const MOSCOW_TIMEZONE = 'Europe/Moscow';
const WEEKDAYS = ['Понедельник', 'Вторник', 'Среда', 'Четверг', 'Пятница', 'Суббота', 'Воскресенье'];
const MONTHS = ['января', 'февраля', 'марта', 'апреля', 'мая', 'июня', 'июля', 'августа', 'сентября', 'октября', 'ноября', 'декабря'];
const SLOT_MINUTES = 15;
const START_HOUR = 8;
const END_HOUR = 20;
const PIXELS_PER_MINUTE = 0.8;

const CATPPUCCIN_MOCHA = {
    rosewater: '#f5e0dc',
    flamingo: '#f2cdcd',
    pink: '#f5c2e7',
    mauve: '#cba6f7',
    red: '#f38ba8',
    maroon: '#eba0ac',
    peach: '#fab387',
    yellow: '#f9e2af',
    green: '#a6e3a1',
    teal: '#94e2d5',
    sky: '#89dceb',
    sapphire: '#74c7ec',
    blue: '#89b4fa',
    lavender: '#b4befe'
};
const DEFAULT_EVENT_COLOR = 'blue';

function eventColorHex(colorKey) {
    return CATPPUCCIN_MOCHA[colorKey] || CATPPUCCIN_MOCHA[DEFAULT_EVENT_COLOR];
}

let currentWeekStart = null;

function getMoscowDateString() {
    const formatter = new Intl.DateTimeFormat('en-CA', {
        timeZone: MOSCOW_TIMEZONE,
        year: 'numeric',
        month: '2-digit',
        day: '2-digit'
    });
    return formatter.format(new Date());
}

function parseISODate(value) {
    const [year, month, day] = value.split('-').map(Number);
    return new Date(year, month - 1, day);
}

function formatISODate(date) {
    return `${date.getFullYear()}-${String(date.getMonth() + 1).padStart(2, '0')}-${String(date.getDate()).padStart(2, '0')}`;
}

function addDays(dateStr, days) {
    const date = parseISODate(dateStr);
    date.setDate(date.getDate() + days);
    return formatISODate(date);
}

function startOfWeek(dateStr = null) {
    const base = parseISODate(dateStr || getMoscowDateString());
    const jsDay = base.getDay();
    const diff = jsDay === 0 ? -6 : 1 - jsDay;
    base.setDate(base.getDate() + diff);
    return formatISODate(base);
}

function timeToMinutes(time) {
    const [hour, minute] = time.split(':').map(Number);
    return hour * 60 + minute;
}

function formatDate(dateStr) {
    const date = parseISODate(dateStr);
    return `${WEEKDAYS[(date.getDay() + 6) % 7]}, ${date.getDate()} ${MONTHS[date.getMonth()]}`;
}

function calculateEndTime(startTime, durationMin) {
    const [hour, minute] = startTime.split(':').map(Number);
    const totalMinutes = hour * 60 + minute + durationMin;
    const endHour = Math.floor(totalMinutes / 60);
    const endMinute = totalMinutes % 60;
    return `${String(endHour).padStart(2, '0')}:${String(endMinute).padStart(2, '0')}`;
}

function renderDay(container, titleEl, dateStr, items, options = {}) {
    let titleText = formatDate(dateStr);
    if (options.today) {
        titleText = `Сегодня, ${titleText.toLowerCase()}`;
    } else if (options.tomorrow) {
        titleText = `Завтра, ${titleText.toLowerCase()}`;
    }
    titleEl.textContent = titleText;

    const tasks = items.filter((item) => item.kind === 'task');
    const events = items
        .filter((item) => item.kind === 'event')
        .sort((a, b) => a.start_time.localeCompare(b.start_time));

    if (!tasks.length && !events.length) {
        container.innerHTML = '<div class="empty-message">На этот день расписания нет.</div>';
        return;
    }

    const tasksHtml = tasks.length ? `
        <div class="tasks-list">
            ${tasks.map((task) => `<div class="task-item">${task.repeat_weekly ? 'Каждую неделю: ' : ''}${escapeHtml(task.title)}</div>`).join('')}
        </div>
    ` : '';

    const eventsHtml = events.length ? `
        <div class="events-list">
            ${events.map((event) => `
                <div class="event-item" style="--event-color:${eventColorHex(event.color)};">
                    <span class="event-time">${event.start_time}-${calculateEndTime(event.start_time, event.duration_min)}</span>
                    <span class="event-title">${escapeHtml(event.title)}</span>
                </div>
            `).join('')}
        </div>
    ` : '';

    container.innerHTML = `${tasksHtml}${eventsHtml}`;
}

function escapeHtml(value) {
    return String(value)
        .replaceAll('&', '&amp;')
        .replaceAll('<', '&lt;')
        .replaceAll('>', '&gt;')
        .replaceAll('"', '&quot;')
        .replaceAll("'", '&#39;');
}

