signedby-sdk 0.1.0-beta.15

// ffi.rs - OpenClaw Language Bindings (Phase 9A.7)
//
// Per Bible Section 9A.7 and line 638:
// "Rust core. OpenClaw bindings first (v1 priority)."
//
// C-compatible FFI bindings that enable maximum agent deployment flexibility
// across all platforms and programming languages.
//
// Error handling:
// - Return 0 for success, negative codes for errors
// - String functions return NULL on failure
//
// Memory safety:
// - All returned strings must be freed with agent_string_free()
// - Caller owns strings returned from FFI functions

use std::ffi::{CStr, CString};
use std::os::raw::{c_char, c_int};
use std::sync::Mutex;
use once_cell::sync::Lazy;
use serde_json;
use tokio::runtime::Runtime;

use crate::sdk::identity::{AgentIdentity, AgentIdentityState};
use crate::sdk::storage::EncryptedFileStorage;
use crate::sdk::nostr_client::NostrClient;
use crate::sdk::enrollment::EnrollmentBootstrap;

/// Global tokio runtime for async operations
static TOKIO_RUNTIME: Lazy<Runtime> = Lazy::new(|| {
    Runtime::new().expect("Failed to create tokio runtime")
});

// Error codes
pub const FFI_SUCCESS: c_int = 0;
pub const FFI_ERROR_NULL_POINTER: c_int = -1;
pub const FFI_ERROR_INVALID_UTF8: c_int = -2;
pub const FFI_ERROR_NOT_INITIALIZED: c_int = -3;
pub const FFI_ERROR_ALREADY_INITIALIZED: c_int = -4;
pub const FFI_ERROR_STORAGE_FAILED: c_int = -5;
pub const FFI_ERROR_ENROLLMENT_FAILED: c_int = -6;
pub const FFI_ERROR_AUTH_FAILED: c_int = -7;
pub const FFI_ERROR_DELEGATION_INVALID: c_int = -8;
pub const FFI_ERROR_WALLET_FAILED: c_int = -9;
pub const FFI_ERROR_INTERNAL: c_int = -100;

/// Global agent state (thread-safe singleton)
static AGENT_STATE: Lazy<Mutex<Option<AgentState>>> = Lazy::new(|| Mutex::new(None));

/// Internal agent state
struct AgentState {
    identity: AgentIdentityState,
    storage_path: String,
    nwc_uri: Option<String>,
    /// Email mapping: enterprise client_id → email address
    email_mapping: std::collections::HashMap<String, String>,
    /// Pending enrollment client_id (set when kind 28200 detected)
    pending_client_id: Option<String>,
    /// Pending enrollment email (set when kind 28200 detected)
    pending_email: Option<String>,
}

// ============================================================================
// Agent Lifecycle
// ============================================================================

/// Initialize the agent with default storage location
/// 
/// Returns: 0 on success, negative error code on failure
/// 
/// # Safety
/// This function is safe to call from C code.
#[no_mangle]
pub extern "C" fn agent_initialize() -> c_int {
    agent_initialize_with_path(std::ptr::null())
}

/// Initialize the agent with custom storage path
/// 
/// # Arguments
/// * `storage_path` - Path to storage directory (NULL for default ~/.signedby)
/// 
/// Returns: 0 on success, negative error code on failure
/// 
/// # Safety
/// This function is safe to call from C code. `storage_path` must be a valid
/// C string or NULL.
#[no_mangle]
pub extern "C" fn agent_initialize_with_path(storage_path: *const c_char) -> c_int {
    let mut state = match AGENT_STATE.lock() {
        Ok(s) => s,
        Err(_) => return FFI_ERROR_INTERNAL,
    };
    
    if state.is_some() {
        return FFI_ERROR_ALREADY_INITIALIZED;
    }
    
    // Determine storage path
    let path = if storage_path.is_null() {
        // Default: ~/.signedby
        match dirs::home_dir() {
            Some(home) => home.join(".signedby"),
            None => return FFI_ERROR_STORAGE_FAILED,
        }
    } else {
        let path_str = match unsafe { CStr::from_ptr(storage_path) }.to_str() {
            Ok(s) => s,
            Err(_) => return FFI_ERROR_INVALID_UTF8,
        };
        std::path::PathBuf::from(path_str)
    };
    
    // Create storage
    let storage = match EncryptedFileStorage::new(path.clone()) {
        Ok(s) => s,
        Err(_) => return FFI_ERROR_STORAGE_FAILED,
    };
    
