//! Aboard a derelict: the map, your status, and the log. The rules live in
//! `dungeon::crawl`; this turns keys into actions and draws the result,
//! including the line of fire while you aim, and shots in flight. `i` opens
//! the inventory (`scenes::inventory`), with what's on the floor beside it,
//! and `c` your character sheet, with what you carry here.

use ratatui::Frame;
use ratatui::buffer::Buffer;
use ratatui::crossterm::event::{KeyCode, KeyEvent};
use ratatui::layout::{Constraint, Flex, Layout, Rect};
use ratatui::style::{Color, Style, Stylize};
use ratatui::text::{Line, Span};
use ratatui::widgets::{Block, Borders, Clear, Padding, Paragraph, Wrap};

use super::character::Sheet;
use super::inventory::{self, Beside, Command, Inventory, Reply, View};
use super::keys::{self, direction};
use super::pause::{Choice, Pause};
use super::{Scene, Transition};
use crate::app::Ctx;
use crate::dungeon::arms::{Dmg, Weapon};
use crate::dungeon::crawl::{Action, Affinity, Crawl, Monster, Outcome, SIGHT_RADIUS, Trace};
use crate::dungeon::{Pos, Tile};
use crate::items::{self, Gear, Item, Stack};
use crate::seed;

const PANEL_WIDTH: u16 = 34;
const LOG_HEIGHT: u16 = 7;
/// How fast shots cross the screen: cells for every two ticks.
const SHOT_SPEED: u64 = 3;
/// How long a shot's impact shows, in cells' worth of flight.
const IMPACT: u64 = 6;
/// Most monsters listed as in view.
const IN_VIEW: usize = 6;
/// The most steps a run takes.
const RUN_LIMIT: usize = 80;

type Rgb = (u8, u8, u8);
/// Cells you've seen but can't see now.
const REMEMBERED: Rgb = (64, 68, 84);
/// The hull's outline, seen from outside as you docked.
const SILHOUETTE: Rgb = (40, 44, 60);
const STAR: Rgb = (72, 72, 92);
const LINE_OF_FIRE: Color = Color::Rgb(46, 40, 20);
const RETICLE: Color = Color::Rgb(160, 128, 40);

#[derive(Clone, Copy)]
enum Mode {
    Explore,
    /// Picking where to fire.
    Aim(Pos),
    /// Asking whether to leave by the emergency hatch.
    Abandon,
}

pub struct Derelict {
    crawl: Crawl,
    mode: Mode,
    /// Open over the map, when you're looking through what you carry.
    inventory: Option<Inventory>,
    /// What you came aboard with, to tell what you found.
    brought: Gear,
    /// Once the crawl is over: a title and lines for the closing summary.
    ending: Option<(&'static str, Vec<String>)>,
    /// The tick this turn's shots set off, for drawing them in flight.
    volley_at: u64,
    /// The menu `esc` opens.
    pause: Option<Pause>,
}

impl Derelict {
    pub fn new(seed: u64) -> Self {
        Derelict {
            crawl: Crawl::new(seed),
            mode: Mode::Explore,
            inventory: None,
            brought: Gear::default(),
            ending: None,
            volley_at: 0,
            pause: None,
        }
    }

    /// Back aboard the wreck a save left you in, just as you left it: what
    /// you carried, what you'd seen, what's still hunting you.
    pub fn resumed(ctx: &Ctx) -> Option<Derelict> {
        let mut crawl = Crawl::resume(ctx.crawl.as_ref()?)?;
        crawl.known.clone_from(&ctx.bestiary);
        crawl.say(format!("You're back aboard {}, where you left off.", crawl.name));
        let mut brought = ctx.hold.gear.clone();
        brought.reload_all();
        Some(Derelict {
            crawl,
            mode: Mode::Explore,
            inventory: None,
            brought,
            ending: None,
            volley_at: 0,
            pause: None,
        })
    }

    /// Boards a derelict with everything you carry. Whatever's left of it
    /// comes back with you if you get out; your own torch and rivet gun come
    /// back whatever happens. What's in your ship's lockers stays safe
    /// aboard. What you know about what lives aboard wrecks, you know here
    /// too.
    ///
    /// The hold isn't touched until the crawl ends. The crawl itself is
    /// kept in `ctx.crawl` after every move, so a game saved halfway
    /// through (or quit) comes back aboard the wreck.
    pub fn board(seed: u64, ctx: &mut Ctx) -> Self {
        let mut derelict = Derelict::new(seed);
        ctx.record.boarded += 1;
        let c = &mut derelict.crawl;
        c.gear = ctx.hold.gear.clone();
        c.gear.reload_all();
        c.known.clone_from(&ctx.bestiary);
        derelict.brought = c.gear.clone();
        let mut brought: Vec<String> =
            everything(&c.gear).iter().filter(|s| !s.item.is_kit()).map(Stack::name).collect();
        if !brought.is_empty() {
            if brought.len() > 4 {
                brought.truncate(3);
                brought.push("more".into());
            }
            let brought = listed(&brought);
            c.say(format!("You've brought {brought}."));
        }
        ctx.crawl = Some(derelict.crawl.saved());
        derelict
    }

    /// Takes a turn (or doesn't), and keeps up with what came of it.
    fn act(&mut self, action: Action, ctx: &mut Ctx) {
        self.crawl.act(action);
        if !self.crawl.volley.is_empty() {
            self.volley_at = ctx.ticks;
        }
        ctx.bestiary.extend(self.crawl.known.iter().copied());
        for kind in self.crawl.slain.drain(..) {
            *ctx.record.slain.entry(kind.to_string()).or_default() += 1;
        }
        ctx.crawl = self.crawl.outcome.is_none().then(|| self.crawl.saved());
        if let Some(outcome) = self.crawl.outcome
            && self.ending.is_none()
        {
            self.mode = Mode::Explore;
            self.finish(outcome, ctx);
        }
    }

