import { useCallback, useEffect, useState } from 'react'

// Playback speed for the battle replay. A multiplier: 2 means everything (JS
// step timers and CSS animation durations alike) runs twice as fast. The choice
// is remembered across sessions in localStorage so a player who likes it quick
// doesn't have to re-set it every battle.

const STORAGE_KEY = 'sap:battleSpeed'

// The values offered in the speed picker. 1 is the honest, savour-it pace;
// higher values are for players who've seen enough clashes for one evening.
export const SPEED_OPTIONS = [0.5, 1, 1.5, 2, 3] as const

const DEFAULT_SPEED = 1

function load(): number {
  if (typeof localStorage === 'undefined') return DEFAULT_SPEED
  const raw = localStorage.getItem(STORAGE_KEY)
  const n = raw ? Number(raw) : NaN
  // Guard against stale/garbage values, and snap to a known option.
  return SPEED_OPTIONS.includes(n as (typeof SPEED_OPTIONS)[number]) ? n : DEFAULT_SPEED
}

export function useBattleSpeed(): [number, (n: number) => void] {
  const [speed, setSpeed] = useState<number>(load)

  useEffect(() => {
    try {
      localStorage.setItem(STORAGE_KEY, String(speed))
    } catch {
      // Private-mode / storage-disabled: keep the in-memory value, just don't persist.
    }
  }, [speed])

  const set = useCallback((n: number) => setSpeed(n), [])
  return [speed, set]
}