rustial-engine 0.0.1

use super::*;

impl MapState {
    /// Run just the terrain update (used by tests and manual pipelines).
    pub fn update_terrain(&mut self) {
        if self.terrain.enabled() {
            let cam_world = self.mercator_camera_world();
            let meshes = self.terrain.update(
                &self.viewport_bounds,
                self.zoom_level,
                cam_world,
                self.camera.projection(),
                self.camera.distance(),
                self.camera.pitch(),
            );
            self.terrain_meshes = Arc::new(meshes);
            self.hillshade_rasters = Arc::new(self.terrain.visible_hillshade_rasters().to_vec());

            // Report terrain DEM demand to the coordinator.
            self.request_coordinator
                .report_demand(SourcePriority::Terrain, self.terrain.pending_count());
        }
    }

    /// Determine the terrain tile set for the current frame.
    ///
    /// In steep-pitch terrain views, terrain should cover both the tile layer's
    /// selected raster targets and the stricter uncapped terrain footprint so
    /// mesh coverage does not clip at the frustum edge.
    ///
    /// When the camera is highly pitched the visible ground stretches far
    /// toward the horizon.  To avoid abrupt clipping where terrain tiles
    /// end, we supplement the base-zoom tiles with progressively coarser
    /// "horizon fill" tiles at lower zooms.
    pub(super) fn desired_terrain_tiles(&self) -> Option<Vec<rustial_math::TileId>> {
        let use_covering = self.terrain.enabled()
            && self.camera.pitch() > 0.3
            && self.camera.mode() == crate::camera::CameraMode::Perspective;

        if !use_covering || self.visible_tiles.is_empty() {
            return None;
        }

        // Build a set of all raster tile actuals (with loaded data) so we
        // can verify that every candidate terrain tile has an ancestor
        // with a raster texture available.  This prevents spawning terrain
        // meshes that would render with the white placeholder because the
        // covering algorithm did not select a raster tile for that area
        // (e.g. tiles in the viewport-overscan zone beyond the frustum).
        let raster_actuals: HashSet<TileId> = self
            .visible_tiles
            .iter()
            .filter(|vt| vt.data.is_some())
            .map(|vt| vt.actual)
            .collect();

        let has_raster_ancestor = |tile: &TileId| -> bool {
            // Exact match among raster targets.
            if raster_actuals.contains(tile) {
                return true;
            }
            // Walk up the parent chain looking for a loaded ancestor.
            let mut current = *tile;
            for _ in 0..8u8 {
                let Some(parent) = current.parent() else {
                    break;
                };
                if raster_actuals.contains(&parent) {
                    return true;
                }
                current = parent;
            }
            false
        };

        let mut terrain_tiles: Vec<rustial_math::TileId> =
            self.visible_tiles.iter().map(|tile| tile.target).collect();

        let strict_tiles = if let Some(view) = self.camera.flat_tile_view() {
            visible_tiles_flat_view_with_config(
                &self.viewport_bounds,
                self.zoom_level,
                &view,
                &FlatTileSelectionConfig {
                    footprint_pitch_threshold_rad: 0.0,
                    footprint_min_tiles: 0,
                    ..FlatTileSelectionConfig::default()
                },
            )
        } else {
            visible_tiles(&self.viewport_bounds, self.zoom_level)
        };

        let mut seen = HashSet::with_capacity(terrain_tiles.len() + strict_tiles.len());
        terrain_tiles.retain(|tile| seen.insert(*tile));
        for tile in strict_tiles {
            if seen.insert(tile) && has_raster_ancestor(&tile) {
                terrain_tiles.push(tile);
            }
        }

        // Near-field guarantee: at steep pitch the footprint polygon can
        // clip tiles at the bottom viewport corners. Ensure tiles around
        // the camera eye's ground projection are always included so the
        // near-field terrain is never missing.
        if self.camera.pitch() > 0.4 {
            let target_world = self.camera.target_world();
            let eye = target_world + self.camera.eye_offset();
            let eye_ground = WorldCoord::new(eye.x, eye.y, 0.0);

            // Radius proportional to the camera altitude, covering at
            // least a few tiles in every direction below the eye.
            let altitude = (eye.z - target_world.z).abs().max(1.0);
            let half = altitude * 1.5;
            let near_bounds = WorldBounds::new(
                WorldCoord::new(
                    eye_ground.position.x - half,
                    eye_ground.position.y - half,
                    0.0,
                ),
                WorldCoord::new(
                    eye_ground.position.x + half,
                    eye_ground.position.y + half,
                    0.0,
                ),
            );
            for tile in visible_tiles(&near_bounds, self.zoom_level) {
                if seen.insert(tile) && has_raster_ancestor(&tile) {
                    terrain_tiles.push(tile);
                }
            }
        }

        let cam = self.mercator_camera_world();

