vin-decoder/src/cache.js

import db from './db.js';
import { fetchFromNhtsa, mapNhtsaToSchema, TTL_SECONDS } from './nhtsa.js';

const VIN_RE = /^[A-HJ-NPR-Z0-9]{17}$/;

export function validateVin(vin) {
  return typeof vin === 'string' && VIN_RE.test(vin.toUpperCase());
}

const getStmt = db.prepare(
  'SELECT * FROM vin_cache WHERE vin = ? AND expires_at > unixepoch()'
);

const upsertStmt = db.prepare(`
  INSERT INTO vin_cache
    (vin, make, model, model_year, trim, series, body_class, drive_type,
     engine_displacement_cc, engine_displacement_l, engine_cylinders,
     fuel_type_primary, transmission_style, transmission_speeds,
     plant_city, plant_state, plant_country, manufacturer_name,
     vehicle_type, error_code, error_text, raw_nhtsa, cached_at, expires_at)
  VALUES
    (@vin, @make, @model, @model_year, @trim, @series, @body_class, @drive_type,
     @engine_displacement_cc, @engine_displacement_l, @engine_cylinders,
     @fuel_type_primary, @transmission_style, @transmission_speeds,
     @plant_city, @plant_state, @plant_country, @manufacturer_name,
     @vehicle_type, @error_code, @error_text, @raw_nhtsa, @cached_at, @expires_at)
  ON CONFLICT(vin) DO UPDATE SET
    make=excluded.make, model=excluded.model, model_year=excluded.model_year,
    trim=excluded.trim, series=excluded.series, body_class=excluded.body_class,
    drive_type=excluded.drive_type,
    engine_displacement_cc=excluded.engine_displacement_cc,
    engine_displacement_l=excluded.engine_displacement_l,
    engine_cylinders=excluded.engine_cylinders,
    fuel_type_primary=excluded.fuel_type_primary,
    transmission_style=excluded.transmission_style,
    transmission_speeds=excluded.transmission_speeds,
    plant_city=excluded.plant_city, plant_state=excluded.plant_state,
    plant_country=excluded.plant_country,
    manufacturer_name=excluded.manufacturer_name,
    vehicle_type=excluded.vehicle_type,
    error_code=excluded.error_code, error_text=excluded.error_text,
    raw_nhtsa=excluded.raw_nhtsa,
    cached_at=excluded.cached_at, expires_at=excluded.expires_at
`);

const evictStmt = db.prepare('DELETE FROM vin_cache WHERE expires_at < unixepoch()');

export function evictExpired() {
  return evictStmt.run().changes;
}

export async function decodeVin(vin) {
  const upperVin = vin.toUpperCase();
  const cached = getStmt.get(upperVin);
  if (cached) {
    return { result: { ...cached, cached: true }, fromCache: true };
  }
  const raw = await fetchFromNhtsa(upperVin);
  const mapped = mapNhtsaToSchema(raw);
  const now = Math.floor(Date.now() / 1000);
  upsertStmt.run({
    vin: upperVin, ...mapped,
    raw_nhtsa: JSON.stringify(raw),
    cached_at: now,
    expires_at: now + TTL_SECONDS,
  });
  return { result: { vin: upperVin, ...mapped, cached: false }, fromCache: false };
}

export function getCacheStats() {
  const count = db.prepare('SELECT COUNT(*) AS c FROM vin_cache WHERE expires_at > unixepoch()').get();
  const size = db.prepare("SELECT page_count * page_size AS sz FROM pragma_page_count(), pragma_page_size()").get();
  return {
    entries: count?.c ?? 0,
    size_mb: size ? Math.round(size.sz / 1024 / 1024 * 100) / 100 : 0,
  };
}