Div PHP Laze

laze is a PHP library designed for defining _lazy evaluation_. Values are set as closures and only materialize upon first access, ensuring efficient and controlled initialization. Once a closure function is evaluated, it becomes immutable and cannot be redefined as a different value. However, it can be redefined as a closure until it?s accessed, at which point it transforms into a non-closure value.

laze might be an English word that suggests relaxation or laziness, but in this context, it?s actually an acronym derived from Lazy Evaluation. This refers to a programming technique where the evaluation of an expression is delayed until its value is needed. With laze, once the value is evaluated, it becomes an immutable value. In other words, a value that, although evaluated with delay, cannot be modified after its initial evaluation. Thus, laze encapsulates the concept of deferred evaluation that results in a definitive value, combining flexibility and robustness into one concept.

Installation

You can install laze using Composer:

composer require divengine/laze

Usage

Defining a Lazy Constant

To define a lazy constant, use the laze::define method. The value must be provided as a closure.

use divengine\laze;

// Define a lazy constant
laze::define('MY_CONSTANT', fn() => computeExpensiveValue());

Reading a Lazy Constant

To access the value, use the Laze::read method. The closure will be evaluated on the first access, and the result will be stored as the constant's value.

$value = laze::read('MY_CONSTANT');

Basic example

use divengine\laze;

// Define a lazy constant. Simulate an expensive computation
laze::define('MY_CONSTANT', fn() => return rand(1, 100)); 

// First access, the closure is evaluated
$value = laze::read('MY_CONSTANT');
echo $value; // Outputs the evaluated value

// Subsequent access returns the stored value
$value = laze::read('MY_CONSTANT');
echo $value; // Outputs the same value as before

Comprehensive example

This example covers the full range of Laze's capabilities in a concise manner suitable for a README, showing how it can be applied in real-world scenarios.

• Constraints: Ensures that APP_CONFIG implements the Configurable interface.
• Closure Returning Closure: MY_FUNCTION key holds a closure that returns another closure
• Lazy Value with Object Instance: APP_CONFIG stores an instance of AppConfig, which is validated by the constraint.
• Reusing define and read: FINAL_MESSAGE reads from both APP_CONFIG and MY_FUNCTION, combining their values.
• PHPUnit Test: Demonstrates how APP_CONFIG can be redefined for testing, using a mock object.

interface Configurable {
    public function configure(array $settings): void;
}

class AppConfig implements Configurable {
    private array $settings;

    public function configure(array $settings): void {
        $this->settings = $settings;
    }

    public function getSetting(string $key) {
        return $this->settings[$key] ?? null;
    }
}

// 1. Add a constraint to ensure a value implements the Configurable interface
laze::constraint(
    name: 'Must implement Configurable interface',
    fn($key, $value) => $key == 'APP_CONFIG' ? $value instanceof Configurable : true
);

// 2. Define a lazy value that returns a closure
laze::define('MY_FUNCTION', function() {
    return function() {
        return "Function Result";
    };
});

// 3. Define a lazy value with an object instance
laze::define('APP_CONFIG', function() {
    $config = new AppConfig();
    $config->configure([
        'timezone' => 'UTC',
        'locale' => 'en_US'
    ]);
    return $config;
});

// 4. Reuse define and read within each other
laze::define('FINAL_MESSAGE', function() {
    $config = laze::read('APP_CONFIG');
    $timezone = $config->getSetting('timezone');
    return laze::read('MY_FUNCTION')() . " in timezone $timezone";
});

$finalMessage = laze::read('FINAL_MESSAGE');
echo $finalMessage; // Outputs: "Function Result in timezone UTC"

// 5. PHPUnit Test - Redefining a value
class LazeTest extends \PHPUnit\Framework\TestCase {
    public function testAppConfigCanBeMocked() {

        // mock function
        laze::define('MY_FUNCTION', function() {
            return function() {
                return "Mocked Result";
            };
        });

        // mock object
        laze::define('APP_CONFIG', function() {
            $mockConfig = $this->createMock(Configurable::class);
            $mockConfig->method('getSetting')->willReturn('mocked_timezone');
            return $mockConfig;
        });

        $message = laze::read('FINAL_MESSAGE');
        $this->assertEquals("Mocked Result in timezone mocked_timezone", $message);
    }
}

How to reset Laze during testing

If you need to reset Laze during testing, you have two options:

1. Using reflection to reset the internal state of Laze.

   class LazeTest extends \PHPUnit\Framework\TestCase {
   
       public $lazeBackup;
   
       public function setUp(): void {
           parent::setUp();
           $reflection = new ReflectionClass(laze::class);
           $property = $reflection->getProperty('store');
           $property->setAccessible(true);
           $this->lazeBackup = $property->getValue();
       }
   
       public function tearDown(): void {
           $reflection = new ReflectionClass(laze::class);
           $property = $reflection->getProperty('store');
           $property->setAccessible(true);
           $property->setValue($this->lazeBackup);
           parent::tearDown();
       }
   }
   

2. If you are using `phpunit`, then use it with the parameter `--process-isolation` to run each test in a separate process.

   vendor/bin/phpunit --process-isolation
   

Utility of this library

• Lazy Evaluation: Optimizes resource usage by deferring value evaluation until needed, improving performance and load times.
• Immutability: Ensures values remain unchanged once evaluated, useful in concurrent environments and functional programming.
• Dependency Injection: Supports lazy initialization of dependencies, improving modularity and testing (e.g., mocking services).
• Configuration Management: Manages environment-specific or conditional configurations, evaluated only when required.
• Caching: Implements deferred caching, storing results only when needed, and supports multi-level caching with constraints.
• Event-Driven Programming: Facilitates deferred event handling, triggering actions only under certain conditions or upon request.
• Testing: Validates values with constraints in unit tests, and simulates complex environments with lazy-loaded dependencies.
• Security: Enforces data validation and security constraints before values are used, reducing risks.
• Declarative Programming: Supports declarative configurations that are evaluated on demand.
• Domain-Specific Languages (DSLs): Builds DSLs with declarative value definitions that execute in specific contexts.
• CI/CD: Defines dynamic configurations or scripts for CI/CD pipelines, evaluated conditionally based on environment state.

License

This project is licensed under the GNU GENERAL PUBLIC LICENSE. See the LICENSE file for details.

Contributing

Contributions are welcome! Please feel free to submit a Pull Request or open an Issue.

About

laze is developed and maintained by Divengine Software Solutions. If you find this library useful, please consider starring the repository and sharing it with others.