kiln/kiln-core/src/board.rs

use crate::floor::Floor;
use crate::fov::{color_to_rgb, FovCaster, Lighting};
use crate::glyph::Glyph;
use crate::log::LogLine;
use crate::utils::Direction;
use crate::utils::{ObjectId, RegistryValue};
use std::collections::{HashMap, HashSet};
use crate::portal::Portal;
use crate::tile::{DrawLayer, EnterResponse, Hookable, IntoTile, LocatedObject, ScriptAttributes, Sensor, Tile, TileSpec};

/// The complete state of one game board (a single room or screen).
///
/// `Board` is the central data structure of the engine, equivalent to a
/// "board" in ZZT. It contains everything needed to represent and run one
/// self-contained area of the game world:
///
/// - A grid of cells, each with a visual representation ([`Glyph`]) and an [`Archetype`]
/// - The current player position
/// - Scripted objects and portals (loaded but not yet active)
///
/// ## Cell storage
///
/// Cells are stored as `(Glyph, Archetype)` tuples in a row-major `Vec`.
/// Each cell directly owns its visual and behavioral class — there is no
/// separate element palette or index indirection. Access cells with
/// [`Board::get`] and [`Board::get_mut`] using `(x, y)` coordinates.
/// Use [`Board::is_passable`] for collision checks.
///
/// `Board` derives [`Clone`] to support deep-copying a whole [`World`](crate::world::World)
/// (see [`World::deep_clone`](crate::world::World::deep_clone)) — e.g. the editor's
/// playtest runs a game against an isolated copy so play mutations never touch the
/// boards being edited.
#[derive(Clone)]
pub struct Board {
    /// Human-readable name for this board, loaded from the map file and round-tripped on save.
    pub name: String,
    /// Width of the board in cells.
    pub width: usize,
    /// Height of the board in cells.
    pub height: usize,
    /// The single row-major grid of `Option<Tile>` cells (`width * height`),
    /// holding every solid. A transparent cell (glyph tile 0)
    /// draws nothing, revealing a `Sensor` or the
    /// [`floor`](Board::floor) beneath. Access a cell with [`Board::get`]/
    /// [`Board::get_mut`] by `(x, y)`.
    pub(crate) grid: Vec<Option<Tile>>,
    /// The board's cosmetic floor (blank / one fixed glyph / a biome), drawn beneath
    /// everything.
    pub(crate) floor: Floor,
    /// Non-solid things placed off the main grid, can't affect movement but see other hooks
    pub sensors: Vec<Sensor>,
    /// The portals aren't really a kind of sensor, and they can't be on the grid because the player
    /// can share a space with them:
    pub portals: Vec<Portal>,
    /// The next [`ObjectId`] to hand out (starts at 1, monotonically increasing).
    /// See [`Board::add_object`].
    pub next_object_id: ObjectId,
    /// When `true`, this board is "dark": front-ends reveal only the cells the
    /// player can see and that receive light (see [`Board::lighting`]) and draw
    /// everything else as unlit darkness. Sight and light are blocked by opaque cells.
    /// Loaded from / saved to the `dark` key in the map file's `[map]` header;
    /// defaults to `false` (fully lit).
    pub dark: bool,
    /// Per-board key→value store written and read by Rhai scripts via the
    /// `Registry` scope constant. Persists automatically across board transitions
    /// because all boards live as `Rc<RefCell<Board>>` in `World::boards` and are
    /// never evicted. Not saved to disk in v1.
    pub registry: HashMap<String, RegistryValue>,
}

impl Board {
    /// Return a list of all `ObjectId`s currently on the board.
    pub fn all_ids(&self) -> Vec<ObjectId> {
        self.grid.iter().filter_map(|cell| {
            if let Some(Tile::Object(def)) = cell {
                Some(def.scripting.id)
            } else {
                None
            }
        }).collect()
    }

    /// Returns a reference to the `(Glyph, Archetype)` cell at `(x, y)`.
    ///
    /// Panics if `x` or `y` are out of bounds.
    pub fn get(&self, x: usize, y: usize) -> &Option<Tile> {
        &self.grid[y * self.width + x]
    }

    /// Returns a mutable reference to the cell at `(x, y)`.
    ///
    /// Panics if `x` or `y` are out of bounds.
    pub fn get_mut(&mut self, x: usize, y: usize) -> &mut Option<Tile> {
        let w = self.width;
        &mut self.grid[y * w + x]
    }

    /// Replace the solid terrain (if any) at `(x, y)` with a transparent `Empty`
    /// cell, revealing the floor beneath.
    pub fn clear_cell(&mut self, x: usize, y: usize) {
        if self.in_bounds((x as i64, y as i64)) {
            *self.get_mut(x, y) = None;
        }
    }

