From 426a5dbb765023e9a51aafd84d6929a500266669 Mon Sep 17 00:00:00 2001
From: Zhihao Yuan <lichray@gmail.com>
Date: Mon, 25 Nov 2019 18:44:04 -0600
Subject: [PATCH] Parse integers in the .scan fluent interface

---
 include/argparse.hpp | 137 ++++++++++++++++++++++++++++++++++
 test/CMakeLists.txt  |   1 +
 test/test_scan.cpp   | 173 +++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 311 insertions(+)
 create mode 100644 test/test_scan.cpp

diff --git a/include/argparse.hpp b/include/argparse.hpp
index 6ce6f83..b5ef1ed 100644
--- a/include/argparse.hpp
+++ b/include/argparse.hpp
@@ -77,6 +77,25 @@ struct is_string_like
     : std::conjunction<std::is_constructible<std::string, T>,
                        std::is_convertible<T, std::string_view>> {};
 
+template <typename T> constexpr bool standard_signed_integer = false;
+template <> constexpr bool standard_signed_integer<signed char> = true;
+template <> constexpr bool standard_signed_integer<short int> = true;
+template <> constexpr bool standard_signed_integer<int> = true;
+template <> constexpr bool standard_signed_integer<long int> = true;
+template <> constexpr bool standard_signed_integer<long long int> = true;
+
+template <typename T> constexpr bool standard_unsigned_integer = false;
+template <> constexpr bool standard_unsigned_integer<unsigned char> = true;
+template <> constexpr bool standard_unsigned_integer<unsigned short int> = true;
+template <> constexpr bool standard_unsigned_integer<unsigned int> = true;
+template <> constexpr bool standard_unsigned_integer<unsigned long int> = true;
+template <>
+constexpr bool standard_unsigned_integer<unsigned long long int> = true;
+
+template <typename T>
+constexpr bool standard_integer =
+    standard_signed_integer<T> || standard_unsigned_integer<T>;
+
 template <class F, class Tuple, class Extra, size_t... I>
 constexpr decltype(auto) apply_plus_one_impl(F &&f, Tuple &&t, Extra &&x,
                                              std::index_sequence<I...>) {
@@ -92,6 +111,85 @@ constexpr decltype(auto) apply_plus_one(F &&f, Tuple &&t, Extra &&x) {
           std::tuple_size_v<std::remove_reference_t<Tuple>>>{});
 }
 
+constexpr auto pointer_range(std::string_view s) noexcept {
+  return std::tuple(s.data(), s.data() + s.size());
+}
+
+template <class CharT, class Traits>
+constexpr bool starts_with(std::basic_string_view<CharT, Traits> prefix,
+                           std::basic_string_view<CharT, Traits> s) noexcept {
+  return s.substr(0, prefix.size()) == prefix;
+}
+
+enum class chars_format {
+  scientific = 0x1,
+  fixed = 0x2,
+  hex = 0x4,
+  general = fixed | scientific
+};
+
+struct consume_hex_prefix_result {
+  bool is_hexadecimal;
+  std::string_view rest;
+};
+
+using namespace std::literals;
+
+constexpr auto consume_hex_prefix(std::string_view s)
+    -> consume_hex_prefix_result {
+  if (starts_with("0x"sv, s) || starts_with("0X"sv, s)) {
+    s.remove_prefix(2);
+    return {true, s};
+  } else {
+    return {false, s};
+  }
+}
+
+template <class T, auto Param>
+inline auto do_from_chars(std::string_view s) -> T {
+  T x;
+  auto [first, last] = pointer_range(s);
+  auto [ptr, ec] = std::from_chars(first, last, x, Param);
+  if (ec == std::errc()) {
+    if (ptr == last)
+      return x;
+    else
+      throw std::invalid_argument{"pattern does not match to the end"};
+  } else if (ec == std::errc::invalid_argument) {
+    throw std::invalid_argument{"pattern not found"};
+  } else if (ec == std::errc::result_out_of_range) {
+    throw std::range_error{"not representable"};
+  } else {
+    return x; // unreachable
+  }
+}
+
+template <class T, auto Param = 0> struct parse_number {
+  auto operator()(std::string_view s) -> T {
+    return do_from_chars<T, Param>(s);
+  }
+};
+
+template <class T> struct parse_number<T, 16> {
+  auto operator()(std::string_view s) -> T {
+    if (auto [ok, rest] = consume_hex_prefix(s); ok)
+      return do_from_chars<T, 16>(rest);
+    else
+      throw std::invalid_argument{"pattern not found"};
+  }
+};
+
+template <class T> struct parse_number<T> {
+  auto operator()(std::string_view s) -> T {
+    if (auto [ok, rest] = consume_hex_prefix(s); ok)
+      return do_from_chars<T, 16>(rest);
+    else if (starts_with("0"sv, s))
+      return do_from_chars<T, 8>(rest);
+    else
+      return do_from_chars<T, 10>(rest);
+  }
+};
+
 } // namespace details
 
