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#![warn(clippy::all)]
#![warn(clippy::pedantic)]
#![warn(clippy::cargo)]
#![warn(missing_copy_implementations)]
#![warn(missing_debug_implementations)]
#![warn(trivial_casts, trivial_numeric_casts)]
#![warn(unused_qualifications)]
#![warn(variant_size_differences)]
#![forbid(unsafe_code)]
#![warn(unused_import_braces)]
#![warn(unused_results)]
#![warn(unused_lifetimes)]
#![warn(unused)]
#![warn(missing_docs)]
#![allow(clippy::multiple_crate_versions)]
#![doc = include_str!("../README.md")]
use std::{collections::BTreeSet, error::Error, fmt::Display};
use bitflags::bitflags;
use log::trace;
use unicode_titlecase::StrTitleCase;
/// Error cases for the [`Result`] of [`decompound`].
#[derive(Debug, Clone, PartialEq, Eq, PartialOrd, Ord)]
pub enum DecompositionError {
/// Result was *not* a compound word, but a valid *single* word. Whether this is a
/// hard error is subjective: in any case, *decomposition failed*, but the word is
/// returned to the caller for further processing.
SingleWord(String),
/// Nothing valid was found (neither a compound word nor a single, non-compound
/// word).
NothingValid, // Kind of like `Option::None`, but incompatible;
// use obviously different name so it's not confused.
}
impl Display for DecompositionError {
fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
match self {
DecompositionError::SingleWord(word) => {
write!(f, "Not a compound, but valid single word: {word}")
}
DecompositionError::NothingValid => write!(f, "No valid decomposition found"),
}
}
}
impl Error for DecompositionError {}
bitflags! {
/// Options for [`decompound`], configuring its search. Available options are found
/// below, as `pub const`s.
///
/// Use [`DecompositionOptions::empty()`] to set *no* options. See the [`bitflags`
/// docs](https://docs.rs/bitflags/latest/bitflags/#working-with-flags-values) for
/// more.
#[derive(Clone)]
pub struct DecompositionOptions: u32 {
/// In *addition* to the original suffix being tried, try its titlecased version
/// as well. Does nothing if suffix is already titlecased.
///
/// This option is mostly relevant for languages with meaningful capitalization.
///
/// ```
/// use decompound::{decompound, DecompositionError, DecompositionOptions};
///
/// let is_valid_single_word = |w: &str| ["Haus", "Boot"].contains(&w);
///
/// let word = "Hausboot";
///
/// // Without this option
/// assert_eq!(
/// decompound(
/// word,
/// &is_valid_single_word,
/// DecompositionOptions::empty(),
/// ).unwrap_err(),
/// DecompositionError::NothingValid
/// );
///
/// // With this option
/// assert_eq!(
/// decompound(
/// word,
/// &is_valid_single_word,
/// DecompositionOptions::TRY_TITLECASE_SUFFIX,
/// ).unwrap(),
/// vec!["Haus", "Boot"]
/// );
/// ```
const TRY_TITLECASE_SUFFIX = 1;
/// Treat hyphenated words as compound words. Its constituents will be returned
/// as a collection of *all* constituents of the hyphenated word, *without* any
/// hyphens:
///
/// ```
/// use decompound::{decompound, DecompositionError, DecompositionOptions};
///
/// let is_valid_single_word = |w: &str| [
/// "room",
/// "bed",
/// "super",
/// "hero",
/// "in",
/// "side",
/// ].contains(&w);
///
/// let word = "bedroom-superhero-inside";
///
/// // Without this option
/// assert_eq!(
/// decompound(
/// word,
/// &is_valid_single_word,
/// DecompositionOptions::empty(),
/// ).unwrap_err(),
/// DecompositionError::NothingValid
/// );
///
/// // With this option
/// assert_eq!(
/// decompound(
/// word,
/// &is_valid_single_word,
/// DecompositionOptions::SPLIT_HYPHENATED,
/// ).unwrap(),
/// vec!["bed", "room", "super", "hero", "in", "side"]
/// );
/// ```
///
/// Any error in any of the found subwords will cause the entire operation to
/// fail:
///
/// ```
/// use decompound::{decompound, DecompositionError, DecompositionOptions};
///
/// let is_valid_single_word = |w: &str| ["room", "bed"].contains(&w);
///
/// assert_eq!(
/// decompound(
/// "bedroom-error", // 'error' is not a valid word here
/// &is_valid_single_word,
/// DecompositionOptions::SPLIT_HYPHENATED,
/// ).unwrap_err(),
/// DecompositionError::NothingValid // Not even `vec!["bed", "room"]`
/// );
/// ```
const SPLIT_HYPHENATED = 1 << 1;
/// Split into as many constituents as possible. Otherwise, by default, the
/// decomposition with the fewest elements is returned, as that is likeliest to
/// be most desirable. If your use case disagrees, use this option.