    /// Returns the glyph to display at `(x, y)`.
    ///
    /// With a single grid the draw order is a fixed precedence (no layer walk):
    ///
    /// 1. the player (drawn on top; not part of the grid yet);
    /// 2. an object at the cell — a solid object always, otherwise the first
    ///    non-transparent non-solid object (`tile != 0`, so invisible objects exist);
    /// 3. the grid cell `(glyph, arch)` — a solid always draws, a non-solid only when
    ///    visible (`tile != 0`);
    /// 4. a portal at the cell (portals sit on a transparent grid cell);
    /// 5. a [`decoration`](Board::decorations) at the cell (reached only because the
    ///    grid cell was empty);
    /// 6. the [`floor`](Board::floor) glyph, if any;
    /// 7. the canonical black `Empty` glyph.
    ///
    /// Panics if out of bounds.
    pub fn glyph_at(&self, x: usize, y: usize) -> Glyph {
        let grid_glyph = self.get(x, y).as_ref().map(Tile::glyph);

        let sensors = self.sensors.iter().filter(|&s| s.x == x && s.y == y);

        // Is there a sensor above the grid?
        if let Some(above) = sensors.clone().find(|s| s.draw_layer == DrawLayer::Above && s.scripting.glyph.tile != 0) {
            return above.scripting.glyph;
        }

        // Does the grid have a good glyph?
        if let Some(glyph) = grid_glyph && glyph.tile != 0 {
            return glyph;
        }

        // Is there a sensor below the grid?
        if let Some(below) = sensors.clone().find(|s| s.draw_layer == DrawLayer::Below && s.scripting.glyph.tile != 0) {
            return below.scripting.glyph;
        }

        // Otherwise the floor, or the canonical black empty cell.
        self.floor
            .glyph_at(x, y, self.width)
            .unwrap_or_else(|| Glyph::transparent())
    }

    /// Returns `true` if `(x, y)` is a valid cell coordinate on this board.
    ///
    /// Takes signed coords so callers can pass a raw `pos + delta` without first
    /// checking for negatives.
    pub fn in_bounds(&self, pos: (i64, i64)) -> bool {
        let (x, y) = pos;
        x >= 0 && y >= 0 && (x as usize) < self.width && (y as usize) < self.height
    }

    /// Returns `true` if a mover can enter `(x, y)` — i.e. no solid occupies it.
    ///
    /// Convenience inverse of [`solid_at`](Board::solid_at).
    /// Panics if `x` or `y` are out of bounds.
    pub fn is_passable(&self, x: usize, y: usize) -> bool {
        self.get(x, y).is_none()
    }

    /// Returns `true` if cell `(x, y)` blocks line of sight (and light).
    ///
    /// A cell is sight-blocking if its grid terrain is opaque (e.g. a `Wall`)
    /// **or** any object on it is opaque. This is the input to lighting on
    /// [`dark`](Board::dark) boards; see [`Board::lighting`].
    /// Panics if `x` or `y` are out of bounds.
    pub fn is_opaque_at(&self, x: usize, y: usize) -> bool {
        if self.sensors.iter().any(|s| s.x == x && s.y == y && s.scripting.optics.opaque) {
            true
        } else {
            match self.get(x, y) {
                None => false,
                Some(Tile::Player) => false,
                Some(Tile::Object(def)) => {
                    def.scripting.optics.opaque
                }
            }
        }
    }

    /// Computes lighting + line-of-sight for the player on this board.
    ///
    /// Returns `None` unless the board is [`dark`](Board::dark) — a lit board
    /// needs no lighting and front-ends draw every cell at full color. On a dark
    /// board it (a) casts an unbounded line-of-sight field from the player, then
    /// (b) accumulates colored light from every source — the player's torch
    /// (radius `player_torch`, white), each object with `light > 0`, and each
    /// terrain cell with [`Archetype::light`] `> 0` — each source colored by its
    /// own glyph fg and falling off linearly to its radius. Opaque cells (via
    /// [`is_opaque_at`](Board::is_opaque_at)) block both sight and light.
    pub fn lighting(&self, player_torch: u32) -> Option<Lighting> {
        if !self.dark {
            return None;
        }
        let (w, h) = (self.width, self.height);
        let mut lighting = Lighting::new(w, h);
        // One caster whose transparency is seeded once from the opaque cells;
        // reused for the LOS pass and every light source (its FOV is cleared per cast).
        let mut caster = FovCaster::new(w, h, |x, y| !self.is_opaque_at(x, y));

        let (px, py) = self.player_pos();

        // (a) Player line of sight — unbounded (radius 0), pure geometry.
        caster.cast(px, py, 0, |x, y| lighting.set_los(x, y));

        // (b) Accumulate each light source into the per-cell color buffer. A
        // source paints every cell it can see within its radius, tinted by its
        // glyph fg and dimmed by a linear falloff (full at the source, 0 at the edge).
        let mut add_source = |lighting: &mut Lighting, sx: usize, sy: usize, radius: u32, color: [f32; 3]| {
            let r = radius as f32;
            caster.cast(sx, sy, radius as usize, |x, y| {
                let d = ((x as f32 - sx as f32).powi(2) + (y as f32 - sy as f32).powi(2)).sqrt();
                let falloff = (1.0 - d / r).max(0.0);
                lighting.add_light(x, y, [color[0] * falloff, color[1] * falloff, color[2] * falloff]);
            });
        };

