yog 0.0.4

//! egui widget: the §11 Altitude-2 Transcript tab.
//!
//! A scrollable list over the [`rows`] projection — one line per message,
//! per model text block, per thinking block, per tool call, per tool result,
//! per live tail — each folding open to its full payload under a `▶`/`▼`
//! disclosure toggle (§11 glyph doctrine: convention passes; the glyphs are
//! jsonview's, one home for the fold vocabulary). `raw` flips the whole tab
//! to verbatim bytes for every entry (§11: "every tab has a Raw toggle
//! showing verbatim bytes").
//!
//! **The step spine runs through it** (bl-1802). Every operable commit paints
//! as a horizontal rule across the chat, at the row where that model call's
//! reading began, with the children born there hanging under it — the [`spine`]
//! submodule, which is the whole of what the `history-rail` side panel used to
//! be. Where each rule sits and which notch it is arrives derived on the
//! [`Rail`] (`rail::place`), so the line, the pin behind it and the fold it
//! cuts to are one fact rather than three.
//!
//! The fold toggle is the jsonview exception (§11 widget-split discipline): a
//! self-contained widget whose interaction is *intrinsic* owns its tested
//! click, exercised under a simulated-pointer render test, rather than
//! smearing the flip across the excluded shell.

use std::collections::HashSet;

use super::{AutoExpand, Entry, Fold, Row, Tone, Transcript, rows, spine};
use crate::jsonview::{GLYPH_COLLAPSED, GLYPH_EXPANDED, toggle_path};
use crate::rail::Rail;
use crate::theme;

/// Leaf marker for a row with nothing to fold — keeps its prefix aligned
/// under the toggles above it (jsonview's alignment convention).
const NO_FOLD_MARK: &str = "·";

/// How the chat is read: who the model turns ARE (§3.3 display name, bl-2335),
/// whether the Raw toggle is up, and which row classes arrive expanded (the
/// §4.1 knobs). One value because they are one question — *how to project this
/// transcript* — and the tab data already holds all three side by side.
#[derive(Debug, Clone, PartialEq, Eq)]
pub struct Reading {
    pub speaker: String,
    pub raw: bool,
    pub auto: AutoExpand,
}

/// Render the transcript. `folds` is the caller's RAM override set (§5.3),
/// which a toggle click mutates; `rail` is the step spine whose notches paint
/// as this chat's rules and whose cards hang under them; `selected` is the
/// caller-owned pinned-notch ephemeron a rule click flips. The return is the
/// child agent a card click asks to open — the same selection gesture the §11
/// descent-tree rows spend.
pub fn render(
    ui: &mut egui::Ui,
    transcript: &Transcript,
    reading: &Reading,
    folds: &mut HashSet<String>,
    rail: &Rail,
    selected: &mut Option<usize>,
) -> Option<String> {
    let mut follow = None;
    // §11 tail idiom, whole: the newest row is the bottom row, so the view sits
    // on the bottom edge whether or not the conversation fills it, and following
    // live output costs nothing. Scrolling up is the deliberate review gesture,
    // and it releases the anchor until the operator scrolls back down.
    crate::tail::scroll(ui, true, |ui| {
        if transcript.entries.is_empty() {
            ui.label("(no messages yet)");
            return;
        }
        if reading.raw {
            for entry in &transcript.entries {
                render_raw(ui, entry);
            }
            return;
        }
        let rules = rail.rules();
        let cohorts = crate::rail::cohorts(rail);
        for row in rows(transcript, &reading.speaker, reading.auto, folds) {
            if let Some(&index) = rules.get(&row.key) {
                // Absence of a commit = no line, unchanged since bl-929d: the
                // in-flight strip owns that interval, and the rule materializes
                // on the ordinary snapshot re-derivation once the commit does.
                if let Some(notch) = rail.notches.get(index).filter(|n| n.commit.is_some()) {
                    spine::rule(ui, index, notch, selected);
                }
                for born_here in cohorts.iter().filter(|c| c.notch == index) {
                    if let Some(id) = spine::cohort(ui, born_here) {
                        follow = Some(id);
                    }
                }
            }
            render_row(ui, &row, folds);
        }
    });
    follow
}

/// Verbatim backing bytes under a filename header — the Raw view of any entry.
/// Both seats are [`whole`]: Raw is the escape from a parse, and bytes cut at
/// the pane edge are not the bytes.
fn render_raw(ui: &mut egui::Ui, entry: &Entry) {
    whole(ui, |ui| {
        ui.monospace(&entry.name);
        ui.monospace(String::from_utf8_lossy(&entry.raw).to_string());
    });
}

/// **Show `body` entire** — the seat that must not truncate, stated locally
/// (bl-7654).
///
/// `shell::row::bounded` puts §11 rule 1's `Truncate` at every bounded panel
/// root, the centre included, and a `Ui` inherits its parent's style — so an
/// expanded payload laid in the centre was a *one-line* galley ending in `…`,
/// 67 of a 400-character answer at 420x320. The fold's whole promise is that
/// turning the triangle shows the payload, and rule 1's own body names this
/// exemption: *"a seat that must not truncate (a wrapped prose block) can
/// still say so locally"*. Taken here, deliberately, in a scope: no ambient
/// default is set, so the rows around it keep truncating, and the seat depends
/// on no ambient state either — in a seat that declares none, egui's
/// horizontal default is `Extend` and the pane's clip rect slices the run
/// mid-glyph with no ellipsis at all.
fn whole<R>(ui: &mut egui::Ui, body: impl FnOnce(&mut egui::Ui) -> R) -> R {
    ui.scope(|ui| {
        ui.style_mut().wrap_mode = Some(egui::TextWrapMode::Wrap);
        body(ui)
    })
    .inner
}

