import { t } from '../../i18n/index.mjs';

export function createReaderScroll({

renderState,

session,

motion,

translationState,

preferences,

activity,

feedback,

view,

actions,

}) {

function showScrollbar(event) {

const el = event?.currentTarget;

if (!el) return;

el.dataset.scrolling = 'true';

clearTimeout(renderState.scrollbarTimers.get(el));

renderState.scrollbarTimers.set(

el,

setTimeout(() => {

delete el.dataset.scrolling;

renderState.scrollbarTimers.delete(el);

}, 800),

);

}

function scrolling(event) {

actions.rootActions.immersiveScroll();

if (session.restoringView.value || motion.fitResizing) return;

activity.performanceRecorder.scroll();

const el = view.reader.value,

now = performance.now(),

position = view.direction.value === 'horizontal' ? el?.scrollLeft : el?.scrollTop,

extent = view.direction.value === 'horizontal' ? el?.clientWidth : el?.clientHeight;

if (translationState.lastTranslationScroll && position !== undefined) {

const delta = position - translationState.lastTranslationScroll.position;

if (Math.abs(delta) > 1) translationState.readingDirection = Math.sign(delta);

translationState.translationMoving =

Math.abs(delta) > extent * 0.6 ||

Math.abs(delta) / Math.max(16, now - translationState.lastTranslationScroll.time) >

extent / 700;

}

translationState.lastTranslationScroll = { position: position || 0, time: now };

const viewport = actions.readerViewport.viewportPages();

if (!motion.pinching.value) actions.translationQueue.schedulePages();

actions.readerViewport.scheduleViewport(viewport);

actions.readingPosition.scheduleReadingSave();

showScrollbar(event);

actions.readerPreview.interruptPreview();

actions.readerInputs.showNavigator();

feedback.reading.value = t('reading.scrolling');

clearTimeout(translationState.timer);

translationState.timer = setTimeout(() => {

if (!motion.pinching.value) settle();

}, 180);

}

function settle() {

translationState.translationMoving = false;

if (!activity.foreground.value && preferences.translationMode.value !== 'full') return;

if (!renderState.previewScrolling && !motion.pinching.value) {

for (const n of renderState.visiblePages) {

const p = session.pages.value[n - 1];

if (p) renderState.pendingPreview.set(n, p);

}

actions.readerPreview.flushPreview();

}

if (!activity.foreground.value && preferences.translationMode.value !== 'full') return;

const p = session.pages.value[view.active.value - 1];

if (!p) return;

feedback.reading.value = t('reading.readingPage', { page: p.number });

p.dwell++;

actions.translationQueue.schedulePages();

}

return { showScrollbar, scrolling, settle };

}