//! Runner trait abstraction for job processing

use crate::{Job, JobStatus, Client};
use log::{error, info};
use redis::AsyncCommands;

use std::sync::Arc;
use std::time::Duration;
use tokio::sync::mpsc;
use tokio::task::JoinHandle;

use crate::{initialize_redis_connection, BLPOP_TIMEOUT_SECONDS};

/// Configuration for runner instances
#[derive(Debug, Clone)]
pub struct RunnerConfig {
    pub runner_id: String,
    pub db_path: String,
    pub redis_url: String,
    pub default_timeout: Option<Duration>, // Only used by async runners
}

impl RunnerConfig {
    /// Create a new runner configuration
    pub fn new(
        runner_id: String,
        db_path: String,
        redis_url: String,
    ) -> Self {
        Self {
            runner_id,
            db_path,
            redis_url,
            default_timeout: None,
        }
    }

    /// Set default timeout for async runners
    pub fn with_default_timeout(mut self, timeout: Duration) -> Self {
        self.default_timeout = Some(timeout);
        self
    }
}

/// Trait for job runners
pub trait Runner: Send + Sync + 'static {
    /// Process a single job and return the result
    fn process_job(&self, job: Job) -> Result<String, Box<dyn std::error::Error + Send + Sync>>;
    
    /// Get runner ID
    fn runner_id(&self) -> &str;
    
    /// Get Redis URL
    fn redis_url(&self) -> &str;

    /// Spawn the runner loop
    fn spawn(
        self: Arc<Self>,
        mut shutdown_rx: mpsc::Receiver<()>,
    ) -> JoinHandle<Result<(), Box<dyn std::error::Error + Send + Sync>>> 
    where 
        Self: Sized 
    {
        tokio::spawn(async move {
            let runner_id = self.runner_id();
            let redis_url = self.redis_url();
            
            // Create client to get the proper queue key
            let client = Client::builder()
                .redis_url(redis_url)
                .build()
                .await
                .map_err(|e| format!("Failed to create client: {}", e))?;
            
            let queue_key = client.runner_key(runner_id);
            info!(
                "Runner '{}' starting. Connecting to Redis at {}. Listening on queue: {}",
                runner_id,
                redis_url,
                queue_key
            );

            let mut redis_conn = initialize_redis_connection(runner_id, redis_url).await?;

            // Main runner loop: poll Redis queue for jobs and process them
            // Exits on shutdown signal or Redis error
            loop {
                let blpop_keys = vec![queue_key.clone()];
                tokio::select! {
                    // Listen for shutdown signal
                    _ = shutdown_rx.recv() => {
                        info!("Runner '{}': Shutdown signal received", runner_id);
                        break;
                    }
                    // Listen for tasks from Redis
                    blpop_result = redis_conn.blpop(&blpop_keys, BLPOP_TIMEOUT_SECONDS as f64) => {
                        let response: Option<(String, String)> = match blpop_result {
                            Ok(resp) => resp,
                            Err(e) => {
                                error!("Runner '{}': Redis BLPOP error: {}", runner_id, e);
                                return Err(Box::new(e) as Box<dyn std::error::Error + Send + Sync>);
                            }
                        };

                        if let Some((_queue_name_recv, job_id)) = response {
                            info!("Runner '{}' received job: {}", runner_id, job_id);
                            
                            // Load and process job
                            match client.load_job_from_redis(&job_id).await {
                                Ok(job) => {
                                    if job.payload.trim() == "ping" {
                                        handle_ping_job(&client, runner_id, &job_id).await;
                                    } else {
                                        process_regular_job(&*self, &client, runner_id, &job_id, job).await;
                                    }
                                }
                                Err(e) => {
                                    error!("Runner '{}': Failed to load job '{}': {}", runner_id, job_id, e);
                                }
                            }
                        }
                    }
                }
            }

            info!("Runner '{}' has shut down", runner_id);
            Ok(())
        })
    }
}

/// Handle ping job - responds with "pong"
async fn handle_ping_job(client: &Client, runner_id: &str, job_id: &str) {
    info!("Runner '{}': Received ping job '{}'", runner_id, job_id);
    
    if let Err(e) = client.set_job_status(job_id, JobStatus::Started).await {
        error!("Runner '{}': Failed to set ping job '{}' status to Started: {}", runner_id, job_id, e);
    }
    
    if let Err(e) = client.set_result(job_id, "pong").await {
        error!("Runner '{}': Failed to set ping job '{}' result: {}", runner_id, job_id, e);
    }
    
    if let Err(e) = client.set_job_status(job_id, JobStatus::Finished).await {
        error!("Runner '{}': Failed to set ping job '{}' status to Finished: {}", runner_id, job_id, e);
    }
    
    info!("Runner '{}': Ping job '{}' completed", runner_id, job_id);
}

/// Process regular job - handles job execution and status updates
async fn process_regular_job(
    runner: &dyn Runner,
    client: &Client,
    runner_id: &str,
    job_id: &str,
    job: Job,
) {
    if let Err(e) = client.set_job_status(job_id, JobStatus::Started).await {
        error!("Runner '{}': Failed to set job '{}' status to Started: {}", runner_id, job_id, e);
    }
    
    match runner.process_job(job) {
        Ok(result) => {
            if let Err(e) = client.set_result(job_id, &result).await {
                error!("Runner '{}': Failed to set job '{}' result: {}", runner_id, job_id, e);
            }
            
            if let Err(e) = client.set_job_status(job_id, JobStatus::Finished).await {
                error!("Runner '{}': Failed to set job '{}' status to Finished: {}", runner_id, job_id, e);
            }
        }
        Err(e) => {
            let error_str = format!("{:?}", e);
            error!("Runner '{}': Job '{}' failed: {}", runner_id, job_id, error_str);
            
            if let Err(e) = client.set_error(job_id, &error_str).await {
                error!("Runner '{}': Failed to set job '{}' error: {}", runner_id, job_id, e);
            }
            
            if let Err(e) = client.set_job_status(job_id, JobStatus::Error).await {
                error!("Runner '{}': Failed to set job '{}' status to Error: {}", runner_id, job_id, e);
            }
        }
    }
}

/// Convenience function to spawn a runner with the trait-based interface
/// 
/// This function provides a unified interface for spawning any runner implementation
/// that implements the Runner trait.
/// 
/// # Arguments
/// 
/// * `runner` - The runner implementation to spawn
/// * `shutdown_rx` - Channel receiver for shutdown signals
/// 
/// # Returns
/// 
/// Returns a `JoinHandle` that can be awaited to wait for runner shutdown.
pub fn spawn_runner<W: Runner>(
    runner: Arc<W>,
    shutdown_rx: mpsc::Receiver<()>,
) -> JoinHandle<Result<(), Box<dyn std::error::Error + Send + Sync>>> {
    runner.spawn(shutdown_rx)
}