1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
// 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 ).

//! Titlecasing-specific try_new_with_mapper_unstable
use crate::provider::CaseMapV1Marker;
use crate::CaseMapper;
use alloc::string::String;
use icu_locid::LanguageIdentifier;
use icu_properties::maps::CodePointMapData;
use icu_properties::provider::GeneralCategoryV1Marker;
use icu_properties::{GeneralCategory, GeneralCategoryGroup, PropertiesError};
use icu_provider::prelude::*;
use writeable::Writeable;

/// How to handle the rest of the string once the beginning of the
/// string has been titlecased.
///
/// # Examples
///
/// ```rust
/// use icu::casemap::titlecase::{TitlecaseOptions, TrailingCase};
/// use icu::casemap::TitlecaseMapper;
/// use icu::locid::langid;
///
/// let cm = TitlecaseMapper::new();
/// let root = langid!("und");
///
/// let default_options = Default::default();
/// let mut preserve_case: TitlecaseOptions = Default::default();
/// preserve_case.trailing_case = TrailingCase::Unchanged;
///
/// // Exhibits trailing case when set:
/// assert_eq!(
///     cm.titlecase_segment_to_string("spOngeBoB", &root, default_options),
///     "Spongebob"
/// );
/// assert_eq!(
///     cm.titlecase_segment_to_string("spOngeBoB", &root, preserve_case),
///     "SpOngeBoB"
/// );
/// ```
#[non_exhaustive]
#[derive(Copy, Clone, Default, PartialEq, Eq, Hash, Debug)]
pub enum TrailingCase {
    /// Preserve the casing of the rest of the string ("spoNgEBoB" -> "SpoNgEBoB")
    Unchanged,
    /// Lowercase the rest of the string ("spoNgEBoB" -> "Spongebob")
    #[default]
    Lower,
}

/// Where to start casing the string.
///
/// [`TitlecaseMapper`] by default performs "leading adjustment", where it searches for the first "relevant" character
/// in the string before initializing the actual titlecasing. For example, it will skip punctuation at the beginning
/// of a string, allowing for strings like `'twas` or `«hello»` to be appropriately titlecased.
///
/// Opinions on exactly what is a "relevant" character may differ. In "adjust to cased" mode the first cased character is considered "relevant",
/// whereas in the "auto" mode, it is the first character that is a letter, number, symbol, or private use character. This means
/// that the strings `49ers` and `«丰(abc)»` will titlecase in "adjust to cased" mode to `49Ers` and `«丰(Abc)»`, whereas in the "auto" mode they stay unchanged.
/// This difference largely matters for things that mix numbers and letters, or mix writing systems, within a single segment.
///
/// # Examples
///
/// ```rust
/// use icu::casemap::titlecase::{LeadingAdjustment, TitlecaseOptions};
/// use icu::casemap::TitlecaseMapper;
/// use icu::locid::langid;
///
/// let cm = TitlecaseMapper::new();
/// let root = langid!("und");
///
/// let default_options = Default::default(); // head adjustment set to Auto
/// let mut no_adjust: TitlecaseOptions = Default::default();
/// let mut adjust_to_cased: TitlecaseOptions = Default::default();
/// no_adjust.leading_adjustment = LeadingAdjustment::None;
/// adjust_to_cased.leading_adjustment = LeadingAdjustment::ToCased;
///
/// // Exhibits leading adjustment when set:
/// assert_eq!(
///     cm.titlecase_segment_to_string("«hello»", &root, default_options),
///     "«Hello»"
/// );
/// assert_eq!(
///     cm.titlecase_segment_to_string("«hello»", &root, adjust_to_cased),
///     "«Hello»"
/// );
/// assert_eq!(
///     cm.titlecase_segment_to_string("«hello»", &root, no_adjust),
///     "«hello»"
/// );
///
/// // Only changed in adjust-to-cased mode:
/// assert_eq!(
///     cm.titlecase_segment_to_string("丰(abc)", &root, default_options),
///     "丰(abc)"
/// );
/// assert_eq!(
///     cm.titlecase_segment_to_string("丰(abc)", &root, adjust_to_cased),
///     "丰(Abc)"
/// );
/// assert_eq!(
///     cm.titlecase_segment_to_string("丰(abc)", &root, no_adjust),
///     "丰(abc)"
/// );
///
/// // Only changed in adjust-to-cased mode:
/// assert_eq!(
///     cm.titlecase_segment_to_string("49ers", &root, default_options),
///     "49ers"
/// );
/// assert_eq!(
///     cm.titlecase_segment_to_string("49ers", &root, adjust_to_cased),
///     "49Ers"
/// );
/// assert_eq!(
///     cm.titlecase_segment_to_string("49ers", &root, no_adjust),
///     "49ers"
/// );
/// ```
#[non_exhaustive]
#[derive(Copy, Clone, Default, PartialEq, Eq, Hash, Debug)]
pub enum LeadingAdjustment {
    /// Start titlecasing immediately, even if the character is not one that is relevant for casing
    /// ("'twixt" -> "'twixt", "twixt" -> "Twixt")
    None,
    /// Adjust the string to the first relevant character before beginning to apply casing
    /// ("'twixt" -> "'Twixt"). "Relevant" character is picked by best available algorithm,
    /// by default will adjust to first letter, number, symbol, or private use character,
    /// but if no data is available (e.g. this API is being called via [`CaseMapper::titlecase_segment_with_only_case_data()`]),
    /// then may be equivalent to "adjust to cased".
    ///
    /// This is the default
    #[default]
    Auto,
    /// Adjust the string to the first cased character before beginning to apply casing
    /// ("'twixt" -> "'Twixt")
    ToCased,
}

