// Costs & splitting panel from GET /api/trips/:id/costs.
// Total + currency, breakdown by entry type, a per-user share/paid/net table
// (net colored green when owed to them, red when they owe), a settle-up list,
// and a hint when some priced entries have no payer assigned.
import { el } from '../dom.js';
import { typeInfo, formatMoney } from '../format.js';

// byType's "expense" key isn't an entry type (typeInfo only knows
// activity/stay/transport/flight/rental/note), so it'd otherwise fall back to
// a bare bullet + the raw key. Give it its own icon/label to match the
// Expenses card.
function byTypeInfo(type) {
  if (type === 'expense') return { icon: '💸', label: 'Expenses', color: '#64748b' };
  return typeInfo(type);
}

export function renderCosts(tctx) {
  const costs = tctx.costs || {};
  const currency = costs.currency || (tctx.trip.trip && tctx.trip.trip.currency) || 'USD';
  const total = costs.totalCost || 0;
  const perUser = costs.perUser || [];
  const byType = costs.byType || {};
  const settlements = costs.settlements || [];
  const unassigned = costs.unassigned || 0;

  const money = (n) => formatMoney(n, currency);

  const nameById = new Map(perUser.map((u) => [u.userId, u.displayName]));
  const memberName = (id) => {
    if (nameById.has(id)) return nameById.get(id);
    const m = (tctx.trip.members || []).find((x) => x.id === id);
    return m ? m.display_name : `user ${id}`;
  };

  const section = el('section', { class: 'card costs-section' });
  section.appendChild(
    el(
      'div',
      { class: 'section-head' },
      el('h2', {}, 'Costs'),
      el('p', { class: 'muted' }, 'Who owes whom, split across the trip.'),
    ),
  );

  const hasCosts = total > 0 || perUser.some((u) => u.share || u.paid);
  if (!hasCosts) {
    section.appendChild(
      el(
        'div',
        { class: 'costs-empty' },
        el('div', { class: 'empty-icon' }, '💰'),
        el('p', {}, 'No costs tracked yet.'),
        el('p', { class: 'muted' }, 'Add a price to an entry to start splitting expenses.'),
      ),
    );
    return section;
  }

  // Total.
  section.appendChild(
    el(
      'div',
      { class: 'costs-total' },
      el('span', { class: 'costs-total-value' }, money(total)),
      el('span', { class: 'costs-total-label' }, 'total trip cost'),
    ),
  );

  if (unassigned > 0) {
    section.appendChild(
      el(
        'div',
        { class: 'costs-warn' },
        `⚠ ${money(unassigned)} of priced entries have no payer assigned — assign payers to settle them.`,
      ),
    );
  }

  // Breakdown by type.
  const typeKeys = Object.keys(byType);
  if (typeKeys.length) {
    const bt = el('div', { class: 'cost-block' }, el('h3', {}, 'By type'));
    for (const type of typeKeys) {
      const info = byTypeInfo(type);
      bt.appendChild(
        el(
          'div',
          { class: 'bytype-row' },
          el('span', { class: 'bytype-dot', style: { background: info.color } }),
          el('span', { class: 'bytype-name' }, `${info.icon} ${info.label}`),
          el('span', { class: 'bytype-amount' }, money(byType[type])),
        ),
      );
    }
    section.appendChild(bt);
  }

  // Per-user table.
  if (perUser.length) {
    const table = el(
      'table',
      { class: 'cost-table' },
      el(
        'thead',
        {},
        el(
          'tr',
          {},
          el('th', {}, 'Member'),
          el('th', { class: 'num' }, 'Share'),
          el('th', { class: 'num' }, 'Paid'),
          el('th', { class: 'num' }, 'Net'),
        ),
      ),
      el(
        'tbody',
        {},
        ...perUser.map((u) => {
          const net = u.net || 0;
          const netClass = net > 0.004 ? 'net-pos' : net < -0.004 ? 'net-neg' : 'net-zero';
          const netText = `${net > 0 ? '+' : ''}${money(net)}`;
          return el(
            'tr',
            {},
            el('td', {}, u.displayName),
            el('td', { class: 'num' }, money(u.share || 0)),
            el('td', { class: 'num' }, money(u.paid || 0)),
            el('td', { class: `num ${netClass}` }, netText),
          );
        }),
      ),
    );
    section.appendChild(el('div', { class: 'cost-block' }, el('h3', {}, 'Per person'), table));
  }

  // Settle-up list.
  const settleBlock = el('div', { class: 'cost-block' }, el('h3', {}, 'Settle up'));
  if (!settlements.length) {
    settleBlock.appendChild(el('p', { class: 'muted' }, 'All square — no transfers needed.'));
  } else {
    for (const s of settlements) {
      settleBlock.appendChild(
        el(
          'div',
          { class: 'settle-row' },
          el('span', { class: 'settle-from' }, memberName(s.fromUserId)),
          el('span', { class: 'settle-arrow' }, '→'),
          el('span', { class: 'settle-to' }, memberName(s.toUserId)),
          el('span', { class: 'settle-amount' }, money(s.amount)),
        ),
      );
    }
  }
  section.appendChild(settleBlock);

  return section;
}