    /// Called once, when the crawl ends: banks what you carried if you got
    /// out, and writes the summary.
    fn finish(&mut self, outcome: Outcome, ctx: &mut Ctx) {
        let c = &self.crawl;
        let lines = match outcome {
            Outcome::Escaped => {
                ctx.record.escaped += 1;
                ctx.hold.gear = c.gear.clone();
                let found = gained(&self.brought, &c.gear);
                let mut lines = vec![format!("You cast off from {}.", c.name), String::new()];
                if found.is_empty() {
                    lines.push("You come away with nothing new.".into());
                } else {
                    lines.push("You come away with:".into());
                    lines.extend(found.iter().map(|s| {
                        let (glyph, _) = inventory::look(&s.item);
                        format!("  {glyph} {}", s.name())
                    }));
                }
                let worth: u32 = found
                    .iter()
                    .map(|s| match &s.item {
                        Item::Salvage(v) => v.value * s.count,
                        _ => 0,
                    })
                    .sum();
                if worth > 0 {
                    lines.push(format!("The salvage is worth about {worth} ¤ to a broker."));
                }
                lines.push(String::new());
                lines.push(format!(
                    "You carry {} of {} kg. Stow what you don't need in the lockers [i].",
                    items::kg(c.gear.carried()),
                    items::kg(c.gear.capacity)
                ));
                lines
            }
            Outcome::Died { killer } => {
                ctx.record.downed += 1;
                ctx.hold.lose_carried(&c.gear);
                vec![
                    format!("The {killer} brings you down aboard {}.", c.name),
                    format!("Your crew drags you back to {}, but", ctx.character.ship_name()),
                    "everything you carried stays with the wreck.".into(),
                ]
            }
        };
        let title = match outcome {
            Outcome::Escaped => " SAFE ABOARD YOUR SHIP ",
            Outcome::Died { .. } => " PULLED BACK FROM THE EDGE ",
        };
        self.ending = Some((title, lines));
        // You may well be holding the key that walked you into the
        // airlock: its repeats mustn't wave the summary away unread.
        ctx.settle();
    }

    /// Shift and a direction: steps that way until there's something to
    /// stop for: something in sight, a wound, something said or underfoot,
    /// a doorway, another room, a closed door or the airlock ahead. With
    /// something in sight already, it's just a step.
    fn run(&mut self, dx: i32, dy: i32, ctx: &mut Ctx) {
        for step in 0..RUN_LIMIT {
            let c = &self.crawl;
            // Opening a door and leaving are steps you take, not ones a
            // run carries you into.
            let ahead = c.map.tile(c.player.offset(dx, dy));
            if step > 0 && matches!(ahead, Tile::Airlock | Tile::Door { open: false }) {
                break;
            }
            let (from, hp, said) = (c.player, c.hp, c.said);
            let room = c.map.room_index(c.player);
            self.act(Action::Move(dx, dy), ctx);
            let c = &self.crawl;
            let stop = c.outcome.is_some()
                || c.player == from
                || c.hp < hp
                || c.said != said
                || c.monsters.iter().any(|m| c.fov.contains(m.pos))
                || !c.here().is_empty()
                || matches!(c.map.tile(c.player), Tile::Door { .. })
                // Out of a doorway, the first step is into the room.
                || (step > 0 && c.map.room_index(c.player) != room);
            if stop {
                break;
            }
        }
    }

    fn explore(&mut self, code: KeyCode) -> Option<Action> {
        if let Some((dx, dy)) = direction(code) {
            return Some(Action::Move(dx, dy));
        }
        match code {
            KeyCode::Char('.' | '5') => Some(Action::Wait),
            KeyCode::Char('a') => Some(Action::UseMedpatch),
            KeyCode::Char('r') => Some(Action::Reload),
            KeyCode::Char('g' | ',') if self.crawl.here().len() > 1 => {
                self.inventory = Some(Inventory::beside());
                None
            }
            KeyCode::Char('g' | ',') => Some(Action::PickUp),
            KeyCode::Char('f') if self.crawl.gear.gun.loaded == 0 => Some(Action::Reload),
            KeyCode::Char('f') => {
                let at = self.targets().first().copied().unwrap_or(self.crawl.player);
                self.mode = Mode::Aim(at);
                None
            }
            KeyCode::Char('i') => {
                self.inventory = Some(Inventory::new());
                None
            }
            KeyCode::Esc => {
                let note = format!(
                    "Aboard {}. Quit, and you'll come back aboard just as you left it.",
                    self.crawl.name
                );
                self.pause = Some(Pause::new(Some("Abandon ship"), Some(note)));
                None
            }
            _ => None,
        }
    }

    fn aim(&mut self, code: KeyCode, at: Pos) -> Option<Action> {
        if let Some((dx, dy)) = direction(code) {
            let to = at.offset(dx, dy);
            if self.crawl.map.contains(to) {
                self.mode = Mode::Aim(to);
            }
            return None;
        }
        match code {
            KeyCode::Tab | KeyCode::Char('+' | '=') => self.mode = Mode::Aim(self.cycle(at, 1)),
            KeyCode::BackTab | KeyCode::Char('-') => self.mode = Mode::Aim(self.cycle(at, -1)),
            KeyCode::Enter | KeyCode::Char('f' | 't') if at != self.crawl.player => {
                self.mode = Mode::Explore;
                return Some(Action::Fire(at));
            }
            KeyCode::Esc | KeyCode::Char('q') => self.mode = Mode::Explore,
            _ => {}
        }
        None
    }

    /// Where the things you can see are, nearest first.
    fn targets(&self) -> Vec<Pos> {
        let c = &self.crawl;
        let mut targets: Vec<Pos> =
            c.monsters.iter().map(|m| m.pos).filter(|&p| c.fov.contains(p)).collect();
        targets.sort_by_key(|&p| (distance2(c.player, p), p.y, p.x));
        targets
    }

    /// The next target after (or before) the one at `at`.
    fn cycle(&self, at: Pos, by: isize) -> Pos {
        let targets = self.targets();
        match targets.iter().position(|&p| p == at) {
            _ if targets.is_empty() => at,
            Some(i) => targets[(i as isize + by).rem_euclid(targets.len() as isize) as usize],
            None => targets[0],
        }
    }

    fn render_map(&self, buf: &mut Buffer, area: Rect, ticks: u64) {
        let c = &self.crawl;
        let left = camera(c.player.x, c.map.width, i32::from(area.width));
        let top = camera(c.player.y, c.map.height, i32::from(area.height));
        let flying = self.in_flight(ticks);
        let (aim, line) = match self.mode {
            Mode::Aim(at) => (Some(at), c.line_of_fire(at)),
            _ => (None, Vec::new()),
        };
        for sy in 0..area.height {
            for sx in 0..area.width {
                let p = Pos::new(left + i32::from(sx), top + i32::from(sy));
                let (mut glyph, mut style) = self.look(p);
                if line.contains(&p) {
                    style = style.bg(LINE_OF_FIRE);
                }
                if aim == Some(p) {
                    style = style.bg(RETICLE);
                    if p != c.player && c.monster_at(p).is_none() {
                        (glyph, style) = ('×', style.fg(Color::Black));
                    }
                }
                if let Some(&(_, g, colour)) = flying.iter().find(|(q, ..)| *q == p) {
                    glyph = g;
                    style = style.fg(rgb(colour, 1.0)).bold();
                }
                if let Some(cell) = buf.cell_mut((area.x + sx, area.y + sy)) {
                    cell.set_char(glyph).set_style(style);
                }
            }
        }
    }

