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<?php

    namespace Inteve\FeedGenerator\Feeds\GoogleMerchant;

    use Inteve\FeedGenerator\Feed;
    use Inteve\FeedGenerator\InvalidItemException;
    use Inteve\FeedGenerator\IOutput;
    use Inteve\FeedGenerator\Utils\Helpers;


    class GoogleMerchantFeed extends Feed
    {
        /** @var string|NULL */
        private $title;

        /** @var string|NULL */
        private $websiteUrl;

        /** @var \DateTimeInterface|NULL */
        private $updated;

        /** @var string|NULL */
        private $author;


        /**
         * @return string|NULL
         */
        public function getTitle()
        {
            return $this->title;
        }


        /**
         * @param  string
         * @return self
         */
        public function setTitle($title)
        {
            $this->title = $title;
            return $this;
        }


        /**
         * @return string|NULL
         */
        public function getWebsiteUrl()
        {
            return $this->websiteUrl;
        }


        /**
         * @param  string
         * @return self
         */
        public function setWebsiteUrl($websiteUrl)
        {
            $this->websiteUrl = $websiteUrl;
            return $this;
        }


        /**
         * @return \DateTimeInterface|NULL
         */
        public function getUpdated()
        {
            return $this->updated;
        }


        /**
         * @param  \DateTimeInterface
         * @return self
         */
        public function setUpdated(\DateTimeInterface $updated)
        {
            $this->updated = $updated;
            return $this;
        }


        /**
         * @return string|NULL
         */
        public function getAuthor()
        {
            return $this->author;
        }


        /**
         * @param  string
         * @return self
         */
        public function setAuthor($author)
        {
            $this->author = $author;
            return $this;
        }


        /**
         * @return string
         */
        public function getContentType()
        {
            return 'application/atom+xml';
        }


        /**
         * @return void
         * @throws InvalidItemException
         */
        public function generate(IOutput $output)
        {
            // https://support.google.com/merchants/answer/160593
            $this->validate();
            $output->open();
            $output->output('<?xml version="1.0" encoding="utf-8"?>');
            $output->output("\n");
            $output->output('<feed xmlns="http://www.w3.org/2005/Atom" xmlns:g="http://base.google.com/ns/1.0">');
            $output->output("\n");

            $feedUpdated = $this->getUpdated();

            Helpers::writeXml($output, array(
                'title' => $this->getTitle(),
                'link' => array(
                    'attrs' => array(
                        'href' => $this->getWebsiteUrl(),
                        'rel' => 'alternate',
                        'type' => 'text/html',
                    ),
                ),
                'updated' => $feedUpdated ? $feedUpdated->format(\DateTime::ATOM) : NULL,
                'author' => array(
                    'content' => array(
                        'name' => $this->getAuthor(),
                    ),
                ),
            ));

            foreach ($this->items as $item) {
                // https://support.google.com/merchants/answer/7052112

                if (!($item instanceof GoogleMerchantItem)) {
                    throw new InvalidItemException('Feed item must be instance of GoogleMerchantItem.');
                }

                $item->validate();

                $output->output("<entry>\n");

                Helpers::writeXml($output, array(
                    'g:id' => $item->getId(),
                    'g:title' => $item->getTitle(),
                    'g:description' => $item->getDescription(),
                    'g:link' => $item->getUrl(),
                    'g:image_link' => $item->getImageUrl(),

                    // price & availability
                    'g:availability' => $item->getAvailability(),
                    'g:price' => $item->getPrice(),

                    // features
                    'g:condition' => $item->getCondition(),
                    'g:adult' => $item->isAdult() ? 'yes' : 'no',
                    'g:color' => $item->getColor(),
                    'g:gender' => $item->getGender(),
                    'g:size' => $item->getSize(),

                    // group ID
                    'g:item_group_id' => $item->getGroupId(),

                    // shipping
                    'g:shipping' => $item->getShipping(),
                    'g:shipping_label' => $item->getShippingLabel(),

                    // identifiers
                    'g:identifier_exists' => !$item->hasIdentifiers() ? 'no' : NULL,
                ));

                $output->output("</entry>\n");
            }

            $output->output('</feed>');
            $output->output("\n");
            $output->close();
        }


        /**
         * @return void
         * @throws AssertException
         */
        protected function validate()
        {
            Helpers::assert(isset($this->title), 'Missing title, call $feed->setTitle().');
            Helpers::assert(isset($this->websiteUrl), 'Missing website URL, call $feed->setWebsiteUrl().');
            Helpers::assert(isset($this->updated), 'Missing update date, call $feed->setUpdated().');
            Helpers::assert(isset($this->author), 'Missing author, call $feed->setAuthor().');
        }
    }