wallet/db_accessors.h

#pragma once
namespace ro {
	//	Compile time test to see if a type can be directly read from or written to an sqlite3 file
	//	This can be used in if constexpr (is_sqlite3_field_type<T>::value)
	template <class T> struct is_sqlite3_field_type
	{
		template <typename U> static constexpr decltype(std::declval<Icompiled_sql>().Isqlite3_bind(1, std::declval<U>()), bool()) test() {
			return true;
		}
		template <typename U> static constexpr bool test(int = 0) {
			return false;
		}
		static constexpr bool value = is_sqlite3_field_type::template test<T>();
	};

	static_assert(is_sqlite3_field_type<int>::value);

	//Owns a compiled sql statement and destroys it when it is deconstructed.
	//Has move semantics.
	class sql : public std::unique_ptr<Icompiled_sql> {
	public:
		class monostate {};
		sql(ISqlite3* p, const char* sz) :std::unique_ptr<Icompiled_sql>(sqlite3_prepare(p, sz)) {}
		sql(const std::unique_ptr<ISqlite3>& p, const char* sz) :std::unique_ptr<Icompiled_sql>(sqlite3_prepare(p.get(), sz)) {}
		//	copy constructor
		sql(const sql& a) = delete;
		//	move constructor
		sql(sql&& p) :std::unique_ptr<Icompiled_sql>(p.release()) { }
		//	copy assignment
		sql& operator=(const sql) = delete;
		//	Move assignment
		sql& operator=(sql&& p) {
			std::unique_ptr<Icompiled_sql>::reset(p.release());
		}
		sql(Icompiled_sql* p) :std::unique_ptr<Icompiled_sql>(p) {}
		sql(std::unique_ptr<Icompiled_sql>&& p) :std::unique_ptr<Icompiled_sql>(p.release()) { }
		~sql() = default;
		template <typename T>auto column(int i) const {
			if constexpr (ro::is_blob_field_type<T>::value) {
				auto st = (*this)->Isqlite3_column_blob(i);
				if (st.size_bytes() != sizeof(T)) throw BadDataException();
				static_assert (std::is_standard_layout<T>(), "not standard layout");
				static_assert (std::is_trivial<T>(), "not trivial");
				return reinterpret_cast<const T*>(&st[0]);
			}
			else if constexpr (std::is_integral<T>::value) {
				if constexpr (sizeof(T) > sizeof(int_least32_t)) {
					T retval = (*this)->Isqlite3_column_int64(i);
					return retval;
				}
				else {
					T retval = (*this)->Isqlite3_column_int(i);
					return retval;
				}
			}
			else if constexpr (std::is_same_v<std::remove_cvref_t<T>, std::span<const byte>>) {
				return (*this)->Isqlite3_column_blob(i);
			}
			else if constexpr (std::is_same_v<std::remove_cvref_t<T>, const char*>) {
				auto sz{ (*this)->Isqlite3_column_text(i) };
//				if (!IsValidUtf8String(sz)) throw NonUtf8DataInDatabase();
				return sz;
			}
			else {
				assert(false);
					//, "Don't know how to read this datatype from database");
				return monostate();  //should generate somewhat relevant type error at compile time.
			}
		}

		template <typename T>const sql& read(int i, T& j) const{
			if constexpr (ro::is_blob_field_type<T>::value) {
				auto st = (*this)->Isqlite3_column_blob(i);
				if (st.size_bytes() != sizeof(T)) throw BadDataException();
				static_assert (std::is_standard_layout<T>(), "not standard layout");
				static_assert (std::is_trivial<T>(), "not trivial");
				j = *reinterpret_cast<const T*>(&st[0]);
			}
			else if constexpr (std::is_integral<T>::value) {
				if constexpr (sizeof(T) > sizeof(int_least32_t)) {
					j = (*this)->Isqlite3_column_int64(i);
				}
				else {
					j = (*this)->Isqlite3_column_int(i);
				}
			}
			else if constexpr (std::is_same_v<std::remove_cvref_t<T>, std::span<const byte>>) {
				j = (*this)->Isqlite3_column_blob(i);
			}
			else if constexpr (std::is_same_v<std::remove_cvref_t<T>, const char*>) {
				j = (*this)->Isqlite3_column_text(i);
			}
			else {
				assert(false);
					//, "Don't know how to read this datatype from database")
				j = monostate();  //Should generate somewhat relevant error at compile time.
			}
			return *this;
		}

