#include "px5g-openssl.hpp"
#include <array>
#include <iostream>
#include <string>
#include <string_view>
#include <unistd.h>


class argv_view { // TODO(pst): use std::span when available.

private:

    std::basic_string_view<const char *> data;

public:

    argv_view(const argv_view &) = delete;


    argv_view(argv_view &&) = delete;


    auto operator=(const argv_view &) -> argv_view & = delete;


    auto operator=(argv_view &&) -> argv_view & = delete;


    argv_view(const char ** argv, int argc) :
    data{argv, static_cast<size_t>(argc)} {}


    inline auto operator[] (size_t pos) const -> std::string_view
    { return std::string_view{data[pos]}; }


    [[nodiscard]] inline constexpr auto size() const noexcept -> size_t
    { return data.size(); }


    ~argv_view() = default;

};


static const auto default_validity = 30;


auto checkend(const argv_view & argv) -> int;


void eckey(const argv_view & argv);


void rsakey(const argv_view & argv);


void selfsigned(const argv_view & argv);


inline auto parse_int(const std::string_view & arg) -> int
{
    size_t pos;
    int ret = stoi(std::string{arg}, &pos);
    if (pos < arg.size()) {
        throw std::runtime_error("number has trailing char");
    }
    return ret;
}


inline auto parse_curve(const std::string_view & name) -> int
{
    if (name=="P-384") { return NID_secp384r1; }
    if (name=="P-521") { return NID_secp521r1; }
    if (name=="P-256" || name=="secp256r1") { return NID_X9_62_prime256v1; }
    if (name=="secp192r1") { return NID_X9_62_prime192v1; }
    return OBJ_sn2nid(name.data());
    // not: if (curve == 0) { curve = EC_curve_nist2nid(name.c_str()); }
}


auto checkend(const argv_view & argv) -> int
{
    bool use_pem = true;
    std::string crtpath{};
    time_t seconds = 0;

    for (size_t i=2; i<argv.size(); ++i) {
        if (argv[i]=="-der") {
            use_pem = false;
        } else if (argv[i]=="-in") {
            ++i;

            if (i >= argv.size()) {
                throw std::runtime_error("checkend error: -in misses filename");
            }

            if (!crtpath.empty()) {
                if (argv[i] == crtpath) {
                    std::cerr<<"checkend warning: repeated same -in file\n";
                } else {
                    throw std::runtime_error
                                    ("checkend error: more than one -in file");
                }
            }

            crtpath = argv[i];
        }

        else if (argv[i][0]=='-') {
            std::cerr<<"checkend warning: skipping option "<<argv[i]<<std::endl;
        } else { // main option:
            intmax_t num = 0;

            try {
                num = parse_int(argv[i]);
            } catch (...) {
                auto errmsg = std::string{"checkend error: invalid time "};
                errmsg += argv[i];
                std::throw_with_nested(std::runtime_error(errmsg));
            }

            seconds = static_cast<time_t>(num);

            if (num!=static_cast<intmax_t>(seconds)) {
                auto errmsg = std::string{"checkend error: time too big "};
                errmsg += argv[i];
                throw std::runtime_error(errmsg);
            }
        }
    }

    bool valid = checkend(crtpath, seconds, use_pem);
    std::cout<<"Certificate will"<<(valid ? " not " : " ")<<"expire"<<std::endl;

    return (valid ? 0 : 1);
}


void eckey(const argv_view & argv)
{
    bool has_main_option = false;
    bool use_pem = true;
    std::string keypath{};
    int curve = NID_X9_62_prime256v1;

    for (size_t i=2; i < argv.size(); ++i) {
        if (argv[i]=="-der") {
            use_pem = false;
        } else if (argv[i]=="-out") {
            ++i;

            if (i >= argv.size()) {
                throw std::runtime_error("eckey error: -out misses filename");
            }

            if (!keypath.empty()) {
                if (argv[i]==keypath) {
                    std::cerr<<"eckey warning: repeated same -out file\n";
                } else {
                    throw std::runtime_error
                    ("eckey error: more than one -out file");
                }
            }

