feat(nix): add support for running external services through services…

…-flake (#6377)

.gitignore

@@ -263,4 +263,9 @@ result*
 node_modules/
 
 # cypress credentials
-creds.json
+creds.json
+
+/.direnv
+
+# Nix services data
+/data

docs/try_local_system.md

@@ -15,6 +15,10 @@ Check the Table Of Contents to jump to the relevant section.
 - [Run hyperswitch using Docker Compose](#run-hyperswitch-using-docker-compose)
   - [Running additional services](#running-additional-services)
 - [Set up a development environment using Docker Compose](#set-up-a-development-environment-using-docker-compose)
+- [Set up a Nix development environment](#set-up-a-nix-development-environment)
+   - [Install Nix](#install-nix)
+   - [Using external services through Nix](#using-external-services-through-nix)
+   - [Develop in a Nix environment (coming soon)](#develop-in-a-nix-environment-coming-soon)
 - [Set up a Rust environment and other dependencies](#set-up-a-rust-environment-and-other-dependencies)
   - [Set up dependencies on Ubuntu-based systems](#set-up-dependencies-on-ubuntu-based-systems)
   - [Set up dependencies on Windows (Ubuntu on WSL2)](#set-up-dependencies-on-windows-ubuntu-on-wsl2)
@@ -166,6 +170,43 @@ Once the services have been confirmed to be up and running, you can proceed with
    If the command returned a `200 OK` status code, proceed with
    [trying out our APIs](#try-out-our-apis).
 
+## Set up a Nix development environment
+
+A Nix development environment simplifies the setup of required project dependencies. This is available for MacOS, Linux and WSL2 users.
+
+### Install nix
+
+We recommend that you install Nix using [the DetSys nix-installer][detsys-nixos-installer], which automatically enables flakes.
+
+As an **optional** next step, if you are interested in using Nix to manage your dotfiles and local packages, you can setup [nixos-unified-template][nixos-unified-template-repo].
+
+### Using external services through Nix
+
+Once Nix is installed, you can use it to manage external services via `flakes`. More services will be added soon.
+
+- Run below command in hyperswitch directory
+
+   ```shell
+   nix run .#ext-services
+   ```
+
+This will start the following services using `process-compose`
+- PostgreSQL
+   - Creates database and an user to be used by the application
+- Redis
+
+### Develop in a Nix environment (coming soon)
+
+Nix development environment ensures all the required project dependencies, including both the tools and services are readily available, eliminating the need for manual setup.
+
+Run below command in hyperswitch directory
+
+   ```shell
+   nix develop
+   ```
+
+**NOTE:** This is a work in progress, and only a selected commands are available at the moment. Look in `flake.nix` (hyperswitch-shell) for a full list of packages.
+
 ## Set up a Rust environment and other dependencies
 
 If you are using `nix`, please skip the setup dependencies step and jump to
@@ -681,3 +722,5 @@ To explore more of our APIs, please check the remaining folders in the
 [refunds-create]: https://www.postman.com/hyperswitch/workspace/hyperswitch-development/request/25176162-4d1315c6-ac61-4411-8f7d-15d4e4e736a1
 [refunds-retrieve]: https://www.postman.com/hyperswitch/workspace/hyperswitch-development/request/25176162-137d6260-24f7-4752-9e69-26b61b83df0d
 [connector-specific-details]: https://docs.google.com/spreadsheets/d/e/2PACX-1vQWHLza9m5iO4Ol-tEBx22_Nnq8Mb3ISCWI53nrinIGLK8eHYmHGnvXFXUXEut8AFyGyI9DipsYaBLG/pubhtml?gid=748960791&single=true
+[detsys-nixos-installer]: https://nixos.asia/en/install
+[nixos-unified-template-repo]: https://github.com/juspay/nixos-unified-template#on-non-nixos

flake.nix

@@ -8,10 +8,14 @@
     # TODO: Move away from these to https://github.com/juspay/rust-flake
     cargo2nix.url = "github:cargo2nix/cargo2nix/release-0.11.0";
     rust-overlay.url = "github:oxalica/rust-overlay";
+
+    process-compose-flake.url = "github:Platonic-Systems/process-compose-flake";
+    services-flake.url = "github:juspay/services-flake";
   };
 
   outputs = inputs:
     inputs.flake-parts.lib.mkFlake { inherit inputs; } {
+      imports = [ inputs.process-compose-flake.flakeModule ];
       systems = inputs.nixpkgs.lib.systems.flakeExposed;
       perSystem = { self', pkgs, lib, system, ... }:
         let
@@ -27,17 +31,47 @@
           devShells.default = pkgs.mkShell {
             name = "hyperswitch-shell";
             packages = with pkgs; [
+              just
+              nixd
               openssl
               pkg-config
-              exa
-              fd
               rust-bin.stable.${rustVersion}.default
             ] ++ lib.optionals stdenv.isDarwin [
               # arch might have issue finding these libs.
               frameworks.CoreServices
               frameworks.Foundation
             ];
           };
+
+          /* For running external services
+              - Redis
+              - Postgres
+          */
+          process-compose."ext-services" =
+            let 
+              developmentToml = lib.importTOML ./config/development.toml;
+              databaseName = developmentToml.master_database.dbname;
+              databaseUser = developmentToml.master_database.username;
+              databasePass = developmentToml.master_database.password;
+            in
+            {
+              imports = [ inputs.services-flake.processComposeModules.default ];
+              services.redis."r1".enable = true;
+              /* Postgres
+                  - Create an user and grant all privileges
+                  - Create a database
+              */
+              services.postgres."p1" = {
+                enable = true;
+                initialScript = {
+                  before = "CREATE USER ${databaseUser} WITH PASSWORD '${databasePass}' SUPERUSER CREATEDB CREATEROLE INHERIT LOGIN;";
+                  after = "GRANT ALL PRIVILEGES ON DATABASE ${databaseName} to ${databaseUser};";
+                };
+                initialDatabases = [
+                  { name = databaseName; }
+                ];
+              };
+            };
         };
     };
 }