gander-core 0.6.5

//! Field identifiers and their presentation metadata.

use crate::Pid;

/// A displayable per-process column.
///
/// Variants mirror htop's `RowField.h` / `<platform>/ProcessField.h` semantics.
/// The numeric IDs deliberately do *not* match htop: only the `htoprc` importer
/// needs name-level compatibility.
///
/// Render with `match`, never `dyn` dispatch — thousands of rows times dozens of
/// columns per frame makes dynamic dispatch measurable.
#[derive(Copy, Clone, PartialEq, Eq, Hash, Debug, PartialOrd, Ord)]
#[non_exhaustive]
pub enum Field {
    Pid,
    Comm,
    State,
    Ppid,
    Pgrp,
    Session,
    Tty,
    Tpgid,
    MinFlt,
    MajFlt,
    Priority,
    Nice,
    StartTime,
    Processor,
    VirtMem,
    ResMem,
    User,
    PercentCpu,
    PercentMem,
    Time,
    Nlwp,
    Tgid,
    PercentNormCpu,
    Elapsed,
    SchedPolicy,
    ProcComm,
    ProcExe,
    Cwd,

    // Linux-only fields (see docs/DESIGN.md, milestone M3).
    #[cfg(target_os = "linux")]
    Pss,
    #[cfg(target_os = "linux")]
    Swap,
    #[cfg(target_os = "linux")]
    Private,
    #[cfg(target_os = "linux")]
    Epss,
    #[cfg(target_os = "linux")]
    Cgroup,
    #[cfg(target_os = "linux")]
    Container,
    #[cfg(target_os = "linux")]
    GpuPercent,
    #[cfg(target_os = "linux")]
    GpuTime,
    #[cfg(target_os = "linux")]
    CpuDelayPercent,
    #[cfg(target_os = "linux")]
    IoDelayPercent,
    #[cfg(target_os = "linux")]
    SwapDelayPercent,
}

impl Field {
    /// Whether reading this column requires `/proc/<pid>/smaps_rollup`.
    ///
    /// The sampler consults this before spending tens of milliseconds per tick on
    /// a kernel VMA walk: a column that is not on screen must not cost anything.
    /// Kept next to the `Field` definition so a future PSS-derived column cannot
    /// be added without answering the question.
    pub const fn needs_smaps_rollup(self) -> bool {
        #[cfg(target_os = "linux")]
        {
            matches!(self, Field::Pss | Field::Epss | Field::Private | Field::Swap)
        }
        #[cfg(not(target_os = "linux"))]
        {
            let _ = self;
            false
        }
    }

    /// Whether reading this column requires a `TASKSTATS` netlink query.
    ///
    /// Same contract as [`Self::needs_smaps_rollup`], with a higher price: every
    /// query is a syscall pair and a kernel task lookup, per process, per tick.
    pub const fn needs_delayacct(self) -> bool {
        #[cfg(target_os = "linux")]
        {
            matches!(
                self,
                Field::CpuDelayPercent | Field::IoDelayPercent | Field::SwapDelayPercent
            )
        }
        #[cfg(not(target_os = "linux"))]
        {
            let _ = self;
            false
        }
    }

    /// Whether reading this column requires scanning `/proc/<pid>/fdinfo`.
    ///
    /// Same contract as [`Self::needs_smaps_rollup`]: a column that is not on
    /// screen must not cost a directory walk per process per tick.
    pub const fn needs_gpu_fdinfo(self) -> bool {
        #[cfg(target_os = "linux")]
        {
            matches!(self, Field::GpuPercent | Field::GpuTime)
        }
        #[cfg(not(target_os = "linux"))]
        {
            let _ = self;
            false
        }
    }
}

/// Horizontal alignment of a column.
#[derive(Copy, Clone, PartialEq, Eq, Debug)]
pub enum Align {
    Left,
    Right,
}

/// Static description of a field, used by the setup screen and by the renderer.
pub struct FieldMeta {
    pub field: Field,
    /// Stable identifier used in config files (`"M_PSS"`).
    pub name: &'static str,
    /// Header cell text (`" PSS "`).
    pub title: &'static str,
    /// Human description shown in the setup screen.
    pub description: &'static str,
    /// Whether this column sorts descending by default.
    pub default_sort_desc: bool,
    pub align: Align,
}

impl Field {
    pub fn meta(self) -> Option<&'static FieldMeta> {
        FIELD_META.iter().find(|m| m.field == self)
    }

