add nix shell file to start invidious and database

nix/clipious.nix

@@ -0,0 +1,66 @@
+{ pkgs, ci ? false}:
+
+let
+
+ helpers = {
+   postgres = {
+      setup = builtins.readFile ./helpers/postgres/init_db.sh;
+      clean = builtins.readFile ./helpers/postgres/clean.sh;
+      packages = pkgs: [ pkgs.postgresql ];
+   };
+
+   invidious = {
+     setup = builtins.readFile ./helpers/invidious/setup.sh;
+     clean = "pkill invidious";
+     packages = pkgs: [ pkgs.invidious ];
+   };
+
+ };
+in
+{
+ helpers = helpers;
+
+ packages =
+   builtins.concatLists [
+   (helpers.postgres.packages pkgs)
+   (helpers.invidious.packages pkgs)
+ ];
+
+ prepareShell = {setupScripts ? [], cleanupScripts ? [] }: ''
+    ######################################################################
+    # Create a diretory for the generated artifacts                      #
+    ######################################################################
+
+    mkdir .nix-shell
+    export NIX_SHELL_DIR=$PWD/.nix-shell
+
+    ''
+    + helpers.postgres.setup
+    + helpers.invidious.setup
+    +
+    builtins.concatStringsSep "\n" setupScripts
+    + ''
+
+    #clean up will be triggered once the shell exits
+    trap \
+    "''
+    + helpers.postgres.clean
+    + helpers.invidious.clean
+    + builtins.concatStringsSep "\n" cleanupScripts
+    +
+    ''
+        ########################################################
+        # Delete `.nix-shell` directory                        #
+        # ----------------------------------                   #
+        # The first  step is going  back to the  project root, #
+        # otherwise `.nix-shell`  won't get deleted.     #
+        ########################################################
+        cd $PWD
+        rm -rf $PGDATA
+        cd $PWD
+        rm -rf $NIX_SHELL_DIR
+    " \
+    EXIT
+    '';
+
+}