From df2f1d7a2f9b7143010a49d98dba0ed99b52c759 Mon Sep 17 00:00:00 2001
From: Sebastian Messmer <messmer@cryfs.org>
Date: Tue, 22 May 2018 00:04:00 -0700
Subject: [PATCH] Start implementing ValueType

---
 src/cpp-utils/CMakeLists.txt                |  1 +
 src/cpp-utils/value_type/ConfigBuilder.cpp  |  1 +
 src/cpp-utils/value_type/ConfigBuilder.h    | 61 ++++++++++++++++
 src/cpp-utils/value_type/ValueType.cpp      |  5 +-
 src/cpp-utils/value_type/ValueType.h        | 79 +++++++++++----------
 test/cpp-utils/value_type/ValueTypeTest.cpp | 58 ++++++++++-----
 6 files changed, 143 insertions(+), 62 deletions(-)
 create mode 100644 src/cpp-utils/value_type/ConfigBuilder.cpp
 create mode 100644 src/cpp-utils/value_type/ConfigBuilder.h

diff --git a/src/cpp-utils/CMakeLists.txt b/src/cpp-utils/CMakeLists.txt
index c1f388a1..db4b168d 100644
--- a/src/cpp-utils/CMakeLists.txt
+++ b/src/cpp-utils/CMakeLists.txt
@@ -48,6 +48,7 @@ set(SOURCES
         system/time.cpp
 		system/diskspace.cpp
         value_type/ValueType.cpp
+        value_type/ConfigBuilder.cpp
 )
 
 add_library(${PROJECT_NAME} STATIC ${SOURCES})
diff --git a/src/cpp-utils/value_type/ConfigBuilder.cpp b/src/cpp-utils/value_type/ConfigBuilder.cpp
new file mode 100644
index 00000000..d538c561
--- /dev/null
+++ b/src/cpp-utils/value_type/ConfigBuilder.cpp
@@ -0,0 +1 @@
+#include "ConfigBuilder.h"
diff --git a/src/cpp-utils/value_type/ConfigBuilder.h b/src/cpp-utils/value_type/ConfigBuilder.h
new file mode 100644
index 00000000..d14f358f
--- /dev/null
+++ b/src/cpp-utils/value_type/ConfigBuilder.h
@@ -0,0 +1,61 @@
+#pragma once
+#ifndef MESSMER_CPPUTILS_VALUETYPE_CONFIGBUILDER_H_
+#define MESSMER_CPPUTILS_VALUETYPE_CONFIGBUILDER_H_
+
+namespace cpputils {
+
+template<class Config> class ValueType;
+
+template<class tag, class underlyingType, bool valueAccessEnabled, bool explicitValueConstructorEnabled, bool incrementAndDecrementEnabled>
+struct ValueTypeConfig final {
+private:
+    /*
+     * Accessors for building the ValueType<Config> class
+     */
+    friend class ValueType<ValueTypeConfig>;
+
+    using underlying_type = underlyingType;
+    static constexpr bool value_access_enabled() { return valueAccessEnabled; }
+    static constexpr bool explicit_value_constructor_enabled() { return explicitValueConstructorEnabled; }
+    static constexpr bool increment_and_decrement_enabled() { return incrementAndDecrementEnabled; }
+
+
+public:
+    /*
+     * Setters for builder pattern
+     */
+    constexpr ValueTypeConfig<tag, underlyingType, true, explicitValueConstructorEnabled, incrementAndDecrementEnabled>
+    enable_value_access() {
+        static_assert(!valueAccessEnabled, "Can't call enable_value_access() twice");
+        return {};
+    }
+
+    constexpr ValueTypeConfig<tag, underlyingType, valueAccessEnabled, true, incrementAndDecrementEnabled>
+    enable_explicit_value_constructor() {
+        static_assert(!explicitValueConstructorEnabled, "Can't call enable_explicit_value_constructor() twice");
+        return {};
+    }
+
+    constexpr ValueTypeConfig<tag, underlyingType, valueAccessEnabled, explicitValueConstructorEnabled, true>
+    enable_increment_and_decrement_operators() {
+        static_assert(!incrementAndDecrementEnabled, "Can't call enable_increment_and_decrement_operators twice");
+        return {};
+    };
+
+    using type = ValueType<ValueTypeConfig>;
+
+private:
+    constexpr ValueTypeConfig() {/* not meant for instantiation*/}
+};
+
+/**
+ * Start building a value type.
+ * tag: Some unique type to make sure the resulting value type is unique
+ * underlyingType: The type of the underlying values
+ */
+template<class tag, class underlyingType>
+inline constexpr ValueTypeConfig<tag, underlyingType, false, false, false> valueType() { return {}; }
+
+}
+
+#endif
diff --git a/src/cpp-utils/value_type/ValueType.cpp b/src/cpp-utils/value_type/ValueType.cpp
index fa166d0f..d0062732 100644
--- a/src/cpp-utils/value_type/ValueType.cpp
+++ b/src/cpp-utils/value_type/ValueType.cpp
@@ -1,4 +1 @@
-//
-// Created by heinzi on 21/05/18.
-//
-
+#include "ValueType.h"
diff --git a/src/cpp-utils/value_type/ValueType.h b/src/cpp-utils/value_type/ValueType.h
index 74e6e2b3..3644c177 100644
--- a/src/cpp-utils/value_type/ValueType.h
+++ b/src/cpp-utils/value_type/ValueType.h
@@ -1,29 +1,59 @@
 #pragma once
-#ifndef MESSMER_CPPUTILS_VALUETYPE_H_
-#define MESSMER_CPPUTILS_VALUETYPE_H_
+#ifndef MESSMER_CPPUTILS_VALUETYPE_VALUETYPE_H_
+#define MESSMER_CPPUTILS_VALUETYPE_VALUETYPE_H_
 
