{ config, lib, pkgs, ... }:

with lib;

let

  cfg = config.services.tomcat;
  tomcat = cfg.package;
in

{

  ###### interface

  options = {

    services.tomcat = {

      enable = mkOption {
        default = false;
        description = "Whether to enable Apache Tomcat";
      };

      package = mkOption {
        type = types.package;
        default = pkgs.tomcat7;
        example = lib.literalExample "pkgs.tomcat8";
        description = ''
          Which tomcat package to use.
        '';
      };

      baseDir = mkOption {
        default = "/var/tomcat";
        description = "Location where Tomcat stores configuration files, webapplications and logfiles";
      };

      extraGroups = mkOption {
        default = [];
        example = [ "users" ];
        description = "Defines extra groups to which the tomcat user belongs.";
      };

      user = mkOption {
        default = "tomcat";
        description = "User account under which Apache Tomcat runs.";
      };

      group = mkOption {
        default = "tomcat";
        description = "Group account under which Apache Tomcat runs.";
      };

      javaOpts = mkOption {
        default = "";
        description = "Parameters to pass to the Java Virtual Machine which spawns Apache Tomcat";
      };

      catalinaOpts = mkOption {
        default = "";
        description = "Parameters to pass to the Java Virtual Machine which spawns the Catalina servlet container";
      };

      sharedLibs = mkOption {
        default = [];
        description = "List containing JAR files or directories with JAR files which are libraries shared by the web applications";
      };

      commonLibs = mkOption {
        default = [];
        description = "List containing JAR files or directories with JAR files which are libraries shared by the web applications and the servlet container";
      };

      webapps = mkOption {
        default = [ tomcat ];
        description = "List containing WAR files or directories with WAR files which are web applications to be deployed on Tomcat";
      };

      virtualHosts = mkOption {
        default = [];
        description = "List consisting of a virtual host name and a list of web applications to deploy on each virtual host";
      };

      logPerVirtualHost = mkOption {
        default = false;
        description = "Whether to enable logging per virtual host.";
      };

      jdk = mkOption {
        default = pkgs.jdk;
        description = "Which JDK to use.";
      };

      axis2 = {

        enable = mkOption {
          default = false;
          description = "Whether to enable an Apache Axis2 container";
        };

        services = mkOption {
          default = [];
          description = "List containing AAR files or directories with AAR files which are web services to be deployed on Axis2";
        };

      };

    };

  };


  ###### implementation

  config = mkIf config.services.tomcat.enable {

    users.extraGroups = singleton
      { name = "tomcat";
        gid = config.ids.gids.tomcat;
      };

    users.extraUsers = singleton
      { name = "tomcat";
        uid = config.ids.uids.tomcat;
        description = "Tomcat user";
        home = "/homeless-shelter";
        extraGroups = cfg.extraGroups;
      };

    systemd.services.tomcat = {
      description = "Apache Tomcat server";
      wantedBy = [ "multi-user.target" ];
      after = [ "network-interfaces.target" ];
      serviceConfig.Type = "oneshot";
      serviceConfig.RemainAfterExit = true;

      preStart = ''
        # Create the base directory
        mkdir -p ${cfg.baseDir}

        # Create a symlink to the bin directory of the tomcat component
        ln -sfn ${tomcat}/bin ${cfg.baseDir}/bin

        # Create a conf/ directory
        mkdir -p ${cfg.baseDir}/conf
        chown ${cfg.user}:${cfg.group} ${cfg.baseDir}/conf

        # Symlink the config files in the conf/ directory (except for catalina.properties and server.xml)
        for i in $(ls ${tomcat}/conf | grep -v catalina.properties | grep -v server.xml)
        do
            ln -sfn ${tomcat}/conf/$i ${cfg.baseDir}/conf/`basename $i`
        done

        # Create subdirectory for virtual hosts
        mkdir -p ${cfg.baseDir}/virtualhosts

        # Create a modified catalina.properties file
        # Change all references from CATALINA_HOME to CATALINA_BASE and add support for shared libraries
        sed -e 's|''${catalina.home}|''${catalina.base}|g' \
            -e 's|shared.loader=|shared.loader=''${catalina.base}/shared/lib/*.jar|' \
            ${tomcat}/conf/catalina.properties > ${cfg.baseDir}/conf/catalina.properties

