context.hh

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#pragma once

#include <memory>
#include <string>

#include <vcsn/ctx/fwd.hh> // vcsn::context
#include <vcsn/dyn/cast.hh>
#include <vcsn/misc/export.hh>
#include <vcsn/misc/symbol.hh>

namespace vcsn
{
  namespace dyn
  {
    class LIBVCSN_API context
    {
    public:
      context()
        : self_(nullptr)
      {}

      template <typename LabelSet, typename WeightSet>
      context(const vcsn::context<LabelSet, WeightSet>& ctx)
        : self_(std::make_shared<model<vcsn::context<LabelSet, WeightSet>>>(ctx))
      {}

      symbol vname() const
      {
        return self_->vname();
      }

      template <typename Ctx>
      auto& as()
      {
        return detail::dyn_cast<model<Ctx>&>(*self_).context();
      }

      template <typename Ctx>
      auto& as() const
      {
        return detail::dyn_cast<const model<Ctx>&>(*self_).context();
      }

      const auto* operator->() const
      {
        return this;
      }

      operator bool() const
      {
        return bool(self_);
      }

    private:
      struct base
      {
        virtual ~base() = default;
        virtual symbol vname() const = 0;
      };

      template <typename Context>
      struct model final : base
      {
        using context_t = Context;

        model(context_t ctx)
          : context_(std::move(ctx))
        {}

        symbol vname() const
        {
          return context().sname();
        }

        const auto& context() const
        {
          return context_;
        }

        const context_t context_;
      };

      std::shared_ptr<base> self_;
    };
  }
}