/// Various options for controlling titlecasing
///
/// See docs of [`TitlecaseMapper`] for examples.
#[non_exhaustive]
#[derive(Copy, Clone, Default, PartialEq, Eq, Hash, Debug)]
pub struct TitlecaseOptions {
    /// How to handle the rest of the string once the head of the
    /// string has been titlecased
    pub trailing_case: TrailingCase,
    /// Whether to start casing at the beginning of the string or at the first
    /// relevant character.
    pub leading_adjustment: LeadingAdjustment,
}

/// A wrapper around [`CaseMapper`] that can compute titlecasing stuff, and is able to load additional data
/// to support the non-legacy "head adjustment" behavior.
///
///
/// By default, [`Self::titlecase_segment()`] and [`Self::titlecase_segment_to_string()`] perform "leading adjustment",
/// where they wait till the first relevant character to begin titlecasing. For example, in the string `'twixt`, the apostrophe
/// is ignored because the word starts at the first "t", which will get titlecased (producing `'Twixt`). Other punctuation will
/// also be ignored, like in the string `«hello»`, which will get titlecased to `«Hello»`.
///
/// This is a separate type from [`CaseMapper`] because it loads the additional data
/// required by [`LeadingAdjustment::Auto`] to perform the best possible leading adjustment.
///
/// If you are planning on only using [`LeadingAdjustment::None`] or [`LeadingAdjustment::ToCased`], consider using [`CaseMapper`] directly; this
/// type will have no additional behavior.
///
/// # Examples
///
/// Basic casemapping behavior:
///
/// ```rust
/// use icu::casemap::TitlecaseMapper;
/// use icu::locid::langid;
///
/// let cm = TitlecaseMapper::new();
/// let root = langid!("und");
///
/// let default_options = Default::default();
///
/// // note that the subsequent words are not titlecased, this function assumes
/// // that the entire string is a single segment and only titlecases at the beginning.
/// assert_eq!(cm.titlecase_segment_to_string("hEllO WorLd", &root, default_options), "Hello world");
/// assert_eq!(cm.titlecase_segment_to_string("Γειά σου Κόσμε", &root, default_options), "Γειά σου κόσμε");
/// assert_eq!(cm.titlecase_segment_to_string("नमस्ते दुनिया", &root, default_options), "नमस्ते दुनिया");
/// assert_eq!(cm.titlecase_segment_to_string("Привет мир", &root, default_options), "Привет мир");
///
/// // Some behavior is language-sensitive
/// assert_eq!(cm.titlecase_segment_to_string("istanbul", &root, default_options), "Istanbul");
/// assert_eq!(cm.titlecase_segment_to_string("istanbul", &langid!("tr"), default_options), "İstanbul"); // Turkish dotted i
///
/// assert_eq!(cm.titlecase_segment_to_string("և Երևանի", &root, default_options), "Եւ երևանի");
/// assert_eq!(cm.titlecase_segment_to_string("և Երևանի", &langid!("hy"), default_options), "Եվ երևանի"); // Eastern Armenian ech-yiwn ligature
///
/// assert_eq!(cm.titlecase_segment_to_string("ijkdijk", &root, default_options), "Ijkdijk");
/// assert_eq!(cm.titlecase_segment_to_string("ijkdijk", &langid!("nl"), default_options), "IJkdijk"); // Dutch IJ digraph
/// ```
#[derive(Clone, Debug)]
pub struct TitlecaseMapper<CM> {
    cm: CM,
    gc: CodePointMapData<GeneralCategory>,
}

