重构如果地狱

Question

TL;DR: What strategy can I follow to simplify request's if hell?

I'm refering specifically to one of my github files. It's there to deal with different possible user actions. I'm trying to refactor it, but I'm not sure what's the best way. A small fraction of the code:

// The users returned from validating
if (!empty($_SESSION['service_connect']))
  {
  // If the service is a valid one
  if (in_array($_SESSION['service'], $UMConfig->services))
    {
    // Include the needed files.
    include $UMConfig->path . "/services/" . $_SESSION['service'] . "/verify.php";
    }
  }
// One service has set an email
if (isset($_SESSION['service_email']))
  {
  // The user is already in the database
  if (Validate::is_user($_SESSION['service_email']))
    {
    // User is logged in
    $_SESSION['email'] = $_SESSION['service_email'];
    include 'actions/login.php';
    }
  // The user is not in the database and didn't submit anythign
  elseif (empty($_POST))
    {
    // !POST
    $UMLog = "We are trying to register you with a service.";
    // Check if the popup has been submited or not
    include 'actions/service_verified.php';
    }
  // The user has submitted something with POST
  else {
    include 'actions/register_service.php';
    $UMLog = "Registering with " . $_SESSION['service'] . ".";
    }
  }

// No user was in the session but there's a user in the cookies
elseif (isset($_COOKIE['email']))
  {
  // The email is in the database
  if (Validate::is_user($_COOKIE['email']))
    {
    // If there's a token
    if (isset($_COOKIE['token']))

My idea right now is to simplify the code into smaller chunks and call them individually. This is the general idea of what I intend to do:

// Get what kind of action is needed
require 'request.php';
$action = request($_POST, $_SESSION, $_COOKIE);

if (file_exists($action_path = "actions/" . $action . ".php"))
  include $action_path;
else
  throw new Exception("Action was not valid: " . $action);

However, this only simplifies it slightly, as I'm only moving the if hell to 'request.php'. It has the advantage that testing is much easier in this way.

I have read how polymorphism can simplify some ifs, however I don't think it can be applied in this case. What strategy can I follow to simplify this if hell?

EDIT: in case anyone's wondering, I have so many ifs because, besides the regular login/register, I allow users to login/register using an external service as facebook/google/etc, which requires more steps and makes it significantly more difficult.

Answer 1

I decided to follow this strategy: one function, request(), identifies what kind of request is being made in their simplest form. Only identifies the action in its simplest form and returns this.

Then, the script calling it, include.php, includes that action from a directory containing all actions. Each of the callable actions have many methods to verify they are valid.

request.php:

<?php

// Find if there was any action to be done with the data provided
// Importance of requests: post > session > cookie (there're no get requests)

function request($Post, $Session, $Cookie)
  {
  // The user is trying to log out
  if ($Post->logout)
    {
    return "log_user_out";
    }

  // The user wants to edit the profile
  if ($Post->edit)
    {
    return "edit_user_data";
    }

  // Someone is trying to log in
  if ($Post->login)
    {
    return "log_user_in";
    }

  // Someone is trying to log in
  if ($Post->recover)
    {
    return "recover_password";
    }

  // Someone is trying to register
  if ($Post->register)
    {
    return "register_with_form";
    }

  // First time the user attempts to connect with a service
  // This should be vefore register_with_service in case someone clicked
  // a service but later wants to register with another service
  if ($Post->service_connect)
    {
    return "service_connect";
    }

  // Someone is trying to register with a service
  if ($Post->service && $Session->service_email)
    {
    return "register_with_service";
    }

  // The service returned green light
  if ($Session->service_connect)
    {
    return "verify_service";
    }

  // The user just landed here after confirming in the service
  if ($Session->service_email)
    {
    return "service_is_verified";
    }

  // There's already a user logged in. Simply retrieve the user
  if ($Session->email)
    {
    return "retrieve_user";
    }

  // There's apparently a user in the cookies
  if (isset($Cookie['email']))
    {
    return "login_with_cookie";
    }

  // If nothing from the above was submitted
  return null;
  }