<?php

namespace Examyou\RestAPI;

use Carbon\Carbon;
use Closure;
use DateTimeInterface;
use Examyou\RestAPI\Exceptions\RelatedResourceNotFoundException;
use Examyou\RestAPI\Exceptions\ResourceNotFoundException;
use Illuminate\Database\Eloquent\Model;
use Illuminate\Database\Eloquent\Relations\BelongsTo;
use Illuminate\Database\Eloquent\Relations\BelongsToMany;
use Illuminate\Database\Eloquent\Relations\HasMany;
use Illuminate\Database\Eloquent\Relations\HasOne;
use Illuminate\Database\Eloquent\Relations\Relation;

class ApiModel extends Model
{

	/**
	 * List of fields that are visible by default. Only these fields
	 * are selected and returned from database
	 *
	 * @var array
	 */
	protected $default = ["id"];

	/**
	 * List of fields that are always hidden. Unless modified, these
	 * fields are not visible when object is serialised. To comply with
	 * Rest architecture, its recommended to hide all relation fields
	 * (like, user_id, student_id)
	 *
	 * @var array
	 */
	protected $hidden = ["created_at", "updated_at", "pivot"];

	/**
	 * List of fields on which filters are allowed to be applied. For security
	 * reasons we cannot allow filters to be allowed on arbitrary fields
	 * @var array
	 */
	protected $filterable = ["id"];

	/**
	 * List of relation attributes found during parsing of request, to be used during saving action
	 * @var array
	 */
	protected $relationAttributes = [];

	protected $guarded = [];

	/**
	 * Raw attributes as sent in request. To be used in setters of various attributes
	 * @var array
	 */
	protected $raw = [];

	//region Metadata functions

	/**
	 * Name of table of this model
	 *
	 * @return string
	 */
	public static function getTableName()
	{
		return (new static)->table;
	}

	/**
	 * Date fields in this model
	 *
	 * @return array
	 */
	public static function getDateFields()
	{
		return (new static)->dates;
	}

	/**
	 * List of custom fields (attributes) that are appended by default
	 * ($appends array)
	 *
	 * @return array
	 */
	public static function getAppendFields()
	{
		return (new static)->appends;
	}

	/**
	 * List of fields to display by default ($defaults array)
	 *
	 * @return array
	 */
	public static function getDefaultFields()
	{
		return (new static)->default;
	}

	/**
	 * Returns list of fields on which filter is allowed to be applied
	 *
	 * @return array
	 */
	public static function getFilterableFields()
	{
		return (new static)->filterable;
	}

	/**
	 * Returns list of fields on which hashing is allowed to be applied
	 *
	 * @return array
	 */
	public static function getHashableFields()
	{
		return (new static)->hashable;
	}

	/**
	 * Checks if given relation exists on the model
	 *
	 * @param $relation
	 * @return bool
	 */
	public static function relationExists($relation)
	{
		return method_exists(new static(), $relation);
	}

	//endregion

	/**
	 * Prepare a date for array / JSON serialization. Override base method in Model to suite our needs
	 *
	 * @param  \DateTime  $date
	 * @return string
	 */
	protected function serializeDate(\DateTimeInterface $date)
	{
		return $date->format("c");
	}

	/**
	 * Return a timestamp as DateTime object.
	 *
	 * @param  mixed  $value
	 * @return \Carbon\Carbon
	 */
	protected function asDateTime($value)
	{
		// If this value is already a Carbon instance, we shall just return it as is.
		// This prevents us having to re-instantiate a Carbon instance when we know
		// it already is one, which wouldn't be fulfilled by the DateTime check.
		if ($value instanceof Carbon) {
			return $value;
		}

		// If the value is already a DateTime instance, we will just skip the rest of
		// these checks since they will be a waste of time, and hinder performance
		// when checking the field. We will just return the DateTime right away.
		if ($value instanceof DateTimeInterface) {
			return new Carbon(
				$value->format('Y-m-d H:i:s.u'),
				$value->getTimeZone()
			);
		}

		// If this value is an integer, we will assume it is a UNIX timestamp's value
		// and format a Carbon object from this timestamp. This allows flexibility
		// when defining your date fields as they might be UNIX timestamps here.
		if (is_numeric($value)) {
			return Carbon::createFromTimestamp($value);
		}

		// If the value is in simply year, month, day format, we will instantiate the
		// Carbon instances from that format. Again, this provides for simple date
		// fields on the database, while still supporting Carbonized conversion.
		if (preg_match('/^(\d{4})-(\d{1,2})-(\d{1,2})$/', $value)) {
			return Carbon::createFromFormat('Y-m-d', $value)->startOfDay();
		}

		// Parse ISO 8061 date
		if (preg_match('/^(\d{4})-(\d{2})-(\d{2})T(\d{2}):(\d{2}):(\d{2})\\+(\d{2}):(\d{2})$/', $value)) {
			return Carbon::createFromFormat('Y-m-d\TH:i:s+P', $value);
		} elseif (preg_match('/^(\d{4})-(\d{1,2})-(\d{1,2}T(\d{2}):(\d{2}):(\d{2})\\.(\d{1,3})Z)$/', $value)) {
			return Carbon::createFromFormat('Y-m-d\TH:i:s.uZ', $value);
		}

		// Finally, we will just assume this date is in the format used by default on
		// the database connection and use that format to create the Carbon object
		// that is returned back out to the developers after we convert it here.
		return Carbon::createFromFormat($this->getDateFormat(), $value);
	}

