#    interface_definition.rnc: VyConf reference tree XML grammar
#
#    Copyright VyOS maintainers and contributors <maintainers@vyos.io>
#
#    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 interfaceDefinition
{
    (node | tagNode)*
}

# 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
node = element node
{
    nodeNameAttr,
    (properties? & children? & command?)
}

# Tag nodes are containers for nodes without predefined names, like network interfaces
# or user names (e.g. "show interfaces ethernet ethX").
# Operational mode tag nodes can be parents to other tag nodes,
# like in "ping <host> count <packets>".
#
# Some commands can be called either with or without arguments,
# like "show interfaces ethernet eth0" (show info for eth0 only)
# or "show interfaces ethernet" (show info about all ethernet interfaces).
# That case is handled using the <standalone> element
tagNode = element tagNode
{
    nodeNameAttr,
    (properties? & standalone? & children? & command?)
}

# The <standalone> element is only used inside tag nodes
# to define their behavior when they are called without arguments
# It can provide a help string and a command.
# Everything else is handled in the <tagNode> itself.
standalone = element standalone
{
    help & command
}

# Virtual tag nodes provide a way to add a variable argument
# to a command that also needs fixed arguments,
# like "show ip route" that can take "show ip route bgp"
# or a network and arguments after it, like "show ip route 10.0.0.0/8 longer-prefixes"
virtualTagNode = element virtualTagNode
{
    (properties? & children? & command?)
}

# Leaf nodes are terminal configuration nodes that can't have children,
# but can have values.

leafNode = element leafNode
{
    nodeNameAttr,
    (command & properties)
}

# Normal and tag nodes may have children: nodes, leaf nodes, or tag nodes.
# There can only be one virtual tag node child, though.
children = element children
{
    (virtualTagNode? & (node | tagNode | leafNode)*) |
    (node | tagNode | leafNode)+
}

# Nodes may have properties
# For simplicity, any property is allowed in any node,
# but whether they are used or not is implementation-defined
properties = element properties
{
    help? &
    completionHelp* &
    constraint? &
    (element constraintErrorMessage { text })?
}

# All nodes must have "name" attribute
nodeNameAttr = attribute name
{
    text
}

# Tag and leaf nodes may have constraints on their names and values
# (respectively).
# When multiple constraints are listed, they work as logical OR
constraint = element constraint
{
    ( (element regex { text }) |
      validator )+
}

# A constraint may also use an external validator rather than regex
validator = element validator
{
    ( (attribute name { text })  &
      (attribute argument { text })? ),
    empty
}

# help tags contains brief description of the purpose of the node
help = element help
{
    text
}

command = element command
{
    text
}

# 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 meaningful 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>),
# as a path to a script file that generates the list (e.g. <script>/usr/lib/foo/list-things</script>,
# or to enable built-in image path completion (<imagePath/>).
completionHelp = element completionHelp
{
    (element list { text })* &
    (element path { text })* &
    (element script { text })* &
    (element imagePath { empty })?
}