shep 0.21.0

//! What the pane spends its width on, and the measuring every line goes
//! through.
//!
//! Column widths are fixed rather than measured from content, the same
//! choice the flock table makes and for the same reason. The one variable
//! is whether the explanation panel fits beside the field list, which
//! [`panel_width`] decides once per frame and every layout below reads.

use ratatui::text::Line;
use shep_core::config::ApplyGroup;

use super::super::flock::{GUTTER, take_columns};
use crate::lookout::pane::UNSET;
use crate::output::width::{char_columns, text_columns};

/// The close dialog's own interior width, once it is boxed: what
/// [`super::close::close_dialog_lines`] lays its rows out to when [`super::close::draw_close_dialog`]
/// draws the boxed form.
pub(super) const BOX_WIDTH: u16 = 86;

/// The KEY cell at its full width, flag character included. Twenty-six is
/// `exp_backoff_restart_delay` plus its flag, the longest key the Flockfile
/// schema declares, so no field name is truncated at a width that can
/// afford the whole column.
pub(super) const KEY_W: u16 = 26;

/// The floor KEY shrinks to before the COST column is dropped instead.
pub(super) const KEY_MIN: u16 = 8;

/// The floor VALUE shrinks to. Below this the pane drops COST, and below
/// that it draws KEY alone.
pub(super) const VALUE_MIN: u16 = 8;

/// The position cell on the list sub-screen. Three columns holds an index
/// into an array longer than any Flockfile has, and no more: an element is
/// what the row is about.
pub(super) const POSITION_W: u16 = 3;

/// The COST cell. Ten columns, which is exactly `next start`, the longest
/// word [`cost_label`] prints.
pub(super) const COST_W: u16 = 10;

/// The narrowest body that still draws KEY, VALUE and COST.
pub(super) const FULL_WIDTH: u16 = KEY_W + 2 + VALUE_MIN + 2 + COST_W;

/// The narrowest body that still draws a VALUE beside the KEY.
pub(super) const VALUE_WIDTH: u16 = KEY_MIN + 2 + VALUE_MIN;

/// The blurb's own wrap width, independent of whatever width the panel
/// itself draws at: prose reads better narrower than the panel's outer
/// ceiling allows, the same way a magazine column is narrower than the
/// page.
pub(super) const BLURB_WRAP: u16 = 66;

/// The narrowest left column that still draws a marker, a key and a value.
pub(super) const LEFT_MIN: u16 = 40;

/// The narrowest panel that holds a wrapped blurb and a validation list.
pub(super) const PANEL_MIN: u16 = 50;

/// The panel at the design target, and the ceiling everywhere else.
pub(super) const PANEL_MAX: u16 = 72;

/// How wide the explanation panel is, and [`None`] when it does not draw.
///
/// 45% of 160 is 72, so the design target falls out of the formula rather
/// than being special cased, and [`PANEL_MAX`] holds it there. Below
/// [`LEFT_MIN`] the panel cannot hold a blurb and a validation list beside
/// a usable left column, and [`super::draw::pane_lines`] falls back to one
/// column.
pub(super) fn panel_width(width: u16) -> Option<u16> {
    let wanted = (u32::from(width) * 45 / 100) as u16;
    let panel = wanted.clamp(PANEL_MIN, PANEL_MAX);
    (width.saturating_sub(panel) >= LEFT_MIN).then_some(panel)
}

/// The narrowest terminal that draws `LANDS` beside the panel rather than
/// giving way to it. The design target itself: at 160 the frame's own
/// `FIELD / VALUE / LANDS` header and the `FOCUSED` panel share a row, per
/// `docs/lookout/design-files/rulings.md`'s 1e ruling and
/// `docs/brainstorming/specs/2026-09-08-lookout-1e-editing-pane-design.md`'s
/// width table.
pub(super) const LANDS_WITH_PANEL_MIN: u16 = 160;

/// Whether `LANDS` draws on a terminal `width` columns wide that also draws
/// the panel (`has_panel`).
///
/// `LANDS` is what an operator scans to read every field's cost at once;
/// the panel is a sentence about the focused field alone. Where they cannot
/// both fit, `LANDS` gives way, since the panel already names that field's
/// cost. Always `true` when the panel is absent.
pub(super) const fn lands_fits_beside_panel(width: u16, has_panel: bool) -> bool {
    !has_panel || width >= LANDS_WITH_PANEL_MIN
}

/// The width the rows are laid out in: the terminal minus [`GUTTER`].
pub(super) const fn body_width(width: u16) -> u16 {
    width.saturating_sub(GUTTER)
}

/// What a change to a field in `group` costs, in an operator's words.
///
/// A prediction from the field's class, not the outcome of a specific
/// write: `watch` says `now` but can park. The row's `!` flag is the
/// durable answer. An untaught [`ApplyGroup`] falls back to `respawn`.
pub(super) const fn cost_label(group: ApplyGroup) -> &'static str {
    match group {
        ApplyGroup::Live => "now",
        ApplyGroup::NextSpawn => "next start",
        ApplyGroup::Structural => "read-only",
        ApplyGroup::NeedsRespawn | _ => "respawn",
    }
}

