const { request } = require("undici");
const { DateTime } = require("luxon");

async function fetchGoAccessJson(url) {
    const res = await request(url, { method: "GET" });
    if (res.statusCode < 200 || res.statusCode >= 300) {
        throw new Error(`HTTP ${res.statusCode}`);
    }
    return res.body.json();
}

function crawlerRatios(data) {
    const browsers = data.browsers?.data || [];
    const crawler = browsers.find((entry) => entry.data === "Crawlers");
    if (!crawler) return { hits: 0, visitors: 0 };

    const totalHits = (browsers.reduce((sum, entry) => sum + (entry.hits?.count || 0), 0)) || 0;
    const totalVisitors = (browsers.reduce((sum, entry) => sum + (entry.visitors?.count || 0), 0)) || 0;

    const hitRatio = totalHits > 0 ? Math.min(1, (crawler.hits?.count || 0) / totalHits) : 0;
    const visitorRatio = totalVisitors > 0 ? Math.min(1, (crawler.visitors?.count || 0) / totalVisitors) : 0;

    return { hits: hitRatio, visitors: visitorRatio };
}

function groupVisitsByMonth(data, { adjustCrawlers = true } = {}) {
    const entries = data.visitors?.data || [];
    const ratios = adjustCrawlers ? crawlerRatios(data) : { hits: 0, visitors: 0 };
    const months = new Map();

    for (const entry of entries) {
        const dateStr = entry.data;
        if (!/^[0-9]{8}$/.test(dateStr)) continue;
        const year = dateStr.slice(0, 4);
        const month = dateStr.slice(4, 6);
        const day = dateStr.slice(6, 8);
        const key = `${year}-${month}`;

        const hits = entry.hits?.count || 0;
        const visitors = entry.visitors?.count || 0;

        const current = months.get(key) || { hits: 0, visitors: 0, from: null, to: null };
        const isoDate = `${year}-${month}-${day}`;

        current.hits += hits;
        current.visitors += visitors;
        if (!current.from || isoDate < current.from) current.from = isoDate;
        if (!current.to || isoDate > current.to) current.to = isoDate;

        months.set(key, current);
    }

    const adjust = (value, ratio) => {
        if (!adjustCrawlers) return value;
        const scaled = value * (1 - ratio);
        return Math.max(0, Math.round(scaled));
    };

    const sorted = Array.from(months.entries())
        .sort((a, b) => a[0].localeCompare(b[0]))
        .map(([key, value]) => ({
            month: key,
            from: value.from,
            to: value.to,
            hits: adjust(value.hits, ratios.hits),
            visitors: adjust(value.visitors, ratios.visitors),
        }));

    return sorted;
}

function aggregateLastNDays(data, days = 30, { adjustCrawlers = true } = {}) {
    const entries = data.visitors?.data || [];
    if (!entries.length || days <= 0) {
        return { from: null, to: null, hits: 0, visitors: 0 };
    }

    const valid = entries.filter((entry) => /^[0-9]{8}$/.test(entry.data));
    if (valid.length === 0) {
        return { from: null, to: null, hits: 0, visitors: 0 };
    }

    const sorted = valid.slice().sort((a, b) => a.data.localeCompare(b.data));
    const last = sorted[sorted.length - 1];
    const end = DateTime.fromFormat(last.data, "yyyyLLdd", { zone: "UTC" });
    if (!end.isValid) {
        return { from: null, to: null, hits: 0, visitors: 0 };
    }

    const start = end.minus({ days: days - 1 });

    let from = null;
    let to = null;
    let hits = 0;
    let visitors = 0;

    for (const entry of sorted) {
        const current = DateTime.fromFormat(entry.data, "yyyyLLdd", { zone: "UTC" });
        if (!current.isValid) continue;
        if (current < start || current > end) continue;

        const iso = current.toISODate();
        if (!from || iso < from) from = iso;
        if (!to || iso > to) to = iso;

        hits += entry.hits?.count || 0;
        visitors += entry.visitors?.count || 0;
    }

    const ratios = adjustCrawlers ? crawlerRatios(data) : { hits: 0, visitors: 0 };

    const adjust = (value, ratio) => {
        if (!adjustCrawlers) return value;
        const scaled = value * (1 - ratio);
        return Math.max(0, Math.round(scaled));
    };

    return {
        from,
        to,
        hits: adjust(hits, ratios.hits),
        visitors: adjust(visitors, ratios.visitors),
    };
}

module.exports = {
    fetchGoAccessJson,
    groupVisitsByMonth,
    aggregateLastNDays,
    crawlerRatios,
};