番組 URL から番組を登録する機能を追加（ステップ11）

internal/tver/series.go

@@ -11,6 +11,9 @@ import (
 
 var tverSeriesIDPattern = regexp.MustCompile(`^[A-Za-z0-9]+$`)
 
+// ErrSeriesNotFound は callSeries が HTTP 404 を返したことを表す。
+var ErrSeriesNotFound = errors.New("series not found")
+
 type seriesContents struct {
 	Code   int `json:"code"`
 	Result struct {
@@ -21,6 +24,47 @@ type seriesContents struct {
 	} `json:"result"`
 }
 
+func (c *Client) FetchSeries(ctx context.Context, seriesID string) (string, error) {
+	if !tverSeriesIDPattern.MatchString(seriesID) {
+		return "", errors.New("invalid series id")
+	}
+	session, err := c.CreateSession(ctx)
+	if err != nil {
+		return "", err
+	}
+	endpoint := c.baseURL.ResolveReference(&url.URL{Path: "/service/api/v2/callSeries/" + seriesID})
+	query := endpoint.Query()
+	query.Set("platform_uid", session.PlatformUID)
+	query.Set("platform_token", session.PlatformToken)
+	endpoint.RawQuery = query.Encode()
+	request, err := http.NewRequestWithContext(ctx, http.MethodGet, endpoint.String(), nil)
+	if err != nil {
+		return "", fmt.Errorf("series request: %w", err)
+	}
+	setTVerHeaders(request)
+	var response struct {
+		Code   int `json:"code"`
+		Result struct {
+			Content struct {
+				Content struct {
+					Title string `json:"title"`
+				} `json:"content"`
+			} `json:"content"`
+		} `json:"result"`
+	}
+	if err := c.getJSON(request, &response); err != nil {
+		var statusErr *httpStatusError
+		if errors.As(err, &statusErr) && statusErr.statusCode == http.StatusNotFound {
+			return "", ErrSeriesNotFound
+		}
+		return "", fmt.Errorf("series: %w", err)
+	}
+	if response.Code != 0 || response.Result.Content.Content.Title == "" {
+		return "", fmt.Errorf("series: invalid API result (code %d)", response.Code)
+	}
+	return response.Result.Content.Content.Title, nil
+}
+
 func (c *Client) FetchSeriesEpisodes(ctx context.Context, seriesID string) ([]Episode, error) {
 	if !tverSeriesIDPattern.MatchString(seriesID) {
 		return nil, errors.New("invalid series id")