const axios = require('axios');
const qs = require('qs');


class OAuth2Client {
    constructor(config) {
        this.tokenUrl = config.token_url;
        this.introspectionUrl = config.introspection_url;
        this.clientId = config.client_id;
        this.clientSecret = config.client_secret;

        const authUrl = config.authorization_url;
        const authArgs = new URLSearchParams({
            response_type: 'code',
            client_id: this.clientId
        }).toString();
        this.authUrl = `${authUrl}?${authArgs}`;

        this.session = axios.create({
            auth: {
                username: this.clientId,
                password: this.clientSecret
            },
            headers: {
                'Content-Type': 'application/x-www-form-urlencoded'
            }
        });
    }

    async exchangeCodeForToken(code) {
        const data = qs.stringify({
            grant_type: 'authorization_code',
            code,
            client_id: this.clientId,
            client_secret: this.clientSecret
        });

        const response = await axios.post(this.tokenUrl, data, {
            headers: { 'Content-Type': 'application/x-www-form-urlencoded' }
        });

        return response.data;
    }

    async introspectToken(token) {
        const data = qs.stringify({
            token,
            client_id: this.clientId,
            client_secret: this.clientSecret
        });

        const response = await axios.post(this.introspectionUrl, data, {
            headers: { 'Content-Type': 'application/x-www-form-urlencoded' }
        });

        return response.data;
    }

}

module.exports = OAuth2Client