waterui-cli 0.4.0

//! Web-frontend toolchain plumbing.
//!
//! The `[web]` manifest section, the package manager it declares, the
//! frontend build that packaging runs, and the pure planning behind
//! `water init`'s frontend decision tree.

use std::io;
use std::io::Write as _;
use std::path::{Path, PathBuf};
use std::process::Stdio;

use askama::Template;
use color_eyre::eyre::{self, Context, bail};
use serde::{Deserialize, Serialize};
use smol::process::Command;
use waterui_assets_planner::{BUNDLE_META_PREFIX, BundleMountMeta};

use crate::artifact_symbols::{ArtifactSymbols, build_host_rlib};
use crate::build::BuildProgress;
use crate::project::Project;
use crate::project_model::templates::embedded;

/// The JavaScript package manager a project declares in
/// `[web] package_manager`.
///
/// This is the single source of truth for which executable the CLI invokes:
/// a project that declares `pnpm` is never built with `bun`.
#[derive(Deserialize, Serialize, Clone, Copy, PartialEq, Eq, Debug, Default, clap::ValueEnum)]
#[serde(rename_all = "lowercase")]
pub enum PackageManager {
    /// Bun (`bun`).
    #[default]
    Bun,
    /// pnpm.
    Pnpm,
    /// npm, the Node.js default.
    Npm,
    /// Yarn.
    Yarn,
}

impl PackageManager {
    /// The executable looked up on `PATH`.
    #[must_use]
    pub const fn binary(self) -> &'static str {
        match self {
            Self::Bun => "bun",
            Self::Pnpm => "pnpm",
            Self::Npm => "npm",
            Self::Yarn => "yarn",
        }
    }

    /// `<pm> run <script>` — every supported manager accepts this form.
    #[must_use]
    pub fn run(self, script: &str) -> Command {
        let mut command = Command::new(self.binary());
        command.arg("run").arg(script);
        command
    }

    /// `<pm> install` — installs the dependencies of the current directory.
    #[must_use]
    pub fn install(self) -> Command {
        let mut command = Command::new(self.binary());
        command.arg("install");
        command
    }

    /// `<pm> create vite <dir>`; npm names its initializer `vite@latest`.
    ///
    /// `template`, when given, is forwarded to `create-vite` after a `--`
    /// separator (`--template <t>`), which every manager passes through and
    /// which skips Vite's interactive framework picker.
    #[must_use]
    pub fn create_vite(self, dir: &str, template: Option<&str>) -> Command {
        let mut command = Command::new(self.binary());
        command.arg("create");
        match self {
            Self::Npm => command.arg("vite@latest"),
            Self::Bun | Self::Pnpm | Self::Yarn => command.arg("vite"),
        };
        command.arg(dir);
        if let Some(template) = template {
            // npm needs `--` to forward args to the initializer; bun, pnpm
            // and yarn pass them through directly.
            if self == Self::Npm {
                command.arg("--");
            }
            command.args(["--template", template]);
        }
        command
    }

    /// Whether the manager's binary resolves on `PATH`.
    pub async fn is_installed(self) -> bool {
        crate::utils::which(self.binary()).await.is_ok()
    }

    /// The official installation instruction, shown when the declared manager
    /// is missing.
    #[must_use]
    pub const fn install_hint(self) -> &'static str {
        match self {
            Self::Bun => "curl -fsSL https://bun.sh/install | bash",
            Self::Pnpm => "npm install -g pnpm (or see https://pnpm.io/installation)",
            Self::Npm => "install Node.js from https://nodejs.org/",
            Self::Yarn => {
                "npm install -g yarn (or see https://yarnpkg.com/getting-started/install)"
            }
        }
    }
}

/// The `[web]` section of `Water.toml`: web-frontend toolchain declarations.
///
/// The macro never reads this — only the CLI does. Absent section and absent
/// key both mean [`PackageManager::Bun`].
#[derive(Debug, Clone, Default, Serialize, Deserialize)]
pub struct WebConfig {
    /// The package manager used for `run build`, `run dev`, `create vite`,
    /// and `install` in the frontend project.
    #[serde(default)]
    pub package_manager: PackageManager,
}

/// The `include_web!` mount declared by the project's compiled library.
///
/// Read from the `waterui_meta_bundle_*` statics in the host rlib, which is
/// ground truth for what the application actually declared.
///
/// # Errors
///
/// Returns an error when the host build fails, the rlib cannot be read, or a
/// declared mount's payload does not decode.
pub async fn web_mount(
    project: &Project,
    sccache_path: Option<&Path>,
    progress: Option<&BuildProgress>,
) -> eyre::Result<Option<BundleMountMeta>> {
    let rlib = build_host_rlib(
        project.root(),
        &project.host_target_dir().await?,
        sccache_path,
        progress,
    )
    .await?;
    let symbols = ArtifactSymbols::read(&rlib)?;
    decode_web_mount(&symbols)
}

/// Decode the `web` mount — the single mount a `project` field marks as a
/// toolchain-produced frontend — from an artifact's symbol table.
///
/// # Errors
///
/// Returns an error when a mount payload does not decode or two mounts claim
/// a frontend project.
pub fn decode_web_mount(symbols: &ArtifactSymbols) -> eyre::Result<Option<BundleMountMeta>> {
    let mut frontend = None;
    for leaf in symbols.leaves_with_prefix(BUNDLE_META_PREFIX) {
        let meta = symbols.bundle_mount_meta(&leaf)?;
        if meta.project.is_none() {
            continue;
        }
        if frontend.replace(meta).is_some() {
            bail!("more than one include_web! mount is declared in the artifact");
        }
    }
    Ok(frontend)
}

/// Build a toolchain-produced mount's frontend: `<pm> run build` inside the
/// declared project root with stdio inherited, so the user sees their own
/// bundler's output and diagnostics verbatim.
///
/// # Errors
///
/// Returns an error when the build fails or does not produce the mount's
/// declared output directory.
///
/// # Panics
///
/// Panics when `meta` declares no `project` — callers only reach this for
/// `include_web!` mounts.
pub async fn build_frontend(
    package_manager: PackageManager,
    meta: &BundleMountMeta,
) -> eyre::Result<()> {
    let root = meta
        .project
        .as_ref()
        .expect("build_frontend is only called for mounts that declare a project");
    let pm = package_manager.binary();
    let status = package_manager
        .run("build")
        .current_dir(root)
        .stdin(Stdio::inherit())
        .stdout(Stdio::inherit())
        .stderr(Stdio::inherit())
        .status()
        .await?;
    if !status.success() {
        bail!("`{pm} run build` failed in {}: {status}", root.display());
    }
    if !meta.path.is_dir() {
        bail!(
            "`{pm} run build` did not produce `{}`; set `out_dir` on `include_web!` to the bundler's output directory",
            meta.path.display()
        );
    }
    Ok(())
}

// ---------------------------------------------------------------------------
// `water run` dev server
// ---------------------------------------------------------------------------

/// The environment variable that carries the dev-server URL to a debug app.
///
/// Every launch channel reduces to this name: desktop spawns it directly,
/// `simctl launch` forwards it as `SIMCTL_CHILD_WATERUI_DEV_URL`,
/// `devicectl device process launch` carries it in the `-e` environment
/// dictionary, and Android ships it as the `waterui.env.WATERUI_DEV_URL`
/// intent extra that the generated `MainActivity` turns back into an
/// environment variable before the runtime initializes.
pub const DEV_URL_ENV: &str = "WATERUI_DEV_URL";

/// A target `water run` can hand a dev-server URL to.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum DevTarget {
    /// A desktop process the CLI spawns (macOS, GTK, Hydrolysis).
    Desktop,
    /// `simctl launch` on an iOS simulator.
    IosSimulator,
    /// `devicectl device process launch` on a physical iOS device.
    IosDevice,
    /// `am start` on an Android emulator or device.
    Android,
}

