import { useCallback, useEffect, useRef, useState } from 'react'
import { message } from './bridge.js'

// One hook for every screen that loads and refreshes.
//
// It exists because the naive version has two bugs every screen would repeat:
// a slow response arriving after the user navigated away sets state on an
// unmounted component, and a poll that fires while the previous request is
// still running stacks up requests against an engine that is already slow.
export function usePolled(fn, intervalMs, deps = []) {
  const [data, setData] = useState(null)
  const [error, setError] = useState(null)
  const [loading, setLoading] = useState(true)
  const alive = useRef(true)
  const busy = useRef(false)

  const run = useCallback(async () => {
    if (busy.current) return
    busy.current = true
    try {
      const result = await fn()
      if (!alive.current) return
      setData(result)
      setError(null)
    } catch (err) {
      if (alive.current) setError(message(err))
    } finally {
      busy.current = false
      if (alive.current) setLoading(false)
    }
    // eslint-disable-next-line react-hooks/exhaustive-deps
  }, deps)

  useEffect(() => {
    alive.current = true
    run()
    if (!intervalMs) return () => { alive.current = false }
    const id = setInterval(run, intervalMs)
    return () => { alive.current = false; clearInterval(id) }
  }, [run, intervalMs])

  return { data, error, loading, reload: run }
}

export function fmtTime(ts) {
  if (!ts) return '—'
  const d = typeof ts === 'number' ? new Date(ts * 1000) : new Date(ts)
  if (isNaN(d)) return '—'
  return d.toLocaleTimeString([], { hour: '2-digit', minute: '2-digit' })
}

export function fmtDate(ts) {
  if (!ts) return '—'
  const d = typeof ts === 'number' ? new Date(ts * 1000) : new Date(ts)
  if (isNaN(d)) return '—'
  return d.toLocaleDateString([], { day: 'numeric', month: 'short' })
}

export function daysAgo(n) {
  const d = new Date()
  d.setDate(d.getDate() - n)
  return d.toISOString().slice(0, 10)
}

export function today() { return new Date().toISOString().slice(0, 10) }