feat: add PDF generation and download feature

- Introduced dependency management with Composer for easier package handling.
- Added TCPDF library to generate PDFs of articles.
- Implemented PDF download functionality via a custom endpoint.
- Included admin notices to ensure Composer dependencies are installed.
- Updated single article view with a download button for PDFs.

.gitignore

@@ -0,0 +1,2 @@
+composer.phar
+vendor/

composer.json

@@ -0,0 +1,5 @@
+{
+    "require": {
+        "tecnickcom/tcpdf": "^6.7"
+    }
+}

composer.lock

@@ -0,0 +1,91 @@
+{
+    "_readme": [
+        "This file locks the dependencies of your project to a known state",
+        "Read more about it at https://getcomposer.org/doc/01-basic-usage.md#installing-dependencies",
+        "This file is @generated automatically"
+    ],
+    "content-hash": "a607f866b3f01ae9ad4f413456987bbb",
+    "packages": [
+        {
+            "name": "tecnickcom/tcpdf",
+            "version": "6.7.5",
+            "source": {
+                "type": "git",
+                "url": "https://github.com/tecnickcom/TCPDF.git",
+                "reference": "951eabf0338ec2522bd0d5d9c79b08a3a3d36b36"
+            },
+            "dist": {
+                "type": "zip",
+                "url": "https://api.github.com/repos/tecnickcom/TCPDF/zipball/951eabf0338ec2522bd0d5d9c79b08a3a3d36b36",
+                "reference": "951eabf0338ec2522bd0d5d9c79b08a3a3d36b36",
+                "shasum": ""
+            },
+            "require": {
+                "php": ">=5.5.0"
+            },
+            "type": "library",
+            "autoload": {
+                "classmap": [
+                    "config",
+                    "include",
+                    "tcpdf.php",
+                    "tcpdf_parser.php",
+                    "tcpdf_import.php",
+                    "tcpdf_barcodes_1d.php",
+                    "tcpdf_barcodes_2d.php",
+                    "include/tcpdf_colors.php",
+                    "include/tcpdf_filters.php",
+                    "include/tcpdf_font_data.php",
+                    "include/tcpdf_fonts.php",
+                    "include/tcpdf_images.php",
+                    "include/tcpdf_static.php",
+                    "include/barcodes/datamatrix.php",
+                    "include/barcodes/pdf417.php",
+                    "include/barcodes/qrcode.php"
+                ]
+            },
+            "notification-url": "https://packagist.org/downloads/",
+            "license": [
+                "LGPL-3.0-or-later"
+            ],
+            "authors": [
+                {
+                    "name": "Nicola Asuni",
+                    "email": "info@tecnick.com",
+                    "role": "lead"
+                }
+            ],
+            "description": "TCPDF is a PHP class for generating PDF documents and barcodes.",
+            "homepage": "http://www.tcpdf.org/",
+            "keywords": [
+                "PDFD32000-2008",
+                "TCPDF",
+                "barcodes",
+                "datamatrix",
+                "pdf",
+                "pdf417",
+                "qrcode"
+            ],
+            "support": {
+                "issues": "https://github.com/tecnickcom/TCPDF/issues",
+                "source": "https://github.com/tecnickcom/TCPDF/tree/6.7.5"
+            },
+            "funding": [
+                {
+                    "url": "https://www.paypal.com/cgi-bin/webscr?cmd=_donations&currency_code=GBP&business=paypal@tecnick.com&item_name=donation%20for%20tcpdf%20project",
+                    "type": "custom"
+                }
+            ],
+            "time": "2024-04-20T17:25:10+00:00"
+        }
+    ],
+    "packages-dev": [],
+    "aliases": [],
+    "minimum-stability": "stable",
+    "stability-flags": [],
+    "prefer-stable": false,
+    "prefer-lowest": false,
+    "platform": [],
+    "platform-dev": [],
+    "plugin-api-version": "2.6.0"
+}

