{ config, lib, pkgs, ... }:
let
  cfg = config.programs.rclone;
  targetName = "rclone";

  mkSystemdDependencyOption =
    { default, ... }: lib.mkOption {
      type = lib.types.attrsOf (lib.types.listOf lib.types.str);
      description = "The systemd services this sync depends on.";
      example = {
        secrets = [
          "sops-nix.service"
        ];
      };
      inherit default;
    };

  mkProvider =
    {
        secretLoader ? ({ ... }: ""),
        envLoader ? ({ ... }: { }),
        configLoader ? ({ ... }: { }),
        options ? {},
        ...
    }: {
      inherit
        secretLoader
        envLoader
        configLoader
        options
      ;
    };

  syncProviders = {
    nextcloud = mkProvider {
      options = lib.types.submodule (
        (mkOwncloudOptions { }));
    };

    proton = mkProvider {};
    manual = mkProvider {};
  };

  syncType = lib.types.submodule (
    { config, name, ... }: {
      options = {
        type = lib.mkOption {
          description = "The type of the sync";
          type = lib.types.enum (builtins.attrNames syncProviders);
          default = "manual";
        };

        autoStart = lib.mkOption {
          type = lib.types.bool;
          description = "Whether to start this sync automatically.";
          default = true;
        };

        providerOptions = lib.mkOption {
          description = "The options of the sync";
          type = lib.types.oneOf [
            (builtins.map
              (provider: provider.options)
              syncProviders)
          ];
        };

        systemdDependencies = mkSystemdDependencyOption {
          default = cfg.systemdDependencies;
        };

        environment = lib.mkOption {
          type = lib.types.attrsOf lib.types.envVar;
          description = "The environment variables to pass to the service.";
          default = {};
        };

        secretsScript = lib.mkOption {
          type = lib.types.lines;
          description = "A script for loading secrets before launching the sync.";
          default = [];
        };

        config = lib.mkOption {
          type = lib.types.attrs;
          description = "The rclone config to use for creating the mount.";
          visible = false;
        };
      };

      config = {
        environment = syncProviders.${config.type}.envLoader config;
        secretsScript = syncProviders.${config.type}.secretLoader config;
        config = syncProviders.${config.type}.configLoader config;
      };
    });
in {
  options = {
    programs.rclone = {
      enable = lib.mkEnableOption "rclone";

      systemdDependencies = mkSystemdDependencyOption {
        default = {};
      };

      configs = lib.mkOption {
        type = lib.types.attrsOf syncType;
        description = "The synchronizations to set up.";
        default = {};
      };
    };
  };

  config = {
    home.packages = lib.optional cfg.enable pkgs.rclone;

    systemd.user = lib.optionalAttrs cfg.enable {
      enable = true;

      services = {
        rclone = {
          Unit = {
            Description = "rclone Starter";
            Documentation = "man:rclone(1)";
          };

          Service = {
            Type = "simple";

            ExecStartPre =
              let
                script = pkgs.writeShellScriptBin "rclone-pre" ''
                  sleep 10
                '';
              in
                (lib.getExe script);

            ExecStart =
              let
                script = pkgs.writeShellScriptBin "rclone" ''
                  systemctl --user start rclone.target
                '';
              in
                (lib.getExe script);
          };
        };
      } // (
        lib.attrsets.concatMapAttrs
        (name: sync:
          let
            serviceName = "rclone-sync-${name}";
          in {
            ${serviceName} = {
              Unit = {
                Description = "${sync.type}";
              };

              Service = {
                Environment = lib.mapAttrsToList
                  (key: val: (lib.escapeShellArg "${key}=${val}"))
                  sync.environment;

                ExecStart =
                  let
                    script = pkgs.writeShellScriptBin serviceName ''
                      ${sync.secretsScript}
                      bash -c echo hello world
                    '';
                  in
                    (lib.getExe script);
              };

              Install = {
                WantedBy = lib.optional sync.autoStart "${targetName}.target";
                After = builtins.concatLists(builtins.attrValues sync.systemdDependencies);
              };
            };
          })
        cfg.configs);

      targets.${targetName} = {
        Unit = {
          Description = "rclone Mounts";
          Documentation = "man:rclone(1)";
        };
      };
    };
  };
}