filter.hpp

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/*
   Copyright (C) 2014 - 2016 by Chris Beck <[email protected]>
   Part of the Battle for Wesnoth Project http://www.wesnoth.org/

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 2 of the License, or
   (at your option) any later version.
   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY.

   See the COPYING file for more details.
*/

/**
 * This namespace contains the function that checks if a unit matches
 * a filter. It helps by simplifying the unit object (which before now
 * holds the "match" function).
 *
 * TODO:
 * Make a class that abstracts a unit filter, assembles the constituent
 * side filters and terrain filters and conditional filters, and caches
 * these to speed up repeated application of the filter.
 */

#ifndef INCLUDED_UNIT_FILTER_HPP_
#define INCLUDED_UNIT_FILTER_HPP_

#include "units/ptr.hpp"

#include <boost/shared_ptr.hpp>
#include <vector>

class filter_context;
class unit;
class config;
class vconfig;
struct map_location;

class unit_filter_abstract_impl {
public:
    virtual bool matches(const unit & u, const map_location & loc, const unit * u2 = nullptr) const = 0;
    virtual std::vector<const unit*> all_matches_on_map(unsigned max_matches) const = 0;
    virtual unit_const_ptr first_match_on_map() const = 0;
    virtual config to_config() const = 0;
    virtual bool empty() const {return false;}
    virtual ~unit_filter_abstract_impl() {}
};

class unit_filter {
public:
    unit_filter(const vconfig & cfg, const filter_context * fc, bool use_flat_tod = false); //!< Constructs a unit filter from a config and a context. This function should give the most efficient implementation available.

    // Copy and Swap Idiom for the interface -- does not copy the underlying impl
    unit_filter(const unit_filter & o ) : impl_(o.impl_) {}
    void swap(unit_filter & o) {
        impl_.swap(o.impl_);
    }
    unit_filter & operator=(unit_filter o) {
        swap(o);
        return *this;
    }

    /// Determine if *this matches @a filter at a specified location.
    /// Use this for units on a recall list, or to test for a match if
    /// a unit is hypothetically moved.
    bool matches(const unit & u, const map_location & loc) const {
        return impl_->matches(u,loc);
    }
    /// Determine if *this matches @a filter at its current location.
    /// (Only use for units currently on the map; otherwise use the overload
    /// that takes a location, possibly with a null location.)
    bool matches(const unit & u) const;

    bool matches(const unit & u, const map_location & loc, const unit & u2) const;
    bool matches(const unit & u, const unit & u2) const;

    bool operator()(const unit & u, const map_location & loc) const {
        return matches(u,loc);
    }

    bool operator()(const unit & u) const {
        return matches(u);
    }

    bool operator()(const unit & u, const map_location & loc, const unit & u2) const {
        return matches(u,loc,u2);
    }

    bool operator()(const unit & u, const unit & u2) const {
        return matches(u,u2);
    }

    std::vector<const unit *> all_matches_on_map() const {
        return impl_->all_matches_on_map(max_matches_);
    }

    unit_const_ptr first_match_on_map() const {
        return impl_->first_match_on_map();
    }
    
    config to_config() const;
    
    bool empty() const {
        return impl_->empty();
    }
private:
    boost::shared_ptr<unit_filter_abstract_impl> impl_;
    unsigned max_matches_;
};

#endif