15 files changed, 490 insertions, 0 deletions

diff --git a/src/config/loader.rs b/src/config/loader.rs
new file mode 100644
index 0000000..81a4351
--- /dev/null
+++ b/src/config/loader.rs
@@ -0,0 +1,70 @@
+use std::{env, path::PathBuf};
+
+use serde::Deserialize;
+
+use crate::{constants::*, errors::McError};
+
+#[allow(dead_code)]
+#[derive(Debug, Deserialize)]
+pub struct Config {
+    pub username: String,
+    pub uuid: String,
+    pub version: String,
+    pub java_path: String,
+    pub max_memory_mb: u32,
+    pub data_dir: PathBuf,
+    pub cache_dir: PathBuf,
+    pub config_dir: PathBuf,
+    #[serde(default)]
+    pub jvm_args: Vec<String>,
+}
+
+impl Config {
+    pub fn load() -> Result<Self, McError> {
+        let cfg_path = default_config_path()?;
+        let mut cfg: Config = if cfg_path.exists() {
+            let txt = std::fs::read_to_string(&cfg_path)?;
+            toml::from_str(&txt).map_err(|e| McError::Config(e.to_string()))?
+        } else {
+            Self::default()
+        };
+
+        if let Ok(v) = env::var("MC_USERNAME") {
+            cfg.username = v;
+        }
+        if let Ok(v) = env::var("MC_VERSION") {
+            cfg.version = v;
+        }
+        if let Ok(v) = env::var("MC_JAVA_PATH") {
+            cfg.java_path = v;
+        }
+        if let Ok(v) = env::var("MC_MAX_MEMORY_MB") {
+            cfg.max_memory_mb = v.parse().unwrap_or(cfg.max_memory_mb);
+        }
+
+        Ok(cfg)
+    }
+
+    fn default() -> Self {
+        let base =
+            directories::ProjectDirs::from("com", "example", "mccl").expect("platform dirs");
+
+        Self {
+            username: "Player".into(),
+            uuid: uuid::Uuid::new_v4().to_string(),
+            version: DEFAULT_VERSION.into(),
+            java_path: DEFAULT_JAVA_PATH.into(),
+            max_memory_mb: DEFAULT_MAX_MEMORY_MB,
+            data_dir: base.data_dir().into(),
+            cache_dir: base.cache_dir().into(),
+            config_dir: base.config_dir().into(),
+            jvm_args: vec![],
+        }
+    }
+}
+
+fn default_config_path() -> Result<PathBuf, McError> {
+    let base = directories::ProjectDirs::from("com", "example", "mccl")
+        .ok_or_else(|| McError::Config("cannot determine config dir".into()))?;
+    Ok(base.config_dir().join("config.toml"))
+}
diff --git a/src/config/mod.rs b/src/config/mod.rs
new file mode 100644
index 0000000..c5fc004
--- /dev/null
+++ b/src/config/mod.rs
@@ -0,0 +1,3 @@
+pub mod loader;
+
+pub use loader::Config;
diff --git a/src/constants.rs b/src/constants.rs
new file mode 100644
index 0000000..52833b2
--- /dev/null
+++ b/src/constants.rs
@@ -0,0 +1,13 @@
+#![allow(dead_code)]
+
+use std::time::Duration;
+
+pub const VERSION_MANIFEST_URL: &str =
+    "https://launchermeta.mojang.com/mc/game/version_manifest.json";
+
+pub const DOWNLOAD_RETRIES: usize = 3;
+pub const DOWNLOAD_BACKOFF: Duration = Duration::from_millis(400);
+
+pub const DEFAULT_MAX_MEMORY_MB: u32 = 2048;
+pub const DEFAULT_JAVA_PATH: &str = "java";
+pub const DEFAULT_VERSION: &str = "latest";
diff --git a/src/errors.rs b/src/errors.rs
new file mode 100644
index 0000000..c167733
--- /dev/null
+++ b/src/errors.rs
@@ -0,0 +1,34 @@
+use std::{fmt, io};
+
+#[allow(dead_code)]
+#[derive(Debug)]
+pub enum McError {
+    Io(io::Error),
+    Http(reqwest::Error),
+    Json(serde_json::Error),
+    Zip(zip::result::ZipError),
+    Config(String),
+    ShaMismatch(String),
+    Process(String),
+    Runtime(String), // ← NEW
+}
+
+impl fmt::Display for McError {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { write!(f, "{:?}", self) }
+}
+
+impl From<io::Error> for McError {
+    fn from(e: io::Error) -> Self { Self::Io(e) }
+}
+
+impl From<reqwest::Error> for McError {
+    fn from(e: reqwest::Error) -> Self { Self::Http(e) }
+}
+
+impl From<serde_json::Error> for McError {
+    fn from(e: serde_json::Error) -> Self { Self::Json(e) }
+}
+
+impl From<zip::result::ZipError> for McError {
+    fn from(e: zip::result::ZipError) -> Self { Self::Zip(e) }
