How to work with legacy code

MICHAŁ SZCZUR
PHP Developer since 2010
bass guitarist and trumpeter
michalszczur.pl
Created by /Michał Szczur @partikus

AGENDA
Scope explanation
Dive into legacy mess
How to start and not die
Step by step to heaven

THANKS TO MAREK MATULKA
WHO INSPIRED ME!

CODE WRITTEN MANY YEARS AGO
BY MYSELF OR OTHER NINJAS

(PRE)HISTORICAL CODE USES NONEXISTING
FRAMEWORKS/LIBRARIES

WHEN CODE CAN BE CALLED
LEGACY ???

WHEN IT IS
TOO HARD TO UNDERSTAND

WHEN IT IS
TOO COUPLED TO FRAMEWORK

WHEN IT IS
TOO HARD TO ADD NEW FEATURE

NO !!!
WE'RE NINJA DEVS
WE LOVE CHALLENGES

TAKE NEW FRAMEWORK
AND START FROM THE BEGINNING

:(MAYBE SOME DAY IN THE FUTURE

EXTENDED LEGACY
CODE
WEB PHP APP

PREASUMPTIONS
YOU DON'T KNOW BUSINESS LOGIC
MOSTLY PROCEDURAL CODE
NO SEPARATION, JUST A FEW LARGE FILES
YOU NEED TO CHANGE STH

LOW LEVEL DOCUMENTATION
FEATURES DESCRIBED BY SCENARIOS (E.G.
GHERKIN)
CLEAN CODE
EASY TO CHANGE (LESS PAIN)
EASY CONTINUOUS DEPLOYMENT

# Project structure
/404.php
/database.php
/functions.php
/index.php
/page.php

PROCEDURAL CODE
WRITTEN IN PHP
INLINE PHP FUNCTIONS MIXED WITH HTML,CSS,JS

#/functions.php
function show_all() {
$db = connect_to_db();
$sql = 'SELECT * FROM receivers';
$result = mysql_query($sql) or die(mysql_error());
while ($row = mysql_fetch_array($result)) {
//echo 'ID: ' . $row['id'] . ', mail: ' . $row['mail'];
echo ''.$row['mail'].'';
echo '<form id="'.$row['id'].'" name="n_ID" method="POST" action=
<input type="hidden" name="id" value="'.$row['id'].'" />
<input type="submit" name="delete" value="Delete" />
</form>';
}
if (isset($_POST['delete'])) {
$n_ID = $_POST['id'];
$sql = "DELETE FROM receivers WHERE id = $n_ID";
mysql_query($sql) or die(mysql_error());

// show_all_receivers.js
casper.test.begin('List all receivers', 5, function suite(test) {
casper.start("http://myapp.dev/mailsender.php", function() {
test.assertHttpStatus(200);
test.assertTitle("Homepage | Mail Sender", "Homepage title is expecte
});
casper.thenClick('a#show-all', function() {
test.assertHttpStatus(200);
test.assertTitle(
"Receivers list | Mail Sender",
"Page title is correct"
);
});
casper.run(function() {
test.done();
});
});

PROCEDURAL CODE??
YOU NEED STH MORE

DEPENDENCY
INJECTION
IOC IMPLEMENTATION

PACKAGE MANAGER
COMPOSER
RUBYGEMS
MAVEN

COMPONENTS
DEPENDENCY INJECTION
/ /SYMFONY DI PIMPLE AURA DI

WELL DOCUMENTED
AND KNOWN BY COMMUNITY

MOVE APP TO /WEB/
# new project structure
/
/web/404.php
/web/database.php
/web/functions.php
/web/index.php
/web/page.php

INSTALL COMPOSER
php -r "readfile('https://getcomposer.org/installer');" > composer-setup.php
php -r "if (hash('SHA384', file_get_contents('composer-setup.php')) ===
php composer-setup.php
php -r "unlink('composer-setup.php');"

