// Spotify Web API actions
function generateCodeVerifier(length = 128) {
    const possible = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-._~';
    let code_verifier = '';
    for (let i = 0; i < length; i++) {
        code_verifier += possible.charAt(Math.floor(Math.random() * possible.length));
    }
    return code_verifier;
}

async function generateCodeChallenge(code_verifier) {
    const digest = await crypto.subtle.digest('SHA-256', new TextEncoder().encode(code_verifier));
    return btoa(String.fromCharCode(...new Uint8Array(digest)))
        .replace(/\+/g, '-').replace(/\//g, '_').replace(/=+$/, '');
}

const client_id = '5ed07e2a23384be495efff4d463aba54';
const redirect_uri = window.location.origin + window.location.pathname;
const scope = 'user-read-private user-read-email user-read-playback-state user-read-currently-playing';

export function loginWithSpotify() {
    const code_verifier = generateCodeVerifier();
    localStorage.setItem('code_verifier', code_verifier);
    generateCodeChallenge(code_verifier).then(code_challenge => {
        const params = new URLSearchParams({
            response_type: 'code',
            client_id,
            scope,
            redirect_uri,
            code_challenge_method: 'S256',
            code_challenge
        });
        window.location = 'https://accounts.spotify.com/authorize?' + params.toString();
    });
}

export async function handleRedirect() {
    const params = new URLSearchParams(window.location.search);
    const code = params.get('code');
    if (!code) return null;

    const code_verifier = localStorage.getItem('code_verifier');
    const body = new URLSearchParams({
        client_id,
        grant_type: 'authorization_code',
        code,
        redirect_uri,
        code_verifier
    });

    const response = await fetch('https://accounts.spotify.com/api/token', {
        method: 'POST',
        headers: { 'Content-Type': 'application/x-www-form-urlencoded' },
        body
    });
    const data = await response.json();
    if (data.access_token) {
        window.history.replaceState({}, document.title, window.location.pathname);
        localStorage.removeItem('code_verifier');
        localStorage.setItem('access_token', data.access_token);
        return data.access_token;
    } else {
        document.getElementById('error-msg').textContent = 'Error: ' + JSON.stringify(data, null, 2);
        return null;
    }
}

// --- Profile and Current Track ---
export async function getProfile(access_token) {
    const res = await fetch('https://api.spotify.com/v1/me', {
        headers: { Authorization: 'Bearer ' + access_token }
    });
    if (!res.ok) return null;
    return await res.json();
}

export async function getCurrentTrack(access_token) {
    const res = await fetch('https://api.spotify.com/v1/me/player/currently-playing', {
        headers: { Authorization: 'Bearer ' + access_token }
    });
    if (res.status === 204 || !res.ok) return null;
    return await res.json();
}

async function playerCommand(access_token, endpoint, method='POST') {
    const response = await fetch(`https://api.spotify.com/v1/me/player/${endpoint}`, {
        method,
        headers: { Authorization: 'Bearer ' + access_token }
    });
    if (!response.ok) {
        const text = await response.text();
        document.getElementById('data').innerText = `Spotify API Error (${endpoint}): ${response.status} ${text}`;
        console.error(`Spotify API Error (${endpoint}):`, response.status, text);
    }
}