download kind works

app/webdav.go

@@ -1,5 +1,99 @@
 package app
 
-func (app *Application) initSync() {
+import (
+	"io"
+	"net/http"
+	"os"
+	"time"
 
+	"git.blackforestbytes.com/BlackForestBytes/goext/cryptext"
+	"git.blackforestbytes.com/BlackForestBytes/goext/exerr"
+	"git.blackforestbytes.com/BlackForestBytes/goext/timeext"
+)
+
+func (app *Application) downloadDatabase() (string, time.Time, string, int64, error) {
+
+	client := http.Client{Timeout: 90 * time.Second}
+
+	req, err := http.NewRequest("GET", app.config.WebDAVURL, nil)
+	if err != nil {
+		return "", time.Time{}, "", 0, exerr.Wrap(err, "").Build()
+	}
+
+	req.SetBasicAuth(app.config.WebDAVUser, app.config.WebDAVPass)
+
+	resp, err := client.Do(req)
+	if err != nil {
+		return "", time.Time{}, "", 0, exerr.Wrap(err, "Failed to download remote database").Build()
+	}
+
+	if resp.StatusCode != http.StatusOK {
+		return "", time.Time{}, "", 0, exerr.New(exerr.TypeInternal, "Failed to download remote database").Int("sc", resp.StatusCode).Build()
+	}
+
+	bin, err := io.ReadAll(resp.Body)
+	if err != nil {
+		return "", time.Time{}, "", 0, exerr.Wrap(err, "Failed to read response body").Build()
+	}
+
+	etag := resp.Header.Get("ETag")
+	if etag == "" {
+		return "", time.Time{}, "", 0, exerr.New(exerr.TypeInternal, "ETag header is missing").Build()
+	}
+
+	lmStr := resp.Header.Get("Last-Modified")
+
+	lm, err := time.Parse("Mon, 02 Jan 2006 15:04:05 MST", lmStr)
+	if err != nil {
+		return "", time.Time{}, "", 0, exerr.Wrap(err, "Failed to parse Last-Modified header").Build()
+	}
+
+	lm = lm.In(timeext.TimezoneBerlin)
+
+	sha := cryptext.BytesSha256(bin)
+
+	sz := int64(len(bin))
+
+	err = os.WriteFile(app.dbFile, bin, 0644)
+	if err != nil {
+		return "", time.Time{}, "", 0, exerr.Wrap(err, "Failed to write database file").Build()
+	}
+
+	return etag, lm, sha, sz, nil
+}
+
+func (app *Application) getRemoteETag() (string, time.Time, error) {
+	client := http.Client{Timeout: 90 * time.Second}
+
+	req, err := http.NewRequest("HEAD", app.config.WebDAVURL, nil)
+	if err != nil {
+		return "", time.Time{}, exerr.Wrap(err, "").Build()
+	}
+
+	req.SetBasicAuth(app.config.WebDAVUser, app.config.WebDAVPass)
+
+	resp, err := client.Do(req)
+	if err != nil {
+		return "", time.Time{}, exerr.Wrap(err, "Failed to download remote database").Build()
+	}
+
+	if resp.StatusCode != http.StatusOK {
+		return "", time.Time{}, exerr.New(exerr.TypeInternal, "Failed to download remote database").Int("sc", resp.StatusCode).Build()
+	}
+
+	etag := resp.Header.Get("ETag")
+	if etag == "" {
+		return "", time.Time{}, exerr.New(exerr.TypeInternal, "ETag header is missing").Build()
+	}
+
+	lmStr := resp.Header.Get("Last-Modified")
+
+	lm, err := time.Parse("Mon, 02 Jan 2006 15:04:05 MST", lmStr)
+	if err != nil {
+		return "", time.Time{}, exerr.Wrap(err, "Failed to parse Last-Modified header").Build()
+	}
+
+	lm = lm.In(timeext.TimezoneBerlin)
+
+	return etag, lm, nil
 }