INIT COMPOSER CONFIG IN THE ROOT DIR
php composer.phar init

PROJECT STRUCTURE
ls -l
/
/composer.json
/web/

COMPOSER.JSON
{
"name": "michalszczur/legacy-demo",
"authors": [
{
"name": "Michal Szczur",
"email": "job@michalszczur.pl"
}
],
"require": {},
"autoload": {
"psr-4": {
"": "src/"
}
},
"description": "Legacy app demo",
"type": "project",
"license": "proprietary"

ADD DEPENDENCIES
php composer.phar require symfony/dependency-injection
php composer.phar require symfony/config
php composer.phar require symfony/yaml

<?php
# /web/container.php
use SymfonyComponentDependencyInjectionContainerBuilder;
use SymfonyComponentConfigFileLocator;
use SymfonyComponentDependencyInjectionLoaderYamlFileLoader;
require __DIR__.'/../vendor/autoload.php';
$container = new ContainerBuilder();
$loader = new YamlFileLoader($container, new FileLocator(__DIR__.'/../app/con
$loader->load('services.yml');
$container->compile();

WHICH SERVICES DO WE REALLY
NEED?

function show_all()
{
# Database connection needed
$sql = 'SELECT * FROM mail_sender';
//...

SERVICES.YML
parameters:
db_host: localhost
db_port: 3306
db_name: legacyapp
db_user: myuser
db_pass: mypass
services:
db:
class: PDO
arguments: ['mysql:port=%db_port%;host=%db_host%;dbname=%db_name%'
receiver_repository:
class: PDOReceiverRepository
arguments: ['@db']

#index.php
...
require 'container.php';
...
function show_all()
{
# Database connection needed
$receiverRepository = $container->get('receiver_repository');
$result = $receiverRepository->findAll();
...

#index.php
...
foreach ($result as $row) {
echo '<form id="'.$row['id'].'" name="n_ID" method="POST" action="mai
<input type="submit" name="delete" value="Usuń" />
</form>';
}
...

PHP ~ HTML
STILL MIXED TOGETHER

INSTALL TWIG USING COMPOSER
php composer.phar require twig/twig

SERVICES.YML
parameters:
...
twig_paths:
- app/Resources/views
services:
...
twig.loader:
class: Twig_Loader_Filesystem
arguments: ['%twig_paths%']
twig:
class: Twig_Environment
arguments: ['@twig.loader']

#index.php
...
$twig = $container->get('@twig');
echo $twig->render(
'receiver_list.html.twig',
['receivers' => $result]
);
...

{% for receiver in receivers %}
<form id="{{ receiver.id }}" name="n_ID" method="POST" action="mail_sender.ph
<input type="hidden" name="id" value="{{ receiver.id }}" />
<input type="submit" name="delete" value="Delete" />
</form>
{% endfor %}

BEFORE
function show_all()
{
$sql = 'SELECT * FROM mail_sender';
while ($row = mysql_fetch_array($result)) {
//echo 'ID: ' . $row['id'] . ', mail: ' . $row['mail'];
echo '<form id="'.$row['id'].'" name="n_ID" method="POST" action="mai
<input type="submit" name="delete" value="Usuń" />
</form>';
}
...
mysql_free_result($result);
mysql_close($db);
}

AFTER
function show_all() {
$receiverRepository = $container->get('receiver_repository');
$twig = $container->get('@twig');
echo $twig->render(
'receiver_list.html.twig',
['receivers' => $result]
...
);

QUESTIONS?
SLIDES: SLIDESHARE.NET/MICHASZCZUR
FEEDBACK: JOIND.IN/EVENT/CODETECON-20161
TWITTER: @PARTIKUS
HOMEPAGE: MICHALSZCZUR.PL

LINKS
Marek Matulka - Modernising the Legacy
CasperJS
Symfony Components
Working Eﬀectively with Legacy Code by Michael Feathers
Page Object Pattern (Martin Fowler)
Page Object Pattern (Selenium Docs)

How to work with legacy code

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