Middleware

src/libs/Middleware.php

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+<?php
+
+namespace libs;
+
+interface Middleware
+{
+    public function handle($request, \Closure $next, ...$parameters);
+}
+
+class Pipeline
+{
+    protected array $middleware = [];
+    protected $request;
+
+    public function send($request): Object
+    {
+        $this->request = $request;
+        return $this;
+    }
+
+    public function through(array $middleware): Object
+    {
+        $this->middleware = $middleware;
+        return $this;
+    }
+
+    public function then(\Closure $destination)
+    {
+        $pipeline = array_reduce(
+            array_reverse($this->parseMiddleware($this->middleware)),
+            $this->carry(),
+            function ($request) use ($destination) {
+                return $destination($request);
+            }
+        );
+
+        return $pipeline($this->request);
+    }
+
+    protected function parseMiddleware(array $middleware)
+    {
+        return array_map(function ($m) {
+            return is_string($m) ? explode(':', $m, 2) : $m;
+        }, $middleware);
+    }
+
+    protected function carry()
+    {
+        return function ($stack, $middleware) {
+            return function ($request) use ($stack, $middleware) {
+                if (is_array($middleware)) {
+                    [$middleware, $parameters] = [
+                        $middleware[0],
+                        isset($middleware[1]) ? explode(',', $middleware[1]) : []
+                    ];
+                }
+
+                if (is_string($middleware)) {
+                    $middleware = new $middleware;
+                }
+
+                return $middleware->handle($request, $stack, ...$parameters ?? []);
+            };
+        };
+    }
+}

src/testMiddleware.php

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+<?php
+
+require "libs/autoload.php";
+
+class TrimStrings implements libs\Middleware
+{
+    public function handle($request, \Closure $next, ...$parameters)
+    {
+        foreach ($request as $key => $value) {
+            if (is_string($value)) {
+                $request[$key] = trim($value);
+            }
+        }
+
+        return $next($request);
+    }
+}
+
+class ucStrings implements libs\Middleware
+{
+    public function handle($request, \Closure $next, ...$parameters)
+    {
+        foreach ($request as $key => $value) {
+            if (is_string($value)) {
+                $request[$key] = ucwords($value);
+            }
+        }
+
+        return $next($request);
+    }
+}
+
+class ConvertEmptyStringsToNull implements libs\Middleware
+{
+    public function handle($request, \Closure $next, ...$parameters)
+    {
+        foreach ($request as $key => $value) {
+            if ($value === '') {
+                $request[$key] = null;
+            }
+        }
+
+        return $next($request);
+    }
+}
+
+class RoleCheck implements libs\Middleware
+{
+    public function handle($request, Closure $next, ...$parameters)
+    {
+        $role  = $parameters[0] ?? '';
+        $level = $parameters[1] ?? 'high';
+        if (!isset($request['user_role']) || $request['user_role'] !== $role) {
+            throw new Exception("Requires {$role} privileges (level: {$level})");
+        }
+
+        return $next($request);
+    }
+}
+
+// Create a request
+$request = [
+    'user_role' => 'admin',
+    'name' => '  john doe  ',
+    'email' => '  john@Example.com  ',
+    'age' => '44',
+    'active' => true,
+];
+
+// Process through middleware
+$response = (new libs\Pipeline)
+    ->send($request)
+    ->through([
+        'RoleCheck:admin,high',
+        TrimStrings::class,
+        ucStrings::class,
+        ConvertEmptyStringsToNull::class,
+    ])
+    ->then(function ($request) {
+        // Final handler
+        return $request;
+    });
+
+print_r($response);