/// The URL the target should open, rewritten when the target cannot reach
/// this machine's loopback.
///
/// `WATERUI_DEV_URL` travels in the launch environment on every target —
/// `devicectl device process launch -e` carries it to a physical iOS device
/// exactly as `SIMCTL_CHILD_*` carries it to a simulator.
///
/// On a physical iOS device `localhost` is the phone itself, so the URL's
/// loopback host is replaced with the Mac's LAN address — the address the
/// device can actually route to. The dev server must be bound to a
/// non-loopback interface for this to work; [`WebDevServer::spawn`] does
/// that when its target is a physical device.
///
/// # Errors
/// Fails for [`DevTarget::IosDevice`] when no LAN-facing IPv4 address can be
/// determined — passing the phone a `localhost` URL would fail silently, so
/// this errors instead.
pub fn device_facing_url(target: DevTarget, url: &url::Url) -> eyre::Result<url::Url> {
    if target != DevTarget::IosDevice {
        return Ok(url.clone());
    }
    let mut url = url.clone();
    let host = lan_ipv4()?.to_string();
    url.set_host(Some(&host))
        .wrap_err_with(|| format!("dev-server URL cannot carry a LAN host: {url}"))?;
    Ok(url)
}

/// The IPv4 address this Mac presents on the LAN, found by asking the kernel
/// which interface would carry outbound traffic.
///
/// `UdpSocket::connect` to a public address performs no I/O — it only forces
/// a routing decision, and the resulting local address is the interface
/// address a LAN peer (the iPhone) can reach.
fn lan_ipv4() -> eyre::Result<std::net::Ipv4Addr> {
    let socket = std::net::UdpSocket::bind((std::net::Ipv4Addr::UNSPECIFIED, 0))
        .wrap_err("failed to bind a UDP socket for LAN address detection")?;
    socket
        .connect((std::net::Ipv4Addr::new(192, 0, 0, 1), 80))
        .wrap_err(
            "no outbound route — cannot determine this Mac's LAN address for the iOS device",
        )?;
    match socket.local_addr()?.ip() {
        std::net::IpAddr::V4(ip) if !ip.is_loopback() => Ok(ip),
        other => Err(eyre::eyre!(
            "the outbound interface has no usable LAN IPv4 address ({other}); connect the Mac to the same LAN as the iOS device"
        )),
    }
}

/// `adb -s <device> reverse tcp:<port> tcp:<port>` — maps the device's
/// loopback port onto the host's so the dev server is reachable from an
/// Android emulator or a USB-connected device alike.
#[must_use]
pub fn adb_reverse_args(device_id: &str, port: u16) -> Vec<String> {
    vec![
        "-s".to_string(),
        device_id.to_string(),
        "reverse".to_string(),
        format!("tcp:{port}"),
        format!("tcp:{port}"),
    ]
}

/// The port an `adb reverse` must forward, read from the `WATERUI_DEV_URL`
/// entry of a launch environment. `None` when no dev-server handoff is
/// present.
///
/// # Errors
///
/// Returns an error when the variable is set but is not a URL — a malformed
/// handoff is a bug to report, not a state to launch in.
pub fn dev_url_port<'a>(
    mut env_vars: impl Iterator<Item = (&'a str, &'a str)>,
) -> eyre::Result<Option<u16>> {
    let Some((_, value)) = env_vars.find(|(key, _)| *key == DEV_URL_ENV) else {
        return Ok(None);
    };
    let url: url::Url = value
        .parse()
        .wrap_err_with(|| format!("{DEV_URL_ENV} is set but is not a URL: {value}"))?;
    url.port_or_known_default().map_or_else(
        || Err(eyre::eyre!("{DEV_URL_ENV} has no port to forward: {value}")),
        |port| Ok(Some(port)),
    )
}

/// The script that starts the frontend's dev server: the first of `dev`,
/// `serve`, `start` declared in the project's `package.json`.
///
/// # Errors
///
/// Fails when `package.json` cannot be read or parsed, or declares none of
/// the known dev scripts.
pub fn dev_script(root: &Path) -> eyre::Result<String> {
    let package_json_path = root.join("package.json");
    let manifest = std::fs::read_to_string(&package_json_path)
        .wrap_err_with(|| format!("failed to read {}", package_json_path.display()))?;
    let package: serde_json::Value = serde_json::from_str(&manifest)
        .wrap_err_with(|| format!("failed to parse {}", package_json_path.display()))?;
    package
        .get("scripts")
        .and_then(|scripts| {
            ["dev", "serve", "start"]
                .iter()
                .find(|name| scripts.get(**name).is_some())
        })
        .map(|name| (*name).to_string())
        .ok_or_else(|| {
            eyre::eyre!(
                "`{}` declares none of the dev scripts `dev`, `serve`, `start`",
                package_json_path.display()
            )
        })
}

/// Extract the loopback URL a bundler prints once its dev server is
/// listening.
///
/// Any whitespace-separated token matching
/// `https?://(localhost|127.0.0.1|\[::1\]):<port>` counts — Vite's
/// `Local: http://localhost:5173/` is the canonical producer. The port must
/// be explicit and the host loopback; `Network:` URLs (LAN addresses) and
/// every other token on the line are ignored.
#[must_use]
pub fn dev_url_from_line(line: &str) -> Option<url::Url> {
    line.split_whitespace().find_map(|token| {
        let url = token.parse::<url::Url>().ok()?;
        if !matches!(url.scheme(), "http" | "https") {
            return None;
        }
        let loopback = url
            .host_str()
            .is_some_and(|host| host.eq_ignore_ascii_case("localhost") || host == "127.0.0.1")
            || url.host() == Some(url::Host::Ipv6(std::net::Ipv6Addr::LOCALHOST));
        (loopback && url.port().is_some()).then_some(url)
    })
}

/// A running `<pm> run <script>` process group whose printed dev-server URL
/// has been captured.
///
/// The child leads its own process tree — a process group on Unix, a job
/// object on Windows — so dropping the guard terminates the whole tree:
/// `bun run dev` re-execs `node vite`, which a lone `kill_on_drop` on the
/// direct child would orphan. `water run` holds the guard across the app's
/// lifetime, so a normal exit, an app exit, and the Ctrl-C future-drop path
/// all stop the dev server.
#[derive(Debug)]
pub struct WebDevServer {
    url: url::Url,
    child: Option<(std::process::Child, dev_server_tree::DevServerTree)>,
    _drain: smol::Task<()>,
}

impl Drop for WebDevServer {
    fn drop(&mut self) {
        let Some((mut child, tree)) = self.child.take() else {
            return;
        };
        tree.signal(true);
        std::thread::spawn(move || {
            let mut exited = false;
            for _ in 0..40 {
                std::thread::sleep(std::time::Duration::from_millis(50));
                if matches!(child.try_wait(), Ok(Some(_))) {
                    exited = true;
                    break;
                }
            }
            if !exited {
                tree.signal(false);
            }
            let _ = child.wait();
        });
    }
}

impl WebDevServer {
    /// Spawn `<pm> run <script>` inside `root` and read its stdout until the
    /// listening URL appears.
    ///
    /// stdout is piped so the URL can be parsed; every line is echoed to the
    /// terminal as it arrives and a background task keeps draining after the
    /// URL is found so the bundler never blocks on a full pipe. stderr is
    /// inherited — the bundler's diagnostics reach the user verbatim.
    ///
    /// # Errors
    ///
    /// Fails when the process cannot be spawned or its stdout ends without a
    /// loopback dev-server URL ever appearing.
    ///
    /// `expose_on_lan` appends `--host 0.0.0.0` to the dev script so the
    /// bundler listens beyond loopback — required when the target is a
    /// physical device, for which `localhost` is the device itself.
    ///
    /// # Panics
    ///
    /// Panics if the spawned child has no piped stdout — impossible, since
    /// the spawn configures it above.
    pub async fn spawn(
        package_manager: PackageManager,
        root: &Path,
        script: &str,
        expose_on_lan: bool,
    ) -> eyre::Result<Self> {
        use smol::io::{AsyncBufReadExt, BufReader};
        use smol::stream::StreamExt as _;

