#ifndef QUERY_ENTITY_QUERY_BUILDER_HPP
#define QUERY_ENTITY_QUERY_BUILDER_HPP

#include "matador/query/condition.hpp"
#include "matador/query/query_intermediates.hpp"

#include "matador/sql/connection.hpp"

#include "matador/object/schema.hpp"

#include "matador/utils/result.hpp"
#include "matador/utils/value.hpp"

#include <stack>
#include <unordered_set>

namespace matador::orm {

struct join_columns
{
  std::string join_column;
  std::string inverse_join_column;
};

class join_column_collector
{
public:
  template<class Type>
  join_columns collect() {
    join_columns_ = {};
    Type obj;

    access::process(*this, obj);

    return join_columns_;
  }
  template < class V >
  void on_primary_key(const char * /*id*/, V &, std::enable_if_t<std::is_integral_v<V> && !std::is_same_v<bool, V>>* = nullptr) {}
  static void on_primary_key(const char * /*id*/, std::string &, size_t) {}
  static void on_revision(const char * /*id*/, unsigned long long &/*rev*/) {}
  template<typename Type>
  static void on_attribute(const char * /*id*/, Type &, const utils::field_attributes &/*attr*/ = utils::null_attributes) {}
  template<class Pointer>
  static void on_belongs_to(const char * /*id*/, Pointer &obj, const utils::foreign_attributes &attr) {}
  template<class Pointer>
  static void on_has_one(const char * /*id*/, Pointer &obj, const utils::foreign_attributes &attr) {}
  template<class ContainerType>
  static void on_has_many(ContainerType &, const char *join_column, const utils::foreign_attributes &attr) {}
  template<class ContainerType>
  void on_has_many_to_many(const char * /*id*/, ContainerType &/*c*/, const char *join_column, const char *inverse_join_column, const utils::foreign_attributes &/*attr*/) {
    join_columns_.join_column = join_column;
    join_columns_.inverse_join_column = inverse_join_column;
  }
  template<class ContainerType>
  static void on_has_many_to_many(const char * /*id*/, ContainerType &/*c*/, const utils::foreign_attributes &/*attr*/) {}

private:
  join_columns join_columns_;
};

struct entity_query_data {
  std::shared_ptr<sql::table> root_table;
  std::string pk_column_name{};
  std::vector<sql::column> columns{};
  std::vector<query::join_data> joins{};
  std::unique_ptr<query::basic_condition> where_clause{};
};

enum class query_build_error : std::uint8_t {
  Ok = 0,
  UnknownType,
  MissingPrimaryKey,
  UnexpectedError
};

class query_builder_exception final : public std::exception
{
public:
  explicit query_builder_exception(const query_build_error error) : error_(error) {}

  [[nodiscard]] query_build_error error() const { return error_; }

private:
  const query_build_error error_;
};

class session_query_builder final
{
public:
  explicit session_query_builder(const object::schema &scm)
  : schema_(scm) {}

  template<class EntityType, typename PrimaryKeyType>
  utils::result<entity_query_data, query_build_error> build(const PrimaryKeyType &pk) {
    auto info = schema_.info<EntityType>();
    if (!info) {
      return utils::failure(query_build_error::UnknownType);
    }
    pk_ = pk;
    table_info_stack_.push({info.value(), std::make_shared<sql::table>(info.value().get().name(), build_alias('t', ++table_index))});
    entity_query_data_ = { table_info_stack_.top().table };
    processed_tables_.insert({info->get().name(), entity_query_data_.root_table});
    try {
      access::process(*this, info->get().prototype());

      return {utils::ok(std::move(entity_query_data_))};
    } catch (const query_builder_exception &ex) {
      return {utils::failure(ex.error())};
    } catch (...) {
      return {utils::failure(query_build_error::UnexpectedError)};
    }
  }

