#include "aoc.h"
#include <algorithm>

namespace aoc2016 {

static void get_number(const char** pp, uint32_t* d) {
  const char* p = *pp;
  while (*p >= '0' && *p <= '9') {
    *d = *d * 10 + *p - '0';
    p++;
  }
  *pp = p;
}

struct ipdigit {
  uint32_t ds[2] = {0};

  void print() const noexcept { printf("%u-%u\n", ds[0], ds[1]); }
  ipdigit(line_view lv) {
    const char* p = lv.line;
    int i{0};
    while (p < lv.line + lv.length) {
      if (*p >= '0' && *p <= '9') {
        get_number(&p, ds + i);
        i++;
      }
      p++;
    }
  }

  friend bool operator<(ipdigit ip1, ipdigit ip2) {
    return ip1.ds[0] < ip2.ds[0] ? true : ip1.ds[0] > ip2.ds[0] ? false : ip1.ds[1] < ip2.ds[1];
  }
};

static bool merge(ipdigit& ip, const ipdigit& ipx) {
  if (ip.ds[1] >= ipx.ds[1]) {
    return true;
  }
  if (ip.ds[1] < ipx.ds[1] && ip.ds[1] + 1 >= ipx.ds[0]) {
    ip.ds[1] = ipx.ds[1];
    return true;
  }
  return false;
}

static std::vector<ipdigit> merge(const std::vector<ipdigit>& ips) {
  std::vector<ipdigit> ds;
  ipdigit ip = ips[0];
  for (size_t i = 1; i < ips.size(); i++) {
    if (!merge(ip, ips[i])) {
      ds.push_back(ip);
      ip = ips[i];
    }
  }
  ds.push_back(ip);
  return ds;
}

static size_t count(std::vector<ipdigit>& ips) {
  size_t c{0};
  for (size_t i = 1; i < ips.size(); i++) {
    c += ips[i].ds[0] - ips[i - 1].ds[1] - 1;
  }
  uint32_t max{UINT32_MAX};
  auto& last = ips[ips.size() - 1];
  c += max - last.ds[1];
  return c;
}

std::pair<int64_t, int64_t> day20(line_view file) {
  std::vector<ipdigit> ips;
  per_line(file, [&ips](line_view lv) {
    ips.emplace_back(lv);
    return true;
  });

  std::sort(ips.begin(), ips.end());
  auto ds = merge(ips);
  // printf("%zu\n", count(ds));
  // for (auto ip : ds) {
  //   ip.print();
  // }

  return {0, count(ds)};
}
} // namespace aoc2016