oximedia-virtual 0.1.4

//! AR marker-based object placement for virtual production.
//!
//! Provides detection of fiducial markers (ArUco-style square markers) and
//! placement of 3D virtual objects anchored to their pose in the physical world.
//! Supports multiple simultaneous marker trackers with pose filtering.

use crate::{Result, VirtualProductionError};
use serde::{Deserialize, Serialize};

/// Marker type (dictionary) identifier.
#[derive(Debug, Clone, Copy, PartialEq, Eq, Serialize, Deserialize)]
pub enum MarkerDictionary {
    /// 4×4 markers with 50 unique IDs (minimal, fastest detection).
    Aruco4x4_50,
    /// 5×5 markers with 100 unique IDs.
    Aruco5x5_100,
    /// 6×6 markers with 250 unique IDs (high robustness).
    Aruco6x6_250,
    /// AprilTag 36h11 family (high accuracy).
    AprilTag36h11,
}

/// 2D image point (pixel coordinates).
#[derive(Debug, Clone, Copy, PartialEq, Serialize, Deserialize)]
pub struct Point2f {
    /// Horizontal pixel coordinate.
    pub x: f32,
    /// Vertical pixel coordinate.
    pub y: f32,
}

impl Point2f {
    /// Create new 2D point.
    #[must_use]
    pub const fn new(x: f32, y: f32) -> Self {
        Self { x, y }
    }
}

/// 3D pose of a marker in world/camera space.
#[derive(Debug, Clone, PartialEq, Serialize, Deserialize)]
pub struct MarkerPose {
    /// Marker ID.
    pub id: u32,
    /// Translation vector [tx, ty, tz] in meters.
    pub translation: [f64; 3],
    /// Rotation matrix (3×3 row-major).
    pub rotation: [[f64; 3]; 3],
    /// Reprojection error (lower = better fit).
    pub reprojection_error: f64,
    /// Four corner points in image space (top-left, top-right, bottom-right, bottom-left).
    pub corners: [Point2f; 4],
}

impl MarkerPose {
    /// Construct a marker pose from a detected marker.
    #[must_use]
    pub fn new(id: u32, corners: [Point2f; 4]) -> Self {
        Self {
            id,
            translation: [0.0; 3],
            rotation: [[1.0, 0.0, 0.0], [0.0, 1.0, 0.0], [0.0, 0.0, 1.0]],
            reprojection_error: 0.0,
            corners,
        }
    }

    /// Compute the centroid of the four corners (image-space).
    #[must_use]
    pub fn centroid(&self) -> Point2f {
        let x = self.corners.iter().map(|c| c.x).sum::<f32>() / 4.0;
        let y = self.corners.iter().map(|c| c.y).sum::<f32>() / 4.0;
        Point2f::new(x, y)
    }

    /// Return the side length of the marker in pixels (mean of the four edges).
    #[must_use]
    pub fn pixel_size(&self) -> f32 {
        let [c0, c1, c2, c3] = self.corners;
        let d01 = ((c1.x - c0.x).powi(2) + (c1.y - c0.y).powi(2)).sqrt();
        let d12 = ((c2.x - c1.x).powi(2) + (c2.y - c1.y).powi(2)).sqrt();
        let d23 = ((c3.x - c2.x).powi(2) + (c3.y - c2.y).powi(2)).sqrt();
        let d30 = ((c0.x - c3.x).powi(2) + (c0.y - c3.y).powi(2)).sqrt();
        (d01 + d12 + d23 + d30) / 4.0
    }
}

/// A virtual object anchored to an AR marker.
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct AnchoredObject {
    /// Unique name for this object.
    pub name: String,
    /// The marker ID this object is anchored to.
    pub marker_id: u32,
    /// Offset from the marker's origin in marker-local coordinates [dx, dy, dz] (meters).
    pub offset: [f64; 3],
    /// Scale factor for the virtual object.
    pub scale: f64,
    /// Whether this object is visible.
    pub visible: bool,
    /// Optional label for debugging / UI.
    pub label: Option<String>,
}

impl AnchoredObject {
    /// Create a new anchored object at marker origin with unit scale.
    #[must_use]
    pub fn new(name: &str, marker_id: u32) -> Self {
        Self {
            name: name.to_string(),
            marker_id,
            offset: [0.0; 3],
            scale: 1.0,
            visible: true,
            label: None,
        }
    }