/// The three cell widths for a body of `width`: KEY, VALUE, COST.
///
/// A zero means the column is not drawn at all. The three always sum, with
/// their separators, to exactly `width`. COST goes first when the terminal
/// narrows: arming a field repeats its cost in the status bar. `show_lands`
/// false behaves as a narrower `width` would.
pub(super) fn widths(width: u16, show_lands: bool) -> (u16, u16, u16) {
    if show_lands && width >= FULL_WIDTH {
        let rest = width - COST_W - 2;
        let key = KEY_W.min(rest - VALUE_MIN - 2);
        (key, rest - key - 2, COST_W)
    } else if width >= VALUE_WIDTH {
        let key = KEY_W.min(width - VALUE_MIN - 2);
        (key, width - key - 2, 0)
    } else {
        (width, 0, 0)
    }
}

/// Masks a secret field's rendered value: [`UNSET`] passes through, since
/// there is nothing to hide, and anything else becomes `<set>`.
///
/// The one rule every render path here applies before a secret's value
/// reaches the screen: `field_line`'s stored cell and its `old -> new`
/// cell, `list_line`'s elements, and both halves of `pending_edit_line`.
pub(super) fn mask_secret(secret: bool, raw: String) -> String {
    if secret && raw != UNSET {
        "<set>".to_owned()
    } else {
        raw
    }
}

/// The columns `line`'s spans occupy, added rather than measured against a
/// fixed cell: a blank separator or an unselected section header is
/// shorter than the left column's own width on its own, and only the
/// panel's own starting column cares where it ends.
pub(super) fn line_columns(line: &Line<'_>) -> usize {
    line.spans
        .iter()
        .flat_map(|span| span.content.chars())
        .map(char_columns)
        .sum()
}

/// Wraps `text` at `width` columns, breaking on spaces. A single word
/// longer than `width` is placed on its own (overlong) line rather than
/// split mid-word: [`super::super::super::field::Field::help`] is prose, not data, and a rare overlong
/// word is a smaller wrong than a hyphen this module invented.
pub(super) fn wrap(text: &str, width: usize) -> Vec<String> {
    if width == 0 {
        return vec![text.to_owned()];
    }
    let mut lines = Vec::new();
    let mut current = String::new();
    for word in text.split_whitespace() {
        let word_w: usize = text_columns(word);
        let current_w: usize = text_columns(&current);
        if current.is_empty() {
            current.push_str(word);
        } else if current_w + 1 + word_w <= width {
            current.push(' ');
            current.push_str(word);
        } else {
            lines.push(std::mem::take(&mut current));
            current.push_str(word);
        }
    }
    if !current.is_empty() || lines.is_empty() {
        lines.push(current);
    }
    lines
}

/// `text`, truncated (never padded) to at most `width` columns, marking a
/// cut with a trailing `…` the way [`super::super::flock::fit`] does.
///
/// Not [`super::super::flock::fit`]: the panel's rows are prose, not a
/// fixed-width cell, so a short value stays short rather than growing
/// padded spaces across the column.
pub(super) fn clipped(text: &str, width: u16) -> String {
    let width = usize::from(width);
    let columns: usize = text_columns(text);
    if columns <= width {
        return text.to_owned();
    }
    if width == 0 {
        return String::new();
    }
    let budget = width - 1;
    let (mut out, _) = take_columns(text, budget);
    out.push('…');
    out
}

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

    #[test]
    fn the_design_target_splits_eighty_eight_and_seventy_two() {
        assert_eq!(panel_width(160), Some(72));
    }

    #[test]
    fn the_panel_goes_below_ninety_columns() {
        assert!(panel_width(90).is_some());
        assert_eq!(panel_width(89), None);
    }

    #[test]
    fn the_panel_never_drops_below_its_own_floor() {
        for width in 90..=200 {
            let panel = panel_width(width).expect("the panel is drawn above 89");
            assert!((50..=72).contains(&panel), "{panel} at {width}");
        }
    }

    #[test]
    fn the_left_column_never_falls_below_its_own_floor() {
        for width in 90..=200 {
            let panel = panel_width(width).expect("the panel is drawn above 89");
            assert!(width - panel >= 40, "{} left at {width}", width - panel);
        }
    }

    /// A panel row is prose, not a table cell: a cut row stops at its `…`
    /// rather than growing padded spaces across the column, and a row that
    /// fits is returned whole.
    #[test]
    fn clipped_cuts_to_the_budget_and_pads_nothing() {
        assert_eq!(clipped("explains the focused field", 12), "explains th…");
        // The dropped glyph is the one that would straddle the budget.
        assert_eq!(clipped("羊羊羊", 5), "羊羊…");
        assert_eq!(clipped("short", 12), "short");
        assert_eq!(clipped("anything", 0), "");
    }
}