rustial-engine 0.0.1

//! Dynamic image overlay layer — a georeferenced overlay with
//! frame-provider–driven content updates.
//!
//! This is the Rustial equivalent of MapLibre / Mapbox `video` and
//! `canvas` source types.  Rather than wrapping a DOM `<video>` or
//! `<canvas>` element, the layer holds a [`FrameProvider`] trait object
//! that supplies new RGBA8 frames on demand.
//!
//! ## Data flow
//!
//! ```text
//! FrameProvider::next_frame()
//!     |
//!     v
//! DynamicImageOverlayLayer   (holds latest frame + generation)
//!     |
//!     v
//! collect_image_overlays()   (polls provider, emits ImageOverlayData)
//!     |
//!     v
//! FrameOutput::image_overlays   (renderer consumes as textured quads)
//! ```
//!
//! ## Usage
//!
//! ```rust,ignore
//! use rustial_engine::{DynamicImageOverlayLayer, FrameProvider, FrameData, GeoCoord};
//!
//! struct TestProvider;
//! impl FrameProvider for TestProvider {
//!     fn next_frame(&mut self) -> Option<FrameData> {
//!         Some(FrameData {
//!             width: 64,
//!             height: 64,
//!             data: vec![255u8; 64 * 64 * 4],
//!         })
//!     }
//! }
//!
//! let corners = [
//!     GeoCoord::from_lat_lon(40.0, -74.0),
//!     GeoCoord::from_lat_lon(40.0, -73.0),
//!     GeoCoord::from_lat_lon(39.0, -73.0),
//!     GeoCoord::from_lat_lon(39.0, -74.0),
//! ];
//! let layer = DynamicImageOverlayLayer::new("video-feed", corners, Box::new(TestProvider));
//! ```

use crate::camera_projection::CameraProjection;
use crate::layer::{Layer, LayerId, LayerKind};
use crate::layers::image_overlay_layer::ImageOverlayData;
use rustial_math::GeoCoord;
use std::any::Any;
use std::sync::Arc;

// ---------------------------------------------------------------------------
// FrameProvider trait
// ---------------------------------------------------------------------------

/// A single RGBA8 frame returned by a [`FrameProvider`].
#[derive(Debug, Clone)]
pub struct FrameData {
    /// Image width in pixels.
    pub width: u32,
    /// Image height in pixels.
    pub height: u32,
    /// RGBA8 pixel data (length must equal `width * height * 4`).
    pub data: Vec<u8>,
}

/// Trait for dynamic frame sources (video decoders, canvas renderers,
/// procedural generators, etc.).
///
/// Implementations supply RGBA8 frames to a
/// [`DynamicImageOverlayLayer`].  The engine polls [`next_frame`] once
/// per frame while the layer is visible and [`is_animating`] returns
/// `true`.
///
/// [`next_frame`]: FrameProvider::next_frame
/// [`is_animating`]: FrameProvider::is_animating
pub trait FrameProvider: Send + Sync {
    /// Poll for the next frame.
    ///
    /// Return `Some(FrameData)` when new pixel data is available, or
    /// `None` to keep the previous frame.
    fn next_frame(&mut self) -> Option<FrameData>;

    /// Whether this source is currently animating.
    ///
    /// When `false`, the engine skips polling [`next_frame`] until
    /// the flag changes.  Defaults to `true`.
    ///
    /// [`next_frame`]: FrameProvider::next_frame
    fn is_animating(&self) -> bool {
        true
    }
}

/// A closure-based [`FrameProvider`] for convenience.
///
/// Wraps any `FnMut() -> Option<FrameData>` as a frame provider.
pub struct CallbackFrameProvider<F> {
    callback: F,
    animating: bool,
}

impl<F: FnMut() -> Option<FrameData> + Send + Sync> CallbackFrameProvider<F> {
    /// Create a new callback-based frame provider.
    pub fn new(callback: F) -> Self {
        Self {
            callback,
            animating: true,
        }
    }

    /// Set whether the provider is currently animating.
    pub fn set_animating(&mut self, animating: bool) {
        self.animating = animating;
    }
}

impl<F: FnMut() -> Option<FrameData> + Send + Sync> FrameProvider for CallbackFrameProvider<F> {
    fn next_frame(&mut self) -> Option<FrameData> {
        (self.callback)()
    }

    fn is_animating(&self) -> bool {
        self.animating
    }
}

/// Factory type for creating [`FrameProvider`] instances.
///
/// Used by [`VideoSource`](crate::style::VideoSource) and
/// [`CanvasSource`](crate::style::CanvasSource) in the style system to
/// produce frame providers when a style document is applied.
pub type FrameProviderFactory = Arc<dyn Fn() -> Box<dyn FrameProvider> + Send + Sync>;