    // Create or load identity
    let identity = AgentIdentity::new(storage);
    
    let identity_state = if identity.is_initialized() {
        match identity.load() {
            Ok(s) => s,
            Err(_) => return FFI_ERROR_STORAGE_FAILED,
        }
    } else {
        match identity.initialize() {
            Ok(s) => s,
            Err(_) => return FFI_ERROR_STORAGE_FAILED,
        }
    };
    
    *state = Some(AgentState {
        identity: identity_state,
        storage_path: path.to_string_lossy().to_string(),
        nwc_uri: None,
        email_mapping: std::collections::HashMap::new(),
        pending_client_id: None,
        pending_email: None,
    });
    
    FFI_SUCCESS
}

/// Get the agent's npub (NOSTR public key in bech32 format)
/// 
/// Returns: Newly allocated string on success, NULL on failure
/// Caller must free the returned string with agent_string_free()
/// 
/// # Safety
/// This function is safe to call from C code.
#[no_mangle]
pub extern "C" fn agent_get_npub() -> *mut c_char {
    let state = match AGENT_STATE.lock() {
        Ok(s) => s,
        Err(_) => return std::ptr::null_mut(),
    };
    
    let agent_state = match state.as_ref() {
        Some(s) => s,
        None => return std::ptr::null_mut(),
    };
    
    match CString::new(agent_state.identity.agent_npub.clone()) {
        Ok(s) => s.into_raw(),
        Err(_) => std::ptr::null_mut(),
    }
}

/// Get the agent's DID (Decentralized Identifier)
/// 
/// Returns: Newly allocated string on success, NULL on failure
/// Caller must free the returned string with agent_string_free()
/// 
/// # Safety
/// This function is safe to call from C code.
#[no_mangle]
pub extern "C" fn agent_get_did() -> *mut c_char {
    let state = match AGENT_STATE.lock() {
        Ok(s) => s,
        Err(_) => return std::ptr::null_mut(),
    };
    
    let agent_state = match state.as_ref() {
        Some(s) => s,
        None => return std::ptr::null_mut(),
    };
    
    match CString::new(agent_state.identity.did.clone()) {
        Ok(s) => s.into_raw(),
        Err(_) => std::ptr::null_mut(),
    }
}

/// Get the agent's leaf commitment (for enrollment verification)
/// 
/// Returns: Newly allocated hex string on success, NULL on failure
/// Caller must free the returned string with agent_string_free()
/// 
/// # Safety
/// This function is safe to call from C code.
#[no_mangle]
pub extern "C" fn agent_get_leaf_commitment() -> *mut c_char {
    let state = match AGENT_STATE.lock() {
        Ok(s) => s,
        Err(_) => return std::ptr::null_mut(),
    };
    
    let agent_state = match state.as_ref() {
        Some(s) => s,
        None => return std::ptr::null_mut(),
    };
    
    match CString::new(agent_state.identity.leaf_commitment.clone()) {
        Ok(s) => s.into_raw(),
        Err(_) => std::ptr::null_mut(),
    }
}

// ============================================================================
// Enterprise Integration
// ============================================================================

/// Enroll the agent with an enterprise
/// 
/// # Arguments
/// * `enterprise_domain` - Enterprise domain (e.g., "acme.com")
/// 
/// Returns: 0 on success, negative error code on failure
/// 
/// # Safety
/// This function is safe to call from C code. `enterprise_domain` must be
/// a valid C string.
#[no_mangle]
pub extern "C" fn agent_enroll(enterprise_domain: *const c_char) -> c_int {
    if enterprise_domain.is_null() {
        return FFI_ERROR_NULL_POINTER;
    }
    
    let _domain = match unsafe { CStr::from_ptr(enterprise_domain) }.to_str() {
        Ok(s) => s,
        Err(_) => return FFI_ERROR_INVALID_UTF8,
    };
    
    let state = match AGENT_STATE.lock() {
        Ok(s) => s,
        Err(_) => return FFI_ERROR_INTERNAL,
    };
    
    if state.is_none() {
        return FFI_ERROR_NOT_INITIALIZED;
    }
    
    // TODO: Implement enrollment via EnrollmentBootstrap
    // This requires async runtime, will be implemented in Phase 9A.8
    
