Feature: bi5 downloader will download to temp folder before moving it…

… to final destination location.

This reduce the likelyhood for file to be corrupted in the even of program being stopped while downloading
Bug: Panic will occur when the requested ticks#Goto target is during weekend.

api/tickdata/ticks/ticks.go

@@ -69,7 +69,7 @@ func (t *Ticks) Goto(to time.Time) (isSuccess bool, err error) {
 		return false, errors.New("[" + to.String() + "] is after [" + t.end.String() + "]")
 	}
 
-	to = to.In(time.UTC) // Done to ease debugging
+	to = to.In(time.UTC) // To ease debugging
 	t.isCompleted = false
 	for currTime := t.timeToHour(to); currTime.Before(t.end); currTime = currTime.Add(time.Hour) {
 		if t.ticksDayHour.Equal(currTime) {
@@ -80,12 +80,12 @@ func (t *Ticks) Goto(to time.Time) (isSuccess bool, err error) {
 			// Download might return errors when there's no tick data during weekend or holiday
 			if bi.Download() == nil {
 				t.ticks, err = bi.Ticks()
+				t.ticksIdx = 0
+				t.ticksDayHour = currTime
 				if err != nil {
 					t.complete()
 					return
 				} else if len(t.ticks) != 0 {
-					t.ticksIdx = 0
-					t.ticksDayHour = currTime
 					t.seek(to)
 					return true, nil
 				}

internal/core/fetch.go

@@ -4,6 +4,7 @@ import (
 	"fmt"
 	"github.com/pkg/errors"
 	"io"
+	"io/ioutil"
 	"net/http"
 	"os"
 	"path/filepath"
@@ -51,7 +52,7 @@ func (h HTTPDownload) Download(URL string, toFilePath string) (httpStatusCode in
 				break
 			}
 
-			log.Warn("[%d] Download %s failed %d:%s. Retrying", retry, URL, httpStatusCode, resp.Status)
+			log.Trace("[%d] Download %s failed %d:%s. Retrying", retry, URL, httpStatusCode, resp.Status)
 			err = fmt.Errorf("http error %d:%s", resp.StatusCode, resp.Status)
 			h.delay()
 			continue
@@ -69,26 +70,39 @@ func (h HTTPDownload) delay() {
 }
 
 func (h HTTPDownload) saveBodyToDisk(body io.ReadCloser, path string) (filesize int64, err error) {
-	// Create dir if not exists
+	tempFile, err := ioutil.TempFile(os.TempDir(), "go-duka.download.*.temp")
+	if err != nil {
+		return 0, errors.New("Failed to create temp file for download")
+	}
+	tempFileName := tempFile.Name()
+	defer func() {
+		if err != nil {
+			_ = tempFile.Close()
+			_ = os.Remove(tempFileName)
+		}
+	}()
+
+	filesize, err = io.Copy(tempFile, body)
+	if err != nil {
+		err = errors.Wrap(err, "Saving tick data ["+tempFileName+"] Failed")
+		return
+	}
+
 	dir := filepath.Dir(path)
 	err = os.MkdirAll(dir, 0755)
 	if err != nil {
 		err = errors.Wrap(err, "Create folder ["+dir+"] failed")
 		return
 	}
 
-	f, err := os.OpenFile(path, os.O_CREATE|os.O_TRUNC|os.O_RDWR, 0666)
+	err = tempFile.Close()
 	if err != nil {
-		err = errors.Wrap(err, "Create file ["+path+"] failed")
+		err = errors.Wrap(err, "Failed to close tick data ["+tempFileName+"] file")
 		return
 	}
-
-	defer f.Close()
-	filesize, err = io.Copy(f, body)
+	err = os.Rename(tempFileName, path)
 	if err != nil {
-		err = errors.Wrap(err, "Saving tick data ["+path+"] failed")
-		return
+		err = errors.Wrap(err, "Failed to move tick data to ["+path+"]")
 	}
-
 	return
 }