rublon-ssh/PAM/ssh/include/rublon/utils.hpp

#pragma once

#include <rublon/memory.hpp>
#include <rublon/static_string.hpp>
#include <rublon/stdlib.hpp>

#include <fcntl.h>
#include <sys/stat.h>
#include <syslog.h>
#include <unistd.h>
#include <utility>

#include <security/pam_appl.h>
#include <security/pam_modules.h>

namespace rublon {
inline bool fileGood(const std::filesystem::path & path) {
    std::ifstream file(path);
    return file.good();
}

template < typename T >
inline bool readFile(const std::filesystem::path & path, T & destination) {
    if(not fileGood(path))
        return false;

    std::ifstream file(path);
    file.seekg(0, std::ios::end);
    size_t size = file.tellg();
    destination.resize(size);
    file.seekg(0);
    file.read(&destination[0], size);
    return true;
}

enum class LogLevel { Debug, Info, Warning, Error };

inline StaticString< 32 > dateStr() {
    StaticString< 32 > date;
    time_t now;
    time(&now);
    strftime(date.data(), date.capacity(), "%FT%TZ", gmtime(&now));
    return date;
}

constexpr const char * LogLevelNames[]{"Debug", "Info", "Warning", "Error"};
LogLevel g_level                = LogLevel::Debug;
constexpr bool syncLogFile      = true;
static const char * application = "";

namespace details {
    std::pmr::string osName(std::pmr::memory_resource * mr) {
        memory::MonotonicStackResource< 8 * 1024 > stackResource;

        std::ifstream file(std::filesystem::path{"/etc/os-release"});
        if(not file.good())
            return {"unknown", mr};

        std::pmr::string line{&stackResource};
        line.reserve(100);

        while(std::getline(file, line)) {
            std::pmr::string _key{&stackResource};
            std::pmr::string _value{&stackResource};

            if(!line.length())
                continue;

            if(line[0] == '#' || line[0] == ';')
                continue;

            auto posEqual = line.find('=');
            _key          = line.substr(0, posEqual);
            _value        = line.substr(posEqual + 1);

            if(_key == "PRETTY_NAME") {
                _value.erase(std::remove_if(_value.begin(), _value.end(), [](auto ch) { return ch == '"'; }), _value.end());
                return {_value, mr};
            }
        }

        return {"unknown", mr};
    }

    constexpr const char * logPath() {
        constexpr auto path = "/var/log/rublon-ssh.log";
        return path;
    }

    inline void touch(const char * filename) {
        close(open(filename, O_CREAT | O_RDWR, 0640));
    }

    inline void mkdir(const char * dirname) {
        ::mkdir(dirname, O_CREAT | O_RDWR);
    }

    inline bool exists(const char * filename) {
        return access(filename, F_OK) == 0;
    }

    inline bool logMissing() noexcept {
        return not exists(logPath());
    }

    inline const char * initLog(const char * app = nullptr) noexcept {
        if(logMissing()) {
            touch(logPath());
        }
        if(not app)
            application = app;
        return logPath();
    }

    inline void doLog(LogLevel level, const char * line) noexcept {
        auto fp = std::unique_ptr< FILE, int (*)(FILE *) >(fopen(initLog(), "a+"), fclose);
        if(fp) {
            /// TODO add transaction ID
            fprintf(
              fp.get(), "%s %s[%s] %s\n", dateStr().c_str(), application == nullptr ? "" : application, LogLevelNames[( int ) level], line);
            if(syncLogFile)
                sync();
        }
        // openlog ("auth", LOG_CONS | LOG_PID | LOG_NDELAY, LOG_AUTH);
        // syslog (LOG_INFO, "[%s] %s", "pam_rublon", line);
        // closelog ();
    }
} // namespace details

inline void log(LogLevel level, const char * line) noexcept {
    if(level < g_level)
        return;
    details::doLog(level, line);
}

template < typename... Ti >
void log(LogLevel level, const char * fmt, Ti &&... ti) noexcept {
    if(level < g_level)
        return;
    constexpr auto maxEntryLength = 1000;
    std::array< char, maxEntryLength > line;
    snprintf(line.data(), maxEntryLength, fmt, std::forward< Ti >(ti)...);
    details::doLog(level, line.data());
}

class PrintUser {
  public:
    template < typename Printer >
    PrintUser(Printer & p) : _impl{std::make_unique< ModelImpl >(p)} {}

  private:
    struct model {
        virtual ~model();
        virtual void print(std::string_view line) const = 0;
    };

    template < typename Printer_T >
    struct ModelImpl : public model {
        ModelImpl(Printer_T & printer) : _printer{printer} {}
        void print(std::string_view line) const override {
            _printer.print(line);
        }
        Printer_T & _printer;
    };

    std::unique_ptr< model > _impl;
};

namespace conv {
    enum class Error { OutOfRange, NotANumber };

    inline bool to_bool(std::string_view userinput) {
        if(userinput.size() > 16) {
            // todo return optional
            return false;
        }
        std::array< char, 16 > buf{};
        auto asciitolower = [](char in) { return in - ((in <= 'Z' && in >= 'A') ? ('Z' - 'z') : 0); };

        std::transform(userinput.cbegin(), userinput.cend(), buf.data(), asciitolower);
        return strcmp(buf.data(), "true") == 0;
    }

    inline tl::expected< std::uint32_t, Error > to_uint32(std::string_view userinput) noexcept {
        try {
            return std::stoi(userinput.data());
        } catch(const std::invalid_argument & e) {
            return tl::make_unexpected(Error::NotANumber);
        } catch(const std::out_of_range & e) {
            return tl::make_unexpected(Error::OutOfRange);
        }
    }
} // namespace conv

namespace details {
    static inline std::string_view ltrim(std::string_view s) {
        while(s.length() && std::isspace(*s.begin()))
            s.remove_prefix(1);
        return s;
    }

    static inline std::string_view rtrim(std::string_view s) {
        while(s.length() && std::isspace(*s.rbegin()))
            s.remove_suffix(1);
        return s;
    }

    static inline std::string_view trim(std::string_view s) {
        return ltrim(rtrim(s));
    }

    template < typename Headers >
    inline void headers(std::string_view data, Headers & headers) {
        memory::StrictMonotonic_4k_HeapResource stackResource;
        std::pmr::string tmp{&stackResource};

        std::istringstream resp{};
        resp.rdbuf()->pubsetbuf(const_cast< char * >(data.data()), data.size());

        while(std::getline(resp, tmp) && !(trim(tmp).empty())) {
            auto line  = std::string_view(tmp);
            auto index = tmp.find(':', 0);
            if(index != std::string::npos) {
                headers.insert({//
                  typename Headers::key_type{trim(line.substr(0, index)), headers.get_allocator()},
                  typename Headers::mapped_type{trim(line.substr(index + 1)), headers.get_allocator()}});
            }
        }
    }

} // namespace details

template < class InputIterator, class OutputIterator, class UnaryOperator, class Pred >
OutputIterator transform_if(InputIterator first1, InputIterator last1, OutputIterator result, UnaryOperator op, Pred pred) {
    while(first1 != last1) {
        if(pred(*first1)) {
            *result = op(*first1);
            ++result;
        }
        ++first1;
    }
    return result;
}

struct ci_less {
    template < typename S >
    bool operator()(const S & s1, const S & s2) const {
        return std::lexicographical_compare(
          s1.cbegin(), s1.cend(), s2.cbegin(), s2.cend(), [](const auto & c1, const auto & c2) { return tolower(c1) < tolower(c2); });
    }
};

} // namespace rublon