        // The player's torch: a white light centered on the player.
        if player_torch > 0 {
            add_source(&mut lighting, px, py, player_torch, [1.0, 1.0, 1.0]);
        }
        // Glowing terrain (e.g. a `Torch` cell): color = the cell's glyph foreground.
        for y in 0..h {
            for x in 0..w {
                if let Some(Tile::Object(obj)) = self.get(x, y) {
                    let radius = obj.scripting.optics.glow;
                    if radius > 0 {
                        add_source(&mut lighting, x, y, radius, color_to_rgb(obj.scripting.glyph.fg));
                    }
                }
            }
        }
        Some(lighting)
    }

    /// Whether the cell's single solid occupant (if any) can be pushed in `dir`.
    ///
    /// This is whether the thing in this cell will _transmit_ a push impulse through
    /// it. Empty cells and cells that can't be pushed in that direction break the
    /// chain.
    fn is_pushable(&self, x: usize, y: usize, dir: Direction) -> bool {
        match self.get(x, y) {
            Some(Tile::Player) => true,
            Some(Tile::Object(obj)) => {
                if let EnterResponse::Push(p) = obj.enter_response {
                    p.allows(dir)
                } else {
                    false
                }
            }
            _ => false,
        }
    }

    /// The object that a move **into** `(x, y)` heading `dir` bumps, if any.
    ///
    /// Walks the chain of pushable crates from the target cell in `dir` until it
    /// reaches something that stops it, and reports the object it presses against:
    /// - a `Block` object in the target cell (or at the end of a pushable chain) is the
    ///   bumped object,
    /// - open space or the player means nothing is bumped,
    ///
    /// This is what lets *any* solid — the player, another object, or a pushed
    /// crate — trigger a `bump`: the bumper need not be an object, since we only
    /// return the *bumped* object's id (the direction it came from is supplied by
    /// the caller from its move direction).
    pub fn bump_target(&self, x: usize, y: usize, dir: Direction) -> Option<ObjectId> {
        let (dx, dy): (i64, i64) = dir.into();
        let (mut cx, mut cy) = (x, y);
        loop {
            if !self.in_bounds((cx as i64, cy as i64)) {
                return None; // push chain runs off the board
            }

            if let Some(Tile::Object(obj)) = self.get(cx, cy) {
                if obj.enter_response.transmits_push(dir) {
                    // An object we can push through, go to the next cell
                    cx = (cx as i64 + dx) as usize;
                    cy = (cy as i64 + dy) as usize;
                } else if obj.enter_response.bumpable(dir) {
                    return Some(obj.scripting.id)
                }
            }
        }
    }

    /// Whether the chain of pushable solids starting at `(x, y)` can be shoved one
    /// step in `dir` — i.e. the chain ends at a passable cell rather than the board
    /// edge or a non-pushable solid.
    ///
    /// Read-only (`&self`); pairs with [`push`](Board::push). Returns `false` when
    /// `(x, y)` itself holds no pushable solid, so it doubles as the "is the cell
    /// ahead shovable?" half of a "can I move here?" query.
    pub fn can_push(&self, x: usize, y: usize, dir: Direction) -> bool {
        let (dx, dy): (i64, i64) = dir.into();
        let (mut cx, mut cy) = (x, y);
        loop {
            // This cell must hold a solid pushable in `dir` to advance the chain.
            if !self.is_pushable(cx, cy, dir) {
                return false;
            }
            let next = (cx as i64 + dx, cy as i64 + dy);
            if !self.in_bounds(next) {
                return false; // chain runs off the board
            }
            let (nx, ny) = (next.0 as usize, next.1 as usize);
            if self.is_passable(nx, ny) {
                return true; // open space at the end: the whole chain can move
            }
            // Next cell holds a solid too; continue (it must itself be pushable).
            cx = nx;
            cy = ny;
        }
    }

    /// Whether the solid at `(x, y)` can be **shifted** one step in `dir`: it is
    /// itself a pushable solid *and* the next cell is either empty or holds another
    /// pushable solid.
    ///
    /// Unlike [`can_push`](Board::can_push) this inspects only the single cell
    /// ahead — it does **not** verify the whole chain ends in open space. It is the
    /// right test for a simultaneous rotation/shift (applied via
    /// [`apply_swap`](Board::apply_swap)), where a destination is occupied by
    /// another pushable that is itself moving the same frame. Returns `false` if
    /// `(x, y)` holds no pushable, or the cell ahead runs off the board.
    ///
    /// The **player** is always a blocker: a shift can't relocate the player, and
    /// `apply_swap` refuses to overwrite it, so a cell holding the player is never
    /// an acceptable shift destination.
    pub fn can_shift(&self, x: usize, y: usize, dir: Direction) -> bool {
        // The source must hold a solid pushable in `dir`.
        if !self.is_pushable(x, y, dir) {
            return false;
        }
        let (dx, dy): (i64, i64) = dir.into();
        let next = (x as i64 + dx, y as i64 + dy);
        if !self.in_bounds(next) {
            return false; // nothing to shift into off the board
        }
        let (nx, ny) = (next.0 as usize, next.1 as usize);
        // The player always blocks a shift: a shift can't relocate it and
        // `apply_swap` refuses to overwrite it. (The player reads as pushable, so it
        // must be excluded explicitly before the cell-ahead test below.)
        if self.get(nx, ny).as_ref().is_some_and(Tile::player) {
            return false;
        }
        // The cell ahead is acceptable if it is empty or another pushable solid.
        self.is_passable(nx, ny) || self.is_pushable(nx, ny, dir)
    }