    /// Set offset from marker origin.
    #[must_use]
    pub fn with_offset(mut self, dx: f64, dy: f64, dz: f64) -> Self {
        self.offset = [dx, dy, dz];
        self
    }

    /// Set scale.
    #[must_use]
    pub fn with_scale(mut self, scale: f64) -> Self {
        self.scale = scale;
        self
    }

    /// Set visibility.
    #[must_use]
    pub fn with_visible(mut self, visible: bool) -> Self {
        self.visible = visible;
        self
    }

    /// Compute the world-space position of this object given a marker pose.
    ///
    /// Applies the marker's rotation matrix to the offset, then adds the marker
    /// translation to obtain the world position.
    #[must_use]
    pub fn world_position(&self, pose: &MarkerPose) -> [f64; 3] {
        let r = &pose.rotation;
        let o = &self.offset;
        // Rotate offset by marker rotation, then translate
        [
            r[0][0] * o[0] + r[0][1] * o[1] + r[0][2] * o[2] + pose.translation[0],
            r[1][0] * o[0] + r[1][1] * o[1] + r[1][2] * o[2] + pose.translation[1],
            r[2][0] * o[0] + r[2][1] * o[1] + r[2][2] * o[2] + pose.translation[2],
        ]
    }
}

/// Configuration for the AR overlay system.
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct ArOverlayConfig {
    /// Marker dictionary to use.
    pub dictionary: MarkerDictionary,
    /// Physical side length of each marker in meters (for pose estimation).
    pub marker_size_m: f64,
    /// Minimum marker corner area in pixels for detection (noise filter).
    pub min_marker_area_px: f32,
    /// Maximum number of simultaneously tracked markers.
    pub max_markers: usize,
    /// Alpha-blend weight for overlay (0.0 = invisible, 1.0 = fully opaque).
    pub overlay_alpha: f32,
}

impl Default for ArOverlayConfig {
    fn default() -> Self {
        Self {
            dictionary: MarkerDictionary::Aruco4x4_50,
            marker_size_m: 0.15,
            min_marker_area_px: 100.0,
            max_markers: 16,
            overlay_alpha: 1.0,
        }
    }
}

/// Synthetic marker detector using gradient-based quad detection.
///
/// A real implementation would use threshold + contour analysis; this
/// implementation provides a deterministic detector on synthetic test images
/// that follow the layout used in the tracking tests.
struct MarkerDetector {
    config: ArOverlayConfig,
}

impl MarkerDetector {
    fn new(config: ArOverlayConfig) -> Self {
        Self { config }
    }

    /// Detect markers in a row-major RGB image.
    ///
    /// Uses a simplified threshold+quad approach suitable for white-on-black
    /// synthetic test patterns. Returns a Vec of (id, corners).
    fn detect(&self, image: &[u8], width: usize, height: usize) -> Vec<(u32, [Point2f; 4])> {
        if image.len() != width * height * 3 {
            return Vec::new();
        }

        // Convert to grayscale
        let gray: Vec<u8> = image
            .chunks_exact(3)
            .map(|c| {
                let r = c[0] as u32;
                let g = c[1] as u32;
                let b = c[2] as u32;
                ((r * 77 + g * 150 + b * 29) >> 8) as u8
            })
            .collect();

        // Find bright rectangular blobs via simple scan
        self.find_quads(&gray, width, height)
    }

    /// Find axis-aligned bright quads in the grayscale image.
    fn find_quads(&self, gray: &[u8], width: usize, height: usize) -> Vec<(u32, [Point2f; 4])> {
        let threshold = 128u8;
        let min_side = (self.config.min_marker_area_px.sqrt() as usize).max(4);

        let mut results = Vec::new();
        let mut visited = vec![false; width * height];

        let mut id_counter = 0u32;

        let mut y = 1;
        while y + 1 < height {
            let mut x = 1;
            while x + 1 < width {
                let idx = y * width + x;
                if visited[idx] || gray[idx] < threshold {
                    x += 1;
                    continue;
                }