        // Cap base-zoom terrain tiles, keeping closest first. The cap
        // must not fall below the strict footprint or steep views will
        // visibly clip terrain against the lower raster layer.
        let max_base_tiles = terrain_base_tile_budget(terrain_tiles.len());
        if terrain_tiles.len() > max_base_tiles {
            terrain_tiles.sort_by(|a, b| {
                let da = tile_center_dist_sq(a, cam);
                let db = tile_center_dist_sq(b, cam);
                da.partial_cmp(&db).unwrap_or(std::cmp::Ordering::Equal)
            });
            terrain_tiles.truncate(max_base_tiles);
        }

        // Horizon fill: at steep pitch, add coarser tiles to cover the
        // distant ground that base-zoom tiles don't reach.  Each step
        // reduces zoom by 2, so a single tile covers 4× the area.
        // Only non-overlapping tiles are added (tiles that are NOT
        // ancestors of any existing tile).
        if self.camera.pitch() > 0.5 && self.zoom_level > 2 {
            let base_tiles: Vec<TileId> = terrain_tiles.clone();
            let is_ancestor_of_existing = |candidate: &TileId| -> bool {
                base_tiles.iter().any(|t| {
                    if t.zoom <= candidate.zoom {
                        return false;
                    }
                    let dz = t.zoom - candidate.zoom;
                    (t.x >> dz) == candidate.x && (t.y >> dz) == candidate.y
                })
            };
            let mut horizon_budget =
                terrain_horizon_tile_budget(max_base_tiles, self.camera.pitch());
            let mut hz = self.zoom_level.saturating_sub(2);
            while hz > 0 && horizon_budget > 0 {
                let coarse = visible_tiles(&self.viewport_bounds, hz);
                let mut coarse_sorted: Vec<_> = coarse
                    .into_iter()
                    .filter(|t| {
                        !seen.contains(t) && !is_ancestor_of_existing(t) && has_raster_ancestor(t)
                    })
                    .map(|t| {
                        let d = tile_center_dist_sq(&t, cam);
                        (t, d)
                    })
                    .collect();
                // Farthest first — fill the horizon end.
                coarse_sorted
                    .sort_by(|a, b| b.1.partial_cmp(&a.1).unwrap_or(std::cmp::Ordering::Equal));
                let take = coarse_sorted.len().min(horizon_budget);
                for (t, _) in coarse_sorted.into_iter().take(take) {
                    if seen.insert(t) {
                        terrain_tiles.push(t);
                        horizon_budget -= 1;
                    }
                }
                hz = hz.saturating_sub(2);
            }
        }

        Some(terrain_tiles)
    }

    /// Run the terrain update using a pre-computed tile set from the tile
    /// layer's covering-tiles selection.  This ensures the terrain manager
    /// generates meshes for exactly the same tiles that have raster textures
    /// available, preventing untextured grey patches.
    pub(super) fn update_terrain_with_tiles(&mut self, tiles: &[rustial_math::TileId]) {
        if self.terrain.enabled() {
            let meshes =
                self.terrain
                    .update_with_tiles(tiles, self.zoom_level, self.camera.projection());
            self.terrain_meshes = Arc::new(meshes);
            self.hillshade_rasters = Arc::new(self.terrain.visible_hillshade_rasters().to_vec());

            // Report terrain DEM demand to the coordinator.
            self.request_coordinator
                .report_demand(SourcePriority::Terrain, self.terrain.pending_count());
        }
    }

    /// Lightweight per-frame tile layer update: poll completed HTTP
    /// responses, recompute the visible tile set for the current camera
    /// position, and issue new tile requests.
    ///
    /// This is separated from the heavier terrain/vector/symbol/model
    /// processing so it can run unconditionally every frame, even during
    /// animation when the heavy layers are throttled.
    pub(super) fn update_tile_layers(&mut self) {
        use crate::layer::LayerKind;
        use crate::layers::TileLayer;

        // Begin a new coordinator frame so per-source budgets are
        // allocated from the global cap before any source updates.
        self.request_coordinator.begin_frame();

        let zoom_level = self.zoom_level;
        let camera_world = self.mercator_camera_world();
        let flat_view = self.camera.flat_tile_view();
        let camera_distance = self.camera.distance();
        let viewport_bounds = self.viewport_bounds;
        let predicted_viewport_bounds = *self.predicted_viewport_bounds();
        let predicted_target_world = self.camera_motion_state.predicted_target_world;
        let should_speculatively_prefetch =
            self.camera_motion_state.pan_velocity_world.length_squared() > 1e-9;
        let zoom_prefetch_direction = zoom_prefetch_direction(self.camera_zoom_delta);
        let prefetch_route = self.prefetch_route.clone();

        let use_covering = self.terrain.enabled()
            && self.camera.pitch() > 0.3
            && self.camera.mode() == crate::camera::CameraMode::Perspective;

        let covering_params = if use_covering {
            let fzoom = self.fractional_zoom();
            self.camera.covering_camera(fzoom).map(|cam| {
                let opts = rustial_math::CoveringTilesOptions {
                    min_zoom: 0,
                    max_zoom: rustial_math::MAX_ZOOM,
                    round_zoom: false,
                    tile_size: 256,
                    max_tiles: 512,
                    allow_variable_zoom: true,
                    render_world_copies: true,
                };
                (cam, opts)
            })
        } else {
            None
        };

