puressh 0.1.3

//! `ssh_config(5)` parsing — see [`SshClientConfig`].
//!
//! Only the keywords the puressh client binaries actually consume today are
//! recognised; any other keyword is rejected as
//! [`ConfigError::UnknownKeyword`]. This is deliberate: the scope is "config
//! values that change observable behaviour", and silently dropping an
//! unrecognised knob is worse than failing loudly.
//!
//! The file is a sequence of blocks. `Host <pattern>` opens a host-pattern
//! block, `Match <criteria>` opens a Match block, and everything before the
//! first block belongs to an implicit "global" Host * block. Settings inside a
//! block apply when the block's selector matches the lookup target;
//! [`SshClientConfig::lookup`] walks the blocks in order with OpenSSH's
//! first-match-wins precedence (scalars) and cumulative-concatenation
//! semantics (`IdentityFile`, `LocalForward`, `RemoteForward`).

use alloc::format;
use alloc::string::{String, ToString};
use alloc::vec;
use alloc::vec::Vec;

use super::ConfigError;
use super::algos::{AlgoCategory, resolve_algo_list};
use super::glob::{HostPattern, host_matches};
use super::match_block::{ExecPolicy, MatchCondition, MatchContext, all_match, parse_match_line};
use super::parser::{ParsedLine, tokenize};

/// `StrictHostKeyChecking` value — maps OpenSSH's keyword set to puressh's
/// TOFU policy. Re-exported as `puressh::config::StrictMode` and re-exported
/// once more from `src/bin/common.rs` so existing binaries keep compiling.
#[derive(Clone, Copy, Debug, PartialEq, Eq)]
pub enum StrictMode {
    /// `yes`: refuse Unknown; reject Mismatch.
    Yes,
    /// `no`: accept Unknown silently AND tolerate Mismatch (insecure).
    No,
    /// `accept-new`: silently accept Unknown; still reject Mismatch.
    AcceptNew,
    /// `ask` (OpenSSH default): prompt on Unknown; reject Mismatch.
    Ask,
}

/// `RequestTTY` value. Distinct from a CLI bool: `Auto` means "PTY if local
/// stdin is a tty" — the binary needs the original token so it can decide
/// late.
#[derive(Clone, Copy, Debug, PartialEq, Eq)]
pub enum RequestTty {
    /// `no`: never allocate.
    No,
    /// `yes`: allocate when there's an interactive session (default for
    /// interactive shells).
    Yes,
    /// `force`: always allocate.
    Force,
    /// `auto`: allocate iff local stdin is a tty.
    Auto,
}

/// `AddressFamily` value — filters the addresses a hostname resolves to
/// before we attempt a connection.
#[derive(Clone, Copy, Debug, PartialEq, Eq)]
pub enum AddressFamily {
    /// `any`: no filtering (default).
    Any,
    /// `inet`: IPv4 only.
    Inet,
    /// `inet6`: IPv6 only.
    Inet6,
}

/// `GatewayPorts` value — controls the bind address of client-side
/// `-L` / `-D` listeners.
#[derive(Clone, Copy, Debug, PartialEq, Eq)]
pub enum GatewayPorts {
    /// `no`: bind loopback (`127.0.0.1`) only (default).
    No,
    /// `yes`: bind all interfaces (`0.0.0.0`).
    Yes,
    /// `clientspecified`: honour the bind address spelled out in the
    /// forward spec; fall back to loopback when none was given.
    ClientSpecified,
}

/// `IdentityAgent` value — overrides which ssh-agent socket the client
/// talks to.
#[derive(Clone, Debug, PartialEq, Eq)]
pub enum IdentityAgent {
    /// `none`: never consult an agent.
    None,
    /// A filesystem path to the agent socket. The literal token
    /// `SSH_AUTH_SOCK` (and `$SSH_AUTH_SOCK`) is preserved verbatim here
    /// and expanded against the environment at the honoring site.
    Path(String),
}

/// `ControlMaster` value — controls connection-multiplexing role.
///
/// `ask` / `autoask` would prompt the user for permission before
/// reusing/establishing a master. puressh has no interactive confirmation
/// path for this decision, so both are rejected at parse time as
/// [`ConfigError::Unsupported`] rather than silently downgraded to `yes`
/// (which would defeat the user's explicit request to be asked).
#[derive(Clone, Copy, Debug, PartialEq, Eq)]
pub enum ControlMaster {
    /// `no` (default): never multiplex. Open a fresh connection.
    No,
    /// `yes`: become the master. Fails if the `ControlPath` socket already
    /// has a live master answering.
    Yes,
    /// `auto`: reuse an existing master if the socket answers; otherwise
    /// connect normally and become the master.
    Auto,
}

/// `ControlPersist` value — how long a master lingers after its foreground
/// session ends.
#[derive(Clone, Copy, Debug, PartialEq, Eq)]
pub enum ControlPersist {
    /// `no`: the master exits as soon as its own foreground session ends
    /// (still serving any clients that attached, but tearing down once the
    /// initiating session finishes — matches OpenSSH `no`).
    No,
    /// `yes`: the master persists indefinitely after the foreground session
    /// ends, until explicitly stopped (or the process exits).
    Yes,
    /// `<N>` (or `<N>[smh]`): linger N seconds after the last client
    /// detaches, then unlink the socket and exit.
    Seconds(u64),
}

/// `ObscureKeystrokeTiming` value (OpenSSH 9.5+). Controls keystroke-timing
/// obfuscation on interactive (pty) sessions: when on, the client releases
/// keystrokes on a fixed cadence and pads idle gaps with `ping@openssh.com`
/// chaff so the on-wire packet rate is constant while typing.
///
/// OpenSSH syntax: `yes` (on, default interval 20 ms), `no`, or
/// `interval:<spec>` where `<spec>` is a millisecond count (`interval:80`) or
/// an OpenSSH time value with unit suffixes (`interval:1s`). The OpenSSH
/// default when the option is unset is `yes` at 20 ms.
#[derive(Clone, Copy, Debug, PartialEq, Eq)]
pub enum ObscureKeystrokeTiming {
    /// `no`: disabled — keystrokes are sent immediately as today.
    Off,
    /// `yes` / `interval:<spec>`: enabled with the given cadence in
    /// milliseconds. `yes` ⇒ `On { interval_ms: 20 }`.
    On {
        /// Cadence between cadence ticks, in milliseconds.
        interval_ms: u32,
    },
}

impl ObscureKeystrokeTiming {
    /// OpenSSH's default cadence interval (20 ms) used by bare `yes`.
    pub const DEFAULT_INTERVAL_MS: u32 = 20;

    /// The effective default when the option is unset: on at 20 ms, matching
    /// OpenSSH's compiled-in default.
    pub fn default_on() -> Self {
        ObscureKeystrokeTiming::On {
            interval_ms: Self::DEFAULT_INTERVAL_MS,
        }
    }

    /// `true` if obfuscation is enabled.
    pub fn is_on(&self) -> bool {
        matches!(self, ObscureKeystrokeTiming::On { .. })
    }

    /// The cadence interval in milliseconds when on; `None` when off.
    pub fn interval_ms(&self) -> Option<u32> {
        match self {
            ObscureKeystrokeTiming::On { interval_ms } => Some(*interval_ms),
            ObscureKeystrokeTiming::Off => None,
        }
    }
}

/// One `DynamicForward` entry — a local SOCKS proxy listener. Wire form
/// `[bind:]port`, e.g. `1080` or `127.0.0.1:1080`.
#[derive(Clone, Debug, PartialEq, Eq)]
pub struct DynamicForwardSpec {
    /// Local bind address; `None` ⇒ loopback (subject to `GatewayPorts`).
    pub bind_addr: Option<String>,
    /// Local port the SOCKS listener binds.
    pub listen_port: u16,
}

/// One `LocalForward` entry. Wire form `[bind:]port host:hostport`, e.g.
/// `8080 example.com:80` or `127.0.0.1:8080 example.com:80`.
#[derive(Clone, Debug, PartialEq, Eq)]
pub struct LocalForwardSpec {
    /// Local bind address; `None` ⇒ loopback (`127.0.0.1`).
    pub bind_addr: Option<String>,
    /// Local port to listen on.
    pub listen_port: u16,
    /// Remote destination host (resolved server-side).
    pub remote_host: String,
    /// Remote destination port.
    pub remote_port: u16,
}

/// One `RemoteForward` entry. Wire form `[bind:]port host:hostport`, e.g.
/// `8080 127.0.0.1:8080`.
#[derive(Clone, Debug, PartialEq, Eq)]
pub struct RemoteForwardSpec {
    /// Remote bind address; `None` ⇒ loopback on the server side.
    pub bind_addr: Option<String>,
    /// Remote port the server should bind.
    pub remote_port: u16,
    /// Local destination host (resolved client-side).
    pub local_host: String,
    /// Local destination port.
    pub local_port: u16,
}

/// Per-host options. Every field is `Option`-typed so callers can distinguish
/// "not set" from "set to default" and apply OpenSSH precedence (CLI > file >
/// built-in default) via a `pick(cli, cfg, default)` helper.
#[derive(Default, Clone, Debug, PartialEq, Eq)]
pub struct ClientOptions {
    /// `HostName`: real hostname to connect to (the `Host` block name is just a label).
    pub host_name: Option<String>,
    /// `Port`: TCP port for the SSH session.
    pub port: Option<u16>,
    /// `User`: remote username.
    pub user: Option<String>,
    /// `IdentityFile` (cumulative across matching blocks).
    pub identity_files: Vec<String>,
    /// `CertificateFile` (cumulative across matching blocks) — paths to user
    /// certificates (`*-cert.pub`) to offer, each paired at load time with the
    /// `IdentityFile` private key whose embedded key it certifies.
    pub certificate_files: Vec<String>,
    /// `IdentitiesOnly` (yes/no).
    pub identities_only: Option<bool>,
    /// `StrictHostKeyChecking`.
    pub strict_host_key: Option<StrictMode>,
    /// `UserKnownHostsFile`.
    pub user_known_hosts: Option<String>,
    /// `HashKnownHosts` (yes/no).
    pub hash_known_hosts: Option<bool>,
    /// `LocalForward` entries (cumulative).
    pub local_forwards: Vec<LocalForwardSpec>,
    /// `RemoteForward` entries (cumulative).
    pub remote_forwards: Vec<RemoteForwardSpec>,
    /// `ForwardAgent` (yes/no).
    pub forward_agent: Option<bool>,
    /// `ForwardX11` (yes/no).
    pub forward_x11: Option<bool>,
    /// `ForwardX11Trusted` (yes/no).
    pub forward_x11_trusted: Option<bool>,
    /// `RequestTTY` (yes/no/force/auto).
    pub request_tty: Option<RequestTty>,
    /// `LogLevel`: 0 = QUIET/INFO, 1 = VERBOSE/DEBUG1, 2 = DEBUG2, 3 = DEBUG3.
    pub log_level: Option<u8>,
    /// `Ciphers` — resolved cipher preference list (strict-validated, with
    /// list modifiers already applied). `None` ⇒ built-in default.
    pub ciphers: Option<Vec<String>>,
    /// `MACs` — resolved MAC preference list.
    pub macs: Option<Vec<String>>,
    /// `KexAlgorithms` — resolved key-exchange preference list (no markers).
    pub kex_algorithms: Option<Vec<String>>,
    /// `HostKeyAlgorithms` — resolved server host-key preference list.
    pub host_key_algorithms: Option<Vec<String>>,
    /// `PubkeyAcceptedAlgorithms` — resolved publickey-auth signature list.
    pub pubkey_accepted_algorithms: Option<Vec<String>>,
    /// `CASignatureAlgorithms` — resolved set of signature algorithms accepted
    /// from a CA when verifying a host certificate. `None` ⇒ built-in default
    /// ([`super::algos::CA_SIGNATURE_DEFAULTS`]).
    pub ca_signature_algorithms: Option<Vec<String>>,
    /// `ProxyCommand` — shell command (with `%h`/`%p`/`%r`/`%%` tokens
    /// un-expanded) to spawn and use as the connection transport. The
    /// literal `none` clears it back to `None`.
    pub proxy_command: Option<String>,
    /// `ProxyJump` — comma-separated `[user@]host[:port]` jump-host chain
    /// to tunnel the connection through. The literal `none` clears it.
    /// Takes precedence over [`Self::proxy_command`] when both are set.
    pub proxy_jump: Option<String>,
    /// `Compression` (yes/no). `Some(true)` advertises
    /// `zlib@openssh.com` ahead of `none`. Requires the `compress`
    /// feature at honoring time.
    pub compression: Option<bool>,
    /// `SetEnv` — literal `NAME=VALUE` pairs to send via `env` requests
    /// (cumulative across matching blocks; later duplicates of a name are
    /// dropped at honoring time per first-wins).
    pub set_env: Vec<(String, String)>,
    /// `SendEnv` — environment-variable name patterns; matching local env
    /// vars are forwarded via `env` requests (cumulative).
    pub send_env: Vec<String>,
    /// `ConnectTimeout` — TCP connect timeout in seconds. `0` is rejected.
    pub connect_timeout: Option<u32>,
    /// `ServerAliveInterval` — seconds between keepalive probes when the
    /// connection is otherwise idle. `0` (or unset) ⇒ disabled.
    pub server_alive_interval: Option<u32>,
    /// `ServerAliveCountMax` — number of unanswered keepalives tolerated
    /// before the connection is torn down (default 3 at honoring time).
    pub server_alive_count_max: Option<u32>,
    /// `TCPKeepAlive` (yes/no) — toggles SO_KEEPALIVE on the socket.
    pub tcp_keep_alive: Option<bool>,
    /// `AddKeysToAgent` — `Some(true)`/`Some(false)`. `confirm`/`ask` are
    /// rejected at parse time (Unsupported).
    pub add_keys_to_agent: Option<bool>,
    /// `PreferredAuthentications` — ordered, comma-separated auth-method
    /// list. Only `publickey`/`password`/`keyboard-interactive`/`none`
    /// are accepted; a list naming none of the implementable methods is
    /// rejected at parse time.
    pub preferred_authentications: Option<Vec<String>>,
    /// `PubkeyAuthentication` (yes/no) — gates publickey credentials.
    pub pubkey_authentication: Option<bool>,
    /// `NumberOfPasswordPrompts` — cap on interactive password attempts
    /// (default 3). `0` disables password auth.
    pub number_of_password_prompts: Option<u32>,
    /// `BatchMode` (yes/no) — never prompt; treat `ask` strict policy as
    /// `yes` and disable password auth.
    pub batch_mode: Option<bool>,
    /// `ExitOnForwardFailure` (yes/no) — abort the connection if any
    /// requested forward fails to bind / be granted.
    pub exit_on_forward_failure: Option<bool>,
    /// `ClearAllForwardings` (yes/no) — discard all local/remote/dynamic
    /// forwards collected so far before connecting.
    pub clear_all_forwardings: Option<bool>,
    /// `DynamicForward` entries — SOCKS proxy listeners (cumulative).
    pub dynamic_forwards: Vec<DynamicForwardSpec>,
    /// `GatewayPorts` — bind-address policy for `-L`/`-D` listeners.
    pub gateway_ports: Option<GatewayPorts>,
    /// `AddressFamily` — restrict resolved addresses to a family.
    pub address_family: Option<AddressFamily>,
    /// `BindAddress` — local source address to bind before connecting.
    pub bind_address: Option<String>,
    /// `IdentityAgent` — agent-socket override (or `none`).
    pub identity_agent: Option<IdentityAgent>,
    /// `ControlMaster` — connection-multiplexing role (no/yes/auto).
    pub control_master: Option<ControlMaster>,
    /// `ControlPath` — Unix-domain control-socket path with `%`-token and
    /// `~` expansion deferred to the honoring site. The literal `none`
    /// (case-insensitive) is stored as `None` to disable multiplexing.
    pub control_path: Option<String>,
    /// `ControlPersist` — how long the master lingers after its foreground
    /// session ends (no/yes/`<N>[smh]`).
    pub control_persist: Option<ControlPersist>,
    /// `ObscureKeystrokeTiming` — keystroke-timing obfuscation for
    /// interactive sessions (`yes`/`no`/`interval:<spec>`). Unset ⇒ honoring
    /// site applies the OpenSSH default (`yes` at 20 ms).
    pub obscure_keystroke_timing: Option<ObscureKeystrokeTiming>,
}

/// One block in a parsed `ssh_config` — either a `Host` block or a `Match`
/// block. Pre-block lines go into an implicit `Host *` block at index 0.
#[derive(Clone, Debug)]
pub(crate) enum Block {
    Host {
        patterns: Vec<HostPattern>,
        opts: ClientOptions,
    },
    Match {
        conditions: Vec<MatchCondition>,
        opts: ClientOptions,
    },
}

impl Block {
    fn opts(&self) -> &ClientOptions {
        match self {
            Block::Host { opts, .. } | Block::Match { opts, .. } => opts,
        }
    }
    fn opts_mut(&mut self) -> &mut ClientOptions {
        match self {
            Block::Host { opts, .. } | Block::Match { opts, .. } => opts,
        }
    }
}

/// A parsed `ssh_config(5)` file.
///
/// Use [`SshClientConfig::parse`] to construct one from text, then
/// [`SshClientConfig::lookup`] (or [`SshClientConfig::lookup_with`] for full
/// `Match` evaluation) to flatten the matching blocks for a target host.
/// Pre-`Host` lines form an implicit "global" block applied to every host
/// (OpenSSH's documented behaviour).
#[derive(Clone, Debug, Default)]
pub struct SshClientConfig {
    pub(crate) blocks: Vec<Block>,
    /// Whether `Match exec` criteria are allowed to execute. Default `false`
    /// (deny). Toggle with [`Self::enable_match_exec`].
    enable_match_exec: bool,
}

impl SshClientConfig {
    /// Parse `src` (the contents of a `ssh_config` file) into an
    /// [`SshClientConfig`]. `Match exec` evaluation is **off** by default;
    /// see [`Self::enable_match_exec`].
    ///
    /// `Include` directives are not resolved by this entry point because
    /// inline parsing has no filesystem context to anchor relative paths to.
    /// Use [`Self::load`] (or [`Self::load_with_base`]) to parse a file with
    /// Include support.
    pub fn parse(src: &str) -> Result<Self, ConfigError> {
        let lines = tokenize(src)?;
        let blocks = parse_blocks(lines)?;
        Ok(SshClientConfig {
            blocks,
            enable_match_exec: false,
        })
    }

    /// Read `path` from disk and parse it, resolving `Include` directives
    /// recursively. Relative paths inside `Include` are anchored to the
    /// directory of the file containing the directive; `~` expands to
    /// `$HOME`; `*` / `?` globs are expanded against the filesystem.
    /// Recursion is capped at [`super::include::MAX_INCLUDE_DEPTH`] hops.
    #[cfg(feature = "std")]
    pub fn load<P: AsRef<std::path::Path>>(path: P) -> Result<Self, ConfigError> {
        let lines = super::include::tokenize_file_with_includes(path.as_ref(), 0)?;
        let blocks = parse_blocks(lines)?;
        Ok(SshClientConfig {
            blocks,
            enable_match_exec: false,
        })
    }

    /// Like [`Self::load`] but parses an in-memory `src` while still
    /// honouring `Include` directives relative to `base_dir`. Useful when
    /// the config has been pre-read (e.g. from a memfd) but you still want
    /// Include semantics anchored at a known directory.
    #[cfg(feature = "std")]
    pub fn load_with_base<P: AsRef<std::path::Path>>(
        src: &str,
        base_dir: P,
    ) -> Result<Self, ConfigError> {
        let lines = tokenize(src)?;
        let expanded = super::include::expand_includes(lines, base_dir.as_ref(), 0)?;
        let blocks = parse_blocks(expanded)?;
        Ok(SshClientConfig {
            blocks,
            enable_match_exec: false,
        })
    }

    /// Append every block of `other` after this config's own, preserving
    /// source order.
    ///
    /// Used to layer a lower-precedence config (e.g. the system-wide
    /// `/etc/ssh/ssh_config`) beneath a higher-precedence one (the user's
    /// `~/.ssh/config`). Because [`lookup`](Self::lookup) is first-match-wins
    /// for scalars, `self`'s blocks keep winning while `other` still
    /// contributes to the cumulative list fields — the same result as
    /// concatenating the two files' text, but with each file's `Include`
    /// directives already resolved relative to its own directory. Both
    /// implicit `Host *` globals survive; `self`'s comes first, so it wins
    /// scalar options.
    pub fn append(&mut self, other: SshClientConfig) {
        self.blocks.extend(other.blocks);
    }

    /// Permit `Match exec <cmd>` criteria to run `/bin/sh -c <cmd>` during
    /// lookup. Off by default because evaluating arbitrary shell commands
    /// during config resolution is a confused-deputy hazard: a config loaded
    /// from an untrusted location could trigger arbitrary commands at the
    /// privilege level of whoever called `lookup`. Callers that fully trust
    /// the config source (e.g. a CLI tool loading the local user's
    /// `~/.ssh/config`) can opt in.
    pub fn enable_match_exec(mut self, allow: bool) -> Self {
        self.enable_match_exec = allow;
        self
    }

    /// `true` iff `Match exec` is currently permitted on this config.
    pub fn is_match_exec_enabled(&self) -> bool {
        self.enable_match_exec
    }

    /// Resolve the effective options for `host`, walking every matching
    /// block in source order with OpenSSH **first-match-wins** semantics for
    /// scalars and **concatenation** for cumulative list fields
    /// (`IdentityFile`, `LocalForward`, `RemoteForward`).
    ///
    /// `Match` blocks that need a username (`Match user …` / `Match localuser
    /// …`) will not match through this entry point — they require fields the
    /// bare `host`-only API doesn't carry. Use [`Self::lookup_with`] when you
    /// have that context.
    pub fn lookup(&self, host: &str) -> ClientOptions {
        self.lookup_with(MatchContext {
            host,
            original_host: None,
            user: None,
            local_user: None,
            ..MatchContext::default()
        })
    }

    /// Like [`Self::lookup`] but supplies a full [`MatchContext`] so `Match`
    /// blocks with `user` / `localuser` / `originalhost` criteria can match.
    pub fn lookup_with(&self, ctx: MatchContext<'_>) -> ClientOptions {
        let policy = if self.enable_match_exec {
            ExecPolicy::Allow
        } else {
            ExecPolicy::Deny
        };
        let mut out = ClientOptions::default();
        for block in &self.blocks {
            let matches = match block {
                Block::Host { patterns, .. } => host_matches(patterns, ctx.host),
                Block::Match { conditions, .. } => all_match(conditions, &ctx, policy),
            };
            if matches {
                merge_into(&mut out, block.opts());
            }
        }
        out
    }
}

/// Walk the tokenised stream and split it into [`Block`]s. Lines outside any
/// explicit `Host` / `Match` block accumulate into the implicit `Host *`
/// block at index 0.
pub(crate) fn parse_blocks(lines: Vec<ParsedLine>) -> Result<Vec<Block>, ConfigError> {
    let mut blocks: Vec<Block> = vec![Block::Host {
        patterns: vec![HostPattern::Any],
        opts: ClientOptions::default(),
    }];
    for line in lines {
        match line.keyword.as_str() {
            "host" => {
                if line.args.is_empty() {
                    return Err(ConfigError::BadValue {
                        line: line.line_no,
                        keyword: "host".to_string(),
                        msg: "Host requires at least one pattern".into(),
                    });
                }
                blocks.push(Block::Host {
                    patterns: HostPattern::parse_all(&line.args),
                    opts: ClientOptions::default(),
                });
            }
            "match" => {
                let conditions = parse_match_line(&line.args, line.line_no)?;
                blocks.push(Block::Match {
                    conditions,
                    opts: ClientOptions::default(),
                });
            }
            "include" => {
                // The Include-expansion pass runs before us when the caller
                // uses SshClientConfig::load* (the std-only entry points). If
                // we see an Include here, the user reached us via
                // SshClientConfig::parse(&str), which has no filesystem
                // context — refuse rather than silently drop.
                return Err(ConfigError::Unsupported {
                    line: line.line_no,
                    msg: "Include requires file-based loading; use SshClientConfig::load() instead"
                        .into(),
                });
            }
            _ => {
                let current = blocks.last_mut().expect("global block always present");
                apply_keyword(current.opts_mut(), &line)?;
            }
        }
    }
    Ok(blocks)
}

/// Apply one parsed line to the in-progress [`ClientOptions`] of the current
/// block.
fn apply_keyword(opts: &mut ClientOptions, line: &ParsedLine) -> Result<(), ConfigError> {
    let kw = line.keyword.as_str();
    let args = &line.args;
    match kw {
        "hostname" => {
            opts.host_name = Some(one_arg(line)?);
        }
        "port" => {
            opts.port = Some(parse_u16(line)?);
        }
        "user" => {
            opts.user = Some(one_arg(line)?);
        }
        "identityfile" => {
            opts.identity_files.push(one_arg(line)?);
        }
        "certificatefile" => {
            opts.certificate_files.push(one_arg(line)?);
        }
        "identitiesonly" => {
            opts.identities_only = Some(parse_yes_no(line)?);
        }
        "stricthostkeychecking" => {
            opts.strict_host_key = Some(parse_strict(line)?);
        }
        "userknownhostsfile" => {
            opts.user_known_hosts = Some(one_arg(line)?);
        }
        "hashknownhosts" => {
            opts.hash_known_hosts = Some(parse_yes_no(line)?);
        }
        "localforward" => {
            opts.local_forwards.push(parse_local_forward(line)?);
        }
        "remoteforward" => {
            opts.remote_forwards.push(parse_remote_forward(line)?);
        }
        "forwardagent" => {
            opts.forward_agent = Some(parse_yes_no(line)?);
        }
        "forwardx11" => {
            opts.forward_x11 = Some(parse_yes_no(line)?);
        }
        "forwardx11trusted" => {
            opts.forward_x11_trusted = Some(parse_yes_no(line)?);
        }
        "requesttty" => {
            opts.request_tty = Some(parse_request_tty(line)?);
        }
        "loglevel" => {
            opts.log_level = Some(parse_log_level(line)?);
        }
        "ciphers" => {
            opts.ciphers = Some(resolve_algo_list(
                AlgoCategory::Cipher,
                args,
                line.line_no,
                "Ciphers",
            )?);
        }
        "macs" => {
            opts.macs = Some(resolve_algo_list(
                AlgoCategory::Mac,
                args,
                line.line_no,
                "MACs",
            )?);
        }
        "kexalgorithms" => {
            opts.kex_algorithms = Some(resolve_algo_list(
                AlgoCategory::Kex,
                args,
                line.line_no,
                "KexAlgorithms",
            )?);
        }
        "hostkeyalgorithms" => {
            opts.host_key_algorithms = Some(resolve_algo_list(
                AlgoCategory::HostKey,
                args,
                line.line_no,
                "HostKeyAlgorithms",
            )?);
        }
        "pubkeyacceptedalgorithms" | "pubkeyacceptedkeytypes" => {
            opts.pubkey_accepted_algorithms = Some(resolve_algo_list(
                AlgoCategory::PubkeyAccepted,
                args,
                line.line_no,
                "PubkeyAcceptedAlgorithms",
            )?);
        }
        "proxycommand" => {
            // The whole rest of the line is the command. The literal `none`
            // (case-insensitive) disables any inherited ProxyCommand.
            if args.is_empty() {
                return Err(ConfigError::BadValue {
                    line: line.line_no,
                    keyword: line.keyword.clone(),
                    msg: "ProxyCommand requires a command (or 'none')".into(),
                });
            }
            if args.len() == 1 && args[0].eq_ignore_ascii_case("none") {
                opts.proxy_command = None;
            } else {
                opts.proxy_command = Some(args.join(" "));
            }
        }
        "proxyjump" => {
            let v = one_arg(line)?;
            if v.eq_ignore_ascii_case("none") {
                opts.proxy_jump = None;
            } else {
                opts.proxy_jump = Some(v);
            }
        }
        "compression" => {
            let on = parse_yes_no(line)?;
            // `Compression yes` requires the `compress` feature: without it
            // the codec has no zlib implementation, so honouring the keyword
            // is impossible. Reject at parse time rather than silently
            // advertising `none` (strict mode — no parse-and-ignore).
            if on && !cfg!(feature = "compress") {
                return Err(ConfigError::Unsupported {
                    line: line.line_no,
                    msg: "Compression yes requires the `compress` feature, which is not \
                          compiled in"
                        .into(),
                });
            }
            opts.compression = Some(on);
        }
        "setenv" => {
            // OpenSSH accepts one or more NAME=VALUE tokens on a SetEnv line.
            if args.is_empty() {
                return Err(ConfigError::BadValue {
                    line: line.line_no,
                    keyword: line.keyword.clone(),
                    msg: "SetEnv requires at least one NAME=VALUE".into(),
                });
            }
            for tok in args {
                let (name, value) = tok.split_once('=').ok_or_else(|| ConfigError::BadValue {
                    line: line.line_no,
                    keyword: line.keyword.clone(),
                    msg: format!("expected NAME=VALUE, got {tok:?}"),
                })?;
                if name.is_empty() {
                    return Err(ConfigError::BadValue {
                        line: line.line_no,
                        keyword: line.keyword.clone(),
                        msg: format!("empty variable name in {tok:?}"),
                    });
                }
                opts.set_env.push((name.to_string(), value.to_string()));
            }
        }
        "sendenv" => {
            if args.is_empty() {
                return Err(ConfigError::BadValue {
                    line: line.line_no,
                    keyword: line.keyword.clone(),
                    msg: "SendEnv requires at least one pattern".into(),
                });
            }
            for pat in args {
                opts.send_env.push(pat.clone());
            }
        }
        "connecttimeout" => {
            let secs = parse_u32(line)?;
            if secs == 0 {
                return Err(ConfigError::BadValue {
                    line: line.line_no,
                    keyword: line.keyword.clone(),
                    msg: "ConnectTimeout must be a positive number of seconds".into(),
                });
            }
            opts.connect_timeout = Some(secs);
        }
        "serveraliveinterval" => {
            opts.server_alive_interval = Some(parse_u32(line)?);
        }
        "serveralivecountmax" => {
            opts.server_alive_count_max = Some(parse_u32(line)?);
        }
        "tcpkeepalive" => {
            opts.tcp_keep_alive = Some(parse_yes_no(line)?);
        }
        "addkeystoagent" => {
            // OpenSSH accepts yes/no/confirm/ask. We can honour yes/no
            // (push or don't push the loaded key to the agent); the
            // interactive confirm/ask variants need a UI we don't have,
            // so reject rather than silently downgrade.
            let s = one_arg(line)?.to_ascii_lowercase();
            match s.as_str() {
                "yes" | "true" | "on" => opts.add_keys_to_agent = Some(true),
                "no" | "false" | "off" => opts.add_keys_to_agent = Some(false),
                "confirm" | "ask" => {
                    return Err(ConfigError::Unsupported {
                        line: line.line_no,
                        msg: "AddKeysToAgent confirm/ask requires interactive confirmation, \
                              which is not implemented"
                            .into(),
                    });
                }
                other => {
                    return Err(ConfigError::BadValue {
                        line: line.line_no,
                        keyword: line.keyword.clone(),
                        msg: format!("expected yes/no/confirm/ask, got {other:?}"),
                    });
                }
            }
        }
        "preferredauthentications" => {
            opts.preferred_authentications = Some(parse_preferred_auth(line)?);
        }
        "pubkeyauthentication" => {
            opts.pubkey_authentication = Some(parse_yes_no(line)?);
        }
        "numberofpasswordprompts" => {
            opts.number_of_password_prompts = Some(parse_u32(line)?);
        }
        "batchmode" => {
            opts.batch_mode = Some(parse_yes_no(line)?);
        }
        "exitonforwardfailure" => {
            opts.exit_on_forward_failure = Some(parse_yes_no(line)?);
        }
        "clearallforwardings" => {
            opts.clear_all_forwardings = Some(parse_yes_no(line)?);
        }
        "dynamicforward" => {
            opts.dynamic_forwards.push(parse_dynamic_forward(line)?);
        }
        "gatewayports" => {
            let s = one_arg(line)?.to_ascii_lowercase();
            opts.gateway_ports = Some(match s.as_str() {
                "no" | "false" | "off" => GatewayPorts::No,
                "yes" | "true" | "on" => GatewayPorts::Yes,
                "clientspecified" => GatewayPorts::ClientSpecified,
                other => {
                    return Err(ConfigError::BadValue {
                        line: line.line_no,
                        keyword: line.keyword.clone(),
                        msg: format!("expected no/yes/clientspecified, got {other:?}"),
                    });
                }
            });
        }
        "addressfamily" => {
            let s = one_arg(line)?.to_ascii_lowercase();
            opts.address_family = Some(match s.as_str() {
                "any" => AddressFamily::Any,
                "inet" => AddressFamily::Inet,
                "inet6" => AddressFamily::Inet6,
                other => {
                    return Err(ConfigError::BadValue {
                        line: line.line_no,
                        keyword: line.keyword.clone(),
                        msg: format!("expected any/inet/inet6, got {other:?}"),
                    });
                }
            });
        }
        "bindaddress" => {
            opts.bind_address = Some(one_arg(line)?);
        }
        "identityagent" => {
            let v = one_arg(line)?;
            opts.identity_agent = Some(if v.eq_ignore_ascii_case("none") {
                IdentityAgent::None
            } else {
                IdentityAgent::Path(v)
            });
        }
        "controlmaster" => {
            let s = one_arg(line)?.to_ascii_lowercase();
            opts.control_master = Some(match s.as_str() {
                "no" | "false" | "off" => ControlMaster::No,
                "yes" | "true" | "on" => ControlMaster::Yes,
                "auto" => ControlMaster::Auto,
                // `ask` / `autoask` need an interactive confirmation path
                // we don't have. Reject rather than silently treat as
                // `yes` — the user explicitly asked to be prompted.
                "ask" | "autoask" => {
                    return Err(ConfigError::Unsupported {
                        line: line.line_no,
                        msg: "ControlMaster ask/autoask requires interactive confirmation, \
                              which is not implemented"
                            .into(),
                    });
                }
                other => {
                    return Err(ConfigError::BadValue {
                        line: line.line_no,
                        keyword: line.keyword.clone(),
                        msg: format!("expected no/yes/auto, got {other:?}"),
                    });
                }
            });
        }
        "controlpath" => {
            // The whole rest of the line (after token re-join) is the path;
            // `%`-token and `~` expansion happen at the honoring site.
            // `none` (case-insensitive) disables multiplexing.
            let v = one_arg(line)?;
            if v.eq_ignore_ascii_case("none") {
                opts.control_path = None;
            } else {
                opts.control_path = Some(v);
            }
        }
        "controlpersist" => {
            opts.control_persist = Some(parse_control_persist(line)?);
        }
        "obscurekeystroketiming" => {
            opts.obscure_keystroke_timing = Some(parse_obscure_keystroke_timing(line)?);
        }
        "casignaturealgorithms" => {
            opts.ca_signature_algorithms = Some(resolve_algo_list(
                AlgoCategory::CaSignature,
                args,
                line.line_no,
                &line.keyword,
            )?);
        }
        _ => {
            return Err(ConfigError::UnknownKeyword {
                line: line.line_no,
                keyword: kw.to_string(),
            });
        }
    }
    let _ = args;
    Ok(())
}

/// First-match-wins merge of `src` over `dst`. Scalars only overwrite if
/// `dst` had `None`; list fields concatenate.
fn merge_into(dst: &mut ClientOptions, src: &ClientOptions) {
    macro_rules! take_scalar {
        ($field:ident) => {
            if dst.$field.is_none() {
                dst.$field = src.$field.clone();
            }
        };
    }
    take_scalar!(host_name);
    take_scalar!(port);
    take_scalar!(user);
    take_scalar!(identities_only);
    take_scalar!(strict_host_key);
    take_scalar!(user_known_hosts);
    take_scalar!(hash_known_hosts);
    take_scalar!(forward_agent);
    take_scalar!(forward_x11);
    take_scalar!(forward_x11_trusted);
    take_scalar!(request_tty);
    take_scalar!(log_level);
    // Algorithm overrides are first-match-wins scalars: the whole resolved
    // list from the earliest matching block wins (OpenSSH semantics — a
    // later block's Ciphers does not append to an earlier block's).
    take_scalar!(ciphers);
    take_scalar!(macs);
    take_scalar!(kex_algorithms);
    take_scalar!(host_key_algorithms);
    take_scalar!(pubkey_accepted_algorithms);
    take_scalar!(ca_signature_algorithms);
    take_scalar!(proxy_command);
    take_scalar!(proxy_jump);
    take_scalar!(compression);
    take_scalar!(connect_timeout);
    take_scalar!(server_alive_interval);
    take_scalar!(server_alive_count_max);
    take_scalar!(tcp_keep_alive);
    take_scalar!(add_keys_to_agent);
    take_scalar!(preferred_authentications);
    take_scalar!(pubkey_authentication);
    take_scalar!(number_of_password_prompts);
    take_scalar!(batch_mode);
    take_scalar!(exit_on_forward_failure);
    take_scalar!(clear_all_forwardings);
    take_scalar!(gateway_ports);
    take_scalar!(address_family);
    take_scalar!(bind_address);
    take_scalar!(identity_agent);
    take_scalar!(control_master);
    take_scalar!(control_path);
    take_scalar!(control_persist);
    take_scalar!(obscure_keystroke_timing);
    dst.identity_files
        .extend(src.identity_files.iter().cloned());
    dst.certificate_files
        .extend(src.certificate_files.iter().cloned());
    dst.local_forwards
        .extend(src.local_forwards.iter().cloned());
    dst.remote_forwards
        .extend(src.remote_forwards.iter().cloned());
    dst.dynamic_forwards
        .extend(src.dynamic_forwards.iter().cloned());
    dst.set_env.extend(src.set_env.iter().cloned());
    dst.send_env.extend(src.send_env.iter().cloned());
}

fn one_arg(line: &ParsedLine) -> Result<String, ConfigError> {
    if line.args.len() != 1 {
        return Err(ConfigError::BadValue {
            line: line.line_no,
            keyword: line.keyword.clone(),
            msg: format!("expected 1 value, got {}", line.args.len()),
        });
    }
    Ok(line.args[0].clone())
}

fn parse_u16(line: &ParsedLine) -> Result<u16, ConfigError> {
    let s = one_arg(line)?;
    s.parse::<u16>().map_err(|_| ConfigError::BadValue {
        line: line.line_no,
        keyword: line.keyword.clone(),
        msg: format!("expected a port number, got {s:?}"),
    })
}

fn parse_u32(line: &ParsedLine) -> Result<u32, ConfigError> {
    let s = one_arg(line)?;
    s.parse::<u32>().map_err(|_| ConfigError::BadValue {
        line: line.line_no,
        keyword: line.keyword.clone(),
        msg: format!("expected a non-negative integer, got {s:?}"),
    })
}

/// Parse a `PreferredAuthentications` list. OpenSSH takes a comma-separated
/// list of method names. We recognise the standard set but only honour the
/// ones the client implements; a list that names *none* of the
/// implementable methods is rejected so the directive can never look like it
/// took effect while silently leaving no usable method.
fn parse_preferred_auth(line: &ParsedLine) -> Result<Vec<String>, ConfigError> {
    // The list may arrive as one comma-joined token or several whitespace-
    // separated tokens; normalise both.
    let mut methods: Vec<String> = Vec::new();
    for tok in &line.args {
        for m in tok.split(',') {
            let m = m.trim();
            if !m.is_empty() {
                methods.push(m.to_ascii_lowercase());
            }
        }
    }
    if methods.is_empty() {
        return Err(ConfigError::BadValue {
            line: line.line_no,
            keyword: line.keyword.clone(),
            msg: "PreferredAuthentications requires at least one method".into(),
        });
    }
    // Known OpenSSH method names. `gssapi-with-mic` / `hostbased` are
    // understood-but-unimplemented: we tolerate them in the list (so a
    // shared config doesn't break) but they contribute nothing usable.
    const KNOWN: &[&str] = &[
        "publickey",
        "password",
        "keyboard-interactive",
        "none",
        "gssapi-with-mic",
        "hostbased",
    ];
    const IMPLEMENTED: &[&str] = &["publickey", "password", "none"];
    for m in &methods {
        if !KNOWN.contains(&m.as_str()) {
            return Err(ConfigError::BadValue {
                line: line.line_no,
                keyword: line.keyword.clone(),
                msg: format!("unknown authentication method {m:?}"),
            });
        }
    }
    if !methods.iter().any(|m| IMPLEMENTED.contains(&m.as_str())) {
        return Err(ConfigError::Unsupported {
            line: line.line_no,
            msg: "PreferredAuthentications names only methods this client does not \
                  implement (publickey/password are the supported methods)"
                .into(),
        });
    }
    Ok(methods)
}

/// Parse a `DynamicForward` argument: a single `[bind:]port` token.
fn parse_dynamic_forward(line: &ParsedLine) -> Result<DynamicForwardSpec, ConfigError> {
    if line.args.len() != 1 {
        return Err(ConfigError::BadValue {
            line: line.line_no,
            keyword: line.keyword.clone(),
            msg: format!("expected 1 token ([bind:]port), got {}", line.args.len()),
        });
    }
    let (bind_addr, listen_port) = split_bind_port(&line.args[0], line)?;
    Ok(DynamicForwardSpec {
        bind_addr,
        listen_port,
    })
}

/// Parse a `ControlPersist` value: `yes` / `no` / `<N>` / `<N>[smh]`.
///
/// A bare integer is seconds. A trailing `s`/`m`/`h` suffix scales to
/// seconds (`m` ⇒ ×60, `h` ⇒ ×3600). A literal `0` means "no persist"
/// (≡ `no`), matching OpenSSH. Overflow on the multiply is rejected.
fn parse_control_persist(line: &ParsedLine) -> Result<ControlPersist, ConfigError> {
    let s = one_arg(line)?.to_ascii_lowercase();
    match s.as_str() {
        "no" | "false" | "off" => return Ok(ControlPersist::No),
        "yes" | "true" | "on" => return Ok(ControlPersist::Yes),
        _ => {}
    }
    let bad = |msg: String| ConfigError::BadValue {
        line: line.line_no,
        keyword: line.keyword.clone(),
        msg,
    };
    let (digits, scale): (&str, u64) = match s.as_bytes().last() {
        Some(b's') => (&s[..s.len() - 1], 1),
        Some(b'm') => (&s[..s.len() - 1], 60),
        Some(b'h') => (&s[..s.len() - 1], 3600),
        _ => (s.as_str(), 1),
    };
    if digits.is_empty() {
        return Err(bad(format!("expected yes/no/<N>[smh], got {s:?}")));
    }
    let n: u64 = digits
        .parse()
        .map_err(|_| bad(format!("expected yes/no/<N>[smh], got {s:?}")))?;
    let secs = n
        .checked_mul(scale)
        .ok_or_else(|| bad("ControlPersist duration overflows".into()))?;
    if secs == 0 {
        Ok(ControlPersist::No)
    } else {
        Ok(ControlPersist::Seconds(secs))
    }
}

/// Parse an `ObscureKeystrokeTiming` value: `yes` / `no` / `interval:<spec>`.
///
/// `yes` ⇒ on at the OpenSSH default (20 ms). `no` ⇒ off. `interval:<spec>`
/// ⇒ on with `<spec>` resolved to milliseconds: either a bare integer
/// (milliseconds, `interval:80`) or an OpenSSH time value with a unit suffix
/// (`interval:1s`, `interval:500ms`). A zero interval is rejected. STRICT:
/// anything malformed is a [`ConfigError::BadValue`].
fn parse_obscure_keystroke_timing(
    line: &ParsedLine,
) -> Result<ObscureKeystrokeTiming, ConfigError> {
    let raw = one_arg(line)?;
    let s = raw.to_ascii_lowercase();
    let bad = |msg: String| ConfigError::BadValue {
        line: line.line_no,
        keyword: line.keyword.clone(),
        msg,
    };
    match s.as_str() {
        "no" | "false" | "off" => return Ok(ObscureKeystrokeTiming::Off),
        "yes" | "true" | "on" => return Ok(ObscureKeystrokeTiming::default_on()),
        _ => {}
    }
    let Some(spec) = s.strip_prefix("interval:") else {
        return Err(bad(format!("expected yes/no/interval:<spec>, got {raw:?}")));
    };
    if spec.is_empty() {
        return Err(bad("interval: requires a value".into()));
    }
    // Resolve <spec> to milliseconds. Bare integer ⇒ ms. `ms` suffix ⇒ ms.
    // `s`/`m`/`h` suffixes ⇒ seconds/minutes/hours scaled to ms.
    let (digits, scale_ms): (&str, u64) = if let Some(d) = spec.strip_suffix("ms") {
        (d, 1)
    } else if let Some(d) = spec.strip_suffix('s') {
        (d, 1000)
    } else if let Some(d) = spec.strip_suffix('m') {
        (d, 60_000)
    } else if let Some(d) = spec.strip_suffix('h') {
        (d, 3_600_000)
    } else {
        (spec, 1)
    };
    if digits.is_empty() || !digits.bytes().all(|b| b.is_ascii_digit()) {
        return Err(bad(format!(
            "interval: expected <ms> or <N>[ms|s|m|h], got {spec:?}"
        )));
    }
    let n: u64 = digits
        .parse()
        .map_err(|_| bad(format!("interval: invalid number {spec:?}")))?;
    let ms = n
        .checked_mul(scale_ms)
        .ok_or_else(|| bad("interval: duration overflows".into()))?;
    if ms == 0 {
        return Err(bad("interval: must be greater than zero".into()));
    }
    let interval_ms = u32::try_from(ms).map_err(|_| bad("interval: too large".into()))?;
    Ok(ObscureKeystrokeTiming::On { interval_ms })
}

fn parse_yes_no(line: &ParsedLine) -> Result<bool, ConfigError> {
    let s = one_arg(line)?.to_ascii_lowercase();
    match s.as_str() {
        "yes" | "true" | "on" => Ok(true),
        "no" | "false" | "off" => Ok(false),
        _ => Err(ConfigError::BadValue {
            line: line.line_no,
            keyword: line.keyword.clone(),
            msg: format!("expected yes/no, got {s:?}"),
        }),
    }
}

fn parse_strict(line: &ParsedLine) -> Result<StrictMode, ConfigError> {
    let s = one_arg(line)?.to_ascii_lowercase();
    match s.as_str() {
        "yes" => Ok(StrictMode::Yes),
        "no" | "off" => Ok(StrictMode::No),
        "accept-new" => Ok(StrictMode::AcceptNew),
        "ask" => Ok(StrictMode::Ask),
        _ => Err(ConfigError::BadValue {
            line: line.line_no,
            keyword: line.keyword.clone(),
            msg: format!("expected yes/no/accept-new/ask/off, got {s:?}"),
        }),
    }
}

fn parse_request_tty(line: &ParsedLine) -> Result<RequestTty, ConfigError> {
    let s = one_arg(line)?.to_ascii_lowercase();
    match s.as_str() {
        "no" => Ok(RequestTty::No),
        "yes" => Ok(RequestTty::Yes),
        "force" => Ok(RequestTty::Force),
        "auto" => Ok(RequestTty::Auto),
        _ => Err(ConfigError::BadValue {
            line: line.line_no,
            keyword: line.keyword.clone(),
            msg: format!("expected no/yes/force/auto, got {s:?}"),
        }),
    }
}

fn parse_log_level(line: &ParsedLine) -> Result<u8, ConfigError> {
    let s = one_arg(line)?.to_ascii_uppercase();
    match s.as_str() {
        "QUIET" | "FATAL" | "ERROR" | "INFO" => Ok(0),
        "VERBOSE" | "DEBUG" | "DEBUG1" => Ok(1),
        "DEBUG2" => Ok(2),
        "DEBUG3" => Ok(3),
        _ => Err(ConfigError::BadValue {
            line: line.line_no,
            keyword: line.keyword.clone(),
            msg: format!("expected QUIET..DEBUG3, got {s:?}"),
        }),
    }
}

/// Parse a `LocalForward` argument list. OpenSSH accepts two whitespace-
/// separated tokens: `[bind:]port host:hostport`.
fn parse_local_forward(line: &ParsedLine) -> Result<LocalForwardSpec, ConfigError> {
    if line.args.len() != 2 {
        return Err(ConfigError::BadValue {
            line: line.line_no,
            keyword: line.keyword.clone(),
            msg: format!("expected 2 tokens, got {}", line.args.len()),
        });
    }
    let (bind_addr, listen_port) = split_bind_port(&line.args[0], line)?;
    let (remote_host, remote_port) = split_host_port(&line.args[1], line)?;
    Ok(LocalForwardSpec {
        bind_addr,
        listen_port,
        remote_host,
        remote_port,
    })
}

/// Parse a `RemoteForward` argument list. Same shape as `LocalForward`.
fn parse_remote_forward(line: &ParsedLine) -> Result<RemoteForwardSpec, ConfigError> {
    if line.args.len() != 2 {
        return Err(ConfigError::BadValue {
            line: line.line_no,
            keyword: line.keyword.clone(),
            msg: format!("expected 2 tokens, got {}", line.args.len()),
        });
    }
    let (bind_addr, remote_port) = split_bind_port(&line.args[0], line)?;
    let (local_host, local_port) = split_host_port(&line.args[1], line)?;
    Ok(RemoteForwardSpec {
        bind_addr,
        remote_port,
        local_host,
        local_port,
    })
}

/// `[bind:]port` → `(Some("bind"), port)` or `(None, port)`. IPv6 literal
/// addresses must be bracketed (`[::1]:port`).
fn split_bind_port(s: &str, line: &ParsedLine) -> Result<(Option<String>, u16), ConfigError> {
    if let Some(rest) = s.strip_prefix('[') {
        // `[addr]:port`
        if let Some((addr, port)) = rest.split_once("]:") {
            let port = port.parse::<u16>().map_err(|_| ConfigError::BadValue {
                line: line.line_no,
                keyword: line.keyword.clone(),
                msg: format!("bad port in {s:?}"),
            })?;
            return Ok((Some(addr.to_string()), port));
        }
        return Err(ConfigError::BadValue {
            line: line.line_no,
            keyword: line.keyword.clone(),
            msg: format!("malformed bracketed bind:port {s:?}"),
        });
    }
    match s.rsplit_once(':') {
        Some((addr, port)) => {
            let port = port.parse::<u16>().map_err(|_| ConfigError::BadValue {
                line: line.line_no,
                keyword: line.keyword.clone(),
                msg: format!("bad port in {s:?}"),
            })?;
            Ok((Some(addr.to_string()), port))
        }
        None => {
            let port = s.parse::<u16>().map_err(|_| ConfigError::BadValue {
                line: line.line_no,
                keyword: line.keyword.clone(),
                msg: format!("expected port or addr:port, got {s:?}"),
            })?;
            Ok((None, port))
        }
    }
}

/// `host:port` or `[host]:port`.
fn split_host_port(s: &str, line: &ParsedLine) -> Result<(String, u16), ConfigError> {
    if let Some(rest) = s.strip_prefix('[') {
        if let Some((addr, port)) = rest.split_once("]:") {
            let port = port.parse::<u16>().map_err(|_| ConfigError::BadValue {
                line: line.line_no,
                keyword: line.keyword.clone(),
                msg: format!("bad port in {s:?}"),
            })?;
            return Ok((addr.to_string(), port));
        }
        return Err(ConfigError::BadValue {
            line: line.line_no,
            keyword: line.keyword.clone(),
            msg: format!("malformed bracketed host:port {s:?}"),
        });
    }
    match s.rsplit_once(':') {
        Some((host, port)) => {
            let port = port.parse::<u16>().map_err(|_| ConfigError::BadValue {
                line: line.line_no,
                keyword: line.keyword.clone(),
                msg: format!("bad port in {s:?}"),
            })?;
            Ok((host.to_string(), port))
        }
        None => Err(ConfigError::BadValue {
            line: line.line_no,
            keyword: line.keyword.clone(),
            msg: format!("expected host:port, got {s:?}"),
        }),
    }
}

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

    #[test]
    fn parse_minimal() {
        let src = "\
Host gw
  HostName 198.51.100.7
  User admin
  Port 2222
";
        let cfg = SshClientConfig::parse(src).unwrap();
        let eff = cfg.lookup("gw");
        assert_eq!(eff.host_name.as_deref(), Some("198.51.100.7"));
        assert_eq!(eff.port, Some(2222));
        assert_eq!(eff.user.as_deref(), Some("admin"));
    }

    #[test]
    fn algorithm_keywords_parse() {
        let src = "\
Host gw
  Ciphers aes128-ctr,aes256-ctr
  MACs hmac-sha2-256
  KexAlgorithms curve25519-sha256
  HostKeyAlgorithms ssh-ed25519
  PubkeyAcceptedAlgorithms ssh-ed25519,rsa-sha2-512
";
        let cfg = SshClientConfig::parse(src).unwrap();
        let eff = cfg.lookup("gw");
        assert_eq!(
            eff.ciphers.as_deref(),
            Some(&["aes128-ctr".to_string(), "aes256-ctr".to_string()][..])
        );
        assert_eq!(
            eff.macs.as_deref(),
            Some(&["hmac-sha2-256".to_string()][..])
        );
        assert_eq!(
            eff.kex_algorithms.as_deref(),
            Some(&["curve25519-sha256".to_string()][..])
        );
        assert_eq!(
            eff.host_key_algorithms.as_deref(),
            Some(&["ssh-ed25519".to_string()][..])
        );
        assert_eq!(
            eff.pubkey_accepted_algorithms.as_deref(),
            Some(&["ssh-ed25519".to_string(), "rsa-sha2-512".to_string()][..])
        );
    }

    #[test]
    fn host_key_algorithms_plus_ssh_rsa_accepted() {
        // `HostKeyAlgorithms +ssh-rsa` used to be rejected; it now resolves to
        // the defaults plus the legacy SHA-1 name appended (opt-in).
        let src = "Host legacy\n  HostKeyAlgorithms +ssh-rsa\n";
        let cfg = SshClientConfig::parse(src).expect("+ssh-rsa must parse");
        let eff = cfg.lookup("legacy");
        let list = eff
            .host_key_algorithms
            .as_deref()
            .expect("host_key_algorithms set");
        assert!(
            list.iter().any(|n| n == "ssh-rsa"),
            "+ssh-rsa must appear in the resolved list: {list:?}"
        );
        assert!(
            list.iter().any(|n| n == "ssh-ed25519"),
            "defaults must be preserved ahead of the appended legacy name"
        );
    }

    #[test]
    fn host_key_algorithms_bare_ssh_rsa_accepted() {
        // A bare replace naming only ssh-rsa is also accepted (explicit opt-in).
        let src = "Host legacy\n  HostKeyAlgorithms ssh-rsa\n";
        let cfg = SshClientConfig::parse(src).expect("bare ssh-rsa must parse");
        let eff = cfg.lookup("legacy");
        assert_eq!(
            eff.host_key_algorithms.as_deref(),
            Some(&["ssh-rsa".to_string()][..])
        );
    }

    #[test]
    fn pubkey_accepted_ssh_rsa_still_rejected() {
        // The SHA-1 opt-in is HostKey-only; pubkey auth must still reject it.
        let src = "Host legacy\n  PubkeyAcceptedAlgorithms +ssh-rsa\n";
        let err = SshClientConfig::parse(src).unwrap_err();
        assert!(matches!(err, ConfigError::BadValue { .. }));
    }

    #[test]
    fn unknown_cipher_rejected_with_line() {
        let src = "Host gw\n  Ciphers totally-bogus\n";
        let err = SshClientConfig::parse(src).unwrap_err();
        match err {
            ConfigError::BadValue { line, keyword, msg } => {
                assert_eq!(line, 2);
                assert_eq!(keyword, "Ciphers");
                assert!(msg.contains("totally-bogus"));
            }
            other => panic!("expected BadValue, got {other:?}"),
        }
    }

    #[test]
    fn proxy_command_parses() {
        let src = "\
Host gw
  ProxyCommand /usr/bin/nc -X connect -x proxy:3128 %h %p
";
        let cfg = SshClientConfig::parse(src).unwrap();
        let eff = cfg.lookup("gw");
        assert_eq!(
            eff.proxy_command.as_deref(),
            Some("/usr/bin/nc -X connect -x proxy:3128 %h %p")
        );
    }

    #[test]
    fn proxy_command_none_clears() {
        let src = "\
Host gw
  ProxyCommand none
";
        let cfg = SshClientConfig::parse(src).unwrap();
        assert_eq!(cfg.lookup("gw").proxy_command, None);
    }

    #[test]
    fn proxy_command_empty_errors() {
        // `ProxyCommand` with no argument is a config error.
        let src = "ProxyCommand\n";
        let err = SshClientConfig::parse(src).unwrap_err();
        match err {
            ConfigError::BadValue { line, keyword, .. } => {
                assert_eq!(line, 1);
                assert_eq!(keyword, "proxycommand");
            }
            other => panic!("expected BadValue, got {other:?}"),
        }
    }

    #[test]
    fn proxy_jump_parses() {
        let src = "\
Host target
  ProxyJump user@bastion:2222,hop2
";
        let cfg = SshClientConfig::parse(src).unwrap();
        assert_eq!(
            cfg.lookup("target").proxy_jump.as_deref(),
            Some("user@bastion:2222,hop2")
        );
    }

    #[test]
    fn proxy_jump_none_clears() {
        let src = "\
Host target
  ProxyJump none
";
        let cfg = SshClientConfig::parse(src).unwrap();
        assert_eq!(cfg.lookup("target").proxy_jump, None);
    }

    #[test]
    fn casignaturealgorithms_accepted() {
        let src = "Host gw\n  CASignatureAlgorithms ssh-ed25519,rsa-sha2-512\n";
        let cfg = SshClientConfig::parse(src).unwrap();
        let eff = cfg.lookup("gw");
        assert_eq!(
            eff.ca_signature_algorithms.as_deref(),
            Some(["ssh-ed25519".to_string(), "rsa-sha2-512".to_string()].as_slice())
        );
    }

    #[test]
    fn casignaturealgorithms_rejects_plain_ssh_rsa() {
        // Plain SHA-1 ssh-rsa is not a valid CA signature algorithm.
        let src = "Host gw\n  CASignatureAlgorithms ssh-rsa\n";
        let err = SshClientConfig::parse(src).unwrap_err();
        assert!(matches!(err, ConfigError::BadValue { line: 2, .. }));
    }

    #[test]
    fn algorithms_first_match_wins() {
        // First matching block's Ciphers wins; a later block does not append.
        let src = "\
Host gw
  Ciphers aes128-ctr
Host *
  Ciphers aes256-ctr
";
        let cfg = SshClientConfig::parse(src).unwrap();
        let eff = cfg.lookup("gw");
        assert_eq!(
            eff.ciphers.as_deref(),
            Some(&["aes128-ctr".to_string()][..])
        );
    }

    #[test]
    fn global_block_applies() {
        let src = "\
User globaluser
IdentitiesOnly yes
Host gw
  Port 2222
";
        let cfg = SshClientConfig::parse(src).unwrap();
        let eff = cfg.lookup("gw");
        assert_eq!(eff.user.as_deref(), Some("globaluser"));
        assert_eq!(eff.port, Some(2222));
        assert_eq!(eff.identities_only, Some(true));
    }

    #[test]
    fn first_match_wins_for_scalars() {
        // Two matching blocks; the FIRST set wins.
        let src = "\
Host *.example.com
  User firstuser
Host *
  User otheruser
";
        let cfg = SshClientConfig::parse(src).unwrap();
        let eff = cfg.lookup("host.example.com");
        assert_eq!(eff.user.as_deref(), Some("firstuser"));
    }

    #[test]
    fn identity_files_cumulative() {
        let src = "\
Host *
  IdentityFile ~/.ssh/id_a
Host gw
  IdentityFile ~/.ssh/id_b
";
        let cfg = SshClientConfig::parse(src).unwrap();
        let eff = cfg.lookup("gw");
        assert_eq!(eff.identity_files, vec!["~/.ssh/id_a", "~/.ssh/id_b"]);
    }

    #[test]
    fn local_forward_parses() {
        let src = "\
Host gw
  LocalForward 8080 example.com:80
  LocalForward 127.0.0.1:9090 backend:443
";
        let cfg = SshClientConfig::parse(src).unwrap();
        let eff = cfg.lookup("gw");
        assert_eq!(eff.local_forwards.len(), 2);
        assert_eq!(eff.local_forwards[0].bind_addr, None);
        assert_eq!(eff.local_forwards[0].listen_port, 8080);
        assert_eq!(eff.local_forwards[0].remote_host, "example.com");
        assert_eq!(eff.local_forwards[0].remote_port, 80);
        assert_eq!(
            eff.local_forwards[1].bind_addr.as_deref(),
            Some("127.0.0.1")
        );
        assert_eq!(eff.local_forwards[1].listen_port, 9090);
    }

    #[test]
    fn ipv6_bracketed_bind() {
        let src = "\
Host gw
  LocalForward [::1]:8080 example.com:80
";
        let cfg = SshClientConfig::parse(src).unwrap();
        let eff = cfg.lookup("gw");
        assert_eq!(eff.local_forwards[0].bind_addr.as_deref(), Some("::1"));
        assert_eq!(eff.local_forwards[0].listen_port, 8080);
    }

    #[test]
    fn negated_host_excludes() {
        let src = "\
Host *.example.com !secret.example.com
  User foo
";
        let cfg = SshClientConfig::parse(src).unwrap();
        assert_eq!(cfg.lookup("ok.example.com").user.as_deref(), Some("foo"));
        assert_eq!(cfg.lookup("secret.example.com").user, None);
    }

    #[test]
    fn unknown_keyword_errors() {
        let src = "Host gw\n  CompressionLevel 9\n";
        let err = SshClientConfig::parse(src).unwrap_err();
        match err {
            ConfigError::UnknownKeyword { keyword, line } => {
                assert_eq!(keyword, "compressionlevel");
                assert_eq!(line, 2);
            }
            _ => panic!("wrong error: {err:?}"),
        }
    }

    #[test]
    fn strict_host_key_values() {
        for (s, want) in [
            ("yes", StrictMode::Yes),
            ("no", StrictMode::No),
            ("off", StrictMode::No),
            ("accept-new", StrictMode::AcceptNew),
            ("ask", StrictMode::Ask),
        ] {
            let src = format!("StrictHostKeyChecking {s}\n");
            let cfg = SshClientConfig::parse(&src).unwrap();
            assert_eq!(cfg.lookup("anything").strict_host_key, Some(want));
        }
    }

    #[test]
    fn request_tty_values() {
        for (s, want) in [
            ("no", RequestTty::No),
            ("yes", RequestTty::Yes),
            ("force", RequestTty::Force),
            ("auto", RequestTty::Auto),
        ] {
            let src = format!("RequestTTY {s}\n");
            let cfg = SshClientConfig::parse(&src).unwrap();
            assert_eq!(cfg.lookup("anything").request_tty, Some(want));
        }
    }

    #[test]
    fn equals_separator_accepted() {
        let src = "Host gw\n  Port=2222\n";
        let cfg = SshClientConfig::parse(src).unwrap();
        assert_eq!(cfg.lookup("gw").port, Some(2222));
    }

    // ----- W4 modern-keyword tests --------------------------------------

    #[cfg(feature = "compress")]
    #[test]
    fn compression_parses_with_feature() {
        let cfg = SshClientConfig::parse("Compression yes\n").unwrap();
        assert_eq!(cfg.lookup("h").compression, Some(true));
        let cfg = SshClientConfig::parse("Compression no\n").unwrap();
        assert_eq!(cfg.lookup("h").compression, Some(false));
    }

    #[cfg(not(feature = "compress"))]
    #[test]
    fn compression_yes_unsupported_without_feature() {
        // `Compression no` still parses (nothing to honour); `yes` rejects.
        let cfg = SshClientConfig::parse("Compression no\n").unwrap();
        assert_eq!(cfg.lookup("h").compression, Some(false));
        let err = SshClientConfig::parse("Compression yes\n").unwrap_err();
        assert!(matches!(err, ConfigError::Unsupported { .. }));
    }

    #[test]
    fn set_env_parses_multiple() {
        let src = "Host gw\n  SetEnv FOO=bar BAZ=qux\n  SetEnv LANG=C\n";
        let cfg = SshClientConfig::parse(src).unwrap();
        let eff = cfg.lookup("gw");
        assert_eq!(
            eff.set_env,
            vec![
                ("FOO".to_string(), "bar".to_string()),
                ("BAZ".to_string(), "qux".to_string()),
                ("LANG".to_string(), "C".to_string()),
            ]
        );
    }

    #[test]
    fn set_env_rejects_missing_equals() {
        let err = SshClientConfig::parse("SetEnv NOTANENV\n").unwrap_err();
        assert!(matches!(err, ConfigError::BadValue { .. }));
    }

    #[test]
    fn send_env_parses() {
        let src = "Host gw\n  SendEnv LANG LC_*\n  SendEnv TERM\n";
        let cfg = SshClientConfig::parse(src).unwrap();
        assert_eq!(cfg.lookup("gw").send_env, vec!["LANG", "LC_*", "TERM"]);
    }

    #[test]
    fn connect_timeout_parses_and_rejects_zero() {
        let cfg = SshClientConfig::parse("ConnectTimeout 10\n").unwrap();
        assert_eq!(cfg.lookup("h").connect_timeout, Some(10));
        let err = SshClientConfig::parse("ConnectTimeout 0\n").unwrap_err();
        assert!(matches!(err, ConfigError::BadValue { .. }));
    }

    #[test]
    fn server_alive_parses() {
        let src = "ServerAliveInterval 15\nServerAliveCountMax 4\n";
        let cfg = SshClientConfig::parse(src).unwrap();
        let eff = cfg.lookup("h");
        assert_eq!(eff.server_alive_interval, Some(15));
        assert_eq!(eff.server_alive_count_max, Some(4));
    }

    #[test]
    fn tcp_keep_alive_parses() {
        let cfg = SshClientConfig::parse("TCPKeepAlive no\n").unwrap();
        assert_eq!(cfg.lookup("h").tcp_keep_alive, Some(false));
    }

    #[test]
    fn add_keys_to_agent_yes_no() {
        assert_eq!(
            SshClientConfig::parse("AddKeysToAgent yes\n")
                .unwrap()
                .lookup("h")
                .add_keys_to_agent,
            Some(true)
        );
        assert_eq!(
            SshClientConfig::parse("AddKeysToAgent no\n")
                .unwrap()
                .lookup("h")
                .add_keys_to_agent,
            Some(false)
        );
    }

    #[test]
    fn add_keys_to_agent_confirm_unsupported() {
        for v in ["confirm", "ask"] {
            let err = SshClientConfig::parse(&format!("AddKeysToAgent {v}\n")).unwrap_err();
            assert!(
                matches!(err, ConfigError::Unsupported { .. }),
                "expected Unsupported for {v}, got {err:?}"
            );
        }
    }

    #[test]
    fn preferred_authentications_parses_and_orders() {
        let cfg = SshClientConfig::parse("PreferredAuthentications password,publickey\n").unwrap();
        assert_eq!(
            cfg.lookup("h").preferred_authentications.as_deref(),
            Some(&["password".to_string(), "publickey".to_string()][..])
        );
    }

    #[test]
    fn preferred_authentications_only_unimplementable_unsupported() {
        let err = SshClientConfig::parse("PreferredAuthentications gssapi-with-mic,hostbased\n")
            .unwrap_err();
        assert!(matches!(err, ConfigError::Unsupported { .. }));
    }

    #[test]
    fn preferred_authentications_unknown_method_rejected() {
        let err = SshClientConfig::parse("PreferredAuthentications quantum\n").unwrap_err();
        assert!(matches!(err, ConfigError::BadValue { .. }));
    }

    #[test]
    fn pubkey_authentication_parses() {
        let cfg = SshClientConfig::parse("PubkeyAuthentication no\n").unwrap();
        assert_eq!(cfg.lookup("h").pubkey_authentication, Some(false));
    }

    #[test]
    fn number_of_password_prompts_and_batchmode() {
        let cfg = SshClientConfig::parse("NumberOfPasswordPrompts 1\nBatchMode yes\n").unwrap();
        let eff = cfg.lookup("h");
        assert_eq!(eff.number_of_password_prompts, Some(1));
        assert_eq!(eff.batch_mode, Some(true));
    }

    #[test]
    fn exit_on_forward_failure_and_clear_all() {
        let cfg =
            SshClientConfig::parse("ExitOnForwardFailure yes\nClearAllForwardings yes\n").unwrap();
        let eff = cfg.lookup("h");
        assert_eq!(eff.exit_on_forward_failure, Some(true));
        assert_eq!(eff.clear_all_forwardings, Some(true));
    }

    #[test]
    fn dynamic_forward_parses() {
        let src = "Host gw\n  DynamicForward 1080\n  DynamicForward 127.0.0.1:1081\n";
        let cfg = SshClientConfig::parse(src).unwrap();
        let eff = cfg.lookup("gw");
        assert_eq!(eff.dynamic_forwards.len(), 2);
        assert_eq!(eff.dynamic_forwards[0].bind_addr, None);
        assert_eq!(eff.dynamic_forwards[0].listen_port, 1080);
        assert_eq!(
            eff.dynamic_forwards[1].bind_addr.as_deref(),
            Some("127.0.0.1")
        );
        assert_eq!(eff.dynamic_forwards[1].listen_port, 1081);
    }

    #[test]
    fn gateway_ports_parses() {
        for (s, want) in [
            ("no", GatewayPorts::No),
            ("yes", GatewayPorts::Yes),
            ("clientspecified", GatewayPorts::ClientSpecified),
        ] {
            let cfg = SshClientConfig::parse(&format!("GatewayPorts {s}\n")).unwrap();
            assert_eq!(cfg.lookup("h").gateway_ports, Some(want));
        }
    }

    #[test]
    fn address_family_parses() {
        for (s, want) in [
            ("any", AddressFamily::Any),
            ("inet", AddressFamily::Inet),
            ("inet6", AddressFamily::Inet6),
        ] {
            let cfg = SshClientConfig::parse(&format!("AddressFamily {s}\n")).unwrap();
            assert_eq!(cfg.lookup("h").address_family, Some(want));
        }
        let err = SshClientConfig::parse("AddressFamily ipx\n").unwrap_err();
        assert!(matches!(err, ConfigError::BadValue { .. }));
    }

    #[test]
    fn bind_address_parses() {
        let cfg = SshClientConfig::parse("BindAddress 10.0.0.5\n").unwrap();
        assert_eq!(cfg.lookup("h").bind_address.as_deref(), Some("10.0.0.5"));
    }

    #[test]
    fn identity_agent_parses() {
        let cfg = SshClientConfig::parse("IdentityAgent none\n").unwrap();
        assert_eq!(cfg.lookup("h").identity_agent, Some(IdentityAgent::None));
        let cfg = SshClientConfig::parse("IdentityAgent /run/agent.sock\n").unwrap();
        assert_eq!(
            cfg.lookup("h").identity_agent,
            Some(IdentityAgent::Path("/run/agent.sock".to_string()))
        );
    }

    // ----- Match-block tests --------------------------------------------

    #[test]
    fn match_host_glob() {
        let src = "\
Match host *.example.com
  User alice
";
        let cfg = SshClientConfig::parse(src).unwrap();
        assert_eq!(cfg.lookup("web.example.com").user.as_deref(), Some("alice"));
        assert_eq!(cfg.lookup("web.other.com").user, None);
    }

    #[test]
    fn control_master_values() {
        let cfg = SshClientConfig::parse("Host h\n  ControlMaster auto\n").unwrap();
        assert_eq!(cfg.lookup("h").control_master, Some(ControlMaster::Auto));
        let cfg = SshClientConfig::parse("Host h\n  ControlMaster yes\n").unwrap();
        assert_eq!(cfg.lookup("h").control_master, Some(ControlMaster::Yes));
        let cfg = SshClientConfig::parse("Host h\n  ControlMaster no\n").unwrap();
        assert_eq!(cfg.lookup("h").control_master, Some(ControlMaster::No));
    }

    #[test]
    fn control_master_ask_unsupported() {
        let err = SshClientConfig::parse("Host h\n  ControlMaster ask\n").unwrap_err();
        assert!(matches!(err, ConfigError::Unsupported { .. }));
        let err = SshClientConfig::parse("Host h\n  ControlMaster autoask\n").unwrap_err();
        assert!(matches!(err, ConfigError::Unsupported { .. }));
    }

    #[test]
    fn control_master_bad_value() {
        let err = SshClientConfig::parse("Host h\n  ControlMaster maybe\n").unwrap_err();
        assert!(matches!(err, ConfigError::BadValue { .. }));
    }

    #[test]
    fn control_path_none_disables() {
        let cfg = SshClientConfig::parse("Host h\n  ControlPath none\n").unwrap();
        assert_eq!(cfg.lookup("h").control_path, None);
        let cfg = SshClientConfig::parse("Host h\n  ControlPath ~/.ssh/cm-%r@%h:%p\n").unwrap();
        assert_eq!(
            cfg.lookup("h").control_path.as_deref(),
            Some("~/.ssh/cm-%r@%h:%p")
        );
    }

    #[test]
    fn control_persist_values() {
        let p = |s: &str| {
            SshClientConfig::parse(&format!("Host h\n  ControlPersist {s}\n"))
                .unwrap()
                .lookup("h")
                .control_persist
        };
        assert_eq!(p("no"), Some(ControlPersist::No));
        assert_eq!(p("yes"), Some(ControlPersist::Yes));
        assert_eq!(p("30"), Some(ControlPersist::Seconds(30)));
        assert_eq!(p("30s"), Some(ControlPersist::Seconds(30)));
        assert_eq!(p("5m"), Some(ControlPersist::Seconds(300)));
        assert_eq!(p("2h"), Some(ControlPersist::Seconds(7200)));
        // `0` collapses to No, matching OpenSSH.
        assert_eq!(p("0"), Some(ControlPersist::No));
    }

    #[test]
    fn control_persist_bad_value() {
        let err = SshClientConfig::parse("Host h\n  ControlPersist soon\n").unwrap_err();
        assert!(matches!(err, ConfigError::BadValue { .. }));
        let err = SshClientConfig::parse("Host h\n  ControlPersist 10x\n").unwrap_err();
        assert!(matches!(err, ConfigError::BadValue { .. }));
    }

    #[test]
    fn match_negated_host() {
        let src = "\
Match host *.example.com,!internal.example.com
  User alice
";
        let cfg = SshClientConfig::parse(src).unwrap();
        assert_eq!(cfg.lookup("web.example.com").user.as_deref(), Some("alice"));
        assert_eq!(cfg.lookup("internal.example.com").user, None);
    }

    #[test]
    fn match_user_combined_with_host() {
        let src = "\
Match host *.example.com user alice
  Port 2222
";
        let cfg = SshClientConfig::parse(src).unwrap();
        // No user supplied → does not match.
        assert_eq!(cfg.lookup("web.example.com").port, None);
        // Wrong user → does not match.
        let ctx = MatchContext {
            host: "web.example.com",
            original_host: None,
            user: Some("bob"),
            local_user: None,
            ..MatchContext::default()
        };
        assert_eq!(cfg.lookup_with(ctx).port, None);
        // Right user → matches.
        let ctx = MatchContext {
            host: "web.example.com",
            original_host: None,
            user: Some("alice"),
            local_user: None,
            ..MatchContext::default()
        };
        assert_eq!(cfg.lookup_with(ctx).port, Some(2222));
    }

    #[test]
    fn match_all_matches_everything() {
        let src = "\
Match all
  Port 4242
";
        let cfg = SshClientConfig::parse(src).unwrap();
        assert_eq!(cfg.lookup("anything").port, Some(4242));
        assert_eq!(cfg.lookup("other").port, Some(4242));
    }

    #[test]
    fn match_canonical_never_matches_in_first_pass() {
        let src = "\
Match canonical
  Port 4242
";
        let cfg = SshClientConfig::parse(src).unwrap();
        assert_eq!(cfg.lookup("anything").port, None);
    }

    #[test]
    fn match_final_never_matches_in_first_pass() {
        let src = "\
Match final
  Port 4242
";
        let cfg = SshClientConfig::parse(src).unwrap();
        assert_eq!(cfg.lookup("anything").port, None);
    }

    #[test]
    fn match_exec_disabled_by_default() {
        // Even with a command that would succeed on every platform, the
        // block must be silently skipped while the default policy is in
        // effect.
        let src = "\
Match exec true
  Port 4242
";
        let cfg = SshClientConfig::parse(src).unwrap();
        assert!(!cfg.is_match_exec_enabled());
        assert_eq!(cfg.lookup("anything").port, None);
    }

    #[cfg(unix)]
    #[test]
    fn match_exec_enabled_runs_command() {
        // Use the shell builtins `true` / `false` (not the `/bin/true`
        // / `/bin/false` binaries) so the test is portable: macOS
        // runners ship coreutils-style helpers at `/usr/bin/true` and
        // recent macOS images don't carry `/bin/true` at all, so an
        // absolute path here breaks `macos-latest` in CI. The `sh -c`
        // wrapper this code routes through always resolves the
        // builtins.
        let src = "\
Match exec true
  Port 4242
";
        let cfg = SshClientConfig::parse(src).unwrap().enable_match_exec(true);
        assert!(cfg.is_match_exec_enabled());
        assert_eq!(cfg.lookup("anything").port, Some(4242));

        let src_false = "\
Match exec false
  Port 4242
";
        let cfg = SshClientConfig::parse(src_false)
            .unwrap()
            .enable_match_exec(true);
        assert_eq!(cfg.lookup("anything").port, None);
    }

    #[test]
    fn match_originalhost_uses_pre_substitution_name() {
        let src = "\
Match originalhost prod
  Port 2200
";
        let cfg = SshClientConfig::parse(src).unwrap();
        let ctx = MatchContext {
            host: "10.0.0.1",
            original_host: Some("prod"),
            user: None,
            local_user: None,
            ..MatchContext::default()
        };
        assert_eq!(cfg.lookup_with(ctx).port, Some(2200));
    }

    #[test]
    fn match_localuser() {
        let src = "\
Match localuser alice
  Port 2200
";
        let cfg = SshClientConfig::parse(src).unwrap();
        let ctx = MatchContext {
            host: "h",
            original_host: None,
            user: None,
            local_user: Some("alice"),
            ..MatchContext::default()
        };
        assert_eq!(cfg.lookup_with(ctx).port, Some(2200));
        let ctx = MatchContext {
            host: "h",
            original_host: None,
            user: None,
            local_user: Some("bob"),
            ..MatchContext::default()
        };
        assert_eq!(cfg.lookup_with(ctx).port, None);
    }

    #[test]
    fn match_block_with_settings_parses() {
        // Sanity: settings inside a Match block actually get applied when
        // the block matches.
        let src = "\
Match host gw
  HostName 10.0.0.1
  Port 2222
  User admin
";
        let cfg = SshClientConfig::parse(src).unwrap();
        let eff = cfg.lookup("gw");
        assert_eq!(eff.host_name.as_deref(), Some("10.0.0.1"));
        assert_eq!(eff.port, Some(2222));
        assert_eq!(eff.user.as_deref(), Some("admin"));
    }

    #[test]
    fn match_unknown_criterion_errors() {
        let src = "Match address 1.2.3.4\n  Port 22\n";
        let err = SshClientConfig::parse(src).unwrap_err();
        match err {
            ConfigError::BadValue { line, .. } => assert_eq!(line, 1),
            _ => panic!("wrong err: {err:?}"),
        }
    }

    #[test]
    fn match_empty_args_errors() {
        let src = "Match\n  Port 22\n";
        let err = SshClientConfig::parse(src).unwrap_err();
        match err {
            ConfigError::BadValue { line, .. } => assert_eq!(line, 1),
            _ => panic!("wrong err: {err:?}"),
        }
    }

    // ----- ObscureKeystrokeTiming tests --------------------------------

    #[test]
    fn obscure_keystroke_timing_yes_defaults_to_20ms() {
        let cfg = SshClientConfig::parse("ObscureKeystrokeTiming yes\n").unwrap();
        assert_eq!(
            cfg.lookup("h").obscure_keystroke_timing,
            Some(ObscureKeystrokeTiming::On { interval_ms: 20 })
        );
    }

    #[test]
    fn obscure_keystroke_timing_no_is_off() {
        let cfg = SshClientConfig::parse("ObscureKeystrokeTiming no\n").unwrap();
        assert_eq!(
            cfg.lookup("h").obscure_keystroke_timing,
            Some(ObscureKeystrokeTiming::Off)
        );
    }

    #[test]
    fn obscure_keystroke_timing_interval_ms_integer() {
        let cfg = SshClientConfig::parse("ObscureKeystrokeTiming interval:80\n").unwrap();
        assert_eq!(
            cfg.lookup("h").obscure_keystroke_timing,
            Some(ObscureKeystrokeTiming::On { interval_ms: 80 })
        );
    }

    #[test]
    fn obscure_keystroke_timing_interval_time_units() {
        let cases = [
            ("interval:1s", 1000),
            ("interval:500ms", 500),
            ("interval:2m", 120_000),
        ];
        for (spec, want) in cases {
            let cfg = SshClientConfig::parse(&format!("ObscureKeystrokeTiming {spec}\n")).unwrap();
            assert_eq!(
                cfg.lookup("h").obscure_keystroke_timing,
                Some(ObscureKeystrokeTiming::On { interval_ms: want }),
                "spec {spec}"
            );
        }
    }

    #[test]
    fn obscure_keystroke_timing_unset_is_none() {
        let cfg = SshClientConfig::parse("Host h\n  Port 22\n").unwrap();
        assert_eq!(cfg.lookup("h").obscure_keystroke_timing, None);
    }

    #[test]
    fn obscure_keystroke_timing_malformed_is_bad_value() {
        for bad in [
            "ObscureKeystrokeTiming maybe\n",
            "ObscureKeystrokeTiming interval:\n",
            "ObscureKeystrokeTiming interval:abc\n",
            "ObscureKeystrokeTiming interval:0\n",
            "ObscureKeystrokeTiming interval:-5\n",
            "ObscureKeystrokeTiming 80\n",
        ] {
            let err = SshClientConfig::parse(bad).unwrap_err();
            assert!(
                matches!(err, ConfigError::BadValue { .. }),
                "input {bad:?} gave {err:?}"
            );
        }
    }

    #[test]
    fn obscure_keystroke_timing_default_helpers() {
        assert!(ObscureKeystrokeTiming::default_on().is_on());
        assert_eq!(ObscureKeystrokeTiming::default_on().interval_ms(), Some(20));
        assert!(!ObscureKeystrokeTiming::Off.is_on());
        assert_eq!(ObscureKeystrokeTiming::Off.interval_ms(), None);
    }

    #[test]
    fn append_layers_user_over_system() {
        // Mimics the CLI's default search path: the user file is loaded
        // first (higher precedence) and the system file appended below it.
        let mut user = SshClientConfig::parse("Host gw\n  Port 2200\n  IdentityFile /u/key\n")
            .expect("user parses");
        let system = SshClientConfig::parse("Host gw\n  Port 22\n  IdentityFile /etc/key\n")
            .expect("system parses");
        user.append(system);
        let eff = user.lookup("gw");
        // First-match-wins scalar: the user file's Port survives.
        assert_eq!(eff.port, Some(2200));
        // Cumulative list: user entry first, then system.
        assert_eq!(eff.identity_files, vec!["/u/key", "/etc/key"]);
    }

    // ----- Include-directive tests -------------------------------------

    #[cfg(feature = "std")]
    #[test]
    fn include_unsupported_in_string_parse() {
        // parse(&str) cannot resolve Include — it should surface a friendly
        // diagnostic rather than UnknownKeyword.
        let src = "Include /etc/ssh/somefile\n";
        let err = SshClientConfig::parse(src).unwrap_err();
        match err {
            ConfigError::Unsupported { line, msg } => {
                assert_eq!(line, 1);
                assert!(msg.contains("Include"), "msg = {msg}");
            }
            _ => panic!("wrong err: {err:?}"),
        }
    }

    #[cfg(feature = "std")]
    mod include_io {
        use super::*;
        use std::io::Write;
        use std::path::PathBuf;

        struct TempDir {
            path: PathBuf,
        }
        impl TempDir {
            fn new(prefix: &str) -> Self {
                use std::time::{SystemTime, UNIX_EPOCH};
                let nanos = SystemTime::now()
                    .duration_since(UNIX_EPOCH)
                    .map(|d| d.as_nanos())
                    .unwrap_or(0);
                let pid = std::process::id();
                let path =
                    std::env::temp_dir().join(format!("puressh-cfg-client-{prefix}-{pid}-{nanos}"));
                std::fs::create_dir_all(&path).expect("create tempdir");
                Self { path }
            }
            fn write(&self, name: &str, body: &str) -> PathBuf {
                let p = self.path.join(name);
                if let Some(parent) = p.parent() {
                    std::fs::create_dir_all(parent).expect("mkdir");
                }
                let mut f = std::fs::File::create(&p).expect("create file");
                f.write_all(body.as_bytes()).expect("write file");
                p
            }
        }
        impl Drop for TempDir {
            fn drop(&mut self) {
                let _ = std::fs::remove_dir_all(&self.path);
            }
        }

        #[test]
        fn include_pulls_in_settings() {
            let dir = TempDir::new("pull");
            let leaf = dir.write("leaf.cfg", "Port 4242\n");
            let root = dir.write(
                "root.cfg",
                &format!("Host gw\n  HostName 10.0.0.1\nInclude {}\n", leaf.display()),
            );
            let cfg = SshClientConfig::load(&root).unwrap();
            // Include is inside the `Host gw` block — its Port applies to gw.
            assert_eq!(cfg.lookup("gw").port, Some(4242));
            assert_eq!(cfg.lookup("gw").host_name.as_deref(), Some("10.0.0.1"));
        }

        #[test]
        fn include_glob_pulls_all_matches() {
            let dir = TempDir::new("glob");
            dir.write("conf.d/01.cfg", "Host gw\n  Port 2001\n");
            dir.write("conf.d/02.cfg", "Host gw\n  User u2\n");
            dir.write("conf.d/03.cfg", "Host gw\n  IdentityFile /tmp/k3\n");
            dir.write("conf.d/skip.txt", "Host gw\n  Port 9999\n");
            let root = dir.write(
                "root.cfg",
                &format!("Include {}/conf.d/*.cfg\n", dir.path.display()),
            );
            let cfg = SshClientConfig::load(&root).unwrap();
            let eff = cfg.lookup("gw");
            // First-match-wins on Port → 2001 (alphabetical 01.cfg sorts
            // first under our deterministic sort).
            assert_eq!(eff.port, Some(2001));
            assert_eq!(eff.user.as_deref(), Some("u2"));
            assert_eq!(eff.identity_files, vec!["/tmp/k3"]);
        }

        #[test]
        fn include_relative_to_containing_file() {
            // root.cfg lives in dir/; Include uses a bare filename, which
            // must be resolved against dir/ (not the CWD).
            let dir = TempDir::new("relative");
            dir.write("sibling.cfg", "Host gw\n  Port 7777\n");
            let root = dir.write("root.cfg", "Include sibling.cfg\n");
            let cfg = SshClientConfig::load(&root).unwrap();
            assert_eq!(cfg.lookup("gw").port, Some(7777));
        }

        #[test]
        fn include_missing_file_warned_not_fatal() {
            let dir = TempDir::new("missing");
            let root = dir.write(
                "root.cfg",
                &format!(
                    "Host gw\n  Port 22\nInclude {}/nope.cfg\n",
                    dir.path.display()
                ),
            );
            let cfg = SshClientConfig::load(&root).expect("missing include is non-fatal");
            assert_eq!(cfg.lookup("gw").port, Some(22));
        }

        #[test]
        fn include_circular_capped_at_16_depth() {
            // file A includes file A → infinite loop guarded by depth cap.
            let dir = TempDir::new("circ");
            // Path-stable file under the temp dir.
            let p = dir.path.join("loop.cfg");
            let body = format!("Include {}\n", p.display());
            std::fs::write(&p, body).expect("write loop.cfg");
            let err = SshClientConfig::load(&p).unwrap_err();
            match err {
                ConfigError::Syntax { msg, .. } => {
                    assert!(msg.contains("max depth"), "msg = {msg}");
                }
                _ => panic!("wrong err: {err:?}"),
            }
        }

        #[test]
        fn include_load_with_base_resolves_relative() {
            let dir = TempDir::new("loadbase");
            dir.write("inner.cfg", "Host gw\n  Port 9999\n");
            let src = "Include inner.cfg\n";
            let cfg = SshClientConfig::load_with_base(src, &dir.path).unwrap();
            assert_eq!(cfg.lookup("gw").port, Some(9999));
        }

        #[test]
        fn include_inside_match_block_only_applies_there() {
            // The Include sits inside a Host block — its settings should be
            // tagged onto that block, not bleed into a sibling block.
            let dir = TempDir::new("inblock");
            dir.write("only_gw.cfg", "Port 3300\n");
            let root = dir.write(
                "root.cfg",
                "Host gw\n  Include only_gw.cfg\nHost other\n  Port 22\n",
            );
            let cfg = SshClientConfig::load(&root).unwrap();
            assert_eq!(cfg.lookup("gw").port, Some(3300));
            assert_eq!(cfg.lookup("other").port, Some(22));
        }
    }
}