Add Context Value

README.md

@@ -40,6 +40,8 @@ zenpipe(100)
 4. [Usage](#usage)
    - [Pipeline Operations](#pipeline-operations)
    - [Class Methods as Operations](#class-methods-as-operations)
+   - [Context Passing](#context-passing)
+   - [Exception Handling](#exception-handling)
    - [More Examples](#more-examples)
 5. [API Reference](#api-reference)
 6. [Contributing](#contributing)
@@ -58,10 +60,11 @@ composer require dynamik-dev/zenpipe-php
 ## Usage
 ### Pipeline Operations
 
-Pipeline operations are functions that take an input and return a processed value. Each operation can receive up to three parameters:
+Pipeline operations are functions that take an input and return a processed value. Each operation can receive up to four parameters:
 - `$input`: The value being processed
 - `$next`: A callback to pass the value to the next operation
 - `$return`: (Optional) A callback to exit the pipeline early with a value
+- `$context`: (Optional) A shared context object passed to all operations
 
 #### Basic Operation Example
 Let's build an input sanitization pipeline:
@@ -157,6 +160,77 @@ $pipeline = zenpipe()
     ]);
 ```
 
+### Context Passing
+
+You can pass a shared context object to all operations using `withContext()`. This is useful for sharing state, configuration, or dependencies across the pipeline without threading them through the value.
+
+```php
+// Use any object as context - your own DTO, stdClass, or array
+class RequestContext
+{
+    public function __construct(
+        public string $userId,
+        public array $permissions,
+        public array $logs = []
+    ) {}
+}
+
+$context = new RequestContext(
+    userId: 'user-123',
+    permissions: ['read', 'write']
+);
+
+$result = zenpipe(['action' => 'update', 'data' => [...]])
+    ->withContext($context)
+    ->pipe(function ($request, $next, $return, RequestContext $ctx) {
+        if (!in_array('write', $ctx->permissions)) {
+            return $return(['error' => 'Unauthorized']);
+        }
+        $ctx->logs[] = "Permission check passed for {$ctx->userId}";
+        return $next($request);
+    })
+    ->pipe(function ($request, $next, $return, RequestContext $ctx) {
+        $ctx->logs[] = "Processing {$request['action']}";
+        return $next([...$request, 'processed_by' => $ctx->userId]);
+    })
+    ->process();
+
+// Context is mutable - logs are accumulated across operations
+// $context->logs = ['Permission check passed for user-123', 'Processing update']
+```
+
+Type hint your context parameter in the operation signature for IDE support:
+
+```php
+/** @var ZenPipe<array, RequestContext> */
+$pipeline = zenpipe()
+    ->withContext(new RequestContext(...))
+    ->pipe(fn($value, $next, $return, RequestContext $ctx) => ...);
+```
+
+### Exception Handling
+
+Use `catch()` to handle exceptions gracefully without breaking the pipeline:
+
+```php
+$result = zenpipe($userData)
+    ->pipe(fn($data, $next) => $next(validateInput($data)))
+    ->pipe(fn($data, $next) => $next(processPayment($data))) // might throw
+    ->pipe(fn($data, $next) => $next(sendConfirmation($data)))
+    ->catch(fn(Throwable $e, $originalValue) => [
+        'error' => $e->getMessage(),
+        'input' => $originalValue,
+    ])
+    ->process();
+```
+
+The catch handler receives:
+- `$e`: The thrown exception (`Throwable`)
+- `$value`: The original input value passed to `process()`
+- `$context`: The context set via `withContext()` (null if not set)
+
+If no catch handler is set, exceptions propagate normally.
+
 ### More Examples
 
 #### RAG Processes

docs/API.md

@@ -35,6 +35,47 @@ Static factory method to create a new pipeline instance.
   - `$initialValue` (mixed|null): The initial value to be processed through the pipeline.
 - **Returns:** A new `ZenPipe` instance.
 
+### withContext()
+
+```php
+public function withContext(mixed $context): self
+```
+
+Sets a context object that will be passed to all operations as the fourth parameter.
+
+- **Parameters:**
+  - `$context` (mixed): Any value to be passed as context (object, array, DTO, etc.)
+- **Returns:** The `ZenPipe` instance for method chaining.
+
+**Example:**
+```php
+$pipeline = zenpipe($value)
+    ->withContext(new MyContext())
+    ->pipe(fn($v, $next, $return, MyContext $ctx) => $next($v));
+```
+
+### catch()
+
+```php
+public function catch(callable $handler): self
+```
+
+Sets an exception handler for the pipeline.
+
+- **Parameters:**
+  - `$handler` (callable): A function that receives `(Throwable $e, mixed $originalValue, mixed $context)` and returns a fallback value.
+- **Returns:** The `ZenPipe` instance for method chaining.
+
+**Example:**
+```php
+$pipeline = zenpipe($value)
+    ->withContext($myContext)
+    ->pipe(fn($v, $next) => $next(riskyOperation($v)))
+    ->catch(fn($e, $value, $ctx) => ['error' => $e->getMessage()]);
+```
+
+If an exception occurs and no catch handler is set, the exception propagates normally.
+
 ### pipe()
 
 ```php
@@ -51,6 +92,13 @@ Adds an operation to the pipeline.
 - **Returns:** The `ZenPipe` instance for method chaining.
 - **Throws:** `\InvalidArgumentException` if the specified class does not exist.
 
