import { createContext, useContext, useState, type ReactNode } from 'react';
import { MotionConfig } from 'framer-motion';

/**
 * "Reduce motion" device preference, persisted to localStorage under
 * 'bt-reduce-motion'. When ON, framer-motion animations are forced off
 * (`reducedMotion="always"`); when OFF we pass "user" so the OS
 * `prefers-reduced-motion` setting is still honored.
 */

const STORAGE_KEY = 'bt-reduce-motion';

function loadPref(): boolean {
  try {
    return localStorage.getItem(STORAGE_KEY) === 'true';
  } catch {
    return false;
  }
}

interface MotionPreferenceValue {
  reduceMotion: boolean;
  setReduceMotion: (v: boolean) => void;
}

const MotionPreferenceContext = createContext<MotionPreferenceValue | null>(null);

export function MotionPreferenceProvider({ children }: { children: ReactNode }) {
  const [reduceMotion, setReduceMotionState] = useState<boolean>(loadPref);

  const setReduceMotion = (v: boolean) => {
    setReduceMotionState(v);
    try {
      localStorage.setItem(STORAGE_KEY, String(v));
    } catch {
      // localStorage unavailable
    }
  };

  return (
    <MotionPreferenceContext.Provider value={{ reduceMotion, setReduceMotion }}>
      <MotionConfig reducedMotion={reduceMotion ? 'always' : 'user'}>{children}</MotionConfig>
    </MotionPreferenceContext.Provider>
  );
}

export function useMotionPreference() {
  const ctx = useContext(MotionPreferenceContext);
  if (!ctx) {
    throw new Error('useMotionPreference must be used within a MotionPreferenceProvider');
  }
  return ctx;
}