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

with lib;
let
  cfg = config.services.lvm;
in {
  options.services.lvm = {
    package = mkOption {
      type = types.package;
      default = if cfg.dmeventd.enable then pkgs.lvm2_dmeventd else pkgs.lvm2;
      internal = true;
      defaultText = "pkgs.lvm2";
      description = ''
        This option allows you to override the LVM package that's used on the system
        (udev rules, tmpfiles, systemd services).
        Defaults to pkgs.lvm2, or pkgs.lvm2_dmeventd if dmeventd is enabled.
      '';
    };
    dmeventd.enable = mkEnableOption "the LVM dmevent daemon";
    boot.thin.enable = mkEnableOption "support for booting from ThinLVs";
  };

  config = mkMerge [
    ({
      # minimal configuration file to make lvmconfig/lvm2-activation-generator happy
      environment.etc."lvm/lvm.conf".text = "config {}";
    })
    (mkIf (!config.boot.isContainer) {
      systemd.tmpfiles.packages = [ cfg.package.out ];
      environment.systemPackages = [ cfg.package ];
      systemd.packages = [ cfg.package ];

      # TODO: update once https://github.com/NixOS/nixpkgs/pull/93006 was merged
      services.udev.packages = [ cfg.package.out ];
    })
    (mkIf cfg.dmeventd.enable {
      systemd.sockets."dm-event".wantedBy = [ "sockets.target" ];
      systemd.services."lvm2-monitor".wantedBy = [ "sysinit.target" ];

      environment.etc."lvm/lvm.conf".text = ''
        dmeventd/executable = "${cfg.package}/bin/dmeventd"
      '';
    })
    (mkIf cfg.boot.thin.enable {
      boot.initrd = {
        kernelModules = [ "dm-snapshot" "dm-thin-pool" ];

        extraUtilsCommands = ''
          copy_bin_and_libs ${pkgs.thin-provisioning-tools}/bin/pdata_tools
          copy_bin_and_libs ${pkgs.thin-provisioning-tools}/bin/thin_check
        '';
      };

      environment.etc."lvm/lvm.conf".text = ''
        global/thin_check_executable = "${pkgs.thin-provisioning-tools}/bin/thin_check"
      '';
    })
    (mkIf (cfg.dmeventd.enable || cfg.boot.thin.enable) {
      boot.initrd.preLVMCommands = ''
          mkdir -p /etc/lvm
          cat << EOF >> /etc/lvm/lvm.conf
          ${optionalString cfg.boot.thin.enable ''
            global/thin_check_executable = "$(command -v thin_check)"
          ''}
          ${optionalString cfg.dmeventd.enable ''
            dmeventd/executable = "$(command -v false)"
            activation/monitoring = 0
          ''}
          EOF
      '';
    })
  ];

}