kraal 0.1.1

//! Workspace definitions loaded from KDL files.
//!
//! A workspace file is a Zellij layout, so existing `~/.config/zellij/layouts/*.kdl`
//! files work unchanged. Zellij writes KDL v1; KDL v2 is accepted too. Only the
//! subset kraal needs is interpreted: anything else is skipped and reported in
//! [`WorkspaceDef::warnings`] rather than failing the load.
//!
//! kraal extends panes with two properties: `preview="notes.md"` (show a rendered
//! file instead of a terminal) and `agent="claude"` (the pane runs a coding agent).
//! Zellij rejects unknown properties, so files using them are kraal-only.

use std::fmt::{self, Write as _};
use std::path::{Path, PathBuf};
use std::{env, fs, io};

use anyhow::{Context as _, Result, anyhow};
use kdl::{KdlDocument, KdlEntry, KdlError, KdlNode, KdlValue};
use serde::{Deserialize, Serialize};

/// How a split arranges its children.
#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash, Default, Serialize, Deserialize)]
pub enum Axis {
    /// Children placed left to right (Zellij `split_direction="vertical"`).
    Row,
    /// Children placed top to bottom (Zellij `split_direction="horizontal"`, the default).
    #[default]
    Column,
}

impl Axis {
    fn from_zellij(s: &str) -> Option<Self> {
        if s.eq_ignore_ascii_case("vertical") {
            Some(Self::Row)
        } else if s.eq_ignore_ascii_case("horizontal") {
            Some(Self::Column)
        } else {
            None
        }
    }

    fn zellij_name(self) -> &'static str {
        match self {
            Self::Row => "vertical",
            Self::Column => "horizontal",
        }
    }
}

/// Size of a split child along its parent's axis.
#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash, Serialize, Deserialize)]
pub enum SizeSpec {
    /// A fixed number of cells (columns in a row, lines in a column).
    Fixed(u16),
    /// A percentage (1-100) of the parent's extent.
    Percent(u16),
}

/// What a pane shows.
#[derive(Debug, Clone, PartialEq, Eq, Default, Serialize, Deserialize)]
pub enum PaneKind {
    /// A terminal running [`PaneDef::command`], or the default shell.
    #[default]
    Terminal,
    /// A rendered preview of a file (kraal extension `preview="..."`).
    Preview(PathBuf),
}

/// A leaf pane.
#[derive(Debug, Clone, PartialEq, Eq, Default, Serialize, Deserialize)]
pub struct PaneDef {
    /// Display name (Zellij `name`).
    pub name: Option<String>,
    /// Program to run; `None` runs the default shell.
    pub command: Option<String>,
    /// Arguments for `command`.
    pub args: Vec<String>,
    /// Effective working directory, already resolved against the enclosing tab and workspace.
    pub cwd: Option<PathBuf>,
    /// Whether this pane should get the focus in its tab.
    pub focus: bool,
    /// Terminal or file preview.
    pub kind: PaneKind,
    /// Coding agent hint (kraal extension `agent="..."`).
    pub agent: Option<String>,
    /// Wait for a keypress before starting `command`.
    pub start_suspended: bool,
    /// Close the pane when `command` exits instead of holding it open.
    pub close_on_exit: bool,
}

/// A tiled layout tree.
#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
pub enum LayoutNode {
    /// A single pane.
    Pane(PaneDef),
    /// Two or more children laid out along `axis`, each with an optional size.
    Split {
        /// Direction in which the children are placed.
        axis: Axis,
        /// Children in order, with their size along `axis` (`None` shares the remaining space).
        children: Vec<(LayoutNode, Option<SizeSpec>)>,
    },
}

impl LayoutNode {
    /// Leaf panes in depth-first order.
    pub fn panes(&self) -> Vec<&PaneDef> {
        let mut out = Vec::new();
        self.collect_panes(&mut out);
        out
    }

    fn collect_panes<'a>(&'a self, out: &mut Vec<&'a PaneDef>) {
        match self {
            Self::Pane(pane) => out.push(pane),
            Self::Split { children, .. } => {
                for (child, _) in children {
                    child.collect_panes(out);
                }
            }
        }
    }

    fn into_panes(self) -> Vec<PaneDef> {
        match self {
            Self::Pane(pane) => vec![pane],
            Self::Split { children, .. } => children.into_iter().flat_map(|(child, _)| child.into_panes()).collect(),
        }
    }
}

/// A tab: a tiled layout plus floating panes.
#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
pub struct TabDef {
    /// Tab title.
    pub name: Option<String>,
    /// Whether this tab should be active when the workspace opens.
    pub focus: bool,
    /// Effective working directory, already resolved against the workspace cwd.
    pub cwd: Option<PathBuf>,
    /// Tiled panes.
    pub root: LayoutNode,
    /// Floating panes, in declaration order.
    pub floating: Vec<PaneDef>,
}

impl TabDef {
    /// Tiled panes in depth-first order, then floating panes.
    pub fn panes(&self) -> Vec<&PaneDef> {
        let mut out = self.root.panes();
        out.extend(&self.floating);
        out
    }
}

/// A parsed workspace file.
#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
pub struct WorkspaceDef {
    /// Workspace name (the file stem).
    pub name: String,
    /// Workspace-wide working directory (Zellij `cwd "..."` inside `layout`).
    pub cwd: Option<PathBuf>,
    /// Tabs in order; never empty for a parsed file.
    pub tabs: Vec<TabDef>,
    /// Constructs that were skipped, as `line N: message`.
    pub warnings: Vec<String>,
}

impl WorkspaceDef {
    /// Every pane in tab order (tiled then floating), handy for listings.
    pub fn panes(&self) -> Vec<&PaneDef> {
        self.tabs.iter().flat_map(TabDef::panes).collect()
    }
}

/// Parse a workspace file. `name` is the workspace name (file stem).
///
/// Fails only on invalid KDL or a missing `layout` node. Relative `cwd` values are
/// resolved against the enclosing cwd (pane, then tab, then workspace) and a
/// leading `~/` is expanded with `$HOME`; panes and tabs without a `cwd` inherit it.
pub fn parse_workspace(name: &str, src: &str) -> Result<WorkspaceDef> {
    let doc = parse_kdl(src)?;
    let mut parser = Parser { src, warnings: Vec::new() };
    let mut layout = None;
    for node in doc.nodes() {
        match node.name().value() {
            "layout" if layout.is_none() => layout = Some(node),
            "layout" => parser.warn(node_pos(node), "extra `layout` node ignored"),
            other => parser.warn(node_pos(node), format!("unknown top-level node `{other}` ignored")),
        }
    }
    let layout = layout.context("no `layout` node")?;
    let (cwd, tabs) = parser.layout(layout);
    // Report in document order (the workspace cwd is read ahead of the rest).
    parser.warnings.sort_by_key(|(offset, _)| *offset);
    Ok(WorkspaceDef {
        name: name.to_owned(),
        cwd,
        tabs,
        warnings: parser.warnings.into_iter().map(|(_, msg)| msg).collect(),
    })
}

/// What [`valid_file_name`] accepts, said to the user.
pub const FILE_NAME_RULE: &str =
    "a workspace file name is one plain name: not empty, no \"/\" or control character, not starting with \".\"";

/// Whether `name` can name a definition file (`<name>.kdl`) inside the definitions directory:
/// one plain path component, so that it never reaches another directory, and no control
/// character (a newline would split the list of saved workspaces).
pub fn valid_file_name(name: &str) -> bool {
    !name.is_empty()
        && name.len() <= 200
        && !name.starts_with('.')
        && !name.contains(['/', '\\', '\0'])
        && !name.chars().any(char::is_control)
        && Path::new(name).components().count() == 1
}

