import fs from 'node:fs';
import path from 'node:path';
import crypto from 'node:crypto';
import config from './config.js';
import db from './db.js';

const MAX_BYTES = 4 * 1024 * 1024;

/**
 * Accepts a data URL from the kiosk camera and writes it to disk.
 * Returns a path relative to config.photoDir, or null if there was no photo.
 */
export function savePhoto(dataUrl) {
  if (!dataUrl) return null;
  const match = /^data:image\/(jpeg|jpg|png|webp);base64,([A-Za-z0-9+/=]+)$/.exec(
    String(dataUrl).trim()
  );
  if (!match) throw new Error('Photo could not be read. Retake it and try again.');

  const ext = match[1] === 'jpg' ? 'jpeg' : match[1];
  const buffer = Buffer.from(match[2], 'base64');
  if (buffer.length > MAX_BYTES) throw new Error('Photo is too large.');

  const now = new Date();
  const folder = path.join(String(now.getFullYear()), String(now.getMonth() + 1).padStart(2, '0'));
  const dir = path.join(config.photoDir, folder);
  fs.mkdirSync(dir, { recursive: true });

  const name = `${now.toISOString().replace(/[:.]/g, '-')}-${crypto.randomBytes(4).toString('hex')}.${ext}`;
  fs.writeFileSync(path.join(dir, name), buffer);
  return path.join(folder, name);
}

/**
 * Copies a recurring visitor's stored photo into a new file for one visit.
 *
 * A copy rather than a shared reference on purpose: the visit record is a snapshot
 * of who was in the building that day, so replacing someone's profile photo later
 * must not retroactively change what every past visit shows. It also keeps photo
 * retention simple — purging old visits can never delete a live profile photo.
 */
export function copyStoredPhoto(relative) {
  const source = photoAbsolutePath(relative);
  if (!source) return null;

  const now = new Date();
  const folder = path.join(String(now.getFullYear()), String(now.getMonth() + 1).padStart(2, '0'));
  const dir = path.join(config.photoDir, folder);
  fs.mkdirSync(dir, { recursive: true });

  const ext = path.extname(source) || '.jpeg';
  const name = `${now.toISOString().replace(/[:.]/g, '-')}-${crypto.randomBytes(4).toString('hex')}${ext}`;
  fs.copyFileSync(source, path.join(dir, name));
  return path.join(folder, name);
}

export function photoAbsolutePath(relative) {
  if (!relative) return null;
  const resolved = path.resolve(config.photoDir, relative);
  if (!resolved.startsWith(path.resolve(config.photoDir))) return null;
  return fs.existsSync(resolved) ? resolved : null;
}

export function deletePhoto(relative) {
  const abs = photoAbsolutePath(relative);
  if (abs) {
    try {
      fs.unlinkSync(abs);
    } catch {
      /* already gone */
    }
  }
}

/** Deletes photo files older than the retention window and clears their DB reference. */
export function purgeOldPhotos() {
  if (!config.photoRetentionDays || config.photoRetentionDays <= 0) return 0;
  const cutoff = new Date(Date.now() - config.photoRetentionDays * 86400000).toISOString();
  const rows = db
    .prepare('SELECT id, photo_path FROM visits WHERE photo_path IS NOT NULL AND signed_in_at < ?')
    .all(cutoff);
  const clear = db.prepare('UPDATE visits SET photo_path = NULL WHERE id = ?');
  for (const row of rows) {
    deletePhoto(row.photo_path);
    clear.run(row.id);
  }
  if (rows.length) console.log(`[photos] purged ${rows.length} photo(s) past retention`);
  return rows.length;
}