wind_power_cal/third_party/drogon_repo/lib/src/HttpUtils.cc

/**
 *
 *  @file HttpUtils.cc
 *  @author An Tao
 *
 *  Copyright 2018, An Tao.  All rights reserved.
 *  https://github.com/an-tao/drogon
 *  Use of this source code is governed by a MIT license
 *  that can be found in the License file.
 *
 *  Drogon
 *
 */

#include "HttpUtils.h"
#include <drogon/utils/Utilities.h>
#include <trantor/utils/Logger.h>
#include <map>
#include <unordered_map>
#include <mutex>

namespace drogon
{
static std::unordered_map<std::string, std::string> customMime;

// https://en.wikipedia.org/wiki/List_of_file_formats
// https://developer.mozilla.org/en-US/docs/Web/HTTP/Basics_of_HTTP/MIME_types/Common_types
// https://www.digipres.org/formats/mime-types/
// https://www.iana.org/assignments/media-types/media-types.xhtml
// content type -> list of corresponding mime types, the first being the default
// (more standard) one + the mime type to return in contentTypeToMime() when not
// empty (mainly to return the charset for text types)
static const std::unordered_map<
    ContentType,
    std::pair<std::vector<std::string_view>, std::string_view>>
    mimeTypeDatabase_{
        {CT_NONE, {{""}, ""}},
        {CT_APPLICATION_OCTET_STREAM, {{"application/octet-stream"}, ""}},
        {CT_APPLICATION_X_FORM, {{"application/x-www-form-urlencoded"}, ""}},
        {CT_MULTIPART_FORM_DATA, {{"multipart/form-data"}, ""}},
        {CT_APPLICATION_GZIP, {{"application/gzip"}, ""}},
        {CT_APPLICATION_JSON,
         {{"application/json"}, "application/json; charset=utf-8"}},
        {CT_APPLICATION_FONT_WOFF, {{"application/font-woff"}, ""}},
        {CT_APPLICATION_FONT_WOFF2, {{"application/font-woff2"}, ""}},
        {CT_APPLICATION_JAVA_ARCHIVE,
         {{"application/java-archive", "application/x-java-archive"}, ""}},
        {CT_APPLICATION_MSWORD, {{"application/msword"}, ""}},
        {CT_APPLICATION_MSWORDX,
         {{"application/"
           "vnd.openxmlformats-officedocument.wordprocessingml.document"},
          ""}},
        {CT_APPLICATION_PDF, {{"application/pdf"}, ""}},
        {CT_APPLICATION_VND_MS_FONTOBJ,
         {{"application/vnd.ms-fontobject"}, ""}},
        {CT_APPLICATION_VND_RAR, {{"application/vnd.rar"}, ""}},
        {CT_APPLICATION_WASM, {{"application/wasm"}, ""}},
        {CT_APPLICATION_X_BZIP, {{"application/x-bzip"}, ""}},
        {CT_APPLICATION_X_BZIP2, {{"application/x-bzip2"}, ""}},
        {CT_APPLICATION_X_7Z, {{"application/x-7z-compressed"}, ""}},
        {CT_APPLICATION_X_HTTPD_PHP, {{"application/x-httpd-php"}, ""}},
        {CT_APPLICATION_X_JAVASCRIPT,
         {{"application/x-javascript"},
          "application/x-javascript; charset=utf-8"}},
        {CT_APPLICATION_X_FONT_OPENTYPE,
         {{"application/x-font-opentype", "font/otf"}, ""}},
        {CT_APPLICATION_X_FONT_TRUETYPE,
         {{"application/x-font-truetype", "font/ttf"}, ""}},
        {CT_APPLICATION_X_TAR, {{"application/x-tar"}, ""}},
