Introduce cmArgumentParser

3 files changed, 238 insertions, 0 deletions

diff --git a/Source/CMakeLists.txt b/Source/CMakeLists.txt
index 52f6742..a2836d6 100644
--- a/Source/CMakeLists.txt
+++ b/Source/CMakeLists.txt
@@ -143,6 +143,8 @@ set(SRCS
   cmAffinity.cxx
   cmAffinity.h
   cmArchiveWrite.cxx
+  cmArgumentParser.cxx
+  cmArgumentParser.h
   cmBase32.cxx
   cmCacheManager.cxx
   cmCacheManager.h
diff --git a/Source/cmArgumentParser.cxx b/Source/cmArgumentParser.cxx
new file mode 100644
index 0000000..9a9932c
--- /dev/null
+++ b/Source/cmArgumentParser.cxx
@@ -0,0 +1,93 @@
+/* Distributed under the OSI-approved BSD 3-Clause License.  See accompanying
+   file Copyright.txt or https://cmake.org/licensing for details.  */
+#include "cmArgumentParser.h"
+
+#include <algorithm>
+#include <type_traits>
+
+namespace ArgumentParser {
+
+auto ActionMap::Emplace(cm::string_view name, Action action)
+  -> std::pair<iterator, bool>
+{
+  auto const it =
+    std::lower_bound(this->begin(), this->end(), name,
+                     [](value_type const& elem, cm::string_view const& k) {
+                       return elem.first < k;
+                     });
+  return (it != this->end() && it->first == name)
+    ? std::make_pair(it, false)
+    : std::make_pair(this->emplace(it, name, std::move(action)), true);
+}
+
+auto ActionMap::Find(cm::string_view name) const -> const_iterator
+{
+  auto const it =
+    std::lower_bound(this->begin(), this->end(), name,
+                     [](value_type const& elem, cm::string_view const& k) {
+                       return elem.first < k;
+                     });
+  return (it != this->end() && it->first == name) ? it : this->end();
+}
+
+void Instance::Bind(bool& val)
+{
+  val = true;
+  this->CurrentString = nullptr;
+  this->CurrentList = nullptr;
+  this->ExpectValue = false;
+}
+
+void Instance::Bind(std::string& val)
+{
+  this->CurrentString = &val;
+  this->CurrentList = nullptr;
+  this->ExpectValue = true;
+}
+
+void Instance::Bind(StringList& val)
+{
+  this->CurrentString = nullptr;
+  this->CurrentList = &val;
+  this->ExpectValue = true;
+}
+
+void Instance::Bind(MultiStringList& val)
+{
+  this->CurrentString = nullptr;
+  this->CurrentList = (val.emplace_back(), &val.back());
+  this->ExpectValue = false;
+}
+
+void Instance::Consume(cm::string_view arg, void* result,
+                       std::vector<std::string>* unparsedArguments,
+                       std::vector<std::string>* keywordsMissingValue)
+{
+  auto const it = this->Bindings.Find(arg);
+  if (it != this->Bindings.end()) {
+    it->second(*this, result);
+    if (this->ExpectValue && keywordsMissingValue != nullptr) {
+      keywordsMissingValue->emplace_back(arg);
+    }
+    return;
+  }
+
+  if (this->CurrentString != nullptr) {
+    this->CurrentString->assign(std::string(arg));
+    this->CurrentString = nullptr;
+    this->CurrentList = nullptr;
+  } else if (this->CurrentList != nullptr) {
+    this->CurrentList->emplace_back(arg);
+  } else if (unparsedArguments != nullptr) {
+    unparsedArguments->emplace_back(arg);
+  }
+
+  if (this->ExpectValue) {
+    if (keywordsMissingValue != nullptr) {
+      keywordsMissingValue->pop_back();
+    }
+    this->ExpectValue = false;
+  }
+}
+
+} // namespace ArgumentParser
diff --git a/Source/cmArgumentParser.h b/Source/cmArgumentParser.h
new file mode 100644
index 0000000..6cfe946
--- /dev/null
+++ b/Source/cmArgumentParser.h
@@ -0,0 +1,143 @@
+/* Distributed under the OSI-approved BSD 3-Clause License.  See accompanying
+   file Copyright.txt or https://cmake.org/licensing for details.  */
+#ifndef cmArgumentParser_h
+#define cmArgumentParser_h
+
+#include "cmConfigure.h" // IWYU pragma: keep
+