///
/// # Example: Word is both a valid single and compound word
///
/// ```
/// use decompound::{decompound, DecompositionError, DecompositionOptions};
///
/// let is_valid_single_word = |w: &str| [
/// // These are regular, valid words,
/// // virtually guaranteed to be in any dictionary:
/// "Entnahme", // "withdrawal"
/// "Stelle", // "spot"
/// "Elle", // "ell"
/// // Not a word in the regular sense, but a plausible occurrence in
/// // dictionaries as an abbreviation for `Sankt` (Saint),
/// // as in `St. Petersburg`. A party pooper in this case...
/// "St",
/// ].contains(&w);
///
/// let word = "Entnahmestelle";
///
/// // Without this option
/// assert_eq!(
/// decompound(
/// word,
/// &is_valid_single_word,
/// // Option not relevant to example but required for valid German
/// // handling:
/// DecompositionOptions::TRY_TITLECASE_SUFFIX,
/// ).unwrap(),
/// vec!["Entnahme", "Stelle"]
/// );
///
/// // With this option
/// assert_eq!(
/// decompound(
/// word,
/// &is_valid_single_word,
/// DecompositionOptions::TRY_TITLECASE_SUFFIX
/// | DecompositionOptions::SHATTER,
/// ).unwrap(),
/// // This is *not* the desired outcome for this term,
/// // but it's what this option does:
/// vec!["Entnahme", "St", "Elle"]
/// );
/// ```
///
/// # Example: Greedy prefix matching
///
/// ```
/// use decompound::{decompound, DecompositionError, DecompositionOptions};
///
/// let is_valid_single_word = |w: &str| [
/// "Empfänger",
/// "Empfängers", // genetive might be part of dictionary...
/// "Station",
/// "tat",
/// "Ion",
/// ].contains(&w);
///
/// let word = "Empfängerstation";
///
/// // Without this option
/// assert_eq!(
/// decompound(
/// word,
/// &is_valid_single_word,
/// // Option not relevant to example but required for valid German
/// // handling:
/// DecompositionOptions::TRY_TITLECASE_SUFFIX,
/// ).unwrap(),
/// vec!["Empfänger", "Station"]
/// );
///
/// // With this option
/// assert_eq!(
/// decompound(
/// word,
/// &is_valid_single_word,
/// DecompositionOptions::TRY_TITLECASE_SUFFIX
/// | DecompositionOptions::SHATTER,
/// ).unwrap(),
/// // This is *not* the desired outcome for this term,
/// // but it's what this option does:
/// vec!["Empfängers", "tat", "Ion"]
/// );
/// ```
const SHATTER = 1 << 2;
}
}
impl AsRef<DecompositionOptions> for DecompositionOptions {
fn as_ref(&self) -> &Self {
self
}
}
/// [`Result`] of a [`decompound`] operation.
///
/// Note constituent words are returned as owned, even if that's not (always) necessary.
/// It *is* necessary when titlecasing is enabled
/// ([`DecompositionOptions::TRY_TITLECASE_SUFFIX`]), at which point it's easier to
/// always return owned versions, even when unnecessary.
pub type DecompositionResult = Result<Vec<String>, DecompositionError>;
/// Refer to the [crate-level documentation](crate) for this item.
