feat(city): app loop, terminal guard, save format, gen CLI

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

crates/city/src/app.rs

@@ -0,0 +1,190 @@
+//! Application state, the screen trait and the fixed-rate frame loop.
+
+use crate::term::{TerminalGuard, install_panic_hook};
+use anyhow::Result;
+use citygen::{City, GenParams};
+use crossterm::event::{self, Event, KeyEvent, KeyEventKind};
+use ratatui::Frame;
+use ratatui::buffer::Buffer;
+use ratatui::layout::{Alignment, Rect};
+use ratatui::style::{Color, Style};
+use ratatui::widgets::Paragraph;
+use std::time::{Duration, Instant};
+
+pub const MIN_W: u16 = 100;
+pub const MIN_H: u16 = 30;
+pub const FRAME: Duration = Duration::from_micros(33_333);
+
+/// State shared by every screen.
+pub struct AppState {
+    pub params: GenParams,
+    pub city: Option<City>,
+    pub tick: u64,
+    status: Option<(String, u64)>,
+}
+
+impl Default for AppState {
+    fn default() -> Self {
+        Self::new()
+    }
+}
+
+impl AppState {
+    pub fn new() -> Self {
+        AppState {
+            params: GenParams::default(),
+            city: None,
+            tick: 0,
+            status: None,
+        }
+    }
+
+    /// Shows a one-line message for `ttl` ticks.
+    pub fn set_status(&mut self, msg: impl Into<String>, ttl: u64) {
+        self.status = Some((msg.into(), self.tick + ttl));
+    }
+
+    pub fn status_text(&self) -> Option<&str> {
+        match &self.status {
+            Some((msg, until)) if *until > self.tick => Some(msg.as_str()),
+            _ => None,
+        }
+    }
+}
+
+/// How a screen change is animated. Replaced by `ui::transition` later.
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub enum TransitionKind {
+    None,
+    Glitch,
+    SlideUp,
+}
+
+/// Placeholder transition: inactive until the ui module lands.
+pub struct Transition;
+
+impl Transition {
+    pub fn new(_kind: TransitionKind, _from: Buffer, _start: u64) -> Self {
+        Transition
+    }
+    pub fn active(&self, _tick: u64) -> bool {
+        false
+    }
+    pub fn apply(&self, _f: &mut Frame, _tick: u64) {}
+}
+
+/// What a screen asks the loop to do after an update.
+pub enum ScreenCmd {
+    Stay,
+    Switch {
+        to: Box<dyn Screen>,
+        fx: TransitionKind,
+    },
+    Quit,
+}
+
+pub trait Screen {
+    fn update(&mut self, st: &mut AppState, keys: &[KeyEvent]) -> ScreenCmd;
+    fn draw(&self, st: &AppState, f: &mut Frame);
+}
+
+/// Centered notice for terminals under the minimum size. Never panics, even at 1x1.
+pub fn draw_too_small(f: &mut Frame) {
+    let area = f.area();
+    let msg = format!(
+        "resize to at least {MIN_W}x{MIN_H} (now {}x{})",
+        area.width, area.height
+    );
+    let y = area.height / 2;
+    let line = Rect::new(area.x, area.y + y, area.width, 1.min(area.height));
+    f.render_widget(
+        Paragraph::new(msg)
+            .alignment(Alignment::Center)
+            .style(Style::default().fg(Color::Rgb(255, 80, 120))),
+        line,
+    );
+}
+
+/// The fixed-rate loop: poll input, tick, update, draw.
+pub fn run(mut screen: Box<dyn Screen>, mut st: AppState) -> Result<()> {
+    install_panic_hook();
+    let (_guard, mut term) = TerminalGuard::enter()?;
+    let mut transition: Option<Transition> = None;
+    loop {
+        let start = Instant::now();
+        let mut keys = Vec::new();
+        while event::poll(Duration::ZERO)? {
+            if let Event::Key(k) = event::read()?
+                && k.kind == KeyEventKind::Press
+            {
+                keys.push(k);
+            }
+        }
+        st.tick += 1;
+        if transition.as_ref().is_some_and(|t| t.active(st.tick)) && !keys.is_empty() {
+            transition = None;
+        }
+        match screen.update(&mut st, &keys) {
+            ScreenCmd::Stay => {}
+            ScreenCmd::Switch { to, fx } => {
+                let snapshot = term.current_buffer_mut().clone();
+                screen = to;
+                transition = Some(Transition::new(fx, snapshot, st.tick));
+            }
+            ScreenCmd::Quit => break,
+        }
+        term.draw(|f| {
+            if f.area().width < MIN_W || f.area().height < MIN_H {
+                draw_too_small(f);
+                return;
+            }
+            screen.draw(&st, f);
+            if let Some(t) = &transition {
+                t.apply(f, st.tick);
+            }
+        })?;
+        if let Some(rest) = FRAME.checked_sub(start.elapsed()) {
+            std::thread::sleep(rest);
+        }
+    }
+    Ok(())
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use ratatui::Terminal;
+    use ratatui::backend::TestBackend;
+
+    fn text(t: &Terminal<TestBackend>) -> String {
+        let b = t.backend().buffer();
+        let mut s = String::new();
+        for y in 0..b.area.height {
+            for x in 0..b.area.width {
+                s.push_str(b[(x, y)].symbol());
+            }
+            s.push('\n');
+        }
+        s
+    }
+
+    #[test]
+    fn too_small_message_never_panics() {
+        for (w, h) in [(1u16, 1u16), (99, 29), (10, 2)] {
+            let mut t = Terminal::new(TestBackend::new(w, h)).unwrap();
+            t.draw(draw_too_small).unwrap();
+        }
+        let mut t = Terminal::new(TestBackend::new(99, 29)).unwrap();
+        t.draw(draw_too_small).unwrap();
+        assert!(text(&t).contains("100"));
+    }
+
+    #[test]
+    fn app_state_status_expires() {
+        let mut st = AppState::new();
+        st.set_status("hi", 10);
+        assert_eq!(st.status_text(), Some("hi"));
+        st.tick += 11;
+        assert_eq!(st.status_text(), None);
+    }
+}

