#include <iostream>
#include <fstream>
#include <string>
#include <vector>
#include <regex>
#include <algorithm>

static const std::regex number_regex_full(R"(\d+)");
static const std::regex number_regex_1to3(R"(\b\d{1,3}\b)");

// Find the first number in a line using the given regex
bool find_first_number_in_line(const std::string& s, int& out, const std::regex& rx) {
    std::smatch m;
    if (std::regex_search(s, m, rx)) {
        out = std::stoi(m.str());
        return true;
    }
    return false;
}

// Check if a line contains exactly 24 consecutive 'Ä'
bool has_exactly_24_A(const std::string& s) {
    int count = 0;
    for (size_t i = 0; i <= s.size(); ++i) {
        if (i < s.size() && s[i] == (char)196) {
            count++;
        }
        else {
            if (count == 24) return true; // exact match found
            count = 0; // reset counter
        }
    }
    return false;
}

int main(int argc, char* argv[]) {
    if (argc < 3) {
        std::cerr << "Usage: " << argv[0] << " <inputfile> <outputfile>\n";
        return 1;
    }

    // Read entire file into memory as lines
    std::ifstream infile(argv[1], std::ios::binary);
    if (!infile) {
        std::cerr << "Error opening input file.\n";
        return 1;
    }

    std::ofstream outfile(argv[2], std::ios::binary);
    if (!outfile) {
        std::cerr << "Error opening output file.\n";
        return 1;
    }

    std::vector<std::string> lines;
    std::string line;
    while (std::getline(infile, line)) {
        if (!infile.eof()) line += '\n'; // preserve original line endings
        lines.push_back(line);
    }

    // Detect if document should be modified
    bool has_bbgyro = false;
    bool has_subs = false;
    for (const auto& l : lines) {
        if (!has_bbgyro && l.find("BBGYRS") != std::string::npos) has_bbgyro = true;
        if (!has_subs && l.find("SUBS") != std::string::npos) has_subs = true;
        if (has_bbgyro || has_subs) break;
    }

    // If neither BBGYRO nor SUBS appears, pass file through unmodified
    if (!has_bbgyro && !has_subs) {
        infile.clear();
        infile.seekg(0, std::ios::beg);
        outfile << infile.rdbuf(); // exact byte-for-byte copy
        return 0;
    }

    const std::string marker = "F.L.C.M. %";

    // === 1) Find marker index ===
    bool marker_found = false;
    size_t marker_index = 0;
    for (size_t i = 0; i < lines.size(); ++i) {
        if (lines[i].find(marker) != std::string::npos) {
            marker_found = true;
            marker_index = i;
            break;
        }
    }

    if (!marker_found) {
        // Marker not found, write original file unchanged
        infile.clear();
        infile.seekg(0, std::ios::beg);
        outfile << infile.rdbuf();
        return 0;
    }

    // === 2) Extract gyros from "BBGYRO" line ===
    int gyros = 0;
    bool gyros_found = false;
    size_t bbgyro_index = std::string::npos;
    const std::string bbgyro_token = "BBGYRO";

    for (size_t i = 0; i < lines.size(); ++i) {
        size_t pos = lines[i].find(bbgyro_token);
        if (pos != std::string::npos) {
            bbgyro_index = i;
            std::string tail = lines[i].substr(pos + bbgyro_token.size());
            if (find_first_number_in_line(tail, gyros, number_regex_full)) {
                gyros_found = true;
            }
            break;
        }
    }

    // === 3) Extract total_subs ===
    int total_subs = 0;

    auto find_total_after_start_index = [&](size_t start_index) -> bool {
        for (size_t j = start_index; j < lines.size(); ++j) {
            if (has_exactly_24_A(lines[j])) {
                if (j + 1 < lines.size()) {
                    if (find_first_number_in_line(lines[j + 1], total_subs, number_regex_1to3)) {
                        return true;
                    }
                }
            }
        }
        return false;
        };

    if (gyros_found) {
        find_total_after_start_index(bbgyro_index + 1);
    }
    else {
        // Fallback: second "SUBS"
        int subs_count = 0;
        size_t subs_index = std::string::npos;
        for (size_t i = 0; i < lines.size(); ++i) {
            if (lines[i].find("SUBS") != std::string::npos) {
                subs_count++;
                if (subs_count == 2) {
                    subs_index = i;
                    break;
                }
            }
        }
        if (subs_index != std::string::npos) {
            find_total_after_start_index(subs_index + 1);
        }
    }

    // === 4) Truncate document after the marker ===
    std::vector<std::string> truncated(lines.begin(), lines.begin() + marker_index + 1);

    // === 5) Insert TOTAL SUBS --- diff before first form feed ===
    int diff = total_subs - gyros;
    const std::string insert_line = "\n\n\r        ROLLS USED  ---  " + std::to_string(diff);

    bool inserted = false;
    for (const auto& l : truncated) {
        size_t ff_pos = l.find('\f');
        if (!inserted && ff_pos != std::string::npos) {
            std::string modified = l.substr(0, ff_pos) + insert_line + l.substr(ff_pos);
            outfile << modified;
            inserted = true;
        }
        else {
            outfile << l;
        }
    }

    if (inserted) {
        // === 6) Append a form feed to the very end of the truncated document ===
        outfile << '\f';
    }

    return 0;
}