Add supportsScheme function to BaseProvider and adjust MappingBrowser…

… accordingly

Preparation for #289.

src/components/MappingBrowser.vue

@@ -630,7 +630,14 @@ export default {
       return object
     },
     mappingRegistries() {
-      let registries = this.config.registries.filter(registry => registry.provider && (registry.provider.has.mappings || registry.provider.has.occurrences) && (registry.scheme == null || this.$jskos.compare(this.selected.scheme[true], registry.scheme) || this.$jskos.compare(this.selected.scheme[false], registry.scheme)))
+      let registries = this.config.registries.filter(registry =>
+        registry.provider &&
+        (registry.provider.has.mappings || registry.provider.has.occurrences) &&
+        (
+          (registry.provider.supportsScheme && registry.provider.supportsScheme(this.selected.scheme[true])) ||
+          (registry.provider.supportsScheme && registry.provider.supportsScheme(this.selected.scheme[false]))
+        )
+      )
       let currentRegistryIndex = registries.findIndex(registry => this.$jskos.compare(registry, this.currentRegistry))
       if (currentRegistryIndex !== -1) {
         let current = registries[currentRegistryIndex]

src/providers/base-provider.js

@@ -586,6 +586,25 @@ class BaseProvider {
     }).then(this.adjustMappings)
   }
 
+  /**
+   * Returns a boolean whether a certain target scheme is supported or not.
+   *
+   * @param {object} scheme
+   */
+  supportsScheme(scheme) {
+    if (!scheme) {
+      return false
+    }
+    if (this.registry.scheme == null && !jskos.isContainedIn(scheme, this.registry.excludedSchemes || [])) {
+      return true
+    }
+    let schemes = _.isArray(this.registry.scheme) ? this.registry.scheme : [this.registry.scheme]
+    if (jskos.isContainedIn(scheme, schemes)) {
+      return true
+    }
+    return false
+  }
+
 }
 
 BaseProvider.providerName = "Base"