<?php
declare(strict_types=1);

namespace Esun\Homepage\Block;

use Mageplaza\Blog\Block\Post\View;
use Mageplaza\Blog\Model\Post;

/**
 * Provides chronological navigation for the current news post.
 */
class NewsPostNavigation extends View
{
    /** @var bool */
    private bool $navigationLoaded = false;

    /** @var Post|null */
    private ?Post $previousPost = null;

    /** @var Post|null */
    private ?Post $nextPost = null;

    /**
     * Get the news post immediately before the current post.
     *
     * @return Post|null
     */
    public function getPreviousPost(): ?Post
    {
        $this->loadNavigation();

        return $this->previousPost;
    }

    /**
     * Get the news post immediately after the current post.
     *
     * @return Post|null
     */
    public function getNextPost(): ?Post
    {
        $this->loadNavigation();

        return $this->nextPost;
    }

    /**
     * Get the active storefront ID.
     *
     * @return int
     */
    public function getCurrentStoreId(): int
    {
        return (int) $this->store->getStore()->getId();
    }

    /**
     * Resolve both navigation directions once per request.
     *
     * @return void
     */
    private function loadNavigation(): void
    {
        if ($this->navigationLoaded) {
            return;
        }

        $this->navigationLoaded = true;
        $currentPost = $this->getPost();
        $currentPostId = (int) $currentPost->getId();
        $publishDate = (string) $currentPost->getData('publish_date');

        if ($currentPostId <= 0 || $publishDate === '') {
            return;
        }

        $this->previousPost = $this->findPost([
            'publish_date' => ['eq' => $publishDate],
            'post_id' => ['lt' => $currentPostId],
        ], 'DESC');

        if ($this->previousPost === null) {
            $this->previousPost = $this->findPost([
                'publish_date' => ['lt' => $publishDate],
            ], 'DESC');
        }

        $this->nextPost = $this->findPost([
            'publish_date' => ['eq' => $publishDate],
            'post_id' => ['gt' => $currentPostId],
        ], 'ASC');

        if ($this->nextPost === null) {
            $this->nextPost = $this->findPost([
                'publish_date' => ['gt' => $publishDate],
            ], 'ASC');
        }
    }

    /**
     * Get the closest published post matching the supplied filters.
     *
     * @param array $filters
     * @param string $direction
     * @return Post|null
     */
    private function findPost(array $filters, string $direction): ?Post
    {
        $collection = $this->helperData->getPostList($this->getCurrentStoreId());

        foreach ($filters as $field => $condition) {
            $collection->addFieldToFilter($field, $condition);
        }

        $collection->setOrder('publish_date', $direction)
            ->setOrder('post_id', $direction)
            ->setPageSize(1)
            ->setCurPage(1);

        $post = $collection->getFirstItem();

        return $post instanceof Post && $post->getId() ? $post : null;
    }
}