# 🔄 **apt-ostree Package Override System Architecture**

## 📋 **Overview**

This document outlines the package override system architecture for apt-ostree, based on analysis of how rpm-ostree implements package overrides, base package replacement, and package customization. The override system allows users to replace base packages with custom versions while maintaining system integrity.

## 🔗 **Related Documents**

- **Core Architecture**: [Overview](overview.md) | [CLI-Daemon Separation](cli-daemon-separation.md)
- **Package Management**: [APT Integration](apt-library-analysis.md) | [Package Overrides](package-overrides.md)
- **System Operations**: [Transaction System](transaction-system.md) | [Live Updates](live-updates.md)
- **Security**: [Responsibility Analysis](responsibility-analysis.md) | [Error Handling](error-handling-analysis.md)

## 🏗️ **Architecture Overview**

### **Component Separation**

```
┌─────────────────┐    ┌─────────────────┐    ┌─────────────────┐
│   CLI Client    │    │   Rust Core     │    │   Rust Daemon   │
│   (apt-ostree)  │◄──►│   (DBus)        │◄──►│   (aptostreed)  │
│                 │    │                 │    │                 │
│ • override      │    │ • Client Logic  │    │ • Override      │
│ • reset         │    │ • DBus Client   │    │ • Package       │
│ • list          │    │ • Override Mgmt │    │ • State Mgmt    │
└─────────────────┘    └─────────────────┘    └─────────────────┘
```

### **Responsibility Distribution**

#### **CLI Client (`apt-ostree`)**
- **Command parsing** for override subcommands
- **User interface** and override management
- **DBus communication** with daemon
- **Override validation** and processing

#### **Daemon (`apt-ostreed`)**
- **Override application** and management
- **Package replacement** and installation
- **Override state** persistence
- **Conflict resolution** and validation

## 🔍 **rpm-ostree Implementation Analysis**

### **Override Commands Structure**

Based on `rpmostree-builtin-override.cxx`, rpm-ostree provides these override subcommands:

```c
static RpmOstreeCommand override_subcommands[]
    = { { "replace", RPM_OSTREE_BUILTIN_FLAG_REQUIRES_ROOT,
          "Replace a base package with a different version", rpmostree_override_builtin_replace },
        { "reset", RPM_OSTREE_BUILTIN_FLAG_REQUIRES_ROOT,
          "Reset a package override to base version", rpmostree_override_builtin_reset },
        { "list", RPM_OSTREE_BUILTIN_FLAG_LOCAL_CMD,
          "List current package overrides", rpmostree_override_builtin_list },
        { NULL, (RpmOstreeBuiltinFlags)0, NULL, NULL } };
```

### **Key Insights from rpm-ostree**

1. **Package Replacement**: Can replace base packages with different versions
2. **Override Persistence**: Overrides are stored and persist across deployments
3. **Conflict Resolution**: Handles package conflicts and dependencies
4. **Reset Capability**: Can restore packages to base versions

## 🚀 **apt-ostree Implementation Strategy**

### **1. CLI Command Structure**

```rust
// src/main.rs - Override command handling
async fn override_commands(args: &[String]) -> AptOstreeResult<()> {
    if args.is_empty() {
        show_override_help();
        return Ok(());
    }
    
    let subcommand = &args[0];
    match subcommand.as_str() {
        "replace" => override_replace(&args[1..]).await?,
        "reset" => override_reset(&args[1..]).await?,
        "list" => override_list(&args[1..]).await?,
        _ => {
            println!("❌ Unknown override subcommand: {}", subcommand);
            show_override_help();
        }
    }
    Ok(())
}
```