crates/city/src/cli.rs

@@ -0,0 +1,132 @@
+//! Command line: interactive app by default, `gen` for headless generation.
+
+use crate::app::{self, AppState};
+use crate::save::save_city;
+use anyhow::{Context, Result, bail};
+use citygen::{GenParams, Generator, SizePreset, WaterMode};
+use clap::{Parser, Subcommand};
+use std::path::PathBuf;
+
+#[derive(Parser)]
+#[command(
+    name = "city",
+    about = "Generate, explore and walk a cyberpunk city in the terminal"
+)]
+pub struct Cli {
+    #[command(subcommand)]
+    cmd: Option<Cmd>,
+}
+
+#[derive(Subcommand)]
+pub enum Cmd {
+    /// Generate a city headlessly and write it to a file.
+    Gen {
+        /// Seed; random when omitted.
+        #[arg(long)]
+        seed: Option<u64>,
+        /// small, medium, large or WxH.
+        #[arg(long, default_value = "medium")]
+        size: String,
+        #[arg(long)]
+        districts: Option<u8>,
+        /// none, bay or river.
+        #[arg(long)]
+        water: Option<String>,
+        #[arg(long)]
+        density: Option<f32>,
+        /// Output path (.city, or .json with --json).
+        #[arg(long)]
+        out: PathBuf,
+        /// Write pretty JSON instead of the binary format.
+        #[arg(long)]
+        json: bool,
+    },
+}
+
+pub fn parse_size(s: &str) -> Result<SizePreset> {
+    match s {
+        "small" => Ok(SizePreset::Small),
+        "medium" => Ok(SizePreset::Medium),
+        "large" => Ok(SizePreset::Large),
+        other => {
+            let (w, h) = other
+                .split_once('x')
+                .with_context(|| format!("size `{other}` is not small/medium/large or WxH"))?;
+            Ok(SizePreset::Custom {
+                w: w.parse().context("bad width")?,
+                h: h.parse().context("bad height")?,
+            })
+        }
+    }
+}
+
+pub fn parse_water(s: &str) -> Result<WaterMode> {
+    match s {
+        "none" => Ok(WaterMode::None),
+        "bay" => Ok(WaterMode::Bay),
+        "river" => Ok(WaterMode::River),
+        other => bail!("water `{other}` is not none/bay/river"),
+    }
+}
+
+fn random_seed() -> u64 {
+    let nanos = std::time::SystemTime::now()
+        .duration_since(std::time::UNIX_EPOCH)
+        .map(|d| d.as_nanos() as u64)
+        .unwrap_or(0);
+    citygen::rng::hash64(nanos, std::process::id() as u64)
+}
+
+pub fn run() -> Result<()> {
+    let cli = Cli::parse();
+    match cli.cmd {
+        None => app::run(Box::new(crate::screens::initial()), AppState::new()),
+        Some(Cmd::Gen {
+            seed,
+            size,
+            districts,
+            water,
+            density,
+            out,
+            json,
+        }) => {
+            let mut params = GenParams {
+                seed: seed.unwrap_or_else(random_seed),
+                size: parse_size(&size)?,
+                ..Default::default()
+            };
+            if let Some(d) = districts {
+                params.districts = d;
+            }
+            if let Some(w) = water {
+                params.water = parse_water(&w)?;
+            }
+            if let Some(d) = density {
+                params.density = d;
+            }
+            params.validate()?;
+            let city = Generator::run(params)?;
+            if json {
+                let file = std::fs::File::create(&out)
+                    .with_context(|| format!("creating {}", out.display()))?;
+                serde_json::to_writer_pretty(file, &city)?;
+            } else {
+                save_city(&out, &city)?;
+            }
+            let bytes = std::fs::metadata(&out).map(|m| m.len()).unwrap_or(0);
+            println!(
+                "{} seed {} {}x{} districts {} buildings {} nodes {} -> {} ({} bytes)",
+                city.name,
+                city.seed,
+                city.size.w,
+                city.size.h,
+                city.districts.len(),
+                city.buildings.len(),
+                city.net.nodes.len(),
+                out.display(),
+                bytes
+            );
+            Ok(())
+        }
+    }
+}