 #include <functional>
 #include <cpp-utils/assert/assert.h>
 
 namespace cpputils {
 
+namespace details {
+// The Helper type is to allow the enable_if to depend on another type, say a local template type of the method.
+// If enable_if depended only on class template parameters, it wouldn't work because they're already deduced when deducing the method.
+template<class Helper, bool Condition, class Type>
+using enable_if_t = std::enable_if_t<std::is_void<Helper>::value && Condition, Type>;
+}
+
 // TODO Test
 template<class Config>
 class ValueType final {
 public:
     using underlying_type = typename Config::underlying_type;
 
-    constexpr explicit ValueType(underlying_type value);
+    template<class U = void>
+    constexpr explicit ValueType(details::enable_if_t<U, Config::explicit_value_constructor_enabled(), underlying_type> value)
+    : _value(value) {}
 
-    template<class U = Config>
-    constexpr std::enable_if_t<sizeof(U) && Config::enable_value_access(), underlying_type> value() const {
+    template<class U = void>
+    constexpr details::enable_if_t<U, Config::value_access_enabled(), underlying_type> value() const {
         return _value;
-    };
+    }
 
-    constexpr ValueType& operator++();
-    constexpr ValueType operator++(int);
-    constexpr ValueType& operator--();
-    constexpr ValueType operator--(int);
+    template<class U = void>
+    constexpr details::enable_if_t<U, Config::increment_and_decrement_enabled(), ValueType&> operator++() {
+        ++_value;
+        return *this;
+    }
+
+    template<class U = void>
+    constexpr details::enable_if_t<U, Config::increment_and_decrement_enabled(), ValueType> operator++(int) {
+        ValueType<Config> tmp = *this;
+        ++(*this);
+        return tmp;
+    }
+
+    template<class U = void>
+    constexpr details::enable_if_t<U, Config::increment_and_decrement_enabled(), ValueType&> operator--() {
+        --_value;
+        return *this;
+    }
+
+    template<class U = void>
+    constexpr details::enable_if_t<U, Config::increment_and_decrement_enabled(), ValueType> operator--(int) {
+        ValueType<Config> tmp = *this;
+        --(*this);
+        return tmp;
+    }
 
     constexpr ValueType& operator+=(ValueType rhs);
     constexpr ValueType& operator-=(ValueType rhs);
@@ -65,35 +95,6 @@ inline constexpr ValueType<Config> operator "" _bytes(unsigned long long int val
     return ValueType<Config>(value);
 }*/
 
