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#ifndef _SPEL_CACHE_2_H_
#define _SPEL_CACHE_2_H_

#include <future>
#include <tuple>
#include <unordered_map>
#include <iostream>
#include <string>
#include <sstream>

#include "error.h"
#include "input.h"
#include "cache/md5.h"
#include "cache/file.h"

/* forward */ struct md5_digest;

template <typename X> struct clean_type { typedef typename std::remove_reference<X>::type type; };
template <typename X> struct clean_type<const X&> { typedef X type; };
template <typename X> struct clean_type<X&> { typedef X type; };
template <typename X> struct clean_type<const X> { typedef X type; };


static inline std::string& cache_directory() { static std::string _ = "tmp"; return _; }

template <typename T> struct generic_value_interface;
template <typename T> struct value;
template <typename T> struct range;
template <typename T> struct collection;

template <typename T> struct fail : std::integral_constant<bool, false> {};

template <typename T> struct value<collection<T>> { static_assert(fail<T>::value, "Can't instantiate this"); };


template <typename T> struct immediate_value;

template <typename FuncType> struct async_computation;
template <typename FuncType> struct cached_computation;
template <typename FuncType> struct computed_value_factory;
template <typename FuncType> struct computed_value;
template <typename FuncType> struct cached_computed_value;

/* a value<T> behaves as a pointer to T */

template <typename T>
    struct generic_value_interface {
        typedef T value_type;

        virtual ~generic_value_interface() {}

        virtual value_type& operator * () = 0;
        virtual value_type* operator -> () = 0;

        virtual const value_type& operator * () const = 0;
        virtual const value_type* operator -> () const = 0;

        virtual size_t hash() const = 0;
        virtual md5_digest& md5(md5_digest&) const = 0;
        virtual bool equal(const generic_value_interface<T>&) const { return false; }
        virtual bool __equal__(const T&) const { return false; }
    };

/* Lightweight */
template <typename T>
    struct value {
        typedef T value_type;

        value() : m_impl() {}
        value(generic_value_interface<T>* v) : m_impl(v) {}
        value(const T& immed) : m_impl(new immediate_value<T>(immed)) {}
        value(T&& immed) : m_impl(new immediate_value<T>(std::forward<T>(immed))) {}

        value_type& operator * () { return m_impl->operator * (); }
        value_type* operator -> () { return m_impl->operator -> (); }
        const value_type& operator * () const { return m_impl->operator * (); }
        const value_type* operator -> () const { return m_impl->operator -> (); }
        size_t hash() const { return m_impl->hash(); }
        md5_digest& md5(md5_digest& md) const { return m_impl->md5(md); }

        value<T> operator = (const T& immed)
        {
            /*m_impl = new immediate_value<T>(immed);*/
            m_impl = std::make_shared<immediate_value<T>>(immed);
            return *this;
        }

        value<T> operator = (std::shared_ptr<generic_value_interface<T>>& new_impl)
        {
            m_impl = new_impl;
            return *this;
        }

        value<T> operator = (const value<T>& new_impl)
        {
            m_impl = new_impl.m_impl;
            return *this;
        }

        bool valid() const { return (bool) m_impl; }

        bool equal(const value<T>& v) const { return m_impl == v.m_impl || m_impl->equal(*v.m_impl); }

    protected:
        std::shared_ptr<generic_value_interface<T>> m_impl;
    };

template <typename T>
bool operator == (const value<T>& v1, const value<T>& v2) { return v1.equal(v2); }

namespace std {
    template <typename T>
        struct hash<value<T>> {
            size_t operator () (const value<T>& v) const
            {
                return v.hash();
            }
        };
}

template <typename VT>
std::ostream& operator << (std::ostream& os, const value<VT>& v)
{
    return os << (*v);
}

template <typename VT>
md5_digest& operator << (md5_digest& md5, const value<VT>& v)
{
    return v.md5(md5);
}


struct md5_hash_type {
    std::string accum;
    std::string append;
};