		void bind(int i, monostate) { (*this)->Isqlite3_bind(i); }
		template < typename T,
			typename std::enable_if<is_sqlite3_field_type<T>::value, int >::type dummy_arg = 0 >
			void bind(int i, T j) {
			(*this)->Isqlite3_bind(i, j);
		}
		template < typename T,
			typename std::enable_if<!is_sqlite3_field_type<T>::value, int >::type dummy_arg = 0 >
			void bind(int i, const T& j) {
			static_assert(ro::is_serializable<T>::value, "Don't know how to store this type in a database");
			(*this)->Isqlite3_bind(i, ro::serialize(j));
		}
		typedef Icompiled_sql::sql_result result;
		result step() {
			return (*this)->Isqlite3_step();
		}
		void final_step() {
			if (step() != result::DONE) throw SQLexception("SQL: Unexpected rows remaining");
		}
		void reset() {
			(*this)->Isqlite3_reset();
		}//	https://sqlite.org/c3ref/reset.html

		template<typename T, typename ...Args> void bind(int i, const T& first, const Args& ...args) {
			bind(i, first);
			bind(i + 1, args...);
		}
		template<typename ...Args> void do_one(const Args& ...args) {
			reset();
			if constexpr (sizeof...(args) > 0) {
				bind(1, args...);
			}
			final_step();
		}
		template<typename ...Args> auto read_one(const Args& ...args) {
			reset();
			if constexpr (sizeof...(args) > 0) {
				bind(1, args...);
			}
			return step() == result::ROW;
		}
	};

	class sql_update :sql {
	public:
		using sql::sql;
		sql_update(ISqlite3* p, const char* sz) : sql(p, sz) {}
		template<typename ...Args> void operator()(const Args& ...args) {
			do_one(args...);
		}
	};
}

class sql_update_to_misc :ro::sql {
public:
	sql_update_to_misc(ISqlite3* p) : sql(p, R"|(REPLACE INTO "Misc" VALUES(?1, ?2);)|") {}
	sql_update_to_misc(const std::unique_ptr<ISqlite3>& p) : sql_update_to_misc(p.get()) {}
	template<typename T>void operator()(int i, const T& j) {
		do_one(i, j);
	}
	template<typename T>void operator()(int i, T* j) {
		do_one(i, j);
	}
};

class sql_read_from_misc :ro::sql {
public:
	sql_read_from_misc(ISqlite3 *p) : sql(p, R"|(SELECT "m" FROM "Misc" WHERE "index" = ?1;)|") {}
	sql_read_from_misc(const std::unique_ptr<ISqlite3>& p) : sql_read_from_misc(p.get()){}
	auto operator()(int i) {
		return read_one(i);
	}
	template<typename T>auto value() {
		return column<T>(0);
	}
	template <typename T> void read(T& j) const {
		sql::read<T>(0,j);
	}
};

class sql_insert_name {
	ro::sql csql_begin;
	ro::sql csql_into_names;
	ro::sql csql_namekey_into_keys;
	ro::sql csql_commit;
public:
	sql_insert_name(ISqlite3* p) :
		csql_begin(p, R"|(BEGIN;)|"),
		csql_into_names(p, R"|(INSERT OR ROLLBACK INTO "Names" VALUES(?1);)|"),
		csql_namekey_into_keys(p, R"|(INSERT OR ROLLBACK INTO "Keys" VALUES(?1, last_insert_rowid(), 1);)|"),
		csql_commit(p, R"|(COMMIT;)|") {}
	sql_insert_name(const std::unique_ptr<ISqlite3>& p) : sql_insert_name(p.get()) {}
	void operator()(const char* psz, const ristretto255::point& pt) {
		csql_begin.do_one();
		try {
			csql_into_names.do_one(psz);
			csql_namekey_into_keys.do_one(pt);
		}
		catch (const std::exception & e) {
			csql_commit.do_one();
			throw e;
		}
		csql_commit.do_one();
	}
};

class sql_read_name :ro::sql {
public:
	sql_read_name(ISqlite3* p) : sql(p, R"|(SELECT * FROM "Names" WHERE OID = ?1;)|") {}
	sql_read_name(const std::unique_ptr<ISqlite3>& p) : sql_read_name(p.get()) {}
	bool operator()(int i) {
		return read_one(i) == Icompiled_sql::ROW;
	}
	auto name() const {
		return sql::column<const char*>(0);
	}
};



constexpr auto WALLET_FILE_IDENTIFIER (0x56d34bc5a655dd1fi64);
constexpr auto WALLET_FILE_SCHEMA_VERSION_0_0(1);