Create initial structure and classes

.gitignore

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+/log/
+/vendor/
+
+.php_cs.cache

composer.json

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+{
+    "name": "anwinged/reason",
+    "type": "library",
+    "require": {},
+    "require-dev": {
+        "phpunit/phpunit": "^6.0"
+    },
+    "license": "MIT",
+    "authors": [
+        {
+            "name": "Anton Vakhrushev",
+            "email": "anwinged@ya.ru"
+        }
+    ],
+    "autoload": {
+        "psr-4": {
+            "Anwinged\\Reason\\": "src/"
+        }
+    }
+}

phpunit.xml.dist

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+<phpunit bootstrap="vendor/autoload.php">
+    <testsuites>
+        <testsuite name="reason">
+            <directory>tests</directory>
+        </testsuite>
+    </testsuites>
+    <filter>
+        <whitelist>
+            <directory suffix=".php">src</directory>
+        </whitelist>
+    </filter>
+    <logging>
+        <log type="coverage-html" target="log/coverage" />
+        <log type="testdox-html" target="log/testdox.html" />
+    </logging>
+</phpunit>

src/Reason.php

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+<?php
+
+declare(strict_types=1);
+
+namespace Anwinged\Reason;
+
+class Reason
+{
+    /**
+     * @var ReasonStatusInterface
+     */
+    private $status;
+
+    /**
+     * @var string[]
+     */
+    private $messages;
+
+    /**
+     * @param ReasonStatusInterface $status
+     * @param string[]              $messages
+     */
+    public function __construct(ReasonStatusInterface $status, array $messages)
+    {
+        $this->status = $status;
+        $this->messages = $messages;
+    }
+
+    /**
+     * Clones the reason.
+     */
+    public function __clone()
+    {
+        $this->status = clone $this->status;
+    }
+
+    /**
+     * @return ReasonStatusInterface
+     */
+    public function getStatus(): ReasonStatusInterface
+    {
+        return clone $this->status;
+    }
+
+    /**
+     * @return string[]
+     */
+    public function getMessages(): array
+    {
+        return $this->messages;
+    }
+
+    /**
+     * Appends reason to current and returns new reason.
+     *
+     * Reason with highest weighs wins.
+     *
+     * If other reason has highest weight, then it will be returned without changes.
+     * If weights are equal, then messages will be merged. Otherwise,
+     * returns current reason.
+     *
+     * Don't change original objects.
+     *
+     * @param Reason $other
+     *
+     * @return self
+     */
+    public function andX(Reason $other): self
+    {
+        if ($other->getStatus()->getWeight() > $this->status->getWeight()) {
+            return clone $other;
+        }
+
+        if ($other->getStatus()->getWeight() === $this->status->getWeight()) {
+            return $this->withMessages($other->getMessages());
+        }
+
+        return clone $this;
+    }
+
+    /**
+     * Join reason to current and return new reason.
+     *
+     * Reason with lowest weight wins.
+     *
+     * If other reason has lowest weight, then it will be returned without changes.
+     * If weights are equal, then messages will be merged. Otherwise,
+     * returns current reason.
+     *
+     * @param Reason $other
+     *
+     * @return self
+     */
+    public function orX(Reason $other): self
+    {
+        if ($other->getStatus()->getWeight() < $this->status->getWeight()) {
+            return clone $other;
+        }
+
+        if ($other->getStatus()->getWeight() === $this->status->getWeight()) {
+            return $this->withMessages($other->getMessages());
+        }
+
+        return clone $this;
+    }
+
+    /**
+     * @param string[] $messages
+     *
+     * @return self
+     */
+    private function withMessages(array $messages): self
+    {
+        $reason = clone $this;
+        $reason->messages = array_merge($reason->messages, $messages);
+
+        return $reason;
+    }
+}

