//! Servo rendering engine backend (experimental)
//!
//! This module provides integration with the Servo rendering engine.
//! It is feature-gated and only available when the `servo-backend` feature is enabled.
//!
//! ## Status
//!
//! [WARNING] **EXPERIMENTAL** - This backend is under development and not ready for production use.
//!
//! ## Architecture
//!
//! ```text
//! ┌─────────────────────────────────────┐
//! │      ServoBackend (WebViewBackend)  │
//! └─────────────────────────────────────┘
//!                  ↓
//!     ┌────────────┴────────────┐
//!     ↓                         ↓
//! ┌─────────┐            ┌──────────┐
//! │  Servo  │            │  winit   │
//! │ Engine  │            │ Window   │
//! └─────────┘            └──────────┘
//!     ↓                         ↓
//! WebRender              Event Loop
//! Stylo (CSS)
//! SpiderMonkey (JS)
//! ```
//!
//! ## Features
//!
//! - [ ] Basic HTML rendering
//! - [ ] CSS support (Stylo)
//! - [ ] JavaScript execution (SpiderMonkey)
//! - [ ] IPC bridge (Rust ↔ JavaScript)
//! - [ ] Event loop integration
//! - [ ] Window embedding
//!
//! ## Usage
//!
//! ```toml
//! [dependencies]
//! auroraview = { version = "0.1", features = ["servo-backend"] }
//! ```
//!
//! ```python
//! from auroraview import NativeWebView
//!
//! # Use Servo backend (if available)
//! webview = NativeWebView.standalone(
//!     title="Servo Test",
//!     backend="servo",  # Specify Servo backend
//! )
//! ```

use std::sync::{Arc, Mutex};
use wry::WebView as WryWebView;

use super::super::config::WebViewConfig;
use super::super::event_loop::UserEvent;
use super::WebViewBackend;
use crate::ipc::{IpcHandler, MessageQueue};

/// Servo rendering engine backend
///
/// This backend uses the Servo rendering engine instead of the system WebView.
///
/// ## Advantages
///
/// - Full control over rendering pipeline
/// - High-performance parallel rendering (WebRender)
/// - Modern CSS engine (Stylo)
/// - Pure Rust implementation
///
/// ## Disadvantages
///
/// - Large binary size (~100MB+)
/// - Experimental and unstable
/// - Limited web compatibility
/// - Higher memory usage
pub struct ServoBackend {
    /// Servo instance (placeholder)
    ///
    /// TODO: Replace with actual Servo types when implementing
    _servo: (),

    /// Window handle (placeholder)
    ///
    /// TODO: Use winit::window::Window
    _window: (),

    /// Event loop (placeholder)
    ///
    /// TODO: Use winit::event_loop::EventLoop
    _event_loop: (),

    /// IPC handler
    ipc_handler: Arc<IpcHandler>,

    /// Message queue
    message_queue: Arc<MessageQueue>,

    /// Configuration
    config: WebViewConfig,
}

impl ServoBackend {
    /// Create a new Servo backend
    ///
    /// ## Implementation Notes
    ///
    /// This is a placeholder implementation. The actual implementation would:
    ///
    /// 1. Initialize Servo engine
    /// 2. Create winit window
    /// 3. Set up WebRender compositor
    /// 4. Configure Stylo CSS engine
    /// 5. Initialize SpiderMonkey JavaScript engine
    /// 6. Set up IPC bridge
    ///
    /// ## Example (Future)
    ///
    /// ```rust,ignore
    /// use servo::Servo;
    /// use winit::window::WindowBuilder;
    ///
    /// let window = WindowBuilder::new()
    ///     .with_title(&config.title)
    ///     .with_inner_size(winit::dpi::LogicalSize::new(config.width, config.height))
    ///     .build(&event_loop)?;
    ///
    /// let servo = Servo::new(ServoConfig {
    ///     url: config.url.clone(),
    ///     window: &window,
    ///     // ... other config
    /// })?;
    /// ```
    pub fn new(
        config: WebViewConfig,
        ipc_handler: Arc<IpcHandler>,
        message_queue: Arc<MessageQueue>,
    ) -> Result<Self, Box<dyn std::error::Error>> {
        tracing::warn!("[WARNING] Servo backend is experimental and not yet implemented");
        tracing::info!(" Configuration: {:?}", config);

