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

let
  cfg = config.crans.reverseProxy;

  formatJSON = pkgs.formats.json { };

  allowAll = formatJSON.generate "allow_all.json" {
    bots = [
      {
        name = "allow_all";
        path_regex = ".*";
        action = "ALLOW";
      }
    ];
  };

  open_graph = formatJSON.generate "opengraph.json" {
    openGraph = [
      {
        enabled = true;
        considerHost = true;
        ttl = "24h";
      }
    ];
  };

  mainTld = "org";
  otherTld = [
    "fr"
    "eu"
  ];

  inherit (lib)
    literalExpression
    mkEnableOption
    mkIf
    mkOption
    types
    ;
in

{
  options.crans.reverseProxy = {
    enable = mkEnableOption "Configuration du reverseproxy.";

    virtualHosts = mkOption {
      type = types.attrsOf (
        types.submodule {
          options = {
            serverAliases = mkOption {
              type = types.listOf types.str;
              default = [ ];
              example = [
                "everything"
                "voyager"
              ];
              description = ''
                Déclaration des alias.
              '';
            };

            proxyPass = mkOption {
              type = types.nullOr types.str;
              default = null;
              description = ''
                Indique la destination à proxy.
              '';
              example = "172.16.10.128:8000";
            };

            serveLocalFiles = mkOption {
              type = types.nullOr types.path;
              default = null;
              description = ''
                Chemin vers un dossier à exposer statiquement.
              '';
              example = "/var/local/adopter-un-manchot";
            };

            globalRedirect = mkOption {
              type = types.nullOr types.str;
              default = null;
              description = ''
                Si définie, toutes les requêtes sont redirigées (via 301) sur cet hôte.
              '';
              example = "perso.crans.org/club";
            };

            anubisConfig = mkOption {
              type = types.nullOr types.str;
              default = null;
              description = ''
                Chemin du fichier de configuration
              '';
              example = "/var/www/anubis.conf";
            };

            anubisOpenGraph = mkOption {
              type = types.bool;
              default = true;
              description = ''
                Activer openGraph pour l'indexation et l'embedding
              '';
            };

            httpOnly = mkOption {
              type = types.bool;
              default = false;
              description = ''
                Interdit les connexions en https
              '';
              example = "true";
            };

            proxyWebsockets = mkOption {
              type = types.bool;
              default = false;
              description = ''
                Activer les websockets
              '';
              example = "true";
            };
          };
        }
      );

      default = { };

      example = literalExpression ''
        {
          "framadate" = {
            host = "176.16.10.128:8000";
            serverAliases = [
              "everything"
              "voyager"
            ]
          };
        };
      '';
      description = "Déclaration des machines.";
    };
  };

  config = {
    systemd.services = lib.mapAttrs (vhostName: vhostConfig: {
      wantedBy = [ "multi-user.target" ];
    }) cfg.virtualHosts;

    services = mkIf cfg.enable {
      anubis = {
        defaultOptions.group = "nginx";
        instances = lib.mapAttrs (
          vhostName: vhostConfig:
          mkIf (vhostConfig.anubisConfig != null) {
            enable = true;
            settings = {
              BIND = "/run/anubis/anubis-${vhostName}/socket.sock";
              BIND_NETWORK = "unix";
              METRICS_BIND = "/run/anubis/anubis-${vhostName}/anubis-${vhostName}-metrics.sock";
              TARGET = "unix:///run/nginx/nginx-${vhostName}.sock";
              COOKIE_DOMAIN = "crans.org";
              REDIRECT_DOMAINS = "${vhostName}.crans.org";
              SOCKET_MODE = "0660";
              # OpenGraph config
              OG_PASSTHROUGH = vhostConfig.anubisOpenGraph;
              OG_EXPIRY_TIME = "24h";
              OG_CACHE_CONSIDER_HOST = true;
              # Policy config
              POLICY_FNAME = vhostConfig.anubisConfig;
            };
          }
        ) cfg.virtualHosts;
      };

      nginx =
        let
          configVhost =
            vhostName: vhostConfig:
            let
              sslConf = {
                enableACME = !vhostConfig.httpOnly;
                forceSSL = !vhostConfig.httpOnly;
                rejectSSL = vhostConfig.httpOnly;
              };

              # Conf pour l’host en entrès
              entryExtraConf = {
                extraConfig = ''
                  set_real_ip_from 172.16.0.0/16;
                  set_real_ip_from fd00::/56;
                  real_ip_header X-Real-Ip;
                '';
              }
              // sslConf;
              # Conf supplémentaire pour le proxy principal
              vhostExtraConf =
                if vhostConfig.anubisConfig != null then
                  # Il reçoit les requêtes d’Anubis
                  {
                    listen = [
                      { addr = "unix:/run/nginx/nginx-${vhostName}.sock"; }
                    ];
                    extraConfig = ''
                      set_real_ip_from unix:;
                      real_ip_header X-Real-IP;
                    '';
                  }
                else
                  # Il est en entrée
                  entryExtraConf;

              # Les alias : vhostName × otherTld U serverAliases × allTld
              aliases =
                lib.foldr
                  (
                    tld: acc:
                    acc
                    ++ (lib.foldr (alias: acc: acc ++ [ "${alias}.crans.${tld}" ]) [
                      "${vhostName}.crans.${tld}"
                    ] vhostConfig.serverAliases)
                  )
                  (lib.foldr (alias: acc: acc ++ [ "${alias}.crans.${mainTld}" ]) [ ] vhostConfig.serverAliases)
                  otherTld;
            in
            {
              # Configuration du service à proxy.
              "${vhostName}" = vhostExtraConf // {
                serverName = "${vhostName}.crans.${mainTld}";
                locations."/" = mkIf (vhostConfig.proxyPass != null) {
                  proxyPass = "http://${vhostConfig.proxyPass}";
                  proxyWebsockets = vhostConfig.proxyWebsockets;
                };
                root = vhostConfig.serveLocalFiles;
                globalRedirect = vhostConfig.globalRedirect;
              };

              # Entrée d’Anubis
              "${vhostName}-anubis" = mkIf (vhostConfig.anubisConfig != null) (
                entryExtraConf
                // {
                  serverName = "${vhostName}.crans.${mainTld}";
                  locations."/" = {
                    proxyPass = "http://unix:/run/anubis/anubis-${vhostName}/socket.sock";
                    proxyWebsockets = vhostConfig.proxyWebsockets;
                  };
                  extraConfig = entryExtraConf.extraConfig + ''
                    access_log /var/log/nginx/anubis.access.log;
                    error_log /var/log/nginx/anubis.error.log;
                  '';
                }
              );
            }
            # Les alias
            // lib.mergeAttrsList (
              lib.map (alias: {
                "${vhostName}-alias-${alias}" = sslConf // {
                  serverName = alias;
                  globalRedirect = vhostConfig.globalRedirect or "${vhostName}.crans.${mainTld}";
                };
              }) aliases
            );
        in
        {
          enable = true;
          virtualHosts = lib.concatMapAttrs configVhost cfg.virtualHosts;
        };
    };
  };
}