cpp-case-matcher/match.hpp

//
//  match.hpp
//  case-matcher
//
//  Created by Sam Jaffe on 9/10/16.
//

#pragma once

#include <array>
#include <tuple>

namespace matcher {
  struct {} any;
  using any_t = decltype(any);
  
  template <typename T>
  bool operator==(T const &, any_t) { return true; }
}

namespace matcher {
  template <typename T, size_t I>
  struct any_of_t {
    std::array<T, I> options;
  };
  
  template <typename T, size_t I>
  bool operator==(T const & t, any_of_t<T, I> const & of) {
    return std::find(of.options.begin(), of.options.end(), t) != of.options.end();
  }
  
  template <typename... Args>
  any_of_t<typename std::common_type<Args...>::type, sizeof...(Args)> any_of(Args &&... args) {
    return {{args...}};
  }
}

namespace matcher {
  template <typename... Args>
  struct matcher {
  public:
    matcher(Args &&... args) : value(std::forward<Args>(args)...) {}
    
    operator bool( ) const { return true; }
    bool unmatched( ) const { return ! satisfied; }
    
    template <typename... NArgs>
    bool matches(NArgs &&... args) const {
      bool const matched = value == std::make_tuple(std::forward<NArgs>(args)...);
      satisfied |= matched;
      return matched;
    }
  private:
    std::tuple<Args...> value;
    mutable bool satisfied = false;
  };
  
  template <typename... Args>
  matcher<Args...> make_matcher(Args &&... args) {
    return matcher<Args...>(std::forward<Args>(args)...);
  }
}

#define match( ... ) \
  if ( auto const & _matcher_local = \
      ::matcher::make_matcher( __VA_ARGS__ ) )

#define with( ... ) \
  if ( _matcher_local.unmatched( ) && \
      _matcher_local.matches( __VA_ARGS__ ) )

#define else_with( ... ) \
  else if ( _matcher_local.matches( __VA_ARGS__ ) )

#define and_with( ... ) \
  if ( _matcher_local.matches( __VA_ARGS__ ) )

#define nomatch( ) \
  if ( _matcher_local.unmatched( ) )