kiln/kiln-core/src/game.rs

use crate::action::Action;
use crate::log::LogLine;
use crate::script::ScriptHost;
use std::cell::{Ref, RefCell, RefMut};
use std::rc::Rc;
use std::time::Duration;
use crate::board::Board;
use crate::utils::{Direction, ObjectId, ScriptArg, Solid};

/// How long a `say()` speech bubble stays on screen, in seconds.
pub const SAY_DURATION: f64 = 3.0;

// Re-export ScrollLine so kiln-tui can pattern-match scroll content without
// accessing the private `action` module directly.
pub use crate::action::ScrollLine;

/// An active scroll overlay opened by a scripted object via `scroll()`.
///
/// While a `Scroll` is present on [`GameState`], the front-end should pause ticks
/// and display the overlay. Closed via [`GameState::close_scroll`].
pub struct Scroll {
    /// The object whose `scroll()` call opened this overlay.
    pub source: ObjectId,
    /// The lines of content to display.
    pub lines: Vec<ScrollLine>,
}

/// An active speech bubble emitted by a scripted object via `say()`.
pub struct SpeechBubble {
    /// The object whose `say()` call created this bubble.
    pub object_id: ObjectId,
    /// The text to display.
    pub text: String,
    /// Seconds remaining before the bubble disappears.
    pub remaining: f64,
}

/// Holds the active game world and provides game-logic operations.
///
/// `GameState` is the boundary between the engine (rendering, input) and the
/// game data. It owns the board (behind a shared `Rc<RefCell<Board>>`),
/// the message log, and the [`ScriptHost`] driving object scripts. Front-ends and
/// internal logic reach the board through [`board`](GameState::board) /
/// [`board_mut`](GameState::board_mut). Scripts read the board directly and
/// request mutations as commands, applied by [`apply_commands`](GameState::apply_commands)
/// after each script batch.
pub struct GameState {
    /// The scriptable world, shared with the script host's read getters.
    board: Rc<RefCell<Board>>,
    /// The in-game message log, oldest first (newest pushed at the end).
    pub log: Vec<LogLine>,
    /// The Rhai scripting runtime driving this board's scripted objects.
    scripts: ScriptHost,
    /// Active speech bubbles from `say()` calls, displayed by the front-end over the board.
    pub speech_bubbles: Vec<SpeechBubble>,
    /// An active scroll overlay opened by `scroll()`. `Some` while the overlay is
    /// visible; the front-end pauses ticks and closes it via [`close_scroll`](GameState::close_scroll).
    pub active_scroll: Option<Scroll>,
}

impl GameState {
    /// Creates a `GameState` from a pre-loaded [`Board`].
    ///
    /// Compiles the board's object scripts but does **not** run any of them;
    /// call [`GameState::run_init`] once the game is ready to start. Any script
    /// compile errors are surfaced into the log here.
    pub fn new(board: Board) -> Self {
        let board = Rc::new(RefCell::new(board));
        let scripts = ScriptHost::new(&board);
        let mut state = Self {
            board,
            log: Vec::new(),
            scripts,
            speech_bubbles: Vec::new(),
            active_scroll: None,
        };
        // Surface any compile-time script errors collected during ScriptHost::new.
        state.drain_errors();
        state
    }

    /// Borrows the active board for reading (e.g. by a front-end renderer).
    pub fn board(&self) -> Ref<'_, Board> {
        self.board.borrow()
    }

    /// Borrows the active board for mutation.
    pub fn board_mut(&self) -> RefMut<'_, Board> {
        self.board.borrow_mut()
    }

    /// Appends a styled message to the log.
    pub fn log(&mut self, line: LogLine) {
        self.log.push(line);
    }

    /// Runs the `init()` hook of every scripted object, pumps their queues, and
    /// resolves the resulting actions. Call once, after the whole map is loaded and
    /// the game is about to start — never during map deserialization, since a script
    /// may inspect the board.
    pub fn run_init(&mut self) {
        self.scripts.run_init();
        self.resolve();
    }

