add nix flake

flake.nix

@@ -0,0 +1,67 @@
+{
+  description = "Cardano DB Sync";
+
+  inputs = {
+    haskell-nix.url = "github:input-output-hk/haskell.nix";
+    nixpkgs.url = "github:NixOS/nixpkgs/nixos-20.09";
+    utils.url = "github:numtide/flake-utils";
+  };
+
+  outputs = { self, nixpkgs, utils, haskell-nix, ... }:
+    (utils.lib.eachSystem [ "x86_64-linux" "x86_64-darwin" ] (system:
+      let
+        legacyPackages = import ./nix {
+          inherit system;
+          ownHaskellNix = haskell-nix.legacyPackages.${system};
+          gitrev = self.rev or "dirty";
+        };
+
+        lib = nixpkgs.lib;
+        sources = import ./nix/sources.nix { };
+        iohkNix = import sources.iohk-nix { inherit system; };
+        environments = iohkNix.cardanoLib.environments;
+        environmentName = "testnet";
+
+        eachEnv = lib.flip lib.pipe [
+          (lib.forEach (builtins.attrNames environments))
+          lib.listToAttrs
+        ];
+
+        config = env:
+          { pkgs, ... }: {
+            services.cardano-db-sync = rec {
+              enable = true;
+              cluster = env;
+              environment = environments.${env};
+              logConfig = iohkNix.cardanoLib.defaultExplorerLogConfig;
+              stateDir = "/local";
+              extended = true;
+              package = pkgs.cardano-db-sync-extended;
+            };
+          };
+
+        evaluated = env:
+          lib.nixosSystem {
+            inherit system;
+            pkgs = legacyPackages;
+            modules = [ ./nix/nixos/cardano-db-sync-service.nix (config env) ];
+          };
+
+        packages = eachEnv (env:
+          lib.nameValuePair "cardano-db-sync-extended-${env}"
+          (legacyPackages.runCommand "cardano-db-sync-extended-entrypoint"
+            { } ''
+              install -Dm0777 ${
+                (evaluated env).config.services.cardano-db-sync.script
+              } $out/bin/cardano-db-sync-extended-entrypoint
+            ''));
+      in {
+        inherit environments evaluated legacyPackages packages;
+
+        apps = eachEnv (env:
+          lib.nameValuePair "cardano-db-sync-extended-${env}" (utils.lib.mkApp {
+            drv = packages."cardano-db-sync-extended-${env}";
+            exePath = "/bin/cardano-db-sync-extended-entrypoint";
+          }));
+      }));
+}

nix/default.nix

@@ -3,12 +3,13 @@
 , config ? {}
 , sourcesOverride ? {}
 , gitrev ? null
+, ownHaskellNix ? null
 }:
 let
   sources = import ./sources.nix { inherit pkgs; }
     // sourcesOverride;
   iohkNix = import sources.iohk-nix {};
-  haskellNix = import sources."haskell.nix" {};
+  haskellNix = if ownHaskellNix != null then ownHaskellNix else import sources."haskell.nix" {};
   # use our own nixpkgs if it exists in our sources,
   # otherwise use iohkNix default nixpkgs.
   nixpkgs = if (sources ? nixpkgs)

repl.nix

@@ -0,0 +1 @@
+builtins.getFlake (toString ./.)