        // -- Raster tile layers -------------------------------------------

        // Apply the coordinator's raster budget to each tile layer.
        let raster_budget = self.request_coordinator.budget_for(SourcePriority::Raster);

        for layer in self.layers.iter_mut() {
            if !layer.visible() {
                continue;
            }
            if layer.kind() == LayerKind::Tile {
                if let Some(tile_layer) = layer.as_any_mut().downcast_mut::<TileLayer>() {
                    // Temporarily apply the coordinator's per-frame budget.
                    let mut sel = tile_layer.selection_config().clone();
                    sel.max_requests_per_frame = raster_budget;
                    tile_layer.set_selection_config(sel);

                    if let (Some(frustum), Some((ref cam, ref opts))) =
                        (self.frustum.as_ref(), covering_params.as_ref())
                    {
                        tile_layer.update_with_covering(frustum, cam, opts, camera_world);
                    } else {
                        tile_layer.update_with_view(
                            &viewport_bounds,
                            zoom_level,
                            camera_world,
                            camera_distance,
                            flat_view.as_ref(),
                        );
                    }

                    // Report raster results to the coordinator.
                    let stats = tile_layer.last_selection_stats();
                    let desired: HashSet<TileId> = tile_layer
                        .visible_tiles()
                        .tiles
                        .iter()
                        .map(|t| t.target)
                        .collect();
                    let mut total_raster_requested = stats.requested_tiles;
                    let raster_pending_demand =
                        stats.fallback_visible_tiles + stats.missing_visible_tiles;
                    let mut remaining_speculative_budget =
                        speculative_prefetch_budget(raster_budget, stats.requested_tiles);

                    // 1. Viewport-prediction prefetch (pan momentum).
                    if remaining_speculative_budget > 0 && should_speculatively_prefetch {
                        let prefetched = tile_layer.prefetch_with_view(
                            &predicted_viewport_bounds,
                            zoom_level,
                            (predicted_target_world.x, predicted_target_world.y),
                            None,
                            remaining_speculative_budget,
                        );
                        total_raster_requested += prefetched;
                        remaining_speculative_budget =
                            remaining_speculative_budget.saturating_sub(prefetched);
                    }

                    // 2. Zoom-direction prefetch.
                    if remaining_speculative_budget > 0 {
                        if let Some(direction) = zoom_prefetch_direction {
                            let prefetched = tile_layer.prefetch_zoom_direction(
                                camera_world,
                                direction,
                                remaining_speculative_budget,
                            );
                            total_raster_requested += prefetched;
                            remaining_speculative_budget =
                                remaining_speculative_budget.saturating_sub(prefetched);
                        }
                    }

                    // 3. Route-aware prefetch.
                    if remaining_speculative_budget > 0 {
                        if let Some(ref route) = prefetch_route {
                            let prefetched = tile_layer.prefetch_route(
                                route,
                                zoom_level,
                                camera_world,
                                remaining_speculative_budget,
                            );
                            total_raster_requested += prefetched;
                        }
                    }

                    self.request_coordinator.report(
                        SourcePriority::Raster,
                        desired,
                        total_raster_requested,
                        raster_pending_demand,
                    );

                    self.visible_tiles = Arc::new(tile_layer.visible_tiles().tiles.clone());
                }
            }
        }

        // -- Streamed vector source layers --------------------------------

        self.update_streamed_vector_source_layers(
            zoom_level,
            camera_world,
            camera_distance,
            &viewport_bounds,
            flat_view.as_ref(),
            covering_params.as_ref(),
        );

        // Finish the coordinator frame and compute cross-source stats.
        self.request_coordinator.finish_frame();
    }

    pub(super) fn update_streamed_vector_source_layers(
        &mut self,
        zoom_level: u8,
        camera_world: (f64, f64),
        camera_distance: f64,
        viewport_bounds: &WorldBounds,
        flat_view: Option<&rustial_math::FlatTileView>,
        covering_params: Option<&(
            rustial_math::CoveringCamera,
            rustial_math::CoveringTilesOptions,
        )>,
    ) {
        // Apply the coordinator's vector budget to each streamed source.
        // The budget is shared across all vector sources (split evenly).
        let vector_budget = self.request_coordinator.budget_for(SourcePriority::Vector);
        let source_count = self.streamed_vector_sources.len().max(1);
        let per_source_budget = if vector_budget == usize::MAX {
            usize::MAX
        } else {
            // Give each vector source a fair share of the vector budget.
            (vector_budget / source_count).max(1)
        };

