#!/usr/bin/env bash
set -euo pipefail

# Enable all future paths in this script to be relative to the directory containing the script.
cd "$(dirname -- "${BASH_SOURCE[0]}")"

configPath=$(realpath -- "hosts/$HOSTNAME/default.nix")

if [ ! -f $configPath ]; then
    echo "aborting: $configPath doesn't exist"
    exit 1
fi

nix-eval() {
    nix-instantiate --eval --raw --read-write-mode "$@"
}

channel=$(nix-eval --argstr host "$HOSTNAME" --expr '{host}:
let
  toml = builtins.readFile ./hosts/${host}/metadata.toml;
in
  (builtins.fromTOML toml).channel
')
nixpkgsPath=$(nix-eval --argstr channel "$channel" --expr '{channel}: (import ./npins).${channel}.outPath')

# nixos-rebuild always reads Nixpkgs from the NIX_PATH,
# so we need to set it explicitly to our pinned version
exec nixos-rebuild "$@" -I nixpkgs="$nixpkgsPath" -I nixos-config="$configPath" -I top="$(pwd)"