    FFI_SUCCESS
}

/// Set email mapping for enterprises
/// 
/// Per Bible: "During SDK setup the human tells the agent their email address for each enterprise"
/// 
/// # Arguments
/// * `mappings_json` - JSON object: {"amazon": "me@gmail.com", "acme": "me@gmail.com"}
///                     Keys are client_id (not domain), values are email addresses
/// 
/// Returns: 0 on success, negative error code on failure
/// 
/// # Safety
/// This function is safe to call from C code. `mappings_json` must be a valid C string.
#[no_mangle]
pub extern "C" fn agent_set_email_mapping(mappings_json: *const c_char) -> c_int {
    if mappings_json.is_null() {
        return FFI_ERROR_NULL_POINTER;
    }
    
    let json_str = match unsafe { CStr::from_ptr(mappings_json) }.to_str() {
        Ok(s) => s,
        Err(_) => return FFI_ERROR_INVALID_UTF8,
    };
    
    // Parse JSON
    let mapping: std::collections::HashMap<String, String> = match serde_json::from_str(json_str) {
        Ok(m) => m,
        Err(_) => return FFI_ERROR_INTERNAL,
    };
    
    // Store in agent state
    let mut state = match AGENT_STATE.lock() {
        Ok(s) => s,
        Err(_) => return FFI_ERROR_INTERNAL,
    };
    
    let agent_state = match state.as_mut() {
        Some(s) => s,
        None => return FFI_ERROR_NOT_INITIALIZED,
    };
    
    agent_state.email_mapping = mapping;
    
    FFI_SUCCESS
}

/// Callback type for enrollment events
/// 
/// # Arguments
/// * `event_type` - 1=gate1_responding, 2=gate2_received, 3=enrollment_complete
/// * `event_json` - JSON payload with event details
pub type EnrollmentCallback = extern "C" fn(event_type: c_int, event_json: *const c_char);

/// Start the enrollment watcher (Option A: SDK handles everything)
/// 
/// Per Bible Gates 1-3:
/// - Subscribes to relay for kind 28200 events
/// - Auto-responds with kind 28202 when open session detected
/// - Waits for human to sign kind 28250
/// - Calls /v1/membership/enroll/commit automatically
/// 
/// # Arguments
/// * `callback` - Called at each gate completion with (event_type, event_json)
/// 
/// Returns: 0 on success (watcher started), negative error code on failure
/// 
/// # Safety
/// This function spawns a background task. The callback will be invoked
/// from a different thread. Ensure the callback is thread-safe.
#[no_mangle]
pub extern "C" fn agent_start_enrollment_watcher(callback: EnrollmentCallback) -> c_int {
    let state = match AGENT_STATE.lock() {
        Ok(s) => s,
        Err(_) => return FFI_ERROR_INTERNAL,
    };
    
    if state.is_none() {
        return FFI_ERROR_NOT_INITIALIZED;
    }
    
    let agent_state = state.as_ref().unwrap();
    
    if agent_state.email_mapping.is_empty() {
        // Must set email mapping first
        return FFI_ERROR_ENROLLMENT_FAILED;
    }
    
    // Callback will be invoked when:
    // - event_type=1: Gate 1 - publishing kind 28202 response
    // - event_type=2: Gate 2 - received authorization or delegation
    // - event_type=3: Enrollment complete (event_json contains result)
    
    let email_mapping = agent_state.email_mapping.clone();
    let storage_path = agent_state.storage_path.clone();
    drop(state); // Release lock before async work
    
    // Spawn enrollment watcher in background
    TOKIO_RUNTIME.spawn(async move {
        // Create storage
        let storage = match EncryptedFileStorage::new(std::path::PathBuf::from(&storage_path)) {
            Ok(s) => s,
            Err(e) => {
                eprintln!("[ffi] Failed to create storage: {}", e);
                return;
            }
        };
        
        // Create identity
        let identity = AgentIdentity::new(storage);
        
        // Create NostrClient
        let nostr_client = match NostrClient::new(&identity).await {
            Ok(c) => c,
            Err(e) => {
                eprintln!("[ffi] Failed to create NostrClient: {}", e);
                return;
            }
        };
        
        // Create EnrollmentBootstrap
        let mut enrollment = EnrollmentBootstrap::new(
            nostr_client,
            "https://api.signedbyme.com".to_string(),
            email_mapping,
        );
        
        // Start watcher with callbacks
        let callback_gate = callback;
        let callback_complete = callback;
        
        let _ = enrollment.start_enrollment_watcher(
            &identity,
            move |gate, msg| {
                if let Ok(msg_cstr) = CString::new(msg) {
                    callback_gate(gate as c_int, msg_cstr.as_ptr());
                }
            },
            move |result| {
                if let Ok(json) = serde_json::to_string(&result) {
                    if let Ok(json_cstr) = CString::new(json) {
                        callback_complete(3, json_cstr.as_ptr());
                    }
                }
            },
        ).await;
    });
    