functions.php

@@ -721,3 +721,105 @@ function custom_login_logo_url_title()
 }
 
 add_filter('login_headertext', 'custom_login_logo_url_title');
+
+// Check if TCPDF is available
+function is_tcpdf_available()
+{
+    return class_exists('TCPDF');
+}
+
+// Check if the Composer autoloader is available
+function is_autoloader_available()
+{
+    return file_exists(get_template_directory() . '/vendor/autoload.php');
+}
+
+// Display admin notice if TCPDF or autoloader is missing
+function tcpdf_missing_notice()
+{
+    if (!is_autoloader_available()) {
+        echo '<div class="notice notice-error"><p>';
+        _e('Composer autoloader is missing. Please run "composer install" to install the required dependencies.', 'duck-behavior-journal');
+        echo '</p></div>';
+    } elseif (!is_tcpdf_available()) {
+        echo '<div class="notice notice-error"><p>';
+        _e('TCPDF library is missing. Please install it via Composer to enable the PDF download feature.', 'duck-behavior-journal');
+        echo '</p></div>';
+    }
+}
+add_action('admin_notices', 'tcpdf_missing_notice');
+
+// Add custom endpoint for PDF download
+function add_pdf_download_endpoint()
+{
+    add_rewrite_rule('^download-pdf/([0-9]+)/?', 'index.php?download_pdf=$matches[1]', 'top');
+}
+add_action('init', 'add_pdf_download_endpoint');
+
+// Add query vars for PDF download
+function add_pdf_query_vars($vars)
+{
+    $vars[] = 'download_pdf';
+    return $vars;
+}
+add_filter('query_vars', 'add_pdf_query_vars');
+
+// Handle PDF download
+function handle_pdf_download()
+{
+    if (is_autoloader_available()) {
+        require_once get_template_directory() . '/vendor/autoload.php';
+    }
+
+    if (is_tcpdf_available()) {
+        $post_id = get_query_var('download_pdf');
+
+        if ($post_id && is_numeric($post_id)) {
+            $post = get_post($post_id);
+
+            if ($post && $post->post_type == 'article') {
+                // Create new PDF document
+                $pdf = new TCPDF(PDF_PAGE_ORIENTATION, PDF_UNIT, PDF_PAGE_FORMAT, true, 'UTF-8', false);
+
+                // Set document information
+                $pdf->SetCreator(PDF_CREATOR);
+                $pdf->SetAuthor(get_bloginfo('name'));
+                $pdf->SetTitle($post->post_title);
+                $pdf->SetSubject('Scientific Paper');
+
+                // Add a page
+                $pdf->AddPage();
+
+                // Set title
+                $pdf->SetFont('helvetica', 'B', 20);
+                $pdf->Cell(0, 10, $post->post_title, 0, 1, 'C');
+
+                // Set authors
+                $pdf->SetFont('helvetica', '', 12);
+                $authors = get_post_meta($post_id, 'article_authors', true);
+                if (!empty($authors)) {
+                    $pdf->Cell(0, 10, implode(', ', array_map('esc_html', $authors)), 0, 1, 'C');
+                }
+
+                // Set abstract
+                $pdf->Ln(10);
+                $pdf->SetFont('helvetica', 'B', 16);
+                $pdf->Cell(0, 10, 'Abstract', 0, 1);
+                $pdf->SetFont('helvetica', '', 12);
+                $pdf->MultiCell(0, 10, $post->post_excerpt);
+
+                // Set content
+                $pdf->Ln(10);
+                $pdf->SetFont('helvetica', 'B', 16);
+                $pdf->Cell(0, 10, 'Content', 0, 1);
+                $pdf->SetFont('helvetica', '', 12);
+                $pdf->writeHTML($post->post_content);
+
+                // Output PDF document
+                $pdf->Output(sanitize_title($post->post_title) . '.pdf', 'D');
+                exit;
+            }
+        }
+    }
+}
+add_action('template_redirect', 'handle_pdf_download');

single-article.php

@@ -24,15 +24,15 @@
                     </p>
                     <p class="text-muted">
                         <strong>Status:</strong> <?php
-                                                    $terms = get_the_terms(get_the_ID(), 'publication_status');
+                        $terms = get_the_terms(get_the_ID(), 'publication_status');
-                                                    if (!empty($terms) && !is_wp_error($terms)) {
+                        if (!empty($terms) && !is_wp_error($terms)) {
-                                                        $term_list = array();
+                            $term_list = array();
-                                                        foreach ($terms as $term) {
+                            foreach ($terms as $term) {
-                                                            $term_list[] = $term->name;
+                                $term_list[] = $term->name;
-                                                        }
+                            }
-                                                        echo implode(', ', $term_list);
+                            echo implode(', ', $term_list);
-                                                    }
+                        }
-                                                    ?>
+                        ?>
                     </p>
                     <?php if (has_excerpt()) : ?>
                         <p class="text-muted"><strong>Abstract:</strong> <?php echo get_the_excerpt(); ?></p>
@@ -49,6 +49,9 @@
                             <p class="text-muted"><strong>Note:</strong> <?php _e('The full paper is available for download for subscribers only.', 'duck-behavior-journal'); ?></p>
                     <?php endif;
                     endif; ?>
+                    <?php if (is_tcpdf_available()) : ?>
+                        <p><a href="<?php echo esc_url(home_url('/download-pdf/' . get_the_ID())); ?>" class="btn btn-primary"><?php _e('Download PDF', 'duck-behavior-journal'); ?></a></p>
+                    <?php endif; ?>
                     <hr>
                     <?php the_content(); ?>
             <?php endwhile;