### **2. Package Override System**

#### **Core Override Manager**

```rust
// src/override/override_manager.rs
pub struct OverrideManager {
    ostree_manager: Arc<OstreeManager>,
    apt_manager: Arc<AptManager>,
    override_store: Arc<RwLock<OverrideStore>>,
    security_manager: Arc<SecurityManager>,
}

impl OverrideManager {
    pub async fn replace_package(
        &self,
        package_name: &str,
        new_version: &str,
        user_id: u32,
        session_id: String,
    ) -> Result<OverrideResult, Error> {
        // Validate package override request
        self.validate_override_request(package_name, new_version).await?;
        
        // Check user authorization
        self.security_manager
            .authorize_package_override(package_name, user_id)
            .await?;
        
        // Get current deployment
        let current_deployment = self.ostree_manager.get_booted_deployment().await?;
        
        // Create staging deployment
        let staging_ref = self.ostree_manager.create_staging_deployment().await?;
        
        // Remove base package from staging
        self.remove_base_package_from_staging(&staging_ref, package_name).await?;
        
        // Install new package version to staging
        let package_info = self.apt_manager
            .get_package_info(package_name, new_version)
            .await?;
        
        self.install_package_to_staging(&staging_ref, &package_info).await?;
        
        // Resolve and install dependencies
        let dependencies = self.apt_manager
            .resolve_package_dependencies(&package_info)
            .await?;
        
        for dependency in &dependencies {
            self.install_package_to_staging(&staging_ref, dependency).await?;
        }
        
        // Execute package scripts
        self.execute_package_scripts(&staging_ref, &[package_info.clone()]).await?;
        
        // Commit staging deployment
        let commit_hash = self.ostree_manager.commit_staging_deployment(
            &staging_ref,
            &format!("Override package: {} -> {}", package_name, new_version),
        ).await?;
        
        // Update boot configuration
        self.ostree_manager.set_default_deployment(&commit_hash).await?;
        
        // Store override information
        let override_info = PackageOverride {
            package_name: package_name.to_string(),
            base_version: self.get_base_package_version(package_name).await?,
            override_version: new_version.to_string(),
            user_id,
            session_id,
            created_at: chrono::Utc::now(),
            commit_hash: commit_hash.clone(),
        };
        
        self.override_store
            .write()
            .await
            .add_override(override_info)
            .await?;
        
        Ok(OverrideResult::Success {
            message: format!("Package {} overridden to version {}", package_name, new_version),
            commit_hash,
            details: Some(format!("Base version: {}", override_info.base_version)),
        })
    }
    
    pub async fn reset_package(
        &self,
        package_name: &str,
        user_id: u32,
        session_id: String,
    ) -> Result<OverrideResult, Error> {
        // Check if package has an override
        let override_info = self.override_store
            .read()
            .await
            .get_override(package_name)
            .await?;
        
        if override_info.is_none() {
            return Err(Error::NoOverrideFound(package_name.to_string()));
        }
        
        let override_info = override_info.unwrap();
        
        // Check user authorization
        self.security_manager
            .authorize_package_override(package_name, user_id)
            .await?;
        
        // Get current deployment
        let current_deployment = self.ostree_manager.get_booted_deployment().await?;
        
        // Create staging deployment
        let staging_ref = self.ostree_manager.create_staging_deployment().await?;
        
        // Remove overridden package from staging
        self.remove_package_from_staging(&staging_ref, package_name).await?;
        
        // Restore base package to staging
        let base_package = self.apt_manager
            .get_base_package(package_name)
            .await?;
        
        self.install_package_to_staging(&staging_ref, &base_package).await?;
        
        // Commit staging deployment
        let commit_hash = self.ostree_manager.commit_staging_deployment(
            &staging_ref,
            &format!("Reset package override: {} -> base version", package_name),
        ).await?;
        
        // Update boot configuration
        self.ostree_manager.set_default_deployment(&commit_hash).await?;
        
        // Remove override from store
        self.override_store
            .write()
            .await
            .remove_override(package_name)
            .await?;
        
        Ok(OverrideResult::Success {
            message: format!("Package {} reset to base version", package_name),
            commit_hash,
            details: Some(format!("Base version: {}", base_package.version)),
        })
    }
    
    pub async fn list_overrides(&self) -> Result<Vec<PackageOverride>, Error> {
        let overrides = self.override_store
            .read()
            .await
            .list_overrides()
            .await?;
        
