feat: implement telegram bot plugin (#1740)

plugin/telegram/download.go

@@ -0,0 +1,44 @@
+package telegram
+
+import (
+	"context"
+	"fmt"
+	"io"
+	"net/http"
+)
+
+// downloadFileId download file with fileID, return the filepath and blob.
+func (r *Robot) downloadFileID(ctx context.Context, fileID string) (string, []byte, error) {
+	file, err := r.GetFile(ctx, fileID)
+	if err != nil {
+		return "", nil, err
+	}
+	blob, err := r.downloadFilepath(ctx, file.FilePath)
+	if err != nil {
+		return "", nil, err
+	}
+
+	return file.FilePath, blob, nil
+}
+
+// downloadFilepath download file with filepath, you can get filepath by calling GetFile.
+func (r *Robot) downloadFilepath(ctx context.Context, filePath string) ([]byte, error) {
+	token := r.handler.RobotToken(ctx)
+	if token == "" {
+		return nil, ErrNoToken
+	}
+
+	uri := "https://api.telegram.org/file/bot" + token + "/" + filePath
+	resp, err := http.Get(uri)
+	if err != nil {
+		return nil, fmt.Errorf("fail to http.Get: %s", err)
+	}
+	defer resp.Body.Close()
+
+	body, err := io.ReadAll(resp.Body)
+	if err != nil {
+		return nil, fmt.Errorf("fail to io.ReadAll: %s", err)
+	}
+
+	return body, nil
+}