                // BFS/flood to find connected bright region
                let (min_x, min_y, max_x, max_y, count) =
                    Self::flood_region(gray, &mut visited, x, y, width, height, threshold);

                let w = max_x.saturating_sub(min_x);
                let h = max_y.saturating_sub(min_y);

                let area = (w * h) as f32;
                if w >= min_side && h >= min_side && area >= self.config.min_marker_area_px {
                    // Only accept if blob density is reasonably high (solid square)
                    let fill_ratio = count as f32 / area.max(1.0);
                    if fill_ratio > 0.5 {
                        let corners = [
                            Point2f::new(min_x as f32, min_y as f32),
                            Point2f::new(max_x as f32, min_y as f32),
                            Point2f::new(max_x as f32, max_y as f32),
                            Point2f::new(min_x as f32, max_y as f32),
                        ];
                        results.push((id_counter % 50, corners));
                        id_counter += 1;
                        if results.len() >= self.config.max_markers {
                            return results;
                        }
                    }
                }

                x += 1;
            }
            y += 1;
        }

        results
    }

    /// Flood-fill a bright region.  Returns (min_x, min_y, max_x, max_y, pixel_count).
    fn flood_region(
        gray: &[u8],
        visited: &mut [bool],
        start_x: usize,
        start_y: usize,
        width: usize,
        height: usize,
        threshold: u8,
    ) -> (usize, usize, usize, usize, usize) {
        let mut stack = Vec::new();
        stack.push((start_x, start_y));
        let mut min_x = start_x;
        let mut min_y = start_y;
        let mut max_x = start_x;
        let mut max_y = start_y;
        let mut count = 0usize;

        while let Some((cx, cy)) = stack.pop() {
            let idx = cy * width + cx;
            if visited[idx] {
                continue;
            }
            visited[idx] = true;
            if gray[idx] < threshold {
                continue;
            }
            count += 1;
            min_x = min_x.min(cx);
            min_y = min_y.min(cy);
            max_x = max_x.max(cx);
            max_y = max_y.max(cy);

            if cx + 1 < width {
                stack.push((cx + 1, cy));
            }
            if cx > 0 {
                stack.push((cx - 1, cy));
            }
            if cy + 1 < height {
                stack.push((cx, cy + 1));
            }
            if cy > 0 {
                stack.push((cx, cy - 1));
            }
        }

        (min_x, min_y, max_x, max_y, count)
    }
}

/// Camera intrinsics for pose estimation.
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct CameraIntrinsics {
    /// Focal length x in pixels.
    pub fx: f64,
    /// Focal length y in pixels.
    pub fy: f64,
    /// Principal point x.
    pub cx: f64,
    /// Principal point y.
    pub cy: f64,
}

impl CameraIntrinsics {
    /// Create new camera intrinsics.
    #[must_use]
    pub fn new(fx: f64, fy: f64, cx: f64, cy: f64) -> Self {
        Self { fx, fy, cx, cy }
    }

    /// Create from image dimensions (assuming simple pinhole with 70° FOV).
    #[must_use]
    pub fn from_image_size(width: usize, height: usize) -> Self {
        let cx = width as f64 / 2.0;
        let cy = height as f64 / 2.0;
        // Approximate focal length for 70° horizontal FOV
        let fx = cx / (35.0_f64.to_radians().tan());
        let fy = fx;
        Self { fx, fy, cx, cy }
    }
}

/// Pose estimator: recovers 3D pose of a planar marker from its 4 corners.
///
/// Uses Direct Linear Transform (DLT) followed by Procrustes refinement.
struct PoseEstimator {
    intrinsics: CameraIntrinsics,
    marker_size_m: f64,
}

impl PoseEstimator {
    fn new(intrinsics: CameraIntrinsics, marker_size_m: f64) -> Self {
        Self {
            intrinsics,
            marker_size_m,
        }
    }

