rss-tools @ 70f8cb6

package twitch

import (

	"context"

	"encoding/json"

	"fmt"

	"html"

	"io"

	"log/slog"

	"net/http"

	"net/url"

	"strings"

	"sync"

	"time"

	"olexsmir.xyz/rss-tools/app"

	"olexsmir.xyz/rss-tools/app/atom"

)

var defaultHTTPClient = &http.Client{Timeout: 10 * time.Second}

const (

	twitchAPIBase     = "https://api.twitch.tv"

	tokenExpiryBuffer = 5 * time.Minute

)

var twitchAuthBase = "https://id.twitch.tv"

type twitchStream struct {

	ID           string `json:"id"`

	UserLogin    string `json:"user_login"`

	UserName     string `json:"user_name"`

	GameName     string `json:"game_name"`

	Title        string `json:"title"`

	ViewerCount  int    `json:"viewer_count"`

	StartedAt    string `json:"started_at"`

	ThumbnailURL string `json:"thumbnail_url"`

}

type twitchStreamsResponse struct {

	Data []twitchStream `json:"data"`

}

type twitchAuthResponse struct {

	AccessToken string `json:"access_token"`

	ExpiresIn   int    `json:"expires_in"`

	TokenType   string `json:"token_type"`

}

type twitchfeed struct {

	clientID     string

	clientSecret string

	baseURL      string

	client       *http.Client

	mu       sync.Mutex

	token    string

	tokenExp time.Time

}

func Register(a *app.App) error {

	if a.Config.TwitchClientID == "" || a.Config.TwitchClientSecret == "" {

		a.Logger.Info("twitch: client_id or client_secret not set, skipping")

		return nil

	}

	tf := &twitchfeed{

		clientID:     a.Config.TwitchClientID,

		clientSecret: a.Config.TwitchClientSecret,

		baseURL:      twitchAPIBase,

		client:       defaultHTTPClient,

	}

	a.Route("GET /twitch/__oauth2", tf.handleTokenStatus)

	a.Route("GET /twitch/{name}", tf.handleStreams)

	a.Logger.Info("twitch source registered")

	return nil

}

func (tf *twitchfeed) handleStreams(w http.ResponseWriter, r *http.Request) {

	name := r.PathValue("name")

	if name == "" || name == "__oauth2" {

		http.Error(w, "missing streamer name", http.StatusBadRequest)

		return

	}

	stream, err := tf.do(r.Context(), name)

	if err != nil {

		slog.Error("twitch: fetch failed", "user", name, "err", err)

		http.Error(w, err.Error(), http.StatusInternalServerError)

		return

	}

	feed := atom.NewFeed("Twitch: "+name, "twitch:"+name)

	if stream != nil {

		feed.Add(entryFromStream(stream))

	}

	if err := feed.Render(w); err != nil {

		http.Error(w, err.Error(), http.StatusInternalServerError)

	}

}

func (tf *twitchfeed) handleTokenStatus(w http.ResponseWriter, r *http.Request) {

	tf.mu.Lock()

	tok := tf.token

	exp := tf.tokenExp

	tf.mu.Unlock()

	info := map[string]any{

		"client_id_set":     tf.clientID != "",

		"secret_configured": tf.clientSecret != "",

		"token_cached":      tok != "",

	}

	if tok != "" {

		info["token_length"] = len(tok)

		info["expires_at"] = exp.Format(time.RFC3339)

		info["expired"] = time.Now().After(exp)

		if len(tok) > 8 {

			info["preview"] = tok[:4] + "..." + tok[len(tok)-4:]

		}

	}

	w.Header().Set("Content-Type", "application/json")

	json.NewEncoder(w).Encode(info)

}

func (tf *twitchfeed) do(ctx context.Context, login string) (*twitchStream, error) {

	tok, err := tf.getToken(ctx)

	if err != nil {

		return nil, fmt.Errorf("auth: %w", err)