async function loadSchedule() {
    const today = getMoscowDateString();
    const tomorrow = addDays(today, 1);

    const response = await fetch(`/api/schedule?from_date=${today}&to_date=${tomorrow}`);
    if (!response.ok) {
        throw new Error('Не удалось загрузить расписание');
    }

    const data = await response.json();
    renderDay(
        document.getElementById('today-content'),
        document.getElementById('today-title'),
        today,
        data.items.filter((item) => item.date === today),
        { today: true }
    );
    renderDay(
        document.getElementById('tomorrow-content'),
        document.getElementById('tomorrow-title'),
        tomorrow,
        data.items.filter((item) => item.date === tomorrow),
        { tomorrow: true }
    );
}

function getWeekDates() {
    return Array.from({ length: 7 }, (_, index) => addDays(currentWeekStart, index));
}

function renderTimeline(dateStr, events) {
    const hours = Array.from({ length: END_HOUR - START_HOUR + 1 }, (_, index) => START_HOUR + index);
    return `
        <div class="timeline">
            ${hours.map((hour, index) => `
                <div class="timeline-hour" style="top:${index * 60 * PIXELS_PER_MINUTE}px;">
                    <span class="timeline-hour-label">${String(hour).padStart(2, '0')}:00</span>
                </div>
            `).join('')}
            ${events.map((event) => renderEventBlock(event)).join('')}
        </div>
    `;
}

function renderEventBlock(event) {
    const startMinutes = timeToMinutes(event.start_time) - START_HOUR * 60;
    const top = Math.max(0, startMinutes * PIXELS_PER_MINUTE);
    const height = Math.max(42, event.duration_min * PIXELS_PER_MINUTE);
    const endTime = calculateEndTime(event.start_time, event.duration_min);
    return `
        <article class="event-block ${event.repeat_weekly ? 'recurring' : ''}" style="top:${top}px;height:${height}px;--event-color:${eventColorHex(event.color)};">
            <div class="event-line">
                <span class="event-time">${event.start_time}–${endTime}</span>
                <span class="event-title">${escapeHtml(event.title)}</span>
            </div>
        </article>
    `;
}

async function loadWeekSchedule() {
    if (!currentWeekStart) {
        currentWeekStart = startOfWeek();
    }

    const dates = getWeekDates();
    const fromDate = dates[0];
    const toDate = dates[dates.length - 1];
    const today = getMoscowDateString();

    const response = await fetch(`/api/schedule?from_date=${fromDate}&to_date=${toDate}`);
    if (!response.ok) {
        throw new Error('Не удалось загрузить расписание');
    }

    const data = await response.json();
    const grid = document.getElementById('week-grid');

    grid.innerHTML = dates.map((dateStr) => {
        const dayItems = data.items.filter((item) => item.date === dateStr);
        const tasks = dayItems.filter((item) => item.kind === 'task');
        const events = dayItems
            .filter((item) => item.kind === 'event')
            .sort((a, b) => a.start_time.localeCompare(b.start_time));

        return `
            <section class="week-day-card ${dateStr === today ? 'is-today' : ''}">
                <div class="week-day-header">${formatDate(dateStr)}</div>
                <div class="week-task-list">
                    ${tasks.map((task) => `<div class="week-task-item">${escapeHtml(task.title)}</div>`).join('')}
                </div>
                ${renderTimeline(dateStr, events)}
            </section>
        `;
    }).join('');

    document.getElementById('week-range').textContent = `${formatDate(dates[0])} - ${formatDate(dates[dates.length - 1])}`;
}

function setActiveTab(tab) {
    const isWeek = tab === 'week';
    document.getElementById('view-daily').hidden = isWeek;
    document.getElementById('view-week').hidden = !isWeek;
    document.getElementById('tab-daily').classList.toggle('is-active', !isWeek);
    document.getElementById('tab-week').classList.toggle('is-active', isWeek);
}

document.addEventListener('DOMContentLoaded', () => {
    document.getElementById('tab-daily').addEventListener('click', () => setActiveTab('daily'));
    document.getElementById('tab-week').addEventListener('click', async () => {
        setActiveTab('week');
        try {
            await loadWeekSchedule();
        } catch (error) {
            console.error(error);
        }
    });
    document.getElementById('week-prev').addEventListener('click', async () => {
        currentWeekStart = addDays(currentWeekStart, -7);
        await loadWeekSchedule().catch((error) => console.error(error));
    });
    document.getElementById('week-next').addEventListener('click', async () => {
        currentWeekStart = addDays(currentWeekStart, 7);
        await loadWeekSchedule().catch((error) => console.error(error));
    });
});

loadSchedule().catch((error) => console.error(error));
setInterval(() => loadSchedule().catch((error) => console.error(error)), 5 * 60 * 1000);