#pragma once
#include <fmt/core.h>
#include <net/ethernet.h>
#include <netinet/in.h>

#include <algorithm>
#include <array>
#include <chrono>
#include <numeric>
#include <sdeventplus/clock.hpp>
#include <sdeventplus/utility/timer.hpp>
#include <string>
#include <string_view>
#include <type_traits>
#include <unordered_map>
#include <unordered_set>
#include <variant>

namespace phosphor
{
namespace network
{

using namespace std::chrono_literals;

// wait for three seconds before reloading systemd-networkd
constexpr auto reloadTimeout = 3s;

// refresh the objets after four seconds as network
// configuration takes 3-4 sec to reconfigure at most.
constexpr auto refreshTimeout = 4s;

// Byte representations for common address types in network byte order
using InAddrAny = std::variant<in_addr, in6_addr>;
class IfAddr
{
  private:
    InAddrAny addr;
    uint8_t pfx;

    static void invalidPfx(uint8_t pfx);

  public:
    constexpr IfAddr() : addr({}), pfx(0)
    {
    }

    constexpr IfAddr(InAddrAny addr, uint8_t pfx) : addr(addr), pfx(pfx)
    {
        std::visit(
            [pfx](auto v) {
                if (sizeof(v) * 8 < pfx)
                {
                    invalidPfx(pfx);
                }
            },
            addr);
    }

    constexpr auto getAddr() const
    {
        return addr;
    }

    constexpr auto getPfx() const
    {
        return pfx;
    }

    constexpr bool operator==(phosphor::network::IfAddr rhs) const noexcept
    {
        return addr == rhs.addr && pfx == rhs.pfx;
    }
};

using Timer = sdeventplus::utility::Timer<sdeventplus::ClockId::Monotonic>;

struct string_hash : public std::hash<std::string_view>
{
    using is_transparent = void;
};
template <typename V>
using string_umap =
    std::unordered_map<std::string, V, string_hash, std::equal_to<>>;
using string_uset =
    std::unordered_set<std::string, string_hash, std::equal_to<>>;

constexpr std::size_t hash_multi() noexcept
{
    return 0;
}

template <typename T, typename... Args>
constexpr std::size_t hash_multi(const T& v, const Args&... args) noexcept
{
    const std::size_t seed = hash_multi(args...);
    return seed ^ (std::hash<T>{}(v) + 0x9e3779b9 + (seed << 6) + (seed >> 2));
}

namespace detail
{

template <typename T, uint8_t size = sizeof(T)>
struct BswapAlign
{
    using type = T;
};

template <typename T>
struct BswapAlign<T, 2>
{
    using type alignas(uint16_t) = T;
};

template <typename T>
struct BswapAlign<T, 4>
{
    using type alignas(uint32_t) = T;
};

template <typename T>
struct BswapAlign<T, 8>
{
    using type alignas(uint64_t) = T;
};

template <typename T>
constexpr T bswapInt(typename BswapAlign<T>::type n) noexcept
{
    static_assert(std::is_trivially_copyable_v<T>);
    if constexpr (sizeof(T) == 2)
    {
        reinterpret_cast<uint16_t&>(n) =
            __builtin_bswap16(reinterpret_cast<uint16_t&>(n));
    }
    else if constexpr (sizeof(T) == 4)
    {
        reinterpret_cast<uint32_t&>(n) =
            __builtin_bswap32(reinterpret_cast<uint32_t&>(n));
    }
    else if constexpr (sizeof(T) == 8)
    {
        reinterpret_cast<uint64_t&>(n) =
            __builtin_bswap64(reinterpret_cast<uint64_t&>(n));
    }
    else
    {
        auto b = reinterpret_cast<std::byte*>(&n);
        std::reverse(b, b + sizeof(n));
    }
    return n;
}