/// The file name a workspace is saved under when none is given: its name when that is already
/// one plain name ([`valid_file_name`]). A group running a command is named after the whole
/// command, which may hold a `/` or be long: those become `_`, a name past 200 bytes is cut, and
/// whenever the name had to change, a digest of the whole is added, so that two workspaces never
/// share a file (`tail /var/log/a_b` and `tail /var/log/a/b` would otherwise both be
/// `tail _var_log_a_b`).
pub fn file_name_from(name: &str) -> String {
    if valid_file_name(name) && name.trim() == name {
        return name.to_string();
    }
    let replaced: String =
        name.chars().map(|c| if matches!(c, '/' | '\\' | '\0') || c.is_control() { '_' } else { c }).collect();
    // Trimmed first: a dot the spaces hid must not start the file name.
    let trimmed = replaced.trim();
    let out = match trimmed.strip_prefix('.') {
        Some(rest) => format!("_{rest}"),
        None if trimmed.is_empty() => "workspace".to_string(),
        None => trimmed.to_string(),
    };
    let digest = format!("-{:016x}", crate::text::fnv64(name));
    let mut cut = out.len().min(200 - digest.len());
    while !out.is_char_boundary(cut) {
        cut -= 1;
    }
    let file = format!("{}{digest}", &out[..cut]);
    if valid_file_name(&file) { file } else { format!("workspace{digest}") }
}

/// Load every `*.kdl` in `dir`, sorted by name. Unparseable files are returned as
/// `Err` entries with the path.
///
/// A missing directory yields an empty list; any other error reading it yields a
/// single `Err` entry for `dir` itself.
pub fn load_dir(dir: &Path) -> Vec<(PathBuf, Result<WorkspaceDef>)> {
    let entries = match fs::read_dir(dir) {
        Ok(entries) => entries,
        Err(e) if e.kind() == io::ErrorKind::NotFound => return Vec::new(),
        Err(e) => {
            let err = anyhow::Error::new(e).context(format!("reading {}", dir.display()));
            return vec![(dir.to_path_buf(), Err(err))];
        }
    };
    let mut paths: Vec<PathBuf> = entries
        .filter_map(|entry| entry.ok().map(|entry| entry.path()))
        .filter(|path| path.extension().is_some_and(|ext| ext == "kdl") && path.is_file())
        .collect();
    paths.sort();
    paths
        .into_iter()
        .map(|path| {
            let ws = load_file(&path);
            (path, ws)
        })
        .collect()
}

fn load_file(path: &Path) -> Result<WorkspaceDef> {
    let src = fs::read_to_string(path).with_context(|| format!("reading {}", path.display()))?;
    let name = path.file_stem().map(|stem| stem.to_string_lossy().into_owned()).unwrap_or_default();
    parse_workspace(&name, &src).with_context(|| format!("parsing {}", path.display()))
}

/// Serialise back to KDL (v1 syntax, Zellij-compatible, kraal extensions as
/// properties), so that `parse_workspace(name, &to_kdl(&ws))` round-trips.
///
/// The output includes Zellij's usual tab-bar/status-bar `default_tab_template`
/// (ignored by kraal) so the file also looks right when opened in Zellij. Paths are
/// written relative to the enclosing cwd only when they are relative themselves.
pub fn to_kdl(ws: &WorkspaceDef) -> String {
    let mut w = Writer::default();
    w.line(0, "layout {");
    if let Some(cwd) = &ws.cwd {
        w.line(1, &format!("cwd {}", quote(&path_text(cwd, None))));
    }
    for line in DEFAULT_TAB_TEMPLATE.lines() {
        w.line(1, line);
    }
    for tab in &ws.tabs {
        let mut head = String::from("tab");
        push_str(&mut head, "name", tab.name.as_deref());
        push_flag(&mut head, "focus", tab.focus);
        push_cwd(&mut head, tab.cwd.as_deref(), ws.cwd.as_deref());
        head.push_str(" {");
        w.line(1, &head);
        let base = tab.cwd.as_deref().or(ws.cwd.as_deref());
        w.node(&tab.root, None, base, 2);
        if !tab.floating.is_empty() {
            w.line(2, "floating_panes {");
            for pane in &tab.floating {
                w.pane(pane, None, base, 3);
            }
            w.line(2, "}");
        }
        w.line(1, "}");
    }
    w.line(0, "}");
    w.out
}

// ---------------------------------------------------------------------------
// Parsing

/// A layout node with its size in the parent split.
type SizedNode = (LayoutNode, Option<SizeSpec>);

/// Parses the KDL text, trying v2 first and then v1 (Zellij's dialect).
fn parse_kdl(src: &str) -> Result<KdlDocument> {
    let v2_err = match KdlDocument::parse_v2(src) {
        Ok(doc) => return Ok(doc),
        Err(e) => e,
    };
    let v1_err = match KdlDocument::parse_v1(src) {
        Ok(doc) => return Ok(doc),
        Err(e) => e,
    };
    // Neither dialect fits: report the parser that got further, which most likely
    // matches the dialect the author intended. Ties go to v1, Zellij's dialect.
    let err = if error_offset(&v2_err) > error_offset(&v1_err) { &v2_err } else { &v1_err };
    Err(anyhow!("invalid KDL: {}", describe_error(src, err)))
}

fn error_offset(err: &KdlError) -> usize {
    err.diagnostics.iter().map(|d| d.span.offset()).min().unwrap_or(0)
}

fn describe_error(src: &str, err: &KdlError) -> String {
    let parts: Vec<String> = err
        .diagnostics
        .iter()
        .take(3)
        .map(|d| {
            let line = line_of(src, d.span.offset());
            let msg = d.message.as_deref().unwrap_or("syntax error");
            match &d.help {
                Some(help) => format!("line {line}: {msg} ({help})"),
                None => format!("line {line}: {msg}"),
            }
        })
        .collect();
    if parts.is_empty() { "syntax error".to_owned() } else { parts.join("; ") }
}

/// 1-based line number of a byte offset.
fn line_of(src: &str, offset: usize) -> usize {
    let end = offset.min(src.len());
    src.as_bytes()[..end].iter().filter(|&&b| b == b'\n').count() + 1
}

fn node_pos(node: &KdlNode) -> usize {
    node.name().span().offset()
}

fn entry_pos(entry: &KdlEntry) -> usize {
    entry.span().offset()
}

fn entry_key(entry: &KdlEntry) -> Option<&str> {
    entry.name().map(|name| name.value())
}

fn child_nodes(node: &KdlNode) -> &[KdlNode] {
    node.children().map_or(&[], KdlDocument::nodes)
}

/// Converts a scalar to text; numbers and booleans are accepted where Zellij wants strings.
fn scalar_text(value: &KdlValue) -> Option<String> {
    match value {
        KdlValue::String(s) => Some(s.clone()),
        KdlValue::Integer(n) => Some(n.to_string()),
        KdlValue::Float(f) => Some(f.to_string()),
        KdlValue::Bool(b) => Some(b.to_string()),
        KdlValue::Null => None,
    }
}

/// Renders a value for messages; strings are always quoted.
fn show(value: &KdlValue) -> String {
    match value {
        KdlValue::String(s) => format!("{s:?}"),
        KdlValue::Integer(n) => n.to_string(),
        KdlValue::Float(f) => f.to_string(),
        KdlValue::Bool(b) => b.to_string(),
        KdlValue::Null => "null".to_owned(),
    }
}

fn parse_size(value: &KdlValue) -> Option<SizeSpec> {
    match value {
        KdlValue::Integer(n) => u16::try_from(*n).ok().filter(|&n| n > 0).map(SizeSpec::Fixed),
        KdlValue::String(s) => {
            let s = s.trim();
            match s.strip_suffix('%') {
                Some(pct) => {
                    pct.trim().parse::<u16>().ok().filter(|pct| (1..=100).contains(pct)).map(SizeSpec::Percent)
                }
                None => s.parse::<u16>().ok().filter(|&n| n > 0).map(SizeSpec::Fixed),
            }
        }
        _ => None,
    }
}

/// Expands a leading `~` or `~/` with `$HOME` and joins relative paths onto `base`.
fn resolve_path(base: Option<&Path>, raw: &str) -> PathBuf {
    let path = expand_home(raw);
    match base {
        Some(base) if path.is_relative() => base.join(path),
        _ => path,
    }
}

fn expand_home(raw: &str) -> PathBuf {
    let rest = if raw == "~" { Some("") } else { raw.strip_prefix("~/") };
    match (rest, env::var_os("HOME")) {
        (Some(rest), Some(home)) if !home.is_empty() => {
            let home = PathBuf::from(home);
            if rest.is_empty() { home } else { home.join(rest) }
        }
        _ => PathBuf::from(raw),
    }
}

/// The effective cwd of a node: its own (resolved) or the inherited one.
fn inherit_cwd(base: Option<&Path>, raw: Option<&str>) -> Option<PathBuf> {
    match raw {
        Some(raw) => Some(resolve_path(base, raw)),
        None => base.map(Path::to_path_buf),
    }
}

/// Builds a split, collapsing it to its child when there is only one.
fn collapse(axis: Axis, mut children: Vec<SizedNode>) -> Option<LayoutNode> {
    match children.len() {
        0 => None,
        1 => children.pop().map(|(node, _)| node),
        _ => Some(LayoutNode::Split { axis, children }),
    }
}

/// The tiled root of a tab; an empty tab gets one shell pane, as in Zellij.
fn tab_root(axis: Axis, panes: Vec<SizedNode>, cwd: Option<&Path>) -> LayoutNode {
    collapse(axis, panes)
        .unwrap_or_else(|| LayoutNode::Pane(PaneDef { cwd: cwd.map(Path::to_path_buf), ..PaneDef::default() }))
}

struct Parser<'a> {
    src: &'a str,
    /// Warnings with the byte offset they refer to.
    warnings: Vec<(usize, String)>,
}

impl Parser<'_> {
    fn warn(&mut self, offset: usize, msg: impl fmt::Display) {
        let line = line_of(self.src, offset);
        self.warnings.push((offset, format!("line {line}: {msg}")));
    }

    fn unknown_entry(&mut self, entry: &KdlEntry, owner: &str) {
        let msg = match entry_key(entry) {
            Some(key) => format!("unsupported property `{key}` on `{owner}` ignored"),
            None => format!("unexpected argument {} on `{owner}` ignored", show(entry.value())),
        };
        self.warn(entry_pos(entry), msg);
    }

    fn unknown_node(&mut self, node: &KdlNode, owner: &str) {
        let name = node.name().value();
        self.warn(node_pos(node), format!("unsupported node `{name}` in `{owner}` ignored"));
    }

    fn string(&mut self, entry: &KdlEntry) -> Option<String> {
        let text = scalar_text(entry.value());
        if text.is_none() {
            let key = entry_key(entry).unwrap_or("value");
            self.warn(entry_pos(entry), format!("`{key}` must be a string, ignored"));
        }
        text
    }

    fn path(&mut self, entry: &KdlEntry) -> Option<String> {
        let text = self.string(entry)?;
        if text.is_empty() {
            let key = entry_key(entry).unwrap_or("path");
            self.warn(entry_pos(entry), format!("empty `{key}` ignored"));
            return None;
        }
        Some(text)
    }

    fn flag(&mut self, entry: &KdlEntry) -> Option<bool> {
        match entry.value() {
            KdlValue::Bool(b) => Some(*b),
            KdlValue::String(s) if s == "true" => Some(true),
            KdlValue::String(s) if s == "false" => Some(false),
            other => {
                let key = entry_key(entry).unwrap_or("value");
                self.warn(entry_pos(entry), format!("`{key}` must be true or false, found {}; ignored", show(other)));
                None
            }
        }
    }

    /// A boolean child node such as `close_on_exit true`; a bare node means true.
    fn flag_node(&mut self, node: &KdlNode) -> Option<bool> {
        match node.entries().first() {
            None => Some(true),
            Some(entry) => self.flag(entry),
        }
    }

    fn axis(&mut self, entry: &KdlEntry) -> Option<Axis> {
        let axis = entry.value().as_string().and_then(Axis::from_zellij);
        if axis.is_none() {
            self.warn(
                entry_pos(entry),
                format!(
                    "`split_direction` must be \"vertical\" or \"horizontal\", found {}; ignored",
                    show(entry.value())
                ),
            );
        }
        axis
    }

    fn size(&mut self, entry: &KdlEntry) -> Option<SizeSpec> {
        let size = parse_size(entry.value());
        if size.is_none() {
            self.warn(
                entry_pos(entry),
                format!(
                    "invalid `size` {} (expected cells like 10 or a percentage like \"50%\"); ignored",
                    show(entry.value())
                ),
            );
        }
        size
    }

    fn layout(&mut self, node: &KdlNode) -> (Option<PathBuf>, Vec<TabDef>) {
        // Zellij treats these as the implicit tab's properties when there are no tabs.
        let mut name = None;
        let mut axis = None;
        for entry in node.entries() {
            match entry_key(entry) {
                Some("name") => name = self.string(entry),
                Some("split_direction") => axis = self.axis(entry),
                Some("hide_floating_panes") => {}
                _ => self.unknown_entry(entry, "layout"),
            }
        }
        let items = child_nodes(node);

        // The workspace cwd applies to every tab, wherever it is declared.
        let mut cwd = None;
        for item in items.iter().filter(|item| item.name().value() == "cwd") {
            match item.entries().first() {
                Some(entry) if entry_key(entry).is_none() => {
                    if let Some(raw) = self.path(entry) {
                        cwd = Some(resolve_path(None, &raw));
                    }
                }
                _ => self.warn(node_pos(item), "`cwd` expects one path argument; ignored"),
            }
        }

        let mut tabs = Vec::new();
        let mut panes = Vec::new();
        let mut floating = Vec::new();
        let mut stray = None;
        for item in items {
            let before = (panes.len(), floating.len());
            if self.tab_item(item, cwd.as_deref(), &mut panes, &mut floating) {
                if stray.is_none() && (panes.len(), floating.len()) != before {
                    stray = Some(node_pos(item));
                }
                continue;
            }
            match item.name().value() {
                "tab" => tabs.push(self.tab(item, cwd.as_deref())),
                // Templates only carry Zellij's own plugin bars; swap layouts are
                // alternative arrangements that do not change the initial layout.
                "cwd" | "default_tab_template" | "new_tab_template" | "swap_tiled_layout" | "swap_floating_layout" => {}
                "pane_template" | "tab_template" => {
                    let kind = item.name().value();
                    self.warn(node_pos(item), format!("`{kind}` is not supported; ignored"));
                }
                _ => self.unknown_node(item, "layout"),
            }
        }

