// Paris timezone helpers + simulated/live clock state.
//
// State is module-level (singleton) so all components share the same
// `simDate` / `isLive` without prop drilling.

import { ref, computed } from 'vue'

export const TZ = 'Europe/Paris'

export function parisComponents(d) {
  const parts = new Intl.DateTimeFormat('fr-FR', {
    timeZone: TZ,
    year: 'numeric',
    month: '2-digit',
    day: '2-digit',
    hour: '2-digit',
    minute: '2-digit',
    second: '2-digit',
    hour12: false,
  }).formatToParts(d)
  const get = (t) => parseInt(parts.find((x) => x.type === t).value, 10)
  return {
    year: get('year'),
    month: get('month'),
    day: get('day'),
    hour: get('hour'),
    minute: get('minute'),
    second: get('second'),
  }
}

export function parisDateStr(d) {
  const p = parisComponents(d)
  const pad = (n) => String(n).padStart(2, '0')
  return `${p.year}-${pad(p.month)}-${pad(p.day)}`
}

export function toInputStr(d) {
  const p = parisComponents(d)
  const pad = (n) => String(n).padStart(2, '0')
  return `${p.year}-${pad(p.month)}-${pad(p.day)}T${pad(p.hour)}:${pad(p.minute)}:${pad(p.second)}`
}

export function getParisOffsetMs(d) {
  const fmt = (tz) =>
    new Intl.DateTimeFormat('en-GB', {
      timeZone: tz,
      hour: '2-digit',
      minute: '2-digit',
      hour12: false,
    }).format(d)
  const [uh, um] = fmt('UTC').split(':').map(Number)
  const [ph, pm] = fmt(TZ).split(':').map(Number)
  return ((ph * 60 + pm) - (uh * 60 + um)) * 60000
}

export function parisStrToDate(val) {
  const naive = new Date(val + 'Z')
  return new Date(naive.getTime() - getParisOffsetMs(naive))
}

// --- Shared singleton state ---
const simDate = ref(null)
const isLive = ref(true)

function getNow() {
  return isLive.value ? new Date() : simDate.value
}

function setSimulated(date) {
  simDate.value = date
  isLive.value = false
}

function goLive() {
  simDate.value = null
  isLive.value = true
}

export function useClockState() {
  return {
    simDate: computed(() => simDate.value),
    isLive: computed(() => isLive.value),
    getNow,
    setSimulated,
    goLive,
  }
}