namespace redux {
template <typename Functor, typename... Elems> struct reduce_impl;

template <typename Functor, typename Elem>
    struct reduce_impl<Functor, Elem> {
        template <typename accum_type>
        void operator () (Functor& f, accum_type& accum, const Elem& e)
        {
            /*std::cout << "final e=" << e << std::endl;*/
            f(accum, e);
        }
    };

template <typename Functor, typename Elem, typename... Elems>
    struct reduce_impl<Functor, Elem, Elems...> {
        template <typename accum_type>
        void operator () (Functor& f, accum_type& accum, const Elem& e, const Elems&... x)
        {
            /*std::cout << "e=" << e << std::endl;*/
            f(accum, e);
            reduce_impl<Functor, Elems...>()(f, accum, x...);
        }
    };

struct reduce {
    template <typename Functor, typename... Elems>
        auto operator () (typename Functor::accum_type accum, Functor& f, const Elems&... e)
            -> typename Functor::accum_type
        {
            reduce_impl<Functor, Elems...>()(f, accum, e...);
            return accum;
        }

    template <typename Functor, typename... Elems>
        auto operator () (Functor& f, const Elems&... e)
            -> typename Functor::accum_type
        {
            typename Functor::accum_type accum = typename Functor::accum_type();
            reduce_impl<Functor, Elems...>()(f, accum, e...);
            return accum;
        }
};

struct hash {
    typedef size_t accum_type;
    template <typename T>
        void operator () (size_t accum, const T& t) { accum = accum ^ std::hash<T>()(t); }
    template <typename VT>
        void operator () (size_t accum, const value<VT>& v) { accum = accum ^ v.hash(); }
};

struct md5 {
    typedef md5_digest& accum_type;
    template <typename T>
        void operator () (md5_digest& md, const T& t) { md << t; }
    template <typename VT>
        void operator () (md5_digest& md, const value<VT>& v) { v.md5(md); }
};

struct md5_append {
    typedef std::stringstream& accum_type;
    template <typename T>
        void operator () (std::stringstream& ss, const T& t)
        {
            md5_digest md;
            md << t;
            ss << (std::string) md;
        }
    template <typename VT>
        void operator () (std::stringstream& ss, const value<VT>& t)
        {
            md5_digest md;
            ss << (std::string) t.md5(md);
        }
};
} /* namespace redux */

template <typename... Elems>
size_t compute_hash(const Elems&... e) { redux::hash h; return redux::reduce()(0, h, e...); }

template <typename... Elems>
std::string compute_md5(const Elems&... e)
{
    md5_digest md;
    redux::md5 m;
    redux::reduce()(md, m, e...);
    return md;
}

template <typename... Elems>
std::string append_md5(const Elems&... e) { std::stringstream ss; redux::md5_append ma; return redux::reduce()(ss, ma, e...).str(); }


template <typename ValueType>
    struct immediate_value : generic_value_interface<ValueType> {
        typedef ValueType value_type;

        value_type m_storage;

        immediate_value(const ValueType& v) : m_storage(v) {}
        immediate_value(ValueType&& v) : m_storage(std::forward<ValueType>(v)) {}

        virtual
            value_type& operator * ()
            override { return m_storage; }
        virtual
            value_type* operator -> ()
            override { return &m_storage; }
        virtual
            const value_type& operator * () const
            override { return m_storage; }
        virtual
            const value_type* operator -> () const
            override { return &m_storage; }

        virtual
            size_t hash() const
            override { return std::hash<ValueType>()(m_storage); }
        virtual
            md5_digest& md5(md5_digest& md) const
            override { return md << m_storage; }

        virtual
            bool equal(const generic_value_interface<ValueType>& gvi) const
            override
            {
                return gvi.__equal__(m_storage);
            }

        virtual
            bool __equal__(const ValueType& v) const
            override
            {
                return m_storage == v;
            }
    };


