<?php

namespace Kirby\Kql;

use Exception;
use Kirby\Cms\App;
use Kirby\Cms\Collection;
use Kirby\Toolkit\Str;

/**
 * ...
 *
 * @package   Kirby KQL
 * @author    Bastian Allgeier <bastian@getkirby.com>
 * @link      https://getkirby.com
 * @copyright Bastian Allgeier
 * @license   https://getkirby.com/license
 */
class Kql
{
	public static function fetch($model, $key, $selection)
	{
		// simple key/value
		if ($selection === true) {
			return static::render($model->$key());
		}

		// selection without additional query
		if (
			is_array($selection) === true &&
			empty($selection['query']) === true
		) {
			return static::select(
				$model->$key(),
				$selection['select'] ?? null,
				$selection['options'] ?? []
			);
		}

		// nested queries
		return static::run($selection, $model);
	}

	/**
	 * Returns helpful information about the object
	 * type as well as, if available, values and methods
	 */
	public static function help($object): array
	{
		return Help::for($object);
	}

	public static function query(string $query, $model = null)
	{
		$model ??= App::instance()->site();
		$data    = [$model::CLASS_ALIAS => $model];

		return Query::factory($query)->resolve($data);
	}

	public static function render($value)
	{
		if (is_object($value) === true) {
			// replace actual object with intercepting proxy class
			$object = Interceptor::replace($value);

			if (method_exists($object, 'toResponse') === true) {
				return $object->toResponse();
			}

			if (method_exists($object, 'toArray') === true) {
				return $object->toArray();
			}

			throw new Exception('The object "' . get_class($object) . '" cannot be rendered. Try querying one of its methods instead.');
		}

		return $value;
	}

	public static function run($input, $model = null)
	{
		// string queries
		if (is_string($input) === true) {
			$result = static::query($input, $model);
			return static::render($result);
		}

		// multiple queries
		if (isset($input['queries']) === true) {
			$result = [];

			foreach ($input['queries'] as $name => $query) {
				$result[$name] = static::run($query);
			}

			return $result;
		}

		$query   = $input['query']  ?? 'site';
		$select  = $input['select'] ?? null;
		$options = ['pagination' => $input['pagination'] ?? null];

		// check for invalid queries
		if (is_string($query) === false) {
			throw new Exception('The query must be a string');
		}

		$result = static::query($query, $model);
		return static::select($result, $select, $options);
	}

	public static function select(
		$data,
		array|string|null $select = null,
		array $options = []
	) {
		if ($select === null) {
			return static::render($data);
		}

		if ($select === '?') {
			return static::help($data);
		}

		if ($data instanceof Collection) {
			return static::selectFromCollection($data, $select, $options);
		}

		if (is_object($data) === true) {
			return static::selectFromObject($data, $select);
		}

		if (is_array($data) === true) {
			return static::selectFromArray($data, $select);
		}
	}

	/**
	 * @internal
	 */
	public static function selectFromArray(array $array, array $select): array
	{
		$result = [];

		foreach ($select as $key => $selection) {
			if ($selection === false) {
				continue;
			}

			if (is_int($key) === true) {
				$key       = $selection;
				$selection = true;
			}

			$result[$key] = $array[$key] ?? null;
		}

		return $result;
	}

	/**
	 * @internal
	 */
	public static function selectFromCollection(
		Collection $collection,
		array|string $select,
		array $options = []
	): array {
		if ($options['pagination'] ?? false) {
			$collection = $collection->paginate($options['pagination']);
		}

		$data = [];

		foreach ($collection as $model) {
			$data[] = static::selectFromObject($model, $select);
		}

		if ($pagination = $collection->pagination()) {
			return [
				'data' => $data,
				'pagination' => [
					'page'   => $pagination->page(),
					'pages'  => $pagination->pages(),
					'offset' => $pagination->offset(),
					'limit'  => $pagination->limit(),
					'total'  => $pagination->total(),
				],
			];
		}

		return $data;
	}

	/**
	 * @internal
	 */
	public static function selectFromObject(
		object $object,
		array|string $select
	): array {
		// replace actual object with intercepting proxy class
		$object = Interceptor::replace($object);
		$result = [];

		if (is_string($select) === true) {
			$select = Str::split($select);
		}

		foreach ($select as $key => $selection) {
			if ($selection === false) {
				continue;
			}

			if (is_int($key) === true) {
				$key       = $selection;
				$selection = true;
			}

			$result[$key] = static::fetch($object, $key, $selection);
		}

		return $result;
	}
}