CShare/backend/src/services/analytics.ts

import { newUuid, sha256 } from '../utils/crypto.js';
import { store } from './store.js';
import type { DatabaseShape } from '../types.js';

/**
 * Record a view or download event directly on the provided database instance.
 * Useful for batched/atomic operations within store.update().
 */
export function recordEventInDb(
  db: DatabaseShape,
  linkId: string,
  type: 'view' | 'download',
  rawIp?: string,
  userAgent?: string,
  referrer?: string,
): void {
  const hashedIp = rawIp ? sha256(rawIp) : undefined;
  const cleanedUserAgent = userAgent || undefined;
  const cleanedReferrer = referrer || undefined;

  const file = db.files.find((f) => f.linkId === linkId && f.status === 'uploaded');
  if (file) {
    if (type === 'view') {
      file.views += 1;
    } else if (type === 'download') {
      file.downloads += 1;
    }
  }

  db.events.push({
    id: newUuid(),
    linkId,
    type,
    createdAt: new Date().toISOString(),
    ip: hashedIp,
    userAgent: cleanedUserAgent,
    referrer: cleanedReferrer,
  });
}

/**
 * Standalone helper to record an event.
 */
export async function recordEvent(
  linkId: string,
  type: 'view' | 'download',
  rawIp?: string,
  userAgent?: string,
  referrer?: string,
): Promise<void> {
  await store.update((db) => {
    recordEventInDb(db, linkId, type, rawIp, userAgent, referrer);
  });
}

/**
 * Generates a 30-day daily breakdown of views and downloads for a specific file link.
 */
export async function getDailyBreakdown(linkId: string, days = 30) {
  const db = await store.read();
  const now = new Date();
  const dateMap = new Map<string, { views: number; downloads: number }>();

  // Pre-fill the range of days
  for (let i = days - 1; i >= 0; i--) {
    const d = new Date(now.getTime() - i * 24 * 60 * 60 * 1000);
    const dateString = d.toISOString().split('T')[0];
    dateMap.set(dateString, { views: 0, downloads: 0 });
  }

  // Filter events matching the link ID
  const fileEvents = db.events.filter((e) => e.linkId === linkId);
  for (const event of fileEvents) {
    const dateString = event.createdAt.split('T')[0];
    if (dateMap.has(dateString)) {
      const counts = dateMap.get(dateString)!;
      if (event.type === 'view') counts.views += 1;
      if (event.type === 'download') counts.downloads += 1;
    }
  }

  return Array.from(dateMap.entries()).map(([date, counts]) => ({
    date,
    views: counts.views,
    downloads: counts.downloads,
  }));
}

/**
 * Aggregates and returns top referrers for a specific file link.
 */
export async function getTopReferrers(linkId: string) {
  const db = await store.read();
  const referrerCounts = new Map<string, number>();

  const fileEvents = db.events.filter((e) => e.linkId === linkId);
  for (const event of fileEvents) {
    const ref = event.referrer || 'Direct';
    referrerCounts.set(ref, (referrerCounts.get(ref) || 0) + 1);
  }

  return Array.from(referrerCounts.entries())
    .map(([referrer, count]) => ({ referrer, count }))
    .sort((a, b) => b.count - a.count);
}

/**
 * Generates the recent activity feed (views, downloads, and uploads) for a user session.
 */
export async function getActivityFeed(sessionId: string, limit = 20) {
  const db = await store.read();
  const myFiles = db.files.filter((f) => f.status === 'uploaded' && f.sessionId === sessionId);
  const myFileMap = new Map(myFiles.map((f) => [f.linkId, f]));

  const activities: Array<{
    id: string;
    type: 'view' | 'download' | 'upload';
    fileName: string;
    fileId: string;
    linkId: string;
    createdAt: string;
    ip?: string;
    userAgent?: string;
    referrer?: string;
  }> = [];

  // Add uploads
  for (const file of myFiles) {
    activities.push({
      id: file.id,
      type: 'upload',
      fileName: file.originalName,
      fileId: file.id,
      linkId: file.linkId,
      createdAt: file.createdAt,
    });
  }

  // Add views/downloads
  for (const event of db.events) {
    const file = myFileMap.get(event.linkId);
    if (file) {
      activities.push({
        id: event.id,
        type: event.type,
        fileName: file.originalName,
        fileId: file.id,
        linkId: event.linkId,
        createdAt: event.createdAt,
        ip: event.ip,
        userAgent: event.userAgent,
        referrer: event.referrer,
      });
    }
  }