+**Operation Parameters:**
+Operations receive up to four parameters:
+1. `$value` - The current value being processed
+2. `$next` - Callback to pass value to next operation
+3. `$return` - Callback to exit pipeline early with a value
+4. `$context` - The context set via `withContext()` (null if not set)
+
 ### process()
 
 ```php

phpstan.neon

@@ -6,7 +6,10 @@ parameters:
         - vendor
     ignoreErrors:
         - '#PHPDoc tag @var#'
-        - 
+        -
             message: '#Template type T of function zenpipe\(\) is not referenced in a parameter.#'
             path: src/helpers.php
+        -
+            message: '#Template type TContext of function zenpipe\(\) is not referenced in a parameter.#'
+            path: src/helpers.php
     reportUnmatchedIgnoredErrors: false

src/ZenPipe.php

@@ -4,19 +4,54 @@
 
 /**
  * @template T
+ * @template TContext
  */
 class ZenPipe
 {
     /** @var array<callable|array{class-string, string}> */
     protected array $operations = [];
 
+    /** @var TContext|null */
+    protected mixed $context = null;
+
+    /** @var callable|null */
+    protected $exceptionHandler = null;
+
     public function __construct(protected mixed $initialValue = null)
     {
     }
 
+    /**
+     * Set an exception handler for the pipeline.
+     *
+     * @param  callable(\Throwable, mixed, TContext|null): mixed  $handler
+     * @return self<T, TContext>
+     */
+    public function catch(callable $handler): self
+    {
+        $this->exceptionHandler = $handler;
+
+        return $this;
+    }
+
+    /**
+     * Set the context to be passed to each operation.
+     *
+     * @template TNewContext
+     *
+     * @param  TNewContext  $context
+     * @return self<T, TNewContext>
+     */
+    public function withContext(mixed $context): self
+    {
+        $this->context = $context;
+
+        return $this;
+    }
+
     /**
      * @param mixed|null $initialValue
-     * @return self<T>
+     * @return self<T, TContext>
      */
     public static function make(mixed $initialValue = null): self
     {
@@ -25,7 +60,7 @@ public static function make(mixed $initialValue = null): self
 
     /**
      * @param  callable|array{class-string, string}  $operation
-     * @return self<T>
+     * @return self<T, TContext>
      */
     public function pipe($operation): self
     {
@@ -78,6 +113,7 @@ public function __invoke($initialValue)
      * @param  T|null  $initialValue
      * @return T
      * @throws \InvalidArgumentException
+     * @throws \Throwable
      */
     public function process($initialValue = null)
     {
@@ -93,17 +129,24 @@ public function process($initialValue = null)
             $this->passThroughOperation()
         );
 
-        return $pipeline($value);
+        try {
+            return $pipeline($value);
+        } catch (\Throwable $e) {
+            if ($this->exceptionHandler !== null) {
+                return ($this->exceptionHandler)($e, $value, $this->context);
+            }
+            throw $e;
+        }
     }
 
     /**
      * This method is used to carry the value through the pipeline.
      * It wraps the next operation in a closure that can handle both
      * static method calls and regular callables.
      *
-     * The operation can now accept a third parameter for early return:
-     * - For callables: function($value, $next, $return)
-     * - For class methods: method($value, $next, $return)
+     * Operations can accept up to four parameters:
+     * - For callables: function($value, $next, $return, $context)
+     * - For class methods: method($value, $next, $return, $context)
      *
      * @return callable
      */
@@ -120,10 +163,10 @@ public function carry(): callable
                     $method = $operation[1];
                     $instance = new $class();
 
-                    return $instance->$method($value, $next, $return);
+                    return $instance->$method($value, $next, $return, $this->context);
                 }
 
-                return $operation($value, $next, $return);
+                return $operation($value, $next, $return, $this->context);
             };
         };
     }

src/helpers.php

@@ -7,7 +7,9 @@
      * Create a new ZenPipe instance.
      *
      * @template T
-     * @return ZenPipe<T>
+     * @template TContext
+     *
+     * @return ZenPipe<T, TContext>
      */
     function zenpipe(mixed $initialValue = null): ZenPipe
     {