{
  # nix run nixpkgs#alejandra -- format ./flake.nix
  description = "Expo RN devshells (local emulator / remote AVD)";
  inputs = {
    nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable";
    # Android SDK as packages
    android-nixpkgs = {
      url = "github:tadfisher/android-nixpkgs";
      inputs.nixpkgs.follows = "nixpkgs";
    };
  };

  outputs = {
    self,
    nixpkgs,
    android-nixpkgs,
    ...
  }: let
    systems = ["x86_64-linux" "aarch64-darwin" "x86_64-darwin"];
    forAllSystems = f:
      nixpkgs.lib.genAttrs systems (
        system:
          f {
            pkgs = import nixpkgs {
              inherit system;
              overlays = [android-nixpkgs.overlays.default];
              config.allowUnfree = true; # emulator is unfree
            };
          }
      );
  in {
    devShells = forAllSystems ({pkgs}: let
      makeAndroidSdk = mode: let
        androidSdk = pkgs.androidSdk (
          sdk:
            if mode == "full"
            then
              (with sdk; [
                cmdline-tools-latest
                platform-tools
                emulator
                build-tools-36-0-0
                platforms-android-36
                system-images-android-36-0-Baklava-google-apis-playstore-x86-64
                # Add NDK + CMake for native builds
                ndk-26-1-10909125
                cmake-3-22-1
              ])
            else if mode == "remote"
            then
              (with sdk; [
                cmdline-tools-latest # ← required for a valid SDK
                platform-tools # adb/fastboot
              ])
            else throw "makeAndroidSdk: unknown mode '${mode}'. Use \"full\" or \"remote\"."
        );

        # Standard path from nixpkgs' androidSdk wrapper
        # https://ryantm.github.io/nixpkgs/languages-frameworks/android/#notes-on-environment-variables-in-android-projects
        sdkRoot = "${androidSdk}/libexec/android-sdk";
      in {
        inherit androidSdk sdkRoot;
      };

      fullAndroidSdk = makeAndroidSdk "full";
      remoteAndroidSdk = makeAndroidSdk "remote";

      defaultPkgs = with pkgs; [
        nodejs_22
        nodePackages.pnpm
        git
        just
        jq
        watchman
        jdk17
        gradle_8
        cmake
        ninja
        pkg-config
      ];
    in {
      # Minimal: only universal dev tools you always want
      default = pkgs.mkShell {
        packages = defaultPkgs;
      };

      # Local emulator: full SDK + AVD bits for API 36
      android-local = pkgs.mkShell {
        packages = defaultPkgs ++ [fullAndroidSdk.androidSdk];
        shellHook = ''
          # Resolve SDK root robustly (libexec first, then share)
          _CANDS=(
            "${fullAndroidSdk.sdkRoot}"
            "${fullAndroidSdk.androidSdk}/libexec/android-sdk"
            "${fullAndroidSdk.androidSdk}/share/android-sdk"
          )
          for p in "''${_CANDS[@]}"; do
            if [ -d "$p" ]; then
              export ANDROID_SDK_ROOT="$p"
              export ANDROID_HOME="$p"
              break
            fi
          done

          if [ -z "$ANDROID_SDK_ROOT" ]; then
            echo "❌ Could not locate ANDROID_SDK_ROOT in Nix store. Check androidSdk composition."
            return 1
          fi

          # Ensure Nix adb/emulator/cmdline-tools win over system tools
          export PATH="$ANDROID_SDK_ROOT/platform-tools:$ANDROID_SDK_ROOT/emulator:$ANDROID_SDK_ROOT/cmdline-tools/latest/bin:$PATH"
          hash -r

          echo "ANDROID_SDK_ROOT=$ANDROID_SDK_ROOT"
          which -a adb || true
          which -a emulator || true
          which -a avdmanager || true

          # quick sanity
          adb version || true
          emulator -version || true
          avdmanager --help >/dev/null || true
        '';
      };

      # Remote AVD workflow: no emulator/image; add scrcpy + adb only
      android-remote = pkgs.mkShell {
        packages =
          defaultPkgs
          ++ [
            remoteAndroidSdk.androidSdk # provides adb/fastboot only
            pkgs.scrcpy
          ];
        shellHook = ''
          export ANDROID_SDK_ROOT="${remoteAndroidSdk.sdkRoot}"
          export ANDROID_HOME="${remoteAndroidSdk.sdkRoot}"
          export PATH="${remoteAndroidSdk.sdkRoot}/platform-tools:$PATH"
          hash -r
          echo "Using Nix adb from: $ANDROID_SDK_ROOT"
          which -a adb
          adb version || true
          echo "Tip: ssh -N -L 5037:127.0.0.1:5037 user@remote && scrcpy"
        '';
      };
    });
  };
}