<?xml version="1.0" encoding="UTF-8"?>
<grammar xmlns="http://relaxng.org/ns/structure/1.0">
  <!--
       interface_definition.rnc: VyConf reference tree XML grammar
    
       Copyright (C) 2014. 2017 VyOS maintainers and contributors <maintainers@vyos.net>
    
       This library is free software; you can redistribute it and/or
       modify it under the terms of the GNU Lesser General Public
       License as published by the Free Software Foundation; either
       version 2.1 of the License, or (at your option) any later version.
    
       This library is distributed in the hope that it will be useful,
       but WITHOUT ANY WARRANTY; without even the implied warranty of
       MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
       Lesser General Public License for more details.
    
       You should have received a copy of the GNU Lesser General Public
       License along with this library; if not, write to the Free Software
       Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301
       USA
  -->
  <!--
    The language of this file is compact form RELAX-NG
    http://relaxng.org/compact-tutorial-20030326.htm
    (unless converted to XML, then just RELAX-NG :)
  -->
  <!-- Interface definition starts with interfaceDefinition tag that may contain node tags -->
  <start>
    <element name="interfaceDefinition">
      <zeroOrMore>
        <ref name="node"/>
      </zeroOrMore>
    </element>
  </start>
  <!--
    node tag may contain node, leafNode, or tagNode tags
    Those are intermediate configuration nodes that may only contain
    other nodes and must not have values
  -->
  <define name="node">
    <element name="node">
      <interleave>
        <optional>
          <ref name="ownerAttr"/>
        </optional>
        <ref name="nodeNameAttr"/>
      </interleave>
      <interleave>
        <optional>
          <ref name="properties"/>
        </optional>
        <optional>
          <ref name="children"/>
        </optional>
      </interleave>
    </element>
  </define>
  <!--
    Tag nodes are containers for nodes without predefined names, like network interfaces
    or user names (e.g. "interfaces ethernet eth0" or "user jrandomhacker")
    Tag nodes may contain node and leafNode elements, and also nameConstraint tags
    They must not contain other tag nodes
  -->
  <define name="tagNode">
    <element name="tagNode">
      <interleave>
        <optional>
          <ref name="ownerAttr"/>
        </optional>
        <ref name="nodeNameAttr"/>
      </interleave>
      <interleave>
        <optional>
          <ref name="properties"/>
        </optional>
        <ref name="children"/>
      </interleave>
    </element>
  </define>
  <!--
    Leaf nodes are terminal configuration nodes that can't have children,
    but can have values.
    Leaf node may contain one or more valueConstraint tags
    If multiple valueConstraint tags are used, they work a logical OR
    Leaf nodes can have "multi" attribute that indicated that it can have
    more than one value
  -->
  <define name="leafNode">
    <element name="leafNode">
      <interleave>
        <optional>
          <ref name="ownerAttr"/>
        </optional>
        <ref name="nodeNameAttr"/>
      </interleave>
      <ref name="properties"/>
    </element>
  </define>
  <!-- Normal and tag nodes may have children -->
  <define name="children">
    <element name="children">
      <oneOrMore>
        <choice>
          <ref name="node"/>
          <ref name="tagNode"/>
          <ref name="leafNode"/>
        </choice>
      </oneOrMore>
    </element>
  </define>
  <!--
    Nodes may have properties
    For simplicity, any property is allowed in any node,
    but whether they are used or not is implementation-defined
    
    Leaf nodes may differ in number of values that can be
    associated with them.
    By default, a leaf node can have only one value.
    "multi" tag means a node can have one or more values,
    "valueless" means it can have no values at all.
    "hidden" means node visibility can be toggled, eg 'dangerous' commands,
    "secret" allows a node to hide its value from unprivileged users.
    
    "priority" is used to influence node processing order for nodes
    with exact same dependencies and in compatibility modes.
  -->
  <define name="properties">
    <element name="properties">
      <interleave>
        <optional>
          <ref name="help"/>
        </optional>
        <optional>
          <ref name="constraint"/>
        </optional>
        <zeroOrMore>
          <ref name="valueHelp"/>
        </zeroOrMore>
        <optional>
          <element name="constraintErrorMessage">
            <text/>
          </element>
        </optional>
        <zeroOrMore>
          <ref name="completionHelp"/>
        </zeroOrMore>
        <optional>
          <!-- These are meaningful only for leaf nodes -->
          <group>
            <element name="valueless">
              <empty/>
            </element>
          </group>
        </optional>
        <optional>
          <element name="multi">
            <empty/>
          </element>
        </optional>
        <optional>
          <element name="hidden">
            <empty/>
          </element>
        </optional>
        <optional>
          <element name="secret">
            <empty/>
          </element>
        </optional>
        <optional>
          <element name="priority">
            <text/>
          </element>
        </optional>
        <optional>
          <!-- These are meaningful only for tag nodes -->
          <group>
            <element name="keepChildOrder">
              <empty/>
            </element>
          </group>
        </optional>
      </interleave>
    </element>
  </define>
  <!-- All nodes must have "name" attribute -->
  <define name="nodeNameAttr">
    <attribute name="name"/>
  </define>
  <!--
    Ordinary nodes and tag nodes can have "owner" attribute.
    Owner is the component that is notified when node changes.
  -->
  <define name="ownerAttr">
    <attribute name="owner"/>
  </define>
  <!--
    Tag and leaf nodes may have constraints on their names and values
    (respectively).
    When multiple constraints are listed, they work as logical OR
  -->
  <define name="constraint">
    <element name="constraint">
      <oneOrMore>
        <choice>
          <element name="regex">
            <text/>
          </element>
          <ref name="validator"/>
        </choice>
      </oneOrMore>
    </element>
  </define>
  <!-- A constraint may also use an external validator rather than regex -->
  <define name="validator">
    <element name="validator">
      <interleave>
        <attribute name="name"/>
        <optional>
          <attribute name="argument"/>
        </optional>
      </interleave>
      <empty/>
    </element>
  </define>
  <!-- help tags contains brief description of the purpose of the node -->
  <define name="help">
    <element name="help">
      <text/>
    </element>
  </define>
  <!-- valueHelp tags contain information about acceptable value format -->
  <define name="valueHelp">
    <element name="valueHelp">
      <interleave>
        <element name="format">
          <text/>
        </element>
        <element name="description">
          <text/>
        </element>
      </interleave>
    </element>
  </define>
  <!--
    completionHelp tags contain information about allowed values of a node that is used for generating
    tab completion in the CLI frontend and drop-down lists in GUI frontends
    It is only meaninful for leaf nodes
    Allowed values can be given as a fixed list of values (e.g. <list>foo bar baz</list>),
    as a configuration path (e.g. <path>interfaces ethernet</path>),
    or as a path to a script file that generates the list (e.g. <script>/usr/lib/foo/list-things</script>
  -->
  <define name="completionHelp">
    <element name="completionHelp">
      <interleave>
        <zeroOrMore>
          <element name="list">
            <text/>
          </element>
        </zeroOrMore>
        <zeroOrMore>
          <element name="path">
            <text/>
          </element>
        </zeroOrMore>
        <zeroOrMore>
          <element name="script">
            <text/>
          </element>
        </zeroOrMore>
      </interleave>
    </element>
  </define>
</grammar>