lernie 0.1.86

//! **The start half of the composer**: where a conversation is begun.
//!
//! It is a **mode of the composer and not a pane beside it**, and that is this
//! ball's one layout decision. A wall with no conversation selected already had
//! a box that refused — *pick a workspace and a conversation to say anything* —
//! and that refusal was the start's own case wearing a sentence: there is
//! nothing to say to, so the thing to do is begin one. A second box would be
//! the same box twice, each with its own Enter, on a face that is four panes
//! wide; upstream states the rule as *one box, one Enter* and it is worth more
//! here than there.
//!
//! So the composer is one control with two subjects, decided by what is
//! selected and by nothing else:
//!
//! - no wall aimed at → nothing to say and nothing to begin;
//! - a wall, no conversation → **this**, the start;
//! - a wall and a conversation → the deposit.
//!
//! **A start in flight paints its sentence instead of the box**, which is how a
//! second start is refused: not by a disarmed control, but by there being no
//! control. The receipt is the one state that paints the sentence *and* the box
//! — the minted name stays readable while the operator begins the next one.
//!
//! # One composer, in both of its modes (DESIGN §4.39)
//!
//! *Being* the same control and *looking* like it are two things, and until
//! bl-b3c3 this mode only had the first: it painted a one-line
//! [`crate::ui::theme::paint::field`] and a button beside it while the deposit
//! painted [`crate::ui::theme::paint::composer`] — the field
//! [`crate::ui::theme::COMPOSER_ROWS`] tall with the act inside it — so the
//! pane's focal element shrank to a bar whenever nothing was selected. It is
//! now laid through the same shape at the same rows, with [`START`] inside the
//! field where the deposit says `send`, and under it the same offers row
//! carrying what applies to a start ([`super::offers::starting`]).
//!
//! **What the row does NOT carry is the rule, not an omission.** `records…`,
//! `interrupt`, `stop`, `nudge` and the `…` strip are acts on a conversation's
//! turn or on a conversation as an object, and there is neither — so they are
//! absent rather than greyed, by the offers row's own rule that only what is
//! offered is on the row.

use crate::ui::{Aim, Fill, Model};

/// **What the box asks for, naming the wall the Enter begins on** (§4.42
/// item 3; bl-9031). A start's goal is what the conversation is *for*, which
/// is a different question from what to say to one that exists; and with two
/// walls on one engine the box is the one place the operator is looking when
/// the Enter decides where the conversation lands. While `/plan` has said the
/// next start is a plan, the hint's tail says so instead.
pub fn goal(wall: &str, plan: bool) -> String {
    let tail = if plan {
        "begun as a plan"
    } else {
        "Enter begins it"
    };
    format!("what this conversation on {wall} is for — {tail}")
}

/// Paint the start composer and take what it was given.
pub fn render(ui: &mut egui::Ui, model: &mut Model, aim: &Aim) {
    // **Taken before anything is painted**, so a start in flight — which
    // paints its sentence and no box — spends the request rather than holding
    // it for whichever frame paints a box next (`crate::ui::model::fill`).
    let wanted = model.filling() == Some(Fill::Goal);
    if let Some(held) = model.start.clone() {
        ui.label(held.line());
        if held.outstanding() {
            return;
        }
    }
    // **The same shape as the deposit, at the same rows** (§4.39) — including
    // the rows the operator dragged the panel's top edge to, because one box
    // in two modes is one box: the act
    // stands inside the field rather than beside it, and its word is the only
    // thing that differs. The start has nothing to glow about — a glow is the
    // selected conversation asking, and there is no conversation.
    //
    // **Both halves of the start ride this one control** (`crate::ui::act`):
    // the click composes `prepare`, and the `prompt` that finishes it is fired
    // by the frame when the engine's reply lands (`crate::ui::model::start`),
    // from no widget at all. A walk over the accessibility tree can only ever
    // see the control that begins the pair, so both tokens ride it.
    let slashed = crate::ui::slash::parsed(&model.draft).is_some();
    let entry = crate::ui::theme::paint::prompt(
        ui,
        egui::Id::new(crate::ui::keys::BOX_ID),
        &mut model.draft,
        &super::hint(
            ui,
            &goal(&aim.address, model.plan),
            &crate::ui::chat::panel::WAYS,
        ),
        None,
    );
    crate::ui::act::tag(&entry, &[crate::verbs::PREPARE, crate::verbs::PROMPT]);
    // **The `+` on an engine's row lands the caret here** (§4.39): the control
    // is on the other column and the box is this one, so what crosses between
    // them is a request the frame that paints the box answers.
    if wanted {
        entry.request_focus();
    }
    // Enter begins it, as it always did — through the deposit's own read, now
    // that the box is the deposit's own box (`super::entered`).
    if slashed {
        return;
    }
    if super::entered(ui, &entry) {
        model.stage(&aim.address);
    }
}

#[cfg(test)]
mod tests;