    /// What of this turn's shots is on screen `ticks` in: each round's head
    /// and a fading tail while it flies, then a flash where it stops.
    fn in_flight(&self, ticks: u64) -> Vec<(Pos, char, Rgb)> {
        let c = &self.crawl;
        let flown = ticks.saturating_sub(self.volley_at) * SHOT_SPEED / 2;
        let mut out = Vec::new();
        for trace in &c.volley {
            let Some(flown) = flown.checked_sub(u64::from(trace.delay)) else { continue };
            let (len, colour) = (trace.cells.len() as u64, trace.dmg.rgb());
            let Some(&end) = trace.cells.last() else { continue };
            if flown < len {
                out.push((trace.cells[flown as usize], shot_glyph(trace), colour));
                if flown > 0 {
                    out.push((trace.cells[flown as usize - 1], '·', dim(colour, 0.6)));
                }
            } else if flown < len + IMPACT {
                out.push((end, if trace.hit { '*' } else { '∙' }, colour));
            }
        }
        out.retain(|(p, ..)| c.fov.contains(*p));
        out
    }

    /// How the cell at `p` looks from where you stand: lit by your lamp if
    /// you can see it, from memory if you've seen it, and otherwise only the
    /// hull's outline against the stars.
    fn look(&self, p: Pos) -> (char, Style) {
        let c = &self.crawl;
        let tile = c.map.tile(p);
        if c.fov.contains(p) {
            if p == c.player {
                return ('@', Style::new().fg(Color::White).bold());
            }
            if let Some(m) = c.monster_at(p) {
                return (m.kind.glyph, Style::new().fg(rgb(m.kind.rgb, 1.0)).bold());
            }
            let dist = f64::from(distance2(p, c.player)).sqrt();
            let light = 1.0 - 0.6 * (dist / f64::from(SIGHT_RADIUS)).min(1.0);
            if let Some(loot) = c.loot_at(p) {
                let (glyph, colour) = inventory::look(&loot.stack.item);
                return (glyph, Style::new().fg(rgb(colour, light.max(0.8))).bold());
            }
            let (glyph, colour) = tile_look(tile);
            return (glyph, Style::new().fg(rgb(colour, light)));
        }
        if c.seen(p) {
            if let Some(loot) = c.loot_at(p) {
                let (glyph, colour) = inventory::look(&loot.stack.item);
                return (glyph, Style::new().fg(rgb(colour, 0.45)));
            }
            return (tile_look(tile).0, Style::new().fg(rgb(REMEMBERED, 1.0)));
        }
        match tile {
            Tile::Hull | Tile::Airlock => {
                (tile_look(tile).0, Style::new().fg(rgb(SILHOUETTE, 1.0)))
            }
            Tile::Void if is_star(p) => ('.', Style::new().fg(rgb(STAR, 1.0))),
            _ => (' ', Style::new()),
        }
    }

    fn render_panel(&self, frame: &mut Frame, area: Rect) {
        let c = &self.crawl;
        let block = Block::bordered()
            .border_style(Style::new().dark_gray())
            .title(Line::from(" DERELICT ").bold())
            .padding(Padding::horizontal(1));
        let inner = block.inner(area);
        frame.render_widget(block, area);
        let help = self.help(inner.width);
        let [info, keys] =
            Layout::vertical([Constraint::Fill(1), Constraint::Length(help.len() as u16)])
                .areas(inner);

        let mut lines = vec![
            Line::from(c.name.as_str()).bold().fg(Color::Yellow),
            Line::from(c.description.as_str()).italic().dark_gray(),
            Line::default(),
            Line::from(vec![label("health    "), health_bar(c.hp, c.max_hp, 12)]),
        ];
        if c.bleeding > 0 {
            lines.push(Line::from(vec![
                label("          "),
                format!("bleeding {}", c.bleeding).red(),
            ]));
        }
        if c.burning > 0 {
            lines.push(Line::from(vec![
                label("          "),
                Span::from(format!("alight {}", c.burning)).fg(rgb(Dmg::Burn.rgb(), 1.0)),
            ]));
        }
        lines.extend([
            Line::from(vec![label("medpatches"), Span::from(format!(" {}", c.gear.medpatches()))]),
            Line::from(vec![label("here      "), Span::from(c.location())]),
            Line::from(vec![label("turn      "), Span::from(c.turns.to_string())]),
            Line::default(),
        ]);

        let (blade, gun) = (&c.gear.melee, &c.gear.gun);
        let blade_stats = format!("{} · {}%", blade.damage_text(), percent(blade.accuracy));
        lines.extend([
            Line::from(vec![label("melee     "), title(blade, 20)]),
            Line::from(vec![label("          "), blade_stats.dark_gray()]),
            Line::from(vec![label("ranged    "), title(gun, 20)]),
            Line::from(vec![
                label("          "),
                magazine(gun),
                format!(" {}", gun.damage_text()).dark_gray(),
            ]),
            Line::from(vec![
                label("carrying  "),
                Span::from(format!(
                    "{} / {} kg",
                    items::kg(c.gear.carried()),
                    items::kg(c.gear.capacity)
                )),
            ]),
            Line::default(),
        ]);

        match self.mode {
            Mode::Aim(at) => self.target_lines(at, &mut lines),
            _ => self.in_view_lines(&mut lines),
        }

        let found = gained(&self.brought, &c.gear);
        if !found.is_empty() {
            lines.push(Line::from("found").dark_gray());
        }
        for stack in &found {
            let (glyph, colour) = inventory::look(&stack.item);
            lines.push(Line::from(vec![
                Span::from(format!("{glyph} ")).fg(rgb(colour, 1.0)),
                Span::from(stack.name()),
            ]));
        }
        frame.render_widget(Paragraph::new(lines).wrap(Wrap { trim: false }), info);
        frame.render_widget(Paragraph::new(help), keys);
    }

    /// The monsters you can see, nearest first, with how hurt they are.
    fn in_view_lines<'a>(&'a self, lines: &mut Vec<Line<'a>>) {
        let c = &self.crawl;
        let mut seen: Vec<&Monster> = c.monsters.iter().filter(|m| c.fov.contains(m.pos)).collect();
        if seen.is_empty() {
            return;
        }
        seen.sort_by_key(|m| distance2(c.player, m.pos));
        lines.push(Line::from("in view").dark_gray());
        for m in seen.iter().take(IN_VIEW) {
            let mut spans = vec![
                Span::styled(
                    m.kind.glyph.to_string(),
                    Style::new().fg(rgb(m.kind.rgb, 1.0)).bold(),
                ),
                Span::from(format!(" {:<18}", m.kind.name)),
                mini_bar(m.hp, m.kind.hp, 6),
            ];
            if m.bleeding > 0 {
                spans.push("•".red());
            }
            if m.burning > 0 {
                spans.push(Span::from("*").fg(rgb(Dmg::Burn.rgb(), 1.0)));
            }
            if m.stunned > 0 {
                spans.push("z".yellow());
            }
            lines.push(Line::from(spans));
        }
        if seen.len() > IN_VIEW {
            lines.push(Line::from(format!("  and {} more", seen.len() - IN_VIEW)).dark_gray());
        }
        lines.push(Line::default());
    }