crates/city/src/main.rs

@@ -1,3 +1,14 @@
-fn main() {
+//! `city`: generate, explore and walk a cyberpunk city in the terminal.
-    println!("city");
+
+// Screens, widgets and overlays land task by task; lifted once the app is wired up.
+#![allow(dead_code)]
+
+mod app;
+mod cli;
+mod save;
+mod screens;
+mod term;
+
+fn main() -> anyhow::Result<()> {
+    cli::run()
 }

crates/city/src/save.rs

@@ -0,0 +1,198 @@
+//! The `.city` file format: magic, version, header, postcard body.
+
+use anyhow::{Context, Result, bail};
+use citygen::{City, Size};
+use serde::{Deserialize, Serialize};
+use std::path::{Path, PathBuf};
+use std::time::SystemTime;
+
+pub const MAGIC: &[u8; 4] = b"CITY";
+pub const FORMAT_VERSION: u16 = 1;
+
+#[derive(Debug, Serialize, Deserialize)]
+struct Header {
+    name: String,
+    seed: u64,
+    w: u32,
+    h: u32,
+}
+
+/// What the file list shows for one saved city.
+#[derive(Clone, Debug)]
+pub struct CityFileInfo {
+    pub path: PathBuf,
+    pub name: String,
+    pub seed: u64,
+    pub size: Size,
+    pub modified: SystemTime,
+}
+
+/// Where cities are saved by default.
+pub fn default_dir() -> PathBuf {
+    PathBuf::from("cities")
+}
+
+pub fn save_city(path: &Path, city: &City) -> Result<()> {
+    let header = Header {
+        name: city.name.clone(),
+        seed: city.seed,
+        w: city.size.w,
+        h: city.size.h,
+    };
+    let header_bytes = postcard::to_allocvec(&header)?;
+    let body = postcard::to_allocvec(city)?;
+    let mut out = Vec::with_capacity(10 + header_bytes.len() + body.len());
+    out.extend_from_slice(MAGIC);
+    out.extend_from_slice(&FORMAT_VERSION.to_le_bytes());
+    out.extend_from_slice(&(header_bytes.len() as u32).to_le_bytes());
+    out.extend_from_slice(&header_bytes);
+    out.extend_from_slice(&body);
+    if let Some(parent) = path.parent()
+        && !parent.as_os_str().is_empty()
+    {
+        std::fs::create_dir_all(parent)
+            .with_context(|| format!("creating {}", parent.display()))?;
+    }
+    std::fs::write(path, out).with_context(|| format!("writing {}", path.display()))?;
+    Ok(())
+}
+
+/// Splits a file into (header, body) after checking magic and version.
+fn split<'a>(bytes: &'a [u8], path: &Path) -> Result<(Header, &'a [u8])> {
+    if bytes.len() < 10 || &bytes[0..4] != MAGIC {
+        bail!("{} is not a .city file", path.display());
+    }
+    let version = u16::from_le_bytes([bytes[4], bytes[5]]);
+    if version != FORMAT_VERSION {
+        bail!(
+            "{} is .city version {version}; this build reads version {FORMAT_VERSION}",
+            path.display()
+        );
+    }
+    let header_len = u32::from_le_bytes([bytes[6], bytes[7], bytes[8], bytes[9]]) as usize;
+    let header_end = 10 + header_len;
+    if bytes.len() < header_end {
+        bail!("{} is truncated", path.display());
+    }
+    let header: Header = postcard::from_bytes(&bytes[10..header_end])
+        .with_context(|| format!("{}: corrupt header", path.display()))?;
+    Ok((header, &bytes[header_end..]))
+}
+
+pub fn load_city(path: &Path) -> Result<City> {
+    let bytes = std::fs::read(path).with_context(|| format!("reading {}", path.display()))?;
+    let (_, body) = split(&bytes, path)?;
+    let city: City = postcard::from_bytes(body)
+        .with_context(|| format!("{}: corrupt or truncated city data", path.display()))?;
+    Ok(city)
+}
+
+/// Lists `.city` files in `dir`, newest first. A missing directory lists as empty.
