#!/bin/sh
NIXOS_VERSION=20.03

fetch() {
  rev=$1
  output=$2
  url=${3:-https://github.com/NixOS/nixpkgs-channels.git}

  printf "\033[1m$url\033[0m $rev\n"
  nix-prefetch-git \
    --url "${url}" \
    --rev "${rev}" \
    > "${output}"
}

nixpkgs() {
  fetch "refs/heads/nixos-$NIXOS_VERSION" .versions/nixpkgs.json
}

nixpkgs_unstable() {
  fetch "refs/heads/nixos-unstable" .versions/nixpkgs-unstable.json
}

home_manager() {
  fetch "refs/heads/release-$NIXOS_VERSION" .versions/home-manager.json "https://github.com/rycee/home-manager.git"
}

krops() {
  fetch "refs/tags/v1.21.0" .versions/krops.json "https://cgit.krebsco.de/krops"
}

stockholm() {
  fetch "ea5b591d065b721666fc3527ad45a7545a594a77" .versions/stockholm.json "https://cgit.krebsco.de/stockholm"
}

usage() {
  echo >&2 "Usage: $0 [--all | REPO... ]

  Where REPO is one of nixpkgs, home-manager, krops, stockholm"
  exit 1
}

if [ $# -eq 0 ]; then
  usage
else
  for arg in "$@"; do
    case $arg in
      nixpkgs)
        nixpkgs &
        nixpkgs_unstable & ;;
      home-manager)
        home_manager & ;;
      krops)
        krops & ;;
      stockholm)
        stockholm & ;;
      --all)
        nixpkgs &
        nixpkgs_unstable &
        home_manager &
        krops &
        stockholm & ;;
      *)
        usage ;;
    esac
    shift
  done
  wait
fi