/// One line: toggle, tone-painted prefix, and the payload — inline as the
/// preview while contracted, or below in full while expanded. A row whose
/// payload already fits the line has an empty body and shows it inline
/// always, so nothing is hidden behind a fold that would reveal nothing. A
/// turn's aggregate row has no payload of its own: what its fold reveals is
/// the step rows the projection puts after it.
///
/// **One fact decides three things** (bl-7654). `row.body.is_empty()` — the
/// projection's own spelling of *"is there anything behind this?"* — says
/// whether the inline seat is the payload entire or a stand-in for a body the
/// `▶` reveals, and the seat then wraps-or-truncates, paints solid-or-faded,
/// and wears a toggle-or-the-mark on that one answer. The operator's ruling is
/// that the three never disagree: **anything hidden is hidden behind a
/// triangle**, so a run that ends in `…` always has one beside it, and a run
/// with no triangle beside it is whole.
fn render_row(ui: &mut egui::Ui, row: &Row, folds: &mut HashSet<String>) {
    let inline = row.fold == Fold::Steps || row.body.is_empty() || !row.expanded;
    // Is the inline seat standing in for something? `Fold::Steps` is not
    // abridged prose — an aggregate has no payload of its own and its preview
    // is empty — so this is exactly "a body exists and is folded away".
    let abridged = inline && !row.body.is_empty();
    ui.horizontal(|ui| {
        // §11 rule 1, stated at the row rather than inherited: the chrome of a
        // row — stripe, toggle, prefix — is one line and elides rather than
        // running off the pane, wherever the transcript is seated.
        ui.style_mut().wrap_mode = Some(egui::TextWrapMode::Truncate);
        // The §11 role stripe (bl-3acb): who this row speaks for, at the left
        // edge, from the one mapping the pending queue reads too. Every row
        // allocates the seat, so machinery rows keep the toggles aligned.
        theme::role_stripe(ui, row.role);
        toggle(ui, row, folds);
        // The label is the speaker; what it stands for hovers (bl-2335) — the
        // §11 glyph doctrine applied to a name: the glance gets the agent, the
        // hover gets the config fact behind it.
        let label = paint(ui, row.tone, &row.prefix);
        if !row.hover.is_empty() {
            label.on_hover_text(&row.hover);
        }
        if inline && !row.preview.is_empty() {
            preview(ui, &row.preview, abridged);
        }
    });
    if !inline {
        whole(ui, |ui| ui.label(&row.body));
    }
}

/// The inline payload seat. `abridged` is the row's one fact: a body is folded
/// away behind the `▶` beside this run.
///
/// **The fade means "there is more behind this", so it may only appear where
/// there is** (bl-7654). `ui.weak` was unconditional, which painted a payload
/// shown *whole* exactly as faded as a preview standing in for hidden text —
/// the surface saying the opposite of the truth precisely where it told the
/// whole truth. Inverted: complete content reads complete.
///
/// **Solidity, not a tone.** [`Tone`] is the projection's statement about what
/// kind of thing a row *is*, derived from the entry's bytes; abridgement is a
/// fact about this seat in this frame, and it flips when the operator turns
/// the triangle — so a row would have to wear two tones for one payload, which
/// is a category error. `theme::tone_solidity` is the palette's answer for
/// exactly this ("a statement that is not yet a statement"): one number, the
/// same 0.55 the §7.2 pending echo and the inbox queue spend, dimming the seat
/// rather than repainting it into a parallel palette.
fn preview(ui: &mut egui::Ui, text: &str, abridged: bool) {
    if !abridged {
        whole(ui, |ui| ui.label(text));
        return;
    }
    ui.scope(|ui| {
        ui.set_opacity(theme::tone_solidity(Tone::Weak));
        ui.label(text);
    });
}

/// The disclosure toggle, or the alignment mark when there is nothing to fold.
/// An aggregate row always folds — its steps are what it opens onto.
fn toggle(ui: &mut egui::Ui, row: &Row, folds: &mut HashSet<String>) {
    if row.fold == Fold::Payload && row.body.is_empty() {
        ui.monospace(NO_FOLD_MARK);
        return;
    }
    let glyph = if row.expanded {
        GLYPH_EXPANDED
    } else {
        GLYPH_COLLAPSED
    };
    // §11 discoverability: the glyph passes on convention, the hover says what
    // this particular fold holds.
    let hit = ui
        .add(egui::Label::new(egui::RichText::new(glyph).monospace()).sense(egui::Sense::click()))
        .on_hover_text(
            "Fold this row open or shut — open shows its whole text, shut shows the \
             first line. The two checkboxes above set which kinds open by default. No key \
             of its own: Tab reaches it, Space presses it.",
        );
    if hit.clicked() {
        toggle_path(folds, &row.key);
    }
}

/// Paint `text` in the row's tone, handing back the label so the caller can
/// hang a hover on it. An in-flight tool call pulses and pulls a near-term
/// repaint, exactly as the git_tree tool indicator does.
fn paint(ui: &mut egui::Ui, tone: Tone, text: &str) -> egui::Response {
    match tone {
        Tone::Plain => ui.label(text),
        Tone::Weak => ui.weak(text),
        Tone::Good => ui.colored_label(theme::HYDRA, text),
        Tone::Bad => ui.colored_label(theme::ICHOR, text),
        Tone::Live => ui.colored_label(theme::SPECTRE, text),
        Tone::InFlight => {
            let time = ui.ctx().input(|i| i.time);
            ui.ctx().request_repaint_after(theme::PULSE_REPAINT_DELAY);
            // Spectral, not the §11 tools-class hydra: inside a transcript the
            // contrast that matters is running-vs-finished, and hydra is
            // already the finished-ok result row two lines down.
            ui.colored_label(theme::pulse(theme::SPECTRE, time), text)
        }
    }
}