 class ArgumentParser;
@@ -162,6 +260,45 @@ public:
     return *this;
   }
 
+  template <char Shape, typename T>
+  auto scan() -> std::enable_if_t<std::is_arithmetic_v<T>, Argument &> {
+    static_assert(!(std::is_const_v<T> || std::is_volatile_v<T>),
+                  "T should not be cv-qualified");
+    auto is_one_of = [](char c, auto... x) constexpr {
+      return ((c == x) || ...);
+    };
+
+    if constexpr (is_one_of(Shape, 'd') && details::standard_integer<T>)
+      action(details::parse_number<T, 10>());
+    else if constexpr (is_one_of(Shape, 'i') && details::standard_integer<T>)
+      action(details::parse_number<T>());
+    else if constexpr (is_one_of(Shape, 'u') &&
+                       details::standard_unsigned_integer<T>)
+      action(details::parse_number<T, 10>());
+    else if constexpr (is_one_of(Shape, 'o') &&
+                       details::standard_unsigned_integer<T>)
+      action(details::parse_number<T, 8>());
+    else if constexpr (is_one_of(Shape, 'x', 'X') &&
+                       details::standard_unsigned_integer<T>)
+      action(details::parse_number<T, 16>());
+    else if constexpr (is_one_of(Shape, 'a', 'A') &&
+                       std::is_floating_point_v<T>)
+      action(details::parse_number<T, details::chars_format::hex>());
+    else if constexpr (is_one_of(Shape, 'e', 'E') &&
+                       std::is_floating_point_v<T>)
+      action(details::parse_number<T, details::chars_format::scientific>());
+    else if constexpr (is_one_of(Shape, 'f', 'F') &&
+                       std::is_floating_point_v<T>)
+      action(details::parse_number<T, details::chars_format::fixed>());
+    else if constexpr (is_one_of(Shape, 'g', 'G') &&
+                       std::is_floating_point_v<T>)
+      action(details::parse_number<T, details::chars_format::general>());
+    else
+      static_assert(alignof(T) == 0, "No scan specification for T");
+
+    return *this;
+  }
+
   Argument &nargs(int aNumArgs) {
     if (aNumArgs < 0)
       throw std::logic_error("Number of arguments must be non-negative");
diff --git a/test/CMakeLists.txt b/test/CMakeLists.txt
index 72aa695..a1f4c82 100644
--- a/test/CMakeLists.txt
+++ b/test/CMakeLists.txt
@@ -37,6 +37,7 @@ file(GLOB ARGPARSE_TEST_SOURCES
     test_parse_args.cpp
     test_positional_arguments.cpp
     test_required_arguments.cpp
+    test_scan.cpp
     test_value_semantics.cpp
 )
 set_source_files_properties(main.cpp
diff --git a/test/test_scan.cpp b/test/test_scan.cpp
new file mode 100644
index 0000000..c55e5a8
--- /dev/null
+++ b/test/test_scan.cpp
@@ -0,0 +1,173 @@
+#include <argparse.hpp>
+#include <doctest.hpp>
+#include <stdint.h>
+
+using doctest::test_suite;
+
+TEST_CASE_TEMPLATE("Parse a decimal integer argument" * test_suite("scan"), T,
+                   int8_t, int16_t, int32_t, int64_t, uint8_t, uint16_t,
+                   uint32_t, uint64_t) {
+  argparse::ArgumentParser program("test");
+  program.add_argument("-n").scan<'d', T>();
+
+  SUBCASE("zero") {
+    program.parse_args({"test", "-n", "0"});
+    REQUIRE(program.get<T>("-n") == 0);
+  }
+
+  SUBCASE("non-negative") {
+    program.parse_args({"test", "-n", "5"});
+    REQUIRE(program.get<T>("-n") == 5);
+  }
+
+  SUBCASE("negative") {
+    if constexpr (std::is_signed_v<T>) {
+      program.parse_args({"test", "-n", "-128"});
+      REQUIRE(program.get<T>("-n") == -128);
+    } else {
+      REQUIRE_THROWS_AS(program.parse_args({"test", "-n", "-135"}),
+                        std::invalid_argument);
+    }
+  }
+
+  SUBCASE("left-padding is not allowed") {
+    REQUIRE_THROWS_AS(program.parse_args({"test", "-n", " 32"}),
+                      std::invalid_argument);
+  }
+
+  SUBCASE("right-padding is not allowed") {
+    REQUIRE_THROWS_AS(program.parse_args({"test", "-n", "12 "}),
+                      std::invalid_argument);
+  }
+
+  SUBCASE("plus sign is not allowed") {
+    REQUIRE_THROWS_AS(program.parse_args({"test", "-n", "+12"}),
