feat: add underscore functions

Author: adhocore

src/UnderscoreFunction.php

@@ -0,0 +1,107 @@
+<?php
+
+namespace Ahc\Underscore;
+
+class UnderscoreFunction extends UnderscoreArray
+{
+    /**
+     * Returns a callable which when invoked caches the result for given arguments
+     * and reuses that result in subsequent calls.
+     *
+     * @param callable $fn The main callback.
+     *
+     * @return mixed
+     */
+    public function memoize(callable $fn)
+    {
+        static $memo = [];
+
+        return function () use (&$memo, $fn) {
+            $hash = \md5(\json_encode($args = \func_get_args()));
+
+            if (isset($memo[$hash])) {
+                return $memo[$hash];
+            }
+
+            return $memo[$hash] = \call_user_func_array($fn, $args);
+        };
+    }
+
+    /**
+     * Cache the result of callback for given arguments and reuse that in subsequent call.
+     *
+     * @param callable $fn   The main callback.
+     * @param int      $wait The time to wait in millisec.
+     *
+     * @return mixed
+     */
+    public function delay(callable $fn, $wait)
+    {
+        return function () use ($fn, $wait) {
+            \usleep(1000 * $wait);
+
+            return \call_user_func_array($fn, \func_get_args());
+        };
+    }
+
+    /**
+     * Returns a callable that wraps given callable which can be only invoked
+     * at most once per given $wait threshold.
+     *
+     * @param callable $fn   The main callback.
+     * @param int      $wait The callback will only be triggered at most once within this period.
+     *
+     * @return mixed The return set of callback if runnable else the previous cache.
+     */
+    public function throttle(callable $fn, $wait)
+    {
+        static $previous = 0;
+        static $result   = null;
+
+        return function () use ($fn, &$previous, &$result, &$wait) {
+            $now = $this->now();
+
+            if (!$previous) {
+                $previous = $now;
+            }
+
+            $remaining = $wait - ($now - $previous);
+
+            if ($remaining <= 0 || $remaining > $wait) {
+                $previous = $now;
+                $result   = \call_user_func_array($fn, \func_get_args());
+            }
+
+            return $result;
+        };
+    }
+
+    /**
+     * Returns a function that is the composition of a list of functions,
+     * each consuming the return value of the function that follows.
+     *
+     * Note that last function is executed first.
+     *
+     * @param callable $fn1
+     * @param callable $fn2
+     * @param ...callable|null $fn3 And so on!
+     *
+     * @return mixed Final result value.
+     */
+    public function compose(callable $fn1, callable $fn2 /* , callable $fn3 = null */)
+    {
+        $fns   = \func_get_args();
+        $start = \func_num_args() - 1;
+
+        return function () use ($fns, $start) {
+            $i      = $start;
+            $result = \call_user_func_array($fns[$start], \func_get_args());
+
+            while ($i--) {
+                $result = $fns[$i]($result);
+            }
+
+            return $result;
+        };
+    }
+}