        Ok(overrides)
    }
    
    async fn validate_override_request(
        &self,
        package_name: &str,
        new_version: &str,
    ) -> Result<(), Error> {
        // Check if package exists in base system
        if !self.apt_manager.base_package_exists(package_name).await? {
            return Err(Error::BasePackageNotFound(package_name.to_string()));
        }
        
        // Check if new version exists
        if !self.apt_manager.package_version_exists(package_name, new_version).await? {
            return Err(Error::PackageVersionNotFound(
                package_name.to_string(),
                new_version.to_string(),
            ));
        }
        
        // Check for package conflicts
        let conflicts = self.apt_manager
            .check_package_conflicts(package_name, new_version)
            .await?;
        
        if !conflicts.is_empty() {
            return Err(Error::PackageConflicts(conflicts));
        }
        
        // Check if package is already overridden
        if self.override_store
            .read()
            .await
            .has_override(package_name)
            .await? {
            return Err(Error::PackageAlreadyOverridden(package_name.to_string()));
        }
        
        Ok(())
    }
    
    async fn remove_base_package_from_staging(
        &self,
        staging_ref: &str,
        package_name: &str,
    ) -> Result<(), Error> {
        // Get staging deployment path
        let staging_path = self.ostree_manager.get_staging_path(staging_ref);
        
        // Remove package files from staging
        let package_files = self.apt_manager
            .get_package_files(package_name)
            .await?;
        
        for file_path in &package_files {
            let full_path = staging_path.join(file_path);
            if full_path.exists() {
                tokio::fs::remove_file(&full_path).await?;
            }
        }
        
        // Remove package from package database
        let dpkg_status_path = staging_path.join("var/lib/dpkg/status");
        self.remove_package_from_dpkg_status(&dpkg_status_path, package_name).await?;
        
        Ok(())
    }
    
    async fn install_package_to_staging(
        &self,
        staging_ref: &str,
        package_info: &PackageInfo,
    ) -> Result<(), Error> {
        // Get staging deployment path
        let staging_path = self.ostree_manager.get_staging_path(staging_ref);
        
        // Download package
        let package_path = self.apt_manager
            .download_package(&package_info.name, &package_info.version)
            .await?;
        
        // Extract package to staging
        self.extract_package_to_staging(&staging_path, &package_path).await?;
        
        // Update package database
        self.update_package_database_in_staging(&staging_path, package_info).await?;
        
        Ok(())
    }
    
    async fn extract_package_to_staging(
        &self,
        staging_path: &Path,
        package_path: &Path,
    ) -> Result<(), Error> {
        // Extract DEB package contents
        let package_contents = self.extract_deb_package(package_path).await?;
        
        // Apply files to staging
        for (file_path, file_content) in package_contents.files {
            let full_path = staging_path.join(&file_path);
            
            // Create parent directories
            if let Some(parent) = full_path.parent() {
                tokio::fs::create_dir_all(parent).await?;
            }
            
            // Write file content
            tokio::fs::write(&full_path, file_content).await?;
        }
        
        // Store package scripts
        if let Some(scripts) = package_contents.scripts {
            self.store_package_scripts_in_staging(staging_path, &scripts).await?;
        }
        
        Ok(())
    }
    
    async fn execute_package_scripts(
        &self,
        staging_ref: &str,
        packages: &[PackageInfo],
    ) -> Result<(), Error> {
        // Get staging deployment path
        let staging_path = self.ostree_manager.get_staging_path(staging_ref);
        
        for package in packages {
            // Execute preinst script if exists
            if let Some(preinst_script) = self.get_package_script(&staging_path, package, "preinst").await? {
                self.execute_script_in_staging(&staging_path, &preinst_script).await?;
            }
            
            // Execute postinst script if exists
            if let Some(postinst_script) = self.get_package_script(&staging_path, package, "postinst").await? {
                self.execute_script_in_staging(&staging_path, &postinst_script).await?;
            }
        }
        
        Ok(())
    }
    
    async fn execute_script_in_staging(
        &self,
        staging_path: &Path,
        script_path: &Path,
    ) -> Result<(), Error> {
        // Create sandboxed environment
        let mut sandbox = self.create_staging_sandbox(staging_path).await?;
        
        // Execute script in sandbox
        let output = sandbox.exec_script(script_path).await?;
        
        if !output.status.success() {
            return Err(Error::ScriptExecutionFailed {
                script: script_path.to_string_lossy().to_string(),
                stderr: output.stderr,
                exit_code: output.status.code(),
            });
        }
        
        Ok(())
    }
}
```

