#ifndef SASS_EXTENSION_H

#define SASS_EXTENSION_H

// sass.hpp must go before all system headers to get the

// __EXTENSIONS__ fix on Solaris.

#include "sass.hpp"

#include <unordered_map>

#include <unordered_set>

#include "ast_fwd_decl.hpp"

#include "backtrace.hpp"

namespace Sass {

  class Extension {

  public:

    // The selector in which the `@extend` appeared.

    ComplexSelectorObj extender;

    // The selector that's being extended.

    // `null` for one-off extensions.

    SimpleSelectorObj target;

    // The minimum specificity required for any

    // selector generated from this extender.

    size_t specificity;

    // Whether this extension is optional.

    bool isOptional;

    // Whether this is a one-off extender representing a selector that was

    // originally in the document, rather than one defined with `@extend`.

    bool isOriginal;

    bool isSatisfied;

    // The media query context to which this extend is restricted,

    // or `null` if it can apply within any context.

    CssMediaRuleObj mediaContext;

    // Creates a one-off extension that's not intended to be modified over time.

    // If [specificity] isn't passed, it defaults to `extender.maxSpecificity`.

    Extension(ComplexSelectorObj extender) :

      extender(extender),

      target({}),

      specificity(0),

      isOptional(true),

      isOriginal(false),

      isSatisfied(false),

      mediaContext({}) {

    }

    // Copy constructor

    Extension(const Extension& extension) :

      extender(extension.extender),

      target(extension.target),

      specificity(extension.specificity),

      isOptional(extension.isOptional),

      isOriginal(extension.isOriginal),

      isSatisfied(extension.isSatisfied),

      mediaContext(extension.mediaContext) {

    }

    // Default constructor

    Extension() :

      extender({}),

      target({}),

      specificity(0),

      isOptional(false),

      isOriginal(false),

      isSatisfied(false),

      mediaContext({}) {

    }

    // Asserts that the [mediaContext] for a selector is 

    // compatible with the query context for this extender.

    void assertCompatibleMediaContext(CssMediaRuleObj mediaContext, Backtraces& traces) const;

    Extension withExtender(const ComplexSelectorObj& newExtender) const;

  };

}

#endif