// file      : build2/prerequisite -*- C++ -*-
// copyright : Copyright (c) 2014-2016 Code Synthesis Ltd
// license   : MIT; see accompanying LICENSE file

#ifndef BUILD2_PREREQUISITE
#define BUILD2_PREREQUISITE

#include <functional> // hash
#include <unordered_set>

#include <build2/types>
#include <build2/utility>

#include <build2/target-key>
#include <build2/diagnostics>

namespace build2
{
  class scope;
  class target;

  // Light-weight (by being shallow-pointing) prerequisite key, similar
  // to (and based on) target key.
  //
  class prerequisite_key
  {
  public:
    typedef build2::scope scope_type;

    mutable const string* proj; // Can be NULL, from project_name_pool.
    target_key tk;              // .dir and .out can be relative.
    mutable scope_type* scope;  // Can be NULL if tk.dir is absolute.

    template <typename T>
    bool is_a () const {return tk.is_a<T> ();}
    bool is_a (const target_type& tt) const {return tk.is_a (tt);}
  };

  inline bool
  operator== (const prerequisite_key& x, const prerequisite_key& y)
  {
    assert (x.scope == y.scope);

    // Can compare project name pointers since they are from project_name_pool.
    //
    return x.proj == y.proj && x.tk == y.tk;
  }

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

  ostream&
  operator<< (ostream&, const prerequisite_key&);
}


namespace std
{
  // Note that we ignore the extension when calculating the hash because of
  // its special "unspecified" logic (see target_key::operator==).
  //
  template <>
  struct hash<build2::prerequisite_key>
  {
    using argument_type = build2::prerequisite_key;
    using result_type = size_t;

    size_t
    operator() (const build2::prerequisite_key& k) const noexcept
    {
      // Can hash project name pointers since they are from project_name_pool.
      //
      return build2::combine_hash (hash<const string*> () (k.proj),
                                   hash<build2::target_key> () (k.tk));
    }
  };
}

namespace build2
{
  class prerequisite
  {
  public:
    typedef build2::target target_type;
    typedef build2::target_type target_type_type;
    typedef build2::scope scope_type;

    // Note that unlike targets, for prerequisites an empty out directory
    // means undetermined rather than being definitely in the out tree.
    //
    const string* const proj; // NULL if not project-qualified.
    const target_type_type& type;
    const dir_path dir;      // Normalized absolute or relative (to scope).
    const dir_path out;      // Empty, normalized absolute, or relative.
    const string name;
    const string* ext;       // NULL if unspecified.
    scope_type& scope;
    target_type* target;     // NULL if not yet resolved. Note that this should
                             // always be the "primary target", not a member of
                             // a target group.

  public:
    prerequisite (const string* p,
                  const target_type_type& t,
                  dir_path d,
                  dir_path o,
                  string n,
                  const string* e,
                  scope_type& s)
        : proj (p),
          type (t),
          dir (move (d)),
          out (move (o)),
          name (move (n)),
          ext (e),
          scope (s),
          target (nullptr) {}

    // Note that the returned key "tracks" the prerequisite; that is, any
    // updates to the prerequisite's members will be reflected in the key.
    //
    prerequisite_key
    key () const
    {
      return prerequisite_key {proj, {&type, &dir, &out, &name, ext}, &scope};
    }

  public:
    // Prerequisite (target) type.
    //
    template <typename T>
    bool
    is_a () const {return type.is_a<T> ();}

    bool
    is_a (const target_type_type& tt) const {return type.is_a (tt);}
  };

  inline bool
  operator== (const prerequisite& x, const prerequisite& y)
  {
    return x.key () == y.key ();
  }

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

  inline ostream&
  operator<< (ostream& os, const prerequisite& p)
  {
    return os << p.key ();
  }

}

namespace std
{
  template <>
  struct hash<build2::prerequisite>
  {
    using argument_type = build2::prerequisite;
    using result_type = size_t;

    size_t
    operator() (const build2::prerequisite& p) const noexcept
    {
      return hash<build2::prerequisite_key> () (p.key ());
    }
  };
}

namespace build2
{
  // Set of prerequisites in a scope.
  //
  // Similar to targets, specified and unspecified extensions are considered
  // equal and we may update the extension in the existing entry. To make
  // this work we use a hash set.
  //
  struct prerequisite_set: std::unordered_set<prerequisite>
  {
    pair<prerequisite&, bool>
    insert (const string* proj,
            const target_type&,
            dir_path dir,
            dir_path out,
            string name,
            const string* ext,
            scope&,
            tracer&);

    pair<prerequisite&, bool>
    insert (const string* proj, const target_key& tk, scope& s, tracer& t)
    {
      return insert (proj, *tk.type, *tk.dir, *tk.out, *tk.name, tk.ext, s, t);
    }
  };
}

#endif // BUILD2_PREREQUISITE