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// This file is part of ICU4X. For terms of use, please see the file
// called LICENSE at the top level of the ICU4X source tree
// (online at: https://github.com/unicode-org/icu4x/blob/main/LICENSE ).
//! Code for the [`MultiNamedPlaceholder`] pattern backend.
#[cfg(feature = "alloc")]
use alloc::{borrow::Cow, boxed::Box, collections::BTreeMap, str::FromStr, string::String};
use core::fmt;
#[cfg(feature = "litemap")]
use litemap::LiteMap;
use writeable::Writeable;
use crate::common::*;
use crate::Error;
/// A string wrapper for the [`MultiNamedPlaceholder`] pattern backend.
///
/// # Examples
///
/// ```
/// use core::cmp::Ordering;
/// use core::str::FromStr;
/// use icu_pattern::MultiNamedPlaceholderKey;
/// use icu_pattern::MultiNamedPlaceholderPattern;
/// use icu_pattern::PatternItem;
///
/// // Parse the string syntax and check the resulting data store:
/// let pattern = MultiNamedPlaceholderPattern::try_from_str(
/// "Hello, {person0} and {person1}!", Default::default()
/// )
/// .unwrap();
///
/// assert_eq!(
/// pattern.iter().cmp(
/// [
/// PatternItem::Literal("Hello, "),
/// PatternItem::Placeholder(MultiNamedPlaceholderKey(
/// "person0".into()
/// )),
/// PatternItem::Literal(" and "),
/// PatternItem::Placeholder(MultiNamedPlaceholderKey(
/// "person1".into()
/// )),
/// PatternItem::Literal("!")
/// ]
/// .into_iter()
/// ),
/// Ordering::Equal
/// );
/// ```
#[derive(Debug, Clone, PartialEq, Eq, PartialOrd, Ord)]
#[repr(transparent)]
#[allow(clippy::exhaustive_structs)] // transparent newtype
pub struct MultiNamedPlaceholderKey<'a>(pub &'a str);
/// Cowable version of [`MultiNamedPlaceholderKey`], used during construction.
#[derive(Debug, Clone, PartialEq, Eq, PartialOrd, Ord)]
#[cfg_attr(feature = "serde", derive(serde::Deserialize, serde::Serialize))]
#[repr(transparent)]
#[allow(clippy::exhaustive_structs)] // transparent newtype
#[cfg(feature = "alloc")]
pub struct MultiNamedPlaceholderKeyCow<'a>(pub Cow<'a, str>);
#[cfg(feature = "alloc")]
impl FromStr for MultiNamedPlaceholderKeyCow<'_> {
type Err = Error;
fn from_str(s: &str) -> Result<Self, Self::Err> {
// Can't borrow the str here unfortunately
Ok(MultiNamedPlaceholderKeyCow(Cow::Owned(String::from(s))))
}
}
#[derive(Debug, Clone, PartialEq, Eq)]
#[non_exhaustive]
pub struct MissingNamedPlaceholderError<'a> {
pub name: &'a str,
}
impl Writeable for MissingNamedPlaceholderError<'_> {
fn write_to<W: fmt::Write + ?Sized>(&self, sink: &mut W) -> fmt::Result {
sink.write_char('{')?;
sink.write_str(self.name)?;
sink.write_char('}')?;
Ok(())
}
}
#[cfg(feature = "alloc")]
impl<'k, K, W> PlaceholderValueProvider<MultiNamedPlaceholderKey<'k>> for BTreeMap<K, W>
where
K: Ord + core::borrow::Borrow<str>,
W: Writeable,
{
type Error = MissingNamedPlaceholderError<'k>;
type W<'a>
= Result<&'a W, Self::Error>
where
W: 'a,
Self: 'a;
const LITERAL_PART: writeable::Part = crate::PATTERN_LITERAL_PART;
#[inline]
fn value_for<'a>(
&'a self,
key: MultiNamedPlaceholderKey<'k>,
) -> (Self::W<'a>, writeable::Part) {
let writeable = match self.get(key.0) {
Some(value) => Ok(value),
None => Err(MissingNamedPlaceholderError { name: key.0 }),
};
(writeable, crate::PATTERN_PLACEHOLDER_PART)
}
}
#[cfg(feature = "litemap")]
impl<'k, K, W, S> PlaceholderValueProvider<MultiNamedPlaceholderKey<'k>> for LiteMap<K, W, S>
where
K: Ord + core::borrow::Borrow<str>,
W: Writeable,
S: litemap::store::Store<K, W>,
{
type Error = MissingNamedPlaceholderError<'k>;
type W<'a>
= Result<&'a W, Self::Error>
where
W: 'a,
Self: 'a;
const LITERAL_PART: writeable::Part = crate::PATTERN_LITERAL_PART;
#[inline]
fn value_for<'a>(
&'a self,
key: MultiNamedPlaceholderKey<'k>,
) -> (Self::W<'a>, writeable::Part) {
let writeable = match self.get(key.0) {
Some(value) => Ok(value),
None => Err(MissingNamedPlaceholderError { name: key.0 }),
};
(writeable, crate::PATTERN_PLACEHOLDER_PART)
}
}
/// Backend for patterns containing zero or more named placeholders.