template <typename ValueType>
    struct unique_value : generic_value_interface<ValueType> {
        typedef ValueType value_type;

        value_type m_storage;

        unique_value(const ValueType& v) : m_storage(v) {}
        unique_value(ValueType&& v) : m_storage(std::forward<ValueType>(v)) {}
        unique_value() : m_storage() {}

        virtual
            value_type& operator * ()
            override { return m_storage; }
        virtual
            value_type* operator -> ()
            override { return &m_storage; }
        virtual
            const value_type& operator * () const
            override { return m_storage; }
        virtual
            const value_type* operator -> () const
            override { return &m_storage; }

        virtual
            size_t hash() const
            override { return std::hash<const void*>()(this); }
        virtual
            md5_digest& md5(md5_digest& md) const
            override { return md << m_storage; }
    };

/*template <typename M, typename R, typename C>*/
    /*struct immediate_value<labelled_matrix<M, R, C>>*/
        /*: unique_value<labelled_matrix<M, R, C>> {};*/



template <typename Ret, typename... Args>
    struct async_computation<Ret(Args...)> {
        typedef async_computation<Ret(Args...)> this_type;
        typedef Ret value_type;
        typedef Ret (*computation_function_pointer_type) (Args...);
        typedef std::packaged_task<Ret(Args...)> task_type;

        async_computation(computation_function_pointer_type func,
                          const value<typename clean_type<Args>::type>&... args)
            : dependencies(args...)
            , m_storage()
            /*, m_future(task_type(func, *args...).get_future())*/
            , m_future(std::async(func, *args...))
        {}

        async_computation(std::function<Ret(Args...)>& func,
                          const value<typename clean_type<Args>::type>&... args)
            : dependencies(args...)
            , m_storage()
            /*, m_future(task_type(func, *args...).get_future())*/
            , m_future(std::async(func, *args...))
        {}

        value_type& __get_noconst()
        {
            if (m_future.valid()) {
                return m_storage = m_future.get();
            }
            return m_storage;
        }

        const value_type& __get_const() const
        {
            return const_cast<this_type*>(this)->__get_noconst();
        }

    protected:
        std::tuple<value<typename clean_type<Args>::type>...> dependencies;
        value_type m_storage;
        std::future<Ret> m_future;
    };


template <typename Ret, typename... Args>
    struct cached_computation<Ret(Args...)> {
        typedef Ret value_type;

        cached_computation(const std::string& name, Ret (*f) (Args...), const value<Args>&... args)
            : m_name(name)
            , m_func(f)
            , m_md5_hash{.accum = compute_md5(args...), .append = append_md5(args...)}
        {}

        std::string get_path() const
        {
            std::stringstream ss;
            ss << cache_directory() << '/' << m_name << '_' << m_md5_hash.accum << '_' << typeid(Ret).name();
            return ss.str();
        }

        Ret operator () (Args... x)
        {
            Ret data;
            std::string path = get_path();
            /* if cache file found */
            if (check_file(path, false, true)) {
                std::ifstream ifs(path);
                cache_input ci(ifs);
                std::string check;
            /*   read string */
                ci & check;
            /*   compare to m_md5_hash.append */
                if (check == m_md5_hash.append) {
            /*   if same */
            /*     CACHE FOUND */
                    MSG_INFO("Found data in cache");
                    ci & data;
            /*     return value read from file */
                    return data;
                }
            /*   CACHE INVALID */
                MSG_INFO("Cache is invalid. Computing data.");
            } else {
            /* else */
            /*   COMPUTE AND SAVE */
                MSG_INFO("Computing data.");
            }
            /* compute value = m_func(x...) */
            data = m_func(x...);
            /* write m_md5_hash.append to file */
            std::ofstream ofs(path);
            cache_output co(ofs);
            co & m_md5_hash.append;
            /* write value to file */
            co & data;
            /* return value */
            return data;
        }

    protected:
        std::string m_name;
        Ret (*m_func) (Args...);
        md5_hash_type m_md5_hash;
    };


