/**
 * Varify Shopify Web Pixel — links experiments/variations a customer saw to
 * whether they completed a purchase.
 */

let storage;

// Store's currency, used to normalize order totals before sending them.
const SHOP_CURRENCY = init.data?.shop?.paymentSettings?.currencyCode || 'EUR';

// Free FX API, used only when an order's currency differs from the store's.
const FX_API = 'https://api.frankfurter.dev/v1/latest';
const FX_TTL_MS = 6 * 60 * 60 * 1000;
const FX_TIMEOUT_MS = 2000;

const VARIFY_INGESTION_ENDPOINT = 'https://w.varify.io/events';

// One id per pixel session, reused for every event this pixel sends.
const pixelSessionId = crypto.randomUUID();

// Reads this pixel's saved data (experiments seen, anonymous id, etc.),
// cached in-memory after the first read.
async function getVarifyData() {
  if (storage) {
    return storage;
  }
  storage = (async () => {
    try {
      const raw = await browser.localStorage.getItem('varify-data');
      return raw ? JSON.parse(raw) : {};
    } catch (error) {
      // Don't cache a broken read — retry from scratch next time.
      storage = undefined;
      console.error('Varify: error reading local storage', error);
      return {};
    }
  })();
  return storage;
}

// Units of `currency` per 1 unit of the store's currency, or null if
// unavailable — callers should skip sending rather than guess a rate.
async function getFxRate(currency) {
  const cacheKey = `varify-fx-${SHOP_CURRENCY}-${currency}`;

  try {
    const cached = await browser.localStorage.getItem(cacheKey);
    if (cached) {
      const { rate, ts } = JSON.parse(cached);
      if (rate && ts && Date.now() - ts < FX_TTL_MS) {
        return rate;
      }
    }
  } catch (error) {
    // Fall through and fetch fresh below.
  }

  try {
    const url = `${FX_API}?from=${encodeURIComponent(SHOP_CURRENCY)}&to=${encodeURIComponent(currency)}`;

    let res;
    if (typeof AbortController === 'function') {
      const controller = new AbortController();
      const timer = setTimeout(() => controller.abort(), FX_TIMEOUT_MS);
      try {
        res = await fetch(url, { signal: controller.signal });
      } finally {
        clearTimeout(timer);
      }
    } else {
      res = await fetch(url);
    }

    if (!res.ok) {
      console.warn(`Varify: FX API returned ${res.status} for ${currency}.`);
      return null;
    }

    const json = await res.json();
    const rate = json?.rates?.[currency];

    if (typeof rate !== 'number' || !isFinite(rate) || rate <= 0) {
      console.warn(`Varify: FX API gave no usable rate for ${currency}.`, json);
      return null;
    }

    await browser.localStorage.setItem(
      cacheKey,
      JSON.stringify({ rate, ts: Date.now() }),
    );
    return rate;
  } catch (error) {
    console.warn(`Varify: FX lookup failed for ${currency}.`, error);
    return null;
  }
}

// Varify's endpoint only accepts flat text/number values, so a list of
// experiments becomes two comma-separated strings (ids and variation ids).
function flattenExperiments(entries) {
  return {
    experiment_ids: entries.map((entry) => entry.experimentId).join(','),
    variation_ids: entries
      .map((entry) =>
        entry.variationId === null ? 'original' : entry.variationId,
      )
      .join(','),
  };
}

// Edge's identifier also contains "Chrome/", so it must be checked first.
function detectBrowser(userAgent) {
  if (userAgent.includes('Firefox/')) return 'Firefox';
  if (userAgent.includes('Edg/')) return 'Edge';
  if (userAgent.includes('Chrome/')) return 'Chrome';
  if (userAgent.includes('Safari/')) return 'Safari';
  return 'Unknown';
}

function detectDevice(userAgent) {
  if (/Tablet|iPad/i.test(userAgent)) return 'tablet';
  if (/Mobi|Android/i.test(userAgent)) return 'mobile';
  return 'desktop';
}

function detectOs(userAgent) {
  if (/iPhone|iPad|iPod/i.test(userAgent)) return 'iOS';
  if (userAgent.includes('Android')) return 'Android';
  if (userAgent.includes('Win')) return 'Windows';
  if (userAgent.includes('Mac')) return 'macOS';
  if (userAgent.includes('Linux')) return 'Linux';
  return 'Unknown';
}

