Add some of the options from NixOS ollama module

Particularly: host, port, home, models and environmentVariables, to make
ollama module compatible with one from nixpkgs.

Except: sandbox, writablePaths, acceleration, openFirewall.

modules/services/ollama.nix

@@ -21,20 +21,75 @@ in {
         description = "This option specifies the ollama package to use.";
       };
 
-      exec = mkOption {
+      host = mkOption {
         type = types.str;
-        default = "ollama";
-        description = "Ollama command/binary to execute.";
+        default = "127.0.0.1";
+        example = "0.0.0.0";
+        description = ''
+          The host address which the ollama server HTTP interface listens to.
+        '';
+      };
+
+      port = mkOption {
+        type = types.port;
+        default = 11434;
+        example = 11111;
+        description = ''
+          Which port the ollama server listens to.
+        '';
+      };
+
+      home = lib.mkOption {
+        type = types.str;
+        default = "%S/ollama";
+        example = "/home/foo";
+        description = ''
+          The home directory that the ollama service is started in.
+
+          See also `services.ollama.writablePaths` and `services.ollama.sandbox`.
+        '';
+      };
+
+      models = mkOption {
+        type = types.str;
+        default = "%S/ollama/models";
+        example = "/path/to/ollama/models";
+        description = ''
+          The directory that the ollama service will read models from and download new models to.
+        '';
+      };
+
+      environmentVariables = mkOption {
+        type = types.attrsOf types.str;
+        default = { };
+        example = {
+          OLLAMA_LLM_LIBRARY = "cpu";
+          HIP_VISIBLE_DEVICES = "0,1";
+        };
+        description = ''
+          Set arbitrary environment variables for the ollama service.
+
+          Be aware that these are only seen by the ollama server (launchd daemon),
+          not normal invocations like `ollama run`.
+          Since `ollama run` is mostly a shell around the ollama server, this is usually sufficient.
+        '';
       };
     };
   };
 
   config = mkIf cfg.enable {
+
     environment.systemPackages = [ cfg.package ];
     launchd.daemon.ollama = {
       path = [ config.environment.systemPath ];
-      serviceConfig.ProgramArguments =
-        [ "${cfg.package}/bin/${cfg.exec}" "serve" ];
+
+      environment = cfg.environmentVariables // {
+        HOME = cfg.home;
+        OLLAMA_MODELS = cfg.models;
+        OLLAMA_HOST = "${cfg.host}:${toString cfg.port}";
+      };
+
+      serviceConfig.ProgramArguments = [ "${cfg.package}/bin/ollama" "serve" ];
       serviceConfig.RunAtLoad = true;
     };
   };