Added code from other project

Added the code from the other project

src/Exceptions/DanglingRelationships.php

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+<?php
+
+namespace nhalstead\Transferable\Exceptions;
+
+use Exception;
+use Illuminate\Database\Eloquent\Model;
+
+use nhalstead\Transferable\Interfaces\NoDanglingRelationships;
+
+/**
+ * Class DanglingRelationships
+ *
+ * This exception gets thrown if a protected Model is attempting to be deleted
+ *  but will leave its attached relationships that can be transferred set to be null.
+ *
+ * @package App\Exceptions
+ */
+class DanglingRelationships extends Exception
+{
+
+	public function __construct(Model $model, int $dangling)
+	{
+		$nameParts = explode("\\", get_class($model));
+		$name = $nameParts[ count($nameParts) -1 ];
+		$key = $model->getKey();
+
+		$keyword = "can";
+
+		if($model instanceof NoDanglingRelationships) {
+			$keyword = "must";
+		}
+
+		parent::__construct("Model $name($key) still has $dangling items that $keyword be transferred.", 1);
+	}
+
+}

src/Exceptions/FailedToResolveRelationship.php

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+<?php
+
+namespace nhalstead\Transferable\Exceptions;
+
+use Exception;
+
+class FailedToResolveRelationship extends Exception
+{
+    //
+}

src/Interfaces/NoDanglingRelationships.php

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+<?php
+
+namespace nhalstead\Transferable\Interfaces;
+
+
+/**
+ * Interface NoDanglingRelationships
+ * Used in combination with TransferableRelationship to prevent
+ *  deleting models that can't be deleted IF they have select relationships.
+ *
+ * @package App\Interfaces
+ */
+interface NoDanglingRelationships
+{
+
+}

src/Traits/TransferableRelationship.php

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+<?php
+
+namespace nhalstead\Transferable\Traits;
+
+use nhalstead\Transferable\Exceptions\DanglingRelationships;
+use nhalstead\Transferable\Exceptions\FailedToResolveRelationship;
+use nhalstead\Transferable\Interfaces\NoDanglingRelationships;
+use Illuminate\Support\Facades\DB;
+use Illuminate\Database\Eloquent\Model;
+use Illuminate\Database\Eloquent\Relations\BelongsTo;
+use Illuminate\Database\Eloquent\Relations\HasMany;
+use Illuminate\Database\Eloquent\Relations\HasManyThrough;
+use Illuminate\Database\Eloquent\Relations\HasOne;
+use Illuminate\Database\Eloquent\Relations\HasOneOrMany;
+use Illuminate\Database\Eloquent\Relations\HasOneThrough;
+use Illuminate\Database\Eloquent\Relations\MorphMany;
+use Illuminate\Database\Eloquent\Relations\MorphOne;
+use Illuminate\Database\Eloquent\Relations\MorphOneOrMany;
+use Illuminate\Database\Eloquent\Relations\MorphTo;
+use Illuminate\Database\Eloquent\Relations\Relation;
+
+
+trait TransferableRelationship
+{
+
+	public static function bootTransferableRelationship()
+	{
+		// Delete associated images if they exist.
+		static::deleting(function($model) {
+			/**
+			 * @var $model Model
+			 */
+
+			if ($model instanceof NoDanglingRelationships) {
+				$model->checkDangling();
+			}
+		});
+	}
+
+	/**
+	 * Get the transferable relationships.
+	 * @return array
+	 */
+	public function getTransferableRelationships()
+	{
+		return $this->transferable ?? [];
+	}
+
+	/**
+	 * Return the Fk column name for the given type.
+	 *
+	 * @param Relation $relation
+	 * @return string
+	 * @throws FailedToResolveRelationship|\Throwable
+	 */
+	private function getFk(Relation $relation) : string
+	{
+		/**
+		 * @link https://laravel.com/api/7.x/Illuminate/Database/Eloquent/Relations.html
+		 */
+		switch(get_class($relation)) {
+			case BelongsTo::class:
+			case MorphTo::class:
+				/**
+				 * @var $relation BelongsTo
+				 */
+				return $relation->getForeignKeyName();
+
+			case HasOneOrMany::class:
+			case HasOne::class:
+			case HasMany::class:
+			case MorphOneOrMany::class:
+			case MorphOne::class:
+			case MorphMany::class:
+				/**
+				 * @var $relation HasOneOrMany
+				 */
+				return $relation->getForeignKeyName();
+
+			// We only need to update the through Table
+			case HasManyThrough::class:
+			case HasOneThrough::class:
+				/**
+				 * @var $relation HasManyThrough
+				 */
+				return $relation->getForeignKeyName();
+
+			// Support for Morph relationship is going to become the real pain.
+			// case BelongsToMany::class:
+			// case MorphToMany::class:
+			// 	/**
+			// 	 * @var $relation BelongsToMany
+			// 	 */
+			// 	return $relation->getForeignKeyName();
+
+			default:
+				throw new FailedToResolveRelationship("Can't resolve relationship", $relation);
+		}
+	}
+
+	/**
+	 * Checks to see if any transferable relationships are left.
+	 * If so then throw an exception OR return a value.
+	 *
+	 * This is useful to ensure that important items are not set to null on this
+	 *  model's delete action.
+	 *
+	 * @param bool $throwException
+	 * @return int
+	 * @throws DanglingRelationships|\Throwable
+	 */
+	public function checkDangling(bool $throwException = true)
+	{
+		/**
+		 * @var $this Model
+		 */
+
+		$dangling = $this->countTransferable();
+		if($dangling !== 0) {
+			if($throwException) throw new DanglingRelationships($this, $dangling);
+			return $dangling;
+		}
+		return 0;
+	}
+
+	/**
+	 * Counts the transferable items
+	 *
+	 * @return int Rows that can be affected rows by this update
+	 */
+	public function countTransferable()
+	{
+		$affected = 0;
+
+		foreach ($this->getTransferableRelationships() as $transferable) {
+			$relation = call_user_func_array([$this, $transferable], []);
+
+			// Item is NOT a relationship and the class is not a Relationship
+			if(!is_subclass_of($relation, Relation::class)) continue;
+
+			/**
+			 * Update the relationship to from the old model to the new model
+			 *
+			 * @var $relation Relation
+			 */
+			$affected += $relation->count();
+		}
+
+		return $affected;
+	}
+
+	/**
+	 * Transfer the Ownership of the child relationship to another alike model.
+	 *
+	 * @param TransferableRelationship $newModel Must be moved to the same Class Type
+	 * @param bool $dryRun Run the update in a dry run mode
+	 * @return int Affected rows by this update
+	 * @throws FailedToResolveRelationship|\Throwable
+	 */
+	public function transferTo(self $newModel, bool $dryRun = false)
+	{
+		/**
+		 * @var $this Model
+		 * @var $newModel Model
+		 */
+		if($this->getKey() === $newModel->getKey()) return 0;
+
+		if($dryRun) DB::beginTransaction();
+
+		$affected = 0;
+
+		foreach ($this->getTransferableRelationships() as $transferable) {
+			$relation = call_user_func_array([$this, $transferable], []);
+
+			// Item is NOT a relationship and the class is not a Relationship
+			if(!is_subclass_of($relation, Relation::class)) continue;
+
+			$fkName = $this->getFk($relation);
+
+			/**
+			 * Update the relationship to from the old model to the new model
+			 *
+			 * @var $relation Relation
+			 */
+			$affected += $relation->update([
+				$fkName => $newModel->getKey()
+			]);
+		}
+
+		if($dryRun) DB::rollBack();
+		return $affected;
+	}
+
+}
+
+?>