            keypath = argv[i];
        }

        else if (argv[i][0]=='-') {
            std::cerr<<"eckey warning: skipping option "<<argv[i]<<std::endl;
        } else { //main option:

            if (has_main_option) {
                throw std::runtime_error
                    ("eckey error: more than one main option");
            } //else:
            has_main_option = true;

            curve = parse_curve(argv[i]);
        }
    }

    write_key(gen_eckey(curve), keypath, use_pem);
}


void rsakey(const argv_view & argv)
{
    bool has_main_option = false;
    bool use_pem = true;
    std::string keypath{};
    BN_ULONG exponent = RSA_F4;
    int keysize = rsa_min_modulus_bits;

    for (size_t i=2; i < argv.size(); ++i) {
        if (argv[i]=="-der") {
            use_pem = false;
        } else if (argv[i]=="-3") {
            exponent = 3;
        } else if (argv[i]=="-out") {
            ++i;

            if (i >= argv.size()) {
                throw std::runtime_error("rsakey error: -out misses filename");
            }

            if (!keypath.empty()) {
                if (argv[i]==keypath) {
                    std::cerr<<"rsakey warning: repeated -out file"<<std::endl;
                } else {
                    throw std::runtime_error
                        ("rsakey error: more than one -out file");
                }
            }

            keypath = argv[i];
        }

        else if (argv[i][0]=='-') {
            std::cerr<<"rsakey warning: skipping option "<<argv[i]<<std::endl;
        } else { //main option:

            if (has_main_option) {
                throw std::runtime_error("rsakey error: more than one keysize");
            } //else:
            has_main_option = true;

            try {
                keysize = parse_int(argv[i]);
            } catch (...) {
                std::string errmsg{"rsakey error: invalid keysize "};
                errmsg += argv[i];
                std::throw_with_nested(std::runtime_error(errmsg));
            }
        }
    }

    write_key(gen_rsakey(keysize, exponent), keypath, use_pem);
}


void selfsigned(const argv_view & argv)
{
    bool use_pem = true;
    int days = default_validity;
    std::string keypath{};
    std::string crtpath{};
    std::string subject{};

    bool use_rsa = true;
    int keysize = rsa_min_modulus_bits;
    BN_ULONG exponent = RSA_F4;

    int curve = NID_X9_62_prime256v1;

    for (size_t i=2; i < argv.size(); ++i) {
        if (argv[i]=="-der") {
            use_pem = false;
        } else if (argv[i]=="-days") {
            ++i;
            try {
                days = parse_int(argv[i]);
            } catch (...) {
                std::string errmsg{"selfsigned error: not a number for -days "};
                errmsg += argv[i].substr(4);
                std::throw_with_nested(std::runtime_error(errmsg));
            }
        }

        else if (argv[i]=="-newkey") {
            ++i;

            if (i >= argv.size()) {
                throw std::runtime_error
                    ("selfsigned error: -newkey misses algorithm option");
            }

            static constexpr auto rsa_prefix = std::string_view{"rsa:"};

            if (argv[i]=="ec") {
                use_rsa = false;
            } else if (argv[i].rfind(rsa_prefix, 0) == 0) {
                use_rsa = true;
                try {
                    keysize = parse_int(argv[i].substr(rsa_prefix.size()));
                } catch (...) {
                    std::string errmsg{"selfsigned error: invalid keysize "};
                    errmsg += argv[i].substr(4);
                    std::throw_with_nested(std::runtime_error(errmsg));
                }
            } else {
                throw std::runtime_error("selfsigned error: invalid algorithm");
            }
        }

        else if (argv[i]=="-pkeyopt") {
            ++i;

            if (i >= argv.size()) {
                throw std::runtime_error
                    ("selfsigned error: -pkeyopt misses value");
            }

            static constexpr auto curve_prefix =
                std::string_view{"ec_paramgen_curve:"};