// ---------------------------------------------------------------------------
// DynamicImageOverlayLayer
// ---------------------------------------------------------------------------

/// A georeferenced overlay with dynamic frame content.
///
/// This is the Rustial equivalent of MapLibre / Mapbox `video` and
/// `canvas` source types.  A [`FrameProvider`] supplies RGBA8 frames
/// which are rendered as a textured quad at the specified geographic
/// coordinates.
///
/// The layer caches the most recent frame and tracks a generation
/// counter for change detection.  Renderers see this layer through
/// the same [`ImageOverlayData`] path as [`ImageOverlayLayer`],
/// so no renderer changes are required.
///
/// [`ImageOverlayLayer`]: crate::layers::ImageOverlayLayer
pub struct DynamicImageOverlayLayer {
    id: LayerId,
    name: String,
    visible: bool,
    opacity: f32,
    /// Geographic corner coordinates (TL, TR, BR, BL).
    coordinates: [GeoCoord; 4],
    /// Cached frame dimensions.
    width: u32,
    height: u32,
    /// Cached RGBA8 pixel data from the last provider frame.
    data: Arc<Vec<u8>>,
    /// Monotonically increasing generation counter.
    generation: u64,
    /// Whether the first frame has been received.
    has_frame: bool,
    /// The frame provider that supplies dynamic content.
    provider: Box<dyn FrameProvider>,
}

impl std::fmt::Debug for DynamicImageOverlayLayer {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        f.debug_struct("DynamicImageOverlayLayer")
            .field("id", &self.id)
            .field("name", &self.name)
            .field("visible", &self.visible)
            .field("opacity", &self.opacity)
            .field("width", &self.width)
            .field("height", &self.height)
            .field("has_frame", &self.has_frame)
            .field("generation", &self.generation)
            .field("animating", &self.provider.is_animating())
            .finish()
    }
}

impl DynamicImageOverlayLayer {
    /// Create a new dynamic image overlay layer.
    ///
    /// `coordinates` must be in TL → TR → BR → BL order.
    pub fn new(
        name: impl Into<String>,
        coordinates: [GeoCoord; 4],
        provider: Box<dyn FrameProvider>,
    ) -> Self {
        Self {
            id: LayerId::next(),
            name: name.into(),
            visible: true,
            opacity: 1.0,
            coordinates,
            width: 0,
            height: 0,
            data: Arc::new(Vec::new()),
            generation: 0,
            has_frame: false,
            provider,
        }
    }

    /// Geographic corners (TL, TR, BR, BL).
    #[inline]
    pub fn coordinates(&self) -> &[GeoCoord; 4] {
        &self.coordinates
    }

    /// Update the geographic corners.
    pub fn set_coordinates(&mut self, coordinates: [GeoCoord; 4]) {
        self.coordinates = coordinates;
        self.generation = self.generation.wrapping_add(1);
    }

    /// Monotonic generation counter, bumped on coordinate or frame changes.
    #[inline]
    pub fn generation(&self) -> u64 {
        self.generation
    }

    /// Cached frame dimensions `(width, height)`.
    #[inline]
    pub fn dimensions(&self) -> (u32, u32) {
        (self.width, self.height)
    }

    /// Whether at least one frame has been received.
    #[inline]
    pub fn has_frame(&self) -> bool {
        self.has_frame
    }

    /// Poll the frame provider for new data.
    ///
    /// Returns `true` if a new frame was received and the cached data
    /// was updated.
    pub fn poll_frame(&mut self) -> bool {
        if !self.provider.is_animating() {
            return false;
        }
        if let Some(frame) = self.provider.next_frame() {
            debug_assert_eq!(
                frame.data.len(),
                (frame.width * frame.height * 4) as usize,
                "FrameData RGBA8 length must equal width * height * 4"
            );
            self.width = frame.width;
            self.height = frame.height;
            self.data = Arc::new(frame.data);
            self.generation = self.generation.wrapping_add(1);
            self.has_frame = true;
            true
        } else {
            false
        }
    }