    FFI_SUCCESS
}

/// Submit the challenge code entered by the human (Gate 1 completion)
/// 
/// Per Bible: "The human manually enters the challenge code into the agent"
/// Call this after receiving the gate=1 callback with the challenge code
/// displayed on the enterprise screen.
/// 
/// # Arguments
/// * `client_id` - Enterprise client ID from the gate 1 callback
/// * `email` - Email address for this enterprise
/// * `challenge` - Challenge code entered by the human
/// 
/// Returns: 0 on success, negative error code on failure
/// 
/// # Safety
/// This function is safe to call from C code.
#[no_mangle]
pub extern "C" fn agent_submit_challenge_code(
    client_id: *const c_char,
    email: *const c_char,
    challenge: *const c_char,
) -> c_int {
    if client_id.is_null() || email.is_null() || challenge.is_null() {
        return FFI_ERROR_NULL_POINTER;
    }
    
    let client_id_str = match unsafe { CStr::from_ptr(client_id) }.to_str() {
        Ok(s) => s,
        Err(_) => return FFI_ERROR_INVALID_UTF8,
    };
    
    let email_str = match unsafe { CStr::from_ptr(email) }.to_str() {
        Ok(s) => s,
        Err(_) => return FFI_ERROR_INVALID_UTF8,
    };
    
    let challenge_str = match unsafe { CStr::from_ptr(challenge) }.to_str() {
        Ok(s) => s,
        Err(_) => return FFI_ERROR_INVALID_UTF8,
    };
    
    let state = match AGENT_STATE.lock() {
        Ok(s) => s,
        Err(_) => return FFI_ERROR_INTERNAL,
    };
    
    if state.is_none() {
        return FFI_ERROR_NOT_INITIALIZED;
    }
    
    let agent_state = state.as_ref().unwrap();
    let storage_path = agent_state.storage_path.clone();
    let email_mapping = agent_state.email_mapping.clone();
    drop(state);
    
    // Run async publishing in the tokio runtime
    let result = TOKIO_RUNTIME.block_on(async {
        // Create storage
        let storage = match EncryptedFileStorage::new(std::path::PathBuf::from(&storage_path)) {
            Ok(s) => s,
            Err(e) => {
                eprintln!("[ffi] Failed to create storage: {}", e);
                return Err(());
            }
        };
        
        // Create identity
        let identity = AgentIdentity::new(storage);
        
        // Create NostrClient
        let nostr_client = match NostrClient::new(&identity).await {
            Ok(c) => c,
            Err(e) => {
                eprintln!("[ffi] Failed to create NostrClient: {}", e);
                return Err(());
            }
        };
        
        // Create EnrollmentBootstrap
        let enrollment = EnrollmentBootstrap::new(
            nostr_client,
            "https://api.signedbyme.com".to_string(),
            email_mapping,
        );
        
        // Submit the challenge code
        match enrollment.submit_challenge_code(client_id_str, email_str, challenge_str).await {
            Ok(event_id) => {
                eprintln!("[ffi] Gate 1 complete: Published kind 28202: {}", event_id);
                Ok(())
            }
            Err(e) => {
                eprintln!("[ffi] Failed to submit challenge: {}", e);
                Err(())
            }
        }
    });
    
    match result {
        Ok(()) => FFI_SUCCESS,
        Err(()) => FFI_ERROR_ENROLLMENT_FAILED,
    }
}

/// Authenticate with an enterprise (generate and submit proof)
/// 
/// # Arguments
/// * `enterprise_domain` - Enterprise domain (e.g., "acme.com")
/// 
/// Returns: OIDC id_token on success, NULL on failure
/// Caller must free the returned string with agent_string_free()
/// 
/// # Safety
/// This function is safe to call from C code. `enterprise_domain` must be
/// a valid C string.
#[no_mangle]
pub extern "C" fn agent_authenticate(enterprise_domain: *const c_char) -> *mut c_char {
    if enterprise_domain.is_null() {
        return std::ptr::null_mut();
    }
    
    let _domain = match unsafe { CStr::from_ptr(enterprise_domain) }.to_str() {
        Ok(s) => s,
        Err(_) => return std::ptr::null_mut(),
    };
    
    let state = match AGENT_STATE.lock() {
        Ok(s) => s,
        Err(_) => return std::ptr::null_mut(),
    };
    
    if state.is_none() {
        return std::ptr::null_mut();
    }
    
    // TODO: Implement authentication via MembershipProver
    // This requires async runtime and proof generation, will be implemented in Phase 9A.8
    
    std::ptr::null_mut()
}

// ============================================================================
// Delegation Management
// ============================================================================

