<?php

namespace App\Yr\Forecast\Tabular;

use App\Yr\Forecast\Tabular\Time\DiffInterface;
use App\Yr\Forecast\Tabular\Variation\Variation;

/**
 * Removes superfluous forecast data in an Time-object
 * only storing changes.
 *
 * @author Joachim M. Giæver (joachim[]giaever.org)
 */
class Variations implements \IteratorAggregate {

    private $time;
    private $data = [];

    /**
     * @param array $t Array of Time-objects
     */
    public function __construct(array $t) {
        $time = array_shift($t);

        if (!$time instanceof Time)
            return;

        $this->time = $time;
        $var = new Variation($time);

        foreach($time as $entity)
            $var->addEntity($entity, null);

        $this->data[] = $var;

        foreach ($t as $time) {
            $var = new Variation($time);

            foreach($time as $entity)
                $this->match($var, $entity);

            if (!$var->isEmpty())
                $this->data[] = $var;

        }

        array_shift($this->data);
    }

    private function match(Variation $var, DiffInterface $entity): void {
        foreach(array_reverse($this->data) as $data) {
            foreach ($data as $dentity) {
                if ($entity instanceof $dentity) {
                    if ($entity->diff($dentity))
                        $var->addEntity($entity, $data == null ? "NULL" : $data);
                    return;
                }
            }
        }
    }

    public function getTime(): Time {
        return $this->time;
    }

    /**
     * Filter on types, example usage
     * ```
     * $variations->filter(function ($entity) {
     *      return $entity instanceof Temperature;
     * );
     * ```
     *
     * @return \Generator
     */
    public function filter(callable $filterFn): \Generator {
        foreach ($this as $data)
            if (($match = $data->filter($filterFn)) != null)
                yield $match;

        return null;
    }

    /**
     * {@inheritDoc}
     */
    public function getIterator(): \Generator {
        foreach ($this->data as $data)
            yield $data;
    }
}