        let mut total_vector_requested = 0usize;
        let mut all_vector_desired = HashSet::new();
        let predicted_viewport_bounds = *self.predicted_viewport_bounds();
        let predicted_target_world = self.camera_motion_state.predicted_target_world;
        let should_speculatively_prefetch =
            self.camera_motion_state.pan_velocity_world.length_squared() > 1e-9;
        let zoom_prefetch_direction = zoom_prefetch_direction(self.camera_zoom_delta);
        let prefetch_route = self.prefetch_route.clone();

        for source_layer in self.streamed_vector_sources.values_mut() {
            // Temporarily apply the coordinator's per-source budget.
            let mut sel = source_layer.selection_config().clone();
            sel.max_requests_per_frame = per_source_budget;
            source_layer.set_selection_config(sel);

            if let (Some(frustum), Some((cam, opts))) = (self.frustum.as_ref(), covering_params) {
                source_layer.update_with_covering(frustum, cam, opts, camera_world);
            } else {
                source_layer.update_with_view(
                    viewport_bounds,
                    zoom_level,
                    camera_world,
                    camera_distance,
                    flat_view,
                );
            }

            // Accumulate vector stats for the coordinator.
            let stats = source_layer.last_selection_stats();
            total_vector_requested += stats.requested_tiles;
            for tile in source_layer.visible_tiles().tiles.iter() {
                all_vector_desired.insert(tile.target);
            }

            let mut remaining_speculative_budget =
                speculative_prefetch_budget(per_source_budget, stats.requested_tiles);

            // 1. Viewport-prediction prefetch (pan momentum).
            if remaining_speculative_budget > 0 && should_speculatively_prefetch {
                let prefetched = source_layer.prefetch_with_view(
                    &predicted_viewport_bounds,
                    zoom_level,
                    (predicted_target_world.x, predicted_target_world.y),
                    None,
                    remaining_speculative_budget,
                );
                total_vector_requested += prefetched;
                remaining_speculative_budget =
                    remaining_speculative_budget.saturating_sub(prefetched);
            }

            // 2. Zoom-direction prefetch.
            if remaining_speculative_budget > 0 {
                if let Some(direction) = zoom_prefetch_direction {
                    let prefetched = source_layer.prefetch_zoom_direction(
                        camera_world,
                        direction,
                        remaining_speculative_budget,
                    );
                    total_vector_requested += prefetched;
                    remaining_speculative_budget =
                        remaining_speculative_budget.saturating_sub(prefetched);
                }
            }

            // 3. Route-aware prefetch.
            if remaining_speculative_budget > 0 {
                if let Some(ref route) = prefetch_route {
                    let prefetched = source_layer.prefetch_route(
                        route,
                        zoom_level,
                        camera_world,
                        remaining_speculative_budget,
                    );
                    total_vector_requested += prefetched;
                }
            }
        }

        // Report aggregate vector results.
        self.request_coordinator.report(
            SourcePriority::Vector,
            all_vector_desired,
            total_vector_requested,
            total_vector_requested,
        );
    }
}

/// Squared distance from the centre of a tile to a camera world position.
fn tile_center_dist_sq(tile: &rustial_math::TileId, cam: (f64, f64)) -> f64 {
    let b = rustial_math::tile_bounds_world(tile);
    let cx = (b.min.position.x + b.max.position.x) * 0.5;
    let cy = (b.min.position.y + b.max.position.y) * 0.5;
    let dx = cx - cam.0;
    let dy = cy - cam.1;
    dx * dx + dy * dy
}

fn speculative_prefetch_budget(total_budget: usize, visible_requests: usize) -> usize {
    if total_budget == 0 {
        return 0;
    }

    if total_budget == usize::MAX {
        return DEFAULT_SPECULATIVE_PREFETCH_REQUEST_BUDGET;
    }

    let remaining = total_budget.saturating_sub(visible_requests);
    if remaining == 0 {
        return 0;
    }

    let speculative_cap =
        ((total_budget as f64) * SPECULATIVE_PREFETCH_BUDGET_FRACTION).ceil() as usize;
    remaining.min(speculative_cap.max(1))
}

fn zoom_prefetch_direction(zoom_delta: f64) -> Option<ZoomPrefetchDirection> {
    if zoom_delta > ZOOM_DIRECTION_PREFETCH_THRESHOLD {
        Some(ZoomPrefetchDirection::In)
    } else if zoom_delta < -ZOOM_DIRECTION_PREFETCH_THRESHOLD {
        Some(ZoomPrefetchDirection::Out)
    } else {
        None
    }
}