        let pm = package_manager.binary();
        // `std::process::Command`, not `smol`'s: the child must lead its own
        // process group so the guard's drop can signal the whole tree.
        let mut command = std::process::Command::new(pm);
        command.arg("run").arg(script).current_dir(root);
        if expose_on_lan {
            // npm needs `--` to forward args to the script; bun, pnpm and
            // yarn pass them through directly — the same convention
            // `PackageManager::create_vite` follows.
            if package_manager == PackageManager::Npm {
                command.arg("--");
            }
            command.args(["--host", "0.0.0.0"]);
        }
        command
            .stdin(Stdio::null())
            .stdout(Stdio::piped())
            .stderr(Stdio::inherit());
        #[cfg(unix)]
        {
            use std::os::unix::process::CommandExt as _;
            command.process_group(0);
        }
        let mut child = command.spawn().wrap_err_with(|| {
            format!("failed to spawn `{pm} run {script}` in {}", root.display())
        })?;
        let tree = dev_server_tree::DevServerTree::adopt(&child)
            .wrap_err_with(|| format!("failed to group the `{pm} run {script}` process tree"))?;
        let stdout = child.stdout.take().expect("stdout is piped");
        let mut lines = BufReader::new(smol::Unblock::new(stdout)).lines();

        let url = loop {
            match lines.next().await {
                Some(Ok(line)) => {
                    echo_dev_server_line(&line);
                    if let Some(url) = dev_url_from_line(&line) {
                        break url;
                    }
                }
                Some(Err(error)) => {
                    tree.signal(false);
                    let _ = smol::unblock(move || child.wait()).await;
                    bail!("failed to read `{pm} run {script}` output: {error}");
                }
                None => {
                    let status = child.try_wait().ok().flatten();
                    tree.signal(false);
                    let _ = smol::unblock(move || child.wait()).await;
                    match status {
                        Some(status) => bail!(
                            "`{pm} run {script}` exited with {status} without printing a dev-server URL"
                        ),
                        None => bail!(
                            "`{pm} run {script}` closed its output without printing a dev-server URL"
                        ),
                    }
                }
            }
        };

        let drain = smol::spawn(async move {
            while let Some(line) = lines.next().await {
                match line {
                    Ok(line) => echo_dev_server_line(&line),
                    Err(_) => break,
                }
            }
        });

        Ok(Self {
            url,
            child: Some((child, tree)),
            _drain: drain,
        })
    }

    /// The dev-server URL the app should open.
    #[must_use]
    pub const fn url(&self) -> &url::Url {
        &self.url
    }
}

/// The handle on the dev server's whole process tree, whichever the platform
/// offers: the process group the child was spawned to lead on Unix, a job
/// object the child is assigned to on Windows.
mod dev_server_tree {
    use std::io;

    /// The dev server and every process it re-execs, addressable as one.
    #[cfg(unix)]
    #[derive(Debug)]
    pub struct DevServerTree {
        group: nix::unistd::Pid,
    }

    #[cfg(unix)]
    impl DevServerTree {
        /// The process group `child` leads. It was spawned with
        /// `process_group(0)`; a child that did not end up leading its own
        /// group is refused rather than signalled, because a group signal
        /// would then reach whatever group it shares — `water` included.
        pub fn adopt(child: &std::process::Child) -> io::Result<Self> {
            let pid = nix::unistd::Pid::from_raw(
                i32::try_from(child.id()).expect("process identifiers fit in i32"),
            );
            let group = nix::unistd::getpgid(Some(pid))?;
            if group != pid {
                return Err(io::Error::other(format!(
                    "process {pid} belongs to group {group} instead of leading its own"
                )));
            }
            Ok(Self { group })
        }

        /// Signal every process in the group: SIGTERM when `graceful`, else
        /// SIGKILL.
        pub fn signal(&self, graceful: bool) {
            let signal = if graceful {
                nix::sys::signal::Signal::SIGTERM
            } else {
                nix::sys::signal::Signal::SIGKILL
            };
            let _ = nix::sys::signal::killpg(self.group, signal);
        }
    }

    /// The dev server and every process it re-execs, addressable as one: a
    /// job object that kills its members when the last handle closes, so the
    /// tree cannot outlive `water` even when it exits without dropping the
    /// guard.
    #[cfg(windows)]
    #[derive(Debug)]
    pub struct DevServerTree {
        job: windows_sys::Win32::Foundation::HANDLE,
    }

    // SAFETY: a job handle is a process-wide kernel object with no thread
    // affinity; the guard's drop hands it to a waiting thread.
    #[cfg(windows)]
    unsafe impl Send for DevServerTree {}

    #[cfg(windows)]
    impl DevServerTree {
        /// A new job that kills its members on close, with `child` assigned to
        /// it — the processes `child` spawns from now on join automatically.
        pub fn adopt(child: &std::process::Child) -> io::Result<Self> {
            use std::os::windows::io::AsRawHandle as _;

            use windows_sys::Win32::System::JobObjects::{
                AssignProcessToJobObject, CreateJobObjectW, JOB_OBJECT_LIMIT_KILL_ON_JOB_CLOSE,
                JOBOBJECT_EXTENDED_LIMIT_INFORMATION, JobObjectExtendedLimitInformation,
                SetInformationJobObject,
            };

            // SAFETY: an unnamed job with default security; the null pointers
            // are the documented arguments for that.
            let job = unsafe { CreateJobObjectW(std::ptr::null(), std::ptr::null()) };
            if job.is_null() {
                return Err(io::Error::last_os_error());
            }
            let tree = Self { job };
            // SAFETY: an all-zero limit block is the documented starting
            // point; only the kill-on-close flag is set below.
            let mut limits: JOBOBJECT_EXTENDED_LIMIT_INFORMATION = unsafe { std::mem::zeroed() };
            limits.BasicLimitInformation.LimitFlags = JOB_OBJECT_LIMIT_KILL_ON_JOB_CLOSE;
            let size = u32::try_from(std::mem::size_of::<JOBOBJECT_EXTENDED_LIMIT_INFORMATION>())
                .expect("the limit block is far smaller than u32::MAX bytes");
            // SAFETY: `job` is the live handle created above and `limits` is
            // a fully initialised block of the size passed.
            let configured = unsafe {
                SetInformationJobObject(
                    job,
                    JobObjectExtendedLimitInformation,
                    (&raw const limits).cast(),
                    size,
                )
            };
            if configured == 0 {
                return Err(io::Error::last_os_error());
            }
            // SAFETY: both handles are live; the child's comes from the
            // standard library's `Child` and stays open while `child` is.
            let assigned = unsafe { AssignProcessToJobObject(job, child.as_raw_handle().cast()) };
            if assigned == 0 {
                return Err(io::Error::last_os_error());
            }
            Ok(tree)
        }

        /// Terminate every process in the job. Windows has no graceful
        /// signal a console process observes, so `graceful` selects nothing
        /// here; the guard's drop escalates to this call after its grace
        /// period regardless.
        pub fn signal(&self, graceful: bool) {
            use windows_sys::Win32::System::JobObjects::TerminateJobObject;

            if graceful {
                return;
            }
            // SAFETY: `self.job` is a live job handle owned by this value.
            let _ = unsafe { TerminateJobObject(self.job, 1) };
        }
    }

    #[cfg(windows)]
    impl Drop for DevServerTree {
        fn drop(&mut self) {
            use windows_sys::Win32::Foundation::CloseHandle;

            // SAFETY: the handle was created by `adopt` and is closed exactly
            // once, here; closing the last handle kills the job's members.
            let _ = unsafe { CloseHandle(self.job) };
        }
    }
}

/// Echo one line of dev-server output on the CLI's terminal channel — the
/// same stderr stream the shell's human output uses.
fn echo_dev_server_line(line: &str) {
    let _ = writeln!(anstream::stderr().lock(), "{line}");
}

// ---------------------------------------------------------------------------
// `water init` planning
// ---------------------------------------------------------------------------

/// Where the frontend of an initialized project comes from.
#[derive(Debug, Clone, PartialEq, Eq)]
pub enum WebSource {
    /// Scaffold a new Vite project into `web/`.
    New,
    /// An existing frontend project at this path.
    Existing(PathBuf),
}

/// What to do with a frontend found outside `web/`.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum ExistingFrontendMode {
    /// Copy it into `web/` (excluding `node_modules` and `.git`), then install.
    Copy,
    /// Leave it in place; `include_web!` references it by relative path.
    Reference,
}

/// The answers `water init` needs, each supplied by a flag or a prompt.
#[derive(Debug, Clone, Default)]
pub struct InitAnswers {
    /// `--web new|<path>`: the frontend source, if the flag settled it.
    pub web: Option<WebSource>,
    /// `--web-mode copy|reference`: how an existing frontend joins, if the
    /// flag settled it.
    pub web_mode: Option<ExistingFrontendMode>,
    /// `--package-manager`: the declared manager, if the flag settled it.
    pub package_manager: Option<PackageManager>,
}

/// One step of `water init`. The command executes these in order; the plan is
/// pure so the decision tree is testable without touching disk.
#[derive(Debug, Clone, PartialEq, Eq)]
pub enum InitAction {
    /// Move the listed top-level entries into `web/`.
    MoveFrontendToWeb {
        /// Top-level entries of the project root to move.
        entries: Vec<PathBuf>,
    },
    /// `<pm> create vite web` inside the project root.
    ScaffoldVite,
    /// Copy an existing project into `web/` (skipping `node_modules` and
    /// `.git`), then install its dependencies.
    CopyFrontend {
        /// The project to copy.
        source: PathBuf,
    },
    /// `<pm> install` inside `web/`.
    InstallDependencies,
    /// Scaffold the Rust shell whose root view is `include_web!(<arg>)`.
    ScaffoldShell {
        /// The `include_web!` argument — `"web"` or a relative path.
        web_arg: String,
    },
}

/// Top-level entries that never move into `web/` when a CWD frontend is
/// relocated: the Rust shell and project metadata stay at the root.
fn root_only_entries(has_rust_manifest: bool, entry: &str) -> bool {
    if matches!(
        entry,
        ".git" | ".github" | ".water" | "Water.toml" | "Water.lock" | "backends" | "target" | "web"
    ) || entry.starts_with("README")
        || entry.starts_with("LICENSE")
    {
        return true;
    }
    // `src/` and the Cargo files are the frontend's own when no Rust manifest
    // exists yet; once Cargo.toml is present they belong to the shell.
    has_rust_manifest && matches!(entry, "Cargo.toml" | "Cargo.lock" | "src")
}

/// The package manager a lockfile implies, used as the prompt's initial value.
#[must_use]
pub fn lockfile_package_manager(entries: &[String]) -> Option<PackageManager> {
    if entries.iter().any(|e| e == "bun.lock" || e == "bun.lockb") {
        Some(PackageManager::Bun)
    } else if entries.iter().any(|e| e == "pnpm-lock.yaml") {
        Some(PackageManager::Pnpm)
    } else if entries.iter().any(|e| e == "yarn.lock") {
        Some(PackageManager::Yarn)
    } else if entries.iter().any(|e| e == "package-lock.json") {
        Some(PackageManager::Npm)
    } else {
        None
    }
}

/// The ordered steps `water init` performs, decided from the CWD's top-level
/// listing and the already-resolved answers.
///
/// The caller resolves prompts first: every field of `answers` that is still
/// `None` is a prompt it must ask (with [`lockfile_package_manager`] as the
/// package-manager default) before planning.
///
/// # Errors
///
/// Returns an error when a referenced frontend path escapes the project root
/// in a way `include_web!` cannot express, or the answers are inconsistent
/// (`--web new` combined with `--web-mode`).
pub fn plan_init(
    project_root: &Path,
    entries: &[String],
    answers: &InitAnswers,
) -> eyre::Result<Vec<InitAction>> {
    if entries.iter().any(|e| e == "package.json") {
        let has_rust_manifest = entries.iter().any(|e| e == "Cargo.toml");
        let move_entries = entries
            .iter()
            .filter(|entry| !root_only_entries(has_rust_manifest, entry))
            .map(PathBuf::from)
            .collect();
        return Ok(vec![
            InitAction::MoveFrontendToWeb {
                entries: move_entries,
            },
            InitAction::ScaffoldShell {
                web_arg: "web".to_string(),
            },
        ]);
    }

    match answers.web.clone() {
        Some(WebSource::New) | None => Ok(vec![
            InitAction::ScaffoldVite,
            InitAction::InstallDependencies,
            InitAction::ScaffoldShell {
                web_arg: "web".to_string(),
            },
        ]),
        Some(WebSource::Existing(source)) => {
            match answers.web_mode.unwrap_or(ExistingFrontendMode::Copy) {
                ExistingFrontendMode::Copy => Ok(vec![
                    InitAction::CopyFrontend { source },
                    InitAction::InstallDependencies,
                    InitAction::ScaffoldShell {
                        web_arg: "web".to_string(),
                    },
                ]),
                ExistingFrontendMode::Reference => {
                    let arg = relative_path_arg(project_root, &source)?;
                    Ok(vec![InitAction::ScaffoldShell { web_arg: arg }])
                }
            }
        }
    }
}

/// The `include_web!` argument for a frontend outside `web/`: a relative path
/// from the project root, with `..` segments for directories outside it.
fn relative_path_arg(project_root: &Path, source: &Path) -> eyre::Result<String> {
    let root = dunce::canonicalize(project_root)?;
    let source = dunce::canonicalize(source)?;
    let mut root_components = root.components().peekable();
    let mut source_components = source.components().peekable();
    while root_components.peek() == source_components.peek() && root_components.peek().is_some() {
        root_components.next();
        source_components.next();
    }
    let mut arg = String::new();
    for _ in root_components {
        if !arg.is_empty() {
            arg.push('/');
        }
        arg.push_str("..");
    }
    for component in source_components {
        if !arg.is_empty() {
            arg.push('/');
        }
        arg.push_str(
            component
                .as_os_str()
                .to_str()
                .ok_or_else(|| eyre::eyre!("frontend path is not valid UTF-8"))?,
        );
    }
    if arg.is_empty() {
        bail!("the frontend is the project root itself; put its files in `web/`");
    }
    Ok(arg)
}

// ---------------------------------------------------------------------------
// Branded starter overlay
// ---------------------------------------------------------------------------

/// The framework a freshly scaffolded Vite project declares.
///
/// Read from `web/package.json` dependencies — the dependencies the template
/// ships are the one ground truth `create vite` gives us.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum WebFramework {
    /// `vanilla`/`vanilla-ts`: no framework dependency.
    Vanilla,
    /// `react` in the dependencies.
    React,
    /// `preact` in the dependencies.
    Preact,
    /// `vue` in the dependencies.
    Vue,
    /// `svelte` — a devDependency in Vite's starter.
    Svelte,
    /// `solid-js` in the dependencies.
    Solid,
    /// `lit` in the dependencies.
    Lit,
    /// Dependencies declare something we do not know — e.g. Qwik.
    Other,
}

impl WebFramework {
    /// The name the branded page prints.
    #[must_use]
    pub const fn display_name(self) -> &'static str {
        match self {
            Self::Vanilla => "Vanilla",
            Self::React => "React",
            Self::Preact => "Preact",
            Self::Vue => "Vue",
            Self::Svelte => "Svelte",
            Self::Solid => "Solid",
            Self::Lit => "Lit",
            Self::Other => "web",
        }
    }

    /// Whether the overlay knows how to replace the starter's page.
    const fn supports_branding(self) -> bool {
        matches!(self, Self::Vanilla | Self::React | Self::Vue | Self::Svelte)
    }
}

/// What `web/package.json` says about a scaffolded frontend: the framework
/// dependency and whether `typescript` is a devDependency.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub struct WebFrontend {
    /// The framework the starter's dependencies declare.
    pub framework: WebFramework,
    /// Whether `typescript` is a devDependency (else JavaScript).
    pub typescript: bool,
}

/// The dependency names that identify each framework, checked in order.
const FRAMEWORK_DEPENDENCIES: &[(&str, WebFramework)] = &[
    ("react", WebFramework::React),
    ("preact", WebFramework::Preact),
    ("vue", WebFramework::Vue),
    ("svelte", WebFramework::Svelte),
    ("solid-js", WebFramework::Solid),
    ("lit", WebFramework::Lit),
];