+}
diff --git a/src/main.rs b/src/main.rs
new file mode 100644
index 0000000..8a01b9f
--- /dev/null
+++ b/src/main.rs
@@ -0,0 +1,60 @@
+mod constants;
+mod errors;
+
+mod config;
+mod minecraft;
+mod platform;
+mod util;
+
+use clap::Parser;
+use config::Config;
+use errors::McError;
+use log::{debug, info};
+
+#[derive(Parser, Debug)]
+#[command(author, about, disable_version_flag = true)]
+struct Cli {
+    #[arg(long)]
+    version: Option<String>,
+
+    #[arg(long)]
+    username: Option<String>,
+
+    #[arg(long, num_args(0..), allow_hyphen_values = true)]
+    jvm_args: Vec<String>,
+}
+
+#[tokio::main]
+async fn main() -> Result<(), McError> {
+    dotenvy::dotenv().ok();
+    env_logger::init();
+
+    let cli = Cli::parse();
+    let mut config = Config::load()?;
+
+    if let Some(v) = cli.version {
+        config.version = v;
+    }
+
+    if let Some(u) = cli.username {
+        config.username = u;
+    }
+    if !cli.jvm_args.is_empty() {
+        config.jvm_args = cli.jvm_args;
+    }
+
+    info!("Final config after CLI overrides: {:?}", config);
+
+    platform::paths::ensure_dirs(&config)?;
+    info!("Using Minecraft version {}", config.version);
+
+    let version = minecraft::manifests::load_version(&config).await?;
+    info!("Loaded version manifest for: {}", version.id);
+    debug!("Main class: {}", version.main_class);
+
+    minecraft::downloads::download_all(&config, &version).await?;
+    minecraft::extraction::extract_natives(&config, &version)?;
+    minecraft::launcher::launch(&config, &version)?;
+
+    Ok(())
+}
diff --git a/src/minecraft/downloads.rs b/src/minecraft/downloads.rs
new file mode 100644
index 0000000..5be5a05
--- /dev/null
+++ b/src/minecraft/downloads.rs
@@ -0,0 +1,66 @@
+use log::{debug, info};
+use tokio::{fs, io::AsyncWriteExt};
+
+use crate::{
+    config::Config,
+    errors::McError,
+    minecraft::manifests::{Library, Version},
+    platform::paths,
+};
+
+/// Download everything required to launch:
+/// - client jar
+/// - libraries
+pub async fn download_all(config: &Config, version: &Version) -> Result<(), McError> {
+    download_client(config, version).await?;
+    download_libraries(config, &version.libraries).await?;
+    Ok(())
+}
+
+async fn download_client(config: &Config, version: &Version) -> Result<(), McError> {
+    let jar_path = paths::client_jar(config, &version.id)?;
+
+    if jar_path.exists() {
+        debug!("Client jar already exists");
+        return Ok(());
+    }
+
+    info!("Downloading client {}", version.id);
+
+    download_file(&version.downloads.client.url, &jar_path).await
+}
+
+async fn download_libraries(config: &Config, libraries: &[Library]) -> Result<(), McError> {
+    for lib in libraries {
+        let Some(artifact) = &lib.downloads.artifact else {
+            continue;
+        };
+
+        let lib_path = paths::library_file(config, &artifact.path)?;
+
+        if lib_path.exists() {
+            continue;
+        }
+
+        info!("Downloading library {}", artifact.path);
+        download_file(&artifact.url, &lib_path).await?;
+    }
+
+    Ok(())
+}
+
+/* ---------------- helper ---------------- */
+
+async fn download_file(url: &str, path: &std::path::Path) -> Result<(), McError> {
+    if let Some(parent) = path.parent() {
+        fs::create_dir_all(parent).await?;
+    }
+
+    let response = reqwest::get(url).await?;
+    let bytes = response.bytes().await?;
+
+    let mut file = fs::File::create(path).await?;
+    file.write_all(&bytes).await?;
+
+    Ok(())
+}
diff --git a/src/minecraft/extraction.rs b/src/minecraft/extraction.rs
new file mode 100644
index 0000000..5175ee0
--- /dev/null
+++ b/src/minecraft/extraction.rs
@@ -0,0 +1,10 @@
+use log::info;
+
+use crate::errors::McError;
+pub fn extract_natives(
+    _cfg: &crate::config::Config,
+    version: &crate::minecraft::manifests::Version,
+) -> Result<(), McError> {
+    info!("Extracting natives for {}", version.id);
+    Ok(())
+}
