feat: add basic configuration management

src/main/java/dev/lilyvex/oauthfabric/OAuthFabricConfig.java

@@ -0,0 +1,102 @@
+package dev.lilyvex.oauthfabric;
+
+import com.electronwill.nightconfig.core.CommentedConfig;
+import com.electronwill.nightconfig.core.io.ParsingException;
+import com.electronwill.nightconfig.core.io.ParsingMode;
+import com.electronwill.nightconfig.toml.TomlParser;
+import com.electronwill.nightconfig.toml.TomlWriter;
+
+import net.fabricmc.loader.api.FabricLoader;
+
+import java.io.FileNotFoundException;
+import java.io.IOException;
+import java.nio.charset.StandardCharsets;
+import java.nio.file.Files;
+import java.nio.file.NoSuchFileException;
+import java.nio.file.Path;
+import java.nio.file.StandardCopyOption;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+public class OAuthFabricConfig {
+    private static final Logger LOGGER = LoggerFactory.getLogger("oauth-fabric");
+    private static final String DEFAULT_PROVIDER = "auth.lilyvex.dev";
+    private static final String DEFAULT_CLIENT_ID = "minecraft";
+    private static final String DEFAULT_CLIENT_SECRET = "<No default secret>";
+    private static final String DEFAULT_REDIRECT_URI = "mc.lilyvex.dev/oauth2";
+    private static final String DEFAULT_DATABASE = "sqlite";
+    
+    public static final Path CONFIG_FILE_PATH = FabricLoader.getInstance().getConfigDir()
+        .resolve("oauth-fabric.toml")
+        .normalize();
+
+    private final CommentedConfig config = CommentedConfig.inMemory();
+
+    // URL to the OAuth provider (e.g. accounts.google.com, discord.com/oauth2)
+    private String provider;
+
+    // ID of the OAuth client. This is usually defined when creating the OAuth application.
+    private String client_id;
+
+    // Client secret
+    private String client_secret;
+
+    // URI to redirect to. Ensure that this URI is listed in the allowed redirect URIs section
+    // of your OAuth provider.
+    private String redirect_uri;
+
+    // Which database to use (SQLite is currently the only supported database).
+    private String database;
+
+    public void load() {
+        this.config.getOrElse("provider", DEFAULT_PROVIDER);
+        this.config.getOrElse("client_id", DEFAULT_CLIENT_ID);
+        this.config.getOrElse("client_secret", DEFAULT_CLIENT_SECRET);
+        this.config.getOrElse("redirect_uri", DEFAULT_REDIRECT_URI);
+        this.config.getOrElse("database", DEFAULT_DATABASE);
+
+        try {
+            this.loadFromFile(true);
+        } catch (IOException e) {
+            throw new RuntimeException(e);
+        }
+
+        LOGGER.info("oauth-fabric: Configuration loaded.");
+    }
+
+    private void loadFromFile(boolean firstAttempt) throws IOException {
+        try (var reader = Files.newBufferedReader(CONFIG_FILE_PATH)) {
+            new TomlParser().parse(reader, this.config, ParsingMode.REPLACE);
+        } catch (NoSuchFileException | FileNotFoundException e) {
+            if (!firstAttempt) {
+                throw e;
+            }
+
+            this.copyDefaultFile();
+            this.loadFromFile(true);
+        } catch (ParsingException e) {
+            if (!firstAttempt) {
+                throw e;
+            }
+
+            var backupPath = CONFIG_FILE_PATH.resolveSibling("oauth-fabric.toml.old").toAbsolutePath().normalize();
+
+			LOGGER.error("oauth-fabric: Failed to parse configuration file, THIS IS BAD.", e);
+			LOGGER.error("oauth-fabric: Copying the corrupt file to \"{}\".", backupPath);
+			Files.copy(CONFIG_FILE_PATH, backupPath, StandardCopyOption.ATOMIC_MOVE, StandardCopyOption.REPLACE_EXISTING);
+			this.copyDefaultFile();
+			this.loadFromFile(false);
+        }
+    }
+
+    private void copyDefaultFile() throws IOException {
+        Files.createDirectories(CONFIG_FILE_PATH.getParent());
+
+        try (var writer = Files.newBufferedWriter(CONFIG_FILE_PATH, StandardCharsets.UTF_8)) {
+            new TomlWriter().write(this.config.unmodifiable(), writer);
+        } catch (NoSuchFileException | FileNotFoundException e) {
+            LOGGER.error("oauth-fabric: Failed to write default configuration file.");
+        }
+    }
+}