  // Sort by date descending
  return activities
    .sort((a, b) => new Date(b.createdAt).getTime() - new Date(a.createdAt).getTime())
    .slice(0, limit);
}

function getFileCategory(mimeType: string, filename: string): string {
  const mime = mimeType.toLowerCase();
  const ext = filename.split('.').pop()?.toLowerCase() || '';

  if (mime.startsWith('image/')) return 'image';
  if (mime.startsWith('video/')) return 'video';
  if (mime.startsWith('audio/')) return 'audio';

  const archives = new Set(['zip', 'tar', 'gz', 'bz2', '7z', 'rar', 'tgz']);
  const archiveMimes = new Set([
    'application/zip',
    'application/x-tar',
    'application/x-gzip',
    'application/x-bzip2',
    'application/x-7z-compressed',
    'application/x-rar-compressed',
  ]);
  if (archives.has(ext) || archiveMimes.has(mime)) return 'archive';

  const documents = new Set(['pdf', 'doc', 'docx', 'xls', 'xlsx', 'ppt', 'pptx', 'txt', 'csv', 'rtf', 'html', 'css', 'json']);
  const documentMimes = new Set([
    'application/pdf',
    'application/msword',
    'application/vnd.openxmlformats-officedocument.wordprocessingml.document',
    'application/vnd.ms-excel',
    'application/vnd.openxmlformats-officedocument.spreadsheetml.sheet',
    'application/vnd.ms-powerpoint',
    'application/vnd.openxmlformats-officedocument.presentationml.presentation',
    'text/plain',
    'text/html',
    'text/css',
    'text/csv',
    'application/rtf',
    'application/json',
  ]);
  if (documents.has(ext) || documentMimes.has(mime)) return 'document';

  return 'other';
}

/**
 * Returns a storage size and count breakdown grouped by file type category.
 */
export async function getStorageBreakdown(sessionId: string) {
  const db = await store.read();
  const myFiles = db.files.filter((f) => f.status === 'uploaded' && f.sessionId === sessionId);

  const breakdown: Record<string, { count: number; sizeBytes: number }> = {
    document: { count: 0, sizeBytes: 0 },
    image: { count: 0, sizeBytes: 0 },
    video: { count: 0, sizeBytes: 0 },
    audio: { count: 0, sizeBytes: 0 },
    archive: { count: 0, sizeBytes: 0 },
    other: { count: 0, sizeBytes: 0 },
  };

  for (const file of myFiles) {
    const category = getFileCategory(file.mimeType, file.originalName);
    breakdown[category].count += 1;
    breakdown[category].sizeBytes += file.sizeBytes;
  }

  return Object.entries(breakdown).map(([category, stats]) => ({
    category,
    count: stats.count,
    sizeBytes: stats.sizeBytes,
  }));
}

/**
 * Aggregates monthly upload volume (number of uploads and sizes) for the last 6 months.
 */
export async function getMonthlyUploadVolume(sessionId: string, monthsCount = 6) {
  const db = await store.read();
  const myFiles = db.files.filter((f) => f.status === 'uploaded' && f.sessionId === sessionId);

  const volumeMap = new Map<string, { count: number; sizeBytes: number }>();
  const now = new Date();

  // Pre-fill last N months
  for (let i = monthsCount - 1; i >= 0; i--) {
    const d = new Date(now.getFullYear(), now.getMonth() - i, 1);
    const monthStr = `${d.getFullYear()}-${String(d.getMonth() + 1).padStart(2, '0')}`;
    volumeMap.set(monthStr, { count: 0, sizeBytes: 0 });
  }

  for (const file of myFiles) {
    const date = new Date(file.createdAt);
    const monthStr = `${date.getFullYear()}-${String(date.getMonth() + 1).padStart(2, '0')}`;
    if (volumeMap.has(monthStr)) {
      const stats = volumeMap.get(monthStr)!;
      stats.count += 1;
      stats.sizeBytes += file.sizeBytes;
    }
  }

  return Array.from(volumeMap.entries()).map(([month, stats]) => ({
    month,
    count: stats.count,
    sizeBytes: stats.sizeBytes,
  }));
}