### **3. Override Store and Persistence**

#### **Override Storage System**

```rust
// src/override/override_store.rs
pub struct OverrideStore {
    database: Arc<RwLock<Database>>,
    storage_path: PathBuf,
}

impl OverrideStore {
    pub async fn add_override(
        &self,
        override_info: PackageOverride,
    ) -> Result<(), Error> {
        // Save to database
        self.database
            .write()
            .await
            .save_override(&override_info.package_name, &override_info)
            .await?;
        
        // Save to file system for recovery
        let file_path = self.storage_path.join(format!("{}.json", override_info.package_name));
        let content = serde_json::to_string_pretty(&override_info)?;
        tokio::fs::write(&file_path, content).await?;
        
        Ok(())
    }
    
    pub async fn get_override(
        &self,
        package_name: &str,
    ) -> Result<Option<PackageOverride>, Error> {
        // Try database first
        if let Some(override_info) = self.database
            .read()
            .await
            .load_override(package_name)
            .await? {
            return Ok(Some(override_info));
        }
        
        // Fallback to file system
        let file_path = self.storage_path.join(format!("{}.json", package_name));
        if file_path.exists() {
            let content = tokio::fs::read_to_string(&file_path).await?;
            let override_info: PackageOverride = serde_json::from_str(&content)?;
            return Ok(Some(override_info));
        }
        
        Ok(None)
    }
    
    pub async fn list_overrides(&self) -> Result<Vec<PackageOverride>, Error> {
        // Get from database
        let overrides = self.database
            .read()
            .await
            .list_overrides()
            .await?;
        
        Ok(overrides)
    }
    
    pub async fn remove_override(
        &self,
        package_name: &str,
    ) -> Result<(), Error> {
        // Remove from database
        self.database
            .write()
            .await
            .delete_override(package_name)
            .await?;
        
        // Remove from file system
        let file_path = self.storage_path.join(format!("{}.json", package_name));
        if file_path.exists() {
            tokio::fs::remove_file(&file_path).await?;
        }
        
        Ok(())
    }
    
    pub async fn has_override(&self, package_name: &str) -> Result<bool, Error> {
        let override_info = self.get_override(package_name).await?;
        Ok(override_info.is_some())
    }
    
    pub async fn cleanup_orphaned_overrides(&self) -> Result<(), Error> {
        let overrides = self.list_overrides().await?;
        
        for override_info in overrides {
            // Check if override commit still exists
            if !self.ostree_manager.commit_exists(&override_info.commit_hash).await? {
                // Remove orphaned override
                self.remove_override(&override_info.package_name).await?;
            }
        }
        
        Ok(())
    }
}
```

### **4. CLI Command Implementations**

#### **Replace Command**

```rust
// src/commands/override_replace.rs
pub async fn override_replace(args: &[String]) -> AptOstreeResult<()> {
    let mut osname = None;
    let mut package_name = None;
    let mut new_version = None;
    let mut reboot = false;
    let mut lock_finalization = false;
    
    // Parse arguments
    let mut i = 0;
    while i < args.len() {
        match args[i].as_str() {
            "--os" => {
                if i + 1 < args.len() {
                    osname = Some(args[i + 1].clone());
                    i += 2;
                } else {
                    return Err(AptOstreeError::InvalidArgument("--os requires a value".to_string()));
                }
            }
            "--stateroot" => {
                if i + 1 < args.len() {
                    osname = Some(args[i + 1].clone());
                    i += 2;
                } else {
                    return Err(AptOstreeError::InvalidArgument("--stateroot requires a value".to_string()));
                }
            }
            "--reboot" => {
                reboot = true;
                i += 1;
            }
            "--lock-finalization" => {
                lock_finalization = true;
                i += 1;
            }
            _ => {
                if package_name.is_none() {
                    package_name = Some(args[i].clone());
                } else if new_version.is_none() {
                    new_version = Some(args[i].clone());
                } else {
                    return Err(AptOstreeError::InvalidArgument(
                        format!("Unexpected argument: {}", args[i]),
                    ));
                }
                i += 1;
            }
        }
    }
    
    // Validate arguments
    let package_name = package_name.ok_or_else(|| {
        AptOstreeError::InvalidArgument("PACKAGE is required".to_string())
    })?;
    
    let new_version = new_version.ok_or_else(|| {
        AptOstreeError::InvalidArgument("VERSION is required".to_string())
    })?;
    
    // Initialize override manager
    let override_manager = OverrideManager::new(osname.as_deref()).await?;
    
    // Get user and session information
    let user_id = get_current_user_id()?;
    let session_id = get_current_session_id().await?;
    
    // Replace package
    let result = override_manager
        .replace_package(&package_name, &new_version, user_id, session_id)
        .await?;
    
    // Display results
    match result {
        OverrideResult::Success { message, commit_hash, details } => {
            println!("✅ {}", message);
            println!("📝 Commit: {}", commit_hash);
            if let Some(details) = details {
                println!("ℹ️  {}", details);
            }
            
            if reboot {
                println!("🔄 Rebooting system...");
                // Trigger reboot
                trigger_system_reboot().await?;
            }
        }
        OverrideResult::Failure { message, details } => {
            println!("❌ {}", message);
            if let Some(details) = details {
                println!("ℹ️  {}", details);
            }
        }
    }
    
    Ok(())
}
```

