#include "lib/exec.h"

#include <iostream>
#include <functional>
#include <ranges>
#include <string>
#include <sstream>
#include <tuple>
#include <unordered_map>
#include <vector>

#include <fmt/core.h>
#include <fmt/ranges.h>

using namespace std;

using MemoKey = tuple<size_t, size_t, size_t>;

class TupleHash : function<size_t(const MemoKey&)> {
public:
    size_t operator()(const MemoKey& k) const { return get<0>(k) ^ get<1>(k) ^ get<2>(k); }
};

template <typename T>
size_t lcss_inner(const vector<T> &a, const vector<T> &b, size_t i, size_t j,
                  size_t length, size_t &longest, vector<T> &longest_seq,
                  unordered_map<tuple<size_t, size_t, size_t>, size_t, TupleHash> &cache) {
  if (i >= a.size() || j >= b.size()) {
    return length;
  }

  const auto key = make_tuple(i, j, length);
  if (cache.contains(key)) {
    return get<1>(*cache.find(key));
  }


  if (a.at(i) == b.at(j)) {
    // Current (i, j) is member of a common subsequence.
    longest = max(longest, length + 1);
    size_t remaining_longest =
        lcss_inner(a, b, i + 1, j + 1, length + 1, longest, longest_seq, cache);
    if (remaining_longest == longest) {
      // This element is part of the longest common subsequence.
      longest_seq.at(length) = a.at(i);
    }
    cache.insert(make_pair(key, remaining_longest));
    return remaining_longest;
  } else {
    // Skip element from a.
    size_t remaining_longest_skip_a =
        lcss_inner(a, b, i + 1, j, length, longest, longest_seq, cache);
    // Skip element from b.
    size_t remaining_longest_skip_b =
        lcss_inner(a, b, i, j + 1, length, longest, longest_seq, cache);
    size_t result = max(remaining_longest_skip_a, remaining_longest_skip_b);
    cache.insert(make_pair(key, result));
    return result;
  }
}

template<typename T>
vector<T> lcss(const vector<T>& a, const vector<T>& b) {
    size_t longest = 0;
    vector<T> longest_seq(min(a.size(), b.size()));
    unordered_map<tuple<size_t, size_t, size_t>, size_t, TupleHash> cache(100);
    size_t longest_r = lcss_inner(a, b, 0, 0, 0, longest, longest_seq, cache);

    fmt::print("Length: {} / {}\n", longest, longest_r);

    return longest_seq;
}
// g++ only
template<typename T, template<typename> typename C>
void evaluate_lcss(const C<T>& a, const C<T>& b) requires ranges::range<C<T>> {
    vector<T> va(a.begin(), a.end());
    vector<T> vb(b.begin(), b.end());
    auto result = timeit_f(function([&va, &vb]() { return lcss(va, vb); }));

    fmt::print("{}\n", va);
    fmt::print("{}\n", vb);
    fmt::print("{}\n", result);
}

int main(void) {

    vector<int> a{1,6,2,-1,3,55,2,4,23,5,6,7,8,9,10};
    vector<int> b{-3, 1, 5, 7, 2, 4, -1, 3, 6, 7, 9, 11, 10};

    evaluate_lcss(a, b);
    evaluate_lcss(views::single(11), views::single(11));
    return 0;
}