feat: get file stream from link

internal/fs/util.go

@@ -1,10 +1,18 @@
 package fs
 
 import (
-	"github.com/alist-org/alist/v3/internal/driver"
+	"io"
+	"mime"
+	"net/http"
+	"os"
+	stdpath "path"
+	"strings"
+
+	"github.com/alist-org/alist/v3/internal/model"
+	"github.com/pkg/errors"
 )
 
-func containsByName(files []driver.FileInfo, file driver.FileInfo) bool {
+func containsByName(files []model.FileInfo, file model.FileInfo) bool {
 	for _, f := range files {
 		if f.GetName() == file.GetName() {
 			return true
@@ -12,3 +20,46 @@ func containsByName(files []driver.FileInfo, file driver.FileInfo) bool {
 	}
 	return false
 }
+
+var httpClient = &http.Client{}
+
+func getFileStreamFromLink(file model.FileInfo, link *model.Link) (model.FileStreamer, error) {
+	var rc io.ReadCloser
+	mimetype := mime.TypeByExtension(stdpath.Ext(file.GetName()))
+	if link.Data != nil {
+		rc = link.Data
+	} else if link.FilePath != nil {
+		f, err := os.Open(*link.FilePath)
+		if err != nil {
+			return nil, errors.Wrapf(err, "failed to open file %s", *link.FilePath)
+		}
+		rc = f
+	} else {
+		req, err := http.NewRequest(http.MethodGet, link.URL, nil)
+		if err != nil {
+			return nil, errors.Wrapf(err, "failed to create request for %s", link.URL)
+		}
+		for h, val := range link.Header {
+			req.Header[h] = val
+		}
+		res, err := httpClient.Do(req)
+		if err != nil {
+			return nil, errors.Wrapf(err, "failed to get response for %s", link.URL)
+		}
+		mt := res.Header.Get("Content-Type")
+		if mt != "" && strings.ToLower(mt) != "application/octet-stream" {
+			mimetype = mt
+		}
+		rc = res.Body
+	}
+	// if can't get mimetype, use default application/octet-stream
+	if mimetype == "" {
+		mimetype = "application/octet-stream"
+	}
+	stream := model.FileStream{
+		FileInfo:   file,
+		ReadCloser: rc,
+		Mimetype:   mimetype,
+	}
+	return stream, nil
+}