#pragma once

#include "json_binary_proxy.hpp"
#include "json_bt.hpp"
#include "json_conversions.hpp"
#include <oxenc/bt_serialize.h>
#include <nlohmann/json.hpp>
#include <stdexcept>
#include <string>
#include <unordered_map>
#include <optional>

namespace llarp::rpc
{
  using json_range = std::pair<nlohmann::json::const_iterator, nlohmann::json::const_iterator>;
  using rpc_input = std::variant<std::monostate, nlohmann::json, oxenc::bt_dict_consumer>;

  // Checks that key names are given in ascending order
  template <typename... Ignore>
  void
  check_ascending_names(std::string_view name1, std::string_view name2, const Ignore&...)
  {
    if (!(name2 > name1))
      throw std::runtime_error{
          "Internal error: request values must be retrieved in ascending order"};
  }

  // Wrapper around a reference for get_values that is used to indicate that the value is
  // required, in which case an exception will be raised if the value is not found.  Usage:
  //
  //     int a_optional = 0, b_required;
  //     get_values(input,
  //         "a", a_optional,
  //         "b", required{b_required},
  //         // ...
  //     );
  template <typename T>
  struct required
  {
    T& value;
    required(T& ref) : value{ref}
    {}
  };
  template <typename T>
  constexpr bool is_required_wrapper = false;
  template <typename T>
  constexpr bool is_required_wrapper<required<T>> = true;

  template <typename T>
  constexpr bool is_std_optional = false;
  template <typename T>
  constexpr bool is_std_optional<std::optional<T>> = true;

  // Wrapper around a reference for get_values that adds special handling to act as if the value was
  // not given at all if the value is given as an empty string.  This sucks, but is necessary for
  // backwards compatibility (especially with wallet2 clients).
  //
  // Usage:
  //
  //     std::string x;
  //     get_values(input,
  //         "x", ignore_empty_string{x},
  //         // ...
  //     );
  template <typename T>
  struct ignore_empty_string
  {
    T& value;
    ignore_empty_string(T& ref) : value{ref}
    {}

    bool
    should_ignore(oxenc::bt_dict_consumer& d)
    {
      if (d.is_string())
      {
        auto d2{d};  // Copy because we want to leave d intact
        if (d2.consume_string_view().empty())
          return true;
      }
      return false;
    }

    bool
    should_ignore(json_range& it_range)
    {
      auto& e = *it_range.first;
      return (e.is_string() && e.get<std::string_view>().empty());
    }
  };

  template <typename T>
  constexpr bool is_ignore_empty_string_wrapper = false;
  template <typename T>
  constexpr bool is_ignore_empty_string_wrapper<ignore_empty_string<T>> = true;

  // Advances the dict consumer to the first element >= the given name.  Returns true if found,
  // false if it advanced beyond the requested name.  This is exactly the same as
  // `d.skip_until(name)`, but is here so we can also overload an equivalent function for json
  // iteration.
  inline bool
  skip_until(oxenc::bt_dict_consumer& d, std::string_view name)
  {
    return d.skip_until(name);
  }
  // Equivalent to the above but for a json object iterator.
  inline bool
  skip_until(json_range& it_range, std::string_view name)
  {
    auto& [it, end] = it_range;
    while (it != end && it.key() < name)
      ++it;
    return it != end && it.key() == name;
  }

  // List types that are expandable; for these we emplace_back for each element of the input
  template <typename T>
  constexpr bool is_expandable_list = false;
  template <typename T>
  constexpr bool is_expandable_list<std::vector<T>> = true;

  // Types that are constructible from string
  template <typename T>
  constexpr bool is_string_constructible = false;
  template <>
  inline constexpr bool is_string_constructible<IPRange> = true;

  // Fixed size elements: tuples, pairs, and std::array's; we accept list input as long as the
  // list length matches exactly.
  template <typename T>
  constexpr bool is_tuple_like = false;
  template <typename T, size_t N>
  constexpr bool is_tuple_like<std::array<T, N>> = true;
  template <typename S, typename T>
  constexpr bool is_tuple_like<std::pair<S, T>> = true;
  template <typename... T>
  constexpr bool is_tuple_like<std::tuple<T...>> = true;

