/*
Copyright (c) 2014 Microsoft Corporation. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.

Author: Leonardo de Moura
*/
#pragma once
#include "kernel/environment.h"

namespace lean {
/** \brief Object to simulate delayed justification creation. */
class delayed_justification {
    optional<justification>        m_jst;
    std::function<justification()> m_mk;
public:
    template<typename Mk> delayed_justification(Mk && mk):m_mk(mk) {}
    justification get() { if (!m_jst) { m_jst = m_mk(); } return *m_jst; }
};

/** \brief Auxiliary exception used to sign that constraints cannot be created when \c m_cnstrs_enabled flag is false. */
struct add_cnstr_exception {};

class converter {
public:
    /** \brief Abstract context that must be provided to a converter object. */
    class context {
        virtual bool enable_cnstrs(bool flag) = 0;
    public:
        virtual name mk_fresh_name() = 0;
        virtual expr infer_type(expr const & e) = 0;
        virtual void add_cnstr(constraint const & c) = 0;
        class disable_cnstrs_scope {
            context & m_ctx;
            bool      m_old;
        public:
            disable_cnstrs_scope(context & ctx):m_ctx(ctx), m_old(m_ctx.enable_cnstrs(false)) {}
            ~disable_cnstrs_scope() { m_ctx.enable_cnstrs(m_old); }
        };
    };

    virtual ~converter() {}

    virtual expr whnf(expr const & e, context & c) = 0;
    virtual bool is_conv(expr const & t, expr const & s, context & c, delayed_justification & j) = 0;
    virtual bool is_def_eq(expr const & t, expr const & s, context & c, delayed_justification & j) = 0;
    bool is_conv(expr const & t, expr const & s, context & c);
    bool is_def_eq(expr const & t, expr const & s, context & c);
};

std::unique_ptr<converter> mk_dummy_converter();
std::unique_ptr<converter> mk_default_converter(environment const & env,
                                                optional<module_idx> mod_idx = optional<module_idx>(),
                                                bool memoize = true,
                                                name_set const & extra_opaque = name_set());
}