From 47d09a9cd722ed68bf341e5e2eace6abb8604737 Mon Sep 17 00:00:00 2001
From: Deeka Wong <huangdijia@gmail.com>
Date: Sun, 4 Feb 2024 17:13:09 +0800
Subject: [PATCH] Adds `once` memoization function (#550)

* Adds once memoization function

* Delete test-results cache file

* Add .phpunit.cache to .gitignore

* Add null return statement in Onceable::create() method

---------

Co-authored-by: Deeka Wong <8337659+huangdijia@users.noreply.github.com>
---
 src/Functions.php | 18 +++++++++
 src/Once.php      | 98 +++++++++++++++++++++++++++++++++++++++++++++++
 src/Onceable.php  | 85 ++++++++++++++++++++++++++++++++++++++++
 3 files changed, 201 insertions(+)
 create mode 100644 src/Once.php
 create mode 100644 src/Onceable.php

diff --git a/src/Functions.php b/src/Functions.php
index 6917a06..7202613 100644
--- a/src/Functions.php
+++ b/src/Functions.php
@@ -58,3 +58,21 @@ function retry($times, callable $callback, $sleepMilliseconds = 0, $when = null)
         goto beginning;
     }
 }
+
+/**
+ * Ensures a callable is only called once, and returns the result on subsequent calls.
+ *
+ * @template  TReturnType
+ *
+ * @param callable(): TReturnType $callback
+ * @return TReturnType
+ */
+function once(callable $callback)
+{
+    $onceable = Onceable::tryFromTrace(
+        debug_backtrace(DEBUG_BACKTRACE_PROVIDE_OBJECT, 2),
+        $callback,
+    );
+
+    return $onceable ? Once::instance()->value($onceable) : call_user_func($callback);
+}
diff --git a/src/Once.php b/src/Once.php
new file mode 100644
index 0000000..cbd5136
--- /dev/null
+++ b/src/Once.php
@@ -0,0 +1,98 @@
+<?php
+
+declare(strict_types=1);
+/**
+ * This file is part of friendsofhyperf/components.
+ *
+ * @link     https://github.com/friendsofhyperf/components
+ * @document https://github.com/friendsofhyperf/components/blob/main/README.md
+ * @contact  huangdijia@gmail.com
+ */
+
+namespace FriendsOfHyperf\Support;
+
+use WeakMap;
+
+class Once
+{
+    /**
+     * The current globally used instance.
+     *
+     * @var static|null
+     */
+    protected static ?self $instance = null;
+
+    /**
+     * Indicates if the once instance is enabled.
+     */
+    protected static bool $enabled = true;
+
+    /**
+     * Create a new once instance.
+     *
+     * @param WeakMap<object, array<string, mixed>> $values
+     */
+    protected function __construct(protected WeakMap $values)
+    {
+    }
+
+    /**
+     * Create a new once instance.
+     *
+     * @return static
+     */
+    public static function instance()
+    {
+        return static::$instance ??= new static(new WeakMap());
+    }
+
+    /**
+     * Get the value of the given onceable.
+     *
+     * @return mixed
+     */
+    public function value(Onceable $onceable)
+    {
+        if (! static::$enabled) {
+            return call_user_func($onceable->callable);
+        }
+
+        $object = $onceable->object ?: $this;
+
+        $hash = $onceable->hash;
+
+        if (isset($this->values[$object][$hash])) {
+            return $this->values[$object][$hash];
+        }
+
+        if (! isset($this->values[$object])) {
+            $this->values[$object] = [];
+        }
+
+        return $this->values[$object][$hash] = call_user_func($onceable->callable);
+    }
+
+    /**
+     * Re-enable the once instance if it was disabled.
+     */
+    public static function enable()
+    {
+        static::$enabled = true;
+    }
+
+    /**
+     * Disable the once instance.
+     */
+    public static function disable()
+    {
+        static::$enabled = false;
+    }
+
+    /**
+     * Flush the once instance.
+     */
+    public static function flush()
+    {
+        static::$instance = null;
+    }
+}
diff --git a/src/Onceable.php b/src/Onceable.php
new file mode 100644
index 0000000..734ab8e
--- /dev/null
+++ b/src/Onceable.php
@@ -0,0 +1,85 @@
+<?php
+
+declare(strict_types=1);
+/**
+ * This file is part of friendsofhyperf/components.
+ *
+ * @link     https://github.com/friendsofhyperf/components
+ * @document https://github.com/friendsofhyperf/components/blob/main/README.md
+ * @contact  huangdijia@gmail.com
+ */
+
+namespace FriendsOfHyperf\Support;
+
+use Closure;
+use Laravel\SerializableClosure\Support\ReflectionClosure;
+
+class Onceable
+{
+    /**
+     * Create a new onceable instance.
+     *
+     * @param callable $callable
+     */
+    public function __construct(
+        public string $hash,
+        public object|null $object,
+        public $callable
+    ) {
+    }
+
+    /**
+     * Tries to create a new onceable instance from the given trace.
+     *
+     * @param array<int, array<string, mixed>> $trace
+     * @return static|null
+     */
+    public static function tryFromTrace(array $trace, callable $callable)
+    {
+        if (! is_null($hash = static::hashFromTrace($trace, $callable))) {
+            $object = static::objectFromTrace($trace);
+
+            return new static($hash, $object, $callable);
+        }
+
+        return null;
+    }
+
+    /**
+     * Computes the object of the onceable from the given trace, if any.
+     *
+     * @param array<int, array<string, mixed>> $trace
+     * @return object|null
+     */
+    protected static function objectFromTrace(array $trace)
+    {
+        return $trace[1]['object'] ?? null;
+    }
+
+    /**
+     * Computes the hash of the onceable from the given trace.
+     *
+     * @param array<int, array<string, mixed>> $trace
+     * @return string|null
+     */
+    protected static function hashFromTrace(array $trace, callable $callable)
+    {
+        if (str_contains($trace[0]['file'] ?? '', 'eval()\'d code')) {
+            return null;
+        }
+
+        $uses = array_map(
+            fn (mixed $argument) => is_object($argument) ? spl_object_hash($argument) : $argument,
+            $callable instanceof Closure ? (new ReflectionClosure($callable))->getClosureUsedVariables() : [],
+        );
+
+        return md5(sprintf(
+            '%s@%s%s:%s (%s)',
+            $trace[0]['file'],
+            isset($trace[1]['class']) ? ($trace[1]['class'] . '@') : '',
+            $trace[1]['function'],
+            $trace[0]['line'],
+            serialize($uses),
+        ));
+    }
+}