refactor: enable host-specific configuration

1 files changed, 24 insertions, 4 deletions

diff --git a/nixos/rebuild b/nixos/rebuild
index 98101c1..3cb086e 100755
--- a/nixos/rebuild
+++ b/nixos/rebuild
@@ -1,10 +1,30 @@
 #!/usr/bin/env bash
 set -euo pipefail
 
-# nix-instantiate --eval has no raw mode yet
-nixpkgsPath=$(nix-instantiate --eval --read-write-mode nixpkgs/path.nix | tr -d \")
-# Get the ./configuration.nix relative to this script
-configPath=$(realpath -- "$(dirname -- "${BASH_SOURCE[0]}")/configuration.nix")
+# Enable all future paths in this script to be relative to the directory containing the script.
+cd "$(dirname -- "${BASH_SOURCE[0]}")"
+
+configPath=$(realpath -- "$HOSTNAME-configuration.nix")
+
+if [ ! -f $configPath ]; then
+    echo "aborting: $configPath doesn't exist"
+    exit 1
+fi
+
+firstLine=$(head -n1 "$configPath")
+
+if ! echo "$firstLine" | grep -E ^"# channel *=" > /dev/null; then
+    echo "aborting: $configPath doesn't start with \`# channel=\"...\"\`, where ... is a pin from sources.json"
+    exit 1
+fi
+
+nix-eval() {
+    nix-instantiate --eval --read-write-mode "$@" \
+      | tr -d \"  # nix-instantiate has no raw output yet (like the experimental nix eval)
+}
+
+channel=$(nix-eval --argstr line "$(echo $firstLine | tr -d \#)" --expr '{line}: (builtins.fromTOML line).channel')
+nixpkgsPath=$(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