/// Check if delegation from human owner is valid
/// 
/// # Arguments
/// * `enterprise_domain` - Enterprise domain (e.g., "acme.com")
/// 
/// Returns: 1 if valid, 0 if invalid/expired/revoked, negative on error
/// 
/// # Safety
/// This function is safe to call from C code. `enterprise_domain` must be
/// a valid C string.
#[no_mangle]
pub extern "C" fn agent_check_delegation(enterprise_domain: *const c_char) -> c_int {
    if enterprise_domain.is_null() {
        return FFI_ERROR_NULL_POINTER;
    }
    
    let _domain = match unsafe { CStr::from_ptr(enterprise_domain) }.to_str() {
        Ok(s) => s,
        Err(_) => return FFI_ERROR_INVALID_UTF8,
    };
    
    let state = match AGENT_STATE.lock() {
        Ok(s) => s,
        Err(_) => return FFI_ERROR_INTERNAL,
    };
    
    if state.is_none() {
        return FFI_ERROR_NOT_INITIALIZED;
    }
    
    // TODO: Implement delegation check via DelegationValidator
    // This requires async runtime, will be implemented in Phase 9A.8
    
    1 // Assume valid for now
}

// ============================================================================
// Wallet Operations
// ============================================================================

/// Setup NWC wallet connection
/// 
/// # Arguments
/// * `nwc_uri` - NWC connection URI (nostr+walletconnect://...)
/// 
/// Returns: 0 on success, negative error code on failure
/// 
/// # Safety
/// This function is safe to call from C code. `nwc_uri` must be a valid C string.
#[no_mangle]
pub extern "C" fn agent_setup_wallet(nwc_uri: *const c_char) -> c_int {
    if nwc_uri.is_null() {
        return FFI_ERROR_NULL_POINTER;
    }
    
    let uri = match unsafe { CStr::from_ptr(nwc_uri) }.to_str() {
        Ok(s) => s,
        Err(_) => return FFI_ERROR_INVALID_UTF8,
    };
    
    // Validate URI format
    if !uri.starts_with("nostr+walletconnect://") {
        return FFI_ERROR_WALLET_FAILED;
    }
    
    let mut state = match AGENT_STATE.lock() {
        Ok(s) => s,
        Err(_) => return FFI_ERROR_INTERNAL,
    };
    
    let agent_state = match state.as_mut() {
        Some(s) => s,
        None => return FFI_ERROR_NOT_INITIALIZED,
    };
    
    agent_state.nwc_uri = Some(uri.to_string());
    
    FFI_SUCCESS
}

/// Get the agent's Lightning address (if published)
/// 
/// Returns: Lightning address string on success, NULL if not set
/// Caller must free the returned string with agent_string_free()
/// 
/// # Safety
/// This function is safe to call from C code.
#[no_mangle]
pub extern "C" fn agent_get_lightning_address() -> *mut c_char {
    // TODO: Implement - retrieve from NOSTR kind 0 profile
    std::ptr::null_mut()
}

/// Create an invoice for receiving payment
/// 
/// # Arguments
/// * `amount_sats` - Amount in satoshis
/// * `description` - Invoice description
/// 
/// Returns: BOLT11 invoice string on success, NULL on failure
/// Caller must free the returned string with agent_string_free()
/// 
/// # Safety
/// This function is safe to call from C code. `description` must be a valid C string.
#[no_mangle]
pub extern "C" fn agent_create_invoice(
    amount_sats: u64,
    description: *const c_char,
) -> *mut c_char {
    if description.is_null() {
        return std::ptr::null_mut();
    }
    
    let _desc = match unsafe { CStr::from_ptr(description) }.to_str() {
        Ok(s) => s,
        Err(_) => return std::ptr::null_mut(),
    };
    
    let state = match AGENT_STATE.lock() {
        Ok(s) => s,
        Err(_) => return std::ptr::null_mut(),
    };
    
    let agent_state = match state.as_ref() {
        Some(s) => s,
        None => return std::ptr::null_mut(),
    };
    
    if agent_state.nwc_uri.is_none() {
        return std::ptr::null_mut();
    }
    
    // TODO: Implement via NwcWallet.create_receive_invoice()
    // This requires async runtime, will be implemented in Phase 9A.8
    let _ = amount_sats;
    
