// I can't do the normal thing here:
//     import { PrismaClient } from "@prisma/client";
// because something something modules. So have to do this weird thing.
import pkg from '@prisma/client';
const {PrismaClient} = pkg;

export const prisma = new PrismaClient();

// We use database time whenever we work with dates (eg, active pings).
export async function dbDateToday() {
  const now: [{date: string}] =
    await prisma.$queryRaw`select now()::date as date`;
  return dbDateFromString(now[0].date);
}

// s is a string like "2020-01-01" assumed to be UTC.
export function dbDateFromString(s: string) {
  const [year, month, day] = s.split('-').map(n => parseInt(n));
  return new Date(Date.UTC(year, month - 1 /* ! WTF JS ! */, day));
}

export function firstDayOfMonth(d: Date) {
  return new Date(Date.UTC(d.getUTCFullYear(), d.getUTCMonth(), 1));
}

export function lastDayOfMonth(d: Date) {
  // First day of next month.
  const d2 = new Date(Date.UTC(d.getUTCFullYear(), d.getUTCMonth() + 1, 1));
  d2.setUTCDate(d2.getUTCDate() - 1);
  return d2;
}

export function monthsAgo(d: Date, n: number) {
  const year = d.getUTCFullYear();
  const month = d.getUTCMonth();
  let day = d.getUTCDate();
  // Careful! A previous month might have fewer days than d has. If so,
  // set the day to the last day of the target month.
  const days = daysInMonth(new Date(Date.UTC(year, month - n, 1)));
  if (day > days) {
    day = days;
  }
  return new Date(Date.UTC(year, month - n, day));
}

function daysInMonth(d: Date) {
  return new Date(
    Date.UTC(d.getUTCFullYear(), d.getUTCMonth() + 1, 0),
  ).getUTCDate();
}