        if tabs.is_empty() {
            let root = tab_root(axis.unwrap_or_default(), panes, cwd.as_deref());
            tabs.push(TabDef { name, focus: false, cwd: cwd.clone(), root, floating });
        } else {
            if let Some(at) = stray {
                self.warn(at, "panes outside `tab` nodes are ignored when tabs exist");
            }
            if name.is_some() || axis.is_some() {
                self.warn(node_pos(node), "`name`/`split_direction` on `layout` are ignored when tabs exist");
            }
        }
        (cwd, tabs)
    }

    fn tab(&mut self, node: &KdlNode, ws_cwd: Option<&Path>) -> TabDef {
        let mut name = None;
        let mut focus = false;
        let mut cwd_raw = None;
        let mut axis = Axis::default();
        for entry in node.entries() {
            match entry_key(entry) {
                Some("name") => name = self.string(entry),
                Some("focus") => focus = self.flag(entry).unwrap_or(focus),
                Some("cwd") => cwd_raw = self.path(entry),
                Some("split_direction") => axis = self.axis(entry).unwrap_or(axis),
                Some("hide_floating_panes") => {}
                _ => self.unknown_entry(entry, "tab"),
            }
        }
        let cwd = inherit_cwd(ws_cwd, cwd_raw.as_deref());
        let mut panes = Vec::new();
        let mut floating = Vec::new();
        for item in child_nodes(node) {
            if !self.tab_item(item, cwd.as_deref(), &mut panes, &mut floating) {
                self.unknown_node(item, "tab");
            }
        }
        let root = tab_root(axis, panes, cwd.as_deref());
        TabDef { name, focus, cwd, root, floating }
    }

    /// Handles a node that may appear among a tab's panes; returns false for anything else.
    fn tab_item(
        &mut self,
        node: &KdlNode,
        cwd: Option<&Path>,
        panes: &mut Vec<SizedNode>,
        floating: &mut Vec<PaneDef>,
    ) -> bool {
        match node.name().value() {
            "pane" | "plugin" => panes.extend(self.pane(node, cwd)),
            "floating_panes" => {
                let more = self.floating_panes(node, cwd);
                floating.extend(more);
            }
            // Template placeholder; meaningless outside a template.
            "children" => {}
            _ => return false,
        }
        true
    }

    /// Parses a `pane` node. Returns `None` for plugin panes, which kraal drops.
    fn pane(&mut self, node: &KdlNode, parent_cwd: Option<&Path>) -> Option<SizedNode> {
        if node.name().value() == "plugin" {
            return None;
        }
        let mut def = PaneDef::default();
        let mut size = None;
        let mut axis = Axis::default();
        let mut cwd_raw = None;
        let mut preview = None;
        let mut plugin = false;
        for entry in node.entries() {
            match entry_key(entry) {
                Some("name") => def.name = self.string(entry),
                Some("command") => def.command = self.string(entry),
                Some("cwd") => cwd_raw = self.path(entry),
                Some("focus") => def.focus = self.flag(entry).unwrap_or(def.focus),
                Some("size") => size = self.size(entry),
                Some("split_direction") => axis = self.axis(entry).unwrap_or(axis),
                Some("start_suspended") => {
                    def.start_suspended = self.flag(entry).unwrap_or(def.start_suspended);
                }
                Some("close_on_exit") => {
                    def.close_on_exit = self.flag(entry).unwrap_or(def.close_on_exit);
                }
                Some("preview") => preview = self.path(entry),
                Some("agent") => def.agent = self.string(entry),
                Some("plugin") => plugin = true,
                // Cosmetics and floating-pane geometry, which kraal does not model.
                Some("borderless" | "x" | "y" | "width" | "height" | "pinned") => {}
                _ => self.unknown_entry(entry, "pane"),
            }
        }
        let cwd = inherit_cwd(parent_cwd, cwd_raw.as_deref());

        let mut children = Vec::new();
        let mut container = false;
        for item in child_nodes(node) {
            match item.name().value() {
                "pane" => {
                    container = true;
                    children.extend(self.pane(item, cwd.as_deref()));
                }
                "plugin" => plugin = true,
                "args" => self.args(item, &mut def.args),
                "start_suspended" => {
                    def.start_suspended = self.flag_node(item).unwrap_or(def.start_suspended);
                }
                "close_on_exit" => {
                    def.close_on_exit = self.flag_node(item).unwrap_or(def.close_on_exit);
                }
                "children" => {}
                _ => self.unknown_node(item, "pane"),
            }
        }

        if container {
            if def.command.is_some() || !def.args.is_empty() || preview.is_some() || def.agent.is_some() {
                self.warn(
                    node_pos(node),
                    "`command`, `args`, `preview` and `agent` on a pane with child panes are ignored",
                );
            }
            // A container whose children were all plugins disappears with them.
            return collapse(axis, children).map(|node| (node, size));
        }
        if plugin {
            return None;
        }
        // `args` go to the command, or to the agent kraal starts (`agent="claude" { args "--model" "opus" }`).
        if def.command.is_none() && def.agent.is_none() && !def.args.is_empty() {
            self.warn(node_pos(node), "`args` without `command` or `agent` ignored");
            def.args.clear();
        }
        if let Some(raw) = preview {
            if def.command.is_some() {
                self.warn(node_pos(node), "`command` on a preview pane ignored");
                def.command = None;
                def.args.clear();
            }
            def.kind = PaneKind::Preview(resolve_path(cwd.as_deref(), &raw));
        }
        def.cwd = cwd;
        Some((LayoutNode::Pane(def), size))
    }

    fn args(&mut self, node: &KdlNode, out: &mut Vec<String>) {
        for entry in node.entries() {
            if entry_key(entry).is_some() {
                self.unknown_entry(entry, "args");
            } else if let Some(arg) = self.string(entry) {
                out.push(arg);
            }
        }
    }

    fn floating_panes(&mut self, node: &KdlNode, cwd: Option<&Path>) -> Vec<PaneDef> {
        for entry in node.entries() {
            self.unknown_entry(entry, "floating_panes");
        }
        let mut out = Vec::new();
        for item in child_nodes(node) {
            match item.name().value() {
                "pane" | "plugin" => match self.pane(item, cwd) {
                    Some((LayoutNode::Pane(pane), _)) => out.push(pane),
                    Some((split, _)) => {
                        self.warn(node_pos(item), "nested panes inside a floating pane are flattened");
                        out.extend(split.into_panes());
                    }
                    None => {}
                },
                _ => self.unknown_node(item, "floating_panes"),
            }
        }
        out
    }
}

// ---------------------------------------------------------------------------
// Writing

const DEFAULT_TAB_TEMPLATE: &str = r#"default_tab_template {
    pane size=1 borderless=true {
        plugin location="zellij:tab-bar"
    }
    children
    pane size=1 borderless=true {
        plugin location="zellij:status-bar"
    }
}"#;

