import { readFileSync, writeFileSync, existsSync } from 'fs';
import { dirname, join } from 'path';
import { fileURLToPath } from 'url';

const __dirname = dirname(fileURLToPath(import.meta.url));
const DB_FILE = process.env.ANALYTICS_PATH || join(__dirname, 'analytics.json');

function loadDB() {
  if (existsSync(DB_FILE)) {
    return JSON.parse(readFileSync(DB_FILE, 'utf-8'));
  }
  return { events: [], _counter: 0 };
}

function saveDB(data) {
  writeFileSync(DB_FILE, JSON.stringify(data, null, 2));
}

let db = loadDB();

function nextId() {
  db._counter = (db._counter || 0) + 1;
  return db._counter;
}

function now() {
  return new Date().toISOString().replace('T', ' ').slice(0, 19);
}

export function trackEvent(type, userId, metadata = {}) {
  const event = {
    id: nextId(),
    type,
    user_id: userId || null,
    timestamp: now(),
    ...metadata,
  };
  db.events.push(event);
  saveDB(db);
  return event;
}

export function getEvents({ from, to, type, user_id, limit = 100 } = {}) {
  let results = [...db.events];

  if (from) {
    results = results.filter(e => e.timestamp >= from);
  }
  if (to) {
    results = results.filter(e => e.timestamp <= to);
  }
  if (type) {
    results = results.filter(e => e.type === type);
  }
  if (user_id) {
    results = results.filter(e => e.user_id === Number(user_id));
  }

  results.sort((a, b) => b.timestamp.localeCompare(a.timestamp));
  return results.slice(0, limit);
}

export function getOverview() {
  const today = new Date().toISOString().slice(0, 10);
  const weekAgo = new Date(Date.now() - 7 * 24 * 60 * 60 * 1000).toISOString().slice(0, 10);
  const yesterday = new Date(Date.now() - 24 * 60 * 60 * 1000).toISOString().slice(0, 10);

  const pageviews = db.events.filter(e => e.type === 'page_view');
  const pageviewsToday = pageviews.filter(e => e.timestamp.startsWith(today)).length;
  const pageviewsYesterday = pageviews.filter(e => e.timestamp.startsWith(yesterday)).length;
  const pageviewsWeek = pageviews.filter(e => e.timestamp.slice(0, 10) >= weekAgo).length;
  const pageviewsTotal = pageviews.length;

  const activeUsers = new Set(db.events.filter(e => e.user_id).map(e => e.user_id));
  const activeUsersToday = new Set(
    db.events.filter(e => e.user_id && e.timestamp.startsWith(today)).map(e => e.user_id)
  ).size;

  const recipesCreated = db.events.filter(e => e.type === 'recipe_created').length;
  const recipesUpdated = db.events.filter(e => e.type === 'recipe_updated').length;
  const recipesDeleted = db.events.filter(e => e.type === 'recipe_deleted').length;
  const logins = db.events.filter(e => e.type === 'user_login').length;

  return {
    pageviews: { today: pageviewsToday, yesterday: pageviewsYesterday, week: pageviewsWeek, total: pageviewsTotal },
    activeUsers: { total: activeUsers.size, today: activeUsersToday },
    recipes: { created: recipesCreated, updated: recipesUpdated, deleted: recipesDeleted },
    logins,
  };
}

export function getPageviewsByDay(from, to) {
  const pageviews = db.events.filter(e => e.type === 'page_view');
  const days = {};

  for (const e of pageviews) {
    const day = e.timestamp.slice(0, 10);
    if (from && day < from) continue;
    if (to && day > to) continue;
    days[day] = (days[day] || 0) + 1;
  }

  return Object.entries(days)
    .map(([date, count]) => ({ date, count }))
    .sort((a, b) => a.date.localeCompare(b.date));
}

export function getTopUsers(limit = 10) {
  const userActivity = {};

  for (const e of db.events) {
    if (!e.user_id) continue;
    if (!userActivity[e.user_id]) {
      userActivity[e.user_id] = { user_id: e.user_id, logins: 0, recipes_created: 0, recipes_updated: 0, total_events: 0 };
    }
    userActivity[e.user_id].total_events++;
    if (e.type === 'user_login') userActivity[e.user_id].logins++;
    if (e.type === 'recipe_created') userActivity[e.user_id].recipes_created++;
    if (e.type === 'recipe_updated') userActivity[e.user_id].recipes_updated++;
  }

  return Object.values(userActivity)
    .sort((a, b) => b.total_events - a.total_events)
    .slice(0, limit);
}

export function getTopRecipes(limit = 10) {
  const recipeViews = {};

  for (const e of db.events) {
    if (e.type === 'page_view' && e.path?.startsWith('/recipe/')) {
      const id = e.path.split('/')[2];
      if (id) {
        recipeViews[id] = (recipeViews[id] || 0) + 1;
      }
    }
  }

  return Object.entries(recipeViews)
    .map(([recipe_id, views]) => ({ recipe_id: Number(recipe_id), views }))
    .sort((a, b) => b.views - a.views)
    .slice(0, limit);
}

export function getRecentActivity(limit = 50) {
  return db.events
    .sort((a, b) => b.timestamp.localeCompare(a.timestamp))
    .slice(0, limit);
}