// file      : build2/rule -*- C++ -*-
// copyright : Copyright (c) 2014-2017 Code Synthesis Ltd
// license   : MIT; see accompanying LICENSE file

#ifndef BUILD2_RULE
#define BUILD2_RULE

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

#include <build2/target>
#include <build2/operation>

namespace build2
{
  class match_result
  {
  public:
    bool result;
    action recipe_action = action (); // Used as recipe's action if set.

    explicit
    operator bool () const {return result;}

    // Note that the from-bool constructor is intentionally implicit so that
    // we can return true/false from match().
    //
    match_result (bool r): result (r) {}
    match_result (bool r, action a): result (r), recipe_action (a) {}
  };

  // Once a rule is registered (for a scope), it is treated as immutable. If
  // you need to modify some state (e.g., counters or some such), then make
  // sure it is MT-safe.
  //
  class rule
  {
  public:
    virtual match_result
    match (slock&, action, target&, const string& hint) const = 0;

    virtual recipe
    apply (slock&, action, target&) const = 0;
  };

  // Fallback rule that only matches if the file exists.
  //
  class file_rule: public rule
  {
  public:
    file_rule () {}

    virtual match_result
    match (slock&, action, target&, const string&) const override;

    virtual recipe
    apply (slock&, action, target&) const override;

    static const file_rule instance;
  };

  class alias_rule: public rule
  {
  public:
    alias_rule () {}

    virtual match_result
    match (slock&, action, target&, const string&) const override;

    virtual recipe
    apply (slock&, action, target&) const override;

    static const alias_rule instance;
  };

  class fsdir_rule: public rule
  {
  public:
    fsdir_rule () {}

    virtual match_result
    match (slock&, action, target&, const string&) const override;

    virtual recipe
    apply (slock&, action, target&) const override;

    static target_state
    perform_update (action, const target&);

    static target_state
    perform_clean (action, const target&);

    static const fsdir_rule instance;
  };

  // Fallback rule that always matches and does nothing.
  //
  class fallback_rule: public build2::rule
  {
  public:
    fallback_rule () {}

    virtual match_result
    match (slock&, action, target&, const string&) const override
    {
      return true;
    }

    virtual recipe
    apply (slock&, action, target&) const override {return noop_recipe;}

    static const fallback_rule instance;
  };
}

#endif // BUILD2_RULE