updating doc

docs/API.md

@@ -13,6 +13,8 @@ who want to integrate with, extend, or understand the facial authentication syst
 - [Extension Points](#extension-points)
 - [Configuration](#configuration)
 - [IPC Protocol](#ipc-protocol)
+- [D-Bus API](#d-bus-api)
+- [Error Handling](#error-handling)
 
 ## Architecture Overview
 
@@ -416,6 +418,116 @@ The daemon communicates via Unix socket using JSON messages.
 }
 ```
 
+## D-Bus API
+
+The daemon exposes a D-Bus interface for desktop integration.
+
+### Service Information
+
+| Property | Value |
+|----------|-------|
+| Bus | System bus |
+| Service Name | `org.linuxhello.Daemon` |
+| Object Path | `/org/linuxhello/Manager` |
+| Interface | `org.linuxhello.Manager` |
+
+### Methods
+
+```xml
+<!-- Authenticate a user -->
+<method name="Authenticate">
+  <arg name="user" type="s" direction="in"/>
+  <arg name="success" type="b" direction="out"/>
+  <arg name="confidence" type="d" direction="out"/>
+  <arg name="message" type="s" direction="out"/>
+</method>
+
+<!-- Start enrollment -->
+<method name="EnrollStart">
+  <arg name="user" type="s" direction="in"/>
+  <arg name="label" type="s" direction="in"/>
+  <arg name="frame_count" type="u" direction="in"/>
+  <arg name="success" type="b" direction="out"/>
+</method>
+
+<!-- Cancel enrollment -->
+<method name="EnrollCancel">
+  <arg name="success" type="b" direction="out"/>
+</method>
+
+<!-- List templates for user -->
+<method name="ListTemplates">
+  <arg name="user" type="s" direction="in"/>
+  <arg name="templates" type="as" direction="out"/>
+</method>
+
+<!-- Remove a template -->
+<method name="RemoveTemplate">
+  <arg name="user" type="s" direction="in"/>
+  <arg name="label" type="s" direction="in"/>
+  <arg name="success" type="b" direction="out"/>
+</method>
+
+<!-- Get system status -->
+<method name="GetSystemStatus">
+  <arg name="camera_available" type="b" direction="out"/>
+  <arg name="tpm_available" type="b" direction="out"/>
+  <arg name="anti_spoofing_enabled" type="b" direction="out"/>
+  <arg name="enrolled_count" type="u" direction="out"/>
+</method>
+```
+
+### Properties
+
+```xml
+<property name="Version" type="s" access="read"/>
+<property name="CameraAvailable" type="b" access="read"/>
+<property name="TpmAvailable" type="b" access="read"/>
+<property name="AntiSpoofingEnabled" type="b" access="read"/>
+```
+
+### Signals
+
+```xml
+<!-- Enrollment progress -->
+<signal name="EnrollmentProgress">
+  <arg name="frames_captured" type="u"/>
+  <arg name="frames_total" type="u"/>
+  <arg name="status" type="s"/>
+</signal>
+
+<!-- Enrollment complete -->
+<signal name="EnrollmentComplete">
+  <arg name="success" type="b"/>
+  <arg name="message" type="s"/>
+</signal>
+```
+
+### D-Bus Client Example (Rust with zbus)
+
+```rust
+use zbus::{Connection, proxy};
+
+#[proxy(
+    interface = "org.linuxhello.Manager",
+    default_service = "org.linuxhello.Daemon",
+    default_path = "/org/linuxhello/Manager"
+)]
+trait LinuxHelloManager {
+    async fn authenticate(&self, user: &str) -> zbus::Result<(bool, f64, String)>;
+    async fn list_templates(&self, user: &str) -> zbus::Result<Vec<String>>;
+}
+
+async fn authenticate_user() -> zbus::Result<()> {
+    let connection = Connection::system().await?;
+    let proxy = LinuxHelloManagerProxy::new(&connection).await?;
+
+    let (success, confidence, message) = proxy.authenticate("alice").await?;
+    println!("Auth: {} ({}): {}", success, confidence, message);
+    Ok(())
+}
+```
+
 ## Error Handling
 
 All operations return `Result<T, Error>` where `Error` is defined in `linux_hello_common::Error`: