# rpi-cross-overlay.nix
#
# Override pkgs.rpi to cross-compile when buildPlatform != hostPlatform.
#
# By default, nixos-raspberrypi's nixpkgs-rpi module creates pkgs.rpi via
# mkRpiPkgs which imports nixpkgs with system="aarch64-linux" — a NATIVE
# aarch64 build that requires QEMU on x86_64 builders.
#
# This module detects cross-compilation (buildPlatform != hostPlatform) and
# re-imports pkgs.rpi using localSystem (builder) + crossSystem (target) so
# that kernel, firmware, and rpi-optimized packages are genuinely cross-compiled
# with zero QEMU emulation.
#
# Once nixos-raspberrypi upstream supports buildPlatform natively in mkRpiPkgs,
# this module can be removed.

{ config, lib, pkgs, nixos-raspberrypi, ... }:

let
  inherit (config.nixpkgs) buildPlatform hostPlatform;
  isCross = buildPlatform.system != hostPlatform.system;
in
lib.mkIf isCross {
  nixpkgs.overlays = [
    (final: prev: {
      rpi = import pkgs.path {
        localSystem = { system = buildPlatform.system; };
        crossSystem = { system = hostPlatform.system; };
        overlays = with nixos-raspberrypi.overlays; [
          bootloader
          vendor-kernel
          vendor-firmware
          kernel-and-firmware
          vendor-pkgs
          pkgs
        ];
      };
    })
  ];
}