From 33f4d65bed30f193a383595ae54dbebe87ffb1e4 Mon Sep 17 00:00:00 2001
From: Kumi <git@kumi.email>
Date: Thu, 20 Jun 2024 14:44:20 +0200
Subject: [PATCH] feat: add DOI functionality to articles

Introduced DOI meta box with a generator button in the article editor to assign and display DOIs for articles. Added functionality to save DOI values and correspondingly set up rewrite rules and redirections based on DOI queries. Display DOI on the article single view page for enhanced article identification and accessibility.
---
 functions.php      | 76 ++++++++++++++++++++++++++++++++++++++++++++++
 single-article.php |  3 ++
 2 files changed, 79 insertions(+)

diff --git a/functions.php b/functions.php
index 515f941..b9cb8d5 100644
--- a/functions.php
+++ b/functions.php
@@ -257,6 +257,15 @@ function add_article_meta_boxes()
         'side',
         'default'
     );
+
+    add_meta_box(
+        'article_doi',
+        __('Article DOI', 'duck-behavior-journal'),
+        'render_article_doi_meta_box',
+        'article',
+        'side',
+        'default'
+    );
 }
 add_action('add_meta_boxes', 'add_article_meta_boxes');
 
@@ -299,6 +308,32 @@ function render_article_authors_meta_box($post)
 <?php
 }
 
+function render_article_doi_meta_box($post)
+{
+    $doi = get_post_meta($post->ID, 'article_doi', true);
+?>
+    <div id="article-doi">
+        <p>
+            <input type="text" name="article_doi" value="<?php echo esc_attr($doi); ?>" readonly />
+            <button type="button" id="generate-doi-button" class="button"><?php _e('Generate DOI', 'duck-behavior-journal'); ?></button>
+        </p>
+    </div>
+    <script>
+        function generateRandomDOI(prefix) {
+            const randomString = Math.random().toString(36).substring(2, 10);
+            return prefix + randomString;
+        }
+
+        jQuery(document).ready(function($) {
+            $('#generate-doi-button').on('click', function() {
+                const doi = generateRandomDOI('22.2222/DBJ/');
+                $('input[name="article_doi"]').val(doi);
+            });
+        });
+    </script>
+<?php
+}
+
 function save_article_authors_meta_box($post_id)
 {
     if (defined('DOING_AUTOSAVE') && DOING_AUTOSAVE) return;
@@ -307,4 +342,45 @@ function save_article_authors_meta_box($post_id)
     $authors = array_map('sanitize_text_field', $_POST['article_authors']);
     update_post_meta($post_id, 'article_authors', $authors);
 }
+
 add_action('save_post', 'save_article_authors_meta_box');
+
+function add_doi_rewrite_rule()
+{
+    add_rewrite_rule('^([0-9]{2})\.([0-9]{4})/([a-zA-Z0-9_\-\/]+)?$', 'index.php?doi=$matches[1].$matches[2]/$matches[3]', 'top');
+}
+
+add_action('init', 'add_doi_rewrite_rule');
+
+function add_doi_query_var($vars)
+{
+    $vars[] = 'doi';
+    return $vars;
+}
+
+add_filter('query_vars', 'add_doi_query_var');
+
+function redirect_doi_to_article($query)
+{
+    if (isset($query->query_vars['doi'])) {
+        $doi = $query->query_vars['doi'];
+        $args = array(
+            'post_type' => 'article',
+            'meta_query' => array(
+                array(
+                    'key' => 'article_doi',
+                    'value' => $doi,
+                    'compare' => '='
+                )
+            )
+        );
+        $articles = new WP_Query($args);
+        if ($articles->have_posts()) {
+            $articles->the_post();
+            wp_redirect(get_permalink(), 301);
+            exit;
+        }
+    }
+}
+
+add_action('parse_query', 'redirect_doi_to_article');
diff --git a/single-article.php b/single-article.php
index 2e9d6d8..0c8e918 100644
--- a/single-article.php
+++ b/single-article.php
@@ -15,6 +15,9 @@
                             the_author();
                         }
                         ?>
+                    <p class="text-muted">
+                        <strong>DOI:</strong> <?php echo esc_html(get_post_meta(get_the_ID(), 'article_doi', true)); ?>
+                    </p>
                     <p class="text-muted">
                         <?php
                         $terms = get_the_terms(get_the_ID(), 'publication_status');