        {CT_APPLICATION_X_TGZ, {{"application/x-tgz"}, ""}},
        {CT_APPLICATION_X_XZ, {{"application/x-xz", "application/x-lzma"}, ""}},
        {CT_APPLICATION_XHTML,
         {{"application/xhtml+xml", "application/xhtml"},
          "application/xhtml+xml; charset=utf-8"}},
        {CT_APPLICATION_XML,
         {{"application/xml"}, "application/xml; charset=utf-8"}},
        {CT_APPLICATION_ZIP, {{"application/zip"}, ""}},
        {CT_AUDIO_AAC, {{"audio/aac", "audio/aacp"}, ""}},
        {CT_AUDIO_AC3, {{"audio/ac3"}, ""}},
        {CT_AUDIO_AIFF, {{"audio/aiff", "audio/x-aiff"}, ""}},
        {CT_AUDIO_FLAC, {{"audio/flac"}, ""}},
        {CT_AUDIO_MATROSKA, {{"audio/matroska", "audio/x-matroska"}, ""}},
        {CT_AUDIO_MPEG, {{"audio/mpeg"}, ""}},
        {CT_AUDIO_MPEG4, {{"audio/mp4", "audio/x-m4a"}, ""}},
        {CT_AUDIO_OGG, {{"audio/ogg"}, ""}},
        {CT_AUDIO_WAVE, {{"audio/wav", "audio/x-wav"}, ""}},
        {CT_AUDIO_X_APE, {{"audio/x-ape"}, ""}},
        {CT_AUDIO_X_MS_WMA, {{"audio/x-ms-wma"}, ""}},
        {CT_AUDIO_X_TTA, {{"audio/x-tta"}, ""}},
        {CT_AUDIO_X_WAVPACK, {{"audio/x-wavpack"}, ""}},
        {CT_AUDIO_WEBM, {{"audio/webm"}, ""}},
        {CT_IMAGE_APNG, {{"image/apng"}, ""}},
        {CT_IMAGE_AVIF, {{"image/avif"}, ""}},
        {CT_IMAGE_BMP, {{"image/bmp"}, ""}},
        {CT_IMAGE_GIF, {{"image/gif"}, ""}},
        {CT_IMAGE_ICNS, {{"image/icns"}, ""}},
        {CT_IMAGE_JP2, {{"image/jp2", "image/jpx", "image/jpm"}, ""}},
        {CT_IMAGE_JPG, {{"image/jpeg"}, ""}},
        {CT_IMAGE_PNG, {{"image/png"}, ""}},
        {CT_IMAGE_SVG_XML, {{"image/svg+xml"}, ""}},
        {CT_IMAGE_TIFF, {{"image/tiff"}, ""}},
        {CT_IMAGE_WEBP, {{"image/webp"}, ""}},
        {CT_IMAGE_X_MNG, {{"image/x-mng"}, ""}},
        {CT_IMAGE_X_TGA, {{"image/x-tga", "image/x-targa"}, ""}},
        {CT_IMAGE_XICON, {{"image/vnd.microsoft.icon", "image/x-icon"}, ""}},
        {CT_TEXT_CSS, {{"text/css"}, "text/css; charset=utf-8"}},
        {CT_TEXT_CSV, {{"text/csv"}, "text/csv; charset=utf-8"}},
        {CT_TEXT_HTML, {{"text/html"}, "text/html; charset=utf-8"}},
        {CT_TEXT_JAVASCRIPT,
         {{"text/javascript"}, "text/javascript; charset=utf-8"}},
        {CT_TEXT_PLAIN, {{"text/plain"}, "text/plain; charset=utf-8"}},
        {CT_TEXT_XML, {{"text/xml"}, "text/xml; charset=utf-8"}},
        {CT_TEXT_XSL, {{"text/xsl"}, "text/xsl; charset=utf-8"}},
        {CT_VIDEO_APG, {{"video/apg"}, ""}},
        {CT_VIDEO_AV1, {{"video/av01", "video/av1"}, ""}},
        {CT_VIDEO_QUICKTIME, {{"video/quicktime"}, ""}},
        {CT_VIDEO_MPEG, {{"video/mpeg"}, ""}},
        {CT_VIDEO_MPEG2TS, {{"video/mp2t"}, ""}},
        {CT_VIDEO_MP4, {{"video/mp4"}, ""}},
        {CT_VIDEO_OGG, {{"video/ogg"}, ""}},
        {CT_VIDEO_WEBM, {{"video/webm"}, ""}},
        {CT_VIDEO_X_M4V, {{"video/x-m4v"}, ""}},
        {CT_VIDEO_MATROSKA, {{"video/matroska", "video/x-matroska"}, ""}},
        {CT_VIDEO_X_MSVIDEO, {{"video/x-msvideo"}, ""}},
    };

