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

#pragma once

#include "tl/expected.hpp"
#include <algorithm>
#include <array>
#include <cctype>
#include <cstring>
#include <filesystem>
#include <fstream>
#include <iostream>
#include <map>
#include <memory>
#include <memory_resource>
#include <sstream>
#include <string_view>

#include <alloca.h>
#include <cassert>

#include <security/pam_appl.h>
#include <security/pam_modules.h>
#include <sys/stat.h>
#include <syslog.h>
#include <unistd.h>
#include <utility>

#include <rublon/memory.hpp>

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 auto dateStr() {
    std::array< char, 32 > date;
    time_t now;
    time(&now);
    strftime(date.data(), date.size(), "%FT%TZ", gmtime(&now));
    return date;
}

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

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

    inline bool logExists() noexcept {
        return std::unique_ptr< FILE, int (*)(FILE *) >(fopen(logPath(), "r"), fclose).get();
    }

    inline void initLog() noexcept {
        if(not logExists()) {
            auto fp = fopen(logPath(), "w");
            if(fp) {
                fclose(fp);
                chmod(logPath(), S_IRUSR | S_IWUSR | S_IRGRP);
            }
        }
    }

    inline void doLog(LogLevel level, const char * line) noexcept {
        auto fp = std::unique_ptr< FILE, int (*)(FILE *) >(fopen(logPath(), "a+"), fclose);
        if(fp) {
            /// TODO add transaction ID
            fprintf(fp.get(), "%s [%s] %s\n", dateStr().data(), LogLevelNames[( int ) level], line);
            if(syncLogFile)
                sync();
        }
    }
} // 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 {
    inline bool to_bool(std::string_view value) {
        auto * buf        = ( char * ) alloca(value.size() + 1);
        buf[value.size()] = '\0';
        auto asciitolower = [](char in) { return in - ((in <= 'Z' && in >= 'A') ? ('Z' - 'z') : 0); };

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

    enum class Error { OutOfRange, NotANumber };
    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

} // namespace rublon