//! Stdout video backend for piping video output to other tools

use crate::error::{Result, VideoError};
use crate::video::{VideoBackendTrait, VideoStats};
use std::io::{self, Write};
use std::sync::Mutex;
use tracing::{debug, info};

/// Configuration for the stdout video backend
#[derive(Debug, Clone)]
pub struct StdoutConfig {
    /// Whether to output frame headers with metadata
    pub include_headers: bool,
    /// Whether to flush stdout after each frame
    pub flush_after_frame: bool,
    /// Output format for headers (if enabled)
    pub header_format: HeaderFormat,
}

impl Default for StdoutConfig {
    fn default() -> Self {
        Self {
            include_headers: false,
            flush_after_frame: true,
            header_format: HeaderFormat::Simple,
        }
    }
}

/// Header format for frame metadata
#[derive(Debug, Clone)]
pub enum HeaderFormat {
    /// Simple text format: "FRAME:size:timestamp\n"
    Simple,
    /// JSON format: {"frame": {"size": size, "timestamp": timestamp}}
    Json,
    /// Binary format: 4-byte size + 8-byte timestamp
    Binary,
}

/// Stdout video backend that outputs raw video frames to stdout
pub struct StdoutBackend {
    config: StdoutConfig,
    stats: Mutex<VideoStats>,
    frame_count: Mutex<u64>,
    start_time: Mutex<std::time::Instant>,
}

impl StdoutBackend {
    /// Create a new stdout backend with default configuration
    pub fn new() -> Self {
        Self {
            config: StdoutConfig::default(),
            stats: Mutex::new(VideoStats::default()),
            frame_count: Mutex::new(0),
            start_time: Mutex::new(std::time::Instant::now()),
        }
    }

    /// Create a new stdout backend with custom configuration
    pub fn with_config(config: StdoutConfig) -> Self {
        Self {
            config,
            stats: Mutex::new(VideoStats::default()),
            frame_count: Mutex::new(0),
            start_time: Mutex::new(std::time::Instant::now()),
        }
    }

    /// Write frame header if enabled
    fn write_frame_header(&self, frame_size: usize) -> Result<()> {
        if !self.config.include_headers {
            return Ok(());
        }

        let start_time = self.start_time.lock().unwrap();
        let timestamp = start_time.elapsed().as_micros();
        drop(start_time);

        match self.config.header_format {
            HeaderFormat::Simple => {
                let header = format!("FRAME:{}:{}\n", frame_size, timestamp);
                io::stdout().write_all(header.as_bytes())?;
            }
            HeaderFormat::Json => {
                let header = format!(
                    r#"{{"frame": {{"size": {}, "timestamp": {}}}}}{}"#,
                    frame_size, timestamp, '\n'
                );
                io::stdout().write_all(header.as_bytes())?;
            }
            HeaderFormat::Binary => {
                // 4-byte size + 8-byte timestamp
                let size_bytes = (frame_size as u32).to_le_bytes();
                let timestamp_bytes = timestamp.to_le_bytes();
                let mut header = Vec::with_capacity(12);
                header.extend_from_slice(&size_bytes);
                header.extend_from_slice(&timestamp_bytes);
                io::stdout().write_all(&header)?;
            }
        }
        Ok(())
    }

    /// Update statistics
    fn update_stats(&self, frame_size: usize) {
        let mut frame_count = self.frame_count.lock().unwrap();
        *frame_count += 1;
        let current_frame_count = *frame_count;
        drop(frame_count);

        let mut stats = self.stats.lock().unwrap();
        stats.frames_pushed = current_frame_count;
        stats.total_bytes += frame_size as u64;
        
        // Calculate FPS based on elapsed time
        let start_time = self.start_time.lock().unwrap();
        let elapsed = start_time.elapsed().as_secs_f64();
        drop(start_time);
        
        if elapsed > 0.0 {
            stats.fps = current_frame_count as f64 / elapsed;
        }

        // Log frame information for debugging
        if current_frame_count % 30 == 0 { // Log every 30 frames
            tracing::debug!(
                "Stdout backend: frame {}, size: {} bytes, total: {} bytes, fps: {:.2}",
                current_frame_count, frame_size, stats.total_bytes, stats.fps
            );
        }
    }
}

impl VideoBackendTrait for StdoutBackend {
    fn initialize(&mut self) -> Result<()> {
        info!("Initializing stdout video backend");
        {
            let mut start_time = self.start_time.lock().unwrap();
            *start_time = std::time::Instant::now();
        }
        {
            let mut stats = self.stats.lock().unwrap();
            stats.is_ready = true;
        }
        
        // Write initial header if enabled
        if self.config.include_headers {
            match self.config.header_format {
                HeaderFormat::Simple => {
                    io::stdout().write_all(b"STDOUT_VIDEO_STREAM_START\n")?;
                }
                HeaderFormat::Json => {
                    io::stdout().write_all(b"{\"stream\": \"start\"}\n")?;
                }
                HeaderFormat::Binary => {
                    // Magic number: "STDO" (4 bytes)
                    io::stdout().write_all(b"STDO")?;
                }
            }
        }
        
        debug!("Stdout video backend initialized successfully");
        Ok(())
    }

    fn push_frame(&self, frame_data: &[u8]) -> Result<()> {
        let stats = self.stats.lock().unwrap();
        if !stats.is_ready {
            return Err(VideoError::DeviceNotReady.into());
        }
        drop(stats);

        // Write frame header if enabled
        self.write_frame_header(frame_data.len())?;

        // Write frame data to stdout
        io::stdout().write_all(frame_data)?;

        // Flush if configured
        if self.config.flush_after_frame {
            io::stdout().flush()?;
        }

        // Update statistics
        self.update_stats(frame_data.len());
        debug!("Pushed frame to stdout: {} bytes", frame_data.len());
        Ok(())
    }

    fn get_stats(&self) -> VideoStats {
        let mut stats = self.stats.lock().unwrap().clone();
        stats.backend_type = crate::video::VideoBackendType::Stdout;
        stats
    }

    fn is_ready(&self) -> bool {
        self.stats.lock().unwrap().is_ready
    }

    fn shutdown(&mut self) -> Result<()> {
        info!("Shutting down stdout video backend");
        
        // Write final header if enabled
        if self.config.include_headers {
            match self.config.header_format {
                HeaderFormat::Simple => {
                    io::stdout().write_all(b"STDOUT_VIDEO_STREAM_END\n")?;
                }
                HeaderFormat::Json => {
                    io::stdout().write_all(b"{\"stream\": \"end\"}\n")?;
                }
                HeaderFormat::Binary => {
                    // End marker: "END\0" (4 bytes)
                    io::stdout().write_all(b"END\0")?;
                }
            }
        }

        // Final flush
        io::stdout().flush()?;
        
        {
            let mut stats = self.stats.lock().unwrap();
            stats.is_ready = false;
        }
        Ok(())
    }
}

impl Drop for StdoutBackend {
    fn drop(&mut self) {
        let is_ready = {
            let stats = self.stats.lock().unwrap();
            stats.is_ready
        };
        if is_ready {
            let _ = self.shutdown();
        }
    }
}

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

    #[test]
    fn test_stdout_backend_creation() {
        let backend = StdoutBackend::new();
        assert!(!backend.is_ready());
        assert_eq!(backend.get_stats().frames_pushed, 0);
    }

    #[test]
    fn test_stdout_backend_with_config() {
        let config = StdoutConfig {
            include_headers: true,
            flush_after_frame: false,
            header_format: HeaderFormat::Json,
        };
        let backend = StdoutBackend::with_config(config);
        assert!(!backend.is_ready());
    }

    #[test]
    fn test_header_format_creation() {
        let simple = HeaderFormat::Simple;
        let json = HeaderFormat::Json;
        let binary = HeaderFormat::Binary;
        
        // Just test that they can be created
        assert!(matches!(simple, HeaderFormat::Simple));
        assert!(matches!(json, HeaderFormat::Json));
        assert!(matches!(binary, HeaderFormat::Binary));
    }
}