class Init extends HTMLElement {
    #AppName = "customs-portal";

    constructor() {
        super();
    }    

    async connectedCallback() {
        await this.#CheckStorage();

        const LocalVersion = await this.#GetValue(`${this.#AppName}_version`) || -1;

        // Append local version to compare in endpoint, inject version to prevent browser caching this resource
        const Response = await fetch(`customs-portal/package?v=${LocalVersion}c=27387963`);

        if (Response.status == 200) {
            const ResponseObj = await Response.json();

            if (ResponseObj.version > LocalVersion) {
                await this.#SetValue(`${this.#AppName}_version`, ResponseObj.version);
                await this.#SetValue(`${this.#AppName}_data`, JSON.stringify(ResponseObj.data));
                await this.#SetValue(`${this.#AppName}_info`, JSON.stringify(ResponseObj.info));
                await this.#SetValue(`${this.#AppName}_changelog`, JSON.stringify(ResponseObj.changelog));
            }

            const Package = document.createElement("script");
            Package.innerHTML = JSON.parse(await this.#GetValue(`${this.#AppName}_data`));
            document.head.appendChild(Package);

            new App();
        }
    }

    #DB;

    async #CheckStorage() {
        await new Promise(async (resolve, reject) => {
            const Req = window.indexedDB.open(`${this.#AppName}-db`, 5);
            Req.onerror = () => {
                reject("Could not open app database.");
            };
            Req.onsuccess = () => {
                this.#DB = Req.result;
                resolve();
            };

            Req.onupgradeneeded = (e) => {
                this.#CheckSchema(e);
            };
        });
    }

    #CheckSchema(e) {
        const DB = e.target.result;

        if (!DB.objectStoreNames.contains("main")) {
            DB.createObjectStore("main");
        } 
    };

    async #GetValue(Key) {
        return await new Promise(async (resolve, reject) => {
            const Request = this.#DB.transaction("main", "readwrite").objectStore("main").get(Key);

            Request.onerror = () => {
                reject();
            };

            Request.onsuccess = () => {
                resolve(Request.result);
            };
        });
    }

    async #SetValue(Key, Value) {
        await new Promise(async (resolve, reject) => {
            const Request = this.#DB.transaction("main", "readwrite").objectStore("main").put(Value, Key);

            Request.onerror = () => {
                reject();
            };

            Request.onsuccess = () => {
                resolve();
            };
        });
    }
}

customElements.define("app-init", Init);