    /// Produce renderer-ready overlay data by projecting geographic
    /// corners into the active world-space coordinate system.
    ///
    /// Returns `None` if no frame has been received yet.
    pub fn to_overlay_data(&self, projection: CameraProjection) -> Option<ImageOverlayData> {
        if !self.has_frame || self.width == 0 || self.height == 0 {
            return None;
        }
        let corners = [
            project_corner(&self.coordinates[0], projection),
            project_corner(&self.coordinates[1], projection),
            project_corner(&self.coordinates[2], projection),
            project_corner(&self.coordinates[3], projection),
        ];
        Some(ImageOverlayData {
            layer_id: self.id,
            corners,
            width: self.width,
            height: self.height,
            data: Arc::clone(&self.data),
            opacity: self.opacity,
        })
    }

    /// Access the underlying frame provider.
    pub fn provider(&self) -> &dyn FrameProvider {
        &*self.provider
    }

    /// Access the underlying frame provider mutably.
    pub fn provider_mut(&mut self) -> &mut dyn FrameProvider {
        &mut *self.provider
    }
}

fn project_corner(coord: &GeoCoord, projection: CameraProjection) -> [f64; 3] {
    let w = projection.project(coord);
    [w.position.x, w.position.y, w.position.z]
}

// ---------------------------------------------------------------------------
// Layer trait implementation
// ---------------------------------------------------------------------------

impl Layer for DynamicImageOverlayLayer {
    fn id(&self) -> LayerId {
        self.id
    }

    fn name(&self) -> &str {
        &self.name
    }

    fn kind(&self) -> LayerKind {
        LayerKind::Custom
    }

    fn visible(&self) -> bool {
        self.visible
    }

    fn set_visible(&mut self, visible: bool) {
        self.visible = visible;
    }

    fn opacity(&self) -> f32 {
        self.opacity
    }

    fn set_opacity(&mut self, opacity: f32) {
        self.opacity = opacity.clamp(0.0, 1.0);
    }

    fn as_any(&self) -> &dyn Any {
        self
    }

    fn as_any_mut(&mut self) -> &mut dyn Any {
        self
    }
}

// ---------------------------------------------------------------------------
// Tests
// ---------------------------------------------------------------------------

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

    struct CountingProvider {
        frame_count: u32,
        width: u32,
        height: u32,
    }

    impl CountingProvider {
        fn new(width: u32, height: u32) -> Self {
            Self {
                frame_count: 0,
                width,
                height,
            }
        }
    }

    impl FrameProvider for CountingProvider {
        fn next_frame(&mut self) -> Option<FrameData> {
            self.frame_count += 1;
            // Each frame has pixels filled with the frame count (mod 256).
            let fill = (self.frame_count % 256) as u8;
            Some(FrameData {
                width: self.width,
                height: self.height,
                data: vec![fill; (self.width * self.height * 4) as usize],
            })
        }
    }

    struct PausableProvider {
        animating: bool,
    }

    impl FrameProvider for PausableProvider {
        fn next_frame(&mut self) -> Option<FrameData> {
            Some(FrameData {
                width: 2,
                height: 2,
                data: vec![128; 16],
            })
        }

        fn is_animating(&self) -> bool {
            self.animating
        }
    }

    struct OneShotProvider {
        sent: bool,
    }

    impl FrameProvider for OneShotProvider {
        fn next_frame(&mut self) -> Option<FrameData> {
            if self.sent {
                None
            } else {
                self.sent = true;
                Some(FrameData {
                    width: 4,
                    height: 4,
                    data: vec![255; 64],
                })
            }
        }

        fn is_animating(&self) -> bool {
            !self.sent
        }
    }

    fn sample_corners() -> [GeoCoord; 4] {
        [
            GeoCoord::from_lat_lon(40.0, -74.0),
            GeoCoord::from_lat_lon(40.0, -73.0),
            GeoCoord::from_lat_lon(39.0, -73.0),
            GeoCoord::from_lat_lon(39.0, -74.0),
        ]
    }

    #[test]
    fn new_layer_starts_without_frame() {
        let layer = DynamicImageOverlayLayer::new(
            "test",
            sample_corners(),
            Box::new(CountingProvider::new(8, 8)),
        );
        assert!(!layer.has_frame());
        assert_eq!(layer.dimensions(), (0, 0));
        assert_eq!(layer.generation(), 0);
    }