+pub fn list_cities(dir: &Path) -> Result<Vec<CityFileInfo>> {
+    let mut out = Vec::new();
+    let entries = match std::fs::read_dir(dir) {
+        Ok(e) => e,
+        Err(e) if e.kind() == std::io::ErrorKind::NotFound => return Ok(out),
+        Err(e) => return Err(e).with_context(|| format!("listing {}", dir.display())),
+    };
+    for entry in entries {
+        let entry = entry?;
+        let path = entry.path();
+        if path.extension().and_then(|e| e.to_str()) != Some("city") {
+            continue;
+        }
+        let Ok(bytes) = std::fs::read(&path) else {
+            continue;
+        };
+        let Ok((header, _)) = split(&bytes, &path) else {
+            continue;
+        };
+        let modified = entry
+            .metadata()
+            .and_then(|m| m.modified())
+            .unwrap_or(SystemTime::UNIX_EPOCH);
+        out.push(CityFileInfo {
+            path,
+            name: header.name,
+            seed: header.seed,
+            size: Size {
+                w: header.w,
+                h: header.h,
+            },
+            modified,
+        });
+    }
+    out.sort_by(|a, b| b.modified.cmp(&a.modified).then(a.path.cmp(&b.path)));
+    Ok(out)
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use citygen::{GenParams, Generator, SizePreset};
+
+    fn tiny() -> citygen::City {
+        Generator::run(GenParams {
+            seed: 5,
+            size: SizePreset::Custom { w: 80, h: 40 },
+            districts: 4,
+            ..Default::default()
+        })
+        .unwrap()
+    }
+
+    fn tmp(name: &str) -> std::path::PathBuf {
+        let dir = std::env::temp_dir().join(format!("city-test-{}-{name}", std::process::id()));
+        std::fs::create_dir_all(&dir).unwrap();
+        dir
+    }
+
+    #[test]
+    fn roundtrip_and_header() {
+        let c = tiny();
+        let dir = tmp("rt");
+        let path = dir.join("a.city");
+        save_city(&path, &c).unwrap();
+        let back = load_city(&path).unwrap();
+        assert_eq!(
+            postcard::to_allocvec(&c).unwrap(),
+            postcard::to_allocvec(&back).unwrap()
+        );
+        let list = list_cities(&dir).unwrap();
+        assert_eq!(list.len(), 1);
+        assert_eq!(list[0].seed, 5);
+        assert_eq!(list[0].name, c.name);
+        assert_eq!(list[0].size.w, 80);
+        assert!(list_cities(&dir.join("missing")).unwrap().is_empty());
+    }
+
+    #[test]
+    fn rejects_bad_magic_version_and_truncation() {
+        let dir = tmp("bad");
+        let p = dir.join("x.city");
+        std::fs::write(&p, b"NOPE\x01\x00").unwrap();
+        assert!(
+            load_city(&p)
+                .unwrap_err()
+                .to_string()
+                .contains("not a .city file")
+        );
+        let mut bytes = b"CITY".to_vec();
+        bytes.extend_from_slice(&99u16.to_le_bytes());
+        bytes.extend_from_slice(&0u32.to_le_bytes());
+        std::fs::write(&p, &bytes).unwrap();
+        assert!(
+            load_city(&p)
+                .unwrap_err()
+                .to_string()
+                .contains("version 99")
+        );
+        let c = tiny();
+        save_city(&p, &c).unwrap();
+        let full = std::fs::read(&p).unwrap();
+        std::fs::write(&p, &full[..full.len() / 2]).unwrap();
+        assert!(load_city(&p).is_err());
+        std::fs::write(&p, b"CI").unwrap();
+        assert!(load_city(&p).is_err());
+    }
+}