#[cfg(feature = "compiled_data")]
impl Default for TitlecaseMapper<CaseMapper> {
    fn default() -> Self {
        Self::new()
    }
}

impl TitlecaseMapper<CaseMapper> {
    /// A constructor which creates a [`TitlecaseMapper`] using compiled data
    ///
    /// ✨ *Enabled with the `compiled_data` Cargo feature.*
    ///
    /// [📚 Help choosing a constructor](icu_provider::constructors)
    #[cfg(feature = "compiled_data")]
    pub const fn new() -> Self {
        Self {
            cm: CaseMapper::new(),
            gc: icu_properties::maps::general_category().static_to_owned(),
        }
    }

    icu_provider::gen_any_buffer_data_constructors!(locale: skip, options: skip, error: DataError,
    #[cfg(skip)]
    functions: [
        new,
        try_new_with_any_provider,
        try_new_with_buffer_provider,
        try_new_unstable,
        Self,
    ]);

    #[doc = icu_provider::gen_any_buffer_unstable_docs!(UNSTABLE, Self::new)]
    pub fn try_new_unstable<P>(provider: &P) -> Result<Self, DataError>
    where
        P: DataProvider<CaseMapV1Marker> + DataProvider<GeneralCategoryV1Marker> + ?Sized,
    {
        let cm = CaseMapper::try_new_unstable(provider)?;
        let gc = icu_properties::maps::load_general_category(provider).map_err(|e| {
            let PropertiesError::PropDataLoad(e) = e else {
                unreachable!()
            };
            e
        })?;
        Ok(Self { cm, gc })
    }
}

// We use Borrow, not AsRef, since we want the blanket impl on T
impl<CM: AsRef<CaseMapper>> TitlecaseMapper<CM> {
    icu_provider::gen_any_buffer_data_constructors!(locale: skip, casemapper: CM, error: DataError,
    #[cfg(skip)]
    functions: [
        new_with_mapper,
        try_new_with_mapper_with_any_provider,
        try_new_with_mapper_with_buffer_provider,
        try_new_with_mapper_unstable,
        Self,
    ]);

    /// A constructor which creates a [`TitlecaseMapper`] from an existing [`CaseMapper`]
    /// (either owned or as a reference) and compiled data
    ///
    /// ✨ *Enabled with the `compiled_data` Cargo feature.*
    ///
    /// [📚 Help choosing a constructor](icu_provider::constructors)
    #[cfg(feature = "compiled_data")]
    pub const fn new_with_mapper(casemapper: CM) -> Self {
        Self {
            cm: casemapper,
            gc: icu_properties::maps::general_category().static_to_owned(),
        }
    }