diff --git a/src/minecraft/launcher.rs b/src/minecraft/launcher.rs
new file mode 100644
index 0000000..f7e3ecc
--- /dev/null
+++ b/src/minecraft/launcher.rs
@@ -0,0 +1,73 @@
+use std::process::Command;
+
+use log::{debug, info};
+
+use crate::{config::Config, errors::McError, minecraft::manifests::Version, platform::paths};
+
+/// Build the full classpath
+fn build_classpath(config: &Config, version: &Version) -> Result<String, McError> {
+    let sep = if cfg!(windows) { ";" } else { ":" };
+    let mut entries = Vec::new();
+
+    for lib in &version.libraries {
+        if let Some(artifact) = &lib.downloads.artifact {
+            let path = paths::library_file(config, &artifact.path)?;
+            entries.push(path.to_string_lossy().to_string());
+        }
+    }
+
+    let client_jar = paths::client_jar(config, &version.id)?;
+    entries.push(client_jar.to_string_lossy().to_string());
+    Ok(entries.join(sep))
+}
+
+/// Launch Minecraft
+pub fn launch(config: &Config, version: &Version) -> Result<(), McError> {
+    let java = &config.java_path;
+    let classpath = build_classpath(config, version)?;
+    let natives_dir = paths::natives_dir(config, &version.id);
+
+    if !natives_dir.exists() {
+        return Err(McError::Runtime(format!(
+            "Natives folder does not exist: {}",
+            natives_dir.display()
+        )));
+    }
+
+    info!("Launching Minecraft {}", version.id);
+    debug!("Classpath: {}", classpath);
+    debug!("Natives: {}", natives_dir.display());
+
+    let status = Command::new(java)
+        .arg(format!("-Xmx{}M", config.max_memory_mb))
+        .arg(format!("-Djava.library.path={}", natives_dir.display()))
+        .arg("-cp")
+        .arg(classpath)
+        .arg(&version.main_class)
+        .arg("--username")
+        .arg(&config.username)
+        .arg("--version")
+        .arg(&version.id)
+        .arg("--gameDir")
+        .arg(paths::minecraft_root(config))
+        .arg("--assetsDir")
+        .arg(paths::minecraft_root(config).join("assets"))
+        .arg("--assetIndex")
+        .arg(&version.id)
+        .arg("--uuid")
+        .arg(&config.uuid)
+        .arg("--userProperties")
+        .arg("{}")
+        .arg("--accessToken")
+        .arg("0")
+        .arg("--userType")
+        .arg("legacy")
+        .args(&config.jvm_args)
+        .status()?;
+
+    if !status.success() {
+        return Err(McError::Process("Minecraft exited with error".into()));
+    }
+
+    Ok(())
+}
diff --git a/src/minecraft/manifests.rs b/src/minecraft/manifests.rs
new file mode 100644
index 0000000..3cc59af
--- /dev/null
+++ b/src/minecraft/manifests.rs
@@ -0,0 +1,80 @@
+#![allow(dead_code)]
+use reqwest;
+use serde::Deserialize;
+
+use crate::{constants::VERSION_MANIFEST_URL, errors::McError};
+
+#[derive(Debug, Deserialize)]
+pub struct Version {
+    pub id: String,
+
+    #[serde(rename = "mainClass")]
+    pub main_class: String,
+
+    pub downloads: Downloads,
+    pub libraries: Vec<Library>,
+}
+
+#[derive(Debug, Deserialize)]
+pub struct Downloads {
+    pub client: DownloadInfo,
+}
+
+#[derive(Debug, Deserialize)]
+pub struct DownloadInfo {
+    pub url: String,
+    pub sha1: String,
+    pub size: u64,
+}
+
+#[derive(Debug, Deserialize)]
+pub struct Library {
+    pub downloads: LibraryDownloads,
+}
+
+#[derive(Debug, Deserialize)]
+pub struct LibraryDownloads {
+    pub artifact: Option<LibraryArtifact>,
+}
+
+#[derive(Debug, Deserialize)]
+pub struct LibraryArtifact {
+    pub path: String,
+    pub url: String,
+    pub sha1: String,
+    pub size: u64,
+}
+
+pub async fn load_version(cfg: &crate::config::Config) -> Result<Version, McError> {
+    let manifest_text = reqwest::get(VERSION_MANIFEST_URL)
+        .await?
+        .text()
+        .await?;
+    let root: serde_json::Value = serde_json::from_str(&manifest_text)?;
+    let version_id = if cfg.version == "latest" {
+        root["latest"]["release"]
+            .as_str()
+            .ok_or_else(|| McError::Config("missing latest.release".into()))?
