{ lib, config, ... }:
with lib;
let
  cfg = config.services.phpApplication;
  cfgByEnv = lists.groupBy (x: x.websiteEnv) (builtins.attrValues cfg);
in
{
  options = {
    services.phpApplication = with types; mkOption {
      default = {};
      description = ''
        php applications to define
        '';
      type = attrsOf (submodule {
        options = {
          varDir = mkOption {
            type = nullOr path;
            description = ''
              Path to application’s vardir.
              '';
          };
          mode = mkOption {
            type = str;
            default = "0700";
            description = ''
              Mode to apply to the vardir
              '';
          };
          phpSession = mkOption {
            type = bool;
            default = true;
            description = "Handle phpsession files separately in vardir";
          };
          websiteEnv = mkOption {
            type = str;
            description = ''
              website instance name to use
              '';
          };
          httpdUser = mkOption {
            type = str;
            default = config.services.httpd.user;
            description = ''
              httpd user to run the prestart scripts as.
              '';
          };
          httpdGroup = mkOption {
            type = str;
            default = config.services.httpd.group;
            description = ''
              httpd group to run the prestart scripts as.
              '';
          };
          app = mkOption {
            type = path;
            description = ''
              Path to application root
              '';
          };
          webappName = mkOption {
            type = nullOr str;
            description = ''
              Alias name for the app, to be used in services.websites.webappDirs
              '';
          };
          webRoot = mkOption {
            type = nullOr path;
            description = ''
              Path to the web root path of the application. May differ from the application itself (usually a subdirectory)
              '';
          };
          preStartActions = mkOption {
            type = listOf str;
            default = [];
            description = ''
              List of actions to run as apache user at preStart when
              whatchFiles or app dir changed.
              '';
          };
          serviceDeps = mkOption {
            type = listOf str;
            default = [];
            description = ''
              List of systemd services this application depends on
              '';
          };
          watchFiles = mkOption {
            type = listOf path;
            default = [];
            description = ''
              Path to other files to watch to trigger preStart scripts
              '';
          };
        };
      });
    };
  };

  config = {
    services.websites.env = attrsets.mapAttrs' (name: cfgs: attrsets.nameValuePair
      name {
        modules = [ "proxy_fcgi" ];
        watchPaths = builtins.concatLists (map (c: c.watchFiles) cfgs);
      }
    ) cfgByEnv;

    services.websites.webappDirs = attrsets.mapAttrs' (name: icfg: attrsets.nameValuePair
      icfg.webappName icfg.webRoot
    ) (attrsets.filterAttrs (n: v: !isNull v.webappName && !isNull v.webRoot) cfg);

    systemd.services = attrsets.mapAttrs' (name: icfg: attrsets.nameValuePair
      "phpfpm-${name}" {
        after = lib.mkAfter icfg.serviceDeps;
        wants = icfg.serviceDeps;
        preStart = lib.mkAfter (optionalString (!isNull icfg.varDir) ''
          watchFilesChanged() {
            ${optionalString (builtins.length icfg.watchFiles == 0) "return 0"}
            [ ! -f "${icfg.varDir}"/watchedFiles ] \
              || ! sha512sum -c --status ${icfg.varDir}/watchedFiles
          }
          appDirChanged() {
            [ ! -f "${icfg.varDir}/currentWebappDir" -o \
              "${icfg.app}" != "$(cat ${icfg.varDir}/currentWebappDir 2>/dev/null)" ]
          }
          updateWatchFiles() {
            ${optionalString (builtins.length icfg.watchFiles == 0) "return 0"}
            sha512sum ${builtins.concatStringsSep " " icfg.watchFiles} > ${icfg.varDir}/watchedFiles
          }

          if watchFilesChanged || appDirChanged; then
            pushd ${icfg.app} > /dev/null
            ${builtins.concatStringsSep "\n  " (map (c: "/run/wrappers/bin/sudo -u ${icfg.httpdUser} ${c}") icfg.preStartActions) }
            popd > /dev/null
            echo -n "${icfg.app}" > ${icfg.varDir}/currentWebappDir
            updateWatchFiles
          fi
        '');
      }
    ) cfg;

    system.activationScripts = attrsets.mapAttrs' (name: icfg: attrsets.nameValuePair
      name {
        deps = [];
        text = optionalString (!isNull icfg.varDir) ''
          install -m ${icfg.mode} -o ${icfg.httpdUser} -g ${icfg.httpdGroup} -d ${icfg.varDir}
          '' + optionalString (icfg.phpSession) ''
          install -m 0700 -o ${icfg.httpdUser} -g ${icfg.httpdGroup} -d ${icfg.varDir}/phpSessions
          '';
      }
    ) cfg;
  };
}