    /// Shoves the chain of pushable solids starting at `(x, y)` one step in `dir`,
    /// leaving `Empty` floor behind each moved cell.
    ///
    /// No-op when the chain can't move (it self-checks via [`can_push`](Board::can_push)),
    /// so it is safe to call unconditionally.
    /// Returns the cells the shoved solids moved **into** (each chain cell stepped
    /// one cell in `dir`), so the caller can fire `enter` on any non-solid object a
    /// pushed solid landed on. Empty when nothing moved.
    pub fn push(&mut self, x: usize, y: usize, dir: Direction) -> Vec<(usize, usize)> {
        if !self.can_push(x, y, dir) {
            return Vec::new();
        }
        let (dx, dy): (i64, i64) = dir.into();
        // can_push guaranteed the chain ends at an in-bounds passable cell, so
        // re-walk it (no bounds checks needed) and shift the far end first, which
        // keeps each destination cell vacated before its occupant arrives.
        let mut chain: Vec<(usize, usize)> = Vec::new();
        let (mut cx, mut cy) = (x, y);
        while !self.is_passable(cx, cy) {
            chain.push((cx, cy));
            cx = (cx as i64 + dx) as usize;
            cy = (cy as i64 + dy) as usize;
        }
        for &(px, py) in chain.iter().rev() {
            self.shift_solid(px, py, dx, dy);
        }
        // Each solid ended up one step along `dir`; those destination cells are
        // where an `enter` may need to fire.
        chain
            .iter()
            .map(|&(px, py)| ((px as i64 + dx) as usize, (py as i64 + dy) as usize))
            .collect()
    }

    /// Moves the single solid occupant of `(x, y)` one step by `(dx, dy)`.
    ///
    /// A solid object is relocated; otherwise the solid terrain archetype (a crate)
    /// is moved, leaving a transparent cell behind so the floor shows through. The
    /// caller guarantees the destination is already clear.
    fn shift_solid(&mut self, x: usize, y: usize, dx: i64, dy: i64) {
        let (tx, ty) = ((x as i64 + dx) as usize, (y as i64 + dy) as usize);
        if self.get(x, y).is_none() {
            return; // nothing to shift
        }

        *self.get_mut(tx, ty) = self.get_mut(x, y).take();
    }

    /// Returns the [`ObjectId`]s of the **non-solid** objects at `(x, y)`.
    ///
    /// These are the targets of an `enter` hook when a solid relocates onto the
    /// cell (terrain is always solid, so only objects can be non-solid). Mirrors
    /// [`object_ids_at`](Board::object_ids_at) / [`solid_object_id_at`](Board::solid_object_id_at).
    pub fn sensor_ids_at(&self, x: usize, y: usize) -> Vec<ObjectId> {
        self.sensors
            .iter()
            .filter(|s| s.x == x && s.y == y)
            .map(|s| s.scripting.id)
            .collect()
    }

    /// Find and return the portal at the given location
    pub fn portal_at(&self, x: usize, y: usize) -> Option<&Portal> {
        self.portals.iter().find(|&portal| portal.location() == (x, y))
    }

    /// Editor primitive: stamps `arch` (with visual `glyph`) into the cell at
    /// `(x, y)`, applying the editor's placement/removal rules.
    ///
    /// Two cases, keyed only on the archetype (the floor is **never** touched — the
    /// drawing tools cannot place, remove, or alter a floor):
    ///
    /// - **Terrain** (`arch != Empty`, always solid today): removes any solid object
    ///   already in the cell, then writes `(glyph, arch)` into the grid cell.
    /// - **Erase** (`arch == Empty`): removes the grid cell's terrain *and* every
    ///   object in it, leaving the floor beneath in place.
    ///
    /// A vacated grid cell becomes a transparent `Empty` so the floor shows through.
    /// Panics if `(x, y)` is out of bounds.
    pub fn place(&mut self, x: usize, y: usize, spec: Option<TileSpec>) -> Result<(), String> {
        if let Some(spec) = spec {
            let tile = spec.into_tile(&mut self.next_object_id)?;
            *self.get_mut(x, y) = Some(tile);
        } else {
            *self.get_mut(x, y) = None;
        }
        Ok(())
    }