static const std::unordered_map<std::string_view,
                                std::pair<FileType, ContentType>>
    fileTypeDatabase_{
        {"", {FT_UNKNOWN, CT_CUSTOM}},
        {"aac", {FT_AUDIO, CT_AUDIO_AAC}},
        {"ac3", {FT_AUDIO, CT_AUDIO_AC3}},
        {"aif", {FT_AUDIO, CT_AUDIO_AIFF}},
        {"aifc", {FT_AUDIO, CT_AUDIO_AIFF}},
        {"aiff", {FT_AUDIO, CT_AUDIO_AIFF}},
        {"apg", {FT_AUDIO, CT_VIDEO_APG}},
        {"ape", {FT_AUDIO, CT_AUDIO_X_APE}},
        {"apng", {FT_IMAGE, CT_IMAGE_APNG}},
        {"av1", {FT_MEDIA, CT_VIDEO_AV1}},
        {"avi", {FT_MEDIA, CT_VIDEO_X_MSVIDEO}},
        {"avif", {FT_IMAGE, CT_IMAGE_AVIF}},
        {"bmp", {FT_IMAGE, CT_IMAGE_BMP}},
        {"bz", {FT_ARCHIVE, CT_APPLICATION_X_BZIP}},
        {"bz2", {FT_ARCHIVE, CT_APPLICATION_X_BZIP2}},
        {"css", {FT_DOCUMENT, CT_TEXT_CSS}},
        {"csv", {FT_DOCUMENT, CT_TEXT_CSV}},
        {"doc", {FT_DOCUMENT, CT_APPLICATION_MSWORD}},
        {"docx", {FT_DOCUMENT, CT_APPLICATION_MSWORDX}},
        {"eot", {FT_DOCUMENT, CT_APPLICATION_VND_MS_FONTOBJ}},
        {"flac", {FT_AUDIO, CT_AUDIO_FLAC}},
        {"gif", {FT_MEDIA, CT_IMAGE_GIF}},
        {"gz", {FT_ARCHIVE, CT_APPLICATION_GZIP}},
        {"htm", {FT_DOCUMENT, CT_TEXT_HTML}},
        {"html", {FT_DOCUMENT, CT_TEXT_HTML}},
        {"icns", {FT_IMAGE, CT_IMAGE_ICNS}},
        {"ico", {FT_IMAGE, CT_IMAGE_XICON}},
        {"j2k", {FT_IMAGE, CT_IMAGE_JP2}},
        {"jar", {FT_DOCUMENT, CT_APPLICATION_JAVA_ARCHIVE}},
        {"j2c", {FT_IMAGE, CT_IMAGE_JP2}},
        {"jp2", {FT_IMAGE, CT_IMAGE_JP2}},
        {"jpeg", {FT_IMAGE, CT_IMAGE_JPG}},
        {"jpc", {FT_IMAGE, CT_IMAGE_JP2}},
        {"jpf", {FT_IMAGE, CT_IMAGE_JP2}},
        {"jpg", {FT_IMAGE, CT_IMAGE_JPG}},
        {"jpg2", {FT_IMAGE, CT_IMAGE_JP2}},
        {"jpm", {FT_IMAGE, CT_IMAGE_JP2}},
        {"jpx", {FT_IMAGE, CT_IMAGE_JP2}},
        {"js", {FT_DOCUMENT, CT_TEXT_JAVASCRIPT}},
        {"json", {FT_DOCUMENT, CT_APPLICATION_JSON}},
        {"lzma", {FT_ARCHIVE, CT_APPLICATION_X_XZ}},
        {"m1a", {FT_AUDIO, CT_AUDIO_MPEG}},
        {"m1v", {FT_MEDIA, CT_VIDEO_MPEG}},
        {"m2a", {FT_AUDIO, CT_AUDIO_MPEG}},
        {"m2ts", {FT_MEDIA, CT_VIDEO_MPEG2TS}},
        {"m2v", {FT_MEDIA, CT_VIDEO_MPEG}},
        {"m4a", {FT_AUDIO, CT_AUDIO_MPEG4}},
        {"m4v", {FT_MEDIA, CT_VIDEO_X_M4V}},
        {"mjs", {FT_DOCUMENT, CT_TEXT_JAVASCRIPT}},
