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use range::Range;
use std::rc::Rc;
use std::cell::RefCell;
use {
Whitespace,
Token,
UntilAnyOrWhitespace,
Text,
Number,
Node,
NodeRef,
NodeVisit,
MetaReader,
ParseError,
ParseResult,
Select,
SeparatedBy,
Sequence,
Optional,
};
/// A rule describes how some section of a document should be parsed.
pub enum Rule {
/// Read whitespace.
Whitespace(Whitespace),
/// Match against a token.
Token(Token),
/// Read until any or whitespace.
UntilAnyOrWhitespace(UntilAnyOrWhitespace),
/// Read text.
Text(Text),
/// Read number.
Number(Number),
/// Select one of the sub rules.
/// If the first one does not succeed, try another and so on.
/// If all sub rules fail, then the rule fails.
Select(Select),
/// Run each sub rule in sequence.
/// If any sub rule fails, the rule fails.
Sequence(Sequence),
/// Repeat rule separated by another rule.
SeparatedBy(Box<SeparatedBy>),
/// Read node.
Node(NodeRef),
/// Read optional.
Optional(Optional),
}
impl Rule {
/// Parses rule.
pub fn parse<M>(
&self,
meta_reader: &mut M,
state: &M::State,
chars: &[char],
offset: usize
) -> ParseResult<M::State>
where M: MetaReader
{
match self {
&Rule::Whitespace(ref w) => {
w.parse(chars, offset).map(|r| (r, state.clone(), None))
}
&Rule::Token(ref t) => {
t.parse(meta_reader, state, chars, offset)
}
&Rule::UntilAnyOrWhitespace(ref u) => {
u.parse(meta_reader, state, chars, offset)
}
&Rule::Text(ref t) => {
t.parse(meta_reader, state, chars, offset)
}
&Rule::Number(ref n) => {
n.parse(meta_reader, state, chars, offset)
}
&Rule::Select(ref s) => {
s.parse(meta_reader, state, chars, offset)
}
&Rule::Sequence(ref s) => {
s.parse(meta_reader, state, chars, offset)
}
&Rule::SeparatedBy(ref s) => {
s.parse(meta_reader, state, chars, offset)
}
&Rule::Node(ref p) => {
match p {
&NodeRef::Name(_, debug_id) => {
Err((
Range::empty(offset),
ParseError::InvalidRule(
"Node rule is not updated to reference", debug_id)
))
}
&NodeRef::Ref(ref p, _) => {
p.borrow().parse(meta_reader, state, chars, offset)
}
}
}
&Rule::Optional(ref o) => {
Ok(o.parse(meta_reader, state, chars, offset))
}
}
}
/// Updates replacing names with the references.
///
/// The references contains the name,
/// but this can not be borrowed as when the same reference is updated.
pub fn update_refs(&mut self, refs: &[(Rc<String>, Rc<RefCell<Node>>)]) {
match self {
&mut Rule::Node(ref mut p) => {
*p = {
match p {
&mut NodeRef::Name(ref name, _) => {
// Look through references and update if correct name
// is found.
let mut found: Option<Rc<RefCell<Node>>> = None;
for r in refs {
if &**name == &*r.0 {
found = Some(r.1.clone());
}
}
match found {
None => { return; }
Some(r) =>
NodeRef::Ref(r, NodeVisit::Unvisited)
}
}
&mut NodeRef::Ref(ref mut p, ref mut visited) => {
// Update the sub rules of the reference,
// but only if it has not been visited.
if let NodeVisit::Unvisited = *visited {
*visited = NodeVisit::Visited;
for sub_rule in &mut p.borrow_mut().body {
sub_rule.update_refs(refs);
}
return;
} else {
return;
}
}
}
}
}
&mut Rule::Whitespace(_) => {}
&mut Rule::Token(_) => {}
&mut Rule::UntilAnyOrWhitespace(_) => {}
&mut Rule::Text(_) => {}
&mut Rule::Number(_) => {}
&mut Rule::Select(ref mut s) => {
for sub_rule in &mut s.args {
sub_rule.update_refs(refs);
}
}
&mut Rule::Sequence(ref mut s) => {
for sub_rule in &mut s.args {
sub_rule.update_refs(refs);
}
}
&mut Rule::SeparatedBy(ref mut s) => {
s.rule.update_refs(refs);
s.by.update_refs(refs);
}
&mut Rule::Optional(ref mut o) => {
for sub_rule in &mut o.args {
sub_rule.update_refs(refs);
}
}
}
}
}