//! API middleware pipeline for cross-cutting concerns
//!
//! Middleware allows for composable handling of cross-cutting concerns
//! like logging, metrics, rate limiting, caching, etc.

use super::{error::ApiResult, session::SessionContext};
use std::future::Future;
use std::pin::Pin;
use std::sync::Arc;
use tracing::{debug, info};

/// Middleware trait for composable request handling
#[async_trait::async_trait]
pub trait ApiMiddleware: Send + Sync {
	/// Process a request through this middleware layer
	async fn process<F, Fut, T>(
		&self,
		session: &SessionContext,
		operation_name: &str,
		next: F,
	) -> ApiResult<T>
	where
		F: FnOnce() -> Fut + Send,
		Fut: Future<Output = ApiResult<T>> + Send,
		T: Send,
	{
		// Default implementation just calls next
		next().await
	}
}

/// Logging middleware - logs all API operations
pub struct LoggingMiddleware;

#[async_trait::async_trait]
impl ApiMiddleware for LoggingMiddleware {
	async fn process<F, Fut, T>(
		&self,
		session: &SessionContext,
		operation_name: &str,
		next: F,
	) -> ApiResult<T>
	where
		F: FnOnce() -> Fut + Send,
		Fut: Future<Output = ApiResult<T>> + Send,
		T: Send,
	{
		let start = std::time::Instant::now();

		info!(
			request_id = %session.request_metadata.request_id,
			operation = operation_name,
			device_id = %session.auth.device_id,
			library_id = ?session.current_library_id,
			"API operation starting"
		);

		let result = next().await;
		let duration = start.elapsed();

		match &result {
			Ok(_) => {
				info!(
					request_id = %session.request_metadata.request_id,
					operation = operation_name,
					duration_ms = duration.as_millis(),
					"API operation completed successfully"
				);
			}
			Err(e) => {
				debug!(
					request_id = %session.request_metadata.request_id,
					operation = operation_name,
					duration_ms = duration.as_millis(),
					error = %e,
					"API operation failed"
				);
			}
		}

		result
	}
}

/// Metrics middleware - tracks operation metrics
pub struct MetricsMiddleware {
	// Future: metrics collectors, counters, histograms
}

#[async_trait::async_trait]
impl ApiMiddleware for MetricsMiddleware {
	async fn process<F, Fut, T>(
		&self,
		session: &SessionContext,
		operation_name: &str,
		next: F,
	) -> ApiResult<T>
	where
		F: FnOnce() -> Fut + Send,
		Fut: Future<Output = ApiResult<T>> + Send,
		T: Send,
	{
		let start = std::time::Instant::now();
		let result = next().await;
		let duration = start.elapsed();

		// Future: Record metrics
		// self.record_operation_duration(operation_name, duration);
		// self.record_operation_result(operation_name, result.is_ok());

		debug!(
			operation = operation_name,
			duration_ms = duration.as_millis(),
			success = result.is_ok(),
			"Operation metrics recorded"
		);

		result
	}
}

/// Rate limiting middleware - prevents abuse
pub struct RateLimitMiddleware {
	// Future: rate limiters per device/user/operation
}

#[async_trait::async_trait]
impl ApiMiddleware for RateLimitMiddleware {
	async fn process<F, Fut, T>(
		&self,
		session: &SessionContext,
		operation_name: &str,
		next: F,
	) -> ApiResult<T>
	where
		F: FnOnce() -> Fut + Send,
		Fut: Future<Output = ApiResult<T>> + Send,
		T: Send,
	{
		// Future: Check rate limits
		// if self.is_rate_limited(&session.auth.device_id, operation_name).await {
		//     return Err(ApiError::RateLimitExceeded { retry_after_seconds: 60 });
		// }

		let result = next().await;

		// Future: Update rate limit counters
		// self.record_request(&session.auth.device_id, operation_name).await;

		result
	}
}

/// Middleware pipeline for composing multiple middleware layers
pub struct MiddlewarePipeline {
	// For now, use concrete types instead of trait objects
	// Future: Consider using an enum for known middleware types
	logging: Option<LoggingMiddleware>,
	metrics: Option<MetricsMiddleware>,
	rate_limit: Option<RateLimitMiddleware>,
}

impl MiddlewarePipeline {
	/// Create a new middleware pipeline
	pub fn new() -> Self {
		Self {
			logging: None,
			metrics: None,
			rate_limit: None,
		}
	}

	/// Add logging middleware
	pub fn with_logging(mut self) -> Self {
		self.logging = Some(LoggingMiddleware);
		self
	}

	/// Add metrics middleware
	pub fn with_metrics(mut self) -> Self {
		self.metrics = Some(MetricsMiddleware {});
		self
	}

	/// Add rate limiting middleware
	pub fn with_rate_limiting(mut self) -> Self {
		self.rate_limit = Some(RateLimitMiddleware {});
		self
	}

	/// Execute a request through the middleware pipeline
	pub async fn execute<F, Fut, T>(
		&self,
		session: &SessionContext,
		operation_name: &str,
		handler: F,
	) -> ApiResult<T>
	where
		F: FnOnce() -> Fut + Send,
		Fut: Future<Output = ApiResult<T>> + Send,
		T: Send,
	{
		// For now, just execute the handler directly
		// Future: Chain middleware layers properly
		handler().await
	}

	/// Create the default middleware pipeline
	pub fn default_pipeline() -> Self {
		Self::new()
			.with_logging()
			.with_metrics()
			.with_rate_limiting()
	}
}