            if (argv[i].rfind(curve_prefix, 0) != 0) {
                throw std::runtime_error("selfsigned error: -pkeyopt invalid");
            }

            curve = parse_curve(argv[i].substr(curve_prefix.size()));
        }

        else if (argv[i]=="-keyout") {
            ++i;

            if (i >= argv.size()) {
                throw std::runtime_error
                    ("selfsigned error: -keyout misses path");
            }

            if (!keypath.empty()) {
                if (argv[i]==keypath) {
                    std::cerr<<"selfsigned warning: repeated -keyout file\n";
                } else {
                    throw std::runtime_error
                        ("selfsigned error: more than one -keyout file");
                }
            }

            keypath = argv[i];
        }

        else if (argv[i]=="-out") {
            ++i;

            if (i >= argv.size()) {
                throw std::runtime_error
                    ("selfsigned error: -out misses filename");
            }

            if (!crtpath.empty()) {
                if (argv[i]==crtpath) {
                    std::cerr<<"selfsigned warning: repeated same -out file\n";
                } else {
                    throw std::runtime_error
                        ("selfsigned error: more than one -out file");
                }
            }

            crtpath = argv[i];
        }

        else if (argv[i]=="-subj") {
            ++i;

            if (i >= argv.size()) {
                throw std::runtime_error
                    ("selfsigned error: -subj misses value");
            }

            if (!subject.empty()) {
                if (argv[i]==subject) {
                    std::cerr<<"selfsigned warning: repeated same -subj\n";
                } else {
                    throw std::runtime_error
                        ("selfsigned error: more than one -subj value");
                }
            }

            subject = argv[i];
        }

        else {
            std::cerr<<"selfsigned warning: skipping option "<<argv[i]<<std::endl;
        }
    }

    auto pkey = use_rsa ? gen_rsakey(keysize, exponent) : gen_eckey(curve);

    selfsigned(pkey, days, subject, crtpath, use_pem);

    if (!keypath.empty()) { write_key(pkey, keypath, use_pem); }
}


auto main(int argc, const char ** argv) -> int
{
    auto args = argv_view{argv, argc};

    auto cmds = std::array{
        std::array<std::string, 2>{"checkend",
            " [-der] [-in certificate_path] [seconds_remaining]"
        },
        std::array<std::string, 2>{"eckey",
            " [-der] [-out key_path] [curve_name]"
        },
        std::array<std::string, 2>{"rsakey",
            " [-der] [-out key_path] [-3] [key_size]"
        },
        std::array<std::string, 2>{"selfsigned",
            " [-der] [-keyout key_path] [-out certificate_path]"
            " [-newkey ec|rsa:key_size] [-pkeyopt ec_paramgen_curve:name]"
            " [-days validity] [-subj /C=.../ST=.../L=.../O=.../CN=.../... ]"
        },
    };

    try {
        if (argc < 2) { throw std::runtime_error("error: no argument"); }

        if (args[1]==cmds[0][0]) {return checkend(args);}

        if (args[1]==cmds[1][0]) { eckey(args); }

        else if (args[1]==cmds[2][0]) { rsakey(args); }

        else if (args[1]==cmds[3][0]) { selfsigned(args); }

        else { throw std::runtime_error("error: argument not recognized"); }
    }

    catch (const std::exception & e)  {

        auto usage = std::string{"usage: \n"}  ;
        for (auto cmd : cmds) {
            usage += std::string{4, ' '} + *argv +" "+ cmd[0] + cmd[1] +"\n";
        }

        std::cerr<<usage<<std::flush;

        auto print_nested =
            [](auto && self, const std::exception & outer, int depth=0) -> void
        {
            std::cerr<<std::string(depth, '\t')<<outer.what()<<std::endl;
            try { std::rethrow_if_nested(outer); }
            catch (const std::exception & inner) { self(self, inner, depth+1); }
        };

        print_nested(print_nested, e);

        return 1;
    }

    catch (...) {
        std::cerr<<*argv<<" unknown error."<<std::endl;
        return 2;
    }

    return 0;
}