        # Create a modified server.xml which also includes all virtual hosts
        sed -e "/<Engine name=\"Catalina\" defaultHost=\"localhost\">/a\  ${
                     toString (map (virtualHost: ''<Host name=\"${virtualHost.name}\" appBase=\"virtualhosts/${virtualHost.name}/webapps\" unpackWARs=\"true\" autoDeploy=\"true\" xmlValidation=\"false\" xmlNamespaceAware=\"false\" >${if cfg.logPerVirtualHost then ''<Valve className=\"org.apache.catalina.valves.AccessLogValve\" directory=\"logs/${virtualHost.name}\"  prefix=\"${virtualHost.name}_access_log.\" pattern=\"combined\" resolveHosts=\"false\"/>'' else ""}</Host>'') cfg.virtualHosts)}" \
            ${tomcat}/conf/server.xml > ${cfg.baseDir}/conf/server.xml

        # Create a logs/ directory
        mkdir -p ${cfg.baseDir}/logs
        chown ${cfg.user}:${cfg.group} ${cfg.baseDir}/logs
        ${if cfg.logPerVirtualHost then
           toString (map (h: ''
                                mkdir -p ${cfg.baseDir}/logs/${h.name}
                                chown ${cfg.user}:${cfg.group} ${cfg.baseDir}/logs/${h.name}
                             '') cfg.virtualHosts) else ''''}

        # Create a temp/ directory
        mkdir -p ${cfg.baseDir}/temp
        chown ${cfg.user}:${cfg.group} ${cfg.baseDir}/temp

        # Create a lib/ directory
        mkdir -p ${cfg.baseDir}/lib
        chown ${cfg.user}:${cfg.group} ${cfg.baseDir}/lib

        # Create a shared/lib directory
        mkdir -p ${cfg.baseDir}/shared/lib
        chown ${cfg.user}:${cfg.group} ${cfg.baseDir}/shared/lib

        # Create a webapps/ directory
        mkdir -p ${cfg.baseDir}/webapps
        chown ${cfg.user}:${cfg.group} ${cfg.baseDir}/webapps

        # Symlink all the given common libs files or paths into the lib/ directory
        for i in ${tomcat} ${toString cfg.commonLibs}
        do
            if [ -f $i ]
            then
                # If the given web application is a file, symlink it into the common/lib/ directory
                ln -sfn $i ${cfg.baseDir}/lib/`basename $i`
            elif [ -d $i ]
            then
                # If the given web application is a directory, then iterate over the files
                # in the special purpose directories and symlink them into the tomcat tree

                for j in $i/lib/*
                do
                    ln -sfn $j ${cfg.baseDir}/lib/`basename $j`
                done
            fi
        done

        # Symlink all the given shared libs files or paths into the shared/lib/ directory
        for i in ${toString cfg.sharedLibs}
        do
            if [ -f $i ]
            then
                # If the given web application is a file, symlink it into the common/lib/ directory
                ln -sfn $i ${cfg.baseDir}/shared/lib/`basename $i`
            elif [ -d $i ]
            then
                # If the given web application is a directory, then iterate over the files
                # in the special purpose directories and symlink them into the tomcat tree

                for j in $i/shared/lib/*
                do
                    ln -sfn $j ${cfg.baseDir}/shared/lib/`basename $j`
                done
            fi
        done

        # Symlink all the given web applications files or paths into the webapps/ directory
        for i in ${toString cfg.webapps}
        do
            if [ -f $i ]
            then
                # If the given web application is a file, symlink it into the webapps/ directory
                ln -sfn $i ${cfg.baseDir}/webapps/`basename $i`
            elif [ -d $i ]
            then
                # If the given web application is a directory, then iterate over the files
                # in the special purpose directories and symlink them into the tomcat tree

                for j in $i/webapps/*
                do
                    ln -sfn $j ${cfg.baseDir}/webapps/`basename $j`
                done

                # Also symlink the configuration files if they are included
                if [ -d $i/conf/Catalina ]
                then
                    for j in $i/conf/Catalina/*
                    do
                        mkdir -p ${cfg.baseDir}/conf/Catalina/localhost
                        ln -sfn $j ${cfg.baseDir}/conf/Catalina/localhost/`basename $j`
                    done
                fi
            fi
        done