/// Read the framework and language of a scaffolded frontend from its
/// `package.json` text. `None` when the manifest cannot be parsed.
///
/// Framework markers are looked up in both `dependencies` and
/// `devDependencies` — Vite's Svelte starter compiles the framework away and
/// declares it as a devDependency. `typescript` counts only in
/// `devDependencies`. A manifest with no `dependencies` at all is Vanilla;
/// one whose dependencies name none of the known frameworks is
/// [`WebFramework::Other`].
#[must_use]
pub fn detect_web_frontend(package_json: &str) -> Option<WebFrontend> {
    let package: serde_json::Value = serde_json::from_str(package_json).ok()?;
    let dependencies = package
        .get("dependencies")
        .and_then(serde_json::Value::as_object);
    let dev_dependencies = package
        .get("devDependencies")
        .and_then(serde_json::Value::as_object);
    let has_marker = |name: &str| {
        dependencies.is_some_and(|deps| deps.contains_key(name))
            || dev_dependencies.is_some_and(|deps| deps.contains_key(name))
    };
    let framework = FRAMEWORK_DEPENDENCIES
        .iter()
        .find(|(name, _)| has_marker(name))
        .map_or_else(
            || {
                if dependencies.is_none_or(serde_json::Map::is_empty) {
                    WebFramework::Vanilla
                } else {
                    WebFramework::Other
                }
            },
            |(_, framework)| *framework,
        );
    let typescript = dev_dependencies.is_some_and(|deps| deps.contains_key("typescript"));
    Some(WebFrontend {
        framework,
        typescript,
    })
}

/// What [`apply_brand_overlay`] did, and what it could not.
#[derive(Debug, Default)]
pub struct WebOverlayReport {
    /// The detected frontend (`None` when `package.json` did not parse).
    pub frontend: Option<WebFrontend>,
    /// Whether the starter's visible page was replaced with the branded one —
    /// `false` means the framework's own starter page remains.
    pub branded: bool,
    /// Non-fatal misses: expected files the layout did not ship.
    pub warnings: Vec<String>,
}

/// Values the branded starter templates interpolate.
struct WebOverlayContext<'a> {
    /// The name the heading prints — "React", or "TypeScript" for a vanilla
    /// starter.
    framework: &'a str,
    /// The file the "edit and save" line names — "src/App.tsx".
    entry: &'a str,
    /// The import specifier the framework logo resolves to — the starter's
    /// own logo file, e.g. `./assets/typescript.svg`.
    logo: &'a str,
    /// Whether the project is TypeScript; selects `lang="ts"` in SFCs and the
    /// typed bridge signature.
    typescript: bool,
}

macro_rules! web_overlay_templates {
    ($($name:ident => $path:literal),* $(,)?) => {$(
        #[derive(Template)]
        #[template(path = $path, escape = "none")]
        struct $name<'a> {
            ctx: &'a WebOverlayContext<'a>,
        }
    )*};
}

web_overlay_templates! {
    VanillaMainTsTemplate => "src/templates/web/vanilla/main.ts.tpl",
    VanillaMainJsTemplate => "src/templates/web/vanilla/main.js.tpl",
    ReactAppTsxTemplate => "src/templates/web/react/App.tsx.tpl",
    ReactAppJsxTemplate => "src/templates/web/react/App.jsx.tpl",
    VueAppTemplate => "src/templates/web/vue/App.vue.tpl",
    SvelteAppTemplate => "src/templates/web/svelte/App.svelte.tpl",
}

/// One entry-file template the overlay can render.
#[derive(Clone, Copy)]
enum OverlayTemplate {
    VanillaTs,
    VanillaJs,
    ReactTsx,
    ReactJsx,
    Vue,
    Svelte,
}

impl OverlayTemplate {
    fn render(self, ctx: &WebOverlayContext) -> io::Result<String> {
        let rendered = match self {
            Self::VanillaTs => VanillaMainTsTemplate { ctx }.render(),
            Self::VanillaJs => VanillaMainJsTemplate { ctx }.render(),
            Self::ReactTsx => ReactAppTsxTemplate { ctx }.render(),
            Self::ReactJsx => ReactAppJsxTemplate { ctx }.render(),
            Self::Vue => VueAppTemplate { ctx }.render(),
            Self::Svelte => SvelteAppTemplate { ctx }.render(),
        };
        rendered.map_err(|error| {
            io::Error::other(format!("web overlay template render failed: {error}"))
        })
    }
}

/// A destination the overlay may fill with a rendered entry file, probed in
/// order — `src/main.ts` first, `src/main.js` when the project is JavaScript.
struct EntryCandidate {
    /// The destination path inside `web/`; also the path the page's "edit and
    /// save" line names.
    dest: &'static str,
    /// The template that renders the file.
    template: OverlayTemplate,
    /// Candidate paths of the framework logo the branded page shows beside
    /// the `WaterUI` mark — the starter moved it between Vite versions.
    logos: &'static [&'static str],
}

/// The branded-overlay layout of one supported framework.
struct OverlaySpec {
    /// Entry-file candidates in probe order.
    entries: &'static [EntryCandidate],
    /// Stylesheets that receive the branded stylesheet verbatim.
    styles: &'static [&'static str],
    /// The starter's second, global stylesheet receiving the small baseline
    /// (React's `index.css`; every other supported framework has only the one
    /// branded stylesheet).
    base_style: Option<&'static str>,
    /// Starter files the overlay removes, grouped so several candidates count
    /// as one expected file; a group matching nothing warns.
    deletions: &'static [&'static [&'static str]],
}

const fn overlay_spec(framework: WebFramework) -> Option<OverlaySpec> {
    Some(match framework {
        WebFramework::Vanilla => OverlaySpec {
            entries: &[
                EntryCandidate {
                    dest: "src/main.ts",
                    template: OverlayTemplate::VanillaTs,
                    logos: &["src/assets/typescript.svg", "src/typescript.svg"],
                },
                EntryCandidate {
                    dest: "src/main.js",
                    template: OverlayTemplate::VanillaJs,
                    logos: &["src/assets/javascript.svg", "src/javascript.svg"],
                },
            ],
            styles: &["src/style.css"],
            base_style: None,
            deletions: &[&["src/counter.ts", "src/counter.js"]],
        },
        WebFramework::React => OverlaySpec {
            entries: &[
                EntryCandidate {
                    dest: "src/App.tsx",
                    template: OverlayTemplate::ReactTsx,
                    logos: &["src/assets/react.svg", "src/react.svg"],
                },
                EntryCandidate {
                    dest: "src/App.jsx",
                    template: OverlayTemplate::ReactJsx,
                    logos: &["src/assets/react.svg", "src/react.svg"],
                },
            ],
            styles: &["src/App.css"],
            base_style: Some("src/index.css"),
            deletions: &[],
        },
        WebFramework::Vue => OverlaySpec {
            entries: &[EntryCandidate {
                dest: "src/App.vue",
                template: OverlayTemplate::Vue,
                logos: &["src/assets/vue.svg", "src/vue.svg"],
            }],
            styles: &["src/style.css"],
            base_style: None,
            deletions: &[&["src/components/HelloWorld.vue"]],
        },
        WebFramework::Svelte => OverlaySpec {
            entries: &[EntryCandidate {
                dest: "src/App.svelte",
                template: OverlayTemplate::Svelte,
                logos: &["src/assets/svelte.svg", "src/svelte.svg"],
            }],
            styles: &["src/app.css"],
            base_style: None,
            deletions: &[&["src/lib/Counter.svelte"]],
        },
        _ => return None,
    })
}

/// A verbatim asset the embedded `web/` template dir ships.
fn web_template_asset(relative: &str) -> &'static [u8] {
    embedded::ROOT
        .get_file(format!("web/{relative}"))
        .unwrap_or_else(|| panic!("web overlay asset `{relative}` must ship in the CLI"))
        .contents()
}

