1 files changed, 127 insertions, 0 deletions
diff --git a/src/database/select_query.hpp b/src/database/select_query.hpp
new file mode 100644
index 0000000..f4d71af
--- /dev/null
+++ b/src/database/select_query.hpp
@@ -0,0 +1,127 @@
+#pragma once
+
+#include <database/statement.hpp>
+#include <database/query.hpp>
+#include <logger/logger.hpp>
+#include <database/row.hpp>
+
+#include <utils/optional_bool.hpp>
+
+#include <vector>
+#include <string>
+
+#include <sqlite3.h>
+
+using namespace std::string_literals;
+
+template <typename T>
+typename std::enable_if<std::is_integral<T>::value, sqlite3_int64>::type
+extract_row_value(Statement& statement, const int i)
+{
+  return sqlite3_column_int64(statement.get(), i);
+}
+
+template <typename T>
+typename std::enable_if<std::is_same<std::string, T>::value, T>::type
+extract_row_value(Statement& statement, const int i)
+{
+  const auto size = sqlite3_column_bytes(statement.get(), i);
+  const unsigned char* str = sqlite3_column_text(statement.get(), i);
+  std::string result(reinterpret_cast<const char*>(str), static_cast<std::size_t>(size));
+  return result;
+}
+
+template <typename T>
+typename std::enable_if<std::is_same<OptionalBool, T>::value, T>::type
+extract_row_value(Statement& statement, const int i)
+{
+  const auto integer = sqlite3_column_int(statement.get(), i);
+  OptionalBool result;
+  if (integer > 0)
+    result.set_value(true);
+  else if (integer < 0)
+    result.set_value(false);
+  return result;
+}
+
+template <std::size_t N=0, typename... T>
+typename std::enable_if<N < sizeof...(T), void>::type
+extract_row_values(Row<T...>& row, Statement& statement)
+{
+  using ColumnType = typename std::remove_reference<decltype(std::get<N>(row.columns))>::type;
+
+  auto&& column = std::get<N>(row.columns);
+  column.value = static_cast<decltype(column.value)>(extract_row_value<typename ColumnType::real_type>(statement, N));
+
+  extract_row_values<N+1>(row, statement);
+}
+
+template <std::size_t N=0, typename... T>
+typename std::enable_if<N == sizeof...(T), void>::type
+extract_row_values(Row<T...>&, Statement&)
+{}
+
+template <typename... T>
+struct SelectQuery: public Query
+{
+    SelectQuery(std::string table_name):
+        Query("SELECT"),
+        table_name(table_name)
+    {
+      this->insert_col_name();
+      this->body += " from " + this->table_name;
+    }
+
+    template <std::size_t N=0>
+    typename std::enable_if<N < sizeof...(T), void>::type
+    insert_col_name()
+    {
+      using ColumnsType = std::tuple<T...>;
+      using ColumnType = typename std::remove_reference<decltype(std::get<N>(std::declval<ColumnsType>()))>::type;
+
+      this->body += " "s + ColumnType::name;
+
+      if (N < (sizeof...(T) - 1))
+        this->body += ", ";
+
+      this->insert_col_name<N+1>();
+    }
+    template <std::size_t N=0>
+    typename std::enable_if<N == sizeof...(T), void>::type
+    insert_col_name()
+    {}
+
+  SelectQuery& where()
+    {
+      this->body += " WHERE ";
+      return *this;
+    };
+
+    SelectQuery& order_by()
+    {
+      this->body += " ORDER BY ";
+      return *this;
+    }
+
+    SelectQuery& limit()
+    {
+      this->body += " LIMIT ";
+      return *this;
+    }
+
+    auto execute(sqlite3* db)
+    {
+      auto statement = this->prepare(db);
+      std::vector<Row<T...>> rows;
+      while (sqlite3_step(statement.get()) == SQLITE_ROW)
+        {
+          Row<T...> row(this->table_name);
+          extract_row_values(row, statement);
+          rows.push_back(row);
+        }
+      return rows;
+    }
+
+    const std::string table_name;
+};
+