    /// Shifts a set of cells, given as `(x, y)` coordinates. Backs the script
    /// `shift()` fn. Returns a [`ShiftOutcome`] carrying any error [`LogLine`]s for
    /// the caller to log plus the `(from, to)` relocations it performed (so the
    /// caller can fire `enter` on non-solids each moved solid landed on).
    pub fn apply_shift(&mut self, cells: &[(i64, i64)]) -> Result<Vec<((i64, i64), (i64, i64))>, String> {
        // Validate all the cells are in bounds, error if not:
        if cells.iter().any(|&c| !self.in_bounds(c)) {
            return Err("Called shift() with a cell out of bounds".to_string())
        }

        // Get all the Solids at these cells:
        let solids: Vec<_> = cells.iter().map(|&c| self.get_mut(c.0 as usize, c.1 as usize).take()).collect();

        // Find which ones are blockers
        let mut immobile = HashSet::new();
        for (curr_idx, curr) in solids.iter().enumerate() {
            let pushable = curr.as_ref().map_or(true, |c| c.shiftable());
            if !pushable {
                immobile.insert(curr_idx);
            }
        }

        // Trace back from each immobile until we find an empty:
        let mut blocked = HashSet::new();
        for curr_idx in immobile {
            let mut prev_idx = curr_idx;
            loop {
                if solids[prev_idx].is_some() && !blocked.contains(&prev_idx) {
                    blocked.insert(prev_idx);
                    prev_idx = (prev_idx + cells.len() - 1) % cells.len();
                } else {
                    break
                }
            }
        }

        // Now, move anything that we've decided is not blocked, recording each
        // relocation so the caller can fire `enter` at every destination.
        let mut moves = Vec::new();
        for (curr_idx, curr) in solids.into_iter().enumerate() {
            if let Some(solid) = curr {
                if !blocked.contains(&curr_idx) {
                    // Not blocked, write it to target
                    let origin = cells[curr_idx];
                    let target = cells[(curr_idx + 1) % cells.len()];
                    *self.get_mut(target.0 as usize, target.1 as usize) = Some(solid);
                    moves.push((origin, target));
                } else {
                    // it was blocked so just write it back where it was
                    let origin = cells[curr_idx];
                    *self.get_mut(origin.0 as usize, origin.1 as usize) = Some(solid);
                }
            }
        }

        Ok(moves)
    }

    /// Clear the queues of all objects on this board: called when entering a board, objects
    /// don't retain their state across board visits (they get initialized again, but can
    /// store things in the board registry)
    pub fn clear_all_queues(&mut self) {
        for cell in self.grid.iter_mut() {
            if let Some(Tile::Object(obj)) = cell {
                obj.scripting.queue.clear()
            }
        }
    }

    pub fn player_pos(&self) -> (usize, usize) {
        self.grid.iter().enumerate().find_map(|(i, cell)| {
            if matches!(cell, Some(Tile::Player)) {
                Some((i % self.width, i / self.width))
            } else { None }
        }).expect("No player found!") // This should never happen, player presence is validated when building a board
    }

    pub fn get_hookable(&self, id: ObjectId) -> Option<Box<dyn Hookable + '_>> {
        // Search sensors first because it's probably shorter
        for sensor in self.sensors.iter() {
            if sensor.scripting.id == id {
                return Some(Box::new(sensor))
            }
        }

        for (i, tile) in self.grid.iter().enumerate() {
            if let Some(Tile::Object(obj)) = tile && obj.scripting.id == id {
                return Some(Box::new(LocatedObject(obj, (i % self.width, i / self.width))))
            }
        }

        None
    }

    pub fn get_named(&self, name: &str) -> Option<Box<dyn Hookable + '_>> {
        // Search sensors first because it's probably shorter
        for sensor in self.sensors.iter() {
            if let Some(n) = sensor.scripting.name.as_ref() &&
                n.as_str() == name {
                return Some(Box::new(sensor))
            }
        }

        for (i, tile) in self.grid.iter().enumerate() {
            if let Some(Tile::Object(obj)) = tile &&
                let Some(n) = obj.scripting.name.as_ref() &&
                n.as_str() == name {
                return Some(Box::new(LocatedObject(obj, (i % self.width, i / self.width))))
            }
        }

        None
    }

    pub fn get_tagged(&self, tag: &str) -> Vec<Box<dyn Hookable + '_>> {
        self.sorted_hookables().into_iter().filter(|hookable| {
            hookable.scriptable().tags.contains(tag)
        }).collect()
    }

    pub fn scripting_mut(&mut self, id: ObjectId) -> Option<&mut ScriptAttributes> {
        for sensor in self.sensors.iter_mut() {
            if sensor.scripting.id == id {
                return Some(&mut sensor.scripting)
            }
        }

        for tile in self.grid.iter_mut() {
            if let Some(Tile::Object(obj)) = tile && obj.scripting.id == id {
                return Some(&mut obj.scripting)
            }
        }