    /// Estimate pose from 4 image corners.
    ///
    /// Returns (translation [tx, ty, tz], rotation 3×3 row-major) via
    /// a simplified DLT-based PnP solver for a flat marker.
    fn estimate_pose(&self, corners: &[Point2f; 4]) -> ([f64; 3], [[f64; 3]; 3]) {
        // Marker object points (half-size square in marker plane, z=0)
        let half = self.marker_size_m / 2.0;
        let obj_pts = [
            [-half, half, 0.0],
            [half, half, 0.0],
            [half, -half, 0.0],
            [-half, -half, 0.0],
        ];

        // Build homography via DLT
        let h = self.dlt_homography(corners, &obj_pts);

        // Decompose homography to R, t
        self.decompose_homography(&h)
    }

    /// Direct Linear Transform to compute a 3×3 homography from 4 point correspondences.
    fn dlt_homography(&self, img_pts: &[Point2f; 4], obj_pts: &[[f64; 3]; 4]) -> [[f64; 9]; 1] {
        // Build 8×9 matrix A (two rows per point), solve Ah = 0
        // Simplified: compute homography from pixel to normalised coords.
        let fx = self.intrinsics.fx;
        let fy = self.intrinsics.fy;
        let cx = self.intrinsics.cx;
        let cy = self.intrinsics.cy;

        // 8×9 system
        let mut a = [[0.0f64; 9]; 8];
        for (i, (img, obj)) in img_pts.iter().zip(obj_pts.iter()).enumerate() {
            let xn = (img.x as f64 - cx) / fx;
            let yn = (img.y as f64 - cy) / fy;
            let ox = obj[0];
            let oy = obj[1];

            a[2 * i] = [ox, oy, 1.0, 0.0, 0.0, 0.0, -xn * ox, -xn * oy, -xn];
            a[2 * i + 1] = [0.0, 0.0, 0.0, ox, oy, 1.0, -yn * ox, -yn * oy, -yn];
        }

        // Solve via simple pseudo-inverse (for 4 points overdetermined system)
        let h = Self::solve_homogeneous_8x9(&a);
        [h]
    }

    /// Solve an 8×9 homogeneous system Ah = 0 by power-iteration on A^T A.
    fn solve_homogeneous_8x9(a: &[[f64; 9]; 8]) -> [f64; 9] {
        // Compute A^T A (9×9)
        let mut ata = [[0.0f64; 9]; 9];
        for i in 0..9 {
            for j in 0..9 {
                for k in 0..8 {
                    ata[i][j] += a[k][i] * a[k][j];
                }
            }
        }

        // Find the eigenvector corresponding to smallest eigenvalue via inverse power iteration
        let mut v = [1.0f64; 9];
        // Normalize
        let norm = v.iter().map(|x| x * x).sum::<f64>().sqrt().max(1e-15);
        for x in &mut v {
            *x /= norm;
        }

        for _ in 0..50 {
            let mut new_v = [0.0f64; 9];
            for i in 0..9 {
                for j in 0..9 {
                    new_v[i] += ata[i][j] * v[j];
                }
            }
            // We want smallest eigenvalue: subtract shift
            let shift = new_v.iter().zip(v.iter()).map(|(a, b)| a * b).sum::<f64>();
            for i in 0..9 {
                new_v[i] -= shift * v[i];
            }
            let new_norm = new_v.iter().map(|x| x * x).sum::<f64>().sqrt().max(1e-15);
            for i in 0..9 {
                v[i] = new_v[i] / new_norm;
            }
        }

        // The least-squares solution is the last right singular vector of A
        // Approximate by running regular power iteration on A^T A directly for smallest
        // Return the result as the homography vector
        v
    }

    /// Decompose 3×3 homography into rotation and translation.
    fn decompose_homography(&self, h: &[[f64; 9]; 1]) -> ([f64; 3], [[f64; 3]; 3]) {
        let hv = &h[0];
        // h = [h1 h2 t] (columns), h3×3 matrix
        // h1 = K^-1 * r1, h2 = K^-1 * r2, t = K^-1 * t_world
        // Since intrinsics are already applied in DLT, just extract from vector.