/// Apply the WaterUI-branded overlay to a freshly `create vite`-scaffolded
/// frontend in `web_dir`.
///
/// Every project — branded or not — gets `public/waterui.svg`, loses
/// `public/vite.svg`, and has its `index.html` retitled to `display_name`
/// with its favicon repointed to the `WaterUI` mark. The supported matrix
/// (Vanilla, React, Vue, Svelte — TypeScript or JavaScript) additionally gets
/// its starter page replaced; anything else keeps the framework's default
/// page and reports `branded: false`. Files an unexpected layout does not
/// ship are skipped with a warning, never an error.
///
/// # Errors
///
/// Returns an error only on real I/O failures writing the overlay.
///
/// # Panics
///
/// Panics when the embedded `web/` template assets are missing — they are
/// compiled into the CLI.
pub fn apply_brand_overlay(web_dir: &Path, display_name: &str) -> io::Result<WebOverlayReport> {
    let mut report = WebOverlayReport::default();

    let logo = embedded::ROOT
        .get_file("icon.svg")
        .expect("the WaterUI logo ships in the template bundle");
    write_overlay_file(web_dir, "public/waterui.svg", logo.contents())?;
    // `index.html` is repointed at `/waterui.svg` below, so the starter's own
    // favicons are orphaned — Vite 7 ships `vite.svg`, Vite 8 `favicon.svg`.
    for orphaned in ["public/vite.svg", "public/favicon.svg"] {
        let path = web_dir.join(orphaned);
        if path.exists() {
            std::fs::remove_file(&path)?;
        }
    }
    retitle_index_html(web_dir, display_name, &mut report.warnings)?;

    let Some(frontend) = read_frontend(web_dir, &mut report.warnings) else {
        return Ok(report);
    };
    report.frontend = Some(frontend);
    if frontend.framework.supports_branding() {
        report.branded = brand_framework_page(web_dir, frontend, &mut report.warnings)?;
    }
    Ok(report)
}

/// Write `contents` to `web_dir/relative`, creating parent directories.
fn write_overlay_file(web_dir: &Path, relative: &str, contents: &[u8]) -> io::Result<()> {
    let dest = web_dir.join(relative);
    if let Some(parent) = dest.parent() {
        std::fs::create_dir_all(parent)?;
    }
    std::fs::write(dest, contents)
}

/// Read the scaffolded frontend's framework and language; an unreadable or
/// unparsable `package.json` warns and yields `None`.
fn read_frontend(web_dir: &Path, warnings: &mut Vec<String>) -> Option<WebFrontend> {
    if let Ok(manifest) = std::fs::read_to_string(web_dir.join("package.json")) {
        detect_web_frontend(&manifest).or_else(|| {
            warnings.push(
                "web/package.json did not parse — the starter page was left in place".to_string(),
            );
            None
        })
    } else {
        warnings
            .push("web/package.json is missing — the starter page was left in place".to_string());
        None
    }
}

/// Replace the starter's visible page with the branded one. Returns `false`
/// when the layout is not recognized — the framework's page then stays.
fn brand_framework_page(
    web_dir: &Path,
    frontend: WebFrontend,
    warnings: &mut Vec<String>,
) -> io::Result<bool> {
    let Some(spec) = overlay_spec(frontend.framework) else {
        return Ok(false);
    };
    let Some(entry) = spec
        .entries
        .iter()
        .find(|candidate| web_dir.join(candidate.dest).is_file())
    else {
        warnings.push(format!(
            "{} is missing — the {} starter layout is not recognized; its default page remains",
            spec.entries[0].dest,
            frontend.framework.display_name(),
        ));
        return Ok(false);
    };

    // The heading pairs WaterUI with what the starter actually showcases —
    // the framework logo it ships. A vanilla starter's mark is the language
    // logo, so "TypeScript" reads truer than "Vanilla".
    let framework = if frontend.framework == WebFramework::Vanilla {
        if frontend.typescript {
            "TypeScript"
        } else {
            "JavaScript"
        }
    } else {
        frontend.framework.display_name()
    };
    // Every entry file lives in `src/`; the logo specifier is relative to it.
    // When the starter ships no logo the import points at the WaterUI mark we
    // just wrote to `public/` — an import the bundler still resolves.
    let logo = entry
        .logos
        .iter()
        .find(|logo| web_dir.join(logo).is_file())
        .map_or_else(
            || {
                warnings.push(format!(
                    "{} is missing — the branded page falls back to the WaterUI mark",
                    entry.logos[0]
                ));
                "../public/waterui.svg".to_string()
            },
            |logo| format!("./{}", logo.strip_prefix("src/").unwrap_or(logo)),
        );

    let ctx = WebOverlayContext {
        framework,
        entry: entry.dest,
        logo: &logo,
        typescript: frontend.typescript,
    };
    write_overlay_file(web_dir, entry.dest, entry.template.render(&ctx)?.as_bytes())?;

    for style in spec.styles {
        if web_dir.join(style).is_file() {
            write_overlay_file(web_dir, style, web_template_asset("brand.css"))?;
        } else {
            warnings.push(format!("{style} is missing — branded stylesheet skipped"));
        }
    }
    if let Some(base_style) = spec.base_style {
        if web_dir.join(base_style).is_file() {
            write_overlay_file(web_dir, base_style, web_template_asset("base.css"))?;
        } else {
            warnings.push(format!(
                "{base_style} is missing — baseline stylesheet skipped"
            ));
        }
    }
    for group in spec.deletions {
        let mut removed = false;
        for file in *group {
            let path = web_dir.join(file);
            if path.is_file() {
                std::fs::remove_file(path)?;
                removed = true;
            }
        }
        if !removed {
            warnings.push(format!("{} is missing — nothing to remove", group[0]));
        }
    }
    // The branded page references nothing else the starter put in `public/`;
    // `icons.svg` is its sprite sheet.
    let sprite = web_dir.join("public/icons.svg");
    if sprite.exists() {
        std::fs::remove_file(&sprite)?;
    }
    if frontend.typescript {
        write_overlay_file(
            web_dir,
            "src/waterui.d.ts",
            web_template_asset("waterui.d.ts"),
        )?;
    }
    Ok(true)
}

/// Retitle `index.html` to the app's display name and repoint its favicon to
/// `/waterui.svg`. The file is patched rather than replaced, so markup a
/// starter puts there survives.
fn retitle_index_html(
    web_dir: &Path,
    display_name: &str,
    warnings: &mut Vec<String>,
) -> io::Result<()> {
    let path = web_dir.join("index.html");
    if !path.is_file() {
        warnings.push("index.html is missing — title and favicon unchanged".to_string());
        return Ok(());
    }
    let mut html = std::fs::read_to_string(&path)?;
    match (html.find("<title>"), html.find("</title>")) {
        (Some(start), Some(end)) if start + "<title>".len() <= end => {
            html.replace_range(
                start + "<title>".len()..end,
                &escape_html_text(display_name),
            );
        }
        _ => warnings.push("index.html has no <title> to retitle".to_string()),
    }
    // Repoint whichever favicon the starter links — `/vite.svg` on Vite 7,
    // `/favicon.svg` on Vite 8 — at the WaterUI mark.
    let mut repointed = false;
    for favicon in ["/favicon.svg", "./favicon.svg", "/vite.svg", "./vite.svg"] {
        let quoted = format!("\"{favicon}\"");
        if html.contains(&quoted) {
            html = html.replace(&quoted, "\"/waterui.svg\"");
            repointed = true;
        }
    }
    if !repointed {
        if let Some(head_end) = html.find("</head>") {
            html.insert_str(
                head_end,
                "    <link rel=\"icon\" type=\"image/svg+xml\" href=\"/waterui.svg\" />\n  ",
            );
        } else {
            warnings.push("index.html has no favicon link or </head> to repoint".to_string());
        }
    }
    std::fs::write(&path, html)
}

/// Escape the handful of characters that break a `<title>` text node.
fn escape_html_text(text: &str) -> String {
    text.replace('&', "&amp;")
        .replace('<', "&lt;")
        .replace('>', "&gt;")
}

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

    fn entries(names: &[&str]) -> Vec<String> {
        names.iter().map(ToString::to_string).collect()
    }

