/*
Copyright (c) 2013 Microsoft Corporation. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.

Author: Leonardo de Moura
*/
#pragma once
#include <memory>
#include "environment.h"
#include "formatter.h"

namespace lean {
class frontend;
/**
   \brief Expression elaborator, it is responsible for "filling" holes
   in terms left by the user. This is the main module resposible for computing
   the value of implicit arguments.
*/
class elaborator {
    class imp;
    std::shared_ptr<imp> m_ptr;
    static void print(imp * ptr);
public:
    explicit elaborator(frontend const & fe);
    ~elaborator();

    expr operator()(expr const & e);
    expr operator()(expr const & e, expr const & expected_type);

    /**
        \brief If \c e is an expression instantiated by the elaborator, then it
        returns the expression (the one with "holes") used to generate \c e.
        Otherwise, it just returns \c e.
    */
    expr const & get_original(expr const & e) const;

    void set_interrupt(bool flag);
    void interrupt() { set_interrupt(true); }
    void reset_interrupt() { set_interrupt(false); }

    void clear();

    environment const & get_environment() const;

    void display(std::ostream & out) const;
    format pp(formatter & f, options const & o) const;

    bool has_constraints() const;
};
/**
    \brief Create a choice expression for the given functions.
    It is used to mark which functions can be used in a particular application.
    The elaborator decides which one should be used based on the type of the arguments.

    \pre num_fs >= 2
*/
expr mk_choice(unsigned num_fs, expr const * fs);
/**
    \brief Return true iff \c e is an expression created using \c mk_choice.
*/
bool is_choice(expr const & e);
/**
   \brief Return the number of alternatives in a choice expression.
   We have that <tt>get_num_choices(mk_choice(n, fs)) == n</tt>.

   \pre is_choice(e)
*/
unsigned get_num_choices(expr const & e);
/**
   \brief Return the (i+1)-th alternative of a choice expression.

   \pre is_choice(e)
   \pre i < get_num_choices(e)
*/
expr const & get_choice(expr const & e, unsigned i);
}