#[derive(Default)]
struct Writer {
    out: String,
}

impl Writer {
    fn line(&mut self, depth: usize, text: &str) {
        for _ in 0..depth {
            self.out.push_str("    ");
        }
        self.out.push_str(text);
        self.out.push('\n');
    }

    fn node(&mut self, node: &LayoutNode, size: Option<SizeSpec>, base: Option<&Path>, depth: usize) {
        match node {
            LayoutNode::Pane(pane) => self.pane(pane, size, base, depth),
            LayoutNode::Split { axis, children } => {
                let mut head = String::from("pane");
                push_str(&mut head, "split_direction", Some(axis.zellij_name()));
                push_size(&mut head, size);
                head.push_str(" {");
                self.line(depth, &head);
                for (child, child_size) in children {
                    self.node(child, *child_size, base, depth + 1);
                }
                self.line(depth, "}");
            }
        }
    }

    fn pane(&mut self, pane: &PaneDef, size: Option<SizeSpec>, base: Option<&Path>, depth: usize) {
        let mut head = String::from("pane");
        push_str(&mut head, "name", pane.name.as_deref());
        push_str(&mut head, "command", pane.command.as_deref());
        push_cwd(&mut head, pane.cwd.as_deref(), base);
        push_size(&mut head, size);
        push_flag(&mut head, "focus", pane.focus);
        push_flag(&mut head, "start_suspended", pane.start_suspended);
        push_flag(&mut head, "close_on_exit", pane.close_on_exit);
        if let PaneKind::Preview(path) = &pane.kind {
            let own_cwd = pane.cwd.as_deref().or(base);
            push_str(&mut head, "preview", Some(&path_text(path, own_cwd)));
        }
        push_str(&mut head, "agent", pane.agent.as_deref());
        if pane.args.is_empty() {
            self.line(depth, &head);
            return;
        }
        head.push_str(" {");
        self.line(depth, &head);
        let args: Vec<String> = pane.args.iter().map(|arg| quote(arg)).collect();
        self.line(depth + 1, &format!("args {}", args.join(" ")));
        self.line(depth, "}");
    }
}

fn push_str(head: &mut String, key: &str, value: Option<&str>) {
    if let Some(value) = value {
        let _ = write!(head, " {key}={}", quote(value));
    }
}

fn push_flag(head: &mut String, key: &str, value: bool) {
    if value {
        let _ = write!(head, " {key}=true");
    }
}

fn push_size(head: &mut String, size: Option<SizeSpec>) {
    match size {
        Some(SizeSpec::Fixed(n)) => {
            let _ = write!(head, " size={n}");
        }
        Some(SizeSpec::Percent(n)) => {
            let _ = write!(head, " size=\"{n}%\"");
        }
        None => {}
    }
}

/// Writes `cwd` unless it is simply inherited from `base`.
fn push_cwd(head: &mut String, cwd: Option<&Path>, base: Option<&Path>) {
    if let Some(cwd) = cwd
        && Some(cwd) != base
    {
        push_str(head, "cwd", Some(&path_text(cwd, base)));
    }
}

/// Text for a path that the parser will resolve against `base`: absolute paths are
/// written as-is, relative ones relative to `base`.
fn path_text(path: &Path, base: Option<&Path>) -> String {
    let shown = match base {
        Some(base) if path.is_relative() => path.strip_prefix(base).unwrap_or(path),
        _ => path,
    };
    if shown.as_os_str().is_empty() { ".".to_owned() } else { shown.to_string_lossy().into_owned() }
}

/// Quotes a string using escapes valid in both KDL v1 and v2.
fn quote(s: &str) -> String {
    let mut out = String::with_capacity(s.len() + 2);
    out.push('"');
    for c in s.chars() {
        match c {
            '"' => out.push_str("\\\""),
            '\\' => out.push_str("\\\\"),
            '\n' => out.push_str("\\n"),
            '\r' => out.push_str("\\r"),
            '\t' => out.push_str("\\t"),
            '\u{8}' => out.push_str("\\b"),
            '\u{c}' => out.push_str("\\f"),
            // Control, bidi-override and BOM characters must not appear literally in KDL v2.
            c if c.is_control()
                || matches!(
                    c,
                    '\u{200e}' | '\u{200f}' | '\u{202a}'..='\u{202e}' | '\u{2066}'..='\u{2069}' | '\u{feff}'
                ) =>
            {
                let _ = write!(out, "\\u{{{:x}}}", u32::from(c));
            }
            c => out.push(c),
        }
    }
    out.push('"');
    out
}

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

    #[test]
    fn file_names_stay_in_their_directory() {
        for ok in ["work", "my workspace", "a.b"] {
            assert!(valid_file_name(ok), "{ok}");
        }
        for bad in ["", "..", ".", ".hidden", "../x", "a/b", "/etc/x", "a\\b", "a\nb", "tab\there"] {
            assert!(!valid_file_name(bad), "{bad:?}");
        }
        // A workspace's own name always gives a file name, distinct for distinct long names.
        let long =
            |end: &str| format!("prod: journalctl --no-pager --directory=/var/log/journal {}{end}", "x".repeat(300));
        for name in [
            "work",
            "prod: journalctl --directory=/var/log/journal",
            ".",
            "..",
            "",
            "a\nb",
            " .ops",
            "  ",
            " . ",
            "printf ok;\nsleep 600",
            &long("a"),
            &long("é"),
        ] {
            let file = file_name_from(name);
            assert!(valid_file_name(&file), "{name:?} gave {file:?}");
            assert!(!file.chars().any(char::is_control), "{name:?} gave {file:?}");
        }
        assert_eq!(file_name_from("work"), "work");
        assert!(file_name_from("prod: tail /var/log/x").starts_with("prod: tail _var_log_x-"));
        assert_ne!(file_name_from(&long("a")), file_name_from(&long("b")));
        // Names that differ only where they had to change still get files of their own, and
        // none of them takes the file of a workspace whose name needed no change.
        let names = ["prod: tail /var/log/a_b", "prod: tail /var/log/a/b", "prod: tail _var_log_a_b"];
        let files: std::collections::HashSet<String> = names.iter().map(|n| file_name_from(n)).collect();
        assert_eq!(files.len(), names.len(), "{files:?}");
    }

    const BARS: &str = r#"
    default_tab_template {
        pane size=1 borderless=true {
            plugin location="tab-bar"
        }
        children
        pane size=1 borderless=true {
            plugin location="status-bar"
        }
    }
"#;

    /// Excerpt of a real fleet layout (the kind a Wave or Zellij user keeps).
    fn zellij_fleet() -> String {
        format!(
            r#"// Zellij layout transposed from Wave workspace 'Kandy'
layout {{
{BARS}
    tab name="lfimmo" {{
        pane split_direction="vertical" {{
            pane focus=true name="192.0.2.11" command="ssh" {{
                args "admin@192.0.2.11"
            }}
            pane split_direction="horizontal" {{
                pane name="192.0.2.12" command="ssh" {{
                    args "admin@192.0.2.12"
                }}
                pane name="192.0.2.13" command="ssh" {{
                    args "admin@192.0.2.13"
                }}
            }}
        }}
    }}
    tab name="main" focus=true {{
        pane split_direction="vertical" {{
            pane split_direction="horizontal" {{
                pane name="pve-main" command="ssh" {{
                    args "-p" "2222" "root@pve-main.example.net"
                }}
                pane focus=true name="edge-proxy" command="ssh" {{
                    args "deploy@edge-proxy.example.net"
                }}
            }}
            pane split_direction="horizontal" {{
                pane cwd="/home/me"
                pane name="nvr" command="ssh" {{
                    args "root@nvr.example.net"
                }}
            }}
            pane name="198.51.100.249" command="ssh" {{
                args "deploy@198.51.100.249"
            }}
        }}
    }}
    tab name="test" {{
        pane focus=true name="app-test" command="ssh" {{
            args "-t" "deploy@app-test.example.net" "cd /srv/website && exec $SHELL -l"
        }}
    }}
}}
"#
        )
    }

    fn parse(src: &str) -> WorkspaceDef {
        parse_workspace("test", src).expect("parses")
    }

    fn parse_clean(src: &str) -> WorkspaceDef {
        let ws = parse(src);
        assert!(ws.warnings.is_empty(), "unexpected warnings: {:?}", ws.warnings);
        ws
    }

    fn leaf(node: &LayoutNode) -> &PaneDef {
        match node {
            LayoutNode::Pane(pane) => pane,
            LayoutNode::Split { .. } => panic!("expected a pane, got {node:?}"),
        }
    }

    fn split(node: &LayoutNode) -> (Axis, &[(LayoutNode, Option<SizeSpec>)]) {
        match node {
            LayoutNode::Split { axis, children } => (*axis, children),
            LayoutNode::Pane(_) => panic!("expected a split, got {node:?}"),
        }
    }

    fn assert_round_trip(ws: &WorkspaceDef) {
        let text = to_kdl(ws);
        let again = parse_workspace(&ws.name, &text).unwrap_or_else(|e| panic!("re-parse failed: {e:#}\n{text}"));
        assert_eq!(&again, ws, "round trip changed the workspace:\n{text}");
    }

    #[test]
    fn parses_zellij_fleet_layout() {
        let ws = parse_clean(&zellij_fleet());
        assert_eq!(ws.name, "test");
        assert_eq!(ws.cwd, None);
        let names: Vec<_> = ws.tabs.iter().map(|t| t.name.as_deref()).collect();
        assert_eq!(names, [Some("lfimmo"), Some("main"), Some("test")]);
        let focus: Vec<_> = ws.tabs.iter().map(|t| t.focus).collect();
        assert_eq!(focus, [false, true, false]);

        // Zellij "vertical" places children side by side.
        let (axis, children) = split(&ws.tabs[0].root);
        assert_eq!(axis, Axis::Row);
        assert_eq!(children.len(), 2);
        let first = leaf(&children[0].0);
        assert_eq!(first.name.as_deref(), Some("192.0.2.11"));
        assert_eq!(first.command.as_deref(), Some("ssh"));
        assert_eq!(first.args, ["admin@192.0.2.11"]);
        assert!(first.focus);
        assert_eq!(first.kind, PaneKind::Terminal);
        let (inner_axis, inner) = split(&children[1].0);
        assert_eq!(inner_axis, Axis::Column);
        assert_eq!(inner.len(), 2);
        assert!(!leaf(&inner[0].0).focus);
        assert_eq!(ws.tabs.iter().map(|t| t.panes().len()).sum::<usize>(), 9);
    }

    #[test]
    fn keeps_multi_value_args() {
        let ws = parse_clean(&zellij_fleet());
        let (_, columns) = split(&ws.tabs[1].root);
        let (_, top) = split(&columns[0].0);
        assert_eq!(leaf(&top[0].0).args, ["-p", "2222", "root@pve-main.example.net"]);
        let pool = leaf(&ws.tabs[2].root);
        assert_eq!(pool.args, ["-t", "deploy@app-test.example.net", "cd /srv/website && exec $SHELL -l"]);
    }

    #[test]
    fn single_pane_tab_is_the_root() {
        let ws = parse_clean(&zellij_fleet());
        let pool = leaf(&ws.tabs[2].root);
        assert_eq!(pool.name.as_deref(), Some("app-test"));
        assert!(pool.focus);
    }

    #[test]
    fn bare_pane_is_a_shell() {
        let ws = parse_clean(&zellij_fleet());
        let (_, columns) = split(&ws.tabs[1].root);
        let (_, middle) = split(&columns[1].0);
        let shell = leaf(&middle[0].0);
        assert_eq!(shell, &PaneDef { cwd: Some(PathBuf::from("/home/me")), ..PaneDef::default() });
        let src = "layout {\n    tab name=\"empty\"\n    tab { pane; }\n}\n";
        let ws = parse_clean(src);
        assert_eq!(ws.tabs[0].root, LayoutNode::Pane(PaneDef::default()));
        assert_eq!(ws.tabs[1].root, LayoutNode::Pane(PaneDef::default()));
    }

    #[test]
    fn panes_without_tabs_form_one_tab() {
        let src = r#"
layout {
    pane size=1 borderless=true {
        plugin location="zellij:tab-bar"
    }
    pane command="htop"
    pane command="btop" focus=true
    floating_panes {
        pane command="lazygit" x=10 y="10%" width="80%" height=20
    }
}
"#;
        let ws = parse_clean(src);
        assert_eq!(ws.tabs.len(), 1);
        let tab = &ws.tabs[0];
        assert_eq!(tab.name, None);
        let (axis, children) = split(&tab.root);
        assert_eq!(axis, Axis::Column);
        assert_eq!(children.len(), 2);
        assert!(leaf(&children[1].0).focus);
        assert_eq!(tab.floating.len(), 1);
        assert_eq!(tab.floating[0].command.as_deref(), Some("lazygit"));

        let ws = parse_clean("layout {\n}\n");
        assert_eq!(ws.tabs.len(), 1);
        assert_eq!(ws.tabs[0].root, LayoutNode::Pane(PaneDef::default()));

        let ws = parse_clean("layout name=\"solo\" split_direction=\"vertical\" {\n    pane\n    pane\n}\n");
        assert_eq!(ws.tabs[0].name.as_deref(), Some("solo"));
        assert_eq!(split(&ws.tabs[0].root).0, Axis::Row);
    }

    #[test]
    fn parses_sizes() {
        let src = r#"
layout {
    tab split_direction="vertical" {
        pane size=30
        pane size="25%"
        pane size=" 40 % "
        pane
    }
}
"#;
        let ws = parse_clean(src);
        let (axis, children) = split(&ws.tabs[0].root);
        assert_eq!(axis, Axis::Row);
        let sizes: Vec<_> = children.iter().map(|(_, size)| *size).collect();
        assert_eq!(sizes, [Some(SizeSpec::Fixed(30)), Some(SizeSpec::Percent(25)), Some(SizeSpec::Percent(40)), None]);

        let bad =
            parse("layout {\n    pane size=0\n    pane size=\"150%\"\n    pane size=1.5\n    pane size=70000\n}\n");
        assert_eq!(bad.warnings.len(), 4, "{:?}", bad.warnings);
        assert!(bad.warnings.iter().all(|w| w.contains("invalid `size`")));
        let (_, children) = split(&bad.tabs[0].root);
        assert!(children.iter().all(|(_, size)| size.is_none()));
    }

    #[test]
    fn collapses_single_child_splits() {
        let src = r#"
layout {
    tab {
        pane split_direction="vertical" {
            pane size="30%" split_direction="horizontal" {
                pane size=5 split_direction="vertical" {
                    pane command="htop"
                }
            }
            pane command="top"
        }
    }
}
"#;
        let ws = parse_clean(src);
        let (axis, children) = split(&ws.tabs[0].root);
        assert_eq!(axis, Axis::Row);
        // The chain of one-child containers collapses to the leaf, keeping the outer size.
        assert_eq!(leaf(&children[0].0).command.as_deref(), Some("htop"));
        assert_eq!(children[0].1, Some(SizeSpec::Percent(30)));
    }

