// file      : libbuild2/target-type.hxx -*- C++ -*-
// copyright : Copyright (c) 2014-2019 Code Synthesis Ltd
// license   : MIT; see accompanying LICENSE file

#ifndef LIBBUILD2_TARGET_TYPE_HXX
#define LIBBUILD2_TARGET_TYPE_HXX

#include <map>

#include <libbuild2/types.hxx>
#include <libbuild2/utility.hxx>

#include <libbuild2/export.hxx>

namespace build2
{
  class scope;
  class target;
  class target_key;
  class prerequisite_key;

  // Target type.
  //
  // Note that we assume there is always a single instance of this class for
  // any target type. As a result, we can use address comparison to determine
  // if two target types are the same.
  //
  // If the extension derivation functions are NULL, then it means this target
  // type does not use extensions. Note that this is relied upon when deciding
  // whether to print the extension.
  //
  // The fixed extension function should return the fixed extension (which can
  // point to the key's ext member; note that for performance reasons we
  // currently only verify the explicitly specified extension on target
  // insersion -- see target_key comparison for details).
  //
  // The root scope argument to the fixed extension function may be NULL which
  // means the root scope is not known. A target type that relies on this must
  // be prepared to resolve the root scope itself and handle the cases where
  // the target is not (yet) in any project (this is currently only used to
  // handle the alternative build file/directory naming scheme and hopefully
  // it will stay that way).
  //
  // The default extension is used in two key (there are others) places:
  // search_existing_file() (called for a prerequisite with the last argument
  // true) and in target::derive_extension() (called for a target with the
  // last argument false); see their respective implementations for details.
  // The third argument is the default extension that is supplied (e.g., by a
  // rule) to derive_extension(), if any. The implementation can decide which
  // takes precedence, etc (see the exe{} target type for some interesting
  // logic). If the default extension function returns NULL, then it means the
  // default extension for this target could not be derived.
  //
  // If the pattern function is not NULL, then it is used to amend a pattern
  // or match (reverse is false) and then, if the amendment call returned
  // true, to reverse it in the resulting matches. The pattern function for a
  // non-directory target must first call target::split_name() if reverse is
  // false.
  //
  struct LIBBUILD2_SYMEXPORT target_type
  {
    const char* name;
    const target_type* base;

    target* (*factory) (const target_type&, dir_path, dir_path, string);

    const char*      (*fixed_extension)   (const target_key&,
                                           const scope* root);
    optional<string> (*default_extension) (const target_key&,
                                           const scope& base,
                                           const char*,
                                           bool search);

    bool (*pattern) (const target_type&,
                     const scope& base,
                     string& name,
                     optional<string>& extension,
                     const location&,
                     bool reverse);

    void (*print) (ostream&, const target_key&);

    const target* (*search) (const target&, const prerequisite_key&);

    bool see_through; // A group with the default "see through" semantics.

    template <typename T>
    bool
    is_a () const {return is_a (T::static_type);}

    bool
    is_a (const target_type& tt) const
    {
      return this == &tt || (base != nullptr && is_a_base (tt));
    }

    bool
    is_a_base (const target_type&) const; // Defined in target.cxx
  };

  inline bool
  operator< (const target_type& x, const target_type& y) {return &x < &y;}

  inline bool
  operator== (const target_type& x, const target_type& y) {return &x == &y;}

  inline bool
  operator!= (const target_type& x, const target_type& y) {return &x != &y;}

  inline ostream&
  operator<< (ostream& os, const target_type& tt) {return os << tt.name;}

  // Target type map.
  //
  class target_type_map
  {
  public:
    // Target type name to target type mapping.
    //
    const target_type*
    find (const string& n) const
    {
      auto i (type_map_.find (n));
      return i != type_map_.end () ? &i->second.get () : nullptr;
    }

    bool
    empty () const
    {
      return type_map_.empty ();
    }

    const target_type&
    insert (const target_type& tt)
    {
      type_map_.emplace (tt.name, target_type_ref (tt));
      return tt;
    }

    template <typename T>
    const target_type&
    insert ()
    {
      return insert (T::static_type);
    }

    pair<reference_wrapper<const target_type>, bool>
    insert (const string& n, unique_ptr<target_type>&& tt)
    {
      target_type& rtt (*tt); // Save a non-const reference to the object.

      auto p (type_map_.emplace (n, target_type_ref (move (tt))));

      // Patch the alias name to use the map's key storage.
      //
      if (p.second)
        rtt.name = p.first->first.c_str ();

      return pair<reference_wrapper<const target_type>, bool> (
        p.first->second.get (), p.second);
    }

    // File name to target type mapping.
    //
    const target_type*
    find_file (const string& n) const
    {
      auto i (file_map_.find (n));
      return i != file_map_.end () ? &i->second.get () : nullptr;
    }

    void
    insert_file (const string& n, const target_type& tt)
    {
      file_map_.emplace (n, tt);
    }

  private:
    struct target_type_ref
    {
      // Like reference_wrapper except it sometimes deletes the target type.
      //
      explicit
      target_type_ref (const target_type& r): p_ (&r), d_ (false) {}

      explicit
      target_type_ref (unique_ptr<target_type>&& p)
          : p_ (p.release ()), d_ (true) {}

      target_type_ref (target_type_ref&& r)
          : p_ (r.p_), d_ (r.d_) {r.p_ = nullptr;}

      ~target_type_ref () {if (p_ != nullptr && d_) delete p_;}

      explicit operator const target_type& () const {return *p_;}
      const target_type& get () const {return *p_;}

    private:
      const target_type* p_;
      bool d_;
    };

    std::map<string, target_type_ref> type_map_;
    std::map<string, reference_wrapper<const target_type>> file_map_;
  };
}

#endif // LIBBUILD2_TARGET_TYPE_HXX