Add PostgreSQL environment

env/postgresql.nix

@@ -0,0 +1,28 @@
+{ pkgs ? import <nixpkgs> { } }:
+
+with pkgs;
+
+let
+  sql_file = "data/db.sql";
+  data_dir = "$(pwd)/.pgdata";
+
+in mkShell {
+  buildInputs = [ postgresql ];
+
+  shellHook = ''
+    trap "kill 0" EXIT
+    export PGDATA="${data_dir}"
+    export PGHOST="${data_dir}"
+
+    if [ ! -d ${data_dir} ]; then
+      initdb --auth-local=trust --no-locale --encoding=UTF8
+    fi
+
+    if ! pg_ctl status; then
+      pg_ctl start -o "--unix_socket_directories=${data_dir} --listen_addresses='''"
+    fi
+
+    psql -d postgres -f ${sql_file}
+    alias psql='psql -d postgres'
+  '';
+}