template <typename Ret, typename... Args>
    struct computed_value<Ret(Args...)> : generic_value_interface<Ret> {
        typedef Ret value_type;
        typedef std::function<Ret(Args...)> computation_type;

        computed_value(Ret (*func) (Args...), const value<typename clean_type<Args>::type>&... args)
            : m_hash(compute_hash(args...))
            , m_task(func, args...)
        {}

        virtual
            value_type& operator * ()
            override { return m_task.__get_noconst(); }
        virtual
            value_type* operator -> ()
            override { return &m_task.__get_noconst(); }
        virtual
            const value_type& operator * () const
            override { return m_task.__get_const(); }
        virtual
            const value_type* operator -> () const
            override { return &m_task.__get_const(); }

        virtual
            size_t hash() const
            override { return m_hash; }
        virtual
            md5_digest& md5(md5_digest& md) const
            override { return md; }

    protected:
        size_t m_hash;
        async_computation<Ret(Args...)> m_task;
    };

template <typename Ret, typename... Args>
    struct cached_computed_value<Ret(Args...)> : generic_value_interface<Ret> {
        typedef Ret value_type;
        typedef std::function<Ret(Args...)> computation_type;

        cached_computed_value(const std::string& name, Ret (*func) (Args...), const value<Args>&... args)
            : m_hash(compute_hash(args...))
            , m_comp(name, func, args...)
            , m_comp_proxy([this](Args... x) { return m_comp(x...); })
            , m_task(m_comp_proxy, args...)
        {}

        virtual
            value_type& operator * ()
            override { return m_task.__get_noconst(); }
        virtual
            value_type* operator -> ()
            override { return &m_task.__get_noconst(); }
        virtual
            const value_type& operator * () const
            override { return m_task.__get_const(); }
        virtual
            const value_type* operator -> () const
            override { return &m_task.__get_const(); }

        virtual
            size_t hash() const
            override { return m_hash; }
        virtual
            md5_digest& md5(md5_digest& md) const
            override { return md; }

    protected:
        size_t m_hash;
        cached_computation<Ret(Args...)> m_comp;
        std::function<Ret(Args...)> m_comp_proxy;
        async_computation<Ret(Args...)> m_task;
    };


/* ranges and collections */

/* T must have operators + and < */
template <typename T>
    struct range {
        T m_min, m_max, m_step;
        range(T min, T max, T step)
            : m_min(min), m_max(max), m_step(step)
        {}
        struct iterator {
            value<T> m_data;
            T m_step;
            T m_max;
            iterator(T value, T max, T step)
                : m_data(new immediate_value<T>(value)), m_step(step), m_max(max)
            {}
            iterator& operator ++ ()
            {
                *m_data += m_step;
                if (*m_data > m_max) {
                    *m_data = m_max;
                }
                return *this;
            }
            bool operator == (const iterator& i) const
            {
                return *m_data == *i.m_data;
            }
            bool operator != (const iterator& i) const
            {
                return *m_data != *i.m_data;
            }
            const value<T>& operator * () const { return m_data; }
        };
        iterator begin() const { return {m_min, m_max, m_step}; }
        iterator end() const { return {m_max, m_max, 0}; }
    };


#if 0
template <typename ValueType, typename... AllArgs> struct registry_impl_type;
template <typename ValueType>
    struct registry_impl_type<ValueType> { typedef ValueType type; };
template <typename ValueType, typename Arg0, typename... OtherArgs>
    struct registry_impl_type<ValueType, Arg0, OtherArgs...> {
        typedef std::unordered_map<Arg0, registry_impl_type<ValueType, OtherArgs...>::type> type;
    };
#endif

template <typename ValueType, typename... AllArgs>
struct computation_registry {
    typedef ValueType value_type;

    template <typename... Args> struct registry_impl;

    template <typename Arg0>
        struct registry_impl<Arg0> {
            std::unordered_map<Arg0, value_type> m_registry;
            value_type& get_(const Arg0& arg)
            {
                return m_registry[arg];
            }

