walkbyfaith/src/verse.ts

import { getBooks, loadBible, type Verse } from './bible'

const ROLLOVER_LOCAL_HOUR = 2

export interface DailyVerse extends Verse {
  book: string
  chapter: number
  verse: number
}

let flatNT: DailyVerse[] | null = null

export function daySeed(now: Date = new Date()): number {
  const shifted = new Date(now.getTime() - ROLLOVER_LOCAL_HOUR * 3600_000)
  return Math.floor(Date.UTC(shifted.getFullYear(), shifted.getMonth(), shifted.getDate()) / 86_400_000)
}

export function msUntilRollover(now: Date = new Date()): number {
  const next = new Date(now)
  next.setHours(ROLLOVER_LOCAL_HOUR, 0, 0, 0)
  if (next.getTime() <= now.getTime()) next.setDate(next.getDate() + 1)
  return next.getTime() - now.getTime()
}

function mulberry32(seed: number): () => number {
  let a = seed >>> 0
  return () => {
    a = (a + 0x6d2b79f5) | 0
    let t = Math.imul(a ^ (a >>> 15), 1 | a)
    t = (t + Math.imul(t ^ (t >>> 7), 61 | t)) ^ t
    return ((t ^ (t >>> 14)) >>> 0) / 4294967296
  }
}

export function pickForDay(verses: DailyVerse[], seed: number): DailyVerse {
  const rand = mulberry32(seed)
  const index = Math.floor(rand() * verses.length)
  return verses[index]
}

export async function loadKJV(): Promise<DailyVerse[]> {
  if (flatNT) return flatNT
  await loadBible()
  flatNT = []
  let inNewTestament = false
  for (const book of getBooks()) {
    if (book.book === 'Matthew') inNewTestament = true
    if (!inNewTestament) continue
    const name = book.book === 'Psalms' ? 'Psalm' : book.book
    for (const chapter of book.chapters) {
      const chapterNumber = Number(chapter.chapter)
      for (const v of chapter.verses) {
        flatNT.push({ text: v.text, reference: `${name} ${chapterNumber}:${v.verse}`, book: book.book, chapter: chapterNumber, verse: v.verse })
      }
    }
  }
  return flatNT
}