crates/city/src/screens/mod.rs

@@ -0,0 +1,48 @@
+//! Screens: one module per screen, plus shared test helpers.
+
+use crate::app::{AppState, Screen, ScreenCmd};
+use crossterm::event::{KeyCode, KeyEvent};
+use ratatui::Frame;
+
+/// Draws nothing; stands in until the title screen lands.
+pub struct Blank;
+
+impl Screen for Blank {
+    fn update(&mut self, _st: &mut AppState, keys: &[KeyEvent]) -> ScreenCmd {
+        if keys
+            .iter()
+            .any(|k| matches!(k.code, KeyCode::Char('q') | KeyCode::Esc))
+        {
+            ScreenCmd::Quit
+        } else {
+            ScreenCmd::Stay
+        }
+    }
+    fn draw(&self, _st: &AppState, _f: &mut Frame) {}
+}
+
+/// The screen the app starts on.
+pub fn initial() -> impl Screen {
+    Blank
+}
+
+#[cfg(test)]
+pub(crate) mod testutil {
+    use crossterm::event::{KeyCode, KeyEvent, KeyModifiers};
+    use ratatui::buffer::Buffer;
+
+    pub fn key(code: KeyCode) -> KeyEvent {
+        KeyEvent::new(code, KeyModifiers::NONE)
+    }
+
+    pub fn buffer_text(b: &Buffer) -> String {
+        let mut s = String::new();
+        for y in 0..b.area.height {
+            for x in 0..b.area.width {
+                s.push_str(b[(x, y)].symbol());
+            }
+            s.push('\n');
+        }
+        s
+    }
+}

crates/city/src/term.rs

@@ -0,0 +1,40 @@
+//! Raw-mode terminal setup that always restores the shell, even on panic.
+
+use anyhow::Result;
+use crossterm::{cursor, execute, terminal};
+use ratatui::Terminal;
+use ratatui::backend::CrosstermBackend;
+use std::io::{Stdout, stdout};
+
+/// Restores the terminal when dropped.
+pub struct TerminalGuard;
+
+impl TerminalGuard {
+    pub fn enter() -> Result<(Self, Terminal<CrosstermBackend<Stdout>>)> {
+        terminal::enable_raw_mode()?;
+        execute!(stdout(), terminal::EnterAlternateScreen, cursor::Hide)?;
+        let term = Terminal::new(CrosstermBackend::new(stdout()))?;
+        Ok((TerminalGuard, term))
+    }
+}
+
+impl Drop for TerminalGuard {
+    fn drop(&mut self) {
+        restore();
+    }
+}
+
+/// Leaves raw mode and the alternate screen. Safe to call more than once.
+pub fn restore() {
+    let _ = terminal::disable_raw_mode();
+    let _ = execute!(stdout(), terminal::LeaveAlternateScreen, cursor::Show);
+}
+
+/// Makes a panic restore the terminal before printing its message.
+pub fn install_panic_hook() {
+    let previous = std::panic::take_hook();
+    std::panic::set_hook(Box::new(move |info| {
+        restore();
+        previous(info);
+    }));
+}