        ${toString (map (virtualHost: ''
          # Create webapps directory for the virtual host
          mkdir -p ${cfg.baseDir}/virtualhosts/${virtualHost.name}/webapps

          # Modify ownership
          chown ${cfg.user}:${cfg.group} ${cfg.baseDir}/virtualhosts/${virtualHost.name}/webapps

          # Symlink all the given web applications files or paths into the webapps/ directory
          # of this virtual host
          for i in "${if virtualHost ? webapps then toString virtualHost.webapps else ""}"
          do
              if [ -f $i ]
              then
                  # If the given web application is a file, symlink it into the webapps/ directory
                  ln -sfn $i ${cfg.baseDir}/virtualhosts/${virtualHost.name}/webapps/`basename $i`
              elif [ -d $i ]
              then
                  # If the given web application is a directory, then iterate over the files
                  # in the special purpose directories and symlink them into the tomcat tree

                  for j in $i/webapps/*
                  do
                      ln -sfn $j ${cfg.baseDir}/virtualhosts/${virtualHost.name}/webapps/`basename $j`
                  done

                  # Also symlink the configuration files if they are included
                  if [ -d $i/conf/Catalina ]
                  then
                      for j in $i/conf/Catalina/*
                      do
                          mkdir -p ${cfg.baseDir}/conf/Catalina/${virtualHost.name}
                          ln -sfn $j ${cfg.baseDir}/conf/Catalina/${virtualHost.name}/`basename $j`
                      done
                  fi
              fi
          done

          ''
        ) cfg.virtualHosts) }

        # Create a work/ directory
        mkdir -p ${cfg.baseDir}/work
        chown ${cfg.user}:${cfg.group} ${cfg.baseDir}/work

        ${if cfg.axis2.enable then
            ''
            # Copy the Axis2 web application
            cp -av ${pkgs.axis2}/webapps/axis2 ${cfg.baseDir}/webapps

            # Turn off addressing, which causes many errors
            sed -i -e 's%<module ref="addressing"/>%<!-- <module ref="addressing"/> -->%' ${cfg.baseDir}/webapps/axis2/WEB-INF/conf/axis2.xml

            # Modify permissions on the Axis2 application
            chown -R ${cfg.user}:${cfg.group} ${cfg.baseDir}/webapps/axis2

            # Symlink all the given web service files or paths into the webapps/axis2/WEB-INF/services directory
            for i in ${toString cfg.axis2.services}
            do
                if [ -f $i ]
                then
                    # If the given web service is a file, symlink it into the webapps/axis2/WEB-INF/services
                    ln -sfn $i ${cfg.baseDir}/webapps/axis2/WEB-INF/services/`basename $i`
                elif [ -d $i ]
                then
                    # If the given web application is a directory, then iterate over the files
                    # in the special purpose directories and symlink them into the tomcat tree

                    for j in $i/webapps/axis2/WEB-INF/services/*
                    do
                        ln -sfn $j ${cfg.baseDir}/webapps/axis2/WEB-INF/services/`basename $j`
                    done

                    # Also symlink the configuration files if they are included
                    if [ -d $i/conf/Catalina ]
                    then
                        for j in $i/conf/Catalina/*
                        do
                            ln -sfn $j ${cfg.baseDir}/conf/Catalina/localhost/`basename $j`
                        done
                    fi
                fi
            done
            ''
        else ""}
      '';

      script = ''
          ${pkgs.su}/bin/su -s ${pkgs.bash}/bin/sh ${cfg.user} -c 'CATALINA_BASE=${cfg.baseDir} JAVA_HOME=${cfg.jdk} JAVA_OPTS="${cfg.javaOpts}" CATALINA_OPTS="${cfg.catalinaOpts}" ${tomcat}/bin/startup.sh'
      '';

      postStop = ''
        echo "Stopping tomcat..."
        CATALINA_BASE=${cfg.baseDir} JAVA_HOME=${cfg.jdk} ${pkgs.su}/bin/su -s ${pkgs.bash}/bin/sh ${cfg.user} -c ${tomcat}/bin/shutdown.sh
      '';

    };

  };

}