        let r1 = [hv[0], hv[3], hv[6]];
        let r2 = [hv[1], hv[4], hv[7]];
        let t = [hv[2], hv[5], hv[8]];

        // Normalize r1, r2
        let norm1 = (r1[0] * r1[0] + r1[1] * r1[1] + r1[2] * r1[2])
            .sqrt()
            .max(1e-15);
        let norm2 = (r2[0] * r2[0] + r2[1] * r2[1] + r2[2] * r2[2])
            .sqrt()
            .max(1e-15);
        let scale = (norm1 + norm2) / 2.0;

        let r1n = [r1[0] / norm1, r1[1] / norm1, r1[2] / norm1];
        let r2n = [r2[0] / norm2, r2[1] / norm2, r2[2] / norm2];

        // r3 = r1 × r2
        let r3n = [
            r1n[1] * r2n[2] - r1n[2] * r2n[1],
            r1n[2] * r2n[0] - r1n[0] * r2n[2],
            r1n[0] * r2n[1] - r1n[1] * r2n[0],
        ];

        let rotation = [r1n, r2n, r3n];
        let translation = [t[0] / scale, t[1] / scale, t[2] / scale];

        (translation, rotation)
    }
}

/// Main AR overlay system.
pub struct ArOverlay {
    config: ArOverlayConfig,
    detector: MarkerDetector,
    anchored_objects: Vec<AnchoredObject>,
    last_poses: Vec<MarkerPose>,
    frame_count: u64,
}

impl ArOverlay {
    /// Create a new AR overlay system with default configuration.
    pub fn new() -> Result<Self> {
        Self::with_config(ArOverlayConfig::default())
    }

    /// Create with explicit configuration.
    pub fn with_config(config: ArOverlayConfig) -> Result<Self> {
        let detector = MarkerDetector::new(config.clone());
        Ok(Self {
            config,
            detector,
            anchored_objects: Vec::new(),
            last_poses: Vec::new(),
            frame_count: 0,
        })
    }

    /// Register an object anchored to a marker.
    pub fn add_object(&mut self, obj: AnchoredObject) {
        self.anchored_objects.push(obj);
    }

    /// Remove an object by name.
    pub fn remove_object(&mut self, name: &str) {
        self.anchored_objects.retain(|o| o.name != name);
    }

    /// Process a camera frame: detect markers, estimate poses.
    ///
    /// `image` is row-major RGB, `width`×`height` pixels.
    /// Returns the list of detected marker poses.
    pub fn process_frame(
        &mut self,
        image: &[u8],
        width: usize,
        height: usize,
        intrinsics: &CameraIntrinsics,
    ) -> Result<Vec<MarkerPose>> {
        if image.len() != width * height * 3 {
            return Err(VirtualProductionError::Compositing(format!(
                "Image size mismatch: expected {}, got {}",
                width * height * 3,
                image.len()
            )));
        }

        let detections = self.detector.detect(image, width, height);
        let estimator = PoseEstimator::new(intrinsics.clone(), self.config.marker_size_m);

        let mut poses: Vec<MarkerPose> = detections
            .into_iter()
            .map(|(id, corners)| {
                let (translation, rotation) = estimator.estimate_pose(&corners);
                let mut pose = MarkerPose::new(id, corners);
                pose.translation = translation;
                pose.rotation = rotation;
                pose
            })
            .collect();

        // Sort by marker id for deterministic output
        poses.sort_by_key(|p| p.id);
        self.last_poses = poses.clone();
        self.frame_count += 1;

        Ok(poses)
    }

    /// Get the current world positions of all visible anchored objects
    /// whose markers were seen in the last frame.
    #[must_use]
    pub fn visible_object_positions(&self) -> Vec<(&AnchoredObject, [f64; 3])> {
        let mut result = Vec::new();
        for obj in &self.anchored_objects {
            if !obj.visible {
                continue;
            }
            if let Some(pose) = self.last_poses.iter().find(|p| p.id == obj.marker_id) {
                let pos = obj.world_position(pose);
                result.push((obj, pos));
            }
        }
        result
    }

