export function verifyInput()

in packages/amplify-cli/src/input-manager.ts [98:197]
75 lines of code
35 McCabe index (conditional complexity)

export function verifyInput(pluginPlatform: PluginPlatform, input: Input): InputVerificationResult {
  const result = new InputVerificationResult();

  input.plugin = input.plugin || constants.CORE;

  normalizeInput(input);

  const pluginCandidates = getPluginsWithName(pluginPlatform, input.plugin!);

  if (pluginCandidates.length > 0) {
    for (let i = 0; i < pluginCandidates.length; i++) {
      const { name, commands, commandAliases } = pluginCandidates[i].manifest;

      if ((commands && commands!.includes(constants.HELP)) || (commandAliases && Object.keys(commandAliases).includes(constants.HELP))) {
        result.helpCommandAvailable = true;
      }

      // verify if `input.command` is an actual command.
      if (commands && commands!.includes(input.command!)) {
        result.verified = true;
        break;
      }

      // verify if `input.command` is an alias for a command.
      if (commandAliases && Object.keys(commandAliases).includes(input.command!)) {
        input.command = commandAliases[input.command!];
        result.verified = true;
        break;
      }

      if (Array.isArray(input.subCommands) && input.subCommands.length > 0) {
        // if `input.command` is not a command name or an alias for a command, check the
        // first sub-command for a verb / noun swap (i.e. `env add` versus `add env`).
        if (commands && commands!.includes(input.subCommands[0])) {
          const command = input.subCommands[0];
          input.subCommands[0] = input.command!;
          input.command = command;

          result.verified = true;
          break;
        }

        // same as above, but check if the first sub-command is an alias.
        if (commandAliases && commandAliases.hasOwnProperty(input.subCommands[0])) {
          const command = commandAliases[input.subCommands[0]];
          input.subCommands[0] = input.command!;
          input.command = command;

          result.verified = true;
          break;
        }
      }

      // if `input.command` is the default plugin command, check `input.options` for what to do.
      if (input.command! === constants.PLUGIN_DEFAULT_COMMAND) {
        if (commands && commands!.includes(name)) {
          input.command = name;
          result.verified = true;
          break;
        }
        if (input.options && input.options[constants.VERSION] && commands && commands!.includes(constants.VERSION)) {
          input.command = constants.VERSION;
          result.verified = true;
          break;
        }
        if (input.options && input.options[constants.HELP] && commands && commands!.includes(constants.HELP)) {
          input.command = constants.HELP;
          result.verified = true;
          break;
        }

        // as a fall back, use the help command
        if (commands && commands!.includes(constants.HELP)) {
          input.command = constants.HELP;
          result.verified = true;
          break;
        }
      }
    }

    if (!result.verified) {
      let commandString = input.plugin === constants.CORE ? '' : input.plugin;

      if (input.command! !== constants.PLUGIN_DEFAULT_COMMAND) {
        commandString += ' ' + input.command!;
      }

      if (input.subCommands) {
        commandString += ' ' + input.subCommands!.join(' ');
      }

      result.message = `The Amplify CLI can NOT find command: ${commandString}`;
    }
  } else {
    result.verified = false;
    result.message = `The Amplify CLI can NOT find any plugin with name: ${input.plugin}`;
  }

  return result;
}