///
/// This empty type is not constructible.
///
/// # Placeholder Keys
///
/// The placeholder is [`MultiNamedPlaceholderKey`].
///
/// In [`Pattern::interpolate()`], pass a map-like structure. Missing keys will be replaced
/// with the Unicode replacement character U+FFFD.
///
/// # Encoding Details
///
/// The literals and placeholders are stored in context. A placeholder is encoded as a name length
/// in octal code points followed by the placeholder name.
///
/// For example, consider the pattern: "Hello, {user} and {someone_else}!"
///
/// The encoding for this would be:
///
/// ```txt
/// Hello, \x00\x04user and \x01\x04someone_else!
/// ```
///
/// where `\x00\x04` and `\x01\x04` are a big-endian octal number representing the lengths of
/// their respective placeholder names.
///
/// Consequences of this encoding:
///
/// 1. The maximum placeholder name length is 64 bytes
/// 2. Code points in the range `\x00` through `\x07` are reserved for the placeholder name
///
/// # Examples
///
/// Example patterns supported by this backend:
///
/// ```
/// use core::str::FromStr;
/// use icu_pattern::MultiNamedPlaceholder;
/// use icu_pattern::Pattern;
/// use std::collections::BTreeMap;
///
/// let placeholder_value_map: BTreeMap<&str, &str> = [
/// ("num", "5"),
/// ("letter", "X"),
/// ("", "empty"),
/// ("unused", "unused"),
/// ]
/// .into_iter()
/// .collect();
///
/// // Single placeholder:
/// assert_eq!(
/// Pattern::<MultiNamedPlaceholder>::try_from_str("{num} days ago", Default::default())
/// .unwrap()
/// .try_interpolate_to_string(&placeholder_value_map)
/// .unwrap(),
/// "5 days ago",
/// );
///
/// // No placeholder (note, the placeholder value is never accessed):
/// assert_eq!(
/// Pattern::<MultiNamedPlaceholder>::try_from_str("yesterday", Default::default())
/// .unwrap()
/// .try_interpolate_to_string(&placeholder_value_map)
/// .unwrap(),
/// "yesterday",
/// );
///
/// // No literals, only placeholders:
/// assert_eq!(
/// Pattern::<MultiNamedPlaceholder>::try_from_str("{letter}{num}{}", Default::default())
/// .unwrap()
/// .try_interpolate_to_string(&placeholder_value_map)
/// .unwrap(),
/// "X5empty",
/// );
/// ```
///
/// Use [`LiteMap`] for alloc-free formatting:
///
/// ```
/// use core::str::FromStr;
/// use icu_pattern::MultiNamedPlaceholderPattern;
/// use litemap::LiteMap;
/// use writeable::TryWriteable;
///
/// static placeholder_value_map: LiteMap<&str, usize, &[(&str, usize)]> =
/// LiteMap::from_sorted_store_unchecked(&[("seven", 11)]);
///
/// // Note: String allocates, but this could be a non-allocating sink
/// let mut sink = String::new();
///
/// MultiNamedPlaceholderPattern::try_from_str("{seven}", Default::default())
/// .unwrap()
/// .try_interpolate(&placeholder_value_map)
/// .try_write_to(&mut sink)
/// .unwrap()
/// .unwrap();
///
/// assert_eq!(sink, "11");
/// ```
///
/// Missing placeholder values cause an error result to be returned. However,
/// based on the design of [`TryWriteable`], the error can be discarded to get
/// a best-effort interpolation with potential replacement characters.