        {"mka", {FT_AUDIO, CT_AUDIO_MATROSKA}},
        {"mkv", {FT_MEDIA, CT_VIDEO_MATROSKA}},
        {"mng", {FT_MEDIA, CT_IMAGE_X_MNG}},
        {"mov", {FT_MEDIA, CT_VIDEO_QUICKTIME}},
        {"mp1", {FT_AUDIO, CT_AUDIO_MPEG}},
        {"mp2", {FT_AUDIO, CT_AUDIO_MPEG}},
        {"mp3", {FT_AUDIO, CT_AUDIO_MPEG}},
        {"mp4", {FT_MEDIA, CT_VIDEO_MP4}},
        {"mpa", {FT_AUDIO, CT_AUDIO_MPEG}},
        {"mpe", {FT_MEDIA, CT_VIDEO_MPEG}},
        {"mpeg", {FT_MEDIA, CT_VIDEO_MPEG}},
        {"mpg", {FT_MEDIA, CT_VIDEO_MPEG}},
        {"mpv", {FT_MEDIA, CT_VIDEO_MPEG}},
        {"oga", {FT_AUDIO, CT_AUDIO_OGG}},
        {"ogg", {FT_AUDIO, CT_AUDIO_OGG}},
        {"ogv", {FT_MEDIA, CT_VIDEO_OGG}},
        {"otf", {FT_DOCUMENT, CT_APPLICATION_X_FONT_OPENTYPE}},
        {"pdf", {FT_DOCUMENT, CT_APPLICATION_PDF}},
        {"php", {FT_DOCUMENT, CT_APPLICATION_X_HTTPD_PHP}},
        {"png", {FT_IMAGE, CT_IMAGE_PNG}},
        {"rar", {FT_ARCHIVE, CT_APPLICATION_VND_RAR}},
        {"svg", {FT_IMAGE, CT_IMAGE_SVG_XML}},
        {"tar", {FT_ARCHIVE, CT_APPLICATION_X_TAR}},
        {"targa", {FT_IMAGE, CT_IMAGE_X_TGA}},
        {"tif", {FT_IMAGE, CT_IMAGE_TIFF}},
        {"tiff", {FT_IMAGE, CT_IMAGE_TIFF}},
        {"tga", {FT_IMAGE, CT_IMAGE_X_TGA}},
        {"tgz", {FT_ARCHIVE, CT_APPLICATION_X_TGZ}},
        {"ts", {FT_MEDIA, CT_VIDEO_MPEG2TS}},
        {"tta", {FT_AUDIO, CT_AUDIO_X_TTA}},
        {"ttf", {FT_DOCUMENT, CT_APPLICATION_X_FONT_TRUETYPE}},
        {"txt", {FT_DOCUMENT, CT_TEXT_PLAIN}},
        {"w64", {FT_AUDIO, CT_AUDIO_WAVE}},
        {"wav", {FT_AUDIO, CT_AUDIO_WAVE}},
        {"wave", {FT_AUDIO, CT_AUDIO_WAVE}},
        {"wasm", {FT_DOCUMENT, CT_APPLICATION_WASM}},
        {"weba", {FT_AUDIO, CT_AUDIO_WEBM}},
        {"webm", {FT_MEDIA, CT_VIDEO_WEBM}},
        {"webp", {FT_IMAGE, CT_IMAGE_WEBP}},
        {"wma", {FT_AUDIO, CT_AUDIO_X_MS_WMA}},
        {"woff", {FT_DOCUMENT, CT_APPLICATION_FONT_WOFF}},
        {"woff2", {FT_DOCUMENT, CT_APPLICATION_FONT_WOFF2}},
        {"wv", {FT_AUDIO, CT_AUDIO_X_WAVPACK}},
        {"xht", {FT_DOCUMENT, CT_APPLICATION_XHTML}},
        {"xhtml", {FT_DOCUMENT, CT_APPLICATION_XHTML}},
        {"xml", {FT_DOCUMENT, CT_APPLICATION_XML}},
        {"xsl", {FT_DOCUMENT, CT_TEXT_XSL}},
        {"xz", {FT_ARCHIVE, CT_APPLICATION_X_XZ}},
        {"zip", {FT_ARCHIVE, CT_APPLICATION_ZIP}},
        {"7z", {FT_ARCHIVE, CT_APPLICATION_X_7Z}},
    };

