import '../styles/main.scss';
import {
    Chart,
    BarController,
    BarElement,
    CategoryScale,
    LinearScale,
    Tooltip,
} from 'chart.js';
import { createTranslator } from './utils.js';

Chart.register(BarController, BarElement, CategoryScale, LinearScale, Tooltip);

const t = createTranslator('Statistics');
const months = window.Statistics.monthsShort;
const weekdays = window.Statistics.weekdaysShort;

let chart = null;
let cachedData = null;

function formatLabel(key, groupBy) {
    if (groupBy === 'month') {
        const [year, month] = key.split('-');
        return months[parseInt(month, 10) - 1] + ' ' + year.slice(2);
    }
    if (groupBy === 'week') {
        const week = key.split('-')[1];
        return t('weekShort') + ' ' + parseInt(week, 10);
    }
    const d = new Date(key + 'T00:00:00');
    const dayOfWeek = weekdays[(d.getDay() + 6) % 7];
    const day = d.getDate();
    const mon = months[d.getMonth()];
    return dayOfWeek + ' ' + day + '. ' + mon;
}

function formatHours(value) {
    const h = Math.floor(value);
    const m = Math.round((value - h) * 60);
    return h + ':' + String(m).padStart(2, '0');
}

function formatCurrency(value) {
    return value.toLocaleString('de-DE', { minimumFractionDigits: 2, maximumFractionDigits: 2 }) + ' €';
}

function getWeekNumber(dateStr) {
    const d = new Date(dateStr + 'T00:00:00');
    const dayNum = d.getDay() || 7;
    d.setDate(d.getDate() + 4 - dayNum);
    const yearStart = new Date(d.getFullYear(), 0, 1);
    return Math.ceil((((d - yearStart) / 86400000) + 1) / 7);
}

function getBrandColor() {
    return getComputedStyle(document.documentElement)
        .getPropertyValue('--color-primary').trim() || '#4a90d9';
}

function renderChart(data, metric) {
    const canvas = document.getElementById('stats-chart');
    if (!canvas) return;

    if (chart) {
        chart.destroy();
        chart = null;
    }

    const isRevenue = metric === 'revenue';
    const brandColor = getBrandColor();
    const greyColor = 'rgba(170, 184, 198, 0.55)';
    const labels = data.labels.map(l => formatLabel(l, data.groupBy));

    const dataset1 = isRevenue ? data.billableRevenue : data.billable;
    const dataset2 = isRevenue ? data.nonBillableRevenue : data.nonBillable;

    let weekBands = [];
    if (data.groupBy === 'day') {
        let currentWeek = null;
        let bandStart = null;
        let bandIdx = 0;

        data.labels.forEach((key, i) => {
            const wk = getWeekNumber(key);
            if (wk !== currentWeek) {
                if (currentWeek !== null && bandIdx % 2 === 1) {
                    weekBands.push([bandStart, i - 1]);
                }
                currentWeek = wk;
                bandStart = i;
                bandIdx++;
            }
        });
        if (bandIdx % 2 === 1) {
            weekBands.push([bandStart, data.labels.length - 1]);
        }
    }

    chart = new Chart(canvas, {
        type: 'bar',
        data: {
            labels,
            datasets: [
                {
                    label: t('billable'),
                    data: dataset1,
                    backgroundColor: brandColor,
                    borderRadius: 3,
                    borderSkipped: false,
                },
                {
                    label: t('nonBillable'),
                    data: dataset2,
                    backgroundColor: greyColor,
                    borderRadius: 3,
                    borderSkipped: false,
                },
            ],
        },
        options: {
            responsive: true,
            maintainAspectRatio: false,
            animation: {
                duration: 600,
                easing: 'easeOutQuart',
            },
            interaction: {
                mode: 'index',
                intersect: false,
            },
            plugins: {
                legend: { display: false },
                tooltip: {
                    backgroundColor: '#1a2a3a',
                    titleFont: { weight: '600' },
                    bodyFont: { size: 13 },
                    padding: 10,
                    cornerRadius: 6,
                    callbacks: {
                        label(ctx) {
                            if (isRevenue) {
                                return ctx.dataset.label + ': ' + formatCurrency(ctx.parsed.y);
                            }
                            return ctx.dataset.label + ': ' + formatHours(ctx.parsed.y) + ' ' + t('hours');
                        },
                    },
                },
            },
            scales: {
                x: {
                    grid: { display: false },
                    ticks: {
                        font: { size: 11 },
                        maxRotation: data.groupBy === 'day' ? 45 : 0,
                        autoSkip: true,
                        autoSkipPadding: 8,
                    },
                },
                y: {
                    beginAtZero: true,
                    grid: { color: 'rgba(0,0,0,0.06)' },
                    ticks: {
                        font: { size: 11 },
                        callback(value) {
                            if (isRevenue) return formatCurrency(value);
                            return formatHours(value);
                        },
                    },
                },
            },
        },
        plugins: data.groupBy === 'day' ? [{
            id: 'weekBands',
            beforeDraw(chartInstance) {
                const { ctx, chartArea, scales } = chartInstance;
                if (!chartArea || weekBands.length === 0) return;

                ctx.save();
                ctx.fillStyle = 'rgba(0, 0, 0, 0.03)';
                weekBands.forEach(([start, end]) => {
                    const x1 = scales.x.getPixelForValue(start) - (scales.x.getPixelForValue(1) - scales.x.getPixelForValue(0)) / 2;
                    const x2 = scales.x.getPixelForValue(end) + (scales.x.getPixelForValue(1) - scales.x.getPixelForValue(0)) / 2;
                    ctx.fillRect(x1, chartArea.top, x2 - x1, chartArea.bottom - chartArea.top);
                });
                ctx.restore();
            },
        }] : [],
    });
}

async function loadAndRender(range, metric, userId) {
    const wrap = document.getElementById('stats-chart-wrap');
    if (!wrap) return;

    let url = '/api/statistics?range=' + encodeURIComponent(range);
    if (userId) {
        url += '&userId=' + encodeURIComponent(userId);
    }

    try {
        const res = await fetch(url);
        if (!res.ok) throw new Error(res.statusText);
        cachedData = await res.json();
        renderChart(cachedData, metric);
    } catch {
        wrap.innerHTML = '<p class="statistics-error">' + t('errorLoad') + '</p>';
    }
}

function getSelectedUserId() {
    const el = document.getElementById('stats-user-select');
    return el ? el.value : '';
}

document.addEventListener('DOMContentLoaded', () => {
    const rangeSelect = document.getElementById('stats-range-select');
    const metricSelect = document.getElementById('stats-metric-select');
    const userSelect = document.getElementById('stats-user-select');
    if (!rangeSelect || !metricSelect) return;

    loadAndRender(rangeSelect.value, metricSelect.value, getSelectedUserId());

    rangeSelect.addEventListener('change', () => {
        loadAndRender(rangeSelect.value, metricSelect.value, getSelectedUserId());
    });

    if (userSelect) {
        userSelect.addEventListener('change', () => {
            loadAndRender(rangeSelect.value, metricSelect.value, getSelectedUserId());
        });
    }

    metricSelect.addEventListener('change', () => {
        if (cachedData) {
            renderChart(cachedData, metricSelect.value);
        }
    });
});