            size_t size() const { return m_registry.size(); }
        };

    template <typename Arg0, typename... Args>
        struct registry_impl<Arg0, Args...> {
            std::unordered_map<Arg0, registry_impl<Args...>> m_registry;
            value_type& get_(const Arg0& car, const Args&... cdr)
            {
                return m_registry[car].get_(cdr...);
            }

            size_t size() const
            {
                size_t accum = 0;
                for (auto& kv: m_registry) {
                    accum += kv.second.size();
                }
                return accum;
            }
        };

    registry_impl<AllArgs...> m_registry;

    template <typename... Args>
        value_type& get(const Args&... args)
        {
            return m_registry.get_(args...);
        }

    size_t size() const { return m_registry.size(); }
};


template <typename Ret, typename... Args>
computation_registry<value<Ret>, Ret (*) (Args...), value<typename clean_type<Args>::type>...>&
__get_registry()
{
    static computation_registry<value<Ret>, Ret (*) (Args...), value<typename clean_type<Args>::type>...> _reg_;
    /*MSG_DEBUG("Registry at " << (&_reg_));*/
    return _reg_;
}



template <typename VT>
using clean_value_type = value<typename clean_type<VT>::type>;


template <typename Ret, typename... Args>
/*computed_value<Ret(Args...)>**/
value<Ret>&
make_value(Ret (&f) (Args...), const value<typename clean_type<Args>::type>&... x)
{
    auto& _reg_ = __get_registry<Ret, Args...>();
    /*return new computed_value<Ret(Args...)>(&f, x...);*/
    value<Ret>& ret = _reg_.get(&f, x...);
    if (!ret.valid()) {
        /*MSG_INFO("New computed value reg.size=" << (_reg_.size()));*/
        ret = new computed_value<Ret(Args...)>(f, x...);
    } else {
        /*MSG_INFO("Existing computed value reg.size=" << (_reg_.size()));*/
    }
    return ret;
}

template <typename Ret, typename... Args>
value<Ret>&
make_cached_value_impl(const std::string& name, Ret (&f) (Args...), const clean_value_type<Args>&... x)
{
    /*static computation_registry<value<Ret>, Ret (*) (Args...), value<Args>...> _reg_;*/
    /*return new cached_computed_value<Ret(Args...)>(name, &f, x...);*/
    /*value<Ret>& ret = _reg_.get(&f, x...);*/
    value<Ret>& ret = __get_registry<Ret, Args...>().get(&f, x...);
    if (!ret.valid()) {
        MSG_INFO("New cached computed value");
        ret = new cached_computed_value<Ret(Args...)>(name, f, x...);
    } else {
        MSG_INFO("Existing cached computed value");
    }
    return ret;
}


#define make_cached_value(__fname, ...) make_cached_value_impl(#__fname, __fname ,##__VA_ARGS__)


template <typename T> struct collection : std::vector<value<T>> {
    using std::vector<value<T>>::vector;
};

template <typename F, typename R, typename P> struct make_coll_impl;

template <typename A, typename B> struct types_must_be_identical : std::integral_constant<bool, false> {};
template <> struct types_must_be_identical<int, double> : std::integral_constant<bool, false> {};
template <> struct types_must_be_identical<double, int> : std::integral_constant<bool, false> {};
template <typename A> struct types_must_be_identical<A, A> : std::integral_constant<bool, true> {};
template <typename A> struct types_must_be_identical<const A&, A> : std::integral_constant<bool, true> {};
template <typename A> struct types_must_be_identical<A&, A> : std::integral_constant<bool, true> {};
template <typename A> struct types_must_be_identical<const A, A> : std::integral_constant<bool, true> {};

template <typename LA, typename LB> struct type_lists_must_be_identical;
template <> struct type_lists_must_be_identical<std::tuple<>, std::tuple<>> {};

