4 files changed, 85 insertions, 4 deletions
diff --git a/src-tauri/src/core/auth.rs b/src-tauri/src/core/auth.rs
new file mode 100644
index 0000000..39c4ce0
--- /dev/null
+++ b/src-tauri/src/core/auth.rs
@@ -0,0 +1,28 @@
+use serde::{Deserialize, Serialize};
+use std::sync::Mutex;
+use uuid::Uuid;
+
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct OfflineAccount {
+    pub username: String,
+    pub uuid: String,
+}
+
+pub struct AccountState {
+    pub active_account: Mutex<Option<OfflineAccount>>,
+}
+
+impl AccountState {
+    pub fn new() -> Self {
+        Self {
+            active_account: Mutex::new(None),
+        }
+    }
+}
+
+pub fn generate_offline_uuid(username: &str) -> String {
+    // Generate a UUID v3 (MD5-based) using the username as the name
+    // This provides a consistent UUID for the same username
+    let namespace = Uuid::NAMESPACE_OID;
+    Uuid::new_v3(&namespace, username.as_bytes()).to_string()
+}
diff --git a/src-tauri/src/core/downloader.rs b/src-tauri/src/core/downloader.rs
new file mode 100644
index 0000000..8d717be
--- /dev/null
+++ b/src-tauri/src/core/downloader.rs
@@ -0,0 +1,51 @@
+use std::path::PathBuf;
+use tokio::sync::mpsc;
+use serde::{Serialize, Deserialize};
+
+#[derive(Debug, Clone)]
+pub struct DownloadTask {
+    pub url: String,
+    pub path: PathBuf,
+    pub sha1: Option<String>,
+}
+
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub enum DownloadProgress {
+    Started(String),
+    Progress { file: String, downloaded: u64, total: u64 },
+    Finished(String),
+    Error(String, String),
+}
+
+pub struct Downloader {
+    sender: mpsc::Sender<DownloadProgress>,
+}
+
+impl Downloader {
+    pub fn new(sender: mpsc::Sender<DownloadProgress>) -> Self {
+        Self { sender }
+    }
+
+    pub async fn download(&self, tasks: Vec<DownloadTask>) {
+        // TODO: Implement parallel download with limits
+        // Use futures::stream::StreamExt::buffer_unordered
+        
+        for task in tasks {
+            if let Err(_) = self.sender.send(DownloadProgress::Started(task.url.clone())).await {
+                break;
+            }
+
+            // Simulate download for now or implement basic
+            // Ensure directory exists
+            if let Some(parent) = task.path.parent() {
+                 let _ = tokio::fs::create_dir_all(parent).await;
+            }
+
+            // Real implementation would use reqwest here
+            
+            if let Err(_) = self.sender.send(DownloadProgress::Finished(task.url)).await {
+                break;
+            }
+        }
+    }
+}
diff --git a/src-tauri/src/core/manifest.rs b/src-tauri/src/core/manifest.rs
index 1450e77..11ebc5a 100644
--- a/src-tauri/src/core/manifest.rs
+++ b/src-tauri/src/core/manifest.rs
@@ -1,19 +1,19 @@
-use serde::Deserialize;
+use serde::{Deserialize, Serialize};
 use std::error::Error;
 
-#[derive(Debug, Deserialize)]
+#[derive(Debug, Deserialize, Serialize)]
 pub struct VersionManifest {
     pub latest: Latest,
     pub versions: Vec<Version>,
 }
 
-#[derive(Debug, Deserialize)]
+#[derive(Debug, Deserialize, Serialize)]
 pub struct Latest {
     pub release: String,
     pub snapshot: String,
 }
 
-#[derive(Debug, Deserialize)]
+#[derive(Debug, Deserialize, Serialize)]
 pub struct Version {
     pub id: String,
     #[serde(rename = "type")]
diff --git a/src-tauri/src/core/mod.rs b/src-tauri/src/core/mod.rs
index 640fc64..320ab82 100644
--- a/src-tauri/src/core/mod.rs
+++ b/src-tauri/src/core/mod.rs
@@ -1 +1,3 @@
 pub mod manifest;
+pub mod auth;
+pub mod downloader;