First working version

- Move from separate dirs for upload to a unified one (identify
  media/metadata files by file extension)
- Prevent uploading when an import is already scheduled
- Allow setting custom, parser-specific settings
- Add CLI
- Implement WebDAV upload
- Implement checking of upload folders for uploadable contents

Close #6, close #7, close #9, close #3, close #1, close #4

src/webdavupload/CheckRemoteContents.go

@@ -0,0 +1,115 @@
+package webdavupload
+
+import (
+    "os"
+    "sync"
+    "time"
+    "github.com/studio-b12/gowebdav"
+    "gitea.armuli.eu/museum-digital/museum-digital-webdav-uploader/src/configloader"
+)
+
+// Takes a path on the webdav remote and reads folder contents from it.
+func listWebDavFolderContents(config configloader.MDWebDavUploaderConfig, path string) ([]os.FileInfo, error) {
+
+    c := gowebdav.NewClient(getWebDavHost(config), config.Username, config.WebDavAuthToken)
+    c.Connect()
+
+    files, err := c.ReadDir(path)
+    return files, err
+
+}
+
+// Returns a list of the files on the top level of the remote.
+func ListTopLevelContents(config configloader.MDWebDavUploaderConfig) ([]os.FileInfo, error) {
+    return listWebDavFolderContents(config, ".")
+}
+
+// Returns a list of the files in the current metadata dir of the remote.
+func ListMetadataDir(config configloader.MDWebDavUploaderConfig) ([]os.FileInfo, error) {
+    return listWebDavFolderContents(config, "./IMPORT_XML")
+}
+
+// Returns a list of the files in the current media dir of the remote.
+func ListMediaDir(config configloader.MDWebDavUploaderConfig) ([]os.FileInfo, error) {
+    return listWebDavFolderContents(config, "./IMPORT_IMG")
+}
+
+func checkImportConfigExists(c *gowebdav.Client) bool {
+
+    _, err := c.Stat("./import_config.txt")
+    if gowebdav.IsErrNotFound(err) == true {
+        return false
+    }
+    return true
+
+}
+
+// Checks if a remote directory is free for updating:
+// This means it can be read, and it does not contain files more recent than
+// 10 minutes.
+func checkRemoteDirIsFree(c *gowebdav.Client, path string) bool {
+
+    now := time.Now()
+
+    // Check metadata dir
+    files, err := c.ReadDir(path)
+
+    if err != nil {
+        print("Failed to load remote contents")
+        return false
+    }
+
+    for _, f := range(files) {
+        if diff := now.Sub(f.ModTime()); diff < 10 * time.Minute {
+            print("File " + f.Name() + " has been recently renamed")
+            return false
+        }
+    }
+
+    return true
+
+}
+
+// Checks if either the metadata or the image folder contains files that have
+// been changed in the last 10 minutes.
+// In this case, it can be assumed that there is a concurrent upload taking place.
+func checkRemoteImportFilesAreTooRecent(c *gowebdav.Client) bool {
+
+    var wg sync.WaitGroup
+    var metadataDirFree bool
+    var mediaDirFree bool
+
+    wg.Add(2)
+    go func() {
+        defer wg.Done()
+        metadataDirFree = checkRemoteDirIsFree(c, "./IMPORT_XML")
+    }()
+    go func() {
+        defer wg.Done()
+        mediaDirFree = checkRemoteDirIsFree(c, "./IMPORT_IMG")
+    }()
+    wg.Wait()
+
+    if metadataDirFree == true && mediaDirFree == true {
+        return false
+    }
+    return true
+
+}
+
+// Checks the remote for the existence of an import_config.txt.
+func CheckRemoteIsFree(c *gowebdav.Client) bool {
+
+    if checkImportConfigExists(c) == true {
+        return false
+    }
+
+    // Check if the remote media and metadata directories currently
+    // contain very recent files indicating a concurrent upload.
+    if checkRemoteImportFilesAreTooRecent(c) == true {
+        return false
+    }
+
+    return true
+
+}