        None
    }

    pub fn sorted_hookables(&self) -> Vec<Box<dyn Hookable + '_>> {
        // Collect all the sensors
        let mut hookables = self.sensors.iter().map(|s| Box::new(s) as Box<dyn Hookable>).collect::<Vec<_>>();

        // Add the objects into it
        for (i, tile) in self.grid.iter().enumerate() {
            if let Some(Tile::Object(obj)) = tile {
                hookables.push(Box::new(LocatedObject(obj, (i % self.width, i / self.width))))
            }
        }

        // Sort by id
        hookables.sort_by(|a, b| a.id().cmp(&b.id()));
        hookables
    }

    pub fn remove_object(&mut self, id: ObjectId) {
        if let Some(tile) = self.grid.iter_mut().find(|cell| { matches!(cell, Some(Tile::Object(obj)) if obj.scripting.id == id) }) {
            tile.take();
        } else {
            self.sensors.retain(|s| s.id() != id);
        }
    }

    pub fn named_portal(&self, name: &str) -> Option<&Portal> {
        self.portals.iter().find(|p| p.name == name)
    }

    pub fn move_sensor(&mut self, id: ObjectId, dir: Direction) {
        if let Some((sensor_idx, _)) = self.sensors.iter().enumerate().find(|(idx, s)| s.scripting.id == id) {
            let new_loc = (self.sensors[sensor_idx].x as i64 + dir.dx(), self.sensors[sensor_idx].y as i64 + dir.dy());
            if self.in_bounds(new_loc) {
                self.sensors[sensor_idx].x = new_loc.0 as usize;
                self.sensors[sensor_idx].y = new_loc.1 as usize;
            }
        }
    }
}

#[cfg(test)]
pub(crate) mod tests {
    use std::assert_matches;
    use super::Board;
    use crate::builtin::Builtin;
    use crate::floor::Floor;
    use crate::glyph::Glyph;
    use crate::utils::Direction;
    use color::Rgba8;
    use std::collections::HashMap;
    use crate::tile::{DrawLayer, IntoTile, Optics, ScriptAttributes, Sensor, Tile, TileSpec};

    /// Builds an all-empty `w×h` board.
    ///
    /// The grid is fully transparent (a blank floor), so terrain stamped via
    /// [`crate_at`] etc. lands on the single grid. Use [`add_floor`] to give the
    /// board a visible fixed floor underneath.
    pub(crate) fn open_board(
        w: usize,
        h: usize,
        player_pos: (usize, usize)
    ) -> Board {
        let mut board = Board {
            name: "test".into(),
            width: w,
            height: h,
            grid: vec![None; w * h],
            floor: Floor::Blank,
            sensors: Vec::new(),
            portals: Vec::new(),
            next_object_id: 1,
            dark: false,
            registry: HashMap::new(),
        };
        player_at(&mut board, player_pos.0, player_pos.1);
        board
    }

    /// Gives the board a uniform fixed floor glyph (the single-grid replacement for
    /// the old separate floor layer).
    pub(crate) fn add_floor(board: &mut Board, glyph: Glyph) {
        board.floor = Floor::Fixed(glyph);
    }

    /// Stamps a crate cell onto the grid.
    pub(crate) fn crate_at(board: &mut Board, x: usize, y: usize) {
        *board.get_mut(x, y) = Some(TileSpec::krate().into_tile(&mut board.next_object_id).unwrap());
    }

    /// Stamps a wall cell onto the grid.
    pub(crate) fn wall_at(board: &mut Board, x: usize, y: usize) {
        *board.get_mut(x, y) = Some(TileSpec::wall().into_tile(&mut board.next_object_id).unwrap());
    }

    /// Stamps a gem cell onto the grid.
    pub(crate) fn gem_at(board: &mut Board, x: usize, y: usize) {
        *board.get_mut(x, y) = Some(TileSpec::gem().into_tile(&mut board.next_object_id).unwrap());
    }

    /// Stamps a player cell onto the grid.
    pub(crate) fn player_at(board: &mut Board, x: usize, y: usize) {
        *board.get_mut(x, y) = Some(TileSpec::player().into_tile(&mut board.next_object_id).unwrap());
    }

    pub(crate) fn lamp_at(board: &mut Board, x: usize, y: usize) {
        let lamp = Sensor {
            x,
            y,
            draw_layer: DrawLayer::Above,
            scripting: ScriptAttributes {
                id: board.next_object_id,
                glyph: Glyph { tile: 1, fg: Rgba8 { r: 255, g: 0, b: 0, a: 255 }, bg: Rgba8 { r: 0, g: 0, b: 0, a: 255 } },
                optics: Optics {
                    glow: 4,
                    opaque: false
                },
                ..Default::default()
            }
        };
        board.next_object_id += 1;
        board.sensors.push(lamp);
    }

    pub(crate) fn is_builtin(board: &Board, x: usize, y: usize, tag: &str) -> bool {
        if let Some(Tile::Object(obj)) = board.get(x, y) {
            obj.scripting.tags.contains(&format!("BUILTIN_{tag}"))
        } else { false }
    }

