#include <cstdint>

#include <string>
#include <array>
#include <stack>

#include <fstream>
#include <iostream>

#include <filesystem>

std::string get_file_contents(std::ifstream& file_stream) {
    std::string file_string;

    file_stream.seekg(0, std::ios::end);
    file_string.resize(file_stream.tellg());
    file_stream.seekg(0, std::ios::beg);

    file_stream.read(&file_string[0], file_string.size());

    return file_string;
}

std::string get_brainfuck_code(const std::string& file) {
    std::string code;

    for (auto c : file) {
        switch (c) {
        case '>': case '<':
        case '+': case '-':
        case '.': case ',':
        case '[': case ']':
            code.push_back(c);
        }
    }

    return code;
}

template<typename value_type, std::size_t size>
struct bf_context_t {
    std::array<value_type, size> cells;
    std::stack<std::size_t> scope;
    std::uintptr_t ptr;
};

int main(int argc, char* argv[]) {
    if (argc < 2) {
        std::cout << "Usage: " << argv[0] << " [BRAINFUCK FILE]" << std::endl;
        return 1;
    }

    const std::string file_path = argv[1];

    if (!std::filesystem::exists(file_path)) {
        std::cout << "Could not find file." << std::endl;
        return 1;
    }

    std::ifstream file_stream(file_path);

    if (!file_stream) {
        std::cout << "Could not open file." << std::endl;
        return 1;
    }

    const std::string file_contents = get_file_contents(file_stream);
    const std::string bf_code = get_brainfuck_code(file_contents);

    // by default, std::cin skips whitespace
    std::cin >> std::noskipws;

    auto ctx = bf_context_t<std::uint8_t, 30'000>{};

    for (auto ip = 0; ip < bf_code.length(); ++ip) {
        switch (bf_code[ip]) {
            case '>': ++ctx.ptr; break;
            case '<': --ctx.ptr; break;
            case '+': ++ctx.cells[ctx.ptr]; break;
            case '-': --ctx.cells[ctx.ptr]; break;
            case '.': std::cout << (char)ctx.cells[ctx.ptr]; break;
            case ',': std::cin >> ctx.cells[ctx.ptr]; break;
            case '[': ctx.scope.push(ip); break;
            case ']': if (ctx.cells[ctx.ptr]) ip = ctx.scope.top() - 1; ctx.scope.pop(); break;
        }
    }
}