import { getApiUrl } from "./apiConfig"; // Assuming this correctly returns the server's base URL

// --- Constants ---
const VISITOR_ID_KEY = "gda.visitorId";
const SESSION_MARK_KEY = "gda.visitRecorded";
const LOCATION_CACHE_KEY = "gda.coarseLocation";

// --- Core Helper Functions (These are well-written and retained) ---

function generateVisitorId() {
  if (typeof crypto !== "undefined" && crypto.randomUUID) {
    return crypto.randomUUID();
  }
  const random = Math.random().toString(36).slice(2);
  const time = Date.now().toString(36);
  return `v_${time}_${random}`;
}

function getOrCreateVisitorId() {
  if (typeof window === "undefined") return null;
  try {
    const existing = localStorage.getItem(VISITOR_ID_KEY);
    if (existing) return existing;

    const id = generateVisitorId();
    localStorage.setItem(VISITOR_ID_KEY, id);
    return id;
  } catch {
    return generateVisitorId(); // Fallback for environments where localStorage might fail
  }
}

/**
 * A generic function to send any tracking event to the server.
 * This aligns with the server's `/api/track` endpoint and Pydantic model.
 * @param {string} eventType - The type of event (e.g., 'page_view', 'file_upload_start').
 * @param {object} eventData - A dictionary of additional data related to the event.
 */
export async function trackEvent(eventType, eventData = {}) {
  if (typeof window === "undefined") return;

  const clientId = getOrCreateVisitorId();
  if (!clientId) return;

  const payload = {
    client_id: clientId,
    event_type: eventType,
    event_data: eventData,
  };

  // This is a "fire-and-forget" request. We don't wait for the response,
  // and we use `keepalive` to ensure the request is sent even if the user
  // is navigating away from the page.
  try {
    fetch(getApiUrl("/api/track"), {
      method: "POST",
      headers: {
        "Content-Type": "application/json",
      },
      body: JSON.stringify(payload),
      keepalive: true,
    });
  } catch (error) {
    console.warn("Could not send tracking event to server:", error);
  }
}

/**
 * Records a single page visit per session to the server.
 * This now uses the generic `trackEvent` function.
 */
export async function recordVisit() {
  if (typeof window === "undefined") return;

  // Use sessionStorage to ensure this only runs once per browser session.
  try {
    if (sessionStorage.getItem(SESSION_MARK_KEY)) {
      return;
    }
    sessionStorage.setItem(SESSION_MARK_KEY, "1");
  } catch {
    // If sessionStorage fails, proceed anyway but might record multiple visits.
  }

  // Get location data to include in the event
  const location = await getCoarseLocation();

  trackEvent('page_view', {
    path: `${window.location.pathname}${window.location.search}${window.location.hash}`,
    referrer: document.referrer,
    location: location,
  });
}

/**
 * Fetches the user's coarse location using the Geolocation API.
 * This is well-written and retained.
 * @returns {Promise<object|null>}
 */
export function getCoarseLocation() {
  if (typeof window === "undefined") return Promise.resolve(null);

  try {
    const cached = sessionStorage.getItem(LOCATION_CACHE_KEY);
    if (cached) return Promise.resolve(JSON.parse(cached));
  } catch { /* Ignore cache errors */ }

  if (!("geolocation" in navigator)) return Promise.resolve(null);

  return new Promise((resolve) => {
    navigator.geolocation.getCurrentPosition(
      (position) => {
        const location = {
          lat: position.coords.latitude,
          lon: position.coords.longitude,
          accuracyMeters: position.coords.accuracy,
        };
        try {
          sessionStorage.setItem(LOCATION_CACHE_KEY, JSON.stringify(location));
        } catch { /* Ignore cache errors */ }
        resolve(location);
      },
      () => resolve(null),
      {
        enableHighAccuracy: false,
        maximumAge: 10 * 60 * 1000, // 10 minutes
        timeout: 8000,
      }
    );
  });
}