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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 [`SinglePlaceholder`] pattern backend.
use core::convert::Infallible;
use core::{cmp::Ordering, str::FromStr};
use writeable::adapters::WriteableAsTryWriteableInfallible;
use writeable::Writeable;
use crate::common::*;
use crate::Error;
#[cfg(feature = "alloc")]
use alloc::{boxed::Box, string::String};
/// A singleton enum for the [`SinglePlaceholder`] pattern backend.
///
/// # Examples
///
/// ```
/// use core::cmp::Ordering;
/// use core::str::FromStr;
/// use icu_pattern::PatternItem;
/// use icu_pattern::SinglePlaceholder;
/// use icu_pattern::SinglePlaceholderKey;
/// use icu_pattern::SinglePlaceholderPattern;
///
/// // Parse the string syntax and check the resulting data store:
/// let pattern = SinglePlaceholderPattern::try_from_str(
/// "Hello, {0}!",
/// Default::default(),
/// )
/// .unwrap();
///
/// assert_eq!(
/// pattern.iter().cmp(
/// [
/// PatternItem::Literal("Hello, "),
/// PatternItem::Placeholder(SinglePlaceholderKey::Singleton),
/// PatternItem::Literal("!")
/// ]
/// .into_iter()
/// ),
/// Ordering::Equal
/// );
/// ```
#[derive(Debug, Copy, Clone, PartialEq, Eq, PartialOrd, Ord)]
#[cfg_attr(feature = "serde", derive(serde::Deserialize, serde::Serialize))]
#[allow(clippy::exhaustive_enums)] // Singleton
pub enum SinglePlaceholderKey {
Singleton,
}
impl FromStr for SinglePlaceholderKey {
type Err = core::convert::Infallible;
fn from_str(_: &str) -> Result<Self, Self::Err> {
Ok(Self::Singleton)
}
}
impl<W> PlaceholderValueProvider<SinglePlaceholderKey> for (W,)
where
W: Writeable,
{
type Error = Infallible;
type W<'a>
= WriteableAsTryWriteableInfallible<&'a W>
where
Self: 'a;
type L<'a, 'l>
= &'l str
where
Self: 'a;
fn value_for(&self, _key: SinglePlaceholderKey) -> Self::W<'_> {
WriteableAsTryWriteableInfallible(&self.0)
}
#[inline]
fn map_literal<'a, 'l>(&'a self, literal: &'l str) -> Self::L<'a, 'l> {
literal
}
}
impl<W> PlaceholderValueProvider<SinglePlaceholderKey> for [W; 1]
where
W: Writeable,
{
type Error = Infallible;
type W<'a>
= WriteableAsTryWriteableInfallible<&'a W>
where
Self: 'a;
type L<'a, 'l>
= &'l str
where
Self: 'a;
fn value_for(&self, _key: SinglePlaceholderKey) -> Self::W<'_> {
let [value] = self;
WriteableAsTryWriteableInfallible(value)
}
#[inline]
fn map_literal<'a, 'l>(&'a self, literal: &'l str) -> Self::L<'a, 'l> {
literal
}
}
/// Backend for patterns containing zero or one placeholder.
///
/// This empty type is not constructible.
///
/// # Placeholder Keys
///
/// The placeholder is always [`SinglePlaceholderKey::Singleton`].
///
/// In [`Pattern::interpolate()`], pass a single-element array or tuple.
///
/// # Encoding Details
///
/// The first code point of the string is 1 plus the byte offset of the placeholder counting from
/// after that initial code point. If zero, there is no placeholder.
///
/// # Examples
///
/// Parsing a pattern into the encoding:
///
/// ```
/// use core::str::FromStr;
/// use icu_pattern::Pattern;
/// use icu_pattern::SinglePlaceholder;
///
/// // Parse the string syntax and check the resulting data store:
/// let pattern = Pattern::<SinglePlaceholder>::try_from_str(
/// "Hello, {0}!",
/// Default::default(),
/// )
/// .unwrap();
///
/// assert_eq!("\u{8}Hello, !", &pattern.store);
/// ```
///
/// Example patterns supported by this backend:
///
/// ```
/// use core::str::FromStr;
/// use icu_pattern::Pattern;
/// use icu_pattern::QuoteMode;
/// use icu_pattern::SinglePlaceholder;
///
/// // Single numeric placeholder:
/// assert_eq!(
/// Pattern::<SinglePlaceholder>::try_from_str(
/// "{0} days ago",
/// Default::default()
/// )
/// .unwrap()
/// .interpolate_to_string([5]),
/// "5 days ago",
/// );
///
/// // Single named placeholder:
/// assert_eq!(
/// Pattern::<SinglePlaceholder>::try_from_str(
/// "{name}",
/// Default::default()
/// )
/// .unwrap()
/// .interpolate_to_string(["Alice"]),
/// "Alice",
/// );
///
/// // No placeholder (note, the placeholder value is never accessed):
/// assert_eq!(
/// Pattern::<SinglePlaceholder>::try_from_str(
/// "yesterday",
/// Default::default()
/// )
/// .unwrap()
/// .interpolate_to_string(["hi"]),
/// "yesterday",
/// );
///
/// // Escaped placeholder and a real placeholder:
/// assert_eq!(
/// Pattern::<SinglePlaceholder>::try_from_str(
/// "'{0}' {1}",
/// QuoteMode::QuotingSupported.into()
/// )
/// .unwrap()
/// .interpolate_to_string(("hi",)),
/// "{0} hi",
/// );
/// ```
///
/// [`Pattern::interpolate()`]: crate::Pattern::interpolate
#[derive(Debug, Copy, Clone, PartialEq, Eq)]