const std::string_view &statusCodeToString(int code)
{
    switch (code)
    {
        case 100:
        {
            static std::string_view sv = "Continue";
            return sv;
        }
        case 101:
        {
            static std::string_view sv = "Switching Protocols";
            return sv;
        }
        case 102:
        {
            static std::string_view sv = "Processing";
            return sv;
        }
        case 103:
        {
            static std::string_view sv = "Early Hints";
            return sv;
        }
        case 200:
        {
            static std::string_view sv = "OK";
            return sv;
        }
        case 201:
        {
            static std::string_view sv = "Created";
            return sv;
        }
        case 202:
        {
            static std::string_view sv = "Accepted";
            return sv;
        }
        case 203:
        {
            static std::string_view sv = "Non-Authoritative Information";
            return sv;
        }
        case 204:
        {
            static std::string_view sv = "No Content";
            return sv;
        }
        case 205:
        {
            static std::string_view sv = "Reset Content";
            return sv;
        }
        case 206:
        {
            static std::string_view sv = "Partial Content";
            return sv;
        }
        case 207:
        {
            static std::string_view sv = "Multi-Status";
            return sv;
        }
        case 208:
        {
            static std::string_view sv = "Already Reported";
            return sv;
        }
        case 226:
        {
            static std::string_view sv = "IM Used";
            return sv;
        }
        case 300:
        {
            static std::string_view sv = "Multiple Choices";
            return sv;
        }
        case 301:
        {
            static std::string_view sv = "Moved Permanently";
            return sv;
        }
        case 302:
        {
            static std::string_view sv = "Found";
            return sv;
        }
        case 303:
        {
            static std::string_view sv = "See Other";
            return sv;
        }
        case 304:
        {
            static std::string_view sv = "Not Modified";
            return sv;
        }
        case 305:
        {
            static std::string_view sv = "Use Proxy";
            return sv;
        }
        case 306:
        {
            static std::string_view sv = "(Unused)";
            return sv;
        }
        case 307:
        {
            static std::string_view sv = "Temporary Redirect";
            return sv;
        }
        case 308:
        {
            static std::string_view sv = "Permanent Redirect";
            return sv;
        }
        case 400:
        {
            static std::string_view sv = "Bad Request";
            return sv;
        }
        case 401:
        {
            static std::string_view sv = "Unauthorized";
            return sv;
        }
        case 402:
        {
            static std::string_view sv = "Payment Required";
            return sv;
        }
        case 403:
        {
            static std::string_view sv = "Forbidden";
            return sv;
        }
        case 404:
        {
            static std::string_view sv = "Not Found";
            return sv;
        }
        case 405:
        {
            static std::string_view sv = "Method Not Allowed";
            return sv;
        }
        case 406:
        {
            static std::string_view sv = "Not Acceptable";
            return sv;
        }
        case 407:
        {
            static std::string_view sv = "Proxy Authentication Required";
            return sv;
        }
        case 408:
        {
            static std::string_view sv = "Request Time-out";
            return sv;
        }
        case 409:
        {
            static std::string_view sv = "Conflict";
            return sv;
        }
        case 410:
        {
            static std::string_view sv = "Gone";
            return sv;
        }
        case 411:
        {
            static std::string_view sv = "Length Required";
            return sv;
        }
        case 412:
        {
            static std::string_view sv = "Precondition Failed";
            return sv;
        }
        case 413:
        {
            static std::string_view sv = "Request Entity Too Large";
            return sv;
        }
        case 414:
        {
            static std::string_view sv = "Request-URI Too Large";
            return sv;
        }
        case 415:
        {
            static std::string_view sv = "Unsupported Media Type";
            return sv;
        }
        case 416:
        {
            static std::string_view sv = "Requested Range Not Satisfiable";
            return sv;
        }
        case 417:
        {
            static std::string_view sv = "Expectation Failed";
            return sv;
        }
        case 418:
        {
            static std::string_view sv = "I'm a Teapot";
            return sv;
        }
        case 421:
        {
            static std::string_view sv = "Misdirected Request";
            return sv;
        }
        case 422:
        {
            static std::string_view sv = "Unprocessable Entity";
            return sv;
        }
        case 423:
        {
            static std::string_view sv = "Locked";
            return sv;
        }
        case 424:
        {
            static std::string_view sv = "Failed Dependency";
            return sv;
        }
        case 425:
        {
            static std::string_view sv = "Too Early";
            return sv;
        }
        case 426:
        {
            static std::string_view sv = "Upgrade Required";
            return sv;
        }
        case 428:
        {
            static std::string_view sv = "Precondition Required";
            return sv;
        }
        case 429:
        {
            static std::string_view sv = "Too Many Requests";
            return sv;
        }
        case 431:
        {
            static std::string_view sv = "Request Header Fields Too Large";
            return sv;
        }
        case 451:
        {
            static std::string_view sv = "Unavailable For Legal Reasons";
            return sv;
        }
        case 500:
        {
            static std::string_view sv = "Internal Server Error";
            return sv;
        }
        case 501:
        {
            static std::string_view sv = "Not Implemented";
            return sv;
        }
        case 502:
        {
            static std::string_view sv = "Bad Gateway";
            return sv;
        }
        case 503:
        {
            static std::string_view sv = "Service Unavailable";
            return sv;
        }
        case 504:
        {
            static std::string_view sv = "Gateway Time-out";
            return sv;
        }
        case 505:
        {
            static std::string_view sv = "HTTP Version Not Supported";
            return sv;
        }
        case 506:
        {
            static std::string_view sv = "Variant Also Negotiates";
            return sv;
        }
        case 507:
        {
            static std::string_view sv = "Insufficient Storage";
            return sv;
        }
        case 508:
        {
            static std::string_view sv = "Loop Detected";
            return sv;
        }
        case 510:
        {
            static std::string_view sv = "Not Extended";
            return sv;
        }
        case 511:
        {
            static std::string_view sv = "Network Authentication Required";
            return sv;
        }
        default:
            if (code >= 100 && code < 200)
            {
                static std::string_view sv = "Informational";
                return sv;
            }
            else if (code >= 200 && code < 300)
            {
                static std::string_view sv = "Successful";
                return sv;
            }
            else if (code >= 300 && code < 400)
            {
                static std::string_view sv = "Redirection";
                return sv;
            }
            else if (code >= 400 && code < 500)
            {
                static std::string_view sv = "Bad Request";
                return sv;
            }
            else if (code >= 500 && code < 600)
            {
                static std::string_view sv = "Server Error";
                return sv;
            }
            else
            {
                static std::string_view sv = "Undefined Error";
                return sv;
            }
    }
}