///
/// ## Errors
///
/// Errors are covered in the [crate-level documentation](crate#failure-modes).
pub fn decompound(
word: impl AsRef<str>,
is_valid_single_word: &impl Fn(&str) -> bool,
options: impl AsRef<DecompositionOptions>,
) -> DecompositionResult {
let mut constituents = vec![];
let word = word.as_ref();
let options = options.as_ref();
if options.contains(DecompositionOptions::SPLIT_HYPHENATED) {
// Avoid reentry on upcoming recursive call
let options = options.clone() - DecompositionOptions::SPLIT_HYPHENATED;
for subword in word.split('-') {
match decompound(subword, is_valid_single_word, &options) {
Ok(words) => constituents.extend(words),
// Actually allowed in this mode: words like 'string-concatenation' are
// valid, where each part is only a 'single' word, not again a compound
// word in itself.
Err(DecompositionError::SingleWord(word)) => constituents.push(word),
_ => return Err(DecompositionError::NothingValid),
};
}
return match &constituents[..] {
[] => Err(DecompositionError::NothingValid),
[w] => Err(DecompositionError::SingleWord(w.into())),
_ => Ok(constituents),
};
}
if is_valid_compound_word(word, is_valid_single_word, options, &mut constituents) {
debug_assert!(
!constituents.is_empty(),
"Compound word must have constituents"
);
Ok(constituents)
} else {
trace!("Word is not a valid compound word");
if is_valid_single_word(word) {
Err(DecompositionError::SingleWord(word.to_owned()))
} else {
Err(DecompositionError::NothingValid)
}
}
}
fn is_valid_compound_word(
word: impl AsRef<str>,
is_valid_single_word: &impl Fn(&str) -> bool,
options: &DecompositionOptions,
constituents: &mut Vec<String>,
) -> bool {
let word = word.as_ref();
trace!("Checking if word is valid compound word: '{}'", word);
let mut all_valid_splits = Vec::new();
for (i, _) in word.char_indices().skip(1) {
// Try *all* prefixes, not just the first or longest valid one; they all might
// have valid suffixes. Which one to return is decided later.
let (prefix, suffix) = word.split_at(i);
debug_assert!(!prefix.is_empty(), "Prefix should never be empty");
debug_assert!(!suffix.is_empty(), "Suffix should never be empty");
if !is_valid_single_word(prefix) {
continue;
}
trace!(
"Prefix '{}' found to be valid, seeing if suffix '{}' is valid.",
prefix,
suffix
);
let suffix_candidates = {
// Dedupe so no unnecessary work is done, but keep order for determinism
let mut set = BTreeSet::from_iter(vec![suffix.to_owned()]);
if options.contains(DecompositionOptions::TRY_TITLECASE_SUFFIX) {
let _ = set.insert(suffix.to_titlecase_lower_rest());
}
set
};
debug_assert!(
!suffix_candidates.is_empty(),
"Suffix candidates should never be empty"
);
for suffix in suffix_candidates {
// EACH of these checks (for readability, organized into blocks) might be
// true, so we do not break early, and clone copiously (could be done more
// efficiently at substantially higher complexity).
//
// A word might be *both* a valid single *and* compound word, but which
// version is kept depends on `SHATTER`ing.
{
if is_valid_single_word(&suffix) {
trace!("Suffix '{}' is valid: valid single word", suffix);
all_valid_splits.push(vec![prefix.to_owned(), suffix.clone()]);
}
}
{
let mut further_constituents = Vec::new();
if is_valid_compound_word(
&suffix,
is_valid_single_word,
options,
&mut further_constituents,
) {
trace!("Suffix '{}' is valid: valid compound word", suffix);
let mut valid_split = vec![prefix.to_owned()];
valid_split.extend(further_constituents);
all_valid_splits.push(valid_split);
}
}
}
}
match if options.contains(DecompositionOptions::SHATTER) {
all_valid_splits.iter().max_by_key(|s| s.len())
} else {
all_valid_splits.iter().min_by_key(|s| s.len())
} {
Some(split) => {
constituents.extend(split.iter().cloned());
true
}
None => false,
}
}