    /// Stable config name, e.g. `PercentCpu` -> `"PERCENT_CPU"`.
    pub fn name(self) -> &'static str {
        self.meta().map_or("UNKNOWN", |m| m.name)
    }

    /// Header text, e.g. `PercentCpu` -> `" CPU% "`.
    pub fn title(self) -> &'static str {
        self.meta().map_or(" ? ", |m| m.title)
    }

    pub fn default_sort_desc(self) -> bool {
        self.meta().is_some_and(|m| m.default_sort_desc)
    }

    /// All fields available on this platform, in setup-screen order.
    pub fn all() -> impl Iterator<Item = Field> {
        FIELD_META.iter().map(|m| m.field)
    }

    pub fn from_name(name: &str) -> Option<Field> {
        FIELD_META.iter().find(|m| m.name == name).map(|m| m.field)
    }
}

const fn m(
    field: Field,
    name: &'static str,
    title: &'static str,
    description: &'static str,
    default_sort_desc: bool,
    align: Align,
) -> FieldMeta {
    FieldMeta {
        field,
        name,
        title,
        description,
        default_sort_desc,
        align,
    }
}

const FIELD_META: &[FieldMeta] = &[
    m(
        Field::Pid,
        "PID",
        "   PID ",
        "Process ID",
        false,
        Align::Right,
    ),
    m(
        Field::Comm,
        "COMM",
        " COMMAND ",
        "Command name from /proc/<pid>/comm",
        false,
        Align::Left,
    ),
    m(
        Field::State,
        "STATE",
        " S ",
        "Process state",
        false,
        Align::Left,
    ),
    m(
        Field::Ppid,
        "PPID",
        "  PPID ",
        "Parent process ID",
        false,
        Align::Right,
    ),
    m(
        Field::Pgrp,
        "PGRP",
        "  PGRP ",
        "Process group ID",
        false,
        Align::Right,
    ),
    m(
        Field::User,
        "USER",
        " USER ",
        "Effective user",
        false,
        Align::Left,
    ),
    m(
        Field::Priority,
        "PRIORITY",
        " PRI ",
        "Kernel scheduling priority",
        false,
        Align::Right,
    ),
    m(
        Field::Nice,
        "NICE",
        " NI ",
        "Nice value",
        false,
        Align::Right,
    ),
    m(
        Field::PercentCpu,
        "PERCENT_CPU",
        " CPU% ",
        "CPU usage in percent",
        true,
        Align::Right,
    ),
    m(
        Field::PercentMem,
        "PERCENT_MEM",
        " MEM% ",
        "Memory usage in percent",
        true,
        Align::Right,
    ),
    m(
        Field::PercentNormCpu,
        "PERCENT_NORM_CPU",
        " NCPU% ",
        "CPU usage normalized by core count",
        true,
        Align::Right,
    ),
    m(
        Field::Time,
        "TIME",
        "  TIME+ ",
        "Cumulative CPU time",
        true,
        Align::Right,
    ),
    m(
        Field::Elapsed,
        "ELAPSED",
        " ELAPSED ",
        "Time since the process started",
        false,
        Align::Right,
    ),
    m(
        Field::ResMem,
        "M_RESIDENT",
        "  RES ",
        "Resident set size",
        true,
        Align::Right,
    ),
    m(
        Field::VirtMem,
        "M_VIRT",
        "  VIRT ",
        "Virtual memory size",
        true,
        Align::Right,
    ),
    m(
        Field::Nlwp,
        "NLWP",
        " NLWP ",
        "Number of threads",
        false,
        Align::Right,
    ),
    m(
        Field::Processor,
        "PROCESSOR",
        " CPU ",
        "Last used CPU",
        false,
        Align::Right,
    ),
    m(
        Field::MinFlt,
        "MINFLT",
        " MINFLT ",
        "Minor page faults",
        false,
        Align::Right,
    ),
    m(
        Field::MajFlt,
        "MAJFLT",
        " MAJFLT ",
        "Major page faults",
        false,
        Align::Right,
    ),
    // Session and the controlling terminal. Both are in `/proc/<pid>/stat` (fields
    // 4 and 5) and in Darwin's `kinfo_proc`, so they are real on every platform;
    // they were declared as `Field` variants with no metadata, which made them
    // unreachable: no name, no header, no setup entry, and an `htoprc` that named
    // them imported to the string `"UNKNOWN"` and was silently dropped.
    m(
        Field::Session,
        "SESSION",
        " SID ",
        "Session ID: the login session this process belongs to",
        false,
        Align::Right,
    ),
    m(
        Field::Tty,
        "TTY",
        " TTY      ",
        "Controlling terminal, or `?` when there is none",
        false,
        Align::Left,
    ),
    // The process group a *terminal* is currently sending its signals to. Equal to
    // PGRP unless one of the jobs is in the foreground.
    m(
        Field::Tpgid,
        "TPGID",
        "  TPGID ",