  template<class EntityType>
  utils::result<entity_query_data, query_build_error> build() {
    const auto info = schema_.info<EntityType>();
    if (!info) {
      return utils::failure(query_build_error::UnknownType);
    }
    pk_ = nullptr;
    table_info_stack_.push({info.value(), std::make_shared<sql::table>(info.value().get().name(), build_alias('t', ++table_index))});
    entity_query_data_ = { table_info_stack_.top().table };
    processed_tables_.insert({info->get().name(), entity_query_data_.root_table});
    try {
      access::process(*this, info->get().prototype());

      return {utils::ok(std::move(entity_query_data_))};
    } catch (const query_builder_exception &ex) {
      return {utils::failure(ex.error())};
    } catch (...) {
      return {utils::failure(query_build_error::UnexpectedError)};
    }
  }

  template < class V >
  void on_primary_key(const char *id, V &, std::enable_if_t<std::is_integral_v<V> && !std::is_same_v<bool, V>>* = nullptr)
  {
    push(id);
    if (!is_root_entity()) {
      return;
    }
    if (pk_.is_null()) {
      entity_query_data_.pk_column_name = id;
    } else if (pk_.is_integer()) {
      const auto t = std::make_shared<sql::table>(table_info_stack_.top().info.get().name());
        auto v = *pk_.as<V>();
        auto c = sql::column{t, id, ""};
        auto co = std::make_unique<query::condition<sql::column, V>>(c, query::basic_condition::operand_type::EQUAL, v);
      entity_query_data_.where_clause = std::move(co);
      entity_query_data_.pk_column_name = id;
    }
  }

  void on_primary_key(const char *id, std::string &, size_t);
  void on_revision(const char *id, unsigned long long &/*rev*/);

  template<typename Type>
  void on_attribute(const char *id, Type &, const utils::field_attributes &/*attr*/ = utils::null_attributes)
  {
    push(id);
  }

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

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

  template<class ContainerType>
  void on_has_many(const char * /*id*/, ContainerType &, const char *join_column, const utils::foreign_attributes &attr) {
    if (attr.fetch() == utils::fetch_type::EAGER) {
      const auto info = schema_.info<typename ContainerType::value_type::value_type>();
      if (!info) {
        throw query_builder_exception{query_build_error::UnknownType};
      }

      auto next = processed_tables_.find(info->get().name());
      if (next != processed_tables_.end()) {
        return;
      }
      table_info_stack_.push({info.value(), std::make_shared<sql::table>(info->get().name(), build_alias('t', ++table_index))});
      next = processed_tables_.insert({info->get().name(), table_info_stack_.top().table}).first;
      typename ContainerType::value_type::value_type obj;
      access::process(*this , obj);
      table_info_stack_.pop();

      auto pk = info->get().definition().primary_key();
      if (!pk) {
        throw query_builder_exception{query_build_error::MissingPrimaryKey};
      }

      append_join(
        sql::column{table_info_stack_.top().table, table_info_stack_.top().info.get().definition().primary_key()->name()},
        sql::column{next->second, join_column}
      );
    }
  }

  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) {
    if (attr.fetch() != utils::fetch_type::EAGER) {
      return;
    }
    const auto info = schema_.info<typename ContainerType::value_type::value_type>();
    if (!info) {
      throw query_builder_exception{query_build_error::UnknownType};
    }

    auto next = processed_tables_.find(info->get().name());
    if (next != processed_tables_.end()) {
      return;
    }
    auto relation = processed_tables_.find(id);
    if (relation == processed_tables_.end()) {
      relation = processed_tables_.insert({id, std::make_shared<sql::table>(id, build_alias('t', ++table_index))}).first;
    }

    table_info_stack_.push({info.value(), std::make_shared<sql::table>(info->get().name(), build_alias('t', ++table_index))});
    next = processed_tables_.insert({info->get().name(), table_info_stack_.top().table}).first;
    typename ContainerType::value_type::value_type obj;
    access::process(*this , obj);
    table_info_stack_.pop();

    auto pk = info->get().definition().primary_key();
    if (!pk) {
      throw query_builder_exception{query_build_error::MissingPrimaryKey};
    }

