//! Perception query trait (D-017).
//!
//! Abstraction for perception mode geometry computation. Each mode
//! (natural vision, thermal, EM, etc.) implements PerceptionQuery to
//! provide mode-specific FOV and visibility sector computation.
//! v0.1 implements only NaturalVision.
//!
//! Note: HashMap is used for `sector_lookup` — a per-frame scratch buffer
//! looked up only by key. Iteration order is irrelevant here. Not subject to
//! the simulation determinism constraint (see server/.clippy.toml).
//! Consumer contract: every consumer must sort (or otherwise impose a
//! deterministic order on) this data before it touches simulation state or
//! the wire.
#![allow(clippy::disallowed_types)]

use std::collections::{BTreeSet, HashMap};

use bevy_ecs::prelude::*;

use crate::bridge::types::{FacingDirection, TileKind, VisibilitySector, VisibleTile};
use crate::perception::shadowcast::compute_fov;
use crate::perception::vision_cone::{apply_vision_cone, VisionConeConfig};
use crate::simulation::movement::{TilePosition, WalkabilityMap};

/// Cached FOV geometry for the current frame. Produced by
/// compute_visibility_geometry, consumed by compute_observer_snapshot.
/// D-017 perception modes swap the geometry producer while the consumer
/// remains unchanged.
#[derive(Resource, Default)]
pub struct VisibilityGeometry {
    pub visible_tiles: Vec<VisibleTile>,
    pub visible_positions: BTreeSet<(i32, i32)>,
    pub sector_lookup: HashMap<(i32, i32), VisibilitySector>,
    pub observer_z: i32,
}

/// Trait for perception mode geometry computation (D-017).
///
/// Each perception mode implements this to produce a VisibilityGeometry
/// from the observer's position and facing. v0.1 only implements
/// NaturalVision; D-017 adds Thermal, EM, etc.
pub trait PerceptionQuery: Send + Sync {
    fn compute_geometry(
        &self,
        observer_pos: &TilePosition,
        facing: FacingDirection,
        walkability: &WalkabilityMap,
    ) -> VisibilityGeometry;
}

/// Natural vision — default perception mode.
/// Uses symmetric shadowcasting (D-011) + directional vision cone (D-015).
pub struct NaturalVision;

impl PerceptionQuery for NaturalVision {
    fn compute_geometry(
        &self,
        observer_pos: &TilePosition,
        facing: FacingDirection,
        walkability: &WalkabilityMap,
    ) -> VisibilityGeometry {
        let config = VisionConeConfig::default();
        let z = observer_pos.z;

        let fov = compute_fov(
            |x, y| !walkability.can_move_to(&TilePosition::new(x, y, z)),
            observer_pos.x,
            observer_pos.y,
            config.forward_range,
            z,
        );

        let cone_tiles = apply_vision_cone(&fov, observer_pos.x, observer_pos.y, facing, &config);

        let mut visible_tiles: Vec<VisibleTile> = cone_tiles
            .iter()
            .map(|&(x, y, sector)| {
                let tile_kind = if walkability.can_move_to(&TilePosition::new(x, y, z)) {
                    TileKind::Floor
                } else {
                    TileKind::Wall
                };
                VisibleTile {
                    x,
                    y,
                    z,
                    visibility: sector,
                    tile_kind,
                    zone_id: None,
                }
            })
            .collect();
        visible_tiles.sort_by_key(|t| (t.x, t.y));

        let visible_positions = cone_tiles.iter().map(|&(x, y, _)| (x, y)).collect();

        let sector_lookup = cone_tiles
            .iter()
            .map(|&(x, y, sector)| ((x, y), sector))
            .collect();

        // --- Boundary wall margin pass (#584) ---
        // Walk the LOS boundary and include non-walkable tiles 1 tile beyond.
        // This gives the client wall geometry at the fog edge.
        let boundary_walls = compute_boundary_walls(&visible_positions, walkability, z);
        for (bx, by) in &boundary_walls {
            visible_tiles.push(VisibleTile {
                x: *bx,
                y: *by,
                z,
                visibility: VisibilitySector::BoundaryWall,
                tile_kind: TileKind::Wall,
                zone_id: None,
            });
        }
        // Re-sort after adding boundary walls
        visible_tiles.sort_by_key(|t| (t.x, t.y));

        VisibilityGeometry {
            visible_tiles,
            visible_positions,
            sector_lookup,
            observer_z: z,
        }
    }
}

