ContainerType>
  void on_has_many_to_many(const char *id, ContainerType &/*cont*/, const utils::foreign_attributes &attr) {

  }

private:
  const std::unordered_map<std::string, sql::statement> &statements_per_column_;
};
class session final : public sql::executor {
public:
  explicit session(session_context &&ctx);

  template<typename Type>
  [[nodiscard]] utils::result<void, utils::error> attach(const std::string &table_name) const;
  template<typename Type, typename SuperType>
  [[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 info = schema_->info<Type>();
    if (!info) {
      return utils::failure(make_error(error_code::UnknownType, "Failed to determine requested type."));
    }

    session_query_builder eqb(*schema_, *this);
    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 res = build_select_query(data.release()).prepare(*this);
    // auto obj = build_select_query(data.release()).template fetch_one<Type>(*this);

    if (!res) {
      return utils::failure(res.err());
    }
    auto stmt_result = res->bind(0, const_cast<PrimaryKeyType&>(pk)).template fetch_one<Type>();
    if (!stmt_result) {
      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>{ stmt_result->release() });
  }

  template<typename Type>
  utils::result<sql::query_result<Type>, utils::error> find() {
    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_, *this);
    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() + "."));
    }

    const auto ctx = build_select_query(data.release()).compile(dialect_, query::query_mode::Prepared);

    auto result = fetch(ctx);
    if (!result.is_ok()) {
      return utils::failure(result.err());
    }
    return utils::ok(sql::query_result<Type>(result.release(), []{ return new Type();}));
  }

  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_all(const sql::query_context &q) const;
  [[nodiscard]] utils::result<size_t, utils::error> execute(const std::string &sql) 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;

  void dump_schema(std::ostream &os) const;

  [[nodiscard]] utils::result<std::unique_ptr<sql::query_result_impl>, utils::error> fetch(const sql::query_context &ctx) const override;
  [[nodiscard]] utils::result<size_t, utils::error> execute(const sql::query_context &ctx) const override;
  [[nodiscard]] utils::result<sql::statement, utils::error> prepare(const sql::query_context &ctx) override;
  [[nodiscard]] std::string str( const sql::query_context& ctx ) const override;
  [[nodiscard]] const sql::dialect& dialect() const override;

private:
  friend class query_select;

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

private:
  mutable sql::statement_cache cache_;
  const sql::dialect &dialect_;

  std::unique_ptr<object::repository> 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, typename SuperType>
utils::result<void, utils::error> session::attach( const std::string& table_name ) const {
  return schema_->attach<Type, SuperType>(table_name);
}

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