From cf28f9d70b4a241934ecb1861275cb64884d43f7 Mon Sep 17 00:00:00 2001
From: Manuel Thalmann <m@nuth.ch>
Date: Sat, 6 Jul 2024 19:36:47 +0200
Subject: [PATCH] Cache `nixpkgs` locally

---
 archiso/scripts/build.sh | 25 ++++++++++++++++++-------
 1 file changed, 18 insertions(+), 7 deletions(-)

diff --git a/archiso/scripts/build.sh b/archiso/scripts/build.sh
index 72611308..cf3e95d7 100755
--- a/archiso/scripts/build.sh
+++ b/archiso/scripts/build.sh
@@ -1,13 +1,24 @@
 #!/bin/bash
-contextRoot="$(mktemp -d)";
-root="$contextRoot/airootfs";
-rootHome="$root/root";
-nixDir="$root/nix/var/nix/profiles/per-user/root/channels/nixpkgs";
+overlayDir="$(mktemp -d)";
+upperDir="$(mktemp -d)";
+workDir="$(mktemp -d)";
+cacheRoot=~/.cache/archiso-valhalla;
+nixCache="$cacheRoot/nixpkgs";
+root="airootfs";
+rootHome="$overlayDir/$root/root";
 profileDir="/mnt/archiso-valhalla";
+nixDir="$profileDir/$root/nix/var/nix/profiles/per-user/root/channels/nixpkgs";
 mkdir -p "$rootHome";
 git clone .. "$rootHome/PortValhalla";
-git clone https://github.com/NixOS/nixpkgs.git --depth=1 -b nixos-24.05 "$nixDir";
-rm -rf "$nixDir/.git";
-sudo mount --mkdir -t overlay overlay -o lowerdir=.:"$contextRoot" "$profileDir";
+
+if [ ! -d "$nixCache" ]; then
+    mkdir -p "$nixCache"
+    git clone https://github.com/NixOS/nixpkgs.git --depth=1 -b nixos-24.05 "$nixCache";
+    rm -rf "$nixCache/.git";
+fi;
+
+sudo mount --mkdir -t overlay overlay -o lowerdir=.:"$overlayDir",upperdir="$upperDir",workdir="$workDir" "$profileDir";
+sudo mount --mkdir --bind "$nixCache" "$nixDir";
 sudo mkarchiso "$@" "$profileDir";
+sudo umount "$nixDir";
 sudo umount "$profileDir";