crane, util: use url.ResolveReference to build resource paths

2 files changed, 26 insertions, 23 deletions

diff --git a/crane.go b/crane.go
index e3ef9ad..a9d8601 100644
--- a/crane.go
+++ b/crane.go
@@ -30,7 +30,7 @@ const (
 
 var (
 	client      *http.Client
-	scihubURL   string
+	scihubURL   *url.URL
 	host        string
 	port        uint64
 	user        string
@@ -244,8 +244,9 @@ func (papers *Papers) NewPaperFromDOI(doi []byte, category string) (*Paper,
 	tmpXML.Close()
 
 	name := getPaperFileNameFromMeta(meta) // doe2020
+
+	// last-resort if metadata lacking author or publication year
 	if name == "" {
-		// last-resort condition if metadata lacking author or publication year
 		name = strings.Replace(string(doi), "..", "", -1)
 		name = strings.Replace(string(doi), "/", "", -1)
 	}
@@ -253,7 +254,7 @@ func (papers *Papers) NewPaperFromDOI(doi []byte, category string) (*Paper,
 	// doe2020-(2, 3, 4...) if n already exists in set
 	uniqueName := papers.getUniqueName(category, name)
 
-	// if not matching, check if DOIs match (genuine duplicate)
+	// check if DOIs match (genuine duplicate)
 	if name != uniqueName {
 		key := filepath.Join(category, name+".pdf")
 		papers.RLock()
@@ -271,16 +272,13 @@ func (papers *Papers) NewPaperFromDOI(doi []byte, category string) (*Paper,
 		paper.PaperName+".meta.xml")
 
 	// make outbound request to sci-hub, save paper to temporary location
-	url := scihubURL + string(doi)
-	tmpPDF, err := getPaper(client, url)
+	tmpPDF, err := getPaper(client, scihubURL, string(doi))
 	defer os.Remove(tmpPDF)
 	if err != nil {
 		// try passing resource URL (from doi.org metadata) to sci-hub instead
 		// (force cache)
 		if meta.Resource != "" {
-			url = scihubURL + meta.Resource
-			tmpPDF, err = getPaper(client, url)
-			if err != nil {
+			if tmpPDF, err = getPaper(client, scihubURL, meta.Resource); err != nil {
 				return nil, err
 			}
 		} else {
@@ -610,7 +608,9 @@ func main() {
 	var papers Papers
 	papers.List = make(map[string]map[string]*Paper)
 
-	flag.StringVar(&scihubURL, "sci-hub", "https://sci-hub.se/", "Sci-Hub URL")
+	var scihub string
+
+	flag.StringVar(&scihub, "sci-hub", "https://sci-hub.se/", "Sci-Hub URL")
 	flag.StringVar(&papers.Path, "path", "./papers",
 		"Absolute or relative path to papers folder")
 	flag.StringVar(&host, "host", "127.0.0.1", "IP address to listen on")
@@ -621,8 +621,9 @@ func main() {
 
 	papers.Path, _ = filepath.Abs(papers.Path)
 
-	if !strings.HasSuffix(scihubURL, "/") {
-		scihubURL = scihubURL + "/"
+	scihubURL, err = url.Parse(scihub)
+	if err != nil {
+		panic(err)
 	}
 	if _, err := os.Stat(papers.Path); os.IsNotExist(err) {
 		os.Mkdir(papers.Path, os.ModePerm)
diff --git a/util.go b/util.go
index 8fa9c5f..035b519 100644
--- a/util.go
+++ b/util.go
@@ -240,6 +240,7 @@ func getMetaFromDOI(client *http.Client, doi []byte) (*Meta, error) {
 	if err != nil {
 		return nil, err
 	}
+
 	r := bufio.NewReader(resp.Body)
 	d := xml.NewDecoder(r)
 
@@ -254,19 +255,24 @@ func getMetaFromDOI(client *http.Client, doi []byte) (*Meta, error) {
 // getPaper saves makes an outbound request to a remote resource and saves the
 // response body to a temporary file, returning its path, provided the response
 // has the content-type application/pdf
-func getPaper(client *http.Client, u string) (string, error) {
+func getPaper(client *http.Client, scihub *url.URL, resource string) (string, error) {
 
-	resp, err := makeRequest(client, u)
+	ref, err := url.Parse(resource)
 	if err != nil {
 		return "", err
 	}
+	refURL := scihub.ResolveReference(ref) // scihub + resource
 
+	resp, err := makeRequest(client, refURL.String())
+	if err != nil {
+		return "", err
+	}
 	doc, err := html.Parse(resp.Body)
 	if err != nil {
 		return "", err
 	}
 
-	var dl *url.URL
+	var directLink *url.URL
 	var f func(*html.Node)
 	f = func(n *html.Node) {
 		if n.Type == html.ElementNode {
@@ -276,9 +282,8 @@ func getPaper(client *http.Client, u string) (string, error) {
 					if err != nil {
 						continue
 					}
-					fmt.Println(_v.Path)
 					if strings.HasSuffix(_v.Path, "pdf") {
-						dl = _v
+						directLink = scihub.ResolveReference(_v)
 						break
 					}
 				}
@@ -290,25 +295,22 @@ func getPaper(client *http.Client, u string) (string, error) {
 	}
 	f(doc)
 
-	if dl == nil || dl.String() == "" {
-		return "", fmt.Errorf("%q: could not locate PDF direct link", u)
+	if directLink == nil || directLink.String() == "" {
+		return "", fmt.Errorf("%q: could not locate PDF link", refURL.String())
 	}
 
-	resp, err = makeRequest(client, dl.String())
+	resp, err = makeRequest(client, directLink.String())
 	if err != nil {
 		return "", err
 	}
-
 	if resp.Header.Get("content-type") != "application/pdf" {
-		return "", fmt.Errorf("%q: parsed PDF direct link not application/pdf", u)
+		return "", fmt.Errorf("%q: content-type not application/pdf", refURL.String())
 	}
 
 	tmpPDF, err := ioutil.TempFile("", "tmp-*.pdf")
 	if err != nil {
 		return "", err
 	}
-
-	// write resp.Body (paper data) to tmpPDF
 	if err := saveRespBody(resp, tmpPDF.Name()); err != nil {
 		return "", err
 	}