ContentType getContentType(const std::string &fileName)
{
    std::string extName;
    auto pos = fileName.rfind('.');
    if (pos != std::string::npos)
    {
        extName = fileName.substr(pos + 1);
        transform(extName.begin(),
                  extName.end(),
                  extName.begin(),
                  [](unsigned char c) { return tolower(c); });
    }
    auto it = fileTypeDatabase_.find(extName);
    return (it == fileTypeDatabase_.end()) ? CT_APPLICATION_OCTET_STREAM
                                           : it->second.second;
}

ContentType parseContentType(const std::string_view &contentType)
{
    // Generate map from database for faster query
    static std::unordered_map<std::string_view, ContentType> contentTypeMap_;
    // Thread safe initialization
    static std::once_flag flag;
    std::call_once(flag, []() {
        for (const auto &e : mimeTypeDatabase_)
        {
            for (const auto &type : e.second.first)
                contentTypeMap_[type] = e.first;
        }
    });
    auto ext = contentType.find(';');
    if (ext != std::string_view::npos)
        return parseContentType(contentType.substr(0, ext));
    if (contentType == "application/x-www-form-urlencoded")
        return CT_APPLICATION_X_FORM;
    if (contentType == "multipart/form-data")
        return CT_MULTIPART_FORM_DATA;
    auto it = contentTypeMap_.find(contentType);
    return (it == contentTypeMap_.end()) ? CT_CUSTOM : it->second;
}

