1 files changed, 109 insertions, 0 deletions
diff --git a/config-lib/src/main/java/com/yahoo/config/ModelReference.java b/config-lib/src/main/java/com/yahoo/config/ModelReference.java
new file mode 100644
index 00000000000..c0b610e4df3
--- /dev/null
+++ b/config-lib/src/main/java/com/yahoo/config/ModelReference.java
@@ -0,0 +1,109 @@
+// Copyright Yahoo. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
+package com.yahoo.config;
+
+import java.io.File;
+import java.util.Objects;
+import java.util.Optional;
+
+/**
+ * An immutable reference to a model.
+ * This is a file path when read by a client but is set in a config instance either as a
+ * path, url or id resolved to an url during deployment.
+ *
+ * @author bratseth
+ */
+public class ModelReference {
+
+    // At least one of these are set
+    private final Optional<String> modelId;
+    private final Optional<UrlReference> url;
+    private final Optional<FileReference> path;
+
+    public ModelReference(Optional<String> modelId,
+                          Optional<UrlReference> url,
+                          Optional<FileReference> path) {
+        if (modelId.isEmpty() && url.isEmpty() && path.isEmpty())
+            throw new IllegalArgumentException("A model reference must have either a model id, url or path");
+        this.modelId = modelId;
+        this.url = url;
+        this.path = path;
+    }
+
+    public Optional<String> modelId() { return modelId; }
+    public Optional<UrlReference> url() { return url; }
+    public Optional<FileReference> path() { return path; }
+
+    public ModelReference withModelId(Optional<String> modelId) {
+        return new ModelReference(modelId, url, path);
+    }
+
+    public ModelReference withUrl(Optional<UrlReference> url) {
+        return new ModelReference(modelId, url, path);
+    }
+
+    public ModelReference withPath(Optional<FileReference> path) {
+        return new ModelReference(modelId, url, path);
+    }
+
+    /** Returns the path to the file containing this model. */
+    public String value() {
+        if (url.isPresent() && new File(url.get().value()).exists())
+            return new File(url.get().value()).getAbsolutePath();
+        if (path.isPresent())
+            return path.get().value();
+        throw new IllegalStateException("No url or path is available");
+    }
+
+    @Override
+    public boolean equals(Object o) {
+        if ( ! (o instanceof ModelReference other)) return false;
+        if ( ! this.modelId.equals(other.modelId)) return false;
+        if ( ! this.url.equals(other.url)) return false;
+        if ( ! this.path.equals(other.path)) return false;
+        return true;
+    }
+
+    @Override
+    public int hashCode() {
+        return Objects.hash(modelId, url, path);
+    }
+
+    /** Returns this on the format accepted by valueOf */
+    @Override
+    public String toString() {
+        return modelId.orElse("") + " " +
+               url.map(v -> v.value()).orElse("") + " " +
+               path.map(v -> v.value()).orElse("");
+    }
+
+    /** Creates a model reference having a model id only. */
+    public static ModelReference fromModelId(String modelId) {
+        return new ModelReference(Optional.of(modelId), Optional.empty(), Optional.empty());
+    }
+
+    /** Creates a model reference having a url only. */
+    public static ModelReference fromUrl(String url) {
+        return new ModelReference(Optional.empty(), Optional.of(new UrlReference(url)), Optional.empty());
+    }
+
+    /** Creates a model reference having a path only. */
+    public static ModelReference fromPath(String path) {
+        return new ModelReference(Optional.empty(), Optional.empty(), Optional.of(new FileReference(path)));
+    }
+
+    /**
+     * Creates a model reference from a three-part string on the form
+     * <code>modelId url path</code>
+     * Each of the elements are either a value not containing space, or empty represented by "".
+     */
+    public static ModelReference valueOf(String s) {
+        String[] parts = s.split(" ");
+        if (parts.length != 3)
+            throw new IllegalArgumentException("Expected a config with exactly three space-separated parts, but got '" + s + "'");
+        return new ModelReference(parts[0].equals("") ? Optional.empty() : Optional.of(parts[0]),
+                                  parts[1].equals("") ? Optional.empty() : Optional.of(new UrlReference(parts[1])),
+                                  parts[2].equals("") ? Optional.empty() : Optional.of(new FileReference(parts[2])));
+
+    }
+
+}