import type { GridState } from './types'
import type { Actions } from './actions'
import { INITIAL_STATE } from '.'
import reducer from './reducer'
import type { StoreSelectors } from './selectors'
import { createSelectors } from './selectors'

export type Store = {
    subscribe: (listener: () => void) => () => void
    dispatch: (action: Actions) => void
    getState: () => GridState
    selectors: StoreSelectors
}

export function createStore(): Store {
    let state = { ...INITIAL_STATE }
    const listeners = new Set<() => void>()

    const subscribe = (listener: () => void) => {
        listeners.add(listener)
        return () => {
            listeners.delete(listener)
        }
    }

    const notify = () => {
        listeners.forEach((l) => l())
    }

    const dispatch = (action: Actions) => {
        const currentState = state
        state = reducer(state, action)
        if (currentState !== state) {
            notify()
        }
    }

    const getState = () => state

    const selectors = createSelectors()

    return { subscribe, dispatch, getState, selectors }
}