insert query builder improvements progress

include/matador/query/insert_query_builder.hpp

@@ -1,6 +1,8 @@
 #ifndef MATADOR_INSERT_QUERY_BUILDER_HPP
 #define MATADOR_INSERT_QUERY_BUILDER_HPP
 
+#include <utility>
+
 #include "matador/object/collection.hpp"
 
 #include "matador/query/basic_schema.hpp"
@@ -69,6 +71,93 @@ struct insert_step {
   std::function<void()> make_object_persistent{};
 };
 
+class insert_step2 {
+public:
+  explicit insert_step2(sql::query_context ctx)
+  : ctx_(std::move(ctx)) {}
+  virtual ~insert_step2() = default;
+
+  virtual utils::result<void, utils::error> prepare(sql::executor &conn) const = 0;
+  virtual utils::result<void, utils::error> insert(sql::statement &stmt) const = 0;
+
+protected:
+  utils::primary_key_accessor pk_accessor_;
+  sql::query_context ctx_;
+};
+
+template <typename ObjectType>
+class insert_step_sequence : public insert_step2 {
+public:
+  insert_step_sequence(sql::query_context ctx, const object::object_ptr<ObjectType>& ptr, abstract_pk_generator& pk_generator)
+  : insert_step2(std::move(ctx))
+  , ptr_(ptr)
+  , pk_generator_(pk_generator){}
+
+  utils::result<void, utils::error> prepare(sql::executor& conn) const override {
+    auto result = pk_generator_.next_id(conn);
+    if (!result.is_ok()) {
+      return utils::failure(result.err());
+    }
+    pk_accessor_.set(*ptr_, *result);
+
+    return utils::ok<void>();
+  }
+
+  utils::result<void, utils::error> insert(sql::statement& stmt) const override {
+    stmt.bind(*ptr_);
+
+    if (const auto exec_result = stmt.execute(); !exec_result.is_ok()) {
+      return utils::failure(exec_result.err());
+    }
+
+    ptr_.change_state(object::object_state::Persistent);
+    return utils::ok<void>();
+  }
+
+private:
+  object::object_ptr<ObjectType> ptr_;
+  abstract_pk_generator& pk_generator_;
+};
+
+template <typename ObjectType>
+class insert_step_identity : public insert_step2 {
+public:
+  insert_step_identity(sql::query_context ctx, const object::object_ptr<ObjectType>& ptr)
+  : insert_step2(std::move(ctx))
+  , ptr_(ptr) {}
+
+  utils::result<void, utils::error> prepare(sql::executor& conn) const override {
+    return utils::ok<void>();
+  }
+
+  utils::result<void, utils::error> insert(sql::statement& stmt) const override {
+    stmt.bind(*ptr_);
+
+    auto record = stmt.fetch_one();
+    if (!record.is_ok()) {
+      return utils::failure(record.err());
+    }
+    if (!record.value().has_value()) {
+      return utils::failure(utils::error(error_code::FailedToFindObject, "Failed to insert object and retrieve identity."));
+    }
+
+    const auto pk_name = info.primary_key_attribute()->name();
+    const table_column pk_col(&it->second.table(), pk_name);
+    step.apply_returning = [ptr, &step, pk_name = pk_name](const sql::record &rec) {
+      const auto& f = rec.at(pk_name);
+      utils::identifier id;
+      id.assign(f.value());
+      step.pk_accessor.set(*ptr, id);
+    };
+
+    ptr_.change_state(object::object_state::Persistent);
+    return utils::ok<void>();
+  }
+
+private:
+  object::object_ptr<ObjectType> ptr_;
+};
+
 template<class ObjectType>
 class insert_query_builder {
 public: