//! Authentication Module
//!
//! Handles the authentication flow: capture frames, detect faces, extract embeddings,
//! and match against stored templates.

use linux_hello_common::{Config, FaceTemplate, Result, TemplateStore};
use tracing::{debug, info, warn};

use crate::camera::PixelFormat;
use crate::detection::detect_face_simple;
use crate::embedding::{EmbeddingExtractor, PlaceholderEmbeddingExtractor};
use crate::matching::{average_embeddings, match_template};
use image::GrayImage;

/// Authentication service
#[derive(Clone)]
pub struct AuthService {
    config: Config,
    template_store_path: std::path::PathBuf,
    embedding_extractor: PlaceholderEmbeddingExtractor,
}

impl AuthService {
    /// Create a new authentication service
    pub fn new(config: Config) -> Self {
        let template_store_path = TemplateStore::default_path();
        let embedding_extractor =
            PlaceholderEmbeddingExtractor::new(PlaceholderEmbeddingExtractor::default_dimension());

        Self {
            config,
            template_store_path,
            embedding_extractor,
        }
    }

    /// Initialize the authentication service
    pub fn initialize(&self) -> Result<()> {
        let template_store = TemplateStore::new(&self.template_store_path);
        template_store.initialize()?;
        Ok(())
    }

    fn template_store(&self) -> TemplateStore {
        TemplateStore::new(&self.template_store_path)
    }

    /// Authenticate a user
    pub async fn authenticate(&self, user: &str) -> Result<bool> {
        info!("Authenticating user: {}", user);

        let template_store = self.template_store();
        
        // Check if user is enrolled
        if !template_store.is_enrolled(user) {
            warn!("User {} is not enrolled", user);
            return Err(linux_hello_common::Error::UserNotEnrolled(user.to_string()));
        }

        // Load templates
        let templates = template_store.load_all(user)?;
        if templates.is_empty() {
            return Err(linux_hello_common::Error::UserNotEnrolled(user.to_string()));
        }

        // Capture and process frames
        let embedding = self.capture_and_extract_embedding().await?;

        // Match against templates
        let result = match_template(
            &embedding,
            &templates,
            self.config.embedding.distance_threshold,
        );

        debug!(
            "Match result: matched={}, similarity={:.3}, threshold={:.3}",
            result.matched, result.best_similarity, result.distance_threshold
        );

        Ok(result.matched)
    }

    /// Enroll a user
    pub async fn enroll(&self, user: &str, label: &str, frame_count: u32) -> Result<()> {
        info!("Enrolling user: {} with label: {}", user, label);

        // Capture multiple frames
        let mut embeddings = Vec::new();

        for i in 0..frame_count {
            debug!("Capturing frame {}/{}", i + 1, frame_count);
            
            match self.capture_and_extract_embedding().await {
                Ok(emb) => {
                    embeddings.push(emb);
                }
                Err(e) => {
                    warn!("Failed to capture frame {}: {}", i + 1, e);
                    // Continue with other frames
                }
            }
        }

        if embeddings.is_empty() {
            return Err(linux_hello_common::Error::Detection(
                "Failed to capture any valid frames".to_string(),
            ));
        }

        // Average embeddings
        let averaged_embedding = average_embeddings(&embeddings)?;

        // Create template
        let template = FaceTemplate {
            user: user.to_string(),
            label: label.to_string(),
            embedding: averaged_embedding,
            enrolled_at: std::time::SystemTime::now()
                .duration_since(std::time::UNIX_EPOCH)
                .unwrap()
                .as_secs(),
            frame_count: embeddings.len() as u32,
        };

        // Store template
        let template_store = self.template_store();
        template_store.store(&template)?;

        info!("User {} enrolled successfully with {} frames", user, template.frame_count);
        Ok(())
    }

    /// Capture a frame and extract embedding
    async fn capture_and_extract_embedding(&self) -> Result<Vec<f32>> {
        // Open camera
        #[cfg(target_os = "linux")]
        use crate::camera::{enumerate_cameras, Camera};

        #[cfg(target_os = "linux")]
        let device_path = if self.config.camera.device == "auto" {
            let cameras = enumerate_cameras()?;
            let ir_cam = cameras.iter().find(|c| c.is_ir);
            let cam = ir_cam.or(cameras.first());
            match cam {
                Some(c) => c.device_path.clone(),
                None => return Err(linux_hello_common::Error::NoCameraFound),
            }
        } else {
            self.config.camera.device.clone()
        };

        #[cfg(not(target_os = "linux"))]
        let device_path = "mock_cam_0".to_string();

        let mut camera = Camera::open(&device_path)?;

        // Capture frame
        let frame = camera.capture_frame()?;
        debug!("Captured frame: {}x{}, format: {:?}", frame.width, frame.height, frame.format);

        // Convert frame to grayscale image
        let gray_image = match frame.format {
            PixelFormat::Grey => {
                GrayImage::from_raw(frame.width, frame.height, frame.data)
                    .ok_or_else(|| linux_hello_common::Error::Detection(
                        "Failed to create grayscale image".to_string(),
                    ))?
            }
            PixelFormat::Yuyv => {
                // Simple YUYV to grayscale conversion (take Y channel)
                let mut gray_data = Vec::with_capacity((frame.width * frame.height) as usize);
                for chunk in frame.data.chunks_exact(2) {
                    gray_data.push(chunk[0]); // Y component
                }
                GrayImage::from_raw(frame.width, frame.height, gray_data)
                    .ok_or_else(|| linux_hello_common::Error::Detection(
                        "Failed to create grayscale from YUYV".to_string(),
                    ))?
            }
            PixelFormat::Mjpeg => {
                // Decode MJPEG (JPEG) to image, then convert to grayscale
                image::load_from_memory(&frame.data)
                    .map_err(|e| linux_hello_common::Error::Detection(
                        format!("Failed to decode MJPEG: {}", e)
                    ))?
                    .to_luma8()
            }
            _ => {
                return Err(linux_hello_common::Error::Detection(format!(
                    "Unsupported pixel format: {:?}",
                    frame.format
                )));
            }
        };

        // Detect face
        let face_detection = detect_face_simple(gray_image.as_raw(), frame.width, frame.height)
            .ok_or(linux_hello_common::Error::NoFaceDetected)?;

        // Extract face region
        let (x, y, w, h) = face_detection.to_pixels(frame.width, frame.height);
        let face_image = extract_face_region(&gray_image, x, y, w, h)?;

        // Extract embedding
        let embedding = self.embedding_extractor.extract(&face_image)?;

        Ok(embedding)
    }
}

/// Extract a face region from an image
fn extract_face_region(
    image: &GrayImage,
    x: u32,
    y: u32,
    w: u32,
    h: u32,
) -> Result<GrayImage> {
    let (img_width, img_height) = image.dimensions();
    
    // Clamp coordinates to image bounds
    let x = x.min(img_width);
    let y = y.min(img_height);
    let w = w.min(img_width - x);
    let h = h.min(img_height - y);

    if w == 0 || h == 0 {
        return Err(linux_hello_common::Error::Detection(
            "Invalid face region".to_string(),
        ));
    }

    let mut face_data = Vec::with_capacity((w * h) as usize);
    
    for row in y..(y + h) {
        for col in x..(x + w) {
            let pixel = image.get_pixel(col, row);
            face_data.push(pixel[0]);
        }
    }

    GrayImage::from_raw(w, h, face_data)
        .ok_or_else(|| linux_hello_common::Error::Detection(
            "Failed to create face image".to_string(),
        ))
}