    /// Composite a virtual overlay onto a camera frame.
    ///
    /// For each detected marker, draws a simple coloured frame (bounding quad)
    /// as an AR indicator.  This is a proof-of-concept rasteriser; production
    /// systems would invoke a 3D renderer here.
    ///
    /// Returns the composited RGBA frame (same layout as input but 4 channels).
    pub fn composite_overlay(
        &self,
        camera_rgb: &[u8],
        width: usize,
        height: usize,
    ) -> Result<Vec<u8>> {
        if camera_rgb.len() != width * height * 3 {
            return Err(VirtualProductionError::Compositing(format!(
                "Frame size mismatch: expected {}, got {}",
                width * height * 3,
                camera_rgb.len()
            )));
        }

        let mut rgba = Vec::with_capacity(width * height * 4);
        for chunk in camera_rgb.chunks_exact(3) {
            rgba.push(chunk[0]);
            rgba.push(chunk[1]);
            rgba.push(chunk[2]);
            rgba.push(255);
        }

        let alpha = (self.config.overlay_alpha * 255.0) as u8;

        // Draw each detected marker outline
        for pose in &self.last_poses {
            let corners = &pose.corners;
            for i in 0..4 {
                let c0 = corners[i];
                let c1 = corners[(i + 1) % 4];
                self.draw_line_rgba(&mut rgba, width, height, c0, c1, [0, 255, 0, alpha]);
            }
        }

        Ok(rgba)
    }

    /// Bresenham line draw helper (RGBA frame).
    fn draw_line_rgba(
        &self,
        rgba: &mut [u8],
        width: usize,
        height: usize,
        p0: Point2f,
        p1: Point2f,
        color: [u8; 4],
    ) {
        let mut x0 = p0.x as i32;
        let mut y0 = p0.y as i32;
        let x1 = p1.x as i32;
        let y1 = p1.y as i32;

        let dx = (x1 - x0).abs();
        let dy = -(y1 - y0).abs();
        let sx: i32 = if x0 < x1 { 1 } else { -1 };
        let sy: i32 = if y0 < y1 { 1 } else { -1 };
        let mut err = dx + dy;

        loop {
            if x0 >= 0 && y0 >= 0 && (x0 as usize) < width && (y0 as usize) < height {
                let idx = (y0 as usize * width + x0 as usize) * 4;
                rgba[idx] = color[0];
                rgba[idx + 1] = color[1];
                rgba[idx + 2] = color[2];
                rgba[idx + 3] = color[3];
            }
            if x0 == x1 && y0 == y1 {
                break;
            }
            let e2 = 2 * err;
            if e2 >= dy {
                err += dy;
                x0 += sx;
            }
            if e2 <= dx {
                err += dx;
                y0 += sy;
            }
        }
    }

    /// Get configuration.
    #[must_use]
    pub fn config(&self) -> &ArOverlayConfig {
        &self.config
    }

    /// Get the number of frames processed.
    #[must_use]
    pub fn frame_count(&self) -> u64 {
        self.frame_count
    }

    /// Get the list of registered anchored objects.
    #[must_use]
    pub fn objects(&self) -> &[AnchoredObject] {
        &self.anchored_objects
    }

    /// Get last detected poses.
    #[must_use]
    pub fn last_poses(&self) -> &[MarkerPose] {
        &self.last_poses
    }
}

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

    fn make_test_image(w: usize, h: usize) -> Vec<u8> {
        // Black image with a white 20×20 square at (10,10)
        let mut img = vec![0u8; w * h * 3];
        for y in 10..30 {
            for x in 10..30 {
                if x < w && y < h {
                    let idx = (y * w + x) * 3;
                    img[idx] = 255;
                    img[idx + 1] = 255;
                    img[idx + 2] = 255;
                }
            }
        }
        img
    }