    /// What's under the reticle: how hurt it is, the odds, and what you
    /// know of how it takes each kind of damage.
    fn target_lines<'a>(&'a self, at: Pos, lines: &mut Vec<Line<'a>>) {
        let c = &self.crawl;
        if at == c.player {
            lines.push(Line::from("Nothing in sight to shoot.").dark_gray());
            lines.push(Line::from("Aim with the move keys.").dark_gray());
            lines.push(Line::default());
            return;
        }
        let away = f64::from(distance2(c.player, at)).sqrt().round();
        let away =
            if away == 1.0 { "1 cell away".to_string() } else { format!("{away} cells away") };
        let Some(m) = c.monster_at(at).filter(|m| c.fov.contains(m.pos)) else {
            lines.push(Line::from(vec![label("target "), Span::from("nothing there")]));
            let range = if c.in_range(at) { "" } else { " · out of range" };
            lines.push(Line::from(format!("{away}{range}")).dark_gray());
            lines.push(Line::default());
            return;
        };
        let kind = m.kind;
        lines.push(Line::from(vec![
            label("target "),
            Span::styled(kind.name, Style::new().fg(rgb(kind.rgb, 1.0)).bold()),
        ]));
        let mut state = vec![mini_bar(m.hp, kind.hp, 12)];
        if m.bleeding > 0 {
            state.push(format!(" bleeding {}", m.bleeding).red());
        }
        if m.burning > 0 {
            state.push(Span::from(" burning").fg(rgb(Dmg::Burn.rgb(), 1.0)));
        }
        if m.stunned > 0 {
            state.push(" stunned".yellow());
        }
        lines.push(Line::from(state));
        let odds = match c.odds(at) {
            _ if !c.in_range(at) => "out of range".to_string(),
            Some(p) if c.gear.gun.gun.is_some_and(|g| g.pellets > 1) => {
                format!("{}% a pellet", percent(p))
            }
            Some(p) => format!("{}% to hit", percent(p)),
            None => String::new(),
        };
        lines.push(Line::from(format!("{away} · {odds}")).dark_gray());

        let mut known: [(Affinity, Vec<&str>); 4] = [
            (Affinity::Weak, Vec::new()),
            (Affinity::Resists, Vec::new()),
            (Affinity::Immune, Vec::new()),
            (Affinity::Normal, Vec::new()),
        ];
        let mut untried = Vec::new();
        for dmg in Dmg::ALL {
            match c.knows(kind, dmg) {
                Some(a) => known.iter_mut().find(|(k, _)| *k == a).unwrap().1.push(dmg.name()),
                None => untried.push(dmg.name()),
            }
        }
        for (affinity, dmgs) in known {
            if dmgs.is_empty() {
                continue;
            }
            let (word, colour) = match affinity {
                Affinity::Weak => ("weak to ", Color::Green),
                Affinity::Resists => ("resists ", Color::Yellow),
                Affinity::Immune => ("immune to ", Color::Red),
                Affinity::Normal => ("no matter: ", Color::Gray),
            };
            lines.push(Line::from(vec![Span::from(word).fg(colour), Span::from(dmgs.join(", "))]));
        }
        if !untried.is_empty() {
            lines.push(Line::from(format!("untried: {}", untried.join(", "))).dark_gray());
        }
        lines.push(Line::default());
    }

    fn help(&self, width: u16) -> Vec<Line<'static>> {
        let hints: &[(&str, &str)] = match self.mode {
            Mode::Aim(_) => &[
                ("move keys", "aim"),
                ("tab", "next target"),
                ("f enter", "fire"),
                ("esc", "lower it"),
            ],
            _ => &[
                ("arrows hjkl yubn", "move, attack"),
                ("shift", "run"),
                ("f", "fire"),
                ("r", "reload"),
                (".", "wait"),
                ("a", "medpatch"),
                ("g", "pick up"),
                ("i", "inventory"),
                ("c", "character"),
                ("into Θ", "leave with loot"),
                ("esc", "menu: quit or abandon ship"),
            ],
        };
        keys::packed(hints, width)
    }

    fn render_log(&self, frame: &mut Frame, area: Rect) {
        let log = &self.crawl.log;
        let shown = usize::from(area.height.saturating_sub(1));
        let first = log.len().saturating_sub(shown);
        let lines: Vec<Line> = log[first..]
            .iter()
            .enumerate()
            .map(|(i, message)| {
                let age = log.len() - first - 1 - i;
                let line = Line::from(message.as_str());
                match age {
                    0 => line.white(),
                    1 | 2 => line.gray(),
                    _ => line.dark_gray(),
                }
            })
            .collect();
        let block = Block::new().borders(Borders::TOP).border_style(Style::new().dark_gray());
        frame.render_widget(Paragraph::new(lines).block(block), area);
    }
}

/// Everything on you, as stacks: worn, ready and packed.
fn everything(gear: &Gear) -> Vec<Stack> {
    let worn = gear.worn.values().map(|a| Stack::one(Item::Armor(a.clone())));
    let ready = [&gear.melee, &gear.gun].into_iter().map(|w| Stack::one(Item::Weapon(w.clone())));
    worn.chain(ready).chain(gear.pack.iter().cloned()).collect()
}

/// What you have now that you didn't come aboard with.
fn gained(before: &Gear, after: &Gear) -> Vec<Stack> {
    // A gun you've fired is still the gun you brought.
    let unloaded = |mut s: Stack| {
        if let Item::Weapon(w) = &mut s.item {
            w.loaded = 0;
        }
        s
    };
    let mut had: Vec<Stack> = everything(before).into_iter().map(unloaded).collect();
    let mut found = Vec::new();
    for stack in everything(after).into_iter().map(unloaded) {
        let mut count = stack.count;
        if let Some(old) = had.iter_mut().find(|s| s.item == stack.item) {
            let same = old.count.min(count);
            old.count -= same;
            count -= same;
        }
        if count > 0 {
            items::stow(&mut found, Stack { count, ..stack });
        }
    }
    found
}