#### **Reset Command**

```rust
// src/commands/override_reset.rs
pub async fn override_reset(args: &[String]) -> AptOstreeResult<()> {
    let mut osname = None;
    let mut package_name = None;
    let mut reboot = false;
    let mut lock_finalization = false;
    
    // Parse arguments
    let mut i = 0;
    while i < args.len() {
        match args[i].as_str() {
            "--os" => {
                if i + 1 < args.len() {
                    osname = Some(args[i + 1].clone());
                    i += 2;
                } else {
                    return Err(AptOstreeError::InvalidArgument("--os requires a value".to_string()));
                }
            }
            "--stateroot" => {
                if i + 1 < args.len() {
                    osname = Some(args[i + 1].clone());
                    i += 2;
                } else {
                    return Err(AptOstreeError::InvalidArgument("--stateroot requires a value".to_string()));
                }
            }
            "--reboot" => {
                reboot = true;
                i += 1;
            }
            "--lock-finalization" => {
                lock_finalization = true;
                i += 1;
            }
            _ => {
                if package_name.is_none() {
                    package_name = Some(args[i].clone());
                } else {
                    return Err(AptOstreeError::InvalidArgument(
                        format!("Unexpected argument: {}", args[i]),
                    ));
                }
                i += 1;
            }
        }
    }
    
    // Validate arguments
    let package_name = package_name.ok_or_else(|| {
        AptOstreeError::InvalidArgument("PACKAGE is required".to_string())
    })?;
    
    // Initialize override manager
    let override_manager = OverrideManager::new(osname.as_deref()).await?;
    
    // Get user and session information
    let user_id = get_current_user_id()?;
    let session_id = get_current_session_id().await?;
    
    // Reset package
    let result = override_manager
        .reset_package(&package_name, user_id, session_id)
        .await?;
    
    // Display results
    match result {
        OverrideResult::Success { message, commit_hash, details } => {
            println!("✅ {}", message);
            println!("📝 Commit: {}", commit_hash);
            if let Some(details) = details {
                println!("ℹ️  {}", details);
            }
            
            if reboot {
                println!("🔄 Rebooting system...");
                // Trigger reboot
                trigger_system_reboot().await?;
            }
        }
        OverrideResult::Failure { message, details } => {
            println!("❌ {}", message);
            if let Some(details) = details {
                println!("ℹ️  {}", details);
            }
        }
    }
    
    Ok(())
}
```

#### **List Command**

```rust
// src/commands/override_list.rs
pub async fn override_list(args: &[String]) -> AptOstreeResult<()> {
    let mut osname = None;
    
    // Parse arguments
    let mut i = 0;
    while i < args.len() {
        match args[i].as_str() {
            "--os" => {
                if i + 1 < args.len() {
                    osname = Some(args[i + 1].clone());
                    i += 2;
                } else {
                    return Err(AptOstreeError::InvalidArgument("--os requires a value".to_string()));
                }
            }
            "--stateroot" => {
                if i + 1 < args.len() {
                    osname = Some(args[i + 1].clone());
                    i += 2;
                } else {
                    return Err(AptOstreeError::InvalidArgument("--stateroot requires a value".to_string()));
                }
            }
            _ => {
                return Err(AptOstreeError::InvalidArgument(
                    format!("Unknown option: {}", args[i]),
                ));
            }
        }
    }
    
    // Initialize override manager
    let override_manager = OverrideManager::new(osname.as_deref()).await?;
    
    // List overrides
    let overrides = override_manager.list_overrides().await?;
    
    // Display results
    if overrides.is_empty() {
        println!("📦 No package overrides found");
    } else {
        println!("📦 Package overrides ({}):", overrides.len());
        println!("========================");
        
        for override_info in overrides {
            println!("  • {}: {} → {}", 
                override_info.package_name,
                override_info.base_version,
                override_info.override_version
            );
            println!("    User: {} | Created: {}", 
                override_info.user_id,
                override_info.created_at.format("%Y-%m-%d %H:%M:%S UTC")
            );
            println!("    Commit: {}", override_info.commit_hash);
            println!();
        }
    }
    
    Ok(())
}
```