} // namespace detail

template <typename T>
constexpr T bswap(T n) noexcept
{
    return detail::bswapInt<T>(n);
}

template <typename T>
constexpr T hton(T n) noexcept
{
    if constexpr (std::endian::native == std::endian::big)
    {
        return n;
    }
    else if constexpr (std::endian::native == std::endian::little)
    {
        return bswap(n);
    }
    else
    {
        static_assert(std::is_same_v<T, void>);
    }
}

template <typename T>
constexpr T ntoh(T n) noexcept
{
    return hton(n);
}

namespace detail
{
inline constexpr auto charLookup = []() {
    std::array<int8_t, 256> ret;
    std::fill(ret.begin(), ret.end(), -1);
    for (int8_t i = 0; i < 10; ++i)
    {
        ret[i + '0'] = i;
    }
    for (int8_t i = 0; i < 26; ++i)
    {
        ret[i + 'A'] = i + 10;
        ret[i + 'a'] = i + 10;
    }
    return ret;
}();
}

template <typename T, uint8_t base>
struct DecodeInt
{
    static_assert(base > 1 && base <= 36);
    static_assert(std::is_unsigned_v<T>);

    constexpr T operator()(std::string_view str) const
    {
        if (str.empty())
        {
            throw std::invalid_argument("Empty Str");
        }
        constexpr auto max = std::numeric_limits<T>::max();
        auto ret =
            std::accumulate(str.begin(), str.end(), T{}, [&](T r, char c) {
                auto v = detail::charLookup[c];
                if (v < 0 || v >= base)
                {
                    throw std::invalid_argument("Invalid numeral");
                }
                if constexpr (std::popcount(base) == 1)
                {
                    constexpr auto shift = std::countr_zero(base);
                    constexpr auto maxshift = max >> shift;
                    if (r > maxshift)
                    {
                        throw std::overflow_error("Integer Decode");
                    }
                    return (r << shift) | v;
                }
                else
                {
                    constexpr auto maxbase = max / base;
                    if (r > maxbase)
                    {
                        throw std::overflow_error("Integer Decode");
                    }
                    r *= base;
                    if (max - v < r)
                    {
                        throw std::overflow_error("Integer Decode");
                    }
                    return r + v;
                }
            });
        return ret;
    }
};

template <typename T>
struct ToAddr
{
};

template <>
struct ToAddr<ether_addr>
{
    constexpr ether_addr operator()(std::string_view str) const
    {
        constexpr DecodeInt<uint8_t, 16> di;
        ether_addr ret;
        if (str.size() == 12 && str.find(":") == str.npos)
        {
            for (size_t i = 0; i < 6; ++i)
            {
                ret.ether_addr_octet[i] = di(str.substr(i * 2, 2));
            }
        }
        else
        {
            for (size_t i = 0; i < 5; ++i)
            {
                auto loc = str.find(":");
                ret.ether_addr_octet[i] = di(str.substr(0, loc));
                str.remove_prefix(loc == str.npos ? str.size() : loc + 1);
                if (str.empty())
                {
                    throw std::invalid_argument("Missing mac data");
                }
            }
            ret.ether_addr_octet[5] = di(str);
        }
        return ret;
    }
};

namespace detail
{

template <typename T>
constexpr bool vcontains() noexcept
{
    return false;
}

template <typename T, typename V, typename... Vs>
constexpr bool vcontains() noexcept
{
    return vcontains<T, Vs...>() || std::is_same_v<T, V>;
}

template <typename T, typename... Types>
constexpr std::enable_if_t<vcontains<T, Types...>(), bool>
    veq(T t, std::variant<Types...> v) noexcept
{
    return std::visit(
        [t](auto v) {
            if constexpr (std::is_same_v<T, decltype(v)>)
            {
                return v == t;
            }
            else
            {
                return false;
            }
        },
        v);
}

template <typename T>
struct AddrBufMaker
{
};

template <>
struct AddrBufMaker<ether_addr>
{
  public:
    std::string_view operator()(ether_addr val) noexcept;

  private:
    std::array<char, /*octet*/ 2 * /*octets*/ 6 + /*seps*/ 5> buf;
};

template <>
struct AddrBufMaker<in_addr>
{
  public:
    std::string_view operator()(in_addr val) noexcept;

  private:
    std::array<char, /*octet*/ 3 * /*octets*/ 4 + /*seps*/ 3> buf;
};

template <>
struct AddrBufMaker<in6_addr>
{
  public:
    std::string_view operator()(in6_addr val) noexcept;

  private:
    std::array<char, /*hextet*/ 4 * /*hextets*/ 8 + /*seps*/ 7> buf;
};

template <typename BufMaker>
struct FormatFromBuf
{
  private:
    fmt::formatter<std::string_view> formatter;

  public:
    template <typename ParseContext>
    constexpr auto parse(ParseContext& ctx)
    {
        return ctx.begin();
    }

    template <typename FormatContext>
    auto format(auto v, FormatContext& ctx) const
    {
        return formatter.format(BufMaker{}(v), ctx);
    }
};
} // namespace detail
} // namespace network
} // namespace phosphor