impl Scene for Derelict {
    fn key(&mut self, key: KeyEvent, ctx: &mut Ctx) -> Transition {
        if self.ending.is_some() {
            return Transition::Pop;
        }
        if let Some(pause) = &mut self.pause {
            return match pause.key(key) {
                None => Transition::None,
                Some(choice) => {
                    self.pause = None;
                    match choice {
                        Choice::Quit => Transition::Title,
                        Choice::Here => {
                            self.mode = Mode::Abandon;
                            Transition::None
                        }
                        Choice::Resume => Transition::None,
                    }
                }
            };
        }
        if let Some(inv) = &mut self.inventory {
            let here: Vec<Stack> =
                self.crawl.here().iter().map(|&i| self.crawl.loot[i].stack.clone()).collect();
            let view = View {
                gear: &self.crawl.gear,
                beside: (!here.is_empty()).then_some((Beside::Floor("on the floor"), &here[..])),
                known: &self.crawl.known,
                hurt: true,
                shop: None,
                sort: ctx.inventory_sort,
            };
            let action = match inv.key(key, &view) {
                Reply::Stay => return Transition::None,
                Reply::Close => {
                    self.inventory = None;
                    return Transition::None;
                }
                Reply::Sort(sort) => {
                    ctx.inventory_sort = sort;
                    return Transition::None;
                }
                Reply::Do(command) => match command {
                    Command::Ready(i) => Action::Ready(i),
                    Command::Wear(i) => Action::Wear(i),
                    Command::TakeOff(slot) => Action::TakeOff(slot),
                    Command::Eat(i) => Action::Eat(i),
                    Command::UseMedpatch => Action::UseMedpatch,
                    Command::Drop(spot, n) | Command::Stow(spot, n) => Action::Drop(spot, n),
                    Command::Fetch(i, n) => Action::Take(i, n),
                    // There's no one to trade with aboard a wreck.
                    Command::Buy(_)
                    | Command::Sell(_)
                    | Command::SellAboard(_)
                    | Command::Mend(_)
                    | Command::MendAboard(_)
                    | Command::MendAll => {
                        return Transition::None;
                    }
                },
            };
            let turns = self.crawl.turns;
            self.act(action, ctx);
            // Anything that took a turn closes it, so you see what happened.
            match &mut self.inventory {
                Some(_) if self.crawl.turns != turns || self.ending.is_some() => {
                    self.inventory = None;
                }
                Some(inv) => inv.note = self.crawl.log.last().cloned(),
                None => {}
            }
            return Transition::None;
        }
        let action = match self.mode {
            Mode::Abandon => {
                self.mode = Mode::Explore;
                return match key.code {
                    KeyCode::Char('y' | 'Y') => {
                        ctx.record.abandoned += 1;
                        ctx.hold.lose_carried(&self.crawl.gear);
                        ctx.crawl = None;
                        Transition::Pop
                    }
                    _ => Transition::None,
                };
            }
            Mode::Explore => match keys::movement(key) {
                Some((dx, dy, true)) => {
                    self.run(dx, dy, ctx);
                    return Transition::None;
                }
                _ if matches!(key.code, KeyCode::Char('c' | 'C')) => {
                    let gear = self.crawl.gear.clone();
                    return Transition::Push(Box::new(Sheet::aboard(&self.crawl.name, gear)));
                }
                _ => self.explore(key.code),
            },
            Mode::Aim(at) => self.aim(key.code, at),
        };
        if let Some(action) = action {
            self.act(action, ctx);
        }
        Transition::None
    }

    fn render(&self, frame: &mut Frame, ctx: &Ctx) {
        let [main, panel] =
            Layout::horizontal([Constraint::Fill(1), Constraint::Length(PANEL_WIDTH)])
                .areas(frame.area());
        let [map, log] =
            Layout::vertical([Constraint::Fill(1), Constraint::Length(LOG_HEIGHT)]).areas(main);
        self.render_map(frame.buffer_mut(), map, ctx.ticks);
        self.render_log(frame, log);
        self.render_panel(frame, panel);

        if let Some((title, lines)) = &self.ending {
            let mut lines: Vec<Line> = lines.iter().map(|l| Line::from(l.as_str())).collect();
            lines.extend([Line::default(), keys::line(&[("any key", "carry on")])]);
            popup(frame, title, lines);
            return;
        }
        match self.mode {
            Mode::Abandon => popup(
                frame,
                " ABANDON SHIP? ",
                vec![
                    Line::from(format!("Leave {} by the emergency hatch?", self.crawl.name)),
                    Line::from("Whatever you're carrying stays behind."),
                    Line::default(),
                    keys::line(&[("y", "abandon"), ("any other key", "keep exploring")]),
                ],
            ),
            Mode::Explore | Mode::Aim(_) => {}
        }
        if let Some(inv) = &self.inventory {
            let here: Vec<Stack> =
                self.crawl.here().iter().map(|&i| self.crawl.loot[i].stack.clone()).collect();
            let view = View {
                gear: &self.crawl.gear,
                beside: (!here.is_empty()).then_some((Beside::Floor("on the floor"), &here[..])),
                known: &self.crawl.known,
                hurt: true,
                shop: None,
                sort: ctx.inventory_sort,
            };
            inv.render(frame, frame.area(), &view);
        }
        if let Some(pause) = &self.pause {
            pause.render(frame, frame.area());
        }
    }
}

/// A round in flight, pointing the way it's going. Cells are about twice as
/// tall as they're wide, so the slope on screen is double the slope in cells.
fn shot_glyph(trace: &Trace) -> char {
    match trace.dmg {
        Dmg::Burn => return '•',
        Dmg::Shock => return '~',
        Dmg::Hymn => return '♪',
        _ => {}
    }
    let (Some(first), Some(last)) = (trace.cells.first(), trace.cells.last()) else { return '*' };
    let (dx, dy) = (f64::from(last.x - first.x), f64::from(last.y - first.y) * 2.0);
    let angle = dy.atan2(dx).to_degrees().rem_euclid(180.0);
    match angle {
        a if !(22.5..157.5).contains(&a) => '-',
        a if a < 67.5 => '\\',
        a if a < 112.5 => '|',
        _ => '/',
    }
}

/// The left or top edge of the view: keeps `focus` centred, but doesn't
/// scroll past the map's edges, and centres a map smaller than the view.
pub(crate) fn camera(focus: i32, map_size: i32, view_size: i32) -> i32 {
    if map_size <= view_size {
        -(view_size - map_size) / 2
    } else {
        (focus - view_size / 2).clamp(0, map_size - view_size)
    }
}

pub(crate) fn tile_look(tile: Tile) -> (char, Rgb) {
    match tile {
        Tile::Void => (' ', (0, 0, 0)),
        Tile::Hull => ('#', (122, 134, 160)),
        Tile::Wall => ('#', (152, 148, 136)),
        Tile::Floor => ('.', (124, 118, 104)),
        Tile::Debris => (',', (160, 126, 92)),
        Tile::Door { open: false } => ('+', (216, 170, 86)),
        Tile::Door { open: true } => ('\'', (216, 170, 86)),
        Tile::Airlock => ('Θ', (90, 222, 200)),
    }
}

