import React, { createContext, useContext, useState, useSyncExternalStore } from 'react';
import { createStore, type Store } from '../state/store.js';

export type VoiceState = {
  voiceState: 'idle' | 'recording' | 'processing';
  voiceError: string | null;
  voiceInterimTranscript: string;
  voiceAudioLevels: number[];
  voiceWarmingUp: boolean;
};

const DEFAULT_STATE: VoiceState = {
  voiceState: 'idle',
  voiceError: null,
  voiceInterimTranscript: '',
  voiceAudioLevels: [],
  voiceWarmingUp: false,
};

type VoiceStore = Store<VoiceState>;

export const VoiceContext = createContext<VoiceStore | null>(null);

type Props = {
  children: React.ReactNode;
};

export function VoiceProvider({ children }: Props): React.ReactNode {
  // Store is created once — stable context value means the provider never
  // triggers re-renders. Consumers subscribe to slices via useVoiceState.
  const [store] = useState(() => createStore<VoiceState>(DEFAULT_STATE));
  return <VoiceContext.Provider value={store}>{children}</VoiceContext.Provider>;
}

function useVoiceStore(): VoiceStore {
  const store = useContext(VoiceContext);
  if (!store) {
    throw new Error('useVoiceState must be used within a VoiceProvider');
  }
  return store;
}

/**
 * Subscribe to a slice of voice state. Only re-renders when the selected
 * value changes (compared via Object.is).
 */
export function useVoiceState<T>(selector: (state: VoiceState) => T): T {
  const store = useVoiceStore();
  const get = () => selector(store.getState());
  return useSyncExternalStore(store.subscribe, get, get);
}

/**
 * Get the voice state setter. Stable reference — never causes re-renders.
 * store.setState is synchronous: callers can read getVoiceState() immediately
 * after to observe the new value (VoiceKeybindingHandler relies on this).
 */
export function useSetVoiceState(): (updater: (prev: VoiceState) => VoiceState) => void {
  return useVoiceStore().setState;
}

/**
 * Get a synchronous reader for fresh state inside callbacks. Unlike
 * useVoiceState (which subscribes), this doesn't cause re-renders — use
 * inside event handlers that need to read state set earlier in the same tick.
 */
export function useGetVoiceState(): () => VoiceState {
  return useVoiceStore().getState;
}