Add rate limiting functionality

Introduces a new 'rate_limit' table to track request counts by IP and email. Adds `RateLimitQuery` class for querying and inserting rate limits, and `RateLimitEntryDTO` for passing rate limit data.

src/main/java/com/alttd/forms/database/Database.java

@@ -12,8 +12,35 @@ public class Database {
 
     public static void createTables() {
         String[] createTables = {
-                "CREATE TABLE IF NOT EXISTS verify_form (e_mail VARCHAR(256), verification_code INT, formId INT, PRIMARY KEY(e_mail, verification_code))",
+                // language=SQL
-                "CREATE TABLE IF NOT EXISTS form (formId INT AUTO_INCREMENT, creation_date BIGINT, form_json TEXT, form_class VARCHAR(64), PRIMARY KEY(formId))"
+                """
+                CREATE TABLE IF NOT EXISTS verify_form(
+                    e_mail VARCHAR(256),
+                    verification_code INT,
+                    formId INT,
+                    PRIMARY KEY(e_mail, verification_code)
+                )
+                """,
+                // language=SQL
+                """
+                CREATE TABLE IF NOT EXISTS form(
+                    formId INT AUTO_INCREMENT,
+                    creation_date BIGINT,
+                    form_json TEXT,
+                    form_class VARCHAR(64),
+                    PRIMARY KEY(formId)
+                )
+                """,
+                // language=SQL
+                """
+                CREATE TABLE IF NOT EXISTS rate_limit(
+                    id INT AUTO_INCREMENT,
+                    time TIMESTAMP,
+                    ip VARCHAR(45),
+                    mail VARCHAR(256),
+                    PRIMARY KEY(id)
+                )
+                """
         };
         Connection connection = DatabaseConnection.getConnection();
         for (String query : createTables) {

src/main/java/com/alttd/forms/mail/rate_limitter/RateLimitEntryDTO.java

@@ -0,0 +1,6 @@
+package com.alttd.forms.mail.rate_limitter;
+
+import java.time.Instant;
+
+public record RateLimitEntryDTO(Instant time, String ip, String mail) {
+}

src/main/java/com/alttd/forms/mail/rate_limitter/RateLimitQuery.java

@@ -0,0 +1,59 @@
+package com.alttd.forms.mail.rate_limitter;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.sql.*;
+import java.time.Instant;
+
+public class RateLimitQuery {
+
+    private static final Logger logger = LoggerFactory.getLogger(RateLimitQuery.class);
+
+    public int getIpHits(Connection connection, String ip, Instant after) throws SQLException {
+        String sql = "SELECT COUNT(*) AS hits FROM rate_limit WHERE ip = ? AND time > ?";
+        try (PreparedStatement stmt = connection.prepareStatement(sql)) {
+            stmt.setString(1, ip);
+            stmt.setTimestamp(2, Timestamp.from(after));
+            ResultSet resultSet = stmt.executeQuery();
+            if (!resultSet.next()) {
+                return 0;
+            }
+            return resultSet.getInt("hits");
+        } catch (SQLException e) {
+            logger.error("Failed get ip hits query for ip: {}", ip, e);
+            throw e;
+        }
+    }
+
+    public int getMailHits(Connection connection, String mail, Instant after) throws SQLException {
+        String sql = "SELECT COUNT(*) AS hits FROM rate_limit WHERE mail = ? AND time > ?";
+        try (PreparedStatement stmt = connection.prepareStatement(sql)) {
+            stmt.setString(1, mail);
+            stmt.setTimestamp(2, Timestamp.from(after));
+            ResultSet resultSet = stmt.executeQuery();
+            if (!resultSet.next()) {
+                return 0;
+            }
+            return resultSet.getInt("hits");
+        } catch (SQLException e) {
+            logger.error("Failed get mail hits query for ip: {}", mail, e);
+            throw e;
+        }
+    }
+
+    public boolean insertRateLimitEntry(Connection connection, RateLimitEntryDTO entry) throws SQLException {
+        String sql = "INSERT INTO rate_limit (time, ip, mail) VALUES (?, ?, ?)";
+        try {
+            PreparedStatement stmt = connection.prepareStatement(sql);
+            stmt.setTimestamp(1, Timestamp.from(entry.time()));
+            stmt.setString(2, entry.ip());
+            stmt.setString(3, entry.mail());
+            return stmt.executeUpdate() > 0;
+        } catch (SQLException e) {
+            logger.error("Failed to store rate limit for ip: {}, mail: {}, time: {}", entry.ip(), entry.mail(), entry.time(), e);
+            throw e;
+        }
+    }
+
+}