Feat+Refactor: Introduce "Replacement" Feature

README.md

@@ -53,6 +53,32 @@ DB::setSystemVariables(['long_query_time' => 10.0, 'tx_isolation' => 'read-commi
 
 // Assign a variable on a different connection
 DB::connection('other_mysql_connection')->setSystemVariable('long_query_time', 10.0);
+
+// Run callback temporarily assigning a variable
+DB::usingSystemVariable('long_query_time', 10.0, function () {
+    /* ... */
+});
+
+// Run callback temporarily assigning multiple variables
+DB::usingSystemVariables(['long_query_time' => 10.0, 'tx_isolation' => 'read-committed'], function () {
+    /* ... */
+});
+
+// Run callback replacing current value
+// NOTE: You MUST declare closure return types.
+DB::usingSystemVariables(
+    [
+        'long_query_time' => function (float $currentValue): float {
+             return $currentValue + 5.0;
+        },
+        'sql_mode' => function (string $currentValue): string {
+             return str_replace('ONLY_FULL_GROUP_BY', '', $currentValue);
+        },
+    ],
+    function () {
+        /* ... */
+    }
+);
 ```
 
 **WARNING:**  
@@ -97,12 +123,14 @@ class MySqlConnection extends BaseMySqlConnection
 
     public function withoutForeignKeyChecks(callable $callback, ...$args)
     {
-        $this->setSystemVariable('foreign_key_checks', false);
-        try {
-            return $callback(...$args);
-        } finally {
-            $this->setSystemVariable('foreign_key_checks', true);
-        }
+        return $this->usingSystemVariable('foreign_key_checks', false, $callback, ...$args);
+    }
+
+    public function allowingPartialGroupBy(callable $callback, ...$args)
+    {
+        return $this->usingSystemVariable('sql_mode', function (string $mode): string {
+            return str_replace('ONLY_FULL_GROUP_BY', '', $mode);
+        }, $callback, ...$args);
     }
 }
 ```

src/ExpressionInterface.php

@@ -0,0 +1,40 @@
+<?php
+
+namespace Mpyw\LaravelMySqlSystemVariableManager;
+
+interface ExpressionInterface
+{
+    public const TYPE_INTEGER = 'integer';
+    public const TYPE_BOOLEAN = 'boolean';
+    public const TYPE_FLOAT = 'double';
+    public const TYPE_STRING = 'string';
+
+    public const GRAMMATICAL_TYPE_TO_STRING_TYPE = [
+        'int' => self::TYPE_INTEGER,
+        'bool' => self::TYPE_BOOLEAN,
+        'float' => self::TYPE_FLOAT,
+        'double' => self::TYPE_FLOAT,
+        'string' => self::TYPE_STRING,
+    ];
+
+    /**
+     * Return type.
+     *
+     * @return string
+     */
+    public function getType(): string;
+
+    /**
+     * Return PDO::PARAM_* type.s
+     *
+     * @return int
+     */
+    public function getParamType(): int;
+
+    /**
+     * Return placeholder for prepared statement.
+     *
+     * @return string
+     */
+    public function getPlaceholder(): string;
+}

src/ExpressionTrait.php

@@ -0,0 +1,55 @@
+<?php
+
+namespace Mpyw\LaravelMySqlSystemVariableManager;
+
+use PDO;
+
+/**
+ * Trait ExpressionTrait
+ */
+trait ExpressionTrait
+{
+    /**
+     * Return type.
+     *
+     * @return string
+     */
+    abstract public function getType(): string;
+
+    /**
+     * Return PDO::PARAM_* type.
+     *
+     * @return int
+     */
+    public function getParamType(): int
+    {
+        switch ($this->getType()) {
+            case ExpressionInterface::TYPE_INTEGER:
+                return PDO::PARAM_INT;
+            case ExpressionInterface::TYPE_BOOLEAN:
+                return PDO::PARAM_BOOL;
+            case ExpressionInterface::TYPE_FLOAT:
+            case ExpressionInterface::TYPE_STRING:
+            default:
+                return PDO::PARAM_STR;
+        }
+    }
+
+    /**
+     * Return a placeholder format.
+     *
+     * @return string
+     */
+    public function getPlaceholder(): string
+    {
+        switch ($this->getType()) {
+            case ExpressionInterface::TYPE_FLOAT:
+                return 'cast(? as decimal(65, 30))';
+            case ExpressionInterface::TYPE_INTEGER:
+            case ExpressionInterface::TYPE_BOOLEAN:
+            case ExpressionInterface::TYPE_STRING:
+            default:
+                return '?';
+        }
+    }
+}