// Browser timezone, e.g. "Europe/Berlin" — not GPS or IP-based location.
function detectLocation() {
  try {
    return Intl.DateTimeFormat().resolvedOptions().timeZone || undefined;
  } catch {
    return undefined;
  }
}

// Non-identifying browser/page details, added to every event. The pixel
// sandbox may not expose all of these — each lookup is best-effort and
// simply omitted if unavailable.
function collectBrowserInfo() {
  const info = {};

  try {
    const userAgent =
      typeof navigator !== 'undefined' ? navigator.userAgent : undefined;
    if (typeof userAgent === 'string') {
      info.userAgent = userAgent;
      info.browser = detectBrowser(userAgent);
      info.device = detectDevice(userAgent);
      info.os = detectOs(userAgent);
    }
  } catch (error) {
    // Not available in this environment.
  }

  try {
    if (typeof window !== 'undefined' && window.location) {
      info.path = window.location.pathname;
      info.domain = window.location.hostname;
    }
  } catch (error) {
    // Not available in this environment.
  }

  const location = detectLocation();
  if (location) {
    info.location = location;
  }

  return info;
}

// Sends one event to Varify. Never throws — failures are logged and
// swallowed so the pixel/checkout is never affected. Falls back to reading
// the anonymous id from local storage if one wasn't passed in, and returns
// whichever id was actually used so the caller can persist it.
async function sendVarifyEvent(name, teamSqid, anonymousId, properties) {
  const anonymousIdWithFallback =
    anonymousId || localStorage.getItem('varify_anonymous_id');

  if (!teamSqid || !anonymousIdWithFallback) {
    console.warn(
      `Varify: skipping "${name}" event — missing teamSqid or anonymousId.`,
      'Team Sqid',
      teamSqid,
      'Anonymous ID',
      anonymousIdWithFallback,
    );
    return anonymousIdWithFallback;
  }

  try {
    await fetch(VARIFY_INGESTION_ENDPOINT, {
      method: 'POST',
      keepalive: true,
      headers: {
        'Content-Type': 'application/json',
      },
      body: JSON.stringify({
        events: [
          {
            id: crypto.randomUUID(),
            name,
            teamId: String(teamSqid),
            anonymousId: anonymousIdWithFallback,
            sessionId: pixelSessionId,
            properties: { ...collectBrowserInfo(), ...properties },
          },
        ],
      }),
    });
  } catch (error) {
    console.error(`Varify: error sending "${name}" event`, error);
  }

  return anonymousIdWithFallback;
}

// Fired by Varify's tracking script when a customer is shown an experiment.
// Remembers it locally so it can be attached to a later checkout event.
analytics.subscribe('varify', async (event) => {
  const {
    varify_experimentId,
    varify_variationId,
    varify_anonymousId,
    teamId,
    teamSqid,
    storageType = 'localStorage',
  } = event.customData || {};

  if (!varify_experimentId || !teamId || !teamSqid) {
    console.warn('Varify: event missing experimentId or teamId. Event:', event);
    return;
  }

  const validVariationId =
    varify_variationId !== undefined ? varify_variationId : null;

  const existingData = await getVarifyData();

  if (!existingData.data) {
    existingData.data = [];
  }

  const experimentEntry = {
    experimentId: varify_experimentId,
    variationId: validVariationId,
    timestamp: Date.now(),
  };

  existingData.data = existingData.data.filter(
    (entry) => entry.experimentId !== varify_experimentId,
  );

  existingData.data.push(experimentEntry);
  existingData.teamId = teamId;
  existingData.teamSqid = teamSqid;
  existingData.storageType = storageType;

  // Only present once Varify's tracking script has finished loading —
  // don't overwrite a previously-saved id with nothing.
  if (varify_anonymousId) {
    existingData.anonymousId = varify_anonymousId;
  }

  await browser.localStorage.setItem(
    'varify-data',
    JSON.stringify(existingData),
  );
});

// How long an experiment exposure counts toward a later purchase.
const WINDOW_MS = 28 * 24 * 60 * 60 * 1000;

const pruneEntries = (entries) => {
  const threshold = Date.now() - WINDOW_MS;
  return (entries || []).filter(
    (entry) =>
      entry.timestamp && entry.experimentId && entry.timestamp >= threshold,
  );
};

analytics.subscribe('checkout_started', async (event) => {
  const existingData = await getVarifyData();
  if (!existingData.data || existingData.data.length === 0) {
    return;
  }

  existingData.data = pruneEntries(existingData.data);

  await browser.localStorage.setItem(
    'varify-data',
    JSON.stringify(existingData),
  );

  if (existingData.data.length > 0) {
    const resolvedAnonymousId = await sendVarifyEvent(
      'checkout_started',
      existingData.teamSqid,
      existingData.anonymousId,
      flattenExperiments(existingData.data),
    );

    // Persist the fallback id, if used, so it doesn't need re-deriving.
    if (
      resolvedAnonymousId &&
      resolvedAnonymousId !== existingData.anonymousId
    ) {
      existingData.anonymousId = resolvedAnonymousId;
      await browser.localStorage.setItem(
        'varify-data',
        JSON.stringify(existingData),
      );
    }
  }

  // Warm the rate while the customer is still typing.
  const currency = event.data?.checkout?.currencyCode;
  if (currency && currency !== SHOP_CURRENCY) {
    getFxRate(currency);
  }
});

analytics.subscribe('checkout_completed', async (event) => {
  const orderId = event.data?.checkout?.order?.id;
  const money = event.data?.checkout?.subtotalPrice;
  let orderRevenue = money?.amount;
  const orderCurrency = money?.currencyCode;

  // 0 is a valid revenue (100% discount) and must not count as missing.
  if (!orderId || orderRevenue == null || !orderCurrency) {
    console.warn(
      'Varify: checkout_completed missing orderId, revenue or currency.',
    );
    return;
  }

  // subtotalPrice is presentment currency and the event carries no rate or
  // shop-money amount. Convert to shop currency here, or skip.
  if (orderCurrency !== SHOP_CURRENCY) {
    const rate = await getFxRate(orderCurrency);
    if (!rate) {
      console.warn(
        `Varify: skipping order ${orderId} — ${orderRevenue} ${orderCurrency}, no FX rate available.`,
      );
      return;
    }
    const converted = +(orderRevenue / rate).toFixed(2);
    console.info(
      `Varify: converted order ${orderId} — ${orderRevenue} ${orderCurrency} @ ${rate} -> ${converted} ${SHOP_CURRENCY}.`,
    );
    orderRevenue = converted;
  }

  const parsedData = await getVarifyData();
  if (!parsedData.data || parsedData.data.length === 0 || !parsedData.teamId) {
    console.warn('Varify: no valid data in local storage.');
    return;
  }

  // The order-status page refires checkout_completed on every visit.
  if (!Array.isArray(parsedData.sentOrders)) {
    parsedData.sentOrders = [];
  }
  if (parsedData.sentOrders.includes(orderId)) {
    return;
  }

  parsedData.data = pruneEntries(parsedData.data);
  if (parsedData.data.length === 0) {
    return;
  }

  const lineItems = event.data?.checkout?.lineItems;
  let cartProducts = [];

  if (lineItems && Array.isArray(lineItems)) {
    cartProducts = lineItems
      .map((item) => {
        const productId = item.variant?.product?.id?.split('/').pop();
        const variantId = item.variant?.id?.split('/').pop();

        if (productId && variantId) {
          return {
            productId,
            variantId,
          };
        }
        return null;
      })
      .filter((p) => p !== null);
  }

  const resolvedAnonymousId = await sendVarifyEvent(
    'checkout_completed',
    parsedData.teamSqid,
    parsedData.anonymousId,
    {
      ...flattenExperiments(parsedData.data),
      order_id: String(orderId),
      value: orderRevenue,
      currency: SHOP_CURRENCY,
      cart_product_ids: cartProducts.map((p) => p.productId).join(','),
      cart_variant_ids: cartProducts.map((p) => p.variantId).join(','),
    },
  );

  // Persist the fallback id, if used, so it doesn't need re-deriving.
  if (resolvedAnonymousId) {
    parsedData.anonymousId = resolvedAnonymousId;
  }

  parsedData.sentOrders = [...parsedData.sentOrders, orderId].slice(-50);
  await browser.localStorage.setItem('varify-data', JSON.stringify(parsedData));
});