    #[test]
    fn drops_plugin_panes() {
        let src = r#"
layout {
    tab {
        pane size=1 borderless=true {
            plugin location="zellij:tab-bar"
        }
        pane command="htop"
        pane split_direction="vertical" {
            pane { plugin location="zellij:strider"; }
            plugin location="zellij:compact-bar"
        }
        pane plugin="zellij:status-bar"
    }
    tab {
        pane { plugin location="zellij:session-manager"; }
    }
}
"#;
        let ws = parse_clean(src);
        assert_eq!(leaf(&ws.tabs[0].root).command.as_deref(), Some("htop"));
        // A tab with nothing but plugins still gets a shell, as in Zellij.
        assert_eq!(ws.tabs[1].root, LayoutNode::Pane(PaneDef::default()));
    }

    #[test]
    fn parses_floating_panes() {
        let src = r#"
layout {
    tab name="dev" cwd="/srv" {
        pane command="nvim"
        floating_panes {
            pane command="lazygit" width="80%" height="80%" x="10%" y="10%" pinned=true
            pane cwd="logs" name="tail" command="tail" close_on_exit=true {
                args "-f" "app.log"
            }
            pane { plugin location="zellij:filepicker"; }
        }
    }
}
"#;
        let ws = parse_clean(src);
        let tab = &ws.tabs[0];
        assert_eq!(tab.floating.len(), 2);
        assert_eq!(tab.floating[0].cwd, Some(PathBuf::from("/srv")));
        assert_eq!(tab.floating[1].cwd, Some(PathBuf::from("/srv/logs")));
        assert!(tab.floating[1].close_on_exit);
        let commands: Vec<_> = ws.panes().iter().map(|p| p.command.clone()).collect();
        assert_eq!(commands, [Some("nvim".to_owned()), Some("lazygit".to_owned()), Some("tail".to_owned())]);
    }

    #[test]
    fn suspend_and_close_flags_as_properties_or_children() {
        let src = r#"
layout {
    pane command="a" start_suspended=true close_on_exit=false
    pane command="b" {
        start_suspended true
        close_on_exit true
    }
    pane command="c" {
        close_on_exit
    }
}
"#;
        let ws = parse_clean(src);
        let flags: Vec<_> = ws.panes().iter().map(|p| (p.start_suspended, p.close_on_exit)).collect();
        assert_eq!(flags, [(true, false), (true, true), (false, true)]);
    }

    #[test]
    fn kraal_extensions() {
        let src = r#"
layout {
    tab name="agents" cwd="/work/kraal" {
        pane split_direction="vertical" {
            pane name="claude" command="claude" agent="claude" focus=true
            pane name="plan" preview="docs/PLAN.md" size="40%"
            pane preview="/etc/motd"
        }
    }
}
"#;
        let ws = parse_clean(src);
        let panes = ws.panes();
        assert_eq!(panes[0].agent.as_deref(), Some("claude"));
        assert_eq!(panes[0].kind, PaneKind::Terminal);
        assert_eq!(panes[1].kind, PaneKind::Preview(PathBuf::from("/work/kraal/docs/PLAN.md")));
        assert_eq!(panes[1].command, None);
        assert_eq!(panes[2].kind, PaneKind::Preview(PathBuf::from("/etc/motd")));

        let ws = parse("layout {\n    pane preview=\"a.md\" command=\"cat\" {\n        args \"x\"\n    }\n}\n");
        let pane = leaf(&ws.tabs[0].root);
        assert_eq!(pane.kind, PaneKind::Preview(PathBuf::from("a.md")));
        assert_eq!((pane.command.as_deref(), pane.args.len()), (None, 0));
        assert_eq!(ws.warnings.len(), 1, "{:?}", ws.warnings);
    }

    #[test]
    fn resolves_cwd_chain() {
        let src = r#"
layout {
    tab name="rel" cwd="projects" {
        pane split_direction="vertical" cwd="kraal" {
            pane cwd="src"
            pane cwd="/tmp"
            pane
        }
    }
    tab name="abs" cwd="/opt" {
        pane
    }
    tab name="inherit" {
        pane cwd="notes"
    }
    cwd "/home/me"
}
"#;
        let ws = parse_clean(src);
        assert_eq!(ws.cwd, Some(PathBuf::from("/home/me")));
        assert_eq!(ws.tabs[0].cwd, Some(PathBuf::from("/home/me/projects")));
        let cwds: Vec<_> = ws.tabs[0].panes().iter().map(|p| p.cwd.clone()).collect();
        assert_eq!(
            cwds,
            [
                Some(PathBuf::from("/home/me/projects/kraal/src")),
                Some(PathBuf::from("/tmp")),
                Some(PathBuf::from("/home/me/projects/kraal")),
            ]
        );
        assert_eq!(ws.tabs[1].cwd, Some(PathBuf::from("/opt")));
        assert_eq!(leaf(&ws.tabs[1].root).cwd, Some(PathBuf::from("/opt")));
        assert_eq!(ws.tabs[2].cwd, Some(PathBuf::from("/home/me")));
        assert_eq!(leaf(&ws.tabs[2].root).cwd, Some(PathBuf::from("/home/me/notes")));
    }

    #[test]
    fn expands_home() {
        let ws = parse_clean(
            "layout {\n    tab cwd=\"/elsewhere\" {\n        pane cwd=\"~/code\"\n        pane cwd=\"~\"\n        pane cwd=\"~other/x\"\n    }\n}\n",
        );
        let cwds: Vec<_> = ws.panes().iter().map(|p| p.cwd.clone().unwrap()).collect();
        match env::var_os("HOME").filter(|h| !h.is_empty()) {
            Some(home) => {
                let home = PathBuf::from(home);
                assert_eq!(cwds[0], home.join("code"));
                assert_eq!(cwds[1], home);
            }
            None => assert_eq!(cwds[0], PathBuf::from("/elsewhere/~/code")),
        }
        // Only the current user's home is expanded.
        assert_eq!(cwds[2], PathBuf::from("/elsewhere/~other/x"));
    }

    #[test]
    fn accepts_kdl_v2() {
        let src = r##"
layout {
    tab name=main focus=#true split_direction=vertical {
        pane command=htop size="30%" close_on_exit=#true
        pane focus=#true command=ls {
            args -la "/tmp"
        }
    }
    tab name=#"raw "quoted""#
}
"##;
        let ws = parse_clean(src);
        assert!(ws.tabs[0].focus);
        let (axis, children) = split(&ws.tabs[0].root);
        assert_eq!(axis, Axis::Row);
        assert_eq!(children[0].1, Some(SizeSpec::Percent(30)));
        assert!(leaf(&children[0].0).close_on_exit);
        let ls = leaf(&children[1].0);
        assert!(ls.focus);
        assert_eq!(ls.args, ["-la", "/tmp"]);
        assert_eq!(ws.tabs[1].name.as_deref(), Some("raw \"quoted\""));
    }

    #[test]
    fn warns_on_unknown_constructs() {
        let src = r#"layout {
    mystery 1
    pane_template name="ssh" {
        pane command="ssh"
    }
    tab name="t" color="red" {
        pane command="ls" stacked=true {
            args "-l"
            bogus
        }
        pane "positional"
        pane focus="maybe"
        pane split_direction="diagonal"
        pane { args "orphan"; }
        what
    }
}
keybinds {
}
"#;
        let ws = parse(src);
        let expected = [
            "line 2: unsupported node `mystery` in `layout` ignored",
            "line 3: `pane_template` is not supported; ignored",
            "line 6: unsupported property `color` on `tab` ignored",
            "line 7: unsupported property `stacked` on `pane` ignored",
            "line 9: unsupported node `bogus` in `pane` ignored",
            "line 11: unexpected argument \"positional\" on `pane` ignored",
            "line 12: `focus` must be true or false, found \"maybe\"; ignored",
            "line 13: `split_direction` must be \"vertical\" or \"horizontal\", found \"diagonal\"; ignored",
            "line 14: `args` without `command` or `agent` ignored",
            "line 15: unsupported node `what` in `tab` ignored",
            "line 18: unknown top-level node `keybinds` ignored",
        ];
        assert_eq!(ws.warnings, expected);
        // Everything that could be understood is still there.
        assert_eq!(ws.panes().len(), 5);
        assert_eq!(ws.panes()[0].args, ["-l"]);
    }