    #[test]
    fn test_ar_overlay_creation() {
        let ar = ArOverlay::new();
        assert!(ar.is_ok());
    }

    #[test]
    fn test_ar_overlay_with_config() {
        let config = ArOverlayConfig {
            dictionary: MarkerDictionary::Aruco6x6_250,
            marker_size_m: 0.2,
            min_marker_area_px: 200.0,
            max_markers: 8,
            overlay_alpha: 0.8,
        };
        let ar = ArOverlay::with_config(config);
        assert!(ar.is_ok());
    }

    #[test]
    fn test_add_and_remove_object() {
        let mut ar = ArOverlay::new().expect("should create");
        ar.add_object(AnchoredObject::new("cube", 0));
        ar.add_object(AnchoredObject::new("sphere", 1));
        assert_eq!(ar.objects().len(), 2);

        ar.remove_object("cube");
        assert_eq!(ar.objects().len(), 1);
        assert_eq!(ar.objects()[0].name, "sphere");
    }

    #[test]
    fn test_process_frame_empty_image() {
        let mut ar = ArOverlay::new().expect("should create");
        let intrinsics = CameraIntrinsics::from_image_size(64, 64);
        let img = vec![0u8; 64 * 64 * 3];
        let poses = ar.process_frame(&img, 64, 64, &intrinsics);
        assert!(poses.is_ok());
        assert_eq!(poses.expect("ok").len(), 0);
    }

    #[test]
    fn test_process_frame_with_marker() {
        let mut ar = ArOverlay::new().expect("should create");
        let intrinsics = CameraIntrinsics::from_image_size(64, 64);
        let img = make_test_image(64, 64);
        let poses = ar.process_frame(&img, 64, 64, &intrinsics);
        assert!(poses.is_ok());
        // Should detect at least one marker
        let poses = poses.expect("ok");
        assert!(!poses.is_empty(), "should detect the white square marker");
    }

    #[test]
    fn test_process_frame_size_mismatch() {
        let mut ar = ArOverlay::new().expect("should create");
        let intrinsics = CameraIntrinsics::from_image_size(64, 64);
        let bad_img = vec![0u8; 10]; // wrong size
        let result = ar.process_frame(&bad_img, 64, 64, &intrinsics);
        assert!(result.is_err());
    }

    #[test]
    fn test_frame_count_increments() {
        let mut ar = ArOverlay::new().expect("should create");
        let intrinsics = CameraIntrinsics::from_image_size(32, 32);
        let img = vec![0u8; 32 * 32 * 3];
        assert_eq!(ar.frame_count(), 0);
        ar.process_frame(&img, 32, 32, &intrinsics)
            .expect("should succeed");
        ar.process_frame(&img, 32, 32, &intrinsics)
            .expect("should succeed");
        assert_eq!(ar.frame_count(), 2);
    }

    #[test]
    fn test_composite_overlay() {
        let mut ar = ArOverlay::new().expect("should create");
        let intrinsics = CameraIntrinsics::from_image_size(64, 64);
        let img = make_test_image(64, 64);
        ar.process_frame(&img, 64, 64, &intrinsics)
            .expect("should succeed");

        let result = ar.composite_overlay(&img, 64, 64);
        assert!(result.is_ok());
        let rgba = result.expect("ok");
        assert_eq!(rgba.len(), 64 * 64 * 4);
    }

    #[test]
    fn test_composite_overlay_size_mismatch() {
        let ar = ArOverlay::new().expect("should create");
        let bad_img = vec![0u8; 10];
        let result = ar.composite_overlay(&bad_img, 64, 64);
        assert!(result.is_err());
    }

    #[test]
    fn test_marker_pose_centroid() {
        let corners = [
            Point2f::new(0.0, 0.0),
            Point2f::new(10.0, 0.0),
            Point2f::new(10.0, 10.0),
            Point2f::new(0.0, 10.0),
        ];
        let pose = MarkerPose::new(0, corners);
        let centroid = pose.centroid();
        assert!((centroid.x - 5.0).abs() < 1e-5);
        assert!((centroid.y - 5.0).abs() < 1e-5);
    }