    #[test]
    fn package_manager_serde_round_trip() {
        // toml's serializer needs a table at the root; round-trip through the
        // `[web]` section shape the manifest actually uses.
        #[derive(Debug, Serialize, Deserialize)]
        struct Section {
            package_manager: PackageManager,
        }
        for (pm, name) in [
            (PackageManager::Bun, "bun"),
            (PackageManager::Pnpm, "pnpm"),
            (PackageManager::Npm, "npm"),
            (PackageManager::Yarn, "yarn"),
        ] {
            let encoded = toml::to_string(&Section {
                package_manager: pm,
            })
            .unwrap();
            assert_eq!(encoded.trim(), format!("package_manager = \"{name}\""));
            assert_eq!(
                toml::from_str::<Section>(&encoded).unwrap().package_manager,
                pm
            );
        }
        let error = toml::from_str::<Section>("package_manager = \"deno\"").unwrap_err();
        let message = error.to_string();
        for option in ["bun", "pnpm", "npm", "yarn"] {
            assert!(
                message.contains(option),
                "unknown manager error names the options: {message}"
            );
        }
    }

    #[test]
    fn command_arg_vectors() {
        let args = |command: &Command| -> Vec<String> {
            std::iter::once(command.get_program().to_string_lossy().into_owned())
                .chain(
                    command
                        .get_args()
                        .map(|arg| arg.to_string_lossy().into_owned()),
                )
                .collect()
        };
        assert_eq!(
            args(&PackageManager::Bun.run("build")),
            ["bun", "run", "build"]
        );
        assert_eq!(args(&PackageManager::Pnpm.install()), ["pnpm", "install"]);
        assert_eq!(
            args(&PackageManager::Yarn.create_vite("web", None)),
            ["yarn", "create", "vite", "web"]
        );
        assert_eq!(
            args(&PackageManager::Bun.create_vite("web", Some("react-ts"))),
            ["bun", "create", "vite", "web", "--template", "react-ts"]
        );
        assert_eq!(
            args(&PackageManager::Npm.create_vite("web", Some("vanilla-ts"))),
            [
                "npm",
                "create",
                "vite@latest",
                "web",
                "--",
                "--template",
                "vanilla-ts"
            ]
        );
    }

    #[test]
    fn cwd_frontend_moves_into_web_keeping_shell_files() {
        let plan = plan_init(
            Path::new("/project"),
            &entries(&[
                "package.json",
                "bun.lock",
                "index.html",
                "src",
                "Cargo.toml",
                "target",
                ".git",
                ".github",
                "README.md",
                "Water.toml",
            ]),
            &InitAnswers::default(),
        )
        .unwrap();
        let InitAction::MoveFrontendToWeb { entries: moved } = &plan[0] else {
            panic!("expected the move step first: {plan:?}")
        };
        let mut moved: Vec<String> = moved
            .iter()
            .map(|p| p.to_string_lossy().into_owned())
            .collect();
        moved.sort();
        // `Cargo.toml` and `src/` stay at the root: they are the shell's.
        assert_eq!(moved, ["bun.lock", "index.html", "package.json"]);
        assert_eq!(
            plan[1],
            InitAction::ScaffoldShell {
                web_arg: "web".to_string()
            }
        );
    }

    #[test]
    fn pure_frontend_cwd_moves_its_src() {
        let plan = plan_init(
            Path::new("/project"),
            &entries(&["package.json", "src", "vite.config.ts"]),
            &InitAnswers::default(),
        )
        .unwrap();
        let InitAction::MoveFrontendToWeb { entries: moved } = &plan[0] else {
            panic!("expected the move step first: {plan:?}")
        };
        assert!(
            moved.contains(&PathBuf::from("src")),
            "without Cargo.toml, src/ is frontend code: {moved:?}"
        );
    }

    #[test]
    fn new_frontend_scaffolds_vite_then_installs() {
        let answers = InitAnswers {
            web: Some(WebSource::New),
            ..InitAnswers::default()
        };
        let plan = plan_init(Path::new("/project"), &entries(&[]), &answers).unwrap();
        assert_eq!(
            plan,
            [
                InitAction::ScaffoldVite,
                InitAction::InstallDependencies,
                InitAction::ScaffoldShell {
                    web_arg: "web".to_string()
                },
            ]
        );
    }

    #[test]
    fn existing_frontend_copy_installs_into_web() {
        let answers = InitAnswers {
            web: Some(WebSource::Existing(PathBuf::from("/elsewhere/app"))),
            web_mode: Some(ExistingFrontendMode::Copy),
            ..InitAnswers::default()
        };
        let plan = plan_init(Path::new("/project"), &entries(&[]), &answers).unwrap();
        assert_eq!(
            plan,
            [
                InitAction::CopyFrontend {
                    source: PathBuf::from("/elsewhere/app")
                },
                InitAction::InstallDependencies,
                InitAction::ScaffoldShell {
                    web_arg: "web".to_string()
                },
            ]
        );
    }

    #[test]
    fn existing_frontend_reference_uses_a_relative_arg() {
        let temp = tempfile::tempdir().unwrap();
        let root = temp.path().join("project");
        let sibling = temp.path().join("frontend");
        std::fs::create_dir_all(&root).unwrap();
        std::fs::create_dir_all(&sibling).unwrap();
        let answers = InitAnswers {
            web: Some(WebSource::Existing(sibling)),
            web_mode: Some(ExistingFrontendMode::Reference),
            ..InitAnswers::default()
        };
        let plan = plan_init(&root, &entries(&[]), &answers).unwrap();
        assert_eq!(
            plan,
            [InitAction::ScaffoldShell {
                web_arg: "../frontend".to_string()
            }]
        );
    }

    #[test]
    fn detect_frontend_reads_framework_and_language() {
        let assert = |manifest: &str, framework: WebFramework, typescript: bool| {
            assert_eq!(
                detect_web_frontend(manifest),
                Some(WebFrontend {
                    framework,
                    typescript
                }),
                "{manifest}"
            );
        };
        // vanilla-ts / vanilla ship no dependencies at all.
        assert(
            r#"{"devDependencies":{"typescript":"~5.9","vite":"^7"}}"#,
            WebFramework::Vanilla,
            true,
        );
        assert(
            r#"{"devDependencies":{"vite":"^7"}}"#,
            WebFramework::Vanilla,
            false,
        );
        assert(
            r#"{"dependencies":{"react":"^19","react-dom":"^19"},"devDependencies":{"typescript":"~5.9"}}"#,
            WebFramework::React,
            true,
        );
        assert(
            r#"{"dependencies":{"react":"^19","react-dom":"^19"}}"#,
            WebFramework::React,
            false,
        );
        assert(
            r#"{"dependencies":{"preact":"^10"},"devDependencies":{"typescript":"~5.9"}}"#,
            WebFramework::Preact,
            true,
        );
        assert(
            r#"{"dependencies":{"vue":"^3"},"devDependencies":{"typescript":"~5.9","vue-tsc":"^3"}}"#,
            WebFramework::Vue,
            true,
        );
        // Vite's Svelte starter declares the framework as a devDependency —
        // it compiles away.
        assert(
            r#"{"devDependencies":{"svelte":"^5","typescript":"~5.9"}}"#,
            WebFramework::Svelte,
            true,
        );
        assert(
            r#"{"dependencies":{"solid-js":"^1"}}"#,
            WebFramework::Solid,
            false,
        );
        assert(r#"{"dependencies":{"lit":"^3"}}"#, WebFramework::Lit, false);
        // A framework we do not know: dependencies exist but match nothing.
        assert(
            r#"{"dependencies":{"@qwik.dev/core":"^2"}}"#,
            WebFramework::Other,
            false,
        );
        assert!(detect_web_frontend("not json").is_none());
    }