template <typename... Ts>
struct std::hash<std::tuple<Ts...>>
{
    constexpr auto operator()(const std::tuple<Ts...>& t) const noexcept
    {
        return std::apply(phosphor::network::hash_multi<Ts...>, t);
    }
};

template <>
struct std::hash<in_addr>
{
    std::size_t operator()(in_addr addr) const noexcept;
};

template <>
struct std::hash<in6_addr>
{
    std::size_t operator()(in6_addr addr) const noexcept;
};

template <>
struct std::hash<phosphor::network::IfAddr>
{
    std::size_t operator()(phosphor::network::IfAddr addr) const noexcept;
};

namespace fmt
{
template <>
struct formatter<ether_addr>
    : phosphor::network::detail::FormatFromBuf<
          phosphor::network::detail::AddrBufMaker<ether_addr>>
{
};
template <>
struct formatter<in_addr>
    : phosphor::network::detail::FormatFromBuf<
          phosphor::network::detail::AddrBufMaker<in_addr>>
{
};
template <>
struct formatter<in6_addr>
    : phosphor::network::detail::FormatFromBuf<
          phosphor::network::detail::AddrBufMaker<in6_addr>>
{
};
template <>
struct formatter<phosphor::network::InAddrAny>
{
  private:
    fmt::formatter<std::string_view> formatter;

  public:
    template <typename ParseContext>
    constexpr auto parse(ParseContext& ctx)
    {
        return ctx.begin();
    }

    template <typename FormatContext>
    auto format(auto v, FormatContext& ctx) const
    {
        return std::visit(
            [&](auto v) {
                auto abm =
                    phosphor::network::detail::AddrBufMaker<decltype(v)>{};
                return formatter.format(abm(v), ctx);
            },
            v);
    }
};
template <>
struct formatter<phosphor::network::IfAddr>
{
  private:
    fmt::formatter<phosphor::network::InAddrAny> addrF;
    fmt::formatter<char> strF;
    fmt::formatter<uint8_t> numF;

  public:
    template <typename ParseContext>
    constexpr auto parse(ParseContext& ctx)
    {
        return ctx.begin();
    }

    template <typename FormatContext>
    auto format(auto v, FormatContext& ctx) const
    {
        addrF.format(v.getAddr(), ctx);
        strF.format('/', ctx);
        return numF.format(v.getPfx(), ctx);
    }
};
} // namespace fmt

namespace std
{
string to_string(ether_addr value);
string to_string(in_addr value);
string to_string(in6_addr value);
string to_string(phosphor::network::InAddrAny value);
string to_string(phosphor::network::IfAddr value);
} // namespace std

constexpr bool operator==(ether_addr lhs, ether_addr rhs) noexcept
{
    return std::equal(lhs.ether_addr_octet, lhs.ether_addr_octet + 6,
                      rhs.ether_addr_octet);
}

constexpr bool operator==(in_addr lhs, in_addr rhs) noexcept
{
    return lhs.s_addr == rhs.s_addr;
}

constexpr bool operator==(in6_addr lhs, in6_addr rhs) noexcept
{
    return std::equal(lhs.s6_addr32, lhs.s6_addr32 + 4, rhs.s6_addr32);
}

template <typename T>
constexpr std::enable_if_t<!std::is_same_v<phosphor::network::InAddrAny, T>,
                           bool>
    operator==(phosphor::network::InAddrAny lhs, T rhs) noexcept
{
    return phosphor::network::detail::veq(rhs, lhs);
}

auto& operator<<(auto& os, ether_addr v)
{
    return os << phosphor::network::detail::AddrBufMaker<ether_addr>{}(v);
}

auto& operator<<(auto& os, in_addr v)
{
    return os << phosphor::network::detail::AddrBufMaker<in_addr>{}(v);
}

auto& operator<<(auto& os, in6_addr v)
{
    return os << phosphor::network::detail::AddrBufMaker<in6_addr>{}(v);
}

auto& operator<<(auto& os, phosphor::network::InAddrAny v)
{
    return os << std::visit(
               [](auto v) {
                   return phosphor::network::detail::AddrBufMaker<
                       decltype(v)>{}(v);
               },
               v);
}

auto& operator<<(auto& os, phosphor::network::IfAddr v)
{
    return os << v.getAddr() << "/" << std::dec << int{v.getPfx()};
}