    #[test]
    fn warns_on_panes_outside_tabs() {
        let src = "layout {\n    pane command=\"stray\"\n    tab name=\"a\"\n}\n";
        let ws = parse(src);
        assert_eq!(ws.tabs.len(), 1);
        assert_eq!(ws.panes()[0].command, None);
        assert_eq!(ws.warnings, ["line 2: panes outside `tab` nodes are ignored when tabs exist"]);
    }

    #[test]
    fn rejects_invalid_files() {
        let err = parse_workspace("x", "layout {\n    pane name=\"a\n}\n").unwrap_err();
        let msg = format!("{err:#}");
        assert!(msg.starts_with("invalid KDL: line "), "{msg}");

        let err = parse_workspace("x", "layout {\n    tab {\n        pane focus=true\n    \n").unwrap_err();
        assert!(format!("{err:#}").contains("invalid KDL"));

        let err = parse_workspace("x", "tab name=\"a\"\n").unwrap_err();
        assert_eq!(err.to_string(), "no `layout` node");
    }

    #[test]
    fn round_trips_zellij_layout() {
        let ws = parse_clean(&zellij_fleet());
        assert_round_trip(&ws);
        let text = to_kdl(&ws);
        // Plain Zellij input must produce plain Zellij output.
        assert!(!text.contains("preview=") && !text.contains("agent="));
        assert!(text.contains("args \"-p\" \"2222\" \"root@pve-main.example.net\""));
        assert!(text.contains("default_tab_template"));
    }

    #[test]
    fn round_trips_every_feature() {
        let src = r#"
layout {
    cwd "/home/me"
    tab name="agents" cwd="work" focus=true {
        pane split_direction="vertical" {
            pane name="claude" command="claude" agent="claude" focus=true size="60%"
            pane split_direction="horizontal" size=40 cwd="docs" {
                pane preview="PLAN.md" size=10
                pane preview="/etc/motd"
                pane command="cargo" start_suspended=true close_on_exit=true cwd="/tmp" {
                    args "watch" "-x" "test"
                }
            }
        }
        floating_panes {
            pane command="lazygit" cwd="sub" focus=true
            pane agent="claude:pro" {
                args "--model" "opus"
            }
        }
    }
    tab name="fleet" {
        pane command="ssh" name="web" {
            args "-p" "44022" "root@web"
        }
    }
}
"#;
        let ws = parse_clean(src);
        assert_round_trip(&ws);
        // An agent keeps the arguments it was saved with.
        let agent = ws.panes().into_iter().find(|p| p.agent.as_deref() == Some("claude:pro")).unwrap();
        assert_eq!(agent.args, ["--model", "opus"]);
    }

    #[test]
    fn round_trips_relative_cwds_and_odd_strings() {
        let ws = WorkspaceDef {
            name: "odd".to_owned(),
            cwd: Some(PathBuf::from("projects")),
            tabs: vec![
                TabDef {
                    name: Some("quote \" back \\ nl \n tab \t bell \u{7} rtl \u{202e} é 🦀".to_owned()),
                    focus: false,
                    cwd: Some(PathBuf::from("projects/kraal")),
                    root: LayoutNode::Split {
                        axis: Axis::Row,
                        children: vec![
                            (
                                LayoutNode::Pane(PaneDef {
                                    command: Some("sh".to_owned()),
                                    args: vec!["-c".to_owned(), "echo \"$HOME\" && true".to_owned(), String::new()],
                                    cwd: Some(PathBuf::from("projects/kraal/src")),
                                    kind: PaneKind::Terminal,
                                    ..PaneDef::default()
                                }),
                                Some(SizeSpec::Fixed(80)),
                            ),
                            (
                                LayoutNode::Pane(PaneDef {
                                    cwd: Some(PathBuf::from("projects/kraal")),
                                    kind: PaneKind::Preview(PathBuf::from("projects/kraal")),
                                    ..PaneDef::default()
                                }),
                                None,
                            ),
                        ],
                    },
                    floating: vec![],
                },
                TabDef {
                    name: None,
                    focus: true,
                    cwd: Some(PathBuf::from("projects")),
                    root: LayoutNode::Pane(PaneDef { cwd: Some(PathBuf::from("projects")), ..PaneDef::default() }),
                    floating: vec![],
                },
            ],
            warnings: vec![],
        };
        assert_round_trip(&ws);
    }

    #[test]
    fn serde_round_trip() {
        let ws = parse_clean(&zellij_fleet());
        let json = serde_json::to_string(&ws).unwrap();
        let back: WorkspaceDef = serde_json::from_str(&json).unwrap();
        assert_eq!(back, ws);
    }

    #[test]
    fn load_dir_sorts_and_reports_errors() {
        let nanos = std::time::SystemTime::now().duration_since(std::time::UNIX_EPOCH).map_or(0, |d| d.as_nanos());
        let dir = env::temp_dir().join(format!("kraal-ws-test-{}-{nanos}", std::process::id()));
        fs::create_dir_all(&dir).unwrap();
        fs::write(dir.join("zeta.kdl"), "layout {\n    pane\n}\n").unwrap();
        fs::write(dir.join("alpha.kdl"), zellij_fleet()).unwrap();
        fs::write(dir.join("broken.kdl"), "layout {\n").unwrap();
        fs::write(dir.join("notes.txt"), "not a layout").unwrap();

        let loaded = load_dir(&dir);
        let names: Vec<_> =
            loaded.iter().map(|(path, _)| path.file_name().unwrap().to_string_lossy().into_owned()).collect();
        assert_eq!(names, ["alpha.kdl", "broken.kdl", "zeta.kdl"]);
        assert_eq!(loaded[0].1.as_ref().unwrap().name, "alpha");
        let err = loaded[1].1.as_ref().unwrap_err();
        assert!(format!("{err:#}").contains("broken.kdl"), "{err:#}");
        assert_eq!(loaded[2].1.as_ref().unwrap().tabs.len(), 1);

        fs::remove_dir_all(&dir).unwrap();
        assert!(load_dir(&dir).is_empty());
    }

    /// Parses the real layouts in `~/.config/zellij/layouts` (run with `--ignored`).
    #[test]
    #[ignore = "depends on the local Zellij configuration"]
    fn parses_local_zellij_layouts() {
        let home = env::var_os("HOME").expect("HOME is set");
        let dir = PathBuf::from(home).join(".config/zellij/layouts");
        let loaded = load_dir(&dir);
        assert!(!loaded.is_empty(), "no layouts in {}", dir.display());
        for (path, ws) in loaded {
            let ws = ws.unwrap_or_else(|e| panic!("{}: {e:#}", path.display()));
            assert!(ws.warnings.is_empty(), "{}: {:?}", path.display(), ws.warnings);
            assert_round_trip(&ws);
            println!("{}: {} tabs, {} panes", ws.name, ws.tabs.len(), ws.panes().len());
        }
    }
}