    #[test]
    fn in_bounds_checks_grid_boundaries() {
        let board = open_board(3, 2, (0, 0));
        assert!(board.in_bounds((0, 0)));
        assert!(board.in_bounds((2, 1)));
        assert!(!board.in_bounds((-1, 0)));
        assert!(!board.in_bounds((0, -1)));
        assert!(!board.in_bounds((3, 0)));
        assert!(!board.in_bounds((0, 2)));
    }

    #[test]
    fn can_push_is_read_only_and_correct() {
        let mut board = open_board(3, 1, (0, 0));
        crate_at(&mut board, 1, 0);
        assert!(board.can_push(1, 0, Direction::East));
        assert_matches!(board.get(1, 0), Some(Tile::Object(_)));
        assert_matches!(board.get(2, 0), None);

        let mut board = open_board(3, 1, (0, 0));
        crate_at(&mut board, 1, 0);
        wall_at(&mut board, 2, 0);
        assert!(!board.can_push(1, 0, Direction::East));
    }

    #[test]
    fn can_shift_only_checks_the_cell_ahead() {
        // Source must be pushable.
        let mut board = open_board(4, 1, (3, 0));
        assert!(!board.can_shift(0, 0, Direction::East)); // empty source

        // Crate with open space ahead: shiftable.
        crate_at(&mut board, 0, 0);
        assert!(board.can_shift(0, 0, Direction::East));
        assert_matches!(board.get(0, 0), Some(Tile::Object(_)));

        // Crate with another pushable crate ahead: still shiftable (unlike can_push,
        // which would follow the chain to the wall and fail).
        let mut board = open_board(4, 1, (3, 0));
        crate_at(&mut board, 0, 0);
        crate_at(&mut board, 1, 0);
        wall_at(&mut board, 2, 0);
        assert!(board.can_shift(0, 0, Direction::East));
        assert!(!board.can_push(0, 0, Direction::East));

        // Crate with a non-pushable wall ahead: not shiftable.
        let mut board = open_board(3, 1, (2, 0));
        crate_at(&mut board, 0, 0);
        wall_at(&mut board, 1, 0);
        assert!(!board.can_shift(0, 0, Direction::East));

        // Crate at the board edge facing off-board: not shiftable.
        let mut board = open_board(2, 1, (0, 0));
        crate_at(&mut board, 1, 0);
        assert!(!board.can_shift(1, 0, Direction::East));
    }

    #[test]
    fn can_shift_treats_the_player_as_a_blocker() {
        // The player is always a blocker for a shift — even a grab gem may not shift
        // onto it (grab now fires only on player movement, not on being shifted in).
        let mut board = open_board(2, 1, (1, 0));
        gem_at(&mut board, 0, 0);
        assert!(!board.can_shift(0, 0, Direction::East));

        // A plain crate likewise may not shift onto the player.
        let mut board = open_board(2, 1, (1, 0));
        crate_at(&mut board, 0, 0);
        assert!(!board.can_shift(0, 0, Direction::East));
    }

    #[test]
    fn push_into_player_pushes_player() {
        // Crate shoved east into the player slides the player along into open space.
        let mut board = open_board(4, 1, (2, 0));
        crate_at(&mut board, 1, 0);
        assert!(board.can_push(1, 0, Direction::East));
        board.push(1, 0, Direction::East);
        assert!(board.get(1, 0).is_none());
        assert!(is_builtin(&board, 2, 0,"crate"));
        assert_eq!(board.player_pos(), (3, 0));
    }

    #[test]
    fn push_into_player_blocked_by_wall() {
        // Player backed against a wall: push has nowhere to go, nothing moves.
        let mut board = open_board(4, 1, (2, 0));
        crate_at(&mut board, 1, 0);
        wall_at(&mut board, 3, 0);
        assert!(!board.can_push(1, 0, Direction::East));
        board.push(1, 0, Direction::East); // no-op
        assert!(is_builtin(&board, 1, 0, "crate"));
        assert_eq!(board.player_pos(), (2, 0));
    }

    #[test]
    fn glyph_at_uses_floor_for_empty_and_grid_for_solid() {
        // Player parked at (2,0) so it doesn't overlap either asserted cell.
        let mut board = open_board(3, 1, (2, 0));
        let floor_glyph = Glyph {
            tile: '.' as u32,
            fg: Rgba8 {
                r: 10,
                g: 20,
                b: 30,
                a: 255,
            },
            bg: Rgba8 {
                r: 1,
                g: 2,
                b: 3,
                a: 255,
            },
        };
        // A fixed floor attribute, a wall on the grid at (0,0).
        add_floor(&mut board, floor_glyph);
        wall_at(&mut board, 0, 0);
        // The wall (solid) draws over the floor; the empty cell reveals the floor.
        assert_eq!(board.glyph_at(0, 0), Builtin::Wall.default_glyph_for("wall"));
        assert_eq!(board.glyph_at(1, 0), floor_glyph);
    }

