/// <summary>Find or create a schema node if <c>createNodes</c> is true.</summary>
/// <param name="tree">the root of the xmp tree.</param>
/// <param name="namespaceUri">a namespace</param>
/// <param name="suggestedPrefix">If a prefix is suggested, the namespace is allowed to be registered.</param>
/// <param name="createNodes">
/// a flag indicating if the node shall be created if not found.
/// <em>Note:</em> The namespace must be registered prior to this call.
/// </param>
/// <returns>
/// Returns the schema node if found, <c>null</c> otherwise.
/// Note: If <c>createNodes</c> is <c>true</c>, it is <b>always</b>
/// returned a valid node.
/// </returns>
/// <exception cref="XmpException">
/// An exception is only thrown if an error occurred, not if a
/// node was not found.
/// </exception>
internal static XmpNode FindSchemaNode(XmpNode tree, string namespaceUri, string suggestedPrefix, bool createNodes)
{
Debug.Assert(tree.Parent == null);
// make sure that its the root
var schemaNode = tree.FindChildByName(namespaceUri);
if (schemaNode == null && createNodes)
{
var po = new PropertyOptions {
IsSchemaNode = true
};
schemaNode = new XmpNode(namespaceUri, po)
{
IsImplicit = true
};
// only previously registered schema namespaces are allowed in the XMP tree.
var prefix = XmpMetaFactory.SchemaRegistry.GetNamespacePrefix(namespaceUri);
if (prefix == null)
{
if (!string.IsNullOrEmpty(suggestedPrefix))
{
prefix = XmpMetaFactory.SchemaRegistry.RegisterNamespace(namespaceUri, suggestedPrefix);
}
else
{
throw new XmpException("Unregistered schema namespace URI", XmpErrorCode.BadSchema);
}
}
schemaNode.Value = prefix;
tree.AddChild(schemaNode);
}
return(schemaNode);
}
/// <summary>Find or create a child node under a given parent node.</summary>
/// <remarks>
/// Find or create a child node under a given parent node. If the parent node is no
/// Returns the found or created child node.
/// </remarks>
/// <param name="parent">the parent node</param>
/// <param name="childName">the node name to find</param>
/// <param name="createNodes">flag, if new nodes shall be created.</param>
/// <returns>Returns the found or created node or <c>null</c>.</returns>
/// <exception cref="XmpException">Thrown if</exception>
internal static XmpNode FindChildNode(XmpNode parent, string childName, bool createNodes)
{
if (!parent.Options.IsSchemaNode && !parent.Options.IsStruct)
{
if (!parent.IsImplicit)
{
throw new XmpException("Named children only allowed for schemas and structs", XmpErrorCode.BadXPath);
}
if (parent.Options.IsArray)
{
throw new XmpException("Named children not allowed for arrays", XmpErrorCode.BadXPath);
}
if (createNodes)
{
parent.Options.IsStruct = true;
}
}
var childNode = parent.FindChildByName(childName);
if (childNode == null && createNodes)
{
var options = new PropertyOptions();
childNode = new XmpNode(childName, options)
{
IsImplicit = true
};
parent.AddChild(childNode);
}
Debug.Assert(childNode != null || !createNodes);
return(childNode);
}