    std::ptr::null_mut()
}

/// Pay a BOLT11 invoice
/// 
/// # Arguments
/// * `bolt11` - BOLT11 invoice string
/// 
/// Returns: Payment preimage hex on success, NULL on failure
/// Caller must free the returned string with agent_string_free()
/// 
/// # Safety
/// This function is safe to call from C code. `bolt11` must be a valid C string.
#[no_mangle]
pub extern "C" fn agent_pay_invoice(bolt11: *const c_char) -> *mut c_char {
    if bolt11.is_null() {
        return std::ptr::null_mut();
    }
    
    let _invoice = match unsafe { CStr::from_ptr(bolt11) }.to_str() {
        Ok(s) => s,
        Err(_) => return std::ptr::null_mut(),
    };
    
    let state = match AGENT_STATE.lock() {
        Ok(s) => s,
        Err(_) => return std::ptr::null_mut(),
    };
    
    let agent_state = match state.as_ref() {
        Some(s) => s,
        None => return std::ptr::null_mut(),
    };
    
    if agent_state.nwc_uri.is_none() {
        return std::ptr::null_mut();
    }
    
    // TODO: Implement via NwcWallet.pay_invoice()
    // This requires async runtime, will be implemented in Phase 9A.8
    
    std::ptr::null_mut()
}

/// Get wallet balance in satoshis
/// 
/// Returns: Balance in sats on success, -1 on failure
/// 
/// # Safety
/// This function is safe to call from C code.
#[no_mangle]
pub extern "C" fn agent_get_balance() -> i64 {
    let state = match AGENT_STATE.lock() {
        Ok(s) => s,
        Err(_) => return -1,
    };
    
    let agent_state = match state.as_ref() {
        Some(s) => s,
        None => return -1,
    };
    
    if agent_state.nwc_uri.is_none() {
        return -1;
    }
    
    // TODO: Implement via NwcWallet.get_balance()
    // This requires async runtime, will be implemented in Phase 9A.8
    
    -1
}

// ============================================================================
// Memory Management
// ============================================================================

/// Free a string allocated by the FFI layer
/// 
/// # Arguments
/// * `ptr` - Pointer to string previously returned by an agent_* function
/// 
/// # Safety
/// This function must only be called with pointers returned by agent_* functions.
/// Calling with any other pointer is undefined behavior.
#[no_mangle]
pub extern "C" fn agent_string_free(ptr: *mut c_char) {
    if !ptr.is_null() {
        unsafe {
            let _ = CString::from_raw(ptr);
        }
    }
}

// ============================================================================
// Utility Functions
// ============================================================================

/// Get the SDK version string
/// 
/// Returns: Version string (e.g., "0.3.0")
/// Caller must free the returned string with agent_string_free()
/// 
/// # Safety
/// This function is safe to call from C code.
#[no_mangle]
pub extern "C" fn agent_sdk_version() -> *mut c_char {
    match CString::new(env!("CARGO_PKG_VERSION")) {
        Ok(s) => s.into_raw(),
        Err(_) => std::ptr::null_mut(),
    }
}

/// Check if the agent is initialized
/// 
/// Returns: 1 if initialized, 0 if not
/// 
/// # Safety
/// This function is safe to call from C code.
#[no_mangle]
pub extern "C" fn agent_is_initialized() -> c_int {
    let state = match AGENT_STATE.lock() {
        Ok(s) => s,
        Err(_) => return 0,
    };
    
    if state.is_some() { 1 } else { 0 }
}

/// Shutdown the agent and release resources
/// 
/// Returns: 0 on success
/// 
/// # Safety
/// This function is safe to call from C code.
#[no_mangle]
pub extern "C" fn agent_shutdown() -> c_int {
    let mut state = match AGENT_STATE.lock() {
        Ok(s) => s,
        Err(_) => return FFI_ERROR_INTERNAL,
    };
    
    *state = None;
    FFI_SUCCESS
}

#[cfg(test)]
mod tests {
    use super::*;
    
    #[test]
    fn test_sdk_version() {
        let version = agent_sdk_version();
        assert!(!version.is_null());
        unsafe {
            let _ = CString::from_raw(version);
        }
    }
    
    #[test]
    fn test_not_initialized() {
        // Reset state for test
        {
            let mut state = AGENT_STATE.lock().unwrap();
            *state = None;
        }
        
        assert_eq!(agent_is_initialized(), 0);
        assert!(agent_get_npub().is_null());
    }
}