-template<class Config>
-inline constexpr ValueType<Config>::ValueType(typename Config::underlying_type value)
-        : _value(value) {}
-
-template<class Config>
-inline constexpr ValueType<Config>& ValueType<Config>::operator++() {
-    ++_value;
-    return *this;
-}
-
-template<class Config>
-inline constexpr ValueType<Config> ValueType<Config>::operator++(int) {
-    ValueType<Config> tmp = *this;
-    ++(*this);
-    return tmp;
-}
-
-template<class Config>
-inline constexpr ValueType<Config>& ValueType<Config>::operator--() {
-    --_value;
-    return *this;
-}
-
-template<class Config>
-inline constexpr ValueType<Config> ValueType<Config>::operator--(int) {
-    ValueType<Config> tmp = *this;
-    --(*this);
-    return tmp;
-}
 
 template<class Config>
 inline constexpr ValueType<Config>& ValueType<Config>::operator+=(ValueType<Config> rhs) {
diff --git a/test/cpp-utils/value_type/ValueTypeTest.cpp b/test/cpp-utils/value_type/ValueTypeTest.cpp
index a307e207..5ca60550 100644
--- a/test/cpp-utils/value_type/ValueTypeTest.cpp
+++ b/test/cpp-utils/value_type/ValueTypeTest.cpp
@@ -1,30 +1,50 @@
 #include <cpp-utils/value_type/ValueType.h>
+#include <cpp-utils/value_type/ConfigBuilder.h>
 #include <gtest/gtest.h>
+#include <utility>
 
-using cpputils::ValueType;
+using cpputils::valueType;
 
-class AllEnabledConfig final {
-    using underlying_type = int;
-    static constexpr bool allow_value_access() { return true; }
-};
+struct Tag1{};
+using AllEnabledValueType = decltype(valueType<Tag1, int>()
+    .enable_explicit_value_constructor()
+    .enable_value_access()
+)::type;
 
-using AllEnabledValueType = ValueType<AllEnabledConfig>;
+
+/*
+ * Test value() access
+ */
 
 template<class T, class Enable = void> struct has_value_access : std::false_type {};
-template<class T> struct has_value_access<T, std::void_t<T::value()>> : std::true_type {
-    static_assert(std::is_same<typename T::underlying_type, std::result_of_t<T::value()>>::value, "value() method returns wrong type");
+template<class T> struct has_value_access<T, std::void_t<decltype(std::declval<T>().value())>> : std::true_type {
+    using actual_result_type = std::result_of_t<decltype(&T::template value<void>)(T*)>;
+    static_assert(std::is_same<typename T::underlying_type, actual_result_type>::value, "value() method returns wrong type");
 };
 
-struct ConfigWithValueAccess final {
-    using underlying_type = int;
-    static constexpr bool allow_value_access() { return true; }
-};
+struct Tag2{};
+using ValueTypeWithValueAccess = decltype(valueType<Tag2, double>()
+    .enable_explicit_value_constructor()
+    .enable_value_access()
+)::type;
+struct Tag3{};
+using ValueTypeWithoutValueAccess = decltype(valueType<Tag3, double>()
+    .enable_explicit_value_constructor()
+)::type;
 
-struct ConfigWithoutValueAccess final {
-    using underlying_type = int;
-    static constexpr bool allow_value_access() { return false; }
-};
+static_assert(has_value_access<AllEnabledValueType>::value, "");
+static_assert(has_value_access<ValueTypeWithValueAccess>::value, "");
+static_assert(!has_value_access<ValueTypeWithoutValueAccess>::value, "");
 
-static_assert(has_value_access<ValueType<AllEnabledConfig>>::value, "");
-static_assert(has_value_access<ValueType<ConfigWithValueAccess>>::value, "");
-static_assert(!has_value_access<ValueType<ConfigWithoutValueAccess>>::value, "");
\ No newline at end of file
+TEST(ValueTypeTest, valueAccess){
+    EXPECT_EQ(3, AllEnabledValueType(3).value());
+    EXPECT_EQ(5.5, ValueTypeWithValueAccess(5.5).value());
+}
+
+struct Tag4{};
+using ValueTypeWithIncrementAndDecrement = decltype(valueType<Tag4, int>()
+    .enable_explicit_value_constructor()
+    .enable_value_access()
+    .enable_increment_and_decrement_operators()
+)::type;
+// TODO Test incrementAndDecrement
\ No newline at end of file