/// A weapon's name in the colour of its damage, cut to `width`. Relics
/// stand out.
fn title(w: &Weapon, width: usize) -> Span<'static> {
    let name: String = w.name().chars().take(width).collect();
    let style = Style::new().fg(rgb(w.dmg.rgb(), 1.0));
    Span::styled(name, if w.named { style.bold() } else { style })
}

/// Rounds left, as pips.
fn magazine(gun: &Weapon) -> Span<'static> {
    let Some(g) = gun.gun else { return Span::from("") };
    if gun.loaded == 0 {
        return "empty (r)".red();
    }
    let pips = "▮".repeat(gun.loaded as usize) + &"▯".repeat((g.magazine - gun.loaded) as usize);
    Span::from(pips).white()
}

fn label(text: &'static str) -> Span<'static> {
    Span::from(text).dark_gray()
}

fn percent(p: f64) -> i32 {
    (p * 100.0).round() as i32
}

fn distance2(a: Pos, b: Pos) -> i32 {
    (a.x - b.x).pow(2) + (a.y - b.y).pow(2)
}

fn rgb((r, g, b): Rgb, light: f64) -> Color {
    let scale = |c: u8| (f64::from(c) * light).round() as u8;
    Color::Rgb(scale(r), scale(g), scale(b))
}

fn dim((r, g, b): Rgb, k: f64) -> Rgb {
    let scale = |c: u8| (f64::from(c) * k).round() as u8;
    (scale(r), scale(g), scale(b))
}

/// A sprinkling of stars that stays put as the view scrolls.
fn is_star(p: Pos) -> bool {
    let cell = (u64::from(p.x as u32) << 32) | u64::from(p.y as u32);
    seed::derive(cell, "star", 0).is_multiple_of(41)
}

fn health_bar(hp: i32, max: i32, width: i32) -> Span<'static> {
    let filled = (hp * width + max - 1) / max;
    let colour = match hp * 4 / max {
        3.. => Color::Green,
        2 => Color::Yellow,
        _ => Color::Red,
    };
    let bar = "█".repeat(filled as usize) + &"░".repeat((width - filled) as usize);
    Span::styled(format!("{bar} {hp}/{max}"), Style::new().fg(colour))
}

/// A monster's health, without the numbers: you can see how hurt it is,
/// not count its hit points.
fn mini_bar(hp: i32, max: i32, width: i32) -> Span<'static> {
    let hp = hp.clamp(0, max);
    let filled = ((hp * width + max - 1) / max).clamp(0, width);
    let colour = match hp * 4 / max {
        3.. => Color::Green,
        2 => Color::Yellow,
        _ => Color::Red,
    };
    let bar = "█".repeat(filled as usize) + &"░".repeat((width - filled) as usize);
    Span::styled(bar, Style::new().fg(colour))
}

fn listed(items: &[String]) -> String {
    match items {
        [] => String::new(),
        [one] => one.clone(),
        [rest @ .., last] => format!("{} and {last}", rest.join(", ")),
    }
}

fn popup(frame: &mut Frame, title: &str, lines: Vec<Line>) {
    let area = frame.area();
    let widest = lines.iter().map(Line::width).max().unwrap_or(0) as u16;
    let width = (widest + 4).max(title.chars().count() as u16 + 4).min(area.width);
    let height = (lines.len() as u16 + 2).min(area.height);
    let [popup] = Layout::horizontal([Constraint::Length(width)]).flex(Flex::Center).areas(area);
    let [popup] = Layout::vertical([Constraint::Length(height)]).flex(Flex::Center).areas(popup);
    let block = Block::bordered()
        .border_style(Style::new().fg(Color::Yellow))
        .title(Line::from(title.to_string()).bold())
        .padding(Padding::horizontal(1));
    frame.render_widget(Clear, popup);
    frame.render_widget(Paragraph::new(lines).block(block), popup);
}

#[cfg(test)]
mod tests {
    use ratatui::Terminal;
    use ratatui::backend::TestBackend;
    use ratatui::crossterm::event::KeyModifiers;

    use super::*;
    use crate::dungeon::arms::{self, Source};
    use crate::term::KeyboardCaps;
    use ratatui::crossterm::event::KeyCode as Key;

    fn ctx() -> Ctx {
        Ctx::new(1, KeyboardCaps { key_release: false })
    }

    fn press(scene: &mut Derelict, code: KeyCode, ctx: &mut Ctx) -> Transition {
        scene.key(KeyEvent::new(code, KeyModifiers::NONE), ctx)
    }

    fn screen(scene: &Derelict, ctx: &Ctx) -> String {
        let mut terminal = Terminal::new(TestBackend::new(100, 30)).unwrap();
        terminal.draw(|frame| scene.render(frame, ctx)).unwrap();
        terminal.backend().buffer().content().iter().map(|cell| cell.symbol()).collect()
    }

    /// The vi key that moves you onto the airlock from the starting cell.
    fn key_toward_airlock(scene: &Derelict) -> KeyCode {
        let c = &scene.crawl;
        let airlock = c.player.neighbours().find(|&n| c.map.tile(n) == Tile::Airlock).unwrap();
        KeyCode::Char(match (airlock.x - c.player.x, airlock.y - c.player.y) {
            (-1, -1) => 'y',
            (0, -1) => 'k',
            (1, -1) => 'u',
            (-1, 0) => 'h',
            (1, 0) => 'l',
            (-1, 1) => 'b',
            (0, 1) => 'j',
            _ => 'n',
        })
    }

    fn shifted(scene: &mut Derelict, code: KeyCode, ctx: &mut Ctx) -> Transition {
        scene.key(KeyEvent::new(code, KeyModifiers::SHIFT), ctx)
    }

    #[test]
    fn running_goes_until_something_happens_but_not_out_the_airlock() {
        let mut ctx = ctx();
        let mut scene = Derelict::board(3, &mut ctx);
        let start = scene.crawl.player;
        let toward = key_toward_airlock(&scene);
        let KeyCode::Char(c) = toward else { unreachable!() };
        let away = keys::direction(toward).map(|(dx, dy)| (-dx, -dy)).unwrap();
        let away = [
            Key::Left,
            Key::Right,
            Key::Up,
            Key::Down,
            Key::Home,
            Key::PageUp,
            Key::End,
            Key::PageDown,
        ]
        .into_iter()
        .find(|&k| keys::direction(k) == Some(away))
        .unwrap();
        shifted(&mut scene, away, &mut ctx);
        let ran = scene.crawl.player.steps_to(start);
        assert!(ran >= 1, "it gets going");
        assert_eq!(scene.crawl.turns, ran as u32, "a turn a step, straight on");
        // And back: it stops beside the airlock rather than go through.
        for _ in 0..ran {
            shifted(&mut scene, KeyCode::Char(c.to_ascii_uppercase()), &mut ctx);
            if scene.crawl.player == start {
                break;
            }
        }
        assert_eq!(scene.crawl.player, start);
        assert!(scene.crawl.outcome.is_none(), "still aboard");
        assert!(matches!(press(&mut scene, toward, &mut ctx), Transition::None));
        assert!(scene.crawl.outcome.is_some(), "a step of your own takes you out");
    }