src/ReasonStatusInterface.php

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+<?php
+
+declare(strict_types=1);
+
+namespace Anwinged\Reason;
+
+interface ReasonStatusInterface
+{
+    /**
+     * @return bool
+     */
+    public function isSuccess(): bool;
+
+    /**
+     * @return bool
+     */
+    public function isFail(): bool;
+
+    /**
+     * @return int
+     */
+    public function getWeight(): int;
+}

src/Status/BooleanStatus.php

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+<?php
+
+declare(strict_types=1);
+
+namespace Anwinged\Reason\Status;
+
+use Anwinged\Reason\ReasonStatusInterface;
+
+class BooleanStatus implements ReasonStatusInterface
+{
+    /**
+     * @var bool
+     */
+    private $value;
+
+    /**
+     * @param bool $value
+     */
+    public function __construct(bool $value)
+    {
+        $this->value = $value;
+    }
+
+    /**
+     * @return bool
+     */
+    public function isSuccess(): bool
+    {
+        return $this->value;
+    }
+
+    /**
+     * @return bool
+     */
+    public function isFail(): bool
+    {
+        return !$this->value;
+    }
+
+    /**
+     * @return int
+     */
+    public function getWeight(): int
+    {
+        return $this->value ? 0 : 1;
+    }
+}

tests/BooleanReasonTest.php

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+<?php
+
+declare(strict_types=1);
+
+namespace Anwinged\Reason;
+
+use Anwinged\Reason\Status\BooleanStatus;
+use PHPUnit\Framework\TestCase;
+
+class BooleanReasonTest extends TestCase
+{
+    /**
+     * @var Reason
+     */
+    private $trueReason;
+
+    /**
+     * @var Reason
+     */
+    private $falseReason;
+
+    public function setUp()
+    {
+        $this->trueReason = new Reason(new BooleanStatus(true), ['yes', 'ok']);
+        $this->falseReason = new Reason(new BooleanStatus(false), ['no', 'fail']);
+    }
+
+    public function testCanBeCloned()
+    {
+        $cloned = clone $this->trueReason;
+
+        $this->assertNotSame($cloned, $this->trueReason);
+    }
+
+    public function testCanBeAppended()
+    {
+        $first = $this->trueReason->orX($this->falseReason);
+
+        $this->assertTrue($first->getStatus()->isSuccess());
+        $this->assertEquals(['yes', 'ok'], $first->getMessages());
+
+        $second = $this->falseReason->orX($this->trueReason);
+
+        $this->assertTrue($second->getStatus()->isSuccess());
+        $this->assertEquals(['yes', 'ok'], $second->getMessages());
+    }
+
+    public function testCanBeJoined()
+    {
+        $first = $this->trueReason->andX($this->falseReason);
+
+        $this->assertTrue($first->getStatus()->isFail());
+        $this->assertEquals(['no', 'fail'], $first->getMessages());
+
+        $second = $this->falseReason->andX($this->trueReason);
+
+        $this->assertTrue($second->getStatus()->isFail());
+        $this->assertEquals(['no', 'fail'], $second->getMessages());
+    }
+
+    public function testMessageMergedWhileReasonsAppended()
+    {
+        $first = new Reason(new BooleanStatus(true), ['yes', 'ok']);
+        $second = new Reason(new BooleanStatus(true), ['good', 'success']);
+
+        $appended = $first->orX($second);
+
+        $this->assertTrue($appended->getStatus()->isSuccess());
+        $this->assertEquals(['yes', 'ok', 'good', 'success'], $appended->getMessages());
+    }
+
+    public function testMessageMergedWhileReasonsJoined()
+    {
+        $first = new Reason(new BooleanStatus(true), ['yes', 'ok']);
+        $second = new Reason(new BooleanStatus(true), ['good', 'success']);
+
+        $joined = $first->andX($second);
+
+        $this->assertTrue($joined->getStatus()->isSuccess());
+        $this->assertEquals(['yes', 'ok', 'good', 'success'], $joined->getMessages());
+    }
+}