+#include "cm_static_string_view.hxx"
+#include "cm_string_view.hxx"
+
+#include <cassert>
+#include <functional>
+#include <string>
+#include <utility>
+#include <vector>
+
+namespace ArgumentParser {
+
+using StringList = std::vector<std::string>;
+using MultiStringList = std::vector<StringList>;
+
+class Instance;
+using Action = std::function<void(Instance&, void*)>;
+
+// using ActionMap = cm::flat_map<cm::string_view, Action>;
+class ActionMap : public std::vector<std::pair<cm::string_view, Action>>
+{
+public:
+  std::pair<iterator, bool> Emplace(cm::string_view name, Action action);
+  const_iterator Find(cm::string_view name) const;
+};
+
+class Instance
+{
+public:
+  Instance(ActionMap const& bindings)
+    : Bindings(bindings)
+  {
+  }
+
+  void Bind(bool& val);
+  void Bind(std::string& val);
+  void Bind(StringList& val);
+  void Bind(MultiStringList& val);
+
+  void Consume(cm::string_view arg, void* result,
+               std::vector<std::string>* unparsedArguments,
+               std::vector<std::string>* keywordsMissingValue);
+
+private:
+  ActionMap const& Bindings;
+  std::string* CurrentString = nullptr;
+  StringList* CurrentList = nullptr;
+  bool ExpectValue = false;
+};
+
+} // namespace ArgumentParser
+
+template <typename Result>
+class cmArgumentParser
+{
+public:
+  // I *think* this function could be made `constexpr` when the code is
+  // compiled as C++20.  This would allow building a parser at compile time.
+  template <typename T>
+  cmArgumentParser& Bind(cm::static_string_view name, T Result::*member)
+  {
+    bool const inserted =
+      this->Bindings
+        .Emplace(name,
+                 [member](ArgumentParser::Instance& instance, void* result) {
+                   instance.Bind(static_cast<Result*>(result)->*member);
+                 })
+        .second;
+    assert(inserted), (void)inserted;
+    return *this;
+  }
+
+  template <typename Range>
+  void Parse(Result& result, Range const& args,
+             std::vector<std::string>* unparsedArguments = nullptr,
+             std::vector<std::string>* keywordsMissingValue = nullptr) const
+  {
+    ArgumentParser::Instance instance(this->Bindings);
+    for (cm::string_view arg : args) {
+      instance.Consume(arg, &result, unparsedArguments, keywordsMissingValue);
+    }
+  }
+
+  template <typename Range>
+  Result Parse(Range const& args,
+               std::vector<std::string>* unparsedArguments = nullptr,
+               std::vector<std::string>* keywordsMissingValue = nullptr) const
+  {
+    Result result;
+    this->Parse(result, args, unparsedArguments, keywordsMissingValue);
+    return result;
+  }
+
+private:
+  ArgumentParser::ActionMap Bindings;
+};
+
+template <>
+class cmArgumentParser<void>
+{
+public:
+  template <typename T>
+  cmArgumentParser& Bind(cm::static_string_view name, T& ref)
+  {
+    bool const inserted = this->Bind(cm::string_view(name), ref);
+    assert(inserted), (void)inserted;
+    return *this;
+  }
+
+  template <typename Range>
+  void Parse(Range const& args,
+             std::vector<std::string>* unparsedArguments = nullptr,
+             std::vector<std::string>* keywordsMissingValue = nullptr) const
+  {
+    ArgumentParser::Instance instance(this->Bindings);
+    for (cm::string_view arg : args) {
+      instance.Consume(arg, nullptr, unparsedArguments, keywordsMissingValue);
+    }
+  }
+
+protected:
+  template <typename T>
+  bool Bind(cm::string_view name, T& ref)
+  {
+    return this->Bindings
+      .Emplace(name,
+               [&ref](ArgumentParser::Instance& instance, void*) {
+                 instance.Bind(ref);
+               })
+      .second;
+  }
+
+private:
+  ArgumentParser::ActionMap Bindings;
+};
+
+#endif