import assert from 'assert';
import fs from 'fs';
import os from 'os';
import path from 'path';

/**
 * The default Android SDK locations per platform.
 * @see https://developer.android.com/studio/run/emulator-commandline#filedir
 * @see https://developer.android.com/studio/intro/studio-config#optimize-studio-windows
 */
const ANDROID_DEFAULT_LOCATION: Readonly<Partial<Record<NodeJS.Platform, string>>> = {
  darwin: path.join(os.homedir(), 'Library', 'Android', 'sdk'),
  linux: path.join(os.homedir(), 'Android', 'sdk'),
  win32: path.join(os.homedir(), 'AppData', 'Local', 'Android', 'Sdk'),
};

/**
 * Resolve and validate the root folder where the Android SDK has been installed.
 * This checks both `ANDROID_HOME`, `ANDROID_SDK_ROOT`, and the default path for the current platform.
 * @see https://developer.android.com/studio/command-line/variables
 */
export function assertSdkRoot() {
  if (process.env.ANDROID_HOME) {
    assert(
      fs.existsSync(process.env.ANDROID_HOME),
      `Failed to resolve the Android SDK path. ANDROID_HOME is set to a non-existing path: ${process.env.ANDROID_HOME}`
    );
    return process.env.ANDROID_HOME;
  }

  if (process.env.ANDROID_SDK_ROOT) {
    assert(
      fs.existsSync(process.env.ANDROID_SDK_ROOT),
      `Failed to resolve the Android SDK path. Deprecated ANDROID_SDK_ROOT is set to a non-existing path: ${process.env.ANDROID_SDK_ROOT}. Use ANDROID_HOME instead.`
    );
    return process.env.ANDROID_SDK_ROOT;
  }

  const defaultLocation = ANDROID_DEFAULT_LOCATION[process.platform];
  if (defaultLocation) {
    assert(
      fs.existsSync(defaultLocation),
      `Failed to resolve the Android SDK path. Default install location not found: ${defaultLocation}. Use ANDROID_HOME to set the Android SDK location.`
    );
    return defaultLocation;
  }

  return null;
}