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
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
// 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 ).

use crate::transliterate::provider::TransliteratorRulesV1Marker;

use alloc::collections::BTreeMap;
use alloc::format;
use alloc::string::{String, ToString};
use alloc::vec::Vec;
use core::cell::RefCell;
use icu_locale_core::Locale;
use icu_normalizer::provider::*;
use icu_properties::{
    props::{PatternWhiteSpace, XidContinue, XidStart},
    provider::*,
    CodePointSetData,
};
use icu_provider::prelude::*;

mod parse;
mod pass1;
mod pass2;
mod rule_group_agg;

/// The direction of a rule-based transliterator in respect to its source.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub(crate) enum Direction {
    /// Forwards, i.e., left-to-right in the source.
    Forward,
    /// Reverse, i.e., right-to-left in the source.
    Reverse,
    /// Both forwards and reverse.
    Both,
}

impl Direction {
    /// Whether `self` is a superset of `other` or not.
    pub(crate) fn permits(&self, other: Direction) -> bool {
        match self {
            Direction::Forward => other == Direction::Forward,
            Direction::Reverse => other == Direction::Reverse,
            Direction::Both => true,
        }
    }
}

#[derive(Debug, Default)]
/// A collection of transliteration rules.
///
/// ✨ *Enabled with the `compile` Cargo feature.*
///
/// # Example
/// ```
/// use icu::experimental::transliterate::{RuleCollection, Transliterator};
///
/// let mut collection = RuleCollection::default();
/// collection.register_source(
///     &"de-t-de-d0-ascii".parse().unwrap(),
///     r#"
///       $AE = [Ä {A \u0308}];
///       $OE = [Ö {O \u0308}];
///       $UE = [Ü {U \u0308}];
///  
///       [ä {a \u0308}] → ae;
///       [ö {o \u0308}] → oe;
///       [ü {u \u0308}] → ue;
///  
///       {$AE} [:Lowercase:] → Ae;
///       {$OE} [:Lowercase:] → Oe;
///       {$UE} [:Lowercase:] → Ue;
///  
///       $AE → AE;
///       $OE → OE;
///       $UE → UE;
///  
///       ::Any-ASCII;
///     "#.to_string(),
///     // legacy alias, doesn't actually do anything in this case
///     ["de-ASCII"],
///     false,
///     true,
/// );
/// collection.register_source(
///     &"und-t-und-latn-d0-ascii".parse().unwrap(),
///     "# ... ".to_string(),
///     // the previous transliterator refers to this one by the `Any-ASCII` ID,
///     // so it's important that the alias is listed here.
///     ["Latin-Ascii", "Any-ASCII"],
///     false,
///     true,
/// );
///
/// let t = Transliterator::try_new_unstable(&collection.as_provider(), &collection.as_provider(), &"de-t-de-d0-ascii".parse().unwrap()).unwrap();
/// assert_eq!(t.transliterate("Käse".into()), "Kaese");
#[allow(clippy::type_complexity)] // well
pub struct RuleCollection {
    id_mapping: BTreeMap<String, Locale>, // alias -> bcp id
    // these two maps need to lock together
    data: RefCell<(
        BTreeMap<String, (String, bool, bool)>, // marker-attributes -> source/reverse/visible
        BTreeMap<String, Result<DataResponse<TransliteratorRulesV1Marker>, DataError>>, // cache
    )>,
}

impl RuleCollection {
    /// Add a new transliteration source to the collection.
    pub fn register_source<'a>(
        &mut self,
        id: &icu_locale_core::Locale,
        source: String,
        aliases: impl IntoIterator<Item = &'a str>,
        reverse: bool,
        visible: bool,
    ) {
        self.data.borrow_mut().0.insert(
            id.to_string().to_ascii_lowercase(),
            (source, reverse, visible),
        );
        self.register_aliases(id, aliases)
    }

    /// Add transliteration ID aliases without registering a source.
    pub fn register_aliases<'a>(
        &mut self,
        id: &icu_locale_core::Locale,
        aliases: impl IntoIterator<Item = &'a str>,
    ) {
        for alias in aliases {
            self.id_mapping
                .entry(alias.to_ascii_lowercase())
                .and_modify(|prev| {
                    if prev != id {
                        icu_provider::log::warn!(
                            "Duplicate entry for alias for {alias}: {prev}, {id}"
                        );
                        // stability
                        if prev.to_string() > id.to_string() {
                            *prev = id.clone();
                        }
                    }
                })
                .or_insert(id.clone());
        }
    }

    /// Returns a provider that is usable by [`Transliterator::try_new_unstable`](crate::transliterate::Transliterator::try_new_unstable).
    ///
    /// ✨ *Enabled with the `compiled_data` Cargo feature.*
    #[cfg(feature = "compiled_data")]
    pub fn as_provider(
        &self,
    ) -> RuleCollectionProvider<'_, icu_properties::provider::Baked, icu_normalizer::provider::Baked>
    {
        RuleCollectionProvider {
            collection: self,
            properties_provider: &icu_properties::provider::Baked,
            normalizer_provider: &icu_normalizer::provider::Baked,
            xid_start: CodePointSetData::new::<XidStart>().static_to_owned(),
            xid_continue: CodePointSetData::new::<XidContinue>().static_to_owned(),
            pat_ws: CodePointSetData::new::<PatternWhiteSpace>().static_to_owned(),
        }
    }

    #[doc = icu_provider::gen_any_buffer_unstable_docs!(UNSTABLE, Self::as_provider)]
    pub fn as_provider_unstable<'a, PP, NP>(
        &'a self,
        properties_provider: &'a PP,
        normalizer_provider: &'a NP,
    ) -> Result<RuleCollectionProvider<'a, PP, NP>, DataError>
    where
        PP: ?Sized
            + DataProvider<AsciiHexDigitV1Marker>
            + DataProvider<AlphabeticV1Marker>
            + DataProvider<BidiControlV1Marker>
            + DataProvider<BidiMirroredV1Marker>
            + DataProvider<CaseIgnorableV1Marker>
            + DataProvider<CasedV1Marker>
            + DataProvider<ChangesWhenCasefoldedV1Marker>
            + DataProvider<ChangesWhenCasemappedV1Marker>
            + DataProvider<ChangesWhenLowercasedV1Marker>
            + DataProvider<ChangesWhenNfkcCasefoldedV1Marker>
            + DataProvider<ChangesWhenTitlecasedV1Marker>
            + DataProvider<ChangesWhenUppercasedV1Marker>
            + DataProvider<DashV1Marker>
            + DataProvider<DefaultIgnorableCodePointV1Marker>
            + DataProvider<DeprecatedV1Marker>
            + DataProvider<DiacriticV1Marker>
            + DataProvider<EmojiV1Marker>
            + DataProvider<EmojiComponentV1Marker>
            + DataProvider<EmojiModifierV1Marker>
            + DataProvider<EmojiModifierBaseV1Marker>
            + DataProvider<EmojiPresentationV1Marker>
            + DataProvider<ExtendedPictographicV1Marker>
            + DataProvider<ExtenderV1Marker>
            + DataProvider<GraphemeBaseV1Marker>
            + DataProvider<GraphemeClusterBreakV1Marker>
            + DataProvider<GraphemeClusterBreakNameToValueV2Marker>
            + DataProvider<GraphemeExtendV1Marker>
            + DataProvider<HexDigitV1Marker>
            + DataProvider<IdsBinaryOperatorV1Marker>
            + DataProvider<IdsTrinaryOperatorV1Marker>
            + DataProvider<IdContinueV1Marker>
            + DataProvider<IdStartV1Marker>
            + DataProvider<IdeographicV1Marker>
            + DataProvider<JoinControlV1Marker>
            + DataProvider<LogicalOrderExceptionV1Marker>
            + DataProvider<LowercaseV1Marker>
            + DataProvider<MathV1Marker>
            + DataProvider<NoncharacterCodePointV1Marker>
            + DataProvider<PatternSyntaxV1Marker>
            + DataProvider<PatternWhiteSpaceV1Marker>
            + DataProvider<QuotationMarkV1Marker>
            + DataProvider<RadicalV1Marker>
            + DataProvider<RegionalIndicatorV1Marker>
            + DataProvider<SentenceBreakV1Marker>
            + DataProvider<SentenceBreakNameToValueV2Marker>
            + DataProvider<SentenceTerminalV1Marker>
            + DataProvider<SoftDottedV1Marker>
            + DataProvider<TerminalPunctuationV1Marker>
            + DataProvider<UnifiedIdeographV1Marker>
            + DataProvider<UppercaseV1Marker>
            + DataProvider<VariationSelectorV1Marker>
            + DataProvider<WhiteSpaceV1Marker>
            + DataProvider<WordBreakV1Marker>
            + DataProvider<WordBreakNameToValueV2Marker>
            + DataProvider<XidContinueV1Marker>
            + DataProvider<GeneralCategoryMaskNameToValueV2Marker>
            + DataProvider