further Davidson CI testing & AI refinement

create-critter.php

@@ -102,14 +102,6 @@ function secondsSinceLastCritterByAuthor(PDO $pdo, int $authorId): ?int
 
 $dailyLimitReached = countCrittersCreatedTodayByAuthor($pdo, (int) $_SESSION['user_id']) >= DAILY_CRITTER_LIMIT;
 
-$cooldownRemaining = 0;
-if ($_SERVER['REQUEST_METHOD'] === 'POST') {
-    $secondsSinceLast = secondsSinceLastCritterByAuthor($pdo, (int) $_SESSION['user_id']);
-    if ($secondsSinceLast !== null && $secondsSinceLast < CRITTER_COOLDOWN_SECONDS) {
-        $cooldownRemaining = CRITTER_COOLDOWN_SECONDS - $secondsSinceLast;
-    }
-}
-
 function isAllowedReplicateUrl(string $url): bool
 {
     $parts = parse_url($url);
@@ -192,33 +184,69 @@ if ($_SERVER['REQUEST_METHOD'] === 'POST' && $userCredits > 0 && !$dailyLimitRea
         }
     }
 
-    if (empty($errors) && countCrittersCreatedTodayByAuthor($pdo, (int) $_SESSION['user_id']) >= DAILY_CRITTER_LIMIT) {
-        $dailyLimitReached = true;
-    }
-
-    if (empty($errors) && $cooldownRemaining > 0) {
-        $errors['cooldown'] = "Please wait {$cooldownRemaining} more second(s) before creating another critter.";
-    }
-
     $creditReserved = false;
+    $critterId = null;
 
-    if (empty($errors) && !$dailyLimitReached) {
-        // Atomically reserve one credit in the same statement that checks for it, so
-        // concurrent requests can't all read "1 credit" before any of them writes the
-        // deduction. SQLite serializes writes, so only as many of these UPDATEs can
-        // match "credits > 0" as there are credits actually available; everyone else
-        // gets 0 rows affected and is turned away before the expensive Replicate call.
-        $reserveStmt = $pdo->prepare('UPDATE users SET credits = credits - 1 WHERE id = :id AND credits > 0');
-        $reserveStmt->execute(['id' => $_SESSION['user_id']]);
-        $creditReserved = $reserveStmt->rowCount() === 1;
+    if (empty($errors)) {
+        // Hold SQLite's single write lock across the daily-limit check, the
+        // cooldown check, the credit reservation, and the placeholder insert
+        // so concurrent requests can't all read the same stale count/cooldown
+        // before any of them commits. The row is inserted (image NULL) here,
+        // before the slow Replicate call, so it immediately counts toward the
+        // daily limit and cooldown for any other request racing in.
+        $pdo->exec('BEGIN IMMEDIATE');
+        try {
+            if (countCrittersCreatedTodayByAuthor($pdo, (int) $_SESSION['user_id']) >= DAILY_CRITTER_LIMIT) {
+                $dailyLimitReached = true;
+            }
 
-        if (!$creditReserved) {
-            $userCredits = 0;
-            $errors['credits'] = 'You do not have enough credits to create a critter.';
+            $cooldownRemaining = 0;
+            $secondsSinceLast = secondsSinceLastCritterByAuthor($pdo, (int) $_SESSION['user_id']);
+            if ($secondsSinceLast !== null && $secondsSinceLast < CRITTER_COOLDOWN_SECONDS) {
+                $cooldownRemaining = CRITTER_COOLDOWN_SECONDS - $secondsSinceLast;
+            }
+
+            if (!$dailyLimitReached && $cooldownRemaining > 0) {
+                $errors['cooldown'] = "Please wait {$cooldownRemaining} more second(s) before creating another critter.";
+            }
+
+            if (!$dailyLimitReached && empty($errors)) {
+                // Atomically reserve one credit in the same statement that checks for it, so
+                // concurrent requests can't all read "1 credit" before any of them writes the
+                // deduction. SQLite serializes writes, so only as many of these UPDATEs can
+                // match "credits > 0" as there are credits actually available; everyone else
+                // gets 0 rows affected and is turned away before the expensive Replicate call.
+                $reserveStmt = $pdo->prepare('UPDATE users SET credits = credits - 1 WHERE id = :id AND credits > 0');
+                $reserveStmt->execute(['id' => $_SESSION['user_id']]);
+                $creditReserved = $reserveStmt->rowCount() === 1;
+
+                if (!$creditReserved) {
+                    $userCredits = 0;
+                    $errors['credits'] = 'You do not have enough credits to create a critter.';
+                }
+            }
+
+            if ($creditReserved) {
+                $insertStmt = $pdo->prepare('INSERT INTO critters (noun_id, adjective_id, verb_id, location_id, author_id, image, datetime) VALUES (:noun_id, :adjective_id, :verb_id, :location_id, :author_id, NULL, :datetime)');
+                $insertStmt->execute([
+                    'noun_id' => $selected['noun_id'],
+                    'adjective_id' => $selected['adjective_id'],
+                    'verb_id' => $selected['verb_id'],
+                    'location_id' => $selected['location_id'],
+                    'author_id' => $_SESSION['user_id'],
+                    'datetime' => gmdate('Y-m-d H:i:s'),
+                ]);
+                $critterId = (int) $pdo->lastInsertId();
+            }
+
+            $pdo->exec('COMMIT');
+        } catch (Throwable $e) {
+            $pdo->exec('ROLLBACK');
+            throw $e;
         }
     }
 
