daos/mysql: Add colors to tags without one

When user specified a source tag with a same name but a different letter casing as another existing tag,
the MySQL backend would think the tag already exists and not create a color for it.
This would break, for example, OPML export, which expects every tag to have a color associated with it.

The bug has been fixed in the previous commit but there can still be such erroneously created tags from before.
Let’s go through all tags mentioned in the `source` table and ensure the `tags` table is up to date.
If a tag with a different casing and a color exists, let’s consider it the canonical casing and update the source tag to that.

Fixes: #1438

src/daos/mysql/Database.php

@@ -6,6 +6,7 @@
 
 use daos\CommonSqlDatabase;
 use helpers\DatabaseConnection;
+use helpers\StringKeyedArray;
 use Monolog\Logger;
 
 /**
@@ -292,6 +293,77 @@ public function __construct(DatabaseConnection $connection, Logger $logger) {
             $this->exec('INSERT INTO ' . $this->connection->getTableNamePrefix() . 'version (version) VALUES (14)');
             $this->commit();
         }
+        if ($version < 15) {
+            $this->logger->debug('Upgrading database schema to version 15 by ensuring all tags have colors');
+
+            $this->beginTransaction();
+
+            /** @var StringKeyedArray<bool> */
+            $coloredTags = new StringKeyedArray();
+            /** @var StringKeyedArray<string> */
+            $coloredTagsNormalised = new StringKeyedArray();
+            /** @var StringKeyedArray<string> */
+            $tagsWithoutColor = new StringKeyedArray();
+
+            $tags = $this->exec('SELECT tag, LOWER(tag) as normal FROM ' . $this->connection->getTableNamePrefix() . 'tags');
+            foreach ($tags as $tag) {
+                $coloredTags[$tag['tag']] = true;
+                $coloredTagsNormalised[$tag['normal']] = $tag['tag'];
+            }
+
+            $sources = $this->exec('SELECT id, tags, LOWER(tags) as normal FROM ' . $this->connection->getTableNamePrefix() . 'sources');
+            foreach ($sources as $source) {
+                if ($source['tags'] === '') {
+                    continue;
+                }
+
+                $shouldUpdateSourceTags = false;
+
+                $sourceTags = explode(',', $source['tags']);
+                $sourceTagPairs = array_map(
+                    null,
+                    $sourceTags,
+                    explode(',', $source['normal'])
+                );
+                foreach ($sourceTagPairs as $key => [$tag, $normal]) {
+                    // If the tag does not have associated color:
+                    if (!isset($coloredTags[$tag])) {
+                        // Try to match it to a differently-cased tag.
+                        if (isset($coloredTagsNormalised[$normal])) {
+                            $sourceTags[$key] = $coloredTagsNormalised[$normal];
+                            $shouldUpdateSourceTags = true;
+                        } else {
+                            // Otherwise mark it for assigning a color.
+                            $tagsWithoutColor[$normal] = $tag;
+                        }
+                    }
+                }
+
+                if ($shouldUpdateSourceTags) {
+                    $this->exec(
+                        'UPDATE ' . $this->connection->getTableNamePrefix() . 'sources SET tags = :tags WHERE id = :id',
+                        [
+                            'id' => $source['id'],
+                            'tags' => implode(',', $sourceTags),
+                        ]
+                    );
+                }
+            }
+
+            // Add color to all tags without one.
+            foreach ($tagsWithoutColor as $tag) {
+                $this->exec(
+                    'INSERT INTO ' . $this->connection->getTableNamePrefix() . 'tags(tag, color) VALUES (:tag, :color)',
+                    [
+                        'tag' => $tag,
+                        'color' => '#df1818',
+                    ]
+                );
+            }
+
+            $this->exec('INSERT INTO ' . $this->connection->getTableNamePrefix() . 'version (version) VALUES (15)');
+            $this->commit();
+        }
     }
 
     /**