    /// Advances real-time game state by `dt` (the elapsed time since the last tick).
    /// Called once per frame by the front-end's game loop. Counts down object
    /// cooldowns, drives every scripted object's `tick(dt)` hook (pumping each queue),
    /// then resolves the actions that were promoted onto the board queue.
    pub fn tick(&mut self, dt: Duration) {
        let secs = dt.as_secs_f64();
        self.scripts.run_tick(secs);
        // Expire speech bubbles before resolving new actions so a fresh say()
        // this frame isn't immediately culled.
        self.speech_bubbles.retain_mut(|b| { b.remaining -= secs; b.remaining > 0.0 });
        self.resolve();
    }

    /// Drains errors collected by the script host into the game log.
    fn drain_errors(&mut self) {
        // TODO: errors are only logged for now. This is the place to halt execution /
        // set an error state when a script faults.
        let errors = self.scripts.take_errors();
        self.log.extend(errors);
    }

    /// Resolves the board queue: applies each promoted action to the board, then fires
    /// the `bump` and `send` hooks the moves triggered.
    ///
    /// Done in two phases so no `board_mut` borrow is held while scripts run
    /// (they read the board through its getters): phase A mutates the board and records
    /// `(bumped, bumper)` and `(send_target, fn_name, arg)` tuples; phase B fires the
    /// hooks after the borrow drops.
    fn resolve(&mut self) {
        let actions = self.scripts.take_board_queue();
        // Logs are collected here rather than pushed inline, since the board borrow
        // below also borrows `self`.
        let mut logs: Vec<LogLine> = Vec::new();
        let mut bumps: Vec<(ObjectId, i64)> = Vec::new();
        let mut sends: Vec<(ObjectId, String, Option<ScriptArg>)> = Vec::new();
        let mut new_bubbles: Vec<SpeechBubble> = Vec::new();
        // Collected outside the board borrow so we can assign to self.active_scroll.
        let mut new_scroll: Option<Scroll> = None;
        {
            let mut board = self.board_mut();
            for ba in actions {
                match ba.action {
                    Action::Move(dir) => {
                        if let Some(bumped) = step_object(&mut board, ba.source, dir) {
                            bumps.push((bumped, ba.source as i64));
                        }
                    }
                    Action::SetTile(tile) => {
                        if let Some(obj) = board.objects.get_mut(&ba.source) {
                            obj.glyph.tile = tile;
                        }
                    }
                    Action::Log(line) => logs.push(line),
                    Action::SetTag { target, tag, present } => {
                        if let Some(obj) = board.objects.get_mut(&target) {
                            if present { obj.tags.insert(tag); } else { obj.tags.remove(&tag); }
                        }
                    }
                    // Replace any existing bubble from this object so repeated say() calls
                    // don't stack visually — the new text resets the timer.
                    Action::Say(text) => new_bubbles.push(SpeechBubble {
                        object_id: ba.source,
                        text,
                        remaining: SAY_DURATION,
                    }),
                    // Delays are consumed by ScriptHost::drain and never reach the board queue.
                    Action::Delay(_) => {}
                    Action::SetColor { fg, bg } => {
                        if let Some(obj) = board.objects.get_mut(&ba.source) {
                            if let Some(c) = fg { obj.glyph.fg = c; }
                            if let Some(c) = bg { obj.glyph.bg = c; }
                        }
                    }
                    // Collected and fired after the board borrow drops, like bumps.
                    Action::Send { target, fn_name, arg } => {
                        sends.push((target, fn_name, arg));
                    }
                    // Later scrolls overwrite earlier ones from the same tick.
                    Action::Scroll(lines) => {
                        new_scroll = Some(Scroll { source: ba.source, lines });
                    }
                }
            }
        }
        self.log.extend(logs);
        for bubble in new_bubbles {
            // One bubble per object: replace the existing one if present.
            self.speech_bubbles.retain(|b| b.object_id != bubble.object_id);
            self.speech_bubbles.push(bubble);
        }
        if let Some(scroll) = new_scroll {
            self.active_scroll = Some(scroll);
        }
        for (bumped, bumper) in bumps {
            self.scripts.run_bump(bumped, bumper);
        }
        for (target, fn_name, arg) in sends {
            self.scripts.run_send(target, &fn_name, arg);
        }
        self.drain_errors();
    }