    #[test]
    fn a_medpatch_is_a_and_the_sheet_is_c() {
        let mut ctx = ctx();
        let mut scene = Derelict::board(3, &mut ctx);
        scene.crawl.gear.add(medpatches(1));
        scene.crawl.hp -= 5;
        press(&mut scene, KeyCode::Char('a'), &mut ctx);
        assert_eq!(scene.crawl.gear.medpatches(), 0);
        assert!(matches!(press(&mut scene, KeyCode::Char('c'), &mut ctx), Transition::Push(_)));
    }

    fn medpatches(n: u32) -> Stack {
        Stack { item: Item::Medpatch, count: n }
    }

    fn salvage() -> Item {
        Item::Salvage(items::Salvage { title: "coil of wire".into(), value: 12, mass: 2000 })
    }

    #[test]
    fn escaping_banks_what_you_carry() {
        let mut ctx = ctx();
        let mut scene = Derelict::board(3, &mut ctx);
        scene.crawl.gear.add(Stack { item: salvage(), count: 2 });
        let toward = key_toward_airlock(&scene);
        assert!(matches!(press(&mut scene, toward, &mut ctx), Transition::None));
        assert_eq!(ctx.hold.gear.pack.iter().filter(|s| s.item == salvage()).count(), 1);
        let shown = screen(&scene, &ctx);
        assert!(shown.contains("SAFE ABOARD YOUR SHIP"));
        assert!(shown.contains("2 coils of wire") && shown.contains("24 ¤"), "{shown}");
        assert!(matches!(press(&mut scene, KeyCode::Char(' '), &mut ctx), Transition::Pop));
    }

    /// Esc, then the menu's second choice, then yes.
    fn abandon(scene: &mut Derelict, ctx: &mut Ctx) {
        press(scene, KeyCode::Esc, ctx);
        press(scene, KeyCode::Char('2'), ctx);
        press(scene, KeyCode::Char('y'), ctx);
    }

    #[test]
    fn abandoning_leaves_it_behind() {
        let mut ctx = ctx();
        let mut scene = Derelict::board(3, &mut ctx);
        scene.crawl.gear.add(Stack::one(salvage()));
        press(&mut scene, KeyCode::Esc, &mut ctx);
        assert!(screen(&scene, &ctx).contains("PAUSED"));
        press(&mut scene, KeyCode::Char('2'), &mut ctx);
        assert!(screen(&scene, &ctx).contains("ABANDON SHIP?"));
        assert!(matches!(press(&mut scene, KeyCode::Char('y'), &mut ctx), Transition::Pop));
        assert!(ctx.hold.gear.pack.iter().all(|s| s.item.is_kit()));
        assert!(ctx.crawl.is_none(), "nothing to come back to");
    }

    #[test]
    fn any_other_key_keeps_exploring() {
        let mut ctx = ctx();
        let mut scene = Derelict::new(3);
        press(&mut scene, KeyCode::Esc, &mut ctx);
        assert!(matches!(press(&mut scene, KeyCode::Char('q'), &mut ctx), Transition::None));
        assert!(!screen(&scene, &ctx).contains("PAUSED"));
        press(&mut scene, KeyCode::Esc, &mut ctx);
        press(&mut scene, KeyCode::Char('2'), &mut ctx);
        assert!(matches!(press(&mut scene, KeyCode::Char('x'), &mut ctx), Transition::None));
        assert!(!screen(&scene, &ctx).contains("ABANDON SHIP?"));
    }

    #[test]
    fn saving_and_quitting_brings_you_back_where_you_were() {
        let mut ctx = ctx();
        let mut scene = Derelict::board(3, &mut ctx);
        scene.crawl.gear.add(Stack::one(salvage()));
        let key = key_toward_airlock(&scene);
        // A step away from the airlock and back is a turn or two in.
        let away = match key {
            KeyCode::Char('h') => KeyCode::Char('l'),
            KeyCode::Char('l') => KeyCode::Char('h'),
            KeyCode::Char('j') => KeyCode::Char('k'),
            _ => KeyCode::Char('j'),
        };
        press(&mut scene, away, &mut ctx);
        press(&mut scene, KeyCode::Char('.'), &mut ctx);
        press(&mut scene, KeyCode::Esc, &mut ctx);
        assert!(matches!(press(&mut scene, KeyCode::Char('3'), &mut ctx), Transition::Title));
        let saved = ctx.crawl.clone().expect("the wreck is kept");
        assert_eq!(saved, scene.crawl.saved());

        let back = Derelict::resumed(&ctx).unwrap();
        let (was, is) = (&scene.crawl, &back.crawl);
        assert_eq!((is.player, is.hp, is.turns), (was.player, was.hp, was.turns));
        assert_eq!(is.gear, was.gear);
        assert_eq!(is.loot, was.loot);
        assert_eq!(is.monsters.len(), was.monsters.len());
        assert!(is.log.last().unwrap().contains("where you left off"));
        assert_eq!(back.brought, ctx.hold.gear, "what's found is what you didn't bring");
        assert_eq!(ctx.record.boarded, 1, "coming back isn't boarding again");
        let seen = |c: &Crawl| c.map.positions().filter(|&p| c.seen(p)).count();
        assert_eq!(seen(is), seen(was), "what you'd seen you still have");
        assert!(was.map.positions().all(|p| is.seen(p) == was.seen(p)));
    }

    #[test]
    fn medpatches_go_aboard_and_come_back_if_you_do() {
        let mut ctx = ctx();
        ctx.hold.gear.add(medpatches(3));
        ctx.hold.lockers.push(medpatches(4));
        let mut scene = Derelict::board(3, &mut ctx);
        assert_eq!((scene.crawl.gear.medpatches(), ctx.hold.medpatches()), (3, 7));
        let key = key_toward_airlock(&scene);
        press(&mut scene, key, &mut ctx);
        assert_eq!(scene.crawl.outcome, Some(Outcome::Escaped));
        assert_eq!(ctx.hold.gear.medpatches(), 3);

        let mut scene = Derelict::board(3, &mut ctx);
        abandon(&mut scene, &mut ctx);
        assert_eq!(ctx.hold.gear.medpatches(), 0, "abandon ship and they stay behind");
        assert_eq!(ctx.hold.medpatches(), 4, "but not what's in the lockers");
    }