template <typename A0, typename... A, typename B0, typename... B>
    struct type_lists_must_be_identical<std::tuple<A0, A...>, std::tuple<B0, B...>>
            : type_lists_must_be_identical<std::tuple<A...>, std::tuple<B...>> {
        static_assert(types_must_be_identical<A0, B0>::value, "INVALID PARAMETER TYPE.");
    };

template <typename Ret, typename... FuncArgs, typename... ErrArgs>
struct make_coll_impl<Ret(FuncArgs...), std::tuple<>, std::tuple<ErrArgs...>> {
    void operator () (collection<Ret>& coll,
                      Ret (&f) (FuncArgs...),
                      ErrArgs... errargs)
    {
        type_lists_must_be_identical<std::tuple<FuncArgs...>, std::tuple<typename ErrArgs::value_type...>>();
        coll.push_back(make_value(f, errargs...));
    }
};

template <typename Ret, typename... FuncArgs>
struct make_coll_impl<Ret(FuncArgs...), std::tuple<>, std::tuple<clean_value_type<FuncArgs>...>> {
    void operator () (collection<Ret>& coll,
                      Ret (&f) (FuncArgs...),
                      const value<typename clean_type<FuncArgs>::type>&... pargs)
    {
        coll.push_back(make_value(f, pargs...));
    }
};


template <typename Ret, typename... FuncArgs, typename VT, typename... ArgsRemaining, typename... PreviousArgs>
struct make_coll_impl<Ret(FuncArgs...), std::tuple<value<VT>, ArgsRemaining...>, std::tuple<PreviousArgs...>> {
    void operator () (collection<Ret>& coll,
                      Ret (&f) (FuncArgs...),
                      const value<VT>& car,
                      const ArgsRemaining&... cdr,
                      const PreviousArgs&... pargs)
    {
        make_coll_impl<
            Ret(FuncArgs...),
            std::tuple<ArgsRemaining...>,
            std::tuple<PreviousArgs..., value<VT>>>() (coll, f, cdr..., pargs..., car);
    }
};

template <typename Ret, typename... FuncArgs, typename T, typename... ArgsRemaining, typename... PreviousArgs>
struct make_coll_impl<Ret(FuncArgs...), std::tuple<range<T>, ArgsRemaining...>, std::tuple<PreviousArgs...>> {
    void operator () (collection<Ret>& coll,
                      Ret (&f) (FuncArgs...),
                      const range<T>& car,
                      const ArgsRemaining&... cdr,
                      const PreviousArgs&... pargs)
    {
        typedef value<T> vtype;
        for (const vtype& v: car) {
            make_coll_impl<
                Ret(FuncArgs...),
                std::tuple<ArgsRemaining...>,
                std::tuple<PreviousArgs..., vtype>>() (coll, f, cdr..., pargs..., v);
        }
    }
};

template <typename Ret, typename... FuncArgs, typename T, typename... ArgsRemaining, typename... PreviousArgs>
struct make_coll_impl<Ret(FuncArgs...), std::tuple<collection<T>, ArgsRemaining...>, std::tuple<PreviousArgs...>> {
    void operator () (collection<Ret>& coll,
                      Ret (&f) (FuncArgs...),
                      const collection<T>& car,
                      const ArgsRemaining&... cdr,
                      const PreviousArgs&... pargs)
    {
        typedef value<T> vtype;
        for (const vtype& v: car) {
            make_coll_impl<
                Ret(FuncArgs...),
                std::tuple<ArgsRemaining...>,
                std::tuple<PreviousArgs..., vtype>>() (coll, f, cdr..., pargs..., v);
        }
    }
};



template <typename Ret, typename... Args, typename... CollArgs>
collection<Ret>
make_collection(Ret (&f) (Args...), CollArgs... args)
{
    collection<Ret> ret;
    make_coll_impl<Ret(Args...), std::tuple<CollArgs...>, std::tuple<>>() (ret, f, args...);
    return ret;
}


#endif