    /// Closes the active scroll overlay, optionally dispatching a named choice
    /// back to the object that opened it via `send`.
    ///
    /// Call from the front-end when the player dismisses the scroll or selects a
    /// choice. If `choice` is `Some`, the source object receives a `send` call with
    /// that string as the function name (e.g. `"eat"` triggers `fn eat()`).
    pub fn close_scroll(&mut self, choice: Option<&str>) {
        let source = self.active_scroll.take().map(|s| s.source);
        if let (Some(src), Some(ch)) = (source, choice) {
            self.scripts.run_send(src, ch, None);
            self.drain_errors();
        }
    }

    /// Attempts to move the player one cell in `dir`.
    ///
    /// The move is ignored if the target cell is out of bounds, or it is neither
    /// passable nor a pushable solid that can be shoved aside. No-ops silently (the
    /// caller does not need to check). If the target cell holds a solid object, that
    /// object's `bump(-1)` hook fires (whether or not the player ends up moving).
    pub fn try_move(&mut self, dir: Direction) {
        let bumped;
        {
            let (dx, dy): (i32, i32) = dir.into();
            let mut board = self.board_mut();
            let target = (board.player.x + dx, board.player.y + dy);
            if !board.in_bounds(target) {
                return;
            }
            let (nx, ny) = (target.0 as usize, target.1 as usize);
            // A solid object in the way is bumped by the player (id -1).
            bumped = match board.solid_at(nx, ny) {
                Some(Solid::Object(_)) => board.solid_object_id_at(nx, ny),
                _ => None,
            };
            if board.is_passable(nx, ny) || board.can_push(nx, ny, dir) {
                board.push(nx, ny, dir); // shoves a crate/object out of the way; no-op otherwise
                board.player.x = nx as i32;
                board.player.y = ny as i32;
            }
        }
        if let Some(idx) = bumped {
            self.scripts.run_bump(idx, -1);
            self.drain_errors();
        }
    }
}

/// Moves object `id` one cell in `dir` on `board`, returning the [`ObjectId`] of a
/// solid object it bumped (its target cell was occupied by that object), if any.
///
/// The move itself proceeds only if the target is in bounds and either passable or a
/// pushable solid the object can shove out of the way (see [`Board::can_push`]). The
/// bump is recorded whenever a solid object occupies the target — whether it gets
/// pushed aside or blocks the move — since something tried to move into it. Walls and
/// crates carry no script, so only solid objects yield a bump.
fn step_object(board: &mut Board, id: ObjectId, dir: Direction) -> Option<ObjectId> {
    let (dx, dy): (i32, i32) = dir.into();
    let (ox, oy) = board.objects.get(&id).map(|o| (o.x, o.y))?;
    let target = (ox as i32 + dx, oy as i32 + dy);
    if !board.in_bounds(target) {
        return None;
    }
    let (nx, ny) = (target.0 as usize, target.1 as usize);
    // Capture the bumped object before any push relocates it (its id is stable).
    let bumped = match board.solid_at(nx, ny) {
        Some(Solid::Object(_)) => board.solid_object_id_at(nx, ny),
        _ => None,
    };
    if board.is_passable(nx, ny) || board.can_push(nx, ny, dir) {
        board.push(nx, ny, dir); // shoves a crate/object out of the way; no-op otherwise
        let obj = board.objects.get_mut(&id).expect("id checked above");
        obj.x = nx;
        obj.y = ny;
    }
    bumped
}