import type { SdkConfiguration, AccessToken, ICachingStrategy } from "../types.js";
import AccessTokenHelpers from "./AccessTokenHelpers.js";
import IAuthStrategy, { emptyAccessToken } from "./IAuthStrategy.js";

export default class ImplicitGrantStrategy implements IAuthStrategy {

    private static readonly cacheKey = "spotify-sdk:ImplicitGrantStrategy:token";
    private configuration: SdkConfiguration | null = null;
    private get cache(): ICachingStrategy { return this.configuration!.cachingStrategy; }

    constructor(
        private clientId: string,
        private redirectUri: string,
        private scopes: string[]
    ) {
    }

    public setConfiguration(configuration: SdkConfiguration): void {
        this.configuration = configuration;
    }

    public async getOrCreateAccessToken(): Promise<AccessToken> {
        const token = await this.cache.getOrCreate<AccessToken>(
            ImplicitGrantStrategy.cacheKey,
            async () => {
                const token = await this.redirectOrVerifyToken();
                return AccessTokenHelpers.toCachable(token);
            }, async (expiring) => {
                return AccessTokenHelpers.refreshCachedAccessToken(this.clientId, expiring);
            },
        );

        return token;
    }

    public async getAccessToken(): Promise<AccessToken | null> {
        const token = await this.cache.get<AccessToken>(ImplicitGrantStrategy.cacheKey);
        return token;
    }

    public removeAccessToken(): void {
        this.cache.remove(ImplicitGrantStrategy.cacheKey);
    }

    private async redirectOrVerifyToken(): Promise<AccessToken> {
        const hashParams = new URLSearchParams(window.location.hash.substring(1));
        const accessToken = hashParams.get("access_token");

        if (accessToken) {
            return Promise.resolve({
                access_token: accessToken,
                token_type: hashParams.get("token_type") ?? "",
                expires_in: parseInt(hashParams.get("expires_in") ?? "0"),
                refresh_token: hashParams.get("refresh_token") ?? "",
                expires: Number(hashParams.get("expires")) || 0
            });
        }

        const scopes = this.scopes ?? [];
        var scope = scopes.join(' ');

        const params = new URLSearchParams();
        params.append("client_id", this.clientId);
        params.append("response_type", "token");
        params.append("redirect_uri", this.redirectUri);
        params.append("scope", scope);

        const authUrl = 'https://accounts.spotify.com/authorize?' + params.toString();

        this.configuration!.redirectionStrategy.redirect(authUrl);
        return emptyAccessToken;
    }
}