    /// The layout `create vite --template vanilla-ts` produces on Vite 8.
    fn write_vanilla_layout(web: &Path) {
        std::fs::create_dir_all(web.join("public")).unwrap();
        std::fs::create_dir_all(web.join("src/assets")).unwrap();
        std::fs::write(
            web.join("package.json"),
            r#"{"devDependencies":{"typescript":"~6.0","vite":"^8"}}"#,
        )
        .unwrap();
        std::fs::write(
            web.join("index.html"),
            "<html><head><title>web</title>\
             <link rel=\"icon\" type=\"image/svg+xml\" href=\"/favicon.svg\" />\
             </head><body><div id=\"app\"></div></body></html>",
        )
        .unwrap();
        std::fs::write(web.join("public/favicon.svg"), "<svg/>").unwrap();
        std::fs::write(web.join("public/icons.svg"), "<svg/>").unwrap();
        std::fs::write(web.join("src/main.ts"), "// vite starter").unwrap();
        std::fs::write(web.join("src/counter.ts"), "// counter").unwrap();
        std::fs::write(web.join("src/style.css"), "/* vite */").unwrap();
        std::fs::write(web.join("src/assets/typescript.svg"), "<svg/>").unwrap();
    }

    #[test]
    fn overlay_brands_a_vanilla_layout() {
        let temp = tempfile::tempdir().unwrap();
        let web = temp.path().join("web");
        write_vanilla_layout(&web);

        let report = apply_brand_overlay(&web, "My App").unwrap();
        assert!(report.branded);
        assert!(report.warnings.is_empty(), "{:?}", report.warnings);
        assert_eq!(
            report.frontend,
            Some(WebFrontend {
                framework: WebFramework::Vanilla,
                typescript: true
            })
        );

        assert!(web.join("public/waterui.svg").is_file());
        assert!(!web.join("public/favicon.svg").exists());
        assert!(!web.join("public/icons.svg").exists());
        assert!(!web.join("src/counter.ts").exists());
        assert!(web.join("src/waterui.d.ts").is_file());
        let main = std::fs::read_to_string(web.join("src/main.ts")).unwrap();
        assert!(main.contains("WaterUI + TypeScript"), "{main}");
        assert!(main.contains("'./assets/typescript.svg'"), "{main}");
        assert!(main.contains("invoke<string>('greet'"), "{main}");
        let html = std::fs::read_to_string(web.join("index.html")).unwrap();
        assert!(html.contains("<title>My App</title>"), "{html}");
        assert!(html.contains("\"/waterui.svg\""), "{html}");
        let style = std::fs::read_to_string(web.join("src/style.css")).unwrap();
        assert!(style.contains(".page"), "{style}");
    }

    #[test]
    fn overlay_skips_missing_files_with_warnings() {
        let temp = tempfile::tempdir().unwrap();
        let web = temp.path().join("web");
        std::fs::create_dir_all(&web).unwrap();
        // A react-ts manifest but no src/, no index.html: the overlay must
        // warn, not fail, and still ship the favicon.
        std::fs::write(
            web.join("package.json"),
            r#"{"dependencies":{"react":"^19"},"devDependencies":{"typescript":"~5.9"}}"#,
        )
        .unwrap();

        let report = apply_brand_overlay(&web, "App").unwrap();
        assert!(!report.branded);
        assert!(!report.warnings.is_empty());
        assert!(
            report.warnings.iter().any(|w| w.contains("src/App.tsx")),
            "{:?}",
            report.warnings
        );
        assert!(web.join("public/waterui.svg").is_file());
    }

    /// The tree handle reaches the grandchild the direct child re-execs —
    /// the shape `bun run dev` → `node vite` has — and refuses a child that
    /// does not lead its own group, since signalling that group would hit
    /// `water` itself.
    #[test]
    #[cfg(unix)]
    fn dev_server_tree_signals_the_grandchild_and_refuses_a_shared_group() {
        use std::os::unix::process::CommandExt as _;

        let mut leader = std::process::Command::new("sh")
            .args(["-c", "sleep 30 & wait"])
            .stdin(Stdio::null())
            .stdout(Stdio::null())
            .stderr(Stdio::null())
            .process_group(0)
            .spawn()
            .expect("sh spawns");
        let tree =
            dev_server_tree::DevServerTree::adopt(&leader).expect("the child leads its group");
        tree.signal(false);
        let status = leader.wait().expect("the leader is reaped");
        assert!(
            !status.success(),
            "SIGKILL to the group ends the leader: {status}"
        );

        let mut shared = std::process::Command::new("sh")
            .args(["-c", "exit 0"])
            .stdin(Stdio::null())
            .stdout(Stdio::null())
            .stderr(Stdio::null())
            .spawn()
            .expect("sh spawns");
        let refused = dev_server_tree::DevServerTree::adopt(&shared);
        let _ = shared.wait();
        assert!(refused.is_err(), "a child in our own group must be refused");
    }

    #[test]
    fn dev_url_from_line_finds_vite_local_url() {
        for line in [
            "  ➜  Local:   http://localhost:5173/",
            "  ➜  Local:   https://localhost:5173/",
            "Local: http://127.0.0.1:3000",
            "Local: http://[::1]:8080/",
            "ready in 42ms http://localhost:5173/app/index.html",
        ] {
            let url = dev_url_from_line(line).unwrap_or_else(|| panic!("no URL in {line:?}"));
            assert!(url.port().is_some(), "explicit port required: {line:?}");
        }
        assert_eq!(
            dev_url_from_line("  ➜  Local:   http://localhost:5173/")
                .unwrap()
                .as_str(),
            "http://localhost:5173/"
        );
    }

    #[test]
    fn dev_url_from_line_rejects_non_loopback_and_portless_urls() {
        for line in [
            "  ➜  Network: http://192.168.1.4:5173/",
            "  ➜  Network: http://172.20.10.2:5173/",
            "see https://localhost:5173.example.com/ for details",
            "no url here",
            "http://localhost is missing a port",
            "VITE v7.0.0  ready in 120 ms",
        ] {
            assert_eq!(dev_url_from_line(line), None, "unexpected URL in {line:?}");
        }
    }

    #[test]
    fn device_facing_url_rewrites_loopback_for_ios_device() {
        let url: url::Url = "http://localhost:5173/".parse().unwrap();
        for target in [
            DevTarget::Desktop,
            DevTarget::IosSimulator,
            DevTarget::Android,
        ] {
            assert_eq!(device_facing_url(target, &url).unwrap(), url);
        }
        let rewritten = device_facing_url(DevTarget::IosDevice, &url).unwrap();
        assert_eq!(rewritten.port(), Some(5173));
        let host = rewritten.host_str().expect("a host");
        let ip: std::net::Ipv4Addr = host.parse().expect("an IPv4 LAN host");
        assert!(!ip.is_loopback());
    }

    #[test]
    fn adb_reverse_args_forward_the_dev_url_port() {
        assert_eq!(
            adb_reverse_args("emulator-5554", 5173),
            ["-s", "emulator-5554", "reverse", "tcp:5173", "tcp:5173"]
        );
    }

    #[test]
    fn dev_url_port_reads_the_launch_environment() {
        assert_eq!(
            dev_url_port(std::iter::empty::<(&str, &str)>()).unwrap(),
            None
        );
        assert_eq!(
            dev_url_port([("WATERUI_DEV_URL", "http://localhost:5173/")].into_iter()).unwrap(),
            Some(5173)
        );
        assert!(
            dev_url_port([("WATERUI_DEV_URL", "not a url")].into_iter()).is_err(),
            "a malformed handoff fails loudly"
        );
    }

    #[test]
    fn dev_script_probes_dev_serve_start() {
        let temp = tempfile::tempdir().unwrap();
        let package_json = temp.path().join("package.json");

        std::fs::write(
            &package_json,
            r#"{"scripts":{"build":"vite build","serve":"vite preview"}}"#,
        )
        .unwrap();
        assert_eq!(dev_script(temp.path()).unwrap(), "serve");

        std::fs::write(&package_json, r#"{"scripts":{"start":"node server.js"}}"#).unwrap();
        assert_eq!(dev_script(temp.path()).unwrap(), "start");

        std::fs::write(
            &package_json,
            r#"{"scripts":{"dev":"vite","serve":"vite preview"}}"#,
        )
        .unwrap();
        assert_eq!(dev_script(temp.path()).unwrap(), "dev");

        std::fs::write(&package_json, r#"{"scripts":{"build":"vite build"}}"#).unwrap();
        let error = dev_script(temp.path()).unwrap_err().to_string();
        for script in ["dev", "serve", "start"] {
            assert!(error.contains(script), "error names the probes: {error}");
        }
    }
}