+            .to_string()
+    } else {
+        cfg.version.clone()
+    };
+
+    let versions = root["versions"]
+        .as_array()
+        .ok_or_else(|| McError::Config("missing versions array".into()))?;
+
+    let version_entry = versions
+        .iter()
+        .find(|v| v["id"].as_str() == Some(&version_id))
+        .ok_or_else(|| McError::Config(format!("version '{}' not found", version_id)))?;
+
+    let url = version_entry["url"]
+        .as_str()
+        .ok_or_else(|| McError::Config("missing version url".into()))?;
+
+    let version_text = reqwest::get(url).await?.text().await?;
+    let version: Version = serde_json::from_str(&version_text)?;
+
+    Ok(version)
+}
diff --git a/src/minecraft/mod.rs b/src/minecraft/mod.rs
new file mode 100644
index 0000000..f1ce1f0
--- /dev/null
+++ b/src/minecraft/mod.rs
@@ -0,0 +1,4 @@
+pub mod downloads;
+pub mod extraction;
+pub mod launcher;
+pub mod manifests;
diff --git a/src/platform/mod.rs b/src/platform/mod.rs
new file mode 100644
index 0000000..8118b29
--- /dev/null
+++ b/src/platform/mod.rs
@@ -0,0 +1 @@
+pub mod paths;
diff --git a/src/platform/paths.rs b/src/platform/paths.rs
new file mode 100644
index 0000000..47aae9a
--- /dev/null
+++ b/src/platform/paths.rs
@@ -0,0 +1,48 @@
+use std::{fs, path::PathBuf};
+
+use directories::ProjectDirs;
+
+use crate::{config::Config, errors::McError};
+
+fn project_dirs() -> ProjectDirs {
+    ProjectDirs::from("com", "dml", "dml").expect("failed to determine project directories")
+}
+
+/// Root Minecraft directory
+pub fn minecraft_root(_cfg: &Config) -> PathBuf { project_dirs().data_dir().join("minecraft") }
+
+/* ---------------- setup ---------------- */
+
+pub fn ensure_dirs(cfg: &Config) -> Result<(), McError> {
+    let root = minecraft_root(cfg);
+
+    fs::create_dir_all(root.join("versions"))?;
+    fs::create_dir_all(root.join("libraries"))?;
+    fs::create_dir_all(root.join("assets"))?;
+
+    Ok(())
+}
+
+/* ---------------- versions ---------------- */
+
+pub fn version_dir(cfg: &Config, version: &str) -> PathBuf {
+    minecraft_root(cfg).join("versions").join(version)
+}
+
+pub fn client_jar(cfg: &Config, version: &str) -> Result<PathBuf, McError> {
+    Ok(version_dir(cfg, version).join(format!("{}.jar", version)))
+}
+
+/* ---------------- libraries ---------------- */
+
+pub fn library_file(cfg: &Config, rel_path: &str) -> Result<PathBuf, McError> {
+    Ok(minecraft_root(cfg)
+        .join("libraries")
+        .join(rel_path))
+}
+
+/* ---------------- natives ---------------- */
+
+pub fn natives_dir(cfg: &Config, version: &str) -> PathBuf {
+    version_dir(cfg, version).join("natives")
+}
diff --git a/src/util/fs.rs b/src/util/fs.rs
new file mode 100644
index 0000000..b86c0d7
--- /dev/null
+++ b/src/util/fs.rs
@@ -0,0 +1,12 @@
+#![allow(dead_code)]
+
+use std::path::Path;
+
+use crate::errors::McError;
+
+pub async fn remove_if_exists(path: &Path) -> Result<(), McError> {
+    if path.exists() {
+        tokio::fs::remove_file(path).await?;
+    }
+    Ok(())
+}
diff --git a/src/util/mod.rs b/src/util/mod.rs
new file mode 100644
index 0000000..8176b9b
--- /dev/null
+++ b/src/util/mod.rs
@@ -0,0 +1,2 @@
+pub mod fs;
+pub mod sha1;
diff --git a/src/util/sha1.rs b/src/util/sha1.rs
new file mode 100644
index 0000000..c5f1021
--- /dev/null
+++ b/src/util/sha1.rs
@@ -0,0 +1,14 @@
+#![allow(dead_code)]
+
+use std::path::Path;
+
+use sha1::{Digest, Sha1};
+
+use crate::errors::McError;
+
+pub async fn sha1_hex(path: &Path) -> Result<String, McError> {
+    let data = tokio::fs::read(path).await?;
+    let mut hasher = Sha1::new();
+    hasher.update(&data);
+    Ok(format!("{:x}", hasher.finalize()))
+}