#[allow(clippy::exhaustive_enums)] // Empty Enum
pub enum SinglePlaceholder {}
impl crate::private::Sealed for SinglePlaceholder {}
impl PatternBackend for SinglePlaceholder {
type PlaceholderKey<'a> = SinglePlaceholderKey;
#[cfg(feature = "alloc")]
type PlaceholderKeyCow<'a> = SinglePlaceholderKey;
type Error<'a> = Infallible;
type Store = str;
type Iter<'a> = SinglePlaceholderPatternIterator<'a>;
fn validate_store(store: &Self::Store) -> Result<(), Error> {
let placeholder_offset_char = store.chars().next().ok_or(Error::InvalidPattern)?;
let initial_offset = placeholder_offset_char.len_utf8();
let placeholder_offset = placeholder_offset_char as usize;
if placeholder_offset > store.len() - initial_offset + 1 {
return Err(Error::InvalidPattern);
}
if placeholder_offset >= 0xD800 {
return Err(Error::InvalidPattern);
}
Ok(())
}
fn iter_items(store: &Self::Store) -> Self::Iter<'_> {
let placeholder_offset_char = match store.chars().next() {
Some(i) => i,
None => {
debug_assert!(false);
'\0'
}
};
let initial_offset = placeholder_offset_char.len_utf8();
SinglePlaceholderPatternIterator {
store,
placeholder_offset: placeholder_offset_char as usize + initial_offset - 1,
current_offset: initial_offset,
}
}
#[cfg(feature = "alloc")]
fn try_from_items<
'cow,
'ph,
I: Iterator<Item = Result<PatternItemCow<'cow, Self::PlaceholderKey<'ph>>, Error>>,
>(
items: I,
) -> Result<Box<str>, Error> {
let mut result = String::new();
let mut seen_placeholder = false;
for item in items {
match item? {
PatternItemCow::Literal(s) => result.push_str(&s),
PatternItemCow::Placeholder(_) if !seen_placeholder => {
seen_placeholder = true;
let placeholder_offset =
u32::try_from(result.len() + 1).map_err(|_| Error::InvalidPattern)?;
if placeholder_offset >= 0xD800 {
return Err(Error::InvalidPattern);
}
let placeholder_offset_char =
char::try_from(placeholder_offset).map_err(|_| Error::InvalidPattern)?;
result.insert(0, placeholder_offset_char);
}
PatternItemCow::Placeholder(_) => {
return Err(Error::InvalidPattern);
}
}
}
if !seen_placeholder {
result.insert(0, '\0');
}
Ok(result.into_boxed_str())
}
fn empty() -> &'static Self::Store {
"\0"
}
}
#[doc(hidden)] // TODO(#4467): Should be internal
#[derive(Debug)]
pub struct SinglePlaceholderPatternIterator<'a> {
store: &'a str,
placeholder_offset: usize,
current_offset: usize,
}
// Note: This impl is not exported via public bounds, but it might be in the
// future, and the compiler might be able to find it. The code is also
// reachable from `Iterator::size_hint`.
impl ExactSizeIterator for SinglePlaceholderPatternIterator<'_> {
fn len(&self) -> usize {
let placeholder_offset_char = match self.store.chars().next() {
Some(i) => i,
None => {
debug_assert!(false);
'\0'
}
};
let initial_offset = placeholder_offset_char.len_utf8();
let placeholder_offset = placeholder_offset_char as usize + initial_offset - 1;
let store_len = self.store.len();
if placeholder_offset < initial_offset {
// No placeholder
if initial_offset < store_len {
// No placeholder, non-empty literal
1
} else {
// No placeholder, empty literal
0
}
} else if placeholder_offset == initial_offset {
// Has placeholder, empty prefix
if initial_offset < store_len {
// Has placeholder, empty prefix, non-empty suffix
2
} else {
// Has placeholder, empty prefix, empty suffix
1
}
} else if placeholder_offset < store_len {
// Has placeholder, non-empty prefix, non-empty suffix
3
} else {
// Has placeholder, non-empty prefix, empty suffix
2
}
}
}
impl<'a> Iterator for SinglePlaceholderPatternIterator<'a> {
type Item = PatternItem<'a, SinglePlaceholderKey>;
fn next(&mut self) -> Option<Self::Item> {
match self.current_offset.cmp(&self.placeholder_offset) {
Ordering::Less => {
// Prefix
let literal_str = match self.store.get(self.current_offset..self.placeholder_offset)
{
Some(s) => s,
None => {
debug_assert!(false, "offsets are in range");
""
}
};
self.current_offset = self.placeholder_offset;
Some(PatternItem::Literal(literal_str))
}
Ordering::Equal => {
// Placeholder
self.placeholder_offset = 0;
Some(PatternItem::Placeholder(SinglePlaceholderKey::Singleton))
}
Ordering::Greater => {
// Suffix or end of string
let literal_str = match self.store.get(self.current_offset..) {
Some(s) => s,
None => {
debug_assert!(false, "offsets are in range");
""
}
};
if literal_str.is_empty() {
// End of string
None
} else {
// Suffix
self.current_offset = self.store.len();
Some(PatternItem::Literal(literal_str))
}
}
}
}
fn size_hint(&self) -> (usize, Option<usize>) {
let len = self.len();
(len, Some(len))
}
}
// TODO(#1668): Add more tests