1 files changed, 110 insertions, 0 deletions

diff --git a/src/constants.rs b/src/constants.rs
index 3234fe6..72de325 100644
--- a/src/constants.rs
+++ b/src/constants.rs
@@ -1,13 +1,123 @@
 #![allow(dead_code)]
 
+//! Constants module for the DML Launcher.
+//!
+//! This module defines immutable configuration values and defaults
+//! used throughout the launcher. These constants provide a single
+//! source of truth for URLs, download behavior, memory settings,
+//! JVM defaults, download concurrency, directory names, and version selection.
+//!
+//! Centralizing these constants ensures consistency across the
+//! application and simplifies maintenance when defaults need to change.
+
 use std::time::Duration;
 
+/// URL to the Minecraft version manifest.
+///
+/// This manifest contains metadata for all available Minecraft
+/// releases, including release dates, type (release, snapshot),
+/// and download URLs for the client and server distributions.
 pub const VERSION_MANIFEST_URL: &str =
     "https://launchermeta.mojang.com/mc/game/version_manifest.json";
 
+/// Number of times to retry a failed download.
+///
+/// Used by asset and library download routines to tolerate
+/// transient network failures. Downloads will be retried
+/// up to this number of attempts before returning an error.
 pub const DOWNLOAD_RETRIES: usize = 3;
+
+/// Duration to wait between download retries.
+///
+/// Provides fixed delay for network resilience when fetching
+/// game assets. Specified in milliseconds.
 pub const DOWNLOAD_BACKOFF: Duration = Duration::from_millis(400);
 
+/// Default maximum memory allocation for the Minecraft JVM process in
+/// megabytes.
+///
+/// If the user does not specify memory settings via configuration
+/// or JVM arguments, this value will be applied as the default heap size.
 pub const DEFAULT_MAX_MEMORY_MB: u32 = 4048;
+
+/// Default path to the Java executable.
+///
+/// Used when launching the Minecraft client. Can be overridden
+/// via configuration or environment variables if a custom Java
+/// installation is required.
 pub const DEFAULT_JAVA_PATH: &str = "java";
+
+/// Default Minecraft version to launch when no specific version is provided.
+///
+/// The launcher will resolve "latest" to the most recent stable release
+/// according to the version manifest.
 pub const DEFAULT_VERSION: &str = "latest";
+
+/// Default Java major version for launching Minecraft.
+///
+/// This value is used when generating the JVM runtime configuration
+/// for the launcher.
+pub const DEFAULT_JAVA_MAJOR: u8 = 8;
+
+/// Default number of concurrent downloads for libraries.
+///
+/// Limits the number of simultaneous HTTP requests when fetching
+/// Minecraft libraries to avoid saturating network or file handles.
+pub const DEFAULT_LIBRARY_CONCURRENCY: usize = 20;
+
+/// Default number of concurrent downloads for assets.
+///
+/// Limits the number of simultaneous HTTP requests when fetching
+/// Minecraft assets to optimize throughput without overloading the system.
+pub const DEFAULT_ASSET_CONCURRENCY: usize = 20;
+
+/// Default launcher cache directory name.
+///
+/// Used as the base subdirectory for downloaded assets, libraries,
+/// versions, and configuration.
+pub const DEFAULT_LAUNCHER_DIR: &str = "dml";
+
+/// Default environment variable names for overriding configuration.
+pub const ENV_USERNAME: &str = "MC_USERNAME";
+pub const ENV_VERSION: &str = "MC_VERSION";
+pub const ENV_JAVA_PATH: &str = "MC_JAVA_PATH";
+pub const ENV_MAX_MEMORY_MB: &str = "MC_MAX_MEMORY_MB";
+
+/// Default project/platform constants for `directories::ProjectDirs`.
+pub const DEFAULT_COMPANY: &str = "com";
+pub const DEFAULT_PROJECT_GROUP: &str = "example";
+pub const DEFAULT_PROJECT_NAME: &str = "dml";
+
+/// Default error messages for common failures.
+pub const DEFAULT_ERR_PLATFORM_DIR: &str = "cannot determine config dir";
+pub const DEFAULT_ERR_CREATE_DIR: &str = "failed to create directory";
+
+/// Default configuration filename within the launcher directory.
+pub const DEFAULT_CONFIG_FILENAME: &str = "config.toml";
+
+/// Default username if none is provided by environment or config.
+pub const DEFAULT_USERNAME: &str = "phil";
+
+/// Default subdirectory names within the launcher directory.
+pub mod directory {
+    /// Directory for Minecraft versions.
+    pub const VERSIONS: &str = "versions";
+
+    /// Directory for downloaded libraries.
+    pub const LIBRARIES: &str = "libraries";
+
+    /// Directory for Minecraft assets.
+    pub const ASSETS: &str = "assets";
+
+    /// Subdirectory for asset indexes.
+    pub const INDEXES: &str = "indexes";
+
+    /// Subdirectory for asset objects.
+    pub const OBJECTS: &str = "objects";
+
+    /// Directory for native libraries.
+    pub const NATIVES: &str = "natives";
+
+    /// Directory for saved worlds.
+    pub const SAVES: &str = "saves";
+}