  // True if T is a `std::unordered_map<std::string, ANYTHING...>`
  template <typename T>
  constexpr bool is_unordered_string_map = false;
  template <typename... ValueEtc>
  constexpr bool is_unordered_string_map<std::unordered_map<std::string, ValueEtc...>> = true;

  template <typename TupleLike, size_t... Is>
  void
  load_tuple_values(oxenc::bt_list_consumer&, TupleLike&, std::index_sequence<Is...>);

  // Consumes the next value from the dict consumer into `val`
  template <
      typename BTConsumer,
      typename T,
      std::enable_if_t<
          std::is_same_v<BTConsumer, oxenc::bt_dict_consumer>
              || std::is_same_v<BTConsumer, oxenc::bt_list_consumer>,
          int> = 0>
  void
  load_value(BTConsumer& c, T& target)
  {
    if constexpr (std::is_integral_v<T>)
      target = c.template consume_integer<T>();
    else if constexpr (std::is_same_v<T, std::string> || std::is_same_v<T, std::string_view>)
      target = c.consume_string_view();
    else if constexpr (is_string_constructible<T>)
      target = T{c.consume_string()};
    else if constexpr (llarp::rpc::json_is_binary<T>)
      llarp::rpc::load_binary_parameter(c.consume_string_view(), true /*allow raw*/, target);
    else if constexpr (is_expandable_list<T>)
    {
      auto lc = c.consume_list_consumer();
      target.clear();
      while (!lc.is_finished())
        load_value(lc, target.emplace_back());
    }
    else if constexpr (is_tuple_like<T>)
    {
      auto lc = c.consume_list_consumer();
      load_tuple_values(lc, target, std::make_index_sequence<std::tuple_size_v<T>>{});
    }
    else if constexpr (is_unordered_string_map<T>)
    {
      auto dc = c.consume_dict_consumer();
      target.clear();
      while (!dc.is_finished())
        load_value(dc, target[std::string{dc.key()}]);
    }
    else
      static_assert(std::is_same_v<T, void>, "Unsupported load_value type");
  }

  // Copies the next value from the json range into `val`, and advances the iterator.  Throws
  // on unconvertible values.
  template <typename T>
  void
  load_value(json_range& range_itr, T& target)
  {
    auto& key = range_itr.first.key();
    auto& current = *range_itr.first;  // value currently pointed to by range_itr.first
    if constexpr (std::is_same_v<T, bool>)
    {
      if (current.is_boolean())
        target = current.get<bool>();
      else if (current.is_number_unsigned())
      {
        // Also accept 0 or 1 for bools (mainly to be compatible with bt-encoding which doesn't
        // have a distinct bool type).
        auto b = current.get<uint64_t>();
        if (b <= 1)
          target = b;
        else
          throw std::domain_error{"Invalid value for '" + key + "': expected boolean"};
      }
      else
      {
        throw std::domain_error{"Invalid value for '" + key + "': expected boolean"};
      }
    }
    else if constexpr (std::is_unsigned_v<T>)
    {
      if (!current.is_number_unsigned())
        throw std::domain_error{"Invalid value for '" + key + "': non-negative value required"};
      auto i = current.get<uint64_t>();
      if (sizeof(T) < sizeof(uint64_t) && i > std::numeric_limits<T>::max())
        throw std::domain_error{"Invalid value for '" + key + "': value too large"};
      target = i;
    }
    else if constexpr (std::is_integral_v<T>)
    {
      if (!current.is_number_integer())
        throw std::domain_error{"Invalid value for '" + key + "': value is not an integer"};
      auto i = current.get<int64_t>();
      if (sizeof(T) < sizeof(int64_t))
      {
        if (i < std::numeric_limits<T>::lowest())
          throw std::domain_error{
              "Invalid value for '" + key + "': negative value magnitude is too large"};
        if (i > std::numeric_limits<T>::max())
          throw std::domain_error{"Invalid value for '" + key + "': value is too large"};
      }
      target = i;
    }
    else if constexpr (std::is_same_v<T, std::string> || std::is_same_v<T, std::string_view>)
    {
      target = current.get<std::string_view>();
    }
    else if constexpr (
        llarp::rpc::json_is_binary<T> || is_expandable_list<T> || is_tuple_like<T>
        || is_unordered_string_map<T>)
    {
      try
      {
        current.get_to(target);
      }
      catch (const std::exception& e)
      {
        throw std::domain_error{"Invalid values in '" + key + "'"};
      }
    }
    else
    {
      static_assert(std::is_same_v<T, void>, "Unsupported load type");
    }
    ++range_itr.first;
  }