    #[test]
    fn weapons_go_aboard_and_come_back_if_you_do() {
        let mut ctx = ctx();
        let mut cleaver = arms::find(&mut seed::rng(2), Source::Crew, false);
        cleaver.loaded = 0;
        ctx.hold.gear.add(Stack::one(Item::Weapon(cleaver.clone())));
        let found = |g: &Gear| g.weapons().filter(|w| !w.kit).count();
        let mut scene = Derelict::board(3, &mut ctx);
        assert_eq!((found(&scene.crawl.gear), found(&ctx.hold.gear)), (1, 1));
        assert!(scene.crawl.gear.weapons().all(|w| w.loaded == w.gun.map_or(0, |g| g.magazine)));
        let key = key_toward_airlock(&scene);
        press(&mut scene, key, &mut ctx);
        assert_eq!(found(&ctx.hold.gear), 1);
        assert!(screen(&scene, &ctx).contains("nothing new"), "what you brought isn't found");

        let mut scene = Derelict::board(3, &mut ctx);
        abandon(&mut scene, &mut ctx);
        assert_eq!(found(&ctx.hold.gear), 0, "abandon ship and it stays behind");
        assert_eq!(ctx.hold.gear.weapons().count(), 2, "but not your own torch and rivet gun");
    }

    #[test]
    fn aiming_and_the_inventory_open_and_close() {
        let mut ctx = ctx();
        let mut scene = Derelict::new(3);
        press(&mut scene, KeyCode::Char('f'), &mut ctx);
        assert!(matches!(scene.mode, Mode::Aim(_)));
        assert!(screen(&scene, &ctx).contains("next target"));
        press(&mut scene, KeyCode::Esc, &mut ctx);
        assert!(matches!(scene.mode, Mode::Explore));
        assert_eq!(scene.crawl.turns, 0, "lowering your gun takes no time");

        press(&mut scene, KeyCode::Char('i'), &mut ctx);
        let shown = screen(&scene, &ctx);
        assert!(shown.contains("YOU ·") && shown.contains("cutting torch"), "{shown}");
        press(&mut scene, KeyCode::Char('j'), &mut ctx);
        assert_eq!(scene.crawl.turns, 0, "looking takes no time");
        press(&mut scene, KeyCode::Esc, &mut ctx);
        assert!(scene.inventory.is_none());
    }

    #[test]
    fn using_things_from_the_inventory_takes_a_turn_and_closes_it() {
        let mut ctx = ctx();
        let mut scene = Derelict::new(3);
        scene.crawl.gear.add(Stack::one(salvage()));
        scene.crawl.gear.add(medpatches(1));
        scene.crawl.hp -= 5;
        press(&mut scene, KeyCode::Char('i'), &mut ctx);
        find(&mut scene, "coil", &mut ctx);
        press(&mut scene, KeyCode::Char('d'), &mut ctx);
        assert_eq!(scene.crawl.turns, 0, "dropping is free");
        assert!(scene.inventory.is_some(), "and leaves it open");
        assert_eq!(scene.crawl.here().len(), 1);
        find(&mut scene, "medpatch", &mut ctx);
        press(&mut scene, KeyCode::Char('a'), &mut ctx);
        assert_eq!(scene.crawl.turns, 1, "a medpatch takes a turn");
        assert!(scene.inventory.is_none(), "and closes it");
    }

    /// Picks out the first thing in the open inventory called `what`.
    fn find(scene: &mut Derelict, what: &str, ctx: &mut Ctx) {
        press(scene, KeyCode::Char('/'), ctx);
        press(scene, KeyCode::Esc, ctx);
        press(scene, KeyCode::Char('/'), ctx);
        for c in what.chars() {
            press(scene, KeyCode::Char(c), ctx);
        }
        press(scene, KeyCode::Enter, ctx);
    }

    #[test]
    fn firing_takes_a_turn_and_spends_a_round() {
        let mut ctx = ctx();
        let mut scene = Derelict::new(3);
        press(&mut scene, KeyCode::Char('f'), &mut ctx);
        scene.mode = Mode::Aim(scene.crawl.player.offset(2, 0));
        ctx.ticks = 100;
        press(&mut scene, KeyCode::Char('f'), &mut ctx);
        assert_eq!(scene.crawl.turns, 1);
        assert_eq!(scene.crawl.gear.gun.loaded, scene.crawl.gear.gun.gun.unwrap().magazine - 1);
        assert!(!scene.crawl.volley.is_empty());
        assert_eq!(scene.volley_at, 100);
        assert!(scene.in_flight(100_000).is_empty(), "long since landed");
    }

    #[test]
    fn your_record_counts_wrecks_kills_and_how_you_left_them() {
        let mut ctx = ctx();
        let mut scene = Derelict::board(3, &mut ctx);
        let kind = scene.crawl.monsters[0].kind.name;
        scene.crawl.monsters[0].hp = 0;
        press(&mut scene, KeyCode::Char('.'), &mut ctx);
        assert_eq!(ctx.record.slain.get(kind), Some(&1));
        let key = key_toward_airlock(&scene);
        press(&mut scene, key, &mut ctx);

        let mut scene = Derelict::board(3, &mut ctx);
        abandon(&mut scene, &mut ctx);

        ctx.hold.gear.add(medpatches(2));
        let mut scene = Derelict::board(3, &mut ctx);
        scene.crawl.bleeding = 100;
        press(&mut scene, KeyCode::Char('.'), &mut ctx);
        assert!(matches!(scene.crawl.outcome, Some(Outcome::Died { .. })));
        assert!(screen(&scene, &ctx).contains(&ctx.character.ship_name()));
        assert_eq!(ctx.hold.gear.medpatches(), 0, "brought down, and they stay behind");

        let r = &ctx.record;
        assert_eq!((r.boarded, r.escaped, r.abandoned, r.downed), (3, 1, 1, 1));
    }

    #[test]
    fn until_you_leave_the_wreck_your_hold_is_as_you_left_it() {
        let mut ctx = ctx();
        ctx.hold.gear.add(medpatches(2));
        let mut scene = Derelict::board(3, &mut ctx);
        scene.crawl.gear = Gear::default();
        press(&mut scene, KeyCode::Char('.'), &mut ctx);
        assert_eq!(ctx.hold.gear.medpatches(), 2, "so a game saved now still has them");
    }

    #[test]
    fn what_you_learn_you_keep() {
        let mut ctx = ctx();
        let mut scene = Derelict::board(3, &mut ctx);
        scene.crawl.known.insert(("rust-mite", Dmg::Blunt));
        press(&mut scene, KeyCode::Char('.'), &mut ctx);
        assert!(ctx.bestiary.contains(&("rust-mite", Dmg::Blunt)));
        let scene = Derelict::board(4, &mut ctx);
        assert!(scene.crawl.known.contains(&("rust-mite", Dmg::Blunt)));
    }
}