-    if (empty($errors) && !$dailyLimitReached && $creditReserved) {
+    if ($creditReserved && $critterId !== null) {
         $adjectiveValue = getValueById($pdo, 'adjectives', $selected['adjective_id']);
         $nounValue = getValueById($pdo, 'nouns', $selected['noun_id']);
         $verbValue = getValueById($pdo, 'verbs', $selected['verb_id']);
@@ -307,32 +335,27 @@ if ($_SERVER['REQUEST_METHOD'] === 'POST' && $userCredits > 0 && !$dailyLimitRea
                         mkdir($imagesDir, 0755, true);
                     }
 
-                    $imageFilename = bin2hex(random_bytes(16)) . '.webp';
-                    file_put_contents($imagesDir . '/' . $imageFilename, $imageData);
+                    $candidateFilename = bin2hex(random_bytes(16)) . '.webp';
+                    $bytesWritten = file_put_contents($imagesDir . '/' . $candidateFilename, $imageData);
+                    if ($bytesWritten !== false) {
+                        $imageFilename = $candidateFilename;
+                    }
                 }
             }
         }
 
         if ($imageFilename === null) {
             // Every unsuccessful path above (request failure, failed/canceled prediction,
-            // disallowed or missing image URL, oversized or non-image download) leaves
-            // $imageFilename null, so this single check refunds the reserved credit for
-            // all of them instead of only the initial request-failure case.
+            // disallowed or missing image URL, oversized or non-image download, or a failed
+            // write to disk) leaves $imageFilename null, so this single check refunds the
+            // reserved credit for all of them instead of only the initial request-failure case.
             $refundStmt = $pdo->prepare('UPDATE users SET credits = credits + 1 WHERE id = :id');
             $refundStmt->execute(['id' => $_SESSION['user_id']]);
+        } else {
+            $updateStmt = $pdo->prepare('UPDATE critters SET image = :image WHERE id = :id');
+            $updateStmt->execute(['image' => $imageFilename, 'id' => $critterId]);
         }
 
-        $stmt = $pdo->prepare('INSERT INTO critters (noun_id, adjective_id, verb_id, location_id, author_id, image, datetime) VALUES (:noun_id, :adjective_id, :verb_id, :location_id, :author_id, :image, :datetime)');
-        $stmt->execute([
-            'noun_id' => $selected['noun_id'],
-            'adjective_id' => $selected['adjective_id'],
-            'verb_id' => $selected['verb_id'],
-            'location_id' => $selected['location_id'],
-            'author_id' => $_SESSION['user_id'],
-            'image' => $imageFilename,
-            'datetime' => gmdate('Y-m-d H:i:s'),
-        ]);
-
         header('Location: /');
         exit;
     }

db.php

@@ -11,6 +11,11 @@ function getDbConnection(): PDO
         $pdo->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
         $pdo->exec('PRAGMA foreign_keys = ON');
         $pdo->exec('PRAGMA busy_timeout = 5000');
+        // WAL lets readers proceed without blocking a writer's commit (and vice versa),
+        // which the default rollback-journal mode doesn't: two concurrent requests each
+        // holding open, unfetched-to-completion statement handles could otherwise make a
+        // writer's COMMIT fail with "database is locked" even within the busy_timeout.
+        $pdo->exec('PRAGMA journal_mode = WAL');
         $pdo->exec('CREATE TABLE IF NOT EXISTS users (
             id INTEGER PRIMARY KEY AUTOINCREMENT,
             username TEXT NOT NULL UNIQUE,

register.php

@@ -97,6 +97,11 @@ if ($_SERVER['REQUEST_METHOD'] === 'POST') {
                     'email' => $email,
                     'password' => $hashedPassword,
                 ]);
+                // Capture the new user's id before any other insert runs on this connection —
+                // SQLite's lastInsertId() returns the most recent rowid inserted on the
+                // connection regardless of table, so recordRegistrationAttempt()'s own insert
+                // would otherwise clobber it and log the session in as the wrong user.
+                $newUserId = (int) $pdo->lastInsertId();
                 recordRegistrationAttempt($pdo, $ipIdentifier);
             } catch (PDOException $e) {
                 if (str_contains($e->getMessage(), 'UNIQUE constraint failed: users.username')) {
@@ -109,8 +114,6 @@ if ($_SERVER['REQUEST_METHOD'] === 'POST') {
             }
 
             if (empty($errors)) {
-                $newUserId = (int) $pdo->lastInsertId();
-
                 start_app_session();
                 session_regenerate_id(true);
                 $_SESSION['user_id'] = $newUserId;