/** In memory storage.
 * This in memory storage implements the methods of localForage.
 */

export class Storage {
    storage: { [key: string]: any }

    constructor() {
        this.storage = {}
    }

    getItem = <T>(key: string): Promise<T | null> => {
        return new Promise(resolve => {
            const val = this.storage[key] || null

            // https://localforage.github.io/localForage/#data-api-getitem
            // "Even if undefined is saved, null will be returned by getItem(). 
            // This is due to a limitation in localStorage, and for compatibility 
            // reasons localForage cannot store the value undefined."
            const checkedVal = val === undefined ? null : val

            resolve(checkedVal)
        })
    }

    setItem = <T>(key: string, val: T): Promise<T> => {
        return new Promise(resolve => {
            this.storage[key] = val
            resolve(val)
        })
    }

    removeItem = (key: string): Promise<void> => {
        return new Promise(resolve => {
            delete this.storage[key]
            resolve()
        })
    }

    clear = (): Promise<void> => {
        return new Promise(resolve => {
            this.storage = {}
            resolve()
        })
    }
}