    #[test]
    fn apply_shift_out_of_bounds_rejects_immediately() {
        // apply_shift validates all cells upfront; any out-of-bounds cell causes immediate failure.
        let mut board = open_board(3, 1, (2, 0));
        crate_at(&mut board, 0, 0);
        let errs = board.apply_shift(&[(0, 0), (9, 0)]);
        assert!(errs.is_err());
        assert!(is_builtin(&board, 0, 0, "crate")); // unchanged
    }

    #[test]
    fn apply_shift_wall_stops_cascade_but_empty_limits_it() {
        // A non-pushable Wall is immobile. Backward cascade from the wall traces
        // through preceding solids until it hits empty, marking those as blocked.
        // Solids on the *other* side of the empty (outside the blocked region) still move.
        let mut board = open_board(6, 1, (5, 0));
        crate_at(&mut board, 0, 0);
        // (1,0) stays empty
        wall_at(&mut board, 2, 0);
        crate_at(&mut board, 3, 0);
        crate_at(&mut board, 4, 0);

        // Cycle: idx 0 → idx 1 → idx 2 → idx 3 → idx 4 → idx 0 (wrap)
        // immobile = {2} (Wall, Pushable::No)
        // Backward trace from idx 2: solids[2]=Some → blocked.insert(2), prev=1
        //   solids[1]=None (empty) → break
        // blocked = {2}; Crate at (0,0) is NOT blocked
        // Result: Crate(0,0)→(1,0), empty→no-op, Wall stays at (2,0),
        //         Crate(3,0)→(4,0), Crate(4,0)→(0,0) wrap
        let _errs = board.apply_shift(&[(0, 0), (1, 0), (2, 0), (3, 0), (4, 0)]);

        assert!(is_builtin(&board, 0, 0, "crate")); // wrapped from (4,0)
        assert!(is_builtin(&board, 1, 0, "crate")); // moved from (0,0)
        assert!(is_builtin(&board, 2, 0, "wall")); // blocked, immobile
        assert!(board.get(3, 0).is_none()); // cleared, crate moved
        assert!(is_builtin(&board, 4, 0, "crate")); // moved from (3,0)
    }

    #[test]
    fn lighting_none_when_not_dark() {
        // A lit board needs no lighting; front-ends draw every cell.
        let board = open_board(5, 1, (0, 0));
        assert!(!board.dark);
        assert!(board.lighting(10).is_none());
    }

    #[test]
    fn wall_is_opaque_empty_is_not() {
        let mut board = open_board(3, 1, (0, 0));
        wall_at(&mut board, 1, 0);
        assert!(board.is_opaque_at(1, 0)); // wall blocks sight
        assert!(!board.is_opaque_at(2, 0)); // empty cell is transparent
    }

    #[test]
    fn dark_board_hides_cells_behind_a_wall() {
        // Player at the left end of a 1-wide corridor; a wall at x=2 occludes
        // everything past it. The player's torch lights cells before the wall
        // (and the wall itself); the cells behind the wall are neither lit nor
        // in line of sight, so they are not visible.
        let mut board = open_board(5, 1, (0, 0));
        board.dark = true;
        wall_at(&mut board, 2, 0);

        let lit = board.lighting(10).expect("dark board yields Lighting");
        assert!(lit.is_visible(0, 0)); // the player's own cell
        assert!(lit.is_visible(1, 0)); // open cell before the wall
        assert!(lit.is_visible(2, 0)); // the wall itself (light_walls = true)
        assert!(!lit.is_visible(3, 0)); // occluded behind the wall
        assert!(!lit.is_visible(4, 0)); // occluded behind the wall
    }

    #[test]
    fn unlit_cell_in_sight_is_not_visible() {
        // A long lit-free corridor: with a tiny torch, far cells are in line of
        // sight but receive no light, so they are not visible (LOS ∩ lit).
        let mut board = open_board(10, 1, (0, 0));
        board.dark = true;
        let lit = board.lighting(2).expect("dark board yields Lighting");
        assert!(lit.is_visible(0, 0)); // at the torch
        assert!(lit.is_visible(1, 0)); // within the torch radius
        assert!(!lit.is_visible(8, 0)); // in sight but unlit → dark
    }

    #[test]
    fn object_light_tints_toward_its_color() {
        // A dark board with no player torch and one red-glyph light object: the
        // object's cell is lit red, so a white base tints red (green/blue killed).
        let mut board = open_board(3, 1, (1, 0));
        board.dark = true;
        lamp_at(&mut board, 1, 0);

        let lit = board.lighting(0).expect("dark board yields Lighting"); // no player torch
        let white = Rgba8 { r: 255, g: 255, b: 255, a: 255 };
        let t = lit.tint(1, 0, white);
        assert!(t.r > 0, "red channel survives");
        assert_eq!(t.g, 0, "green killed by red light");
        assert_eq!(t.b, 0, "blue killed by red light");
    }
}