	/**
	 * Eagerly load the relationship on a set of models.
	 *
	 * @param  array  $models
	 * @param  string  $name
	 * @param  \Closure  $constraints
	 * @return array
	 */
	protected function loadRelation(array $models, $name, Closure $constraints)
	{
		// First we will "back up" the existing where conditions on the query so we can
		// add our eager constraints. Then we will merge the wheres that were on the
		// query back to it in order that any where conditions might be specified.
		$relation = $this->getRelation($name);

		$relation->addEagerConstraints($models);

		call_user_func($constraints, $relation);

		$models = $relation->initRelation($models, $name);

		// Once we have the results, we just match those back up to their parent models
		// using the relationship instance. Then we just return the finished arrays
		// of models which have been eagerly hydrated and are readied for return.
		$results = $relation->getEager();

		return $relation->match($models, $results, $name);
	}

	/**
	 * Fill the model with an array of attributes.
	 *
	 * @param array $attributes
	 * @param bool $relations If the attributes also contain relations
	 * @return Model
	 */
	public function fill(array $attributes = [])
	{
		$this->raw = $attributes;

		$excludes = config("api.excludes");

		foreach ($attributes as $key => $attribute) {
			// Guarded attributes should be removed
			if (in_array($key, $excludes)) {
				unset($attributes[$key]);
			} else if (method_exists($this, $key) && ((is_array($attribute) || is_null($attribute)))) {
				// Its a relation
				$this->relationAttributes[$key] = $attribute;

				// For belongs to relation, while filling, we need to set relation key.
				$relation = call_user_func([$this, $key]);

				if ($relation instanceof BelongsTo) {
					$primaryKey = $relation->getRelated()->getKeyName();

					if ($attribute !== null) {
						// If key value is not set in request, we create new object
						if (!isset($attribute[$primaryKey])) {
							throw new RelatedResourceNotFoundException('Resource for relation "' . $key . '" not found');
						} else {
							$model = $relation->getRelated()->find($attribute[$primaryKey]);

							if (!$model) {
								// Resource not found
								throw new ResourceNotFoundException();
							}
						}
					}

					$relationKey = $relation->getForeignKeyName();

					$this->setAttribute($relationKey, ($attribute === null) ? null : $model->getKey());
				}

				unset($attributes[$key]);
			}
		}

		return parent::fill($attributes);
	}

	public function save(array $options = [])
	{
		// Belongs to relation needs to be set before, because we need the parent's Id
		foreach ($this->relationAttributes as $key => $relationAttribute) {
			/** @var Relation $relation */
			$relation = call_user_func([$this, $key]);

			if ($relation instanceof BelongsTo) {
				$primaryKey = $relation->getRelated()->getKeyName();

				if ($relationAttribute !== null) {
					// If key value is not set in request, we create new object
					if (!isset($relationAttribute[$primaryKey])) {
						throw new RelatedResourceNotFoundException('Resource for relation "' . $key . '" not found');
					} else {
						$model = $relation->getRelated()->find($relationAttribute[$primaryKey]);

						if (!$model) {
							// Resource not found
							throw new RelatedResourceNotFoundException('Resource for relation "' . $key . '" not found');
						}
					}
				}

				$relationKey = $relation->getForeignKeyName();

				$this->setAttribute($relationKey, ($relationAttribute === null) ? null : $model->getKey());

				unset($this->relationAttributes[$key]);
			}
		}

		parent::save($options);

		// Fill all other relations
		foreach ($this->relationAttributes as $key => $relationAttribute) {
			/** @var Relation $relation */
			$relation = call_user_func([$this, $key]);
			$primaryKey = $relation->getRelated()->getKeyName();

			if ($relation instanceof HasOne || $relation instanceof HasMany) {

				if ($relation instanceof HasOne) {
					$relationAttribute = [$relationAttribute];
				}

				$relationKey = explode(".", $relation->getQualifiedParentKeyName())[1];

				foreach ($relationAttribute as $val) {
					if ($val !== null) {
						if (!isset($val[$primaryKey])) {
							throw new RelatedResourceNotFoundException('Resource for relation "' . $key . '" not found');
						} else {
							/** @var Model $model */
							$model = $relation->getRelated()->find($val[$primaryKey]);

							if (!$model) {
								// Resource not found
								throw new RelatedResourceNotFoundException('Resource for relation "' . $key . '" not found');
							}

							// Only update relation key to attach $model to $this object
							$model->{$relationKey} = $this->getKey();
							$model->save();
						}
					}
				}
			} else if ($relation instanceof BelongsToMany) {
				$relatedIds = [];

				// Value is an array of related models
				foreach ($relationAttribute as $val) {
					if ($val !== null) {
						if (!isset($val[$primaryKey])) {
							throw new RelatedResourceNotFoundException('Resource for relation "' . $key . '" not found');
						} else {
							/** @var Model $model */
							$model = $relation->getRelated()->find($val[$primaryKey]);

							if (!$model) {
								// Resource not found
								throw new RelatedResourceNotFoundException('Resource for relation "' . $key . '" not found');
							}
						}
					}

					if ($val !== null) {
						if (isset($val['pivot'])) {
							// We have additional fields other than primary key
							// that need to be saved to pivot table
							/*
                                [
                                    {
                                        "id": 12, // Primary key
                                        "pivot": {
                                            "count": 8 // Pivot table column
                                        }
                                    }
                                ]
                             */
							$relatedIds[$model->getKey()] = $val['pivot'];
						} else {
							// We just have ids
							$relatedIds[] = $model->getKey();
						}
					}
				}

				$relation->sync($relatedIds);
			}
		}
	}
}