///
/// ```should_panic
/// use core::str::FromStr;
/// use icu_pattern::MultiNamedPlaceholder;
/// use icu_pattern::Pattern;
/// use std::collections::BTreeMap;
///
/// let placeholder_value_map: BTreeMap<&str, &str> =
/// [("num", "5"), ("letter", "X")].into_iter().collect();
///
/// Pattern::<MultiNamedPlaceholder>::try_from_str("Your name is {your_name}", Default::default())
/// .unwrap()
/// .try_interpolate_to_string(&placeholder_value_map)
/// .unwrap();
/// ```
///
/// Recover the best-effort lossy string by directly using [`Pattern::try_interpolate()`]:
///
/// ```
/// use core::str::FromStr;
/// use icu_pattern::MissingNamedPlaceholderError;
/// use icu_pattern::MultiNamedPlaceholder;
/// use icu_pattern::Pattern;
/// use std::borrow::Cow;
/// use std::collections::BTreeMap;
/// use writeable::TryWriteable;
///
/// let placeholder_value_map: BTreeMap<&str, &str> =
/// [("num", "5"), ("letter", "X")].into_iter().collect();
///
/// let pattern = Pattern::<MultiNamedPlaceholder>::try_from_str(
/// "Your name is {your_name}", Default::default(),
/// )
/// .unwrap();
///
/// let mut buffer = String::new();
/// let result = pattern
/// .try_interpolate(&placeholder_value_map)
/// .try_write_to(&mut buffer)
/// .expect("infallible write to String");
///
/// assert!(matches!(result, Err(MissingNamedPlaceholderError { .. })));
/// assert_eq!(result.unwrap_err().name, "your_name");
/// assert_eq!(buffer, "Your name is {your_name}");
/// ```
///
/// [`Pattern::interpolate()`]: crate::Pattern::interpolate
/// [`Pattern::try_interpolate()`]: crate::Pattern::try_interpolate
/// [`TryWriteable`]: writeable::TryWriteable
#[derive(Debug, Copy, Clone, PartialEq, Eq)]
#[allow(clippy::exhaustive_enums)] // Empty Enum
pub enum MultiNamedPlaceholder {}
impl crate::private::Sealed for MultiNamedPlaceholder {}
impl PatternBackend for MultiNamedPlaceholder {
type PlaceholderKey<'a> = MultiNamedPlaceholderKey<'a>;
#[cfg(feature = "alloc")]
type PlaceholderKeyCow<'a> = MultiNamedPlaceholderKeyCow<'a>;
type Error<'a> = MissingNamedPlaceholderError<'a>;
type Store = str;
type Iter<'a> = MultiNamedPlaceholderPatternIterator<'a>;
fn validate_store(store: &Self::Store) -> Result<(), Error> {
let mut iter = MultiNamedPlaceholderPatternIterator::new(store);
while iter
.try_next()
.map_err(|e| match e {
MultiNamedPlaceholderError::InvalidStore => Error::InvalidPattern,
MultiNamedPlaceholderError::Unreachable => {
debug_assert!(false, "unreachable");
Error::InvalidPattern
}
})?
.is_some()
{}
Ok(())
}
fn iter_items(store: &Self::Store) -> Self::Iter<'_> {
MultiNamedPlaceholderPatternIterator::new(store)
}
#[cfg(feature = "alloc")]
fn try_from_items<
'cow,
'ph,
I: Iterator<Item = Result<PatternItemCow<'cow, Self::PlaceholderKeyCow<'ph>>, Error>>,
>(
items: I,
) -> Result<Box<str>, Error> {
let mut string = String::new();
for item in items {
match item? {
PatternItemCow::Literal(s) if s.contains(|x| (x as usize) <= 0x07) => {
// TODO: Should this be a different error type?
