{config, pkgs}:

let

  cfg = config.services.httpd;
  
  startingDependency = if config.services.gw6c.enable then "gw6c" else "network-interfaces";

  httpd = pkgs.apacheHttpd;


  documentRoot = if cfg.documentRoot != null then cfg.documentRoot else
    pkgs.runCommand "empty" {} "ensureDir $out";


  # Names of modules from ${httpd}/modules that we want to load.
  apacheModules = 
    [ # HTTP authentication mechanisms: basic and digest.
      "auth_basic" "auth_digest"

      # Authentication: is the user who he claims to be?
      "authn_file" "authn_dbm" "authn_anon" "authn_alias"

      # Authorization: is the user allowed access?
      "authz_user" "authz_groupfile" "authz_host"

      # Other modules.
      "ext_filter" "include" "log_config" "env" "mime_magic"
      "cern_meta" "expires" "headers" "usertrack" /* "unique_id" */ "setenvif"
      "mime" "dav" "status" "autoindex" "asis" "info" "cgi" "dav_fs"
      "vhost_alias" "negotiation" "dir" "imagemap" "actions" "speling"
      "userdir" "alias" "rewrite"
    ] ++ pkgs.lib.optional cfg.enableSSL "ssl_module";
    

  loggingConf = ''
    ErrorLog ${cfg.logDir}/error_log

    LogLevel notice

    LogFormat "%h %l %u %t \"%r\" %>s %b \"%{Referer}i\" \"%{User-Agent}i\"" combined
    LogFormat "%h %l %u %t \"%r\" %>s %b" common
    LogFormat "%{Referer}i -> %U" referer
    LogFormat "%{User-agent}i" agent

    CustomLog ${cfg.logDir}/access_log common
  '';


  browserHacks = ''
    BrowserMatch "Mozilla/2" nokeepalive
    BrowserMatch "MSIE 4\.0b2;" nokeepalive downgrade-1.0 force-response-1.0
    BrowserMatch "RealPlayer 4\.0" force-response-1.0
    BrowserMatch "Java/1\.0" force-response-1.0
    BrowserMatch "JDK/1\.0" force-response-1.0
    BrowserMatch "Microsoft Data Access Internet Publishing Provider" redirect-carefully
    BrowserMatch "^WebDrive" redirect-carefully
    BrowserMatch "^WebDAVFS/1.[012]" redirect-carefully
    BrowserMatch "^gnome-vfs" redirect-carefully
  '';


  sslConf = ''
    Listen ${toString cfg.httpsPort}

    SSLSessionCache dbm:${cfg.stateDir}/ssl_scache

    SSLMutex  file:${cfg.stateDir}/ssl_mutex

    SSLRandomSeed startup builtin
    SSLRandomSeed connect builtin

    <VirtualHost _default_:${toString cfg.httpsPort}>

        SSLEngine on

        SSLCipherSuite ALL:!ADH:!EXPORT56:RC4+RSA:+HIGH:+MEDIUM:+LOW:+SSLv2:+EXP:+eNULL

        SSLCertificateFile @sslServerCert@
        SSLCertificateKeyFile @sslServerKey@

        #   MSIE compatability.
        SetEnvIf User-Agent ".*MSIE.*" \
                 nokeepalive ssl-unclean-shutdown \
                 downgrade-1.0 force-response-1.0

    </VirtualHost>
  '';


  mimeConf = ''
    TypesConfig ${httpd}/conf/mime.types

    AddType application/x-x509-ca-cert .crt
    AddType application/x-pkcs7-crl    .crl

    <IfModule mod_mime_magic.c>
        MIMEMagicFile ${httpd}/conf/magic
    </IfModule>

    AddEncoding x-compress Z
    AddEncoding x-gzip gz tgz
  '';


  documentRootConf = ''
    DocumentRoot "${documentRoot}"

    <Directory "${documentRoot}">
        Options Indexes FollowSymLinks
        AllowOverride None
        Order allow,deny
        Allow from all
    </Directory>
  '';

  
  httpdConf = pkgs.writeText "httpd.conf" ''
  
    ServerRoot ${httpd}

    ServerAdmin ${cfg.adminAddr}

    ServerName ${cfg.hostName}:${toString cfg.httpPort}

    PidFile ${cfg.stateDir}/httpd.pid

    <IfModule prefork.c>
        MaxClients           150
        MaxRequestsPerChild  0
    </IfModule>

    Listen ${toString cfg.httpPort}

    User ${cfg.user}
    Group ${cfg.group}

    ${let f = name: "LoadModule ${name}_module ${httpd}/modules/mod_${name}.so\n";
      in pkgs.lib.concatStrings (map f apacheModules)
    }

    ${if cfg.enableUserDir then ''
    
      UserDir public_html
      
      <Directory "/home/*/public_html">
          AllowOverride FileInfo AuthConfig Limit Indexes
          Options MultiViews Indexes SymLinksIfOwnerMatch IncludesNoExec
          <Limit GET POST OPTIONS>
              Order allow,deny
              Allow from all
          </Limit>
          <LimitExcept GET POST OPTIONS>
              Order deny,allow
              Deny from all
          </LimitExcept>
      </Directory>
      
    '' else ""}

    AddHandler type-map var

    <Files ~ "^\.ht">
        Order allow,deny
        Deny from all
    </Files>

    ${mimeConf}
    ${loggingConf}
    ${browserHacks}

    Include ${httpd}/conf/extra/httpd-default.conf
    Include ${httpd}/conf/extra/httpd-autoindex.conf
    Include ${httpd}/conf/extra/httpd-multilang-errordoc.conf
    Include ${httpd}/conf/extra/httpd-languages.conf
    
    ${if cfg.enableSSL then sslConf else ""}

    <Directory />
        Options FollowSymLinks
        AllowOverride None
    </Directory>

    ${documentRootConf}

    ${
      let makeDirConf = elem: ''
            Alias ${elem.urlPath} ${elem.dir}/
            <Directory ${elem.dir}>
                Order allow,deny
                Allow from all
                AllowOverride None
            </Directory>
          '';
      in pkgs.lib.concatStrings (map makeDirConf cfg.servedDirs)
    }
  '';

    
in

{

  name = "httpd";
  
  users = [
    { name = cfg.user;
      description = "Apache httpd user";
    }
  ];

  groups = [
    { name = cfg.group;
    }
  ];

  # Statically verify the syntactic correctness of the generated
  # httpd.conf.
  buildHook = "${httpd}/bin/httpd -f ${httpdConf} -t";

  job = ''
    description "Apache HTTPD"

    start on ${startingDependency}/started
    stop on shutdown

    start script
      mkdir -m 0700 -p ${cfg.stateDir}
      mkdir -m 0700 -p ${cfg.logDir}
    end script

    respawn ${httpd}/bin/httpd -f ${httpdConf} -DNO_DETACH
  '';

}