    append_join(
      sql::column{table_info_stack_.top().table, table_info_stack_.top().info.get().definition().primary_key()->name()},
      sql::column{relation->second, join_column}
    );
    append_join(
      sql::column{relation->second, inverse_join_column},
      sql::column{next->second, pk->name()}
    );
  }

  template<class ContainerType>
  void on_has_many_to_many(const char *id, ContainerType &/*cont*/, const utils::foreign_attributes &attr) {
    if (attr.fetch() != utils::fetch_type::EAGER) {
      return;
    }
    const auto info = schema_.info<typename ContainerType::value_type::value_type>();
    if (!info) {
      throw query_builder_exception{query_build_error::UnknownType};
    }

    auto next = processed_tables_.find(info->get().name());
    if (next != processed_tables_.end()) {
      return;
    }

    auto relation = processed_tables_.find(id);
    if (relation == processed_tables_.end()) {
      relation = processed_tables_.insert({id, std::make_shared<sql::table>(id, build_alias('t', ++table_index))}).first;
    }
    table_info_stack_.push({info.value(), std::make_shared<sql::table>(info->get().name(), build_alias('t', ++table_index))});
    next = processed_tables_.insert({info->get().name(), table_info_stack_.top().table}).first;
    typename ContainerType::value_type::value_type obj;
    access::process(*this , obj);
    table_info_stack_.pop();

    auto pk = info->get().definition().primary_key();
    if (!pk) {
      throw query_builder_exception{query_build_error::MissingPrimaryKey};
    }

    const auto join_columns = join_column_collector_.collect<typename ContainerType::value_type::value_type>();

    append_join(
      sql::column{table_info_stack_.top().table, table_info_stack_.top().info.get().definition().primary_key()->name()},
      sql::column{relation->second, join_columns.inverse_join_column}
    );
    append_join(
      sql::column{relation->second, join_columns.join_column},
      sql::column{next->second, pk->name()}
      // sql::column{std::make_shared<sql::table>(info->get().name()), pk->name()}
    );
  }

private:
  template<class Pointer>
  void on_foreign_object(const char *id, Pointer &, const utils::foreign_attributes &attr);
  void push(const std::string &column_name);
  static std::string build_alias(char prefix, unsigned int count);
  [[nodiscard]] bool is_root_entity() const;
  void append_join(const sql::column &left, const sql::column &right);

private:
  utils::value pk_;
  struct table_info {
    std::reference_wrapper<const object::basic_object_info> info;
    std::shared_ptr<sql::table> table;
  };

  std::stack<table_info> table_info_stack_;
  std::unordered_map<std::string, std::shared_ptr<sql::table>> processed_tables_;
  const object::schema &schema_;
  entity_query_data entity_query_data_;
  unsigned int column_index{0};
  unsigned int table_index{0};
  join_column_collector join_column_collector_;
};

template<class Pointer>
void session_query_builder::on_foreign_object(const char *id, Pointer &, const utils::foreign_attributes &attr) {
  if (attr.fetch() == utils::fetch_type::EAGER) {
    const auto info = schema_.info<typename Pointer::value_type>();
    if (!info) {
      throw query_builder_exception{query_build_error::UnknownType};
    }

    auto next = processed_tables_.find(info->get().name());
    if (next != processed_tables_.end()) {
      return;
    }
    table_info_stack_.push({info.value(), std::make_shared<sql::table>(info->get().name(), build_alias('t', ++table_index))});
    next = processed_tables_.insert({info->get().name(), table_info_stack_.top().table}).first;
    typename Pointer::value_type obj;
    access::process(*this, obj);
    table_info_stack_.pop();

    auto pk = info->get().definition().primary_key();
    if (!pk) {
      throw query_builder_exception{query_build_error::MissingPrimaryKey};
    }
    append_join(
      sql::column{table_info_stack_.top().table, id},
      sql::column{next->second, pk->name()}
    );
  } else {
    push(id);
  }
}

}
#endif //QUERY_ENTITY_QUERY_BUILDER_HPP