return Err(Error::InvalidPattern);
}
PatternItemCow::Literal(s) => string.push_str(&s),
PatternItemCow::Placeholder(ph_key) => {
let name_length = ph_key.0.len();
if name_length >= 64 {
return Err(Error::InvalidPlaceholder);
}
let lead = (name_length >> 3) as u8;
let trail = (name_length & 0x7) as u8;
string.push(char::from(lead));
string.push(char::from(trail));
string.push_str(&ph_key.0);
}
}
}
Ok(string.into_boxed_str())
}
fn empty() -> &'static Self::Store {
""
}
}
#[derive(Debug)]
pub struct MultiNamedPlaceholderPatternIterator<'a> {
store: &'a str,
}
// Note: we don't implement ExactSizeIterator since we don't store that metadata in MultiNamed.
impl<'a> Iterator for MultiNamedPlaceholderPatternIterator<'a> {
type Item = PatternItem<'a, MultiNamedPlaceholderKey<'a>>;
fn next(&mut self) -> Option<Self::Item> {
match self.try_next() {
Ok(next) => next,
Err(MultiNamedPlaceholderError::InvalidStore) => {
debug_assert!(
false,
"invalid store with {} bytes remaining",
self.store.len()
);
None
}
Err(MultiNamedPlaceholderError::Unreachable) => {
debug_assert!(false, "unreachable");
None
}
}
}
}
enum MultiNamedPlaceholderError {
InvalidStore,
Unreachable,
}
impl<'a> MultiNamedPlaceholderPatternIterator<'a> {
fn new(store: &'a str) -> Self {
Self { store }
}
fn try_next(
&mut self,
) -> Result<Option<PatternItem<'a, MultiNamedPlaceholderKey<'a>>>, MultiNamedPlaceholderError>
{
match self.store.find(|x| (x as usize) <= 0x07) {
Some(0) => {
// Placeholder
let Some(&[lead, trail]) = self.store.as_bytes().get(0..2) else {
return Err(MultiNamedPlaceholderError::InvalidStore);
};
debug_assert!(lead <= 7);
if trail > 7 {
return Err(MultiNamedPlaceholderError::InvalidStore);
}
let placeholder_len = (lead << 3) + trail;
let boundary = (placeholder_len as usize) + 2;
// TODO: use .split_at_checked() when available:
// https://github.com/rust-lang/rust/issues/119128
let Some(placeholder_name) = self.store.get(2..boundary) else {
return Err(MultiNamedPlaceholderError::InvalidStore);
};
let Some(remainder) = self.store.get(boundary..) else {
debug_assert!(false, "should be a perfect slice");
return Err(MultiNamedPlaceholderError::Unreachable);
};
self.store = remainder;
Ok(Some(PatternItem::Placeholder(MultiNamedPlaceholderKey(
placeholder_name,
))))
}
Some(i) => {
// Literal
// TODO: use .split_at_checked() when available:
// https://github.com/rust-lang/rust/issues/119128
let Some(literal) = self.store.get(..i) else {
debug_assert!(false, "should be a perfect slice");
return Err(MultiNamedPlaceholderError::Unreachable);
};
let Some(remainder) = self.store.get(i..) else {
debug_assert!(false, "should be a perfect slice");
return Err(MultiNamedPlaceholderError::Unreachable);
};
self.store = remainder;
Ok(Some(PatternItem::Literal(literal)))
}
None if self.store.is_empty() => {
// End of string
Ok(None)
}
None => {
// Closing literal
let literal = self.store;
self.store = "";
Ok(Some(PatternItem::Literal(literal)))
}
}
}
}
#[cfg(test)]
mod tests {
use super::*;
use crate::{MultiNamedPlaceholder, MultiNamedPlaceholderPattern};
#[test]
fn test_invalid() {
let long_str = "0123456789".repeat(1000000);
let strings = [
"{", // invalid syntax
"{@}", // placeholder name too long
"\x00", // invalid character
"\x07", // invalid character
];
for string in strings {
let string = string.replace('@', &long_str);
assert!(
MultiNamedPlaceholderPattern::try_from_str(&string, Default::default()).is_err(),
"{string:?}"
);
}
let stores = [
"\x00", // too short
"\x02", // too short
"\x00\x02", // no placeholder name
"\x00\x02a", // placeholder name too short
];
for store in stores {
assert!(
MultiNamedPlaceholder::validate_store(store).is_err(),
"{store:?}"
);
}
}
}