    /// Construct this object to wrap an existing CaseMapper (or a reference to one), loading additional data as needed.
    #[doc = icu_provider::gen_any_buffer_unstable_docs!(UNSTABLE, Self::new_with_mapper)]
    pub fn try_new_with_mapper_unstable<P>(provider: &P, casemapper: CM) -> Result<Self, DataError>
    where
        P: DataProvider<CaseMapV1Marker> + DataProvider<GeneralCategoryV1Marker> + ?Sized,
    {
        let gc = icu_properties::maps::load_general_category(provider).map_err(|e| {
            let PropertiesError::PropDataLoad(e) = e else {
                unreachable!()
            };
            e
        })?;
        Ok(Self { cm: casemapper, gc })
    }

    /// Returns the full titlecase mapping of the given string as a [`Writeable`], treating
    /// the string as a single segment (and thus only titlecasing the beginning of it).
    ///
    /// This should typically be used as a lower-level helper to construct the titlecasing operation desired
    /// by the application, for example one can titlecase on a per-word basis by mixing this with
    /// a `WordSegmenter`.
    ///
    /// This function is context and language sensitive. Callers should pass the text's language
    /// as a `LanguageIdentifier` (usually the `id` field of the `Locale`) if available, or
    /// `Default::default()` for the root locale.
    ///
    /// See [`Self::titlecase_segment_to_string()`] for the equivalent convenience function that returns a String,
    /// as well as for an example.
    pub fn titlecase_segment<'a>(
        &'a self,
        src: &'a str,
        langid: &LanguageIdentifier,
        options: TitlecaseOptions,
    ) -> impl Writeable + 'a {
        if options.leading_adjustment == LeadingAdjustment::Auto {
            // letter, number, symbol, or private use code point
            const HEAD_GROUPS: GeneralCategoryGroup = GeneralCategoryGroup::Letter
                .union(GeneralCategoryGroup::Number)
                .union(GeneralCategoryGroup::Symbol)
                .union(GeneralCategoryGroup::PrivateUse);
            self.cm
                .as_ref()
                .titlecase_segment_with_adjustment(src, langid, options, |_data, ch| {
                    HEAD_GROUPS.contains(self.gc.as_borrowed().get(ch))
                })
        } else {
            self.cm
                .as_ref()
                .titlecase_segment_with_adjustment(src, langid, options, |data, ch| {
                    data.is_cased(ch)
                })
        }
    }

    /// Returns the full titlecase mapping of the given string as a String, treating
    /// the string as a single segment (and thus only titlecasing the beginning of it).
    ///
    /// This should typically be used as a lower-level helper to construct the titlecasing operation desired
    /// by the application, for example one can titlecase on a per-word basis by mixing this with
    /// a `WordSegmenter`.
    ///
    /// This function is context and language sensitive. Callers should pass the text's language
    /// as a `LanguageIdentifier` (usually the `id` field of the `Locale`) if available, or
    /// `Default::default()` for the root locale.
    ///
    /// See [`Self::titlecase_segment()`] for the equivalent lower-level function that returns a [`Writeable`]
    ///
    /// # Examples
    ///
    /// ```rust
    /// use icu::casemap::TitlecaseMapper;
    /// use icu::locid::langid;
    ///
    /// let cm = TitlecaseMapper::new();
    /// let root = langid!("und");
    ///
    /// let default_options = Default::default();
    ///
    /// // note that the subsequent words are not titlecased, this function assumes
    /// // that the entire string is a single segment and only titlecases at the beginning.
    /// assert_eq!(cm.titlecase_segment_to_string("hEllO WorLd", &root, default_options), "Hello world");
    /// assert_eq!(cm.titlecase_segment_to_string("Γειά σου Κόσμε", &root, default_options), "Γειά σου κόσμε");
    /// assert_eq!(cm.titlecase_segment_to_string("नमस्ते दुनिया", &root, default_options), "नमस्ते दुनिया");
    /// assert_eq!(cm.titlecase_segment_to_string("Привет мир", &root, default_options), "Привет мир");
    ///
    /// // Some behavior is language-sensitive
    /// assert_eq!(cm.titlecase_segment_to_string("istanbul", &root, default_options), "Istanbul");
    /// assert_eq!(cm.titlecase_segment_to_string("istanbul", &langid!("tr"), default_options), "İstanbul"); // Turkish dotted i
    ///
    /// assert_eq!(cm.titlecase_segment_to_string("և Երևանի", &root, default_options), "Եւ երևանի");
    /// assert_eq!(cm.titlecase_segment_to_string("և Երևանի", &langid!("hy"), default_options), "Եվ երևանի"); // Eastern Armenian ech-yiwn ligature
    ///
    /// assert_eq!(cm.titlecase_segment_to_string("ijkdijk", &root, default_options), "Ijkdijk");
    /// assert_eq!(cm.titlecase_segment_to_string("ijkdijk", &langid!("nl"), default_options), "IJkdijk"); // Dutch IJ digraph
    /// ```
    ///
    /// Leading adjustment behaviors:
    ///
    /// ```rust
    /// use icu::casemap::titlecase::{LeadingAdjustment, TitlecaseOptions};
    /// use icu::casemap::TitlecaseMapper;
    /// use icu::locid::langid;
    ///
    /// let cm = TitlecaseMapper::new();
    /// let root = langid!("und");
    ///
    /// let default_options = Default::default();
    /// let mut no_adjust: TitlecaseOptions = Default::default();
    /// no_adjust.leading_adjustment = LeadingAdjustment::None;
    ///
    /// // Exhibits leading adjustment when set:
    /// assert_eq!(
    ///     cm.titlecase_segment_to_string("«hello»", &root, default_options),
    ///     "«Hello»"
    /// );
    /// assert_eq!(
    ///     cm.titlecase_segment_to_string("«hello»", &root, no_adjust),
    ///     "«hello»"
    /// );
    ///
    /// assert_eq!(
    ///     cm.titlecase_segment_to_string("'Twas", &root, default_options),
    ///     "'Twas"
    /// );
    /// assert_eq!(
    ///     cm.titlecase_segment_to_string("'Twas", &root, no_adjust),
    ///     "'twas"
    /// );
    ///
    /// assert_eq!(
    ///     cm.titlecase_segment_to_string("", &root, default_options),
    ///     ""
    /// );
    /// assert_eq!(cm.titlecase_segment_to_string("", &root, no_adjust), "");
    /// ```
    ///
    /// Tail casing behaviors:
    ///
    /// ```rust
    /// use icu::casemap::titlecase::{TitlecaseOptions, TrailingCase};
    /// use icu::casemap::TitlecaseMapper;
    /// use icu::locid::langid;
    ///
    /// let cm = TitlecaseMapper::new();
    /// let root = langid!("und");
    ///
    /// let default_options = Default::default();
    /// let mut preserve_case: TitlecaseOptions = Default::default();
    /// preserve_case.trailing_case = TrailingCase::Unchanged;
    ///
    /// // Exhibits trailing case when set:
    /// assert_eq!(
    ///     cm.titlecase_segment_to_string("spOngeBoB", &root, default_options),
    ///     "Spongebob"
    /// );
    /// assert_eq!(
    ///     cm.titlecase_segment_to_string("spOngeBoB", &root, preserve_case),
    ///     "SpOngeBoB"
    /// );
    /// ```
    pub fn titlecase_segment_to_string(
        &self,
        src: &str,
        langid: &LanguageIdentifier,
        options: TitlecaseOptions,
    ) -> String {
        self.titlecase_segment(src, langid, options)
            .write_to_string()
            .into_owned()
    }
}