    #[test]
    fn poll_frame_receives_first_frame() {
        let mut layer = DynamicImageOverlayLayer::new(
            "test",
            sample_corners(),
            Box::new(CountingProvider::new(8, 8)),
        );
        assert!(layer.poll_frame());
        assert!(layer.has_frame());
        assert_eq!(layer.dimensions(), (8, 8));
        assert_eq!(layer.generation(), 1);
    }

    #[test]
    fn consecutive_polls_bump_generation() {
        let mut layer = DynamicImageOverlayLayer::new(
            "test",
            sample_corners(),
            Box::new(CountingProvider::new(4, 4)),
        );
        layer.poll_frame();
        layer.poll_frame();
        layer.poll_frame();
        assert_eq!(layer.generation(), 3);
    }

    #[test]
    fn paused_provider_skips_poll() {
        let mut layer = DynamicImageOverlayLayer::new(
            "test",
            sample_corners(),
            Box::new(PausableProvider { animating: false }),
        );
        assert!(!layer.poll_frame());
        assert!(!layer.has_frame());
        assert_eq!(layer.generation(), 0);
    }

    #[test]
    fn one_shot_provider_stops_after_first() {
        let mut layer = DynamicImageOverlayLayer::new(
            "test",
            sample_corners(),
            Box::new(OneShotProvider { sent: false }),
        );
        assert!(layer.poll_frame());
        assert_eq!(layer.generation(), 1);
        // Provider is no longer animating.
        assert!(!layer.poll_frame());
        assert_eq!(layer.generation(), 1);
    }

    #[test]
    fn to_overlay_data_returns_none_without_frame() {
        let layer = DynamicImageOverlayLayer::new(
            "test",
            sample_corners(),
            Box::new(CountingProvider::new(4, 4)),
        );
        assert!(layer
            .to_overlay_data(CameraProjection::WebMercator)
            .is_none());
    }

    #[test]
    fn to_overlay_data_returns_some_after_poll() {
        let mut layer = DynamicImageOverlayLayer::new(
            "test",
            sample_corners(),
            Box::new(CountingProvider::new(4, 4)),
        );
        layer.poll_frame();
        let data = layer.to_overlay_data(CameraProjection::WebMercator);
        assert!(data.is_some());
        let data = data.unwrap();
        assert_eq!(data.width, 4);
        assert_eq!(data.height, 4);
        assert_eq!(data.data.len(), 64);
    }

    #[test]
    fn set_coordinates_bumps_generation() {
        let mut layer = DynamicImageOverlayLayer::new(
            "test",
            sample_corners(),
            Box::new(CountingProvider::new(4, 4)),
        );
        let g0 = layer.generation();
        layer.set_coordinates([
            GeoCoord::from_lat_lon(50.0, -75.0),
            GeoCoord::from_lat_lon(50.0, -74.0),
            GeoCoord::from_lat_lon(49.0, -74.0),
            GeoCoord::from_lat_lon(49.0, -75.0),
        ]);
        assert_eq!(layer.generation(), g0 + 1);
    }

    #[test]
    fn opacity_clamps_to_valid_range() {
        let mut layer = DynamicImageOverlayLayer::new(
            "test",
            sample_corners(),
            Box::new(CountingProvider::new(4, 4)),
        );
        layer.set_opacity(2.0);
        assert_eq!(layer.opacity(), 1.0);
        layer.set_opacity(-0.5);
        assert_eq!(layer.opacity(), 0.0);
    }

    #[test]
    fn callback_frame_provider_works() {
        let counter = std::sync::Arc::new(std::sync::atomic::AtomicU32::new(0));
        let counter_clone = counter.clone();
        let provider = CallbackFrameProvider::new(move || {
            let n = counter_clone.fetch_add(1, std::sync::atomic::Ordering::Relaxed);
            Some(FrameData {
                width: 2,
                height: 2,
                data: vec![(n % 256) as u8; 16],
            })
        });
        let mut layer = DynamicImageOverlayLayer::new("test", sample_corners(), Box::new(provider));
        layer.poll_frame();
        assert!(layer.has_frame());
        assert_eq!(counter.load(std::sync::atomic::Ordering::Relaxed), 1);
        layer.poll_frame();
        assert_eq!(counter.load(std::sync::atomic::Ordering::Relaxed), 2);
    }
}