use anyhow::{Result, Context};
use std::collections::VecDeque;
use tokio::time::{sleep, Duration};

use crate::events::{EventBus, SystemEvent, FrameCapturedEvent, MeteorDetectedEvent};

/// Configuration for the detection controller
#[derive(Debug, Clone)]
pub struct DetectionConfig {
    pub algorithm_name: String,
    pub brightness_threshold: f32,
    pub buffer_capacity: usize,
    pub min_event_frames: usize,
    pub max_event_gap_frames: usize,
}

impl Default for DetectionConfig {
    fn default() -> Self {
        Self {
            algorithm_name: "brightness_diff".to_string(),
            brightness_threshold: 0.3,
            buffer_capacity: 150,
            min_event_frames: 3,
            max_event_gap_frames: 10,
        }
    }
}

/// Available detection algorithms
#[derive(Debug, Clone)]
pub enum DetectionAlgorithm {
    BrightnessDiff,
    // Future algorithms can be added here
}

/// Stored frame information for analysis
#[derive(Debug, Clone)]
struct StoredFrame {
    frame_id: u64,
    timestamp: chrono::DateTime<chrono::Utc>,
    width: u32,
    height: u32,
    brightness_score: f64, // Simplified representation for analysis
}

/// Detection controller that analyzes frames for meteors
pub struct DetectionController {
    config: DetectionConfig,
    event_bus: EventBus,
    frame_buffer: VecDeque<StoredFrame>,
    last_processed_frame_id: u64,
}

impl DetectionController {
    /// Create a new detection controller
    pub fn new(config: DetectionConfig, event_bus: EventBus) -> Self {
        let buffer_capacity = config.buffer_capacity;
        Self {
            config,
            event_bus,
            frame_buffer: VecDeque::with_capacity(buffer_capacity),
            last_processed_frame_id: 0,
        }
    }

    /// Start the detection loop
    pub async fn run(&mut self) -> Result<()> {
        println!("🔍 Starting meteor detection controller...");
        println!("   Buffer size: {} frames", self.config.buffer_capacity);
        println!("   Algorithm: {}", self.config.algorithm_name);
        println!("   Brightness threshold: {}", self.config.brightness_threshold);
        println!("   Min event frames: {}", self.config.min_event_frames);

        let mut event_receiver = self.event_bus.subscribe();
        let check_interval = Duration::from_millis(100); // Fixed 100ms check interval

        println!("✅ Detection controller initialized, starting analysis loop...");

        loop {
            tokio::select! {
                // Handle incoming events
                event_result = event_receiver.recv() => {
                    match event_result {
                        Ok(event) => {
                            if let Err(e) = self.handle_event(event.as_ref()).await {
                                eprintln!("❌ Error handling event: {}", e);
                            }
                        }
                        Err(e) => {
                            eprintln!("❌ Error receiving event: {}", e);
                            tokio::time::sleep(Duration::from_secs(1)).await;
                        }
                    }
                }
                
                // Periodic analysis check
                _ = sleep(check_interval) => {
                    if let Err(e) = self.run_detection_analysis().await {
                        eprintln!("❌ Error in detection analysis: {}", e);
                    }
                }
            }
        }
    }

    /// Handle incoming events from the event bus
    async fn handle_event(&mut self, event: &SystemEvent) -> Result<()> {
        match event {
            SystemEvent::FrameCaptured(frame_event) => {
                self.process_frame_event(frame_event.clone()).await?;
            }
            SystemEvent::SystemStarted(_) => {
                println!("🔍 Detection controller received system started event");
            }
            SystemEvent::MeteorDetected(_) => {
                // We don't need to process our own detections
            }
            SystemEvent::EventPackageArchived(_) => {
                // Detection controller doesn't need to handle archived events
            }
        }
        Ok(())
    }

    /// Process a captured frame event and add to buffer
    async fn process_frame_event(&mut self, frame_event: FrameCapturedEvent) -> Result<()> {
        // Calculate brightness score (simplified analysis)
        let brightness_score = self.calculate_brightness_score(&frame_event)?;

        let stored_frame = StoredFrame {
            frame_id: frame_event.frame_id,
            timestamp: frame_event.timestamp,
            width: frame_event.frame_data.width,
            height: frame_event.frame_data.height,
            brightness_score,
        };

        // Add to circular buffer
        self.frame_buffer.push_back(stored_frame);

        // Maintain buffer size
        while self.frame_buffer.len() > self.config.buffer_capacity {
            self.frame_buffer.pop_front();
        }

        // Update last processed frame ID
        self.last_processed_frame_id = frame_event.frame_id;

        if frame_event.frame_id % 50 == 0 {
            println!("🔍 Processed {} frames, buffer size: {}", 
                frame_event.frame_id, 
                self.frame_buffer.len()
            );
        }

        Ok(())
    }

    /// Calculate brightness score from frame data (simplified)
    fn calculate_brightness_score(&self, frame_event: &FrameCapturedEvent) -> Result<f64> {
        // Simplified brightness calculation based on frame data content
        // In our synthetic JPEG format, the brightness is encoded in the pixel values
        
        if frame_event.frame_data.len() < 8 { // Need at least header + some data
            return Ok(0.0);
        }
        
        // Skip the fake JPEG header (first 4 bytes) and footer (last 2 bytes)
        let data_start = 4;
        let frame_data_slice = frame_event.frame_data.as_slice();
        let data_end = frame_data_slice.len().saturating_sub(2);
        
        if data_start >= data_end {
            return Ok(0.0);
        }
        
        // Calculate average pixel value (brightness) from the data section
        let pixel_data = &frame_data_slice[data_start..data_end];
        let average_brightness = pixel_data.iter()
            .map(|&b| b as f64)
            .sum::<f64>() / pixel_data.len() as f64;
        
        // Normalize to 0.0-1.0 range (assuming 255 is max brightness)
        let score = (average_brightness / 255.0).min(1.0).max(0.0);
        
        Ok(score)
    }

    /// Run detection analysis on the frame buffer
    async fn run_detection_analysis(&mut self) -> Result<()> {
        if self.frame_buffer.len() < 10 { // Need at least 10 frames for analysis
            return Ok(());
        }

        match self.config.algorithm_name.as_str() {
            "brightness_diff" => {
                self.run_brightness_diff_detection().await?;
            }
            _ => {
                eprintln!("Unknown detection algorithm: {}", self.config.algorithm_name);
            }
        }

        Ok(())
    }

    /// Run brightness difference detection algorithm
    async fn run_brightness_diff_detection(&mut self) -> Result<()> {
        let frames: Vec<&StoredFrame> = self.frame_buffer.iter().collect();
        
        // Need at least 10 frames for reliable detection
        if frames.len() < 10 {
            return Ok(());
        }
        
        // Calculate average brightness of historical frames (excluding recent ones)
        let history_end = frames.len().saturating_sub(3); // Exclude last 3 frames
        if history_end < 5 {
            return Ok(());
        }

        let historical_avg = frames[..history_end]
            .iter()
            .map(|f| f.brightness_score)
            .sum::<f64>() / history_end as f64;

        // Check recent frames for significant brightness increase
        for recent_frame in &frames[history_end..] {
            let brightness_diff = recent_frame.brightness_score - historical_avg;
            let relative_increase = if historical_avg > 0.0 {
                brightness_diff / historical_avg
            } else {
                brightness_diff
            };
            
            // Use relative increase as confidence
            let confidence = relative_increase.max(0.0).min(1.0);

            // Debug output
            if frames.len() >= 15 {
                println!("🔍 DEBUG: Frame #{}, Historical avg: {:.3}, Current: {:.3}, Diff: {:.3}, Confidence: {:.3}", 
                    recent_frame.frame_id,
                    historical_avg,
                    recent_frame.brightness_score,
                    brightness_diff,
                    confidence
                );
            }

            if confidence >= self.config.brightness_threshold as f64 {
                // Potential meteor detected!
                let detection_event = MeteorDetectedEvent::new(
                    recent_frame.frame_id,
                    recent_frame.timestamp,
                    confidence,
                    "brightness_diff_v1".to_string(),
                );

                println!("🌟 METEOR DETECTED! Frame #{}, Confidence: {:.2}", 
                    recent_frame.frame_id, 
                    confidence
                );

                self.event_bus.publish_meteor_detected(detection_event)
                    .context("Failed to publish meteor detection event")?;

                // Prevent duplicate detections for a short period
                // by clearing recent frames from analysis
                break;
            }
        }

        Ok(())
    }

    /// Get current buffer statistics
    pub fn get_stats(&self) -> DetectionStats {
        DetectionStats {
            buffer_size: self.frame_buffer.len(),
            buffer_capacity: self.config.buffer_capacity,
            last_processed_frame_id: self.last_processed_frame_id,
            avg_brightness: if !self.frame_buffer.is_empty() {
                self.frame_buffer.iter().map(|f| f.brightness_score).sum::<f64>() 
                    / self.frame_buffer.len() as f64
            } else {
                0.0
            },
        }
    }
}

/// Statistics about the detection system
#[derive(Debug, Clone)]
pub struct DetectionStats {
    pub buffer_size: usize,
    pub buffer_capacity: usize,
    pub last_processed_frame_id: u64,
    pub avg_brightness: f64,
}

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

    #[test]
    fn test_detection_config_default() {
        let config = DetectionConfig::default();
        assert_eq!(config.buffer_capacity, 150);
        assert_eq!(config.brightness_threshold, 0.3);
        assert_eq!(config.min_event_frames, 3);
        assert_eq!(config.algorithm_name, "brightness_diff");
    }

    #[test]
    fn test_detection_controller_creation() {
        let config = DetectionConfig::default();
        let event_bus = EventBus::new(100);
        let controller = DetectionController::new(config, event_bus);
        
        assert_eq!(controller.frame_buffer.len(), 0);
        assert_eq!(controller.last_processed_frame_id, 0);
    }

    #[test]
    fn test_detection_stats() {
        let config = DetectionConfig::default();
        let event_bus = EventBus::new(100);
        let controller = DetectionController::new(config, event_bus);
        
        let stats = controller.get_stats();
        assert_eq!(stats.buffer_size, 0);
        assert_eq!(stats.buffer_capacity, 100);
        assert_eq!(stats.last_processed_frame_id, 0);
        assert_eq!(stats.avg_brightness, 0.0);
    }
}