# Based up original work by cleverca22
# https://github.com/cleverca22/nixos-configs/blob/master/qemu.nix

{ config, pkgs, lib, ... }:

with lib;
let
  cfg = config.qemu-user;
  arm = {
    interpreter = "${pkgs.qemu-user-arm}/bin/qemu-arm";
    magicOrExtension =
      "\\x7fELF\\x01\\x01\\x01\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x02\\x00\\x28\\x00";
    mask =
      "\\xff\\xff\\xff\\xff\\xff\\xff\\xff\\x00\\xff\\xff\\xff\\xff\\xff\\xff\\x00\\xff\\xfe\\xff\\xff\\xff";
  };
  aarch64 = {
    interpreter = "${pkgs.qemu-user-arm64}/bin/qemu-aarch64";
    magicOrExtension =
      "\\x7fELF\\x02\\x01\\x01\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x02\\x00\\xb7\\x00";
    mask =
      "\\xff\\xff\\xff\\xff\\xff\\xff\\xff\\x00\\xff\\xff\\xff\\xff\\xff\\xff\\x00\\xff\\xfe\\xff\\xff\\xff";
  };
  riscv64 = {
    interpreter = "${pkgs.qemu-riscv64}/bin/qemu-riscv64";
    magicOrExtension =
      "\\x7fELF\\x02\\x01\\x01\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x02\\x00\\xf3\\x00";
    mask =
      "\\xff\\xff\\xff\\xff\\xff\\xff\\xff\\x00\\xff\\xff\\xff\\xff\\xff\\xff\\x00\\xff\\xfe\\xff\\xff\\xff";
  };
in {
  options = {
    qemu-user = {
      arm = mkEnableOption "enable 32bit arm emulation";
      aarch64 = mkEnableOption "enable 64bit arm emulation";
      riscv64 = mkEnableOption "enable 64bit riscv emulation";
    };
    nix.supportedPlatforms = mkOption {
      type = types.listOf types.str;
      description = "extra platforms that nix will run binaries for";
      default = [ ];
    };
  };
  config = mkIf (cfg.arm || cfg.aarch64) {
    nixpkgs = { overlays = [ (import ../overlays/qemu) ]; };
    boot.binfmt.registrations = optionalAttrs cfg.arm { inherit arm; }
      // optionalAttrs cfg.aarch64 { inherit aarch64; }
      // optionalAttrs cfg.riscv64 { inherit riscv64; };
    nix.supportedPlatforms =
      (optionals cfg.arm [ "armv6l-linux" "armv7l-linux" ])
      ++ (optional cfg.aarch64 "aarch64-linux");
    nix.extraOptions = ''
      extra-platforms = ${toString config.nix.supportedPlatforms} i686-linux
    '';
    nix.sandboxPaths = [ "/run/binfmt" ]
      ++ (optional cfg.arm "${pkgs.qemu-user-arm}")
      ++ (optional cfg.aarch64 "${pkgs.qemu-user-arm64}");
  };
}