src/ManagesSystemVariables.php

@@ -52,4 +52,36 @@ public function setSystemVariables(array $values, bool $memoizeForReconnect = tr
 
         return $this;
     }
+
+    /**
+     * Run callback temporarily setting MySQL system variable for both read and write PDOs.
+     * It is lazily executed for unresolved PDO instance.
+     *
+     * @param  string   $key
+     * @param  mixed    $value
+     * @param  callable $callback
+     * @param  mixed    ...$args
+     * @return $this
+     */
+    public function usingSystemVariable(string $key, $value, callable $callback, ...$args)
+    {
+        return $this->usingSystemVariables([$key => $value], $callback, ...$args);
+    }
+
+    /**
+     * Run callback temporarily setting MySQL system variables for both read and write PDOs.
+     * It is lazily executed for unresolved PDO instance.
+     *
+     * @param  array    $values
+     * @param  callable $callback
+     * @param  mixed    ...$args
+     * @return $this
+     */
+    public function usingSystemVariables(array $values, callable $callback, ...$args)
+    {
+        (new SystemVariableTemporaryAssigner($this->readPdo, $this->pdo))
+            ->using($values, $callback, ...$args);
+
+        return $this;
+    }
 }

src/Replacer.php

@@ -0,0 +1,83 @@
+<?php
+
+namespace Mpyw\LaravelMySqlSystemVariableManager;
+
+use InvalidArgumentException;
+use Mpyw\LaravelMySqlSystemVariableManager\Replacers\BooleanReplacerInterface;
+use Mpyw\LaravelMySqlSystemVariableManager\Replacers\CallbackBooleanReplacer;
+use Mpyw\LaravelMySqlSystemVariableManager\Replacers\CallbackFloatReplacer;
+use Mpyw\LaravelMySqlSystemVariableManager\Replacers\CallbackIntegerReplacer;
+use Mpyw\LaravelMySqlSystemVariableManager\Replacers\CallbackStringReplacer;
+use Mpyw\LaravelMySqlSystemVariableManager\Replacers\FloatReplacerInterface;
+use Mpyw\LaravelMySqlSystemVariableManager\Replacers\IntegerReplacerInterface;
+use Mpyw\LaravelMySqlSystemVariableManager\Replacers\StringReplacerInterface;
+
+class Replacer
+{
+    /**
+     * Create new int replacer for MySQL system variable.
+     *
+     * @param  callable                                                                   $callback
+     * @return \Mpyw\LaravelMySqlSystemVariableManager\Replacers\IntegerReplacerInterface
+     */
+    public static function int(callable $callback): IntegerReplacerInterface
+    {
+        return new CallbackIntegerReplacer($callback);
+    }
+
+    /**
+     * Create new bool replacer for MySQL system variable.
+     *
+     * @param  callable                                                                   $callback
+     * @return \Mpyw\LaravelMySqlSystemVariableManager\Replacers\BooleanReplacerInterface
+     */
+    public static function bool(callable $callback): BooleanReplacerInterface
+    {
+        return new CallbackBooleanReplacer($callback);
+    }
+
+    /**
+     * Create new float replacer for MySQL system variable.
+     *
+     * @param  callable                                                                 $callback
+     * @return \Mpyw\LaravelMySqlSystemVariableManager\Replacers\FloatReplacerInterface
+     */
+    public static function float(callable $callback): FloatReplacerInterface
+    {
+        return new CallbackFloatReplacer($callback);
+    }
+
+    /**
+     * Create new string replacer for MySQL system variable.
+     *
+     * @param  callable                                                                  $callback
+     * @return \Mpyw\LaravelMySqlSystemVariableManager\Replacers\StringReplacerInterface
+     */
+    public static function str(callable $callback): StringReplacerInterface
+    {
+        return new CallbackStringReplacer($callback);
+    }
+
+    /**
+     * Create new typed replacer for MySQL system variable.
+     *
+     * @param  string                                                      $type
+     * @param  bool|float|int|string                                       $callback
+     * @return \Mpyw\LaravelMySqlSystemVariableManager\ExpressionInterface
+     */
+    public static function as(string $type, $callback): ExpressionInterface
+    {
+        switch ($type) {
+            case ExpressionInterface::TYPE_INTEGER:
+                return static::int($callback);
+            case ExpressionInterface::TYPE_BOOLEAN:
+                return static::bool($callback);
+            case ExpressionInterface::TYPE_FLOAT:
+                return static::float($callback);
+            case ExpressionInterface::TYPE_STRING:
+                return static::str($callback);
+            default:
+                throw new InvalidArgumentException('The return type must be one of "integer", "boolean", "double" or "string".');
+        }
+    }
+}

