// ── Undo system ──

import { api } from './util.js';

const MAX_STACK = 30;
const stack = [];

export function pushUndo(label, restoreFn) {
    stack.push({ label, restore: restoreFn, time: Date.now() });
    if (stack.length > MAX_STACK) stack.shift();
    showHint(label);
}

export async function undo() {
    const entry = stack.pop();
    if (!entry) return;
    await entry.restore();
    await window._reloadAll();
    showHint(`undo: ${entry.label}`);
}

export function canUndo() { return stack.length > 0; }
export function lastLabel() { return stack.length ? stack[stack.length - 1].label : ''; }

// Snapshot helpers

export function snapshotCard(card) {
    return { ...card };
}

export function snapshotCards(cards) {
    return cards.map(c => ({ ...c }));
}

export function pushCardEdit(label, cardId, prevData) {
    pushUndo(label, async () => {
        await api(`api/cards/${cardId}`, { method: 'PATCH', body: prevData });
    });
}

export function pushCardDelete(label, card) {
    pushUndo(label, async () => {
        const created = await api('api/cards', { method: 'POST', body: {
            title: card.title, body: card.body, color: card.color,
            bucket_id: card.bucket_id, parent_id: card.parent_id, position: card.position,
        }});
        // Restore fields that POST doesn't accept
        if (created?.id && card.due_date) {
            await api(`api/cards/${created.id}`, { method: 'PATCH', body: { due_date: card.due_date } });
        }
    });
}

export function pushReorder(label, cards) {
    const prev = cards.map(c => ({ id: c.id, position: c.position }));
    pushUndo(label, async () => {
        await Promise.all(prev.map(p => api(`api/cards/${p.id}`, { method: 'PATCH', body: { position: p.position } })));
    });
}

export function pushBatch(label, patches) {
    // patches = [{cardId, prevData}, ...]
    pushUndo(label, async () => {
        await Promise.all(patches.map(p => api(`api/cards/${p.cardId}`, { method: 'PATCH', body: p.prevData })));
    });
}

// Toast hint
//
// Centering note: tailwind v4 compiles `-translate-x-1/2` to the *new*
// CSS `translate` property, which then stacks with any inline `transform`
// we set — the box ended up shifted ~ -100% (utility translate + JS
// transform translate both applied) and looked left-anchored. Fix: drop
// the tailwind translate utility and centre purely via the modern
// `translate` property in inline styles, which is one source of truth.
let hintTimer = null;
function showHint(text) {
    let el = document.getElementById('undo-hint');
    if (!el) {
        el = document.createElement('div');
        el.id = 'undo-hint';
        el.className = 'fixed bottom-16 left-1/2 z-[95] bg-t-surface border border-t-border px-4 py-2 text-xs font-pixel text-t-muted shadow-lg transition-all';
        el.style.translate = '-50% 0';
        document.body.appendChild(el);
    }
    el.textContent = text + '  (ctrl+z undo)';
    el.style.opacity = '1';
    el.style.translate = '-50% 0';
    clearTimeout(hintTimer);
    hintTimer = setTimeout(() => {
        el.style.opacity = '0';
        el.style.translate = '-50% 8px';
    }, 2500);
}