//! Blob-layout migration strip: a thin, cancellable progress row above the footer.
//!
//! Shown only while the background migration is relocating blobs from the legacy
//! flat store root into hash-prefix shards. Deliberately a strip and not a modal or
//! a full-screen mode: the migration auto-starts at vault open rather than being
//! asked for, and the library stays completely usable while it runs, because reads
//! resolve both layouts. Seizing the window for it would be the wrong trade.
//!
//! Cancelling is honest here. The sweep is resumable and records nothing until a
//! pass verifies the root is clean, so stopping defers the remainder to the next
//! open instead of abandoning or half-applying it.

use egui;

use super::theme;
use crate::state::BrowserState;

/// Draw the migration strip. No-op when no migration is running.
pub fn draw_layout_strip(ui: &mut egui::Ui, state: &mut BrowserState) {
    let Some(progress) = state.layout_migration else {
        return;
    };

    ui.add_space(theme::space::hair());
    ui.horizontal(|ui| {
        ui.label(
            egui::RichText::new("Optimising storage layout")
                .small()
                .color(theme::content_secondary()),
        );
        ui.label(
            egui::RichText::new(format!("{} / {} files", progress.completed, progress.total))
                .small()
                .color(theme::content_muted()),
        );

        // The button is laid out first from the right so the bar takes the
        // remaining width instead of pushing the button off the row.
        ui.with_layout(egui::Layout::right_to_left(egui::Align::Center), |ui| {
            if ui
                .small_button("Pause")
                .on_hover_text("Stop for now. Resumes the next time this vault opens.")
                .clicked()
            {
                if let Err(e) = state.backend.cancel_layout_migration() {
                    tracing::warn!("failed to cancel layout migration: {e}");
                }
                // Clear the strip immediately rather than waiting for the
                // worker's terminal event: the click has to feel like it did
                // something, and the Complete event that follows sets the status
                // line and would clear this anyway.
                state.layout_migration = None;
            }
            ui.add(
                egui::ProgressBar::new(progress.fraction())
                    .desired_height(theme::space::peer())
                    .show_percentage(),
            );
        });
    });
    ui.add_space(theme::space::hair());
}