src/Replacers/BooleanReplacerInterface.php

@@ -0,0 +1,16 @@
+<?php
+
+namespace Mpyw\LaravelMySqlSystemVariableManager\Replacers;
+
+use Mpyw\LaravelMySqlSystemVariableManager\ExpressionInterface;
+
+interface BooleanReplacerInterface extends ExpressionInterface
+{
+    /**
+     * Replace boolean variable value.
+     *
+     * @param  bool $value
+     * @return bool
+     */
+    public function replace(bool $value): bool;
+}

src/Replacers/CallbackBooleanReplacer.php

@@ -0,0 +1,47 @@
+<?php
+
+namespace Mpyw\LaravelMySqlSystemVariableManager\Replacers;
+
+use Mpyw\LaravelMySqlSystemVariableManager\ExpressionInterface;
+use Mpyw\LaravelMySqlSystemVariableManager\ExpressionTrait;
+
+class CallbackBooleanReplacer implements BooleanReplacerInterface
+{
+    use ExpressionTrait;
+
+    /**
+     * @var callable
+     */
+    protected $callback;
+
+    /**
+     * ClosureBooleanReplacer constructor.
+     *
+     * @param callable $callback
+     */
+    public function __construct(callable $callback)
+    {
+        $this->callback = $callback;
+    }
+
+    /**
+     * Replace boolean variable value.
+     *
+     * @param  bool $value
+     * @return bool
+     */
+    public function replace(bool $value): bool
+    {
+        return ($this->callback)($value);
+    }
+
+    /**
+     * Return type.
+     *
+     * @return string
+     */
+    public function getType(): string
+    {
+        return ExpressionInterface::TYPE_BOOLEAN;
+    }
+}

src/Replacers/CallbackFloatReplacer.php

@@ -0,0 +1,47 @@
+<?php
+
+namespace Mpyw\LaravelMySqlSystemVariableManager\Replacers;
+
+use Mpyw\LaravelMySqlSystemVariableManager\ExpressionInterface;
+use Mpyw\LaravelMySqlSystemVariableManager\ExpressionTrait;
+
+class CallbackFloatReplacer implements FloatReplacerInterface
+{
+    use ExpressionTrait;
+
+    /**
+     * @var callable
+     */
+    protected $callback;
+
+    /**
+     * ClosureFloatReplacer constructor.
+     *
+     * @param callable $callback
+     */
+    public function __construct(callable $callback)
+    {
+        $this->callback = $callback;
+    }
+
+    /**
+     * Replace float variable value.
+     *
+     * @param  float $value
+     * @return float
+     */
+    public function replace(float $value): float
+    {
+        return ($this->callback)($value);
+    }
+
+    /**
+     * Return type.
+     *
+     * @return string
+     */
+    public function getType(): string
+    {
+        return ExpressionInterface::TYPE_FLOAT;
+    }
+}