{
  description = "SDR toolbox — programs for exploring an RTL-SDR stick";

  inputs = {
    nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable";
  };

  outputs = { self, nixpkgs }:
    let
      system = "x86_64-linux";
      pkgs = nixpkgs.legacyPackages.${system};
      lib = pkgs.lib;

      # rtl_wmbus: demodulator that turns raw rtl_sdr I/Q into wM-Bus frames.
      # Not in nixpkgs, so build from source (tiny pure-C project).
      rtl_wmbus = pkgs.stdenv.mkDerivation {
        pname = "rtl-wmbus";
        version = "1.1.0";
        src = pkgs.fetchFromGitHub {
          owner = "xaelsouth";
          repo = "rtl-wmbus";
          rev = "1.1.0";
          sha256 = "1f9psbakvi0ymqmlbbnn96cbvd3bfphc90hw6xwid6r184pnzac6";
        };
        enableParallelBuilding = true;
        installPhase = ''
          runHook preInstall
          install -Dm755 build/rtl_wmbus $out/bin/rtl_wmbus
          runHook postInstall
        '';
        meta.description = "Software defined receiver for wireless M-Bus with RTL-SDR";
      };

      # wmbusmeters: reads/decodes wM-Bus (OMS) smart-meter telegrams. Dropped
      # from nixpkgs, so build from source. At runtime it shells out to
      # rtl_sdr | rtl_wmbus, so wrap those onto its PATH.
      wmbusmeters = pkgs.stdenv.mkDerivation {
        pname = "wmbusmeters";
        version = "3.0.0";
        src = pkgs.fetchFromGitHub {
          owner = "wmbusmeters";
          repo = "wmbusmeters";
          rev = "3.0.0";
          sha256 = "1nnirlnb12zdadsvsybj8h2g6fy7hc7ih488i2qaxzinm1faxagp";
        };
        nativeBuildInputs = [ pkgs.pkg-config pkgs.makeWrapper ];
        buildInputs = [ pkgs.rtl-sdr pkgs.libusb1 pkgs.libxml2 ];
        enableParallelBuilding = true;
        postPatch = ''
          patchShebangs scripts
        '';
        installPhase = ''
          runHook preInstall
          install -Dm755 build/wmbusmeters $out/bin/wmbusmeters
          ln -s wmbusmeters $out/bin/wmbusmetersd
          wrapProgram $out/bin/wmbusmeters \
            --prefix PATH : ${lib.makeBinPath [ pkgs.rtl-sdr rtl_wmbus ]}
          runHook postInstall
        '';
        meta.description = "Read wM-Bus / OMS smart meters (water, heat, gas, electricity)";
      };

      # oms-tui: full-screen TUI for monitoring OMS / wM-Bus meters. Wraps
      # wmbusmeters (put on PATH) and adds a live device list, detail view,
      # live AES-key entry, and CSV export/import.
      oms-tui = pkgs.python3Packages.buildPythonApplication {
        pname = "oms-tui";
        version = "0.1.0";
        pyproject = true;
        src = ./oms-tui;
        build-system = [ pkgs.python3Packages.setuptools ];
        dependencies = [ pkgs.python3Packages.textual ];
        nativeBuildInputs = [ pkgs.makeWrapper ];
        nativeCheckInputs = [
          pkgs.python3Packages.pytestCheckHook
          pkgs.python3Packages.pytest-asyncio
          wmbusmeters # exercises the real decode pipeline in the test suite
        ];
        postFixup = ''
          wrapProgram $out/bin/oms-tui \
            --prefix PATH : ${lib.makeBinPath [ wmbusmeters ]}
        '';
        meta.description = "TUI monitor for OMS / wireless M-Bus smart meters";
      };

      # wmbus-listen: convenience wrapper around wmbusmeters for OMS discovery.
      wmbus-listen = pkgs.writeShellApplication {
        name = "wmbus-listen";
        runtimeInputs = [ wmbusmeters ];
        text = ''
          # Listen for wM-Bus / OMS smart-meter telegrams on 868.95 MHz via RTL-SDR.
          #
          # Usage:
          #   wmbus-listen                     # discovery: show every telegram heard
          #   wmbus-listen NAME DRIVER ID KEY  # decode one meter's readings
          #     e.g. wmbus-listen Water multical21 12345678 00112233445566778899AABBCCDDEEFF
          #
          # Env overrides:
          #   WMBUS_MODES   link modes to listen for (default: c1,t1 — typical OMS)
          #   WMBUS_FORMAT  output format: json | fields | hr (default: json)
          modes="''${WMBUS_MODES:-c1,t1}"
          format="''${WMBUS_FORMAT:-json}"
          if [ "$#" -eq 0 ]; then
            echo "Listening for OMS/wM-Bus telegrams (modes: $modes) on 868.95 MHz. Ctrl-C to stop." >&2
            echo "Unknown meters are printed as they are heard — note their id/driver to decode them." >&2
            exec wmbusmeters --format="$format" --listento="$modes" --verbose rtlwmbus
          else
            exec wmbusmeters --format="$format" --listento="$modes" rtlwmbus "$@"
          fi
        '';
      };

      sdrTools = (with pkgs; [
        rtl-sdr # rtl_test, rtl_fm, rtl_power — verify the stick works first
        sdrpp # modern spectrum browser with waterfall (run: sdrpp)
        gqrx # classic beginner-friendly waterfall receiver
        rtl_433 # decode 433/868 MHz sensors: weather stations, doorbells, meters
        dump1090-fa # ADS-B aircraft tracking on 1090 MHz with a live web map
        multimon-ng # decode POCSAG pagers, AFSK, DTMF (pipe rtl_fm into it)
        welle-io # DAB+ digital radio
        satdump # NOAA/Meteor weather satellite images
        noaa-apt # simple NOAA APT satellite image decoder
        # Heavier options — uncomment if wanted:
        # sdrangel   # kitchen-sink SDR app, many digital modes
        # gnuradio   # build your own DSP flowgraphs
      ]) ++ [
        rtl_wmbus # wM-Bus demodulator (rtl_sdr | rtl_wmbus)
        wmbusmeters # decode OMS smart meters
        wmbus-listen # convenience: listen for OMS telegrams (see below)
        oms-tui # full-screen OMS monitor TUI
      ];
    in
    {
      devShells.${system}.default = pkgs.mkShell {
        packages = sdrTools;
        shellHook = ''
          echo "SDR shell ready. Start with: rtl_test  (OMS meters: wmbus-listen)"
        '';
      };

      packages.${system} = {
        inherit rtl_wmbus wmbusmeters wmbus-listen oms-tui;
        default = oms-tui;

        # Also expose the whole toolbox as one installable package set:
        #   nix profile install .#sdr-tools
        sdr-tools = pkgs.buildEnv {
          name = "sdr-tools";
          paths = sdrTools;
        };
      };
    };
}