+                      std::invalid_argument);
+  }
+
+  SUBCASE("does not fit") {
+    REQUIRE_THROWS_AS(
+        program.parse_args({"test", "-n", "987654321987654321987654321"}),
+        std::range_error);
+  }
+}
+
+TEST_CASE_TEMPLATE("Parse an octal integer argument" * test_suite("scan"), T,
+                   uint8_t, uint16_t, uint32_t, uint64_t) {
+  argparse::ArgumentParser program("test");
+  program.add_argument("-n").scan<'o', T>();
+
+  SUBCASE("zero") {
+    program.parse_args({"test", "-n", "0"});
+    REQUIRE(program.get<T>("-n") == 0);
+  }
+
+  SUBCASE("with octal base") {
+    program.parse_args({"test", "-n", "066"});
+    REQUIRE(program.get<T>("-n") == 066);
+  }
+
+  SUBCASE("minus sign produces an optional argument") {
+    REQUIRE_THROWS_AS(program.parse_args({"test", "-n", "-003"}),
+                      std::runtime_error);
+  }
+
+  SUBCASE("plus sign is not allowed") {
+    REQUIRE_THROWS_AS(program.parse_args({"test", "-n", "+012"}),
+                      std::invalid_argument);
+  }
+
+  SUBCASE("does not fit") {
+    REQUIRE_THROWS_AS(
+        program.parse_args({"test", "-n", "02000000000000000000001"}),
+        std::range_error);
+  }
+}
+
+TEST_CASE_TEMPLATE("Parse a hexadecimal integer argument" * test_suite("scan"),
+                   T, uint8_t, uint16_t, uint32_t, uint64_t) {
+  argparse::ArgumentParser program("test");
+  program.add_argument("-n").scan<'X', T>();
+
+  SUBCASE("with hex digit") {
+    program.parse_args({"test", "-n", "0x1a"});
+    REQUIRE(program.get<T>("-n") == 0x1a);
+  }
+
+  SUBCASE("minus sign produces an optional argument") {
+    REQUIRE_THROWS_AS(program.parse_args({"test", "-n", "-0x1"}),
+                      std::runtime_error);
+  }
+
+  SUBCASE("plus sign is not allowed") {
+    REQUIRE_THROWS_AS(program.parse_args({"test", "-n", "+0x1a"}),
+                      std::invalid_argument);
+  }
+
+  SUBCASE("does not fit") {
+    REQUIRE_THROWS_AS(program.parse_args({"test", "-n", "0XFFFFFFFFFFFFFFFF1"}),
+                      std::range_error);
+  }
+}
+
+TEST_CASE_TEMPLATE("Parse integer argument of any format" * test_suite("scan"),
+                   T, int8_t, int16_t, int32_t, int64_t, uint8_t, uint16_t,
+                   uint32_t, uint64_t) {
+  argparse::ArgumentParser program("test");
+  program.add_argument("-n").scan<'i', T>();
+
+  SUBCASE("zero") {
+    program.parse_args({"test", "-n", "0"});
+    REQUIRE(program.get<T>("-n") == 0);
+  }
+
+  SUBCASE("octal") {
+    program.parse_args({"test", "-n", "077"});
+    REQUIRE(program.get<T>("-n") == 077);
+  }
+
+  SUBCASE("no negative octal") {
+    REQUIRE_THROWS_AS(program.parse_args({"test", "-n", "-0777"}),
+                      std::runtime_error);
+  }
+
+  SUBCASE("hex") {
+    program.parse_args({"test", "-n", "0X2c"});
+    REQUIRE(program.get<T>("-n") == 0X2c);
+  }
+
+  SUBCASE("no negative hex") {
+    REQUIRE_THROWS_AS(program.parse_args({"test", "-n", "-0X2A"}),
+                      std::runtime_error);
+  }
+
+  SUBCASE("decimal") {
+    program.parse_args({"test", "-n", "98"});
+    REQUIRE(program.get<T>("-n") == 98);
+  }
+
+  SUBCASE("negative decimal") {
+    if constexpr (std::is_signed_v<T>) {
+      program.parse_args({"test", "-n", "-39"});
+      REQUIRE(program.get<T>("-n") == -39);
+    } else {
+      REQUIRE_THROWS_AS(program.parse_args({"test", "-n", "-39"}),
+                        std::invalid_argument);
+    }
+  }
+
+  SUBCASE("left-padding is not allowed") {
+    REQUIRE_THROWS_AS(program.parse_args({"test", "-n", "\t32"}),
+                      std::invalid_argument);
+  }
+
+  SUBCASE("right-padding is not allowed") {
+    REQUIRE_THROWS_AS(program.parse_args({"test", "-n", "32\n"}),
+                      std::invalid_argument);
+  }
+
+  SUBCASE("plus sign is not allowed") {
+    REQUIRE_THROWS_AS(program.parse_args({"test", "-n", "+670"}),
+                      std::invalid_argument);
+  }
+}