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use matching::Matcher;
use regex::Error;
use std::cmp::{Eq, Ord, Ordering, PartialEq, PartialOrd};
use std::collections::{BTreeSet, VecDeque};
use util::{Expression, Flags};
use std::fmt;
/// A compiled collection of rules ready for the building of a
/// `pidgin::Matcher` or for use in the definition of a new rule.
///
/// You do not build new `Grammar`s directly. Rather, the `compile` or `grammar`
/// method of a `Pidgin` produces them for you.
#[derive(Clone, Debug)]
pub struct Grammar {
pub(crate) name: Option<String>,
pub(crate) sequence: Vec<Expression>,
pub(crate) flags: Flags,
}
impl Grammar {
/// Compiles a `Matcher` based on the `Grammar`'s rules.
///
/// # Errors
///
/// If the `Grammar` contains a "foreign rule" with a named capture, an
/// error may be returned.
pub fn matcher(&self) -> Result<Matcher, Error> {
Matcher::new(&self)
}
/// Produces a quasi-BNF representation of the grammar.
///
/// This is how `pidging::Grammar` implements `std::fmt::Display`, so a
/// grammar's description is what you get if you feed it to the `{}` pattern.
///
/// # Examples
///
/// ```rust
/// # use pidgin::Pidgin;
/// let mut p = Pidgin::new();
/// let g = p.grammar(&vec!["bar", "baz"]);
/// p.rule("foo", &g);
/// p = p.case_insensitive(true);
/// let g = p.grammar(&vec!["ping", "pang", "pong"]);
/// p = p.case_insensitive(false);
/// p.rule("xyzzy", &g);
/// let g = p.grammar(&vec!["xyzzy", "qux"]);
/// p.rule("plugh", &g);
/// let g = p.grammar(&vec!["foo", "plugh"]);
/// println!("{}", g.describe());
/// // TOP := {foo}|{plugh}
/// // foo := ba[rz]
/// // plugh := qux|{xyzzy}
/// // xyzzy := (?i) p[aio]ng
/// println!("{}", g);
/// // TOP := {foo}|{plugh}
/// // foo := ba[rz]
/// // plugh := qux|{xyzzy}
/// // xyzzy := (?i) p[aio]ng
/// ```
pub fn describe(&self) -> String {
let g = self.describable_grammar();
let mut flags = g.flags(&Flags::defaults());
if flags.len() > 0 {
flags = format!("(?{})", flags);
}
let mut rules = vec![(String::from("TOP"), flags, g._describe())];
let mut seen: BTreeSet<String> = BTreeSet::new();
let mut queue = VecDeque::new();
for r in self.rules() {
let og = g.find(&r).unwrap().describable_grammar();
queue.push_back((r, og));
}
loop {
if let Some((r, g)) = queue.pop_front() {
if !seen.contains(&r) {
let mut flags = g.flags(&Flags::defaults());
if flags.len() > 0 {
flags = format!("(?{})", flags);
}
rules.push((r.clone(), flags, g._describe()));
seen.insert(r);
for r in g.rules() {
let og = g.find(&r).unwrap().describable_grammar();
queue.push_back((r, og));
}
}
} else {
break;
}
}
let mut max = 3;
let mut flag_max = 0;
for (ref n, flags, _) in &rules {
let l = n.len();
if l > max {
max = l;
}
let l = flags.len();
if l > flag_max {
flag_max = l;
}
}
if flag_max > 0 {
flag_max += 1;
}
let mut s = String::new();
for (n, f, d) in rules {
s =
s + &format!(
"{: >width$} := {: <flag_width$}{}",
n,
f,
d,
width = max,
flag_width = flag_max
) + "\n";
}
s
}
fn describable_grammar(&self) -> Grammar {
let mut g = self.clone();
g.name = None;
g.flags.enclosed = false;
g
}
fn _describe(&self) -> String {
self.sequence
.iter()
.map(|e| e.to_s(&self.flags, true, true))
.collect::<Vec<_>>()
.join("")
}
fn rules(&self) -> Vec<String> {
let mut rules = Vec::new();
let mut expressions = VecDeque::new();
for e in &self.sequence {
expressions.push_back(e);
}
loop {
if let Some(e) = expressions.pop_front() {
match e {
Expression::Grammar(ref g, _) => {
if let Some(ref n) = g.name {
rules.push(n.to_string());
}
}
Expression::Alternation(v, _) | Expression::Sequence(v, _) => {
for e in v {
expressions.push_back(e);
}
}
Expression::Repetition(e, _, _) => expressions.push_back(e),
_ => (),
}
} else {
break;
}
}
rules
}
fn find(&self, name: &str) -> Option<Grammar> {
let mut expressions = VecDeque::new();
for e in &self.sequence {
expressions.push_back(e);
}
loop {
if let Some(e) = expressions.pop_front() {
match e {
Expression::Grammar(ref g, _) => {
if let Some(ref n) = g.name {
if n == name {
let mut g = g.clone();
g.name = None;
return Some(g);
}
}
}
Expression::Alternation(v, _) | Expression::Sequence(v, _) => {
for e in v {
expressions.push_back(e);
}
}
Expression::Repetition(e, _, _) => expressions.push_back(e),
_ => (),
}
} else {
break;
}
}
None
}
/// Returns a quasi-regex representation of the grammar. This is intended
/// mostly for debugging. Rules will be identifiable by named groups, but
/// group names may repeat, in which case the stringification cannot be
/// compiled into a regular expression.