        // TODO: Implement Servo initialization
        // For now, return an error
        Err("Servo backend is not yet implemented. Please use the native backend.".into())
    }
}

impl WebViewBackend for ServoBackend {
    fn create(
        config: WebViewConfig,
        ipc_handler: Arc<IpcHandler>,
        message_queue: Arc<MessageQueue>,
    ) -> Result<Self, Box<dyn std::error::Error>>
    where
        Self: Sized,
    {
        Self::new(config, ipc_handler, message_queue)
    }

    fn webview(&self) -> Arc<Mutex<WryWebView>> {
        // TODO: This is a compatibility shim
        // Servo doesn't use WryWebView, so we need to rethink this interface
        unimplemented!("Servo backend does not use WryWebView")
    }

    fn message_queue(&self) -> Arc<MessageQueue> {
        self.message_queue.clone()
    }

    fn window(&self) -> Option<&tao::window::Window> {
        // TODO: Return winit window (need to convert to tao::window::Window)
        None
    }

    fn event_loop(&mut self) -> Option<tao::event_loop::EventLoop<UserEvent>> {
        // TODO: Return winit event loop (need to convert to tao)
        None
    }

    fn process_events(&self) -> bool {
        // TODO: Process Servo events
        false
    }

    fn run_event_loop_blocking(&mut self) {
        // TODO: Run Servo event loop
        unimplemented!("Servo event loop not yet implemented")
    }

    fn load_url(&mut self, url: &str) -> Result<(), Box<dyn std::error::Error>> {
        tracing::info!("[DOCUMENT] Loading URL: {}", url);
        // TODO: Implement URL loading in Servo
        Err("Not yet implemented".into())
    }

    fn load_html(&mut self, html: &str) -> Result<(), Box<dyn std::error::Error>> {
        tracing::info!("[DOCUMENT] Loading HTML ({} bytes)", html.len());
        // TODO: Implement HTML loading in Servo
        Err("Not yet implemented".into())
    }

    fn eval_js(&mut self, script: &str) -> Result<(), Box<dyn std::error::Error>> {
        tracing::info!("[CONFIG] Evaluating JavaScript ({} bytes)", script.len());
        // TODO: Implement JavaScript execution in Servo
        Err("Not yet implemented".into())
    }

    fn emit(
        &mut self,
        event_name: &str,
        data: serde_json::Value,
    ) -> Result<(), Box<dyn std::error::Error>> {
        tracing::info!("[SEND] Emitting event: {}", event_name);
        // TODO: Implement event emission to JavaScript
        Err("Not yet implemented".into())
    }
}

/// Servo backend configuration
///
/// Additional configuration specific to Servo backend.
#[derive(Debug, Clone)]
pub struct ServoConfig {
    /// Enable WebRender debug overlay
    pub debug_overlay: bool,

    /// Enable Stylo parallel CSS processing
    pub parallel_css: bool,

    /// Maximum number of parallel layout threads
    pub layout_threads: usize,

    /// Enable WebGL support
    pub webgl: bool,

    /// Enable WebGPU support (experimental)
    pub webgpu: bool,
}

impl Default for ServoConfig {
    fn default() -> Self {
        Self {
            debug_overlay: false,
            parallel_css: true,
            layout_threads: num_cpus::get(),
            webgl: true,
            webgpu: false,
        }
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn test_servo_config_default() {
        let config = ServoConfig::default();
        assert!(config.parallel_css);
        assert!(config.webgl);
        assert!(!config.webgpu);
    }
}