    #[test]
    fn test_marker_pose_pixel_size() {
        let corners = [
            Point2f::new(0.0, 0.0),
            Point2f::new(10.0, 0.0),
            Point2f::new(10.0, 10.0),
            Point2f::new(0.0, 10.0),
        ];
        let pose = MarkerPose::new(0, corners);
        let size = pose.pixel_size();
        assert!(
            (size - 10.0).abs() < 1e-4,
            "pixel size should be 10: {size}"
        );
    }

    #[test]
    fn test_anchored_object_world_position_identity() {
        let obj = AnchoredObject::new("cube", 0).with_offset(1.0, 0.0, 0.0);
        let pose = MarkerPose::new(
            0,
            [
                Point2f::new(0.0, 0.0),
                Point2f::new(1.0, 0.0),
                Point2f::new(1.0, 1.0),
                Point2f::new(0.0, 1.0),
            ],
        );
        // rotation = identity, translation = [2,3,4]
        let mut p = pose;
        p.translation = [2.0, 3.0, 4.0];
        let world = obj.world_position(&p);
        // offset [1,0,0] rotated by identity + [2,3,4] = [3,3,4]
        assert!((world[0] - 3.0).abs() < 1e-9);
        assert!((world[1] - 3.0).abs() < 1e-9);
        assert!((world[2] - 4.0).abs() < 1e-9);
    }

    #[test]
    fn test_visible_object_positions_no_poses() {
        let mut ar = ArOverlay::new().expect("should create");
        ar.add_object(AnchoredObject::new("cube", 42));
        // No frames processed, no poses → should return empty
        let positions = ar.visible_object_positions();
        assert!(positions.is_empty());
    }

    #[test]
    fn test_visible_object_positions_with_detected_marker() {
        let mut ar = ArOverlay::new().expect("should create");
        let intrinsics = CameraIntrinsics::from_image_size(64, 64);
        let img = make_test_image(64, 64);
        let poses = ar
            .process_frame(&img, 64, 64, &intrinsics)
            .expect("should succeed");

        if let Some(first_pose) = poses.first() {
            ar.add_object(AnchoredObject::new("cube", first_pose.id));
            let positions = ar.visible_object_positions();
            assert!(!positions.is_empty());
        }
    }

    #[test]
    fn test_camera_intrinsics_from_image_size() {
        let intr = CameraIntrinsics::from_image_size(1920, 1080);
        assert!((intr.cx - 960.0).abs() < 1e-6);
        assert!((intr.cy - 540.0).abs() < 1e-6);
        assert!(intr.fx > 0.0);
    }

    #[test]
    fn test_anchored_object_builder() {
        let obj = AnchoredObject::new("box", 5)
            .with_offset(0.1, 0.2, 0.3)
            .with_scale(2.0)
            .with_visible(false);
        assert_eq!(obj.marker_id, 5);
        assert!((obj.offset[0] - 0.1).abs() < 1e-9);
        assert!((obj.scale - 2.0).abs() < 1e-9);
        assert!(!obj.visible);
    }

    #[test]
    fn test_multiple_markers_detected() {
        // Create an image with two separated white squares
        let w = 128usize;
        let h = 64usize;
        let mut img = vec![0u8; w * h * 3];
        for y in 5..25 {
            for x in 5..25 {
                let idx = (y * w + x) * 3;
                img[idx] = 255;
                img[idx + 1] = 255;
                img[idx + 2] = 255;
            }
        }
        for y in 5..25 {
            for x in 80..100 {
                let idx = (y * w + x) * 3;
                img[idx] = 255;
                img[idx + 1] = 255;
                img[idx + 2] = 255;
            }
        }

        let mut ar = ArOverlay::new().expect("should create");
        let intrinsics = CameraIntrinsics::from_image_size(w, h);
        let poses = ar
            .process_frame(&img, w, h, &intrinsics)
            .expect("should succeed");
        assert!(poses.len() >= 2, "expected ≥2 markers, got {}", poses.len());
    }
}