## 🔐 **Security and Privileges**

### **1. Override Authorization**

```rust
// Security checks for package overrides
impl SecurityManager {
    pub async fn authorize_package_override(
        &self,
        package_name: &str,
        user_id: u32,
    ) -> Result<(), SecurityError> {
        // Check if user has permission to override packages
        let action = "org.projectatomic.aptostree.override";
        
        self.check_authorization(action, user_id, HashMap::new()).await?;
        
        // Check if package is in protected list
        if self.is_protected_package(package_name).await? {
            return Err(SecurityError::ProtectedPackage(
                "Cannot override protected system package".to_string(),
            ));
        }
        
        Ok(())
    }
    
    async fn is_protected_package(&self, package_name: &str) -> Result<bool, Error> {
        // List of packages that cannot be overridden
        let protected_packages = [
            "systemd", "systemd-sysv", "systemd-udev",
            "ostree", "apt-ostree", "aptostreed",
            "linux-image-generic", "linux-headers-generic",
        ];
        
        Ok(protected_packages.contains(&package_name))
    }
}
```

### **2. Override Validation**

```rust
// Validate override requests
impl OverrideManager {
    async fn validate_override_safety(
        &self,
        package_name: &str,
        new_version: &str,
    ) -> Result<(), Error> {
        // Check if override would break system
        let system_impact = self.assess_system_impact(package_name, new_version).await?;
        
        if system_impact.critical_dependencies_affected {
            return Err(Error::CriticalDependenciesAffected(
                "Override would break critical system dependencies".to_string(),
            ));
        }
        
        if system_impact.boot_affected {
            return Err(Error::BootAffected(
                "Override would affect system boot process".to_string(),
            ));
        }
        
        if system_impact.security_implications {
            tracing::warn!("Package override has security implications: {}", package_name);
        }
        
        Ok(())
    }
    
    async fn assess_system_impact(
        &self,
        package_name: &str,
        new_version: &str,
    ) -> Result<SystemImpact, Error> {
        // Analyze package dependencies and system impact
        let package_info = self.apt_manager
            .get_package_info(package_name, new_version)
            .await?;
        
        let dependencies = self.apt_manager
            .resolve_package_dependencies(&package_info)
            .await?;
        
        let mut impact = SystemImpact::new();
        
        for dependency in &dependencies {
            if self.is_critical_system_package(dependency).await? {
                impact.critical_dependencies_affected = true;
            }
            
            if self.is_boot_critical_package(dependency).await? {
                impact.boot_affected = true;
            }
            
            if self.has_security_implications(dependency).await? {
                impact.security_implications = true;
            }
        }
        
        Ok(impact)
    }
}
```

## 📊 **Performance Optimization**

### **1. Override Caching**

```rust
// Cache override information
impl OverrideManager {
    pub async fn get_cached_override(
        &self,
        package_name: &str,
    ) -> Result<Option<PackageOverride>, Error> {
        // Check cache first
        if let Some(cached) = self.cache.get_override(package_name).await? {
            return Ok(Some(cached));
        }
        
        // Fetch from store
        let override_info = self.override_store
            .read()
            .await
            .get_override(package_name)
            .await?;
        
        // Cache the result
        if let Some(ref info) = override_info {
            self.cache.cache_override(info).await?;
        }
        
        Ok(override_info)
    }
}
```