        "Process group of the foreground job on this terminal",
        false,
        Align::Right,
    ),
    // Wall-clock start, not the `starttime` ticks kept for PID-reuse detection:
    // ticks since boot mean nothing without the boot time next to them.
    m(
        Field::StartTime,
        "STARTTIME",
        " START     ",
        "Wall-clock time this process started",
        false,
        Align::Left,
    ),
    m(
        Field::Tgid,
        "TGID",
        "  TGID ",
        "Thread group ID: the pid of the process a thread row belongs to",
        false,
        Align::Right,
    ),
    m(
        Field::SchedPolicy,
        "SCHED_POLICY",
        " POL ",
        "Scheduling policy: other, fifo, rr, batch, idle, deadline",
        false,
        Align::Left,
    ),
    // The two PROC_* fields exist because `COMM` is the *command line* here (what
    // htop's Command column shows), so the kernel's own short name needs its own
    // column. htop draws the same distinction: `COMM` vs `PROC_COMM`.
    m(
        Field::ProcComm,
        "PROC_COMM",
        " COMMAND       ",
        "Kernel's short command name, always the executable's base name",
        false,
        Align::Left,
    ),
    m(
        Field::ProcExe,
        "PROC_EXE",
        " EXE                ",
        "Path to the executable, as the kernel resolved it",
        false,
        Align::Left,
    ),
    m(
        Field::Cwd,
        "CWD",
        " CWD                ",
        "Working directory of the process",
        false,
        Align::Left,
    ),
    // Linux-only: cgroup membership, and the container derived from it.
    #[cfg(target_os = "linux")]
    m(
        Field::Cgroup,
        "CGROUP",
        " CGROUP ",
        "Full cgroup path",
        false,
        Align::Left,
    ),
    #[cfg(target_os = "linux")]
    m(
        Field::Container,
        "CONTAINER",
        " CONTAINER ",
        "Container id, prefixed with its runtime",
        false,
        Align::Left,
    ),
    // The PSS family. All four come from `/proc/<pid>/smaps_rollup`, which is why
    // they share `Field::needs_smaps_rollup` — the sampler reads it only when one
    // of these is on screen.
    #[cfg(target_os = "linux")]
    m(
        Field::Pss,
        "M_PSS",
        "  PSS ",
        "Proportional set size: shared pages divided between sharers",
        true,
        Align::Right,
    ),
    #[cfg(target_os = "linux")]
    m(
        Field::Epss,
        "M_EPSS",
        " EPSS ",
        "Effective PSS: PSS plus the swapped-out equivalent",
        true,
        Align::Right,
    ),
    #[cfg(target_os = "linux")]
    m(
        Field::Private,
        "M_PRIVATE",
        " PRIV ",
        "Private memory: what would be freed if this process exited",
        true,
        Align::Right,
    ),
    #[cfg(target_os = "linux")]
    m(
        Field::Swap,
        "M_SWAP",
        "  SWP ",
        "Memory this process has pushed to swap",
        true,
        Align::Right,
    ),
    // GPU, from `drm-usage-stats` keys in `fdinfo`. No vendor SDK is involved:
    // the kernel exports these for every driver that opts in, which today means
    // amdgpu, i915/xe, nouveau and (partially) nvidia.
    #[cfg(target_os = "linux")]
    m(
        Field::GpuPercent,
        "GPU%",
        " GPU% ",
        "Share of GPU time this process used, from drm-usage-stats",
        true,
        Align::Right,
    ),
    #[cfg(target_os = "linux")]
    m(
        Field::GpuTime,
        "GPU_TIME",
        "  GPUT ",
        "Cumulative GPU time, across every engine class",
        true,
        Align::Right,
    ),
    // Delay accounting, from `TASKSTATS` over generic netlink. The figures are
    // shares of the task's lifetime spent *waiting*: runnable but not on a CPU;
    // blocked on synchronous I/O; waiting for a page to be swapped back in.
    //
    // htop names these `PERCENT_CPU_DELAY`, `PERCENT_IO_DELAY` and
    // `PERCENT_SWAP_DELAY`; the ids match htop's `ProcessField.h` so an htoprc
    // imports.
    #[cfg(target_os = "linux")]
    m(
        Field::CpuDelayPercent,
        "CPUD%",
        "CPUD% ",
        "Share of this task's life spent runnable but waiting for a CPU",
        true,
        Align::Right,
    ),
    #[cfg(target_os = "linux")]
    m(
        Field::IoDelayPercent,
        "IOD%",
        " IOD% ",
        "Share of this task's life spent waiting for synchronous block I/O",
        true,
        Align::Right,
    ),
    #[cfg(target_os = "linux")]
    m(
        Field::SwapDelayPercent,
        "SWPD%",
        "SWPD% ",
        "Share of this task's life spent waiting for a page to be swapped in",
        true,
        Align::Right,
    ),
];

/// Names of the fields shown in the default M0 layout.
pub const DEFAULT_COLUMNS: &[Field] = &[
    Field::Pid,
    Field::User,
    Field::Priority,
    Field::Nice,
    Field::PercentCpu,
    Field::PercentMem,
    Field::Time,
    Field::Comm,
];

/// A process name, bounded to avoid any heap allocation during a scan.
pub type CommBuf = arrayvec::ArrayString<64>;

/// Raw, monotonically increasing CPU tick counters for one process.
///
/// CPU percent can only be derived from two samples; see `docs/DESIGN.md` §3.5.
#[derive(Copy, Clone, Default, Debug)]
pub struct CpuTicks {
    /// `utime + stime` of the process, in clock ticks.
    pub proc: u64,
    /// System-wide total ticks across all CPUs at the same instant.
    pub total: u64,
}

bitflags_like::flags! {
    /// Properties of a row that affect rendering and filtering.
    pub struct RowFlags: u16 {
        const KERNEL_THREAD = 1 << 0;
        const USERLAND_THREAD = 1 << 1;
        const STALE_EXE = 1 << 2;
        const STALE_LIB = 1 << 3;
        const NEW = 1 << 4;
    }
}

/// Internal shim: a tiny bitflags implementation, to avoid a dependency.
mod bitflags_like {
    macro_rules! flags {
        (
            $(#[$meta:meta])*
            pub struct $name:ident: $ty:ty {
                $(
                    const $flag:ident = $value:expr;
                )*
            }
        ) => {
            $(#[$meta])*
            #[derive(Copy, Clone, Default, PartialEq, Eq, Debug)]
            pub struct $name(pub $ty);

            impl $name {
                $(pub const $flag: $name = $name($value);)*

                pub const fn empty() -> Self { $name(0) }

                pub const fn contains(self, other: Self) -> bool {
                    (self.0 & other.0) == other.0
                }

                pub const fn intersects(self, other: Self) -> bool {
                    (self.0 & other.0) != 0
                }

                pub const fn insert(self, other: Self) -> Self {
                    $name(self.0 | other.0)
                }

                pub const fn remove(self, other: Self) -> Self {
                    $name(self.0 & !other.0)
                }

                pub const fn set(self, other: Self, on: bool) -> Self {
                    if on { self.insert(other) } else { self.remove(other) }
                }
            }
        };
    }

    pub(crate) use flags;
}

/// One process, as sampled during a single tick.
///
/// **Invariant: `Row` stores raw scalars and interned strings only.** Any
/// `String` produced by `format!` during a scan is a bug — see
/// `docs/DESIGN.md` §9.4. Human-readable text is produced by the renderer
/// through `crate::format`.
#[derive(Clone, Debug)]
pub struct Row {
    pub pid: Pid,
    pub ppid: Pid,
    pub pgrp: Pid,
    pub session: Pid,
    pub tty_nr: i64,
    /// The process group the controlling terminal is currently signalling.
    ///
    /// Equal to `pgrp` unless a job has the terminal in the foreground, which is
    /// the one distinction this column exists to show.
    ///
    /// `-1` is what the kernel reports when the terminal has no foreground job,
    /// and it is also what a thread row carries. The renderer shows `-` for it
    /// rather than the number: `-1` is a wire value, not a process group.
    pub tpgid: i64,
    /// Field 22 of `/proc/<pid>/stat`: cache key and PID-reuse detector.
    pub starttime: u64,
    /// Thread group id: the pid of the process this row belongs to.
    ///
    /// For a process this equals `pid`. For a thread it is the leader's pid,
    /// which is what lets the table nest threads under their process and keep
    /// the selection stable while thread enumeration is toggled.
    pub tgid: Pid,
    /// True when this row is a thread rather than a process.
    ///
    /// Kept separate from `RowFlags::USERLAND_THREAD` because that flag answers
    /// "is this a userland thread" for display purposes, while this answers a
    /// structural question the table has to get right.
    pub is_thread: bool,
    /// Identity of a thread row, unique across the whole table.
    ///
    /// For a process row this is `None` and `pid` is the identity. For a thread it
    /// is `Some`, because on macOS a thread has no pid of its own: `pth` handles
    /// are 64-bit (95% exceed `u32`) and are *not* globally unique (every process
    /// reports the same handle for its main thread). Linux threads do have a tid
    /// that fits in `pid`, but it can coincide with an unrelated process's pid, so
    /// thread rows use this on both platforms.
    pub thread_id: Option<u64>,