/// Compute wall tiles 1 tile beyond the LOS boundary (#584).
///
/// For each tile on the boundary of the visible set (has at least one
/// 4-neighbor outside the set), check each non-visible neighbor.
/// If that neighbor is not walkable, include it as a boundary wall.
///
/// Returns deduplicated (x, y) positions of wall tiles to add.
fn compute_boundary_walls(
    visible_positions: &BTreeSet<(i32, i32)>,
    walkability: &WalkabilityMap,
    z: i32,
) -> Vec<(i32, i32)> {
    const NEIGHBORS: [(i32, i32); 4] = [(0, -1), (0, 1), (-1, 0), (1, 0)];
    let mut walls = BTreeSet::new();

    for &(x, y) in visible_positions {
        for (dx, dy) in NEIGHBORS {
            let nx = x + dx;
            let ny = y + dy;
            if !visible_positions.contains(&(nx, ny)) {
                let pos = TilePosition::new(nx, ny, z);
                if !walkability.can_move_to(&pos) {
                    walls.insert((nx, ny));
                }
            }
        }
    }

    walls.into_iter().collect()
}

/// Resource wrapping the active perception mode (D-017).
/// Defaults to NaturalVision. Swap this resource to change perception modes.
#[derive(Resource)]
pub struct ActivePerceptionMode(pub Box<dyn PerceptionQuery>);

impl Default for ActivePerceptionMode {
    fn default() -> Self {
        Self(Box::new(NaturalVision))
    }
}

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

    /// Build a small walkability map with walls around the edges.
    /// Layout (5x5, z=0):
    ///   W W W W W
    ///   W F F F W
    ///   W F F F W
    ///   W F F F W
    ///   W W W W W
    fn make_walled_map() -> WalkabilityMap {
        let mut map = WalkabilityMap::new(5, 5, 1);
        // All tiles start walkable (floor). Set border to non-walkable (wall).
        for x in 0..5 {
            map.set_walkable(&TilePosition::new(x, 0, 0), false);
            map.set_walkable(&TilePosition::new(x, 4, 0), false);
        }
        for y in 0..5 {
            map.set_walkable(&TilePosition::new(0, y, 0), false);
            map.set_walkable(&TilePosition::new(4, y, 0), false);
        }
        map
    }

    #[test]
    fn boundary_walls_include_adjacent_walls() {
        // Visible set: just the center tile (2,2)
        let visible: BTreeSet<(i32, i32)> = [(2, 2)].into_iter().collect();
        let map = make_walled_map();
        let walls = compute_boundary_walls(&visible, &map, 0);

        // All 4 neighbors of (2,2) are floor tiles (walkable), so no walls.
        // This verifies we don't add walkable tiles as boundary walls.
        assert!(walls.is_empty());
    }

    #[test]
    fn boundary_walls_found_at_edge() {
        // Visible set: tiles along the north interior edge (y=1)
        let visible: BTreeSet<(i32, i32)> = [(1, 1), (2, 1), (3, 1)].into_iter().collect();
        let map = make_walled_map();
        let walls = compute_boundary_walls(&visible, &map, 0);

        // North neighbors (y=0) are all walls: (1,0), (2,0), (3,0)
        // Also (0,1) is a wall (west of (1,1)) and (4,1) (east of (3,1))
        assert!(walls.contains(&(1, 0)));
        assert!(walls.contains(&(2, 0)));
        assert!(walls.contains(&(3, 0)));
        assert!(walls.contains(&(0, 1)));
        assert!(walls.contains(&(4, 1)));
    }

    #[test]
    fn boundary_walls_deduplicated() {
        // Two adjacent visible tiles share a wall neighbor
        let visible: BTreeSet<(i32, i32)> = [(1, 1), (2, 1)].into_iter().collect();
        let map = make_walled_map();
        let walls = compute_boundary_walls(&visible, &map, 0);

        // Count how many times (1,0) appears — should be exactly 1 (deduplicated)
        let count = walls.iter().filter(|&&(x, y)| x == 1 && y == 0).count();
        assert_eq!(count, 1, "boundary walls should be deduplicated");
    }

    #[test]
    fn boundary_walls_not_in_visible_positions() {
        // Verify the full NaturalVision pipeline produces BoundaryWall tiles
        // that are NOT in visible_positions.
        let map = make_walled_map();
        let nv = NaturalVision;
        let pos = TilePosition::new(2, 2, 0);
        let geometry = nv.compute_geometry(&pos, FacingDirection::North, &map);

        let boundary_tiles: Vec<_> = geometry
            .visible_tiles
            .iter()
            .filter(|t| t.visibility == VisibilitySector::BoundaryWall)
            .collect();

        // There should be boundary wall tiles (the 5x5 map has walls at edges)
        assert!(!boundary_tiles.is_empty(), "expected boundary wall tiles");

        // None of the boundary wall tiles should be in visible_positions
        for tile in &boundary_tiles {
            assert!(
                !geometry.visible_positions.contains(&(tile.x, tile.y)),
                "BoundaryWall tile ({}, {}) should NOT be in visible_positions",
                tile.x,
                tile.y
            );
        }

        // All boundary wall tiles should have TileKind::Wall
        for tile in &boundary_tiles {
            assert_eq!(tile.tile_kind, TileKind::Wall);
        }
    }
}