### **2. Parallel Override Processing**

```rust
// Parallel override operations
impl OverrideManager {
    pub async fn batch_overrides(
        &self,
        overrides: Vec<OverrideRequest>,
    ) -> Result<Vec<OverrideResult>, Error> {
        let mut tasks = JoinSet::new();
        
        // Spawn parallel override tasks
        for override_request in overrides {
            let override_manager = self.clone();
            
            tasks.spawn(async move {
                override_manager
                    .replace_package(
                        &override_request.package_name,
                        &override_request.new_version,
                        override_request.user_id,
                        override_request.session_id,
                    )
                    .await
            });
        }
        
        // Collect results
        let mut results = Vec::new();
        while let Some(result) = tasks.join_next().await {
            results.push(result??);
        }
        
        Ok(results)
    }
}
```

## 🧪 **Testing Strategy**

### **1. Unit Tests**

```rust
#[cfg(test)]
mod tests {
    use super::*;
    
    #[tokio::test]
    async fn test_package_override_creation() {
        let override_manager = OverrideManager::new().await.unwrap();
        let result = override_manager
            .replace_package("vim", "2:9.0.1378-1", 1000, "session-123".to_string())
            .await
            .unwrap();
        
        assert!(matches!(result, OverrideResult::Success { .. }));
    }
    
    #[tokio::test]
    async fn test_package_override_reset() {
        let override_manager = OverrideManager::new().await.unwrap();
        
        // First create an override
        override_manager
            .replace_package("vim", "2:9.0.1378-1", 1000, "session-123".to_string())
            .await
            .unwrap();
        
        // Then reset it
        let result = override_manager
            .reset_package("vim", 1000, "session-123".to_string())
            .await
            .unwrap();
        
        assert!(matches!(result, OverrideResult::Success { .. }));
    }
}
```

### **2. Integration Tests**

```rust
#[tokio::test]
async fn test_full_override_workflow() {
    // Set up test environment
    let test_repo = create_test_repository().await?;
    
    // Initialize override manager
    let override_manager = OverrideManager::new(&test_repo.path()).await?;
    
    // Test package override
    let result = override_manager
        .replace_package("test-package", "2.0.0", 1000, "session-123".to_string())
        .await?;
    assert!(matches!(result, OverrideResult::Success { .. }));
    
    // Verify override exists
    let overrides = override_manager.list_overrides().await?;
    assert!(overrides.iter().any(|o| o.package_name == "test-package"));
    
    // Test package reset
    let reset_result = override_manager
        .reset_package("test-package", 1000, "session-123".to_string())
        .await?;
    assert!(matches!(reset_result, OverrideResult::Success { .. }));
    
    // Verify override removed
    let overrides_after = override_manager.list_overrides().await?;
    assert!(!overrides_after.iter().any(|o| o.package_name == "test-package"));
}
```

## 🚀 **Future Enhancements**

### **1. Advanced Override Features**
- **Conditional overrides** based on system state
- **Override groups** and batch management
- **Override templates** and presets
- **Override validation** rules and policies

### **2. Performance Improvements**
- **Incremental overrides** with minimal rebuilds
- **Override dependency** analysis and optimization
- **Background override** processing
- **Override conflict** resolution and prevention

### **3. Integration Features**
- **External override** sources and repositories
- **Override monitoring** and alerting
- **Override analytics** and reporting
- **Automated override** testing and validation

## 🗺️ **Implementation Roadmap**

### **Phase 1: Core Foundation** 🏗️
- [ ] **Basic Override Structure** - Core override manager and store
- [ ] **Package Validation** - Override request validation and safety checks
- [ ] **Basic CLI Commands** - Override replace, reset, and list commands

### **Phase 2: Advanced Features** 🚀
- [ ] **Conflict Resolution** - Package conflict detection and resolution
- [ ] **Dependency Management** - Override dependency handling
- [ ] **Rollback Support** - Override rollback and recovery

### **Phase 3: Production Features** 🎯
- [ ] **Security Integration** - Polkit authorization and privilege management
- [ ] **Performance Optimization** - Caching and parallel processing
- [ ] **Monitoring & Logging** - Override tracking and audit trails

### **Phase 4: Integration & Testing** 🧪
- [ ] **Comprehensive Testing** - Unit, integration, and system tests
- [ ] **Performance Testing** - Override performance benchmarks
- [ ] **Production Deployment** - Production-ready override system

---

This architecture provides a solid foundation for implementing production-ready package overrides in apt-ostree, maintaining compatibility with the rpm-ostree ecosystem while providing robust package replacement, validation, and management capabilities.
