template/src/main/js/Storage.ts

/**
 * Stores key-value pairs.
 */
export interface Storage {
    /**
     * Removes the data from storage.
     */
    clear(): void;

    /**
     * Retrieves an array from storage.
     *
     * @param name the name of the array to retrieve
     * @param def the value to return if no array is stored with the given name
     */
    getArray(name: string, def: any[]): any[];

    /**
     * Stores an array.
     *
     * @param name the name of the array to store
     * @param value the array to store under the given name
     */
    setArray(name: string, value: any[]): void;

    /**
     * Retrieves a boolean from storage.
     *
     * @param name the name of the boolean to retrieve
     * @param def the value to return if no boolean is stored with the given name
     */
    getBoolean(name: string, def: boolean): boolean;

    /**
     * Stores a boolean.
     *
     * @param name the name of the boolean to store
     * @param value the boolean to store under the given name
     */
    setBoolean(name: string, value: boolean): void;

    /**
     * Retrieves a number from storage.
     *
     * @param name the name of the number to retrieve
     * @param def the value to return if no number is stored with the given name
     */
    getNumber(name: string, def: number): number;

    /**
     * Stores a number.
     *
     * @param name the name of the number to store
     * @param value the number to store under the given name
     */
    setNumber(name: string, value: number): void;

    /**
     * Retrieves a string from storage.
     *
     * @param name the name of the string to retrieve
     * @param def the value to return if no string is stored with the given name
     */
    getString(name: string, def: string): string;

    /**
     * Stores a string.
     *
     * @param name the name of the string to store
     * @param value the number to store under the given name
     */
    setString(name: string, value: string): void;
}

/**
 * Stores key-value pairs in a single entry in `localStorage`.
 */
export class LocalStorage implements Storage {
    private readonly key: string;
    private cache: { [key: string]: string } | null = null;


    /**
     * Constructs a new persistent storage item under the given key.
     *
     * @param key the unique identifier to store the data under
     */
    constructor(key: string) {
        this.key = key;
    }


    /**
     * Reads the object stored in local storage.
     *
     * @return the object stored in local storage, or an empty object if there is nothing in the local storage
     * @private
     */
    private read(): { [key: string]: string } {
        if (this.cache === null)
            this.cache = JSON.parse(localStorage.getItem(this.key) ?? "{}");

        return this.cache!;
    }

    /**
     * Writes the given object to local storage.
     *
     * @param item the object to write to local storage
     * @private
     */
    private write(item: { [key: string]: string }): void {
        this.cache = item;
        localStorage.setItem(this.key, JSON.stringify(item));
    }


    clear(): void {
        this.cache = null;
        localStorage.removeItem(this.key);
    }

    getArray(name: string, def: any[] = []): any[] {
        const array = this.read()[name];
        return array === undefined ? def : JSON.parse(array);
    }

    setArray(name: string, value: any[]): void {
        this.setString(name, JSON.stringify(value));
    }

    getBoolean(name: string, def: boolean = false): boolean {
        return this.getString(name, def ? "true" : "false") === "true";
    }

    setBoolean(name: string, value: boolean): void {
        this.setString(name, "" + value);
    }

    getNumber(name: string, def: number = 0): number {
        return +this.getString(name, "" + def);
    }

    setNumber(name: string, value: number): void {
        this.setString(name, "" + value);
    }

    getString(name: string, def: string = ""): string {
        return this.read()[name] ?? def;
    }

    setString(name: string, value: string): void {
        const item = this.read();
        item[name] = value;
        this.write(item);
    }
}

/**
 * Stores key-value pairs in an object.
 */
export class MemoryStorage implements Storage {
    private storage: { [key: string]: any } = {};


    clear(): void {
        this.storage = {};
    }

    setArray(name: string, value: any[] = []): void {
        this.storage[name] = value;
    }

    getArray(name: string, def: any[]): any[] {
        return this.storage[name] ?? def;
    }

    setBoolean(name: string, value: boolean): void {
        this.storage[name] = value;
    }

    getBoolean(name: string, def: boolean): boolean {
        return this.storage[name] ?? def;
    }

    setNumber(name: string, value: number): void {
        this.storage[name] = value;
    }

    getNumber(name: string, def: number): number {
        return this.storage[name] ?? def;
    }

    setString(name: string, value: string): void {
        this.storage[name] = value;
    }

    getString(name: string, def: string): string {
        return this.storage[name] ?? def;
    }
}