/* global usScheduler */
(function () {
    'use strict';

    const app = document.getElementById('us-booking-app');
    if (!app) return;

    const slotList    = document.getElementById('us-slot-list');
    const confirm     = document.getElementById('us-booking-confirmation');
    const errorBox    = document.getElementById('us-booking-error');
    const { restUrl, nonce } = usScheduler;

    function apiFetch(path, options = {}) {
        return fetch(restUrl + path, {
            ...options,
            headers: {
                'Content-Type': 'application/json',
                'X-WP-Nonce': nonce,
                ...(options.headers || {}),
            },
        }).then(async (res) => {
            const data = await res.json();
            if (!res.ok) throw new Error(data.message || 'Request failed');
            return data;
        });
    }

    function showError(message) {
        errorBox.textContent = message;
        errorBox.style.display = 'block';
    }

    function dayKey(dt) {
        return String(dt).slice(0, 10);
    }

    function timeOf(dt) {
        return String(dt).slice(11, 16);
    }

    function dayLabel(key) {
        const date = new Date(key + 'T00:00:00');
        if (Number.isNaN(date.getTime())) return key;
        return date.toLocaleDateString(undefined, {
            weekday: 'long', year: 'numeric', month: 'long', day: 'numeric',
        });
    }

    function groupByDay(slots) {
        const groups = new Map();
        slots.forEach((slot) => {
            const key = dayKey(slot.start_dt);
            if (!groups.has(key)) groups.set(key, []);
            groups.get(key).push(slot);
        });
        return [...groups.entries()].sort((a, b) => a[0].localeCompare(b[0]));
    }

    // Agenda-style calendar: available slots grouped by day. The richer booking
    // UX (offering selection, intake questions, policy acceptance) lands with the
    // booking-flow work.
    function renderSlots(slots) {
        if (!slots.length) {
            slotList.innerHTML = '<p>No available lesson slots at this time.</p>';
            return;
        }

        slotList.innerHTML = groupByDay(slots).map(([key, daySlots]) => `
            <div class="us-day">
                <h3 class="us-day-heading">${escHtml(dayLabel(key))}</h3>
                ${daySlots.map((slot) => `
                    <div class="us-slot">
                        <span>${escHtml(timeOf(slot.start_dt))}–${escHtml(timeOf(slot.end_dt))} (${escHtml(String(slot.duration_minutes))} min)</span>
                        <button data-slot-id="${slot.id}" class="us-book-btn">Book</button>
                    </div>
                `).join('')}
            </div>
        `).join('');

        slotList.querySelectorAll('.us-book-btn').forEach((btn) => {
            btn.addEventListener('click', () => bookSlot(Number(btn.dataset.slotId)));
        });
    }

    function escHtml(str) {
        return String(str)
            .replace(/&/g, '&amp;')
            .replace(/</g, '&lt;')
            .replace(/>/g, '&gt;')
            .replace(/"/g, '&quot;');
    }

    function bookSlot(slotId) {
        errorBox.style.display = 'none';

        apiFetch('bookings', {
            method: 'POST',
            body: JSON.stringify({ slot_id: slotId }),
        })
            .then(() => {
                slotList.style.display = 'none';
                confirm.style.display  = 'block';
            })
            .catch((err) => showError(err.message));
    }

    apiFetch('availability')
        .then(renderSlots)
        .catch((err) => showError(err.message));
}());