#include <fstream>
#include <vector>
#include <algorithm>
#include <ranges>
#include <numeric>
#include <cmath>
#include <utility>

#include "fmt/format.h"

using levels_t  = std::vector<std::int32_t>;
using reports_t = std::vector<levels_t>;

auto main([[maybe_unused]]int argc, [[maybe_unused]]char const* argv[]) -> int {
    constexpr auto filename = "./dat/24/ex/02.txt";
    std::ifstream strm{filename, std::ios::in | std::ios::binary};
    if (!strm.is_open()) {
        fmt::print("Error opening file: {}\n", filename);
        return 1;
    }

    reports_t reports{};

    levels_t tmp{};
    std::string str{};
    while (strm) {
        auto const c = char(strm.peek());
        if (std::isdigit(c)) {
            str += char(strm.get());
            continue;
        }
        if (c == ' ' && !str.empty()) {
            tmp.emplace_back(std::stoi(str));
            str.clear();
        }
        if (c == '\n' && !str.empty()) {
            tmp.emplace_back(std::stoi(str));
            reports.emplace_back(std::move(tmp));
            str.clear();
        }
        strm.get();
    }

    // auto diff = reports | std::views::transform([](auto const& levels) {
    //     return levels | std::views::slide(2) | std::views::transform([](auto pair) {
    //         return pair[1] - pair[0];
    //     });
    // });

    auto diff = reports | std::views::transform([](auto const& levels) {
        return levels | std::views::adjacent_transform<2>([](auto const& a, auto const& b) {
            return b - a;
        });
    });

    // condition: all increasing or all decreasing.
    auto incdec = diff | std::views::filter([](auto const& levels) {
        auto const n = std::ranges::all_of(levels, [](auto v) { return v < 0; });
        auto const p = std::ranges::all_of(levels, [](auto v) { return v > 0; });
        return n || p;
    });

    // condition: Any two adjacent levels differ by at least one and at most three.
    auto adjdiff = incdec | std::views::filter([](auto const& levels){
        return std::ranges::all_of(levels, [](auto v) {
            return std::abs(v) <= 3;
        });
    });

    auto const safe_reports = std::ranges::distance(adjdiff);

    fmt::print("Part A: {}\n", safe_reports);

    for (auto levels : reports) {
        for (auto level : levels) {
            fmt::print("{} ", level);
        }
        fmt::print("\n");
    }

    fmt::print("--------------------------------------------------------------------------------\n");

    for (auto levels : diff) {
        for (auto level : levels) {
            fmt::print("{} ", level);
        }
        fmt::print("\n");
    }

    return 0;
}