Add Crossref citations badge (#3)

* Add Crossref citations badge

* Fix whitespace in admin form

* Fixing Diego's suggestions

* Add error handling to drupal_http_request

* Force plaintext in block_text variable

* Add translatable alt text to badge image

modules/islandora_crossref_citations/README.md

@@ -0,0 +1,48 @@
+# Islandora Crossref Citations
+
+## Introduction
+
+Islandora Crossref Citations generates a block which displays citation counts for any object with a DOI, via the Crossref Cited-by service, for use with Islandora Badges.
+
+The badge will only display on objects with a MODS datastream and a DOI (Digital Object Identifier).
+
+## Requirements
+
+This module requires the following modules/libraries:
+
+* [Islandora](https://github.com/islandora/islandora)
+* [Islandora Badges](https://github.com/Islandora/islandora_badges)
+
+## Installation
+
+Install as usual, see [this](https://drupal.org/documentation/install/modules-themes/modules-7) for further information.
+
+## Configuration
+
+Configuration path is admin/islandora/tools/badges/crossref (Administration > Islandora > Islandora Utility Modules > Islandora Badges Configuration > Crossref citations).
+
+Block text: Defines the text used in the citation count block. Defaults to "Citations via Crossref".
+
+Badge type: You can choose between plain text or an automatically-generated image from shields.io. Plain text is offered for custom styling.
+
+
+## Troubleshooting/Issues
+
+Having problems or solved a problem? Check out the Islandora google groups for a solution.
+
+* [Islandora Group](https://groups.google.com/forum/?hl=en&fromgroups#!forum/islandora)
+* [Islandora Dev Group](https://groups.google.com/forum/?hl=en&fromgroups#!forum/islandora-dev)
+
+## Maintainers/Sponsors
+
+Current maintainers:
+
+* [Brandon Weigel](https://github.com/bondjimbond)
+
+## Development
+
+If you would like to contribute to this module, please check out [CONTRIBUTING.md](CONTRIBUTING.md). In addition, we have helpful [Documentation for Developers](https://github.com/Islandora/islandora/wiki#wiki-documentation-for-developers) info, as well as our [Developers](http://islandora.ca/developers) section on the [Islandora.ca](http://islandora.ca) site.
+
+## License
+
+[GPLv3](http://www.gnu.org/licenses/gpl-3.0.txt)

modules/islandora_crossref_citations/includes/admin.form.inc

@@ -0,0 +1,27 @@
+<?php
+/**
+ * @file
+ * Crossref Citations badge admin options
+ */
+
+/**
+ * Admin form: Nothing here yet.
+ */
+function islandora_crossref_citations_admin_form($form, $form_settings) {
+  $form['islandora_crossref_citations_text'] = array(
+    '#type' => 'textfield',
+    '#title' => t('Link text'),
+    '#description' => t('Text to use when generating external download link.'),
+    '#default_value' => variable_get('islandora_crossref_citations_text', 'Citations via Crossref'),
+  );
+
+  $form['islandora_crossref_citations_badgetype'] = array(
+    '#type' => 'radios',
+    '#title' => t('Type of badge'),
+    '#description' => t('You may choose an image generated by shields.io, or a text block you can style yourself with CSS.'),
+    '#options' => array('image' => t('image'), 'text' => t('text')),
+    '#default_value' => variable_get('islandora_crossref_citations_badgetype', 'image'),
+  );
+
+  return system_settings_form($form);
+}

modules/islandora_crossref_citations/islandora_crossref_citations.info

@@ -0,0 +1,5 @@
+name = Islandora Crossref Citations
+core = 7.x
+description = Islandora Crossref citation counts.
+dependencies[] = islandora_badges
+package = Islandora Tools

modules/islandora_crossref_citations/islandora_crossref_citations.install

@@ -0,0 +1,16 @@
+<?php
+/**
+ * @file
+ * Installation hooks for Crossref Citations badges.
+ */
+
+/**
+ * Implements hook_uninstall().
+ */
+function islandora_crossref_citations_uninstall() {
+  $vars = array(
+    islandora_crossref_citations_text,
+    islandora_crossref_citations_badgetype,
+  );
+  array_walk($vars, 'variable_del');
+}

modules/islandora_crossref_citations/islandora_crossref_citations.module

@@ -0,0 +1,82 @@
+<?php
+/**
+ * @file
+ * Crossref Citation Badges
+ */
+
+/**
+ * Implements hook_menu().
+ */
+function islandora_crossref_citations_menu() {
+  return array(
+    'admin/islandora/tools/badges/crossref' => array(
+      'title' => 'Crossref citations',
+      'description' => 'Configure Crossref Citations settings.',
+      'page callback' => 'drupal_get_form',
+      'page arguments' => array('islandora_crossref_citations_admin_form'),
+      'access arguments' => array('administer site configuration'),
+      'type' => MENU_LOCAL_TASK,
+      'file' => 'includes/admin.form.inc',
+    ),
+  );
+}
+
+/**
+ * Implements hook_block_info().
+ */
+function islandora_crossref_citations_block_info() {
+  return array(
+    'islandora_crossref_badge' => array(
+      'visibility' => BLOCK_VISIBILITY_LISTED,
+      'pages' => 'islandora/object/*',
+      'cache' => DRUPAL_CACHE_PER_PAGE,
+      'info' => t('Crossref citations badge'),
+    ),
+  );
+}
+
+/**
+ * Implements hook_block_view().
+ */
+function islandora_crossref_citations_block_view($delta = '') {
+  module_load_include('inc', 'islandora_badges', 'includes/utilities');
+  $to_render = array();
+  if ($delta == 'islandora_crossref_badge') {
+    $object = menu_get_object('islandora_object', 2);
+    if ($object) {
+      // Check CModel against Badges configuration.
+      if (islandora_badges_show_for_cmodel($object)) {
+          $doi = islandora_badges_get_doi($object);
+          if ($doi) {
+            // Set API endpoint URL
+            // @TODO: Add to admin form.
+            $url = "https://api.crossref.org/works/";
+            $request_url = $url . $doi;
+            // Make the request and get results!
+            $result_json = drupal_http_request($request_url);
+            if (!isset($result_json->error)) {
+              $result_array = json_decode($result_json->data, TRUE);
+              $result_citation_count = $result_array['message']['is-referenced-by-count'];
+            }
+        }
+      }
+    }
+  }
+
+  if (isset($result_citation_count) && ($result_citation_count > 0)) {
+    // Sanitize block text input.
+    $block_text = check_plain(variable_get('islandora_crossref_citations_text', 'Citations via Crossref'));
+    $badge_type = variable_get('islandora_crossref_citations_badgetype', 'image');
+    if ($badge_type == 'text') {
+      $badge = $block_text . ': ' . $result_citation_count;
+    }
+    else {
+      $badge = '<img src="https://img.shields.io/badge/' . $block_text . '-' . $result_citation_count . '-blue.svg?style=flat" alt="' . t('Number of citations via Crossref: ' . $result_citation_count) . '">';
+    }
+  $to_render['content'] = $badge;
+
+  }
+
+  return $to_render;
+
+}