From 7f944af41f3214014becde824608bf3d03d07e15 Mon Sep 17 00:00:00 2001
From: Johannes Meyer <johannes.meyer@icinga.com>
Date: Tue, 17 Dec 2024 10:41:11 +0100
Subject: [PATCH] Introduce singleton `Icinga\Module\Icingadb\Common\Backend`

---
 library/Icingadb/Common/Backend.php | 168 ++++++++++++++++++++++++++++
 1 file changed, 168 insertions(+)
 create mode 100644 library/Icingadb/Common/Backend.php

diff --git a/library/Icingadb/Common/Backend.php b/library/Icingadb/Common/Backend.php
new file mode 100644
index 000000000..135732dfb
--- /dev/null
+++ b/library/Icingadb/Common/Backend.php
@@ -0,0 +1,168 @@
+<?php
+
+/* Icinga DB Web | (c) 2024 Icinga GmbH | GPLv2 */
+
+namespace Icinga\Module\Icingadb\Common;
+
+use Icinga\Application\Config as AppConfig;
+use Icinga\Data\ResourceFactory;
+use Icinga\Module\Icingadb\Model\Schema;
+use ipl\Sql\Adapter\Pgsql;
+use ipl\Sql\Config as SqlConfig;
+use ipl\Sql\Connection;
+use ipl\Sql\Expression;
+use ipl\Sql\QueryBuilder;
+use ipl\Sql\Select;
+use PDO;
+
+/**
+ * Singleton providing access to the Icinga DB and Redis
+ */
+final class Backend
+{
+    /** @var ?Connection */
+    private static $db;
+
+    /** @var ?int */
+    private static $schemaVersion;
+
+    /** @var ?IcingaRedis */
+    private static $redis;
+
+    /**
+     * Set the connection to the Icinga DB
+     *
+     * Usually not required, as the connection is created on demand. Useful for testing.
+     *
+     * @param Connection $db
+     *
+     * @return void
+     */
+    public static function setDb(Connection $db): void
+    {
+        self::$db = $db;
+    }
+
+    /**
+     * Get the connection to the Icinga DB
+     *
+     * @return Connection
+     */
+    public static function getDb(): Connection
+    {
+        if (self::$db === null) {
+            $config = new SqlConfig(ResourceFactory::getResourceConfig(
+                AppConfig::module('icingadb')->get('icingadb', 'resource')
+            ));
+
+            $config->options = [PDO::ATTR_DEFAULT_FETCH_MODE => PDO::FETCH_OBJ];
+            if ($config->db === 'mysql') {
+                $config->options[PDO::MYSQL_ATTR_INIT_COMMAND] = "SET SESSION SQL_MODE='STRICT_TRANS_TABLES"
+                    . ",NO_ZERO_IN_DATE,NO_ZERO_DATE,ERROR_FOR_DIVISION_BY_ZERO,NO_ENGINE_SUBSTITUTION'";
+            }
+
+            self::$db = new Connection($config);
+
+            $adapter = self::$db->getAdapter();
+            if ($adapter instanceof Pgsql) {
+                $quoted = $adapter->quoteIdentifier('user');
+                self::$db->getQueryBuilder()
+                    ->on(QueryBuilder::ON_SELECT_ASSEMBLED, function (&$sql) use ($quoted) {
+                        // user is a reserved key word in PostgreSQL, so we need to quote it.
+                        // TODO(lippserd): This is pretty hacky,
+                        // reconsider how to properly implement identifier quoting.
+                        $sql = str_replace(' user ', sprintf(' %s ', $quoted), $sql);
+                        $sql = str_replace(' user.', sprintf(' %s.', $quoted), $sql);
+                        $sql = str_replace('(user.', sprintf('(%s.', $quoted), $sql);
+                    })
+                    ->on(QueryBuilder::ON_ASSEMBLE_SELECT, function (Select $select) {
+                        // For SELECT DISTINCT, all ORDER BY columns must appear in SELECT list.
+                        if (! $select->getDistinct() || ! $select->hasOrderBy()) {
+                            return;
+                        }
+
+                        $candidates = [];
+                        foreach ($select->getOrderBy() as list($columnOrAlias, $_)) {
+                            if ($columnOrAlias instanceof Expression) {
+                                // Expressions can be and include anything,
+                                // also columns that aren't already part of the SELECT list,
+                                // so we're not trying to guess anything here.
+                                // Such expressions must be in the SELECT list if necessary and
+                                // referenced manually with an alias in ORDER BY.
+                                continue;
+                            }
+
+                            $candidates[$columnOrAlias] = true;
+                        }
+
+                        foreach ($select->getColumns() as $alias => $column) {
+                            if (is_int($alias)) {
+                                if ($column instanceof Expression) {
+                                    // This is the complement to the above consideration.
+                                    // If it is an unaliased expression, ignore it.
+                                    continue;
+                                }
+                            } else {
+                                unset($candidates[$alias]);
+                            }
+
+                            if (! $column instanceof Expression) {
+                                unset($candidates[$column]);
+                            }
+                        }
+
+                        if (! empty($candidates)) {
+                            $select->columns(array_keys($candidates));
+                        }
+                    });
+            }
+        }
+
+        return self::$db;
+    }
+
+    /**
+     * Get the schema version of the Icinga DB
+     *
+     * @return int
+     */
+    public static function getDbSchemaVersion(): int
+    {
+        if (self::$schemaVersion === null) {
+            self::$schemaVersion = Schema::on(self::getDb())
+                ->columns('version')
+                ->first()
+                ->version;
+        }
+
+        return self::$schemaVersion;
+    }
+
+    /**
+     * Set the connection to the Icinga Redis
+     *
+     * Usually not required, as the connection is created on demand. Useful for testing.
+     *
+     * @param IcingaRedis $redis
+     *
+     * @return void
+     */
+    public static function setRedis(IcingaRedis $redis): void
+    {
+        self::$redis = $redis;
+    }
+
+    /**
+     * Get the connection to the Icinga Redis
+     *
+     * @return IcingaRedis
+     */
+    public static function getRedis(): IcingaRedis
+    {
+        if (self::$redis === null) {
+            self::$redis = new IcingaRedis();
+        }
+
+        return self::$redis;
+    }
+}