FileType parseFileType(const std::string_view &fileExtension)
{
    std::string extName(fileExtension);
    transform(extName.begin(),
              extName.end(),
              extName.begin(),
              [](unsigned char c) { return tolower(c); });
    auto it = fileTypeDatabase_.find(extName);
    return (it == fileTypeDatabase_.end()) ? FT_CUSTOM : it->second.first;
}

FileType getFileType(ContentType contentType)
{
    // Generate map from database for faster query
    static std::unordered_map<ContentType, FileType> fileTypeMap_;
    // Thread safe initialization
    static std::once_flag flag;
    std::call_once(flag, []() {
        for (const auto &e : fileTypeDatabase_)
            fileTypeMap_[e.second.second] = e.second.first;
        fileTypeMap_[CT_NONE] = FT_UNKNOWN;
        fileTypeMap_[CT_CUSTOM] = FT_CUSTOM;
    });
    auto it = fileTypeMap_.find(contentType);
    return (it == fileTypeMap_.end()) ? FT_UNKNOWN : it->second;
}

const std::string_view &contentTypeToMime(ContentType contentType)
{
    auto it = mimeTypeDatabase_.find(contentType);
    return (it == mimeTypeDatabase_.end())
               ? mimeTypeDatabase_.at(CT_APPLICATION_OCTET_STREAM).first.front()
               : (it->second.second.empty() ? it->second.first.front()
                                            : it->second.second);
}

void registerCustomExtensionMime(const std::string &ext,
                                 const std::string &mime)
{
    if (ext.empty())
        return;
    auto &mimeStr = customMime[ext];
    if (!mimeStr.empty())
    {
        LOG_WARN << ext << " has already been registered as type " << mime
                 << ". Overwriting.";
    }
    mimeStr = mime;
}

const std::string_view fileNameToMime(const std::string &fileName)
{
    ContentType internalContentType = getContentType(fileName);
    if (internalContentType != CT_APPLICATION_OCTET_STREAM)
        return contentTypeToMime(internalContentType);

    std::string extName;
    auto pos = fileName.rfind('.');
    if (pos != std::string::npos)
    {
        extName = fileName.substr(pos + 1);
        transform(extName.begin(),
                  extName.end(),
                  extName.begin(),
                  [](unsigned char c) { return tolower(c); });
    }
    auto it = customMime.find(extName);
    if (it == customMime.end())
        return "";
    return it->second;
}

std::pair<ContentType, const std::string_view> fileNameToContentTypeAndMime(
    const std::string &fileName)
{
    ContentType internalContentType = getContentType(fileName);
    if (internalContentType != CT_APPLICATION_OCTET_STREAM)
        return {internalContentType, contentTypeToMime(internalContentType)};

    std::string extName;
    auto pos = fileName.rfind('.');
    if (pos != std::string::npos)
    {
        extName = fileName.substr(pos + 1);
        transform(extName.begin(),
                  extName.end(),
                  extName.begin(),
                  [](unsigned char c) { return tolower(c); });
    }
    auto it = customMime.find(extName);
    if (it == customMime.end())
        return {CT_NONE, ""};
    return {CT_CUSTOM, it->second};
}

const std::vector<std::string_view> &getFileExtensions(ContentType contentType)
{
    // Generate map from database for faster query
    static std::unordered_map<ContentType, std::vector<std::string_view>>
        extensionMap_;
    static std::vector<std::string_view> notFound_;
    // Thread safe initialization
    static std::once_flag flag;
    std::call_once(flag, []() {
        for (const auto &e : fileTypeDatabase_)
            if (!e.first.empty())
                extensionMap_[e.second.second].push_back(e.first);
        // Add deprecated
        extensionMap_[CT_APPLICATION_X_JAVASCRIPT] =
            extensionMap_[CT_TEXT_JAVASCRIPT];
        extensionMap_[CT_TEXT_XML] = extensionMap_[CT_APPLICATION_XML];
    });
    auto it = extensionMap_.find(contentType);
    if (it == extensionMap_.end())
        return notFound_;
    return it->second;
}

}  // namespace drogon