{
  description = "PostgreSQL";

  inputs.nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable";

  outputs = { self, nixpkgs, ... }@inputs:
  let
    pkgsFor = system: import nixpkgs { inherit system; };

    shellHook = ''
      CONFIG_FILE=./config/config.yaml

      if [ -f "$CONFIG_FILE" ]; then
        DB_USER=$(yq -r ".database.user" "$CONFIG_FILE")
        DB_PASSWORD=$(yq -r ".database.password" "$CONFIG_FILE")
        DB_PORT=$(yq -r ".database.port" "$CONFIG_FILE")
        DB_NAME=$(yq -r ".database.database" "$CONFIG_FILE")
      else
        echo "config.yaml not found, using defaults."
        exit
      fi

      : "$${DB_USER:=$${USER}}"
      : "$${DB_PASSWORD:=password}"
      : "$${DB_PORT:=5432}"
      : "$${DB_NAME:=postgres}"

      export PGDATA="$PWD/postgres-data-nix"
      export PGHOST="$PGDATA"

      mkdir -p "$PGDATA"
      chmod 700 "$PGDATA"

      mkdir -p "$PWD/.log"
      chmod 700 "$PWD/.log"

      if [ ! -f "$PGDATA/PG_VERSION" ]; then
        echo "Initializing database..."
        initdb -D "$PGDATA" > .log/postgres.log 2>&1

        echo "unix_socket_directories = '$PGDATA'" >> "$PGDATA/postgresql.conf"
        echo "listen_addresses = '127.0.0.1'" >> "$PGDATA/postgresql.conf"

        pg_ctl -D "$PGDATA" -l .log/postgres.log -o "-k $PGDATA -p $DB_PORT" start

        sleep 1

        psql --dbname postgres -v ON_ERROR_STOP=1 <<EOSQL > .log/postgres.log 2>&1
        DO \$\$ 
        BEGIN
          IF NOT EXISTS (SELECT FROM pg_catalog.pg_roles WHERE rolname = '$DB_USER') THEN
            EXECUTE format('CREATE ROLE %I LOGIN PASSWORD %L', '$DB_USER', '$DB_PASSWORD');
          END IF;
        END
        \$\$;
      EOSQL

        psql --dbname postgres -v ON_ERROR_STOP=1 <<EOSQL > .log/postgres.log 2>&1
        CREATE DATABASE "$DB_NAME" OWNER "$DB_USER";
      EOSQL
      else
        pg_ctl -D "$PGDATA" -l .log/postgres.log -o "-k $PGDATA -p $DB_PORT" start
      fi
    '';

  in
  {
    devShells.x86_64-linux.default = let
      pkgs = pkgsFor "x86_64-linux";
    in pkgs.mkShell {
      packages = [ pkgs.postgresql_18 pkgs.yq ];
      shellHook = shellHook;
    };

    devShells.aarch64-linux.default = let
      pkgs = pkgsFor "aarch64-linux";
    in pkgs.mkShell {
      packages = [ pkgs.postgresql_18 pkgs.yq ];
      shellHook = shellHook;
    };
  };
}