  template <typename TupleLike, size_t... Is>
  void
  load_tuple_values(oxenc::bt_list_consumer& c, TupleLike& val, std::index_sequence<Is...>)
  {
    (load_value(c, std::get<Is>(val)), ...);
  }

  // Takes a json object iterator or bt_dict_consumer and loads the current value at the iterator.
  // This calls itself recursively, if needed, to unwrap optional/required/ignore_empty_string
  // wrappers.
  template <typename In, typename T>
  void
  load_curr_value(In& in, T& val)
  {
    if constexpr (is_required_wrapper<T>)
    {
      load_curr_value(in, val.value);
    }
    else if constexpr (is_ignore_empty_string_wrapper<T>)
    {
      if (!val.should_ignore(in))
        load_curr_value(in, val.value);
    }
    else if constexpr (is_std_optional<T>)
    {
      load_curr_value(in, val.emplace());
    }
    else
    {
      load_value(in, val);
    }
  }

  // Gets the next value from a json object iterator or bt_dict_consumer.  Leaves the iterator at
  // the next value, i.e.  found + 1 if found, or the next greater value if not found.  (NB:
  // nlohmann::json objects are backed by an *ordered* map and so both nlohmann iterators and
  // bt_dict_consumer behave analogously here).
  template <typename In, typename T>
  void
  get_next_value(In& in, [[maybe_unused]] std::string_view name, T& val)
  {
    if constexpr (std::is_same_v<std::monostate, In>)
      ;
    else if (skip_until(in, name))
      load_curr_value(in, val);
    else if constexpr (is_required_wrapper<T>)
      throw std::runtime_error{"Required key '" + std::string{name} + "' not found"};
  }

  // Accessor for simple, flat value retrieval from a json or bt_dict_consumer.  In the later
  // case note that the given bt_dict_consumer will be advanced, so you *must* take care to
  // process keys in order, both for the keys passed in here *and* for use before and after this
  // call.
  template <typename Input, typename T, typename... More>
  void
  get_values(Input& in, std::string_view name, T&& val, More&&... more)
  {
    if constexpr (std::is_same_v<rpc_input, Input>)
    {
      if (auto* json_in = std::get_if<nlohmann::json>(&in))
      {
        json_range r{json_in->cbegin(), json_in->cend()};
        get_values(r, name, val, std::forward<More>(more)...);
      }
      else if (auto* dict = std::get_if<oxenc::bt_dict_consumer>(&in))
      {
        get_values(*dict, name, val, std::forward<More>(more)...);
      }
      else
      {
        // A monostate indicates that no parameters field was provided at all
        get_values(var::get<std::monostate>(in), name, val, std::forward<More>(more)...);
      }
    }
    else if constexpr (std::is_same_v<std::string_view, Input>)
    {
      if (in.front() == 'd')
      {
        oxenc::bt_dict_consumer d{in};
        get_values(d, name, val, std::forward<More>(more)...);
      }
      else
      {
        auto json_in = nlohmann::json::parse(in);
        json_range r{json_in.cbegin(), json_in.cend()};
        get_values(r, name, val, std::forward<More>(more)...);
      }
    }
    else
    {
      static_assert(
          std::is_same_v<json_range, Input> || std::is_same_v<oxenc::bt_dict_consumer, Input>
          || std::is_same_v<std::monostate, Input>);
      get_next_value(in, name, val);
      if constexpr (sizeof...(More) > 0)
      {
        check_ascending_names(name, more...);
        get_values(in, std::forward<More>(more)...);
      }
    }
  }
}  // namespace llarp::rpc