pub fn to_string(&self) -> String {
self.to_s(&Flags::defaults(), false, false)
}
pub(crate) fn clear_recursive(&self) -> Grammar {
let sequence = self.sequence.iter().map(|e| e.clear_names()).collect();
Grammar {
sequence,
name: None,
flags: self.flags.clone(),
}
}
pub(crate) fn clear_name(&mut self) {
self.name = None;
}
fn needs_closure(&self, context: &Flags) -> bool {
self.flags.enclosed || self.needs_flags_set(context)
}
fn needs_flags_set(&self, context: &Flags) -> bool {
self.flags.case_insensitive ^ context.case_insensitive
|| self.flags.dot_all ^ context.dot_all
|| self.flags.multi_line ^ context.multi_line
|| self.flags.unicode ^ context.unicode
|| self.flags.reverse_greed ^ context.reverse_greed
}
// flag string when needed
fn flags(&self, context: &Flags) -> String {
if !self.needs_flags_set(context) {
return String::from("");
}
let mut flags_on = Vec::with_capacity(4);
let mut flags_off = Vec::with_capacity(4);
if self.flags.case_insensitive ^ context.case_insensitive {
if self.flags.case_insensitive {
flags_on.push("i");
} else if self.flags.enclosed {
flags_off.push("i");
}
}
if self.flags.multi_line ^ context.multi_line {
if self.flags.multi_line {
flags_on.push("m");
} else if self.flags.enclosed {
flags_off.push("m");
}
}
if self.flags.dot_all ^ context.dot_all {
if self.flags.dot_all {
flags_on.push("s");
} else if self.flags.enclosed {
flags_off.push("s");
}
}
if self.flags.unicode ^ context.unicode {
if !self.flags.unicode {
flags_off.push("u");
} else if self.flags.enclosed {
flags_on.push("u");
}
}
if self.flags.reverse_greed ^ context.reverse_greed {
if !self.flags.reverse_greed {
flags_off.push("U");
} else if self.flags.reverse_greed {
flags_on.push("U");
}
}
let mut flags = String::new();
if flags_on.len() > 0 {
flags.push_str(&flags_on.join(""));
}
if flags_off.len() > 0 {
flags.push('-');
flags.push_str(&flags_off.join(""));
}
flags
}
pub(crate) fn to_s(&self, context: &Flags, describing: bool, top: bool) -> String {
let mut s = if self.name.is_some() {
format!("(?P<{}>", self.name.as_ref().unwrap())
} else {
String::new()
};
if !top && self.needs_closure(context) {
s = s + format!("(?{}:", self.flags(context)).as_str();
}
for e in &self.sequence {
s += e.to_s(&self.flags, describing, top).as_ref();
}
if !top && self.needs_closure(context) {
s = s + ")"
}
if self.name.is_some() {
s = s + ")"
}
s
}
}
impl PartialOrd for Grammar {
fn partial_cmp(&self, other: &Grammar) -> Option<Ordering> {
Some(self.cmp(other))
}
}
impl Ord for Grammar {
fn cmp(&self, other: &Grammar) -> Ordering {
let o = self.sequence.len().cmp(&other.sequence.len());
if o != Ordering::Equal {
return o;
}
if self.name.is_some() ^ other.name.is_some() {
return if self.name.is_some() {
Ordering::Greater
} else {
Ordering::Less
};
}
if self.name.is_some() {
let o = self
.name
.as_ref()
.unwrap()
.cmp(&other.name.as_ref().unwrap());
if o != Ordering::Equal {
return o;
}
}
for i in 0..self.sequence.len() {
let v1 = &self.sequence[i];
let v2 = &other.sequence[i];
let o = v1.cmp(&v2);
if o != Ordering::Equal {
return o;
}
}
self.flags.cmp(&other.flags)
}
}
impl PartialEq for Grammar {
fn eq(&self, other: &Grammar) -> bool {
self.cmp(other) == Ordering::Equal
}
}
impl Eq for Grammar {}
impl fmt::Display for Grammar {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
write!(f, "{}", self.describe())
}
}