feat: Add basic persistence layer + migration framework

.gitignore

@@ -1 +1,3 @@
-.idea
+.idea
+
+credentials.php

core.php

@@ -7,9 +7,12 @@ define("MAINTENANCE_MODE", require(ROOT . "/maintenance.php"));
 if (MAINTENANCE_MODE) {
     require(ROOT . "/templates/maintenance.php");
 } else {
+    $connection = require_once(ROOT . "/persistence/connection.php");
+    (require(ROOT . "/persistence/migrate.php"))($connection);
+
     $router = require(ROOT . "/router/Router.php");
-
     (require(ROOT . "/controllers/routes.php"))($router);
-
-    $router->execute();
+    $router->execute([
+        "DB_CONNECTION" => $connection,
+    ]);
 }

credentials.templ.php

@@ -0,0 +1,7 @@
+<?php
+
+// not constants so we can minimize their scope
+$DB_DSN = "{DB_DSN}";
+$DB_SCHEMA = "{DB_SCHEMA}";
+$DB_USERNAME = "{DB_USERNAME}";
+$DB_PASSWORD = "{DB_PASSWORD}";

persistence/connection.php

@@ -0,0 +1,7 @@
+<?php
+
+return (function() {
+    require(ROOT . "/credentials.php");
+
+    return new PDO($DB_DSN, $DB_USERNAME, $DB_PASSWORD);
+})();

persistence/migrate.php

@@ -0,0 +1,107 @@
+<?php
+
+function ensureDbStructureForMigrations(PDO $connection) {
+    require(ROOT . "/credentials.php");
+
+    if ($connection->query(<<<EOF
+            SELECT 
+                TABLE_NAME
+            FROM 
+            information_schema.TABLES 
+            WHERE 
+                TABLE_SCHEMA LIKE '${DB_SCHEMA}' AND 
+                TABLE_TYPE LIKE 'BASE TABLE' AND
+                TABLE_NAME = 'ua_migrations'
+        EOF)->rowCount() == 0
+    ) {
+        if ($connection->exec(<<<EOF
+                CREATE TABLE `ua_migrations` (
+                    `id` INTEGER PRIMARY KEY,
+                    `file` VARCHAR(255),
+                    `applied` DATETIME DEFAULT CURRENT_TIMESTAMP
+                );
+            EOF) === false
+        ) {
+            die("unable to bootstrap migrations: " . $connection->errorCode());
+        }
+    }
+}
+
+function getAllMigrations() {
+    $files = scandir(ROOT . "/persistence/migrations/");
+    $files = array_values(array_filter($files, fn($f) => $f[0] != "."));
+    sort($files);
+
+    $migrations = [];
+
+    foreach ($files as $file) {
+        $delimiterPos = strpos($file, "_");
+        $migrations[intval(substr($file, 0, $delimiterPos))] = $file;
+    }
+
+    return $migrations;
+}
+
+function getAppliedMigrations(PDO $connection) {
+    $result = $connection->query(<<<EOF
+        SELECT * FROM `ua_migrations`
+    EOF);
+
+    $migrations = [];
+    foreach ($result->fetchAll() as $row) {
+        $migrations[$row["id"]] = $row["file"];
+    }
+
+    return $migrations;
+}
+
+function getMigrationsToApply(PDO $connection) {
+    $all = getAllMigrations();
+    $applied = getAppliedMigrations($connection);
+
+    foreach ($applied as $id => $file) {
+        unset($all[$id]);
+    }
+
+    return $all;
+}
+
+function executeSqlScript(PDO $connection, string $sql, string $file) {
+    if ($connection->exec($sql) === false) {
+        die("failed to apply migration " . $file . ": " . $connection->errorCode());
+    }
+}
+
+function applyMigration(PDO $connection, int $id, string $file) {
+    $connection->beginTransaction();
+
+    $sql = file_get_contents(ROOT . "/persistence/migrations/" . $file);
+    if (!$sql) {
+        die("Unable to read migration file: " . $file);
+    }
+
+    executeSqlScript($connection, $sql, $file);
+
+    $statement = $connection->prepare(<<<EOF
+        INSERT INTO `ua_migrations`
+            (`id`, `file`) VALUES 
+            (?, ?)
+    EOF);
+    $statement->execute([$id, $file]);
+
+    try {
+        $connection->commit();
+    } catch (PDOException $e) {
+        // this might happen if the migration script contains a DDL statement
+        // -> ignore
+    }
+}
+
+return function(PDO $connection) {
+    ensureDbStructureForMigrations($connection);
+
+    $migrations = getMigrationsToApply($connection);
+    foreach ($migrations as $id => $file) {
+        applyMigration($connection, $id, $file);
+    }
+};