#include <bitset>
#include <span>
#include <cstdint>
#include <iostream>
#include <string>
#include <algorithm>
#include <vector>
#include "VoxelSpace.h"

using SomaSolution = std::vector<uint64_t>;

struct Solver {
    std::vector<uint64_t>* input;
    std::vector<int>* offsets;
    std::vector<SomaSolution>* solutions;
};

auto backtrack_solve_iter(std::vector<uint64_t> *polycube_input, std::vector<int> *offsets)-> void {
    auto num_inputs = offsets->size() - 1;

    auto solns = std::vector<int>();

    auto iter_stack = std::vector<int>();
    auto curr_soln_stack = std::vector<int>();
    auto soln_spaces_stack = std::vector<uint64_t>();
    soln_spaces_stack.push_back(0ul);

    auto depth = 0;

    while (depth >= 0) {
        if (depth >= iter_stack.size()) {
            iter_stack.push_back(offsets->at(depth));
        }
        auto end = offsets->at(depth + 1);
        auto broke = false;
        for (; iter_stack[depth] < end; iter_stack[depth]++) {
            auto next_space = polycube_input->at(iter_stack[depth]);
            auto soln_space = soln_spaces_stack[depth];
            std::cout << next_space << " " << soln_space << std::endl;
            auto successful_fuse = (soln_space | next_space) == (soln_space ^ next_space);
            if (successful_fuse) {
                soln_spaces_stack.push_back(soln_space |= next_space);
                curr_soln_stack.push_back(iter_stack[depth]);
                depth++;
                if (curr_soln_stack.size() == num_inputs) {
                    solns.push_back(1);
                    curr_soln_stack.pop_back();
                    soln_spaces_stack.pop_back();
                    depth--;
                } else {
                    depth++;
                    auto broke = true;
                    break;
                }
            }
        }
        if (!broke) {
            curr_soln_stack.pop_back();
            soln_spaces_stack.pop_back();
            depth--;
        }
    }
    std::cout << "Done. Found " << solns.size() << " solutions." << std::endl;
}

auto backtrack_solve(Solver *solver, uint64_t working_solution = 0ul, int curr_piece = 0) -> void {
    auto input = solver->input;
    auto offsets = solver->offsets;
    auto solutions = solver->solutions;
    auto start = offsets->at(curr_piece);
    auto end = offsets->at(curr_piece + 1);
    auto num_pieces = offsets->size() - 1;
    for (int i = start; i < end; i++) {
        auto successful_fuse = !Voxel::collides(working_solution, input->at(i));
        if (successful_fuse) {
            auto new_working_solution = working_solution | input->at(i);
            solutions->back().at(curr_piece) = input->at(i);
            if (curr_piece == num_pieces - 1) {
                auto last_soln = solutions->back();
                solutions->push_back(SomaSolution(last_soln.begin(), last_soln.end()));
                return;
            } else {
                backtrack_solve(solver, new_working_solution, curr_piece + 1);
            }
        }
    }
    if (curr_piece == 0) {
        solutions->pop_back();
    } 
}

auto get_solution_rotations(SomaSolution *solution, int dims[3]) -> std::vector<SomaSolution> {
    auto result = std::vector<SomaSolution>(Voxel::NUM_ROTS_3D);
    for (int piece_i = 0; piece_i < solution->size(); piece_i++) {
        auto space = Voxel::Space{ 
            .space=solution->at(piece_i),
            .dim_x=dims[0],
            .dim_y=dims[1],
            .dim_z=dims[2],
        };
        auto piece_rotations = Voxel::getAllRotations(&space);
        for (int rot_i = 0; rot_i < piece_rotations.size(); rot_i++) {
            result[rot_i].push_back(piece_rotations[rot_i].space);
        }
    }
    return result;
}

auto filter_unique(std::vector<SomaSolution> *solutions, int dims[3]) -> std::vector<SomaSolution> {
    if (solutions->size() == 0) {
        return std::vector<SomaSolution>();
    }
    auto unique_solns = std::vector<SomaSolution>{};
    for (auto &solution : *solutions) {
        auto found_match = false;
        for (auto &rotation : get_solution_rotations(&solution, dims)) { 
            for (auto &unique_soln : unique_solns) {
                auto is_match = true;
                for (int piece_i = 0; piece_i < unique_soln.size(); piece_i++) {
                    if (rotation[piece_i] != unique_soln[piece_i]) {
                        is_match = false;
                        break;
                    }
                }
                if (is_match) {
                    found_match = true;
                    break;
                }
            }
            if (found_match) {
                break;
            }
        }
        if (!found_match) {
            unique_solns.push_back(SomaSolution(solution));
        }
    }
    return unique_solns;
}

auto get_dims_input(int dims[3]) -> void {
    std::cout << "Enter dimensions separated by newlines. (x*y*z must not exceed 64)\n";
    auto success = false;
    while (!success) {
        std::cout << "x: ";
        std::cin >> dims[0];
        std::cout << "y: ";
        std::cin >> dims[1];
        std::cout << "z: ";
        std::cin >> dims[2];

        auto size = dims[0]*dims[1]*dims[2];
        if (size <= 64) {
            success = true;
        } else {
            std::cout << "That resulted in " << size << " units. Try again.\n"; 
        }
        std::cin.ignore();
    }
}

auto get_reprs_input(int units_required) -> std::vector<uint64_t> {
    std::cout << "Enter bit-representations (big endian, max 64 bits, total 1s must add up to " << units_required << "). press ENTER twice to finish input.\n";
    auto reprs = std::vector<uint64_t>();
    auto total_units = 0;
    while (true) {
        auto input = std::string();
        std::getline(std::cin, input);
        if (input.size() == 0) {
            if (total_units == units_required) {
                break;
            } else {
                std::cout << "Bad number of units. You entered: " << total_units << ", but exactly " << units_required << " were required.\n";
                total_units = 0;
                continue;
            }
        }
        auto bit_repr = 0ul;
        auto i = 0;
        auto good_repr = true;
        for (auto it = input.rbegin(); it < input.rend(); it++, i++) {
            if (*it == '1') {
                bit_repr |= 1ul << i;
                total_units++;
            } else if (*it != '0' || i >= 64) {
                std::cout << "Input invalid. Enter a binary string only with max 64 bits." << '\n';
                good_repr = false;
                break;
            }
        }
        if (good_repr) {
            reprs.push_back(bit_repr);
        }
    }
    return reprs;
}

auto main() -> int {
    int dims[3];
    get_dims_input(dims);
    std::cout << '\n';
    auto reprs = get_reprs_input(dims[0]*dims[1]*dims[2]);
    /*
    auto reprs = std::vector<uint64_t>{
        23ul,
        30ul,
        15ul,
        1043ul,
        24594ul,
        12306ul,
        11ul, 
    };
    */
    std::cout << "Great. Calculating solutions...\n";

    auto offsets = std::vector<int>();
    auto polycubes = std::vector<uint64_t>();
    polycubes.reserve(reprs.size() * 10);

    auto model_space = Voxel::Space{ 
        .space={},
        .dim_x=dims[0],
        .dim_y=dims[1],
        .dim_z=dims[2],
    };

    offsets.push_back(0);
    auto space = model_space;
    space.space = reprs[0];
    Voxel::cullEmptySpace(&space);
    auto positions = Voxel::getAllPositionsInPrism(&space, dims);
    polycubes.insert(polycubes.end(), positions.begin(), positions.end());

    for (int i = 1; i < reprs.size(); i++) {
        offsets.push_back(polycubes.size());
        auto space = model_space;
        space.space = reprs[i];
        Voxel::cullEmptySpace(&space);
        auto perms = Voxel::getAllPermutationsInPrism(&space, dims);
        polycubes.insert(polycubes.end(), perms.begin(), perms.end());
    }

    offsets.push_back(polycubes.size());

    auto solutions = std::vector<SomaSolution>{std::vector<uint64_t>(reprs.size())};
    auto solver = Solver{
        .input=&polycubes,
        .offsets=&offsets,
        .solutions=&solutions,
    };

    backtrack_solve(&solver);

    auto filtered_solns = filter_unique(solver.solutions, dims);

    std::cout << filtered_solns.size() << std::endl;
    return 0;
}