auto-charger/web/lib/db.ts

import Database from "better-sqlite3";

const DB_PATH = process.env.DB_PATH || "/data/charges.db";

export interface Charge {
  id: number;
  start_time: string;
  end_time: string;
  duration_s: number;
  energy_wh: number;
}

export interface Totals {
  month_wh: number;
  year_wh: number;
  total_wh: number;
  install_date: string | null;
}

/**
 * Öffnet die DB read-only und gibt sie an `fn`. Es wird bewusst pro Aufruf eine
 * frische Verbindung geöffnet (und wieder geschlossen): Der Collector schreibt
 * aus einem anderen Prozess/Container im WAL-Modus, und eine langlebige
 * readonly-Verbindung bekommt diese Writes über den Docker-Desktop-FUSE-Mount
 * nicht zuverlässig mit (inkohärenter WAL-Index im Shared-Memory). Eine frische
 * Verbindung liest immer den aktuellen Stand.
 *
 * Gibt `fallback` zurück, wenn die Datei/das Schema noch nicht existiert
 * (Collector legt sie beim ersten Start an) — die Seite bleibt dann leer statt
 * zu crashen.
 */
function withDb<T>(fallback: T, fn: (conn: Database.Database) => T): T {
  let conn: Database.Database | null = null;
  try {
    conn = new Database(DB_PATH, { readonly: true, fileMustExist: true });
    const hasTable = conn
      .prepare("SELECT name FROM sqlite_master WHERE type='table' AND name='charges'")
      .get();
    if (!hasTable) return fallback;
    return fn(conn);
  } catch {
    return fallback;
  } finally {
    conn?.close();
  }
}

export function getCharges(): Charge[] {
  return withDb<Charge[]>([], (conn) =>
    conn
      .prepare(
        `SELECT id, start_time, end_time, duration_s, energy_wh
         FROM charges ORDER BY start_time DESC`,
      )
      .all() as Charge[],
  );
}

export function getTotals(): Totals {
  const empty: Totals = { month_wh: 0, year_wh: 0, total_wh: 0, install_date: null };
  return withDb<Totals>(empty, (conn) => {
  const month = conn
    .prepare(
      `SELECT COALESCE(SUM(energy_wh), 0) AS s FROM charges
       WHERE strftime('%Y-%m', start_time) = strftime('%Y-%m', 'now', 'localtime')`,
    )
    .get() as { s: number };
  const year = conn
    .prepare(
      `SELECT COALESCE(SUM(energy_wh), 0) AS s FROM charges
       WHERE strftime('%Y', start_time) = strftime('%Y', 'now', 'localtime')`,
    )
    .get() as { s: number };
  const total = conn
    .prepare(`SELECT COALESCE(SUM(energy_wh), 0) AS s FROM charges`)
    .get() as { s: number };
  const install = conn
    .prepare(`SELECT value FROM meta WHERE key = 'install_date'`)
    .get() as { value: string } | undefined;

  return {
    month_wh: month.s,
    year_wh: year.s,
    total_wh: total.s,
    install_date: install?.value ?? null,
  };
  });
}