    /// `ArrayString<64>`: no heap allocation per scanned process.
    pub comm: CommBuf,
    pub state: u8,

    pub uid: u32,
    pub user: Option<u32>, // index into the user-name table

    pub priority: i8,
    pub nice: i8,
    pub processor: i32,
    pub nlwp: i32,
    pub sched_policy: u8,

    /// Raw tick counters, current and previous sample.
    pub ticks: CpuTicks,
    pub prev_ticks: CpuTicks,

    pub min_flt: u64,
    pub maj_flt: u64,

    /// Virtual and resident size in bytes.
    pub virt: u64,
    pub res: u64,

    /// Derived values, computed at sample time (not at render time).
    pub percent_cpu: f32,
    pub percent_mem: f32,
    /// `utime + stime` in ticks, kept for the TIME column.
    pub time_ticks: u64,
    /// Seconds since process start.
    pub elapsed: u64,

    /// Lazily loaded, cached until the process exits.
    pub cmdline: Option<Box<str>>,
    pub exe: Option<Box<str>>,
    /// The process's working directory, read from `/proc/<pid>/cwd` or, on macOS,
    /// from `proc_pidinfo(PROC_PIDVNODEPATHINFO)`.
    ///
    /// Cached with the identity because a `readlink` per row per tick is
    /// thousands of syscalls for a value that changes rarely — even though, unlike
    /// `exe`, it *can* change. Accepting a stale value until the process exits is
    /// the same trade htop makes.
    pub cwd: Option<Box<str>>,
    /// Proportional set size, from `/proc/<pid>/smaps_rollup`, in bytes.
    ///
    /// `None` means "not read", not "zero": the file is expensive enough that
    /// it is only opened when a column needing it is visible, and another user's
    /// process may refuse to be read at all. The renderer shows `-` for `None`
    /// and a real figure for `Some(0)`.
    ///
    /// RSS counts a shared page once per process, so two processes sharing 100 MB
    /// of libraries report 100 MB each and the machine appears to use 200 MB.
    /// PSS splits that page between them, which is the only figure that adds up
    /// across the table.
    #[cfg(target_os = "linux")]
    pub pss: Option<u64>,
    /// `Pss` + `SwapPss`: what the process costs including what it pushed to swap.
    #[cfg(target_os = "linux")]
    pub epss: Option<u64>,
    /// Memory exclusively this process's (`Private_Clean + Private_Dirty`).
    ///
    /// The complement of the shared part: PSS minus this is what would be freed
    /// if the process exited and nothing else changed.
    #[cfg(target_os = "linux")]
    pub private: Option<u64>,
    /// Bytes of this process's memory currently in swap (`Swap` from rollup).
    #[cfg(target_os = "linux")]
    pub swap_bytes: Option<u64>,
    /// GPU utilisation in percent, from `drm-usage-stats` keys in `fdinfo`.
    ///
    /// `None` when the process holds no DRM descriptor, or holds one whose driver
    /// reports no `drm-busy`, or the `fdinfo` files are unreadable. Those are
    /// three different reasons for the same thing — "no percentage is available"
    /// — and none of them is zero.
    #[cfg(target_os = "linux")]
    pub gpu_percent: Option<f32>,
    /// Cumulative GPU nanoseconds, across every engine class the driver reports.
    #[cfg(target_os = "linux")]
    pub gpu_ns: Option<u64>,
    /// Share of this task's life spent runnable but waiting for a CPU.
    ///
    /// From `TASKSTATS`; see `linux::delayacct`. `None` means unread — no
    /// `CAP_NET_ADMIN`, no `CONFIG_TASKSTATS`, or no delay column visible — and
    /// renders `-`, never `0.0`.
    pub cpu_delay_percent: Option<f32>,
    /// Share of this task's life spent waiting for synchronous block I/O.
    pub io_delay_percent: Option<f32>,
    /// Share of this task's life spent waiting for a page to be swapped in.
    pub swap_delay_percent: Option<f32>,
    /// The process's cgroup path, e.g. `/system.slice/docker-1f2e….scope`.
    ///
    /// The *path*, not the raw `/proc/<pid>/cgroup` line: the raw line is
    /// `12:cpuset:/docker/abc` and carries the hierarchy id and controller list,
    /// which no column wants. The v2 entry (empty controller list) is preferred
    /// when present, because that is the hierarchy the whole machine shares.
    pub cgroup: Option<Box<str>>,
    /// The container this process belongs to, if any.
    ///
    /// Derived from `cgroup` once per process and cached with it. Linux-only
    /// because the detection is cgroup-based; `None` everywhere else.
    #[cfg(target_os = "linux")]
    pub container: Option<Box<str>>,
    /// The runtime that owns the container (`docker`, `kubepods`, …), kept apart
    /// from `container` so the `CONTAINER` column can show `docker:1f2e…` without
    /// re-parsing the path at render time.
    #[cfg(target_os = "linux")]
    pub container_runtime: Option<Box<str>>,

    /// Tree bookkeeping, filled by `tree::build`.
    pub depth: u16,
    pub has_children: bool,
    pub is_last_child: bool,

    pub flags: RowFlags,
}

impl Row {
    /// Construct a minimal row, used by tests and by the tree helpers.
    pub fn default_for_test(pid: Pid) -> Self {
        Row {
            pid,
            ppid: 0,
            pgrp: 0,
            session: 0,
            tty_nr: 0,
            tpgid: -1,
            starttime: 0,
            tgid: pid,
            is_thread: false,
            thread_id: None,
            comm: CommBuf::new(),
            state: b'R',
            uid: 0,
            user: None,
            priority: 20,
            nice: 0,
            processor: 0,
            nlwp: 1,
            sched_policy: 0,
            ticks: CpuTicks::default(),
            prev_ticks: CpuTicks::default(),
            min_flt: 0,
            maj_flt: 0,
            virt: 0,
            res: 0,
            percent_cpu: 0.0,
            percent_mem: 0.0,
            time_ticks: 0,
            elapsed: 0,
            cmdline: None,
            exe: None,
            cwd: None,
            #[cfg(target_os = "linux")]
            pss: None,
            #[cfg(target_os = "linux")]
            epss: None,
            #[cfg(target_os = "linux")]
            private: None,
            #[cfg(target_os = "linux")]
            swap_bytes: None,
            #[cfg(target_os = "linux")]
            gpu_percent: None,
            #[cfg(target_os = "linux")]
            gpu_ns: None,
            cpu_delay_percent: None,
            io_delay_percent: None,
            swap_delay_percent: None,
            cgroup: None,
            #[cfg(target_os = "linux")]
            container: None,
            #[cfg(target_os = "linux")]
            container_runtime: None,
            depth: 0,
            has_children: false,
            is_last_child: false,
            flags: RowFlags::empty(),
        }
    }

    /// Major page faults.
    ///
    /// Exposed as a method so sort keys and renderers read symmetrically.
    pub const fn maj_flt_count(&self) -> u64 {
        self.maj_flt
    }

    /// Total CPU ticks consumed by the process.
    pub const fn time_ticks_total(&self) -> u64 {
        self.time_ticks
    }

    pub fn is_kernel_thread(&self) -> bool {
        self.flags.contains(RowFlags::KERNEL_THREAD)
    }

    /// The value that identifies this row across samples.
    ///
    /// `pid` for a process, a thread-specific id for a thread. Used wherever a
    /// row must be told apart from another row with the same `pid`, which on
    /// macOS every thread of a process shares.
    pub fn identity(&self) -> u64 {
        match self.thread_id {
            Some(id) => id,
            None => self.pid as u64,
        }
    }

    /// Text for the command column: `cmdline` if known, else `comm`, with
    /// kernel threads bracketed per htop's convention.
    pub fn display_command(&self) -> &str {
        match &self.cmdline {
            Some(c) if !c.is_empty() => c,
            _ => self.comm.as_str(),
        }
    }

    /// The executable's base name, and where it sits in [`Self::display_command`].
    ///
    /// Returns `(start, end)` byte offsets into `display_command()` so the renderer
    /// can emphasise those cells without re-deriving the text or allocating.
    ///
    /// # Why this is not just "the last path component"
    ///
    /// The command line is `argv` joined by spaces, so a naive split on `/` finds
    /// a path in an *argument* too (`grep /usr/lib/foo`). The base name is taken
    /// from `exe` when the sampler has it, and located in the command text as a
    /// prefix match on that path; when `exe` is unavailable (another user's
    /// process) it falls back to the first word of the command, which is what
    /// argv[0] is.
    ///
    /// Returns `None` when there is nothing worth highlighting — a kernel thread
    /// in brackets, or a command whose base name is the whole string.
    pub fn base_name_span(&self) -> Option<(usize, usize)> {
        self.base_name_span_in(self.display_command())
    }

    /// [`Self::base_name_span`] against `text` instead of the command column text.
    ///
    /// The renderer prepends the tree branch prefix to the command column, so the
    /// span it needs is offset by that prefix's length. Searching the *finished*
    /// text is simpler and more robust than adding an offset to the span: the
    /// prefix can only appear before the command, and the exe path search below
    /// does not match it.
    pub fn base_name_span_in(&self, text: &str) -> Option<(usize, usize)> {
        if text.is_empty() {
            return None;
        }

        // Prefer the real exe path: a prefix of the command line, when we have it.
        if let Some(exe) = self.exe.as_deref() {
            if !exe.is_empty() {
                if let Some(pos) = text.find(exe) {
                    let start = pos + exe.rfind('/').map_or(0, |i| i + 1);
                    let end = pos + exe.len();
                    if end > start {
                        return Some((start, end));
                    }
                }
            }
        }

        // Fall back to argv[0]: everything up to the first space.
        let end = text.find(' ').unwrap_or(text.len());
        let word = &text[..end];
        // A bracketed name is a kernel thread, and htop does not highlight those.
        if word.starts_with('[') {
            return None;
        }
        let start = word.rfind('/').map_or(0, |i| i + 1);
        // Nothing to gain from highlighting the entire string.
        if start == 0 && end == text.len() {
            return None;
        }
        if end > start {
            Some((start, end))
        } else {
            None
        }
    }
}

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

    fn row_with(cmdline: &str, exe: Option<&str>) -> Row {
        let mut r = Row::default_for_test(1);
        r.cmdline = Some(cmdline.into());
        r.exe = exe.map(Into::into);
        r
    }

    #[test]
    fn finds_the_basename_inside_a_full_path() {
        let r = row_with(
            "/Applications/iTerm.app/Contents/MacOS/iTerm2 --server",
            Some("/Applications/iTerm.app/Contents/MacOS/iTerm2"),
        );
        let text = r.display_command();
        let (s, e) = r.base_name_span().expect("span");
        assert_eq!(&text[s..e], "iTerm2");
    }

    /// The exe path is authoritative, so an argument that looks like a path must
    /// not win. `grep /usr/lib/foo` should highlight `grep`.
    #[test]
    fn an_argument_path_does_not_win_over_the_exe() {
        let r = row_with("grep /usr/lib/foo", Some("/usr/bin/grep"));
        let text = r.display_command();
        let (s, e) = r.base_name_span().expect("span");
        assert_eq!(&text[s..e], "grep");
    }

    /// Without `exe` (another user's process) fall back to argv[0].
    #[test]
    fn falls_back_to_argv0_without_an_exe() {
        let r = row_with("/usr/bin/python3 script.py", None);
        let text = r.display_command();
        let (s, e) = r.base_name_span().expect("span");
        assert_eq!(&text[s..e], "python3");
    }

    #[test]
    fn a_bare_command_name_gets_no_span() {
        // Nothing to emphasise: the name is the whole string already.
        let r = row_with("launchd", None);
        assert_eq!(r.base_name_span(), None);
    }

    #[test]
    fn a_kernel_thread_gets_no_span() {
        let r = row_with("[kworker/0:1]", None);
        assert_eq!(r.base_name_span(), None);
    }

    #[test]
    fn an_empty_command_gets_no_span() {
        let mut r = Row::default_for_test(1);
        r.cmdline = None;
        r.comm.try_push_str("").unwrap();
        assert_eq!(r.base_name_span(), None);
    }

    /// The renderer passes the *finished* column text, which in tree mode carries
    /// a branch prefix. The span has to move with it.
    #[test]
    fn the_span_tracks_a_prepended_tree_prefix() {
        let r = row_with("/usr/bin/nginx -g daemon", Some("/usr/bin/nginx"));
        let plain = r.display_command();
        let (s, e) = r.base_name_span().expect("span");
        assert_eq!(&plain[s..e], "nginx");

        let prefixed = format!("├─ {plain}");
        let (ps, pe) = r.base_name_span_in(&prefixed).expect("span");
        assert_eq!(&prefixed[ps..pe], "nginx");
        assert_eq!(ps, s + "├─ ".len(), "offset by the prefix");
    }

    /// A base name containing a space would make the argv[0] fallback wrong, but
    /// the exe path still locates it correctly.
    #[test]
    fn an_exe_with_spaces_is_located_by_path_not_by_word() {
        let r = row_with(
            "/Users/x/My App.app/Contents/MacOS/My App --flag",
            Some("/Users/x/My App.app/Contents/MacOS/My App"),
        );
        let text = r.display_command();
        let (s, e) = r.base_name_span().expect("span");
        assert_eq!(&text[s..e], "My App");
    }
}

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

    /// Every `Field` variant must have a `FieldMeta`.
    ///
    /// This is the guard for a real bug: `Session`, `Tty`, `Tpgid`, `StartTime`,
    /// `Tgid`, `SchedPolicy`, `ProcComm`, `ProcExe` and `Cwd` were declared as
    /// variants with no metadata, which made them unreachable in three ways at
    /// once — `name()` returned `"UNKNOWN"`, so an `htoprc` that named them
    /// imported to a column string that `TabConfig::fields` silently dropped;
    /// they never appeared in the setup screen, which iterates `Field::all()`; and
    /// the header title was `" ? "`. Nothing failed loudly, so it went unnoticed.
    ///
    /// The list below is written out rather than derived, because `Field` has no
    /// `strum`-style enumeration and adding a derive for one test is not worth the
    /// dependency. A new variant therefore requires editing this list too — which
    /// is the point: the test is a checklist, not an oracle.
    #[test]
    fn every_variant_has_metadata() {
        let all = [
            Field::Pid,
            Field::Comm,
            Field::State,
            Field::Ppid,
            Field::Pgrp,
            Field::Session,
            Field::Tty,
            Field::Tpgid,
            Field::MinFlt,
            Field::MajFlt,
            Field::Priority,
            Field::Nice,
            Field::StartTime,
            Field::Processor,
            Field::VirtMem,
            Field::ResMem,
            Field::User,
            Field::PercentCpu,
            Field::PercentMem,
            Field::Time,
            Field::Nlwp,
            Field::Tgid,
            Field::PercentNormCpu,
            Field::Elapsed,
            Field::SchedPolicy,
            Field::ProcComm,
            Field::ProcExe,
            Field::Cwd,
        ];
        #[allow(unused_mut)]
        let mut all = all.to_vec();
        #[cfg(target_os = "linux")]
        all.extend([
            Field::Pss,
            Field::Swap,
            Field::Private,
            Field::Epss,
            Field::Cgroup,
            Field::Container,
            Field::GpuPercent,
            Field::GpuTime,
            Field::CpuDelayPercent,
            Field::IoDelayPercent,
            Field::SwapDelayPercent,
        ]);

        for field in all {
            let meta = field
                .meta()
                .unwrap_or_else(|| panic!("{field:?} has no FieldMeta"));
            assert_ne!(meta.name, "UNKNOWN", "{field:?} has no name");
            assert_ne!(meta.title.trim(), "?", "{field:?} has no header title");
            assert!(
                !meta.description.is_empty(),
                "{field:?} has no description for the setup screen"
            );
            // The name is the config key and the `--sort` argument, so it must
            // resolve back to the same field.
            assert_eq!(
                Field::from_name(meta.name),
                Some(field),
                "{field:?} does not round-trip through {}",
                meta.name
            );
        }
    }

    /// The same check for `Field::all()`: a variant with metadata but not in the
    /// table is equally invisible, because the setup screen iterates the table.
    #[test]
    fn every_metadata_entry_is_offered_by_all() {
        let offered: Vec<Field> = Field::all().collect();
        for field in &offered {
            assert!(field.meta().is_some());
        }
        for wanted in [Field::Session, Field::Tty, Field::Cwd, Field::ProcComm] {
            assert!(
                offered.contains(&wanted),
                "{wanted:?} must be selectable in the setup screen"
            );
        }
    }

    /// Names must be unique, or `from_name` would resolve to whichever came first.
    #[test]
    fn names_are_unique() {
        let mut seen = std::collections::HashSet::new();
        for field in Field::all() {
            assert!(seen.insert(field.name()), "duplicate name {}", field.name());
        }
    }
}