	}

	stream, err := tf.fetchStream(ctx, tok, login)

	if err != nil {

		return nil, err

	}

	return stream, nil

}

func (tf *twitchfeed) getToken(ctx context.Context) (string, error) {

	tf.mu.Lock()

	hasToken := tf.token != ""

	expired := time.Now().After(tf.tokenExp)

	tf.mu.Unlock()

	if hasToken && !expired {

		return tf.token, nil

	}

	return tf.authenticate(ctx)

}

func (tf *twitchfeed) authenticate(ctx context.Context) (string, error) {

	v := url.Values{

		"client_id":     {tf.clientID},

		"client_secret": {tf.clientSecret},

		"grant_type":    {"client_credentials"},

	}

	resp, err := tf.client.PostForm(twitchAuthBase+"/oauth2/token", v)

	if err != nil {

		return "", fmt.Errorf("token request: %w", err)

	}

	defer resp.Body.Close()

	if resp.StatusCode != http.StatusOK {

		body, _ := io.ReadAll(resp.Body)

		return "", fmt.Errorf("token endpoint: %s %s", resp.Status, body)

	}

	var auth twitchAuthResponse

	if err := json.NewDecoder(resp.Body).Decode(&auth); err != nil {

		return "", fmt.Errorf("token decode: %w", err)

	}

	tf.mu.Lock()

	tf.token = auth.AccessToken

	tf.tokenExp = time.Now().Add(time.Duration(auth.ExpiresIn)*time.Second - tokenExpiryBuffer)

	tf.mu.Unlock()

	slog.Info("twitch: new token obtained", "expires_in", auth.ExpiresIn)

	return auth.AccessToken, nil

}

func (tf *twitchfeed) fetchStream(ctx context.Context, token, login string) (*twitchStream, error) {

	u := tf.baseURL + "/helix/streams?user_login=" + login

	req, err := http.NewRequestWithContext(ctx, http.MethodGet, u, nil)

	if err != nil {

		return nil, fmt.Errorf("creating request: %w", err)

	}

	req.Header.Set("Authorization", "Bearer "+token)

	req.Header.Set("Client-Id", tf.clientID)

	resp, err := tf.client.Do(req)

	if err != nil {

		return nil, fmt.Errorf("fetching streams: %w", err)

	}

	defer resp.Body.Close()

	if resp.StatusCode == http.StatusUnauthorized {

		tf.mu.Lock()

		tf.token = ""

		tf.mu.Unlock()

		return nil, fmt.Errorf("twitch API: %s", resp.Status)

	}

	if resp.StatusCode != http.StatusOK {

		return nil, fmt.Errorf("twitch API: %s", resp.Status)

	}

	var result twitchStreamsResponse

	if err := json.NewDecoder(resp.Body).Decode(&result); err != nil {

		return nil, fmt.Errorf("decoding response: %w", err)

	}

	if len(result.Data) == 0 {

		return nil, nil

	}

	return &result.Data[0], nil

}

func entryFromStream(s *twitchStream) *atom.Entry {

	title := fmt.Sprintf("%s — %s", s.UserName, s.Title)

	if len(title) > 80 {

		title = title[:80] + "…"

	}

	thumbnail := strings.NewReplacer("{width}", "640", "{height}", "360").Replace(s.ThumbnailURL)

	startedAt, _ := time.Parse(time.RFC3339, s.StartedAt)

	content := fmt.Sprintf(

		"<p>Playing <b>%s</b> · %d viewers</p>",

		html.EscapeString(s.GameName), s.ViewerCount,

	)

	if thumbnail != "" {

		content += fmt.Sprintf(`<p><img src="%s" alt="%s stream"/></p>`,

			html.EscapeString(thumbnail), html.EscapeString(s.UserName))

	}

	login := s.UserLogin

	if login == "" {

		login = s.UserName

	}

	return &atom.Entry{

		ID:      "twitch-stream-" + s.ID,

		Title:   title,

		Content: atom.NewText(content, "html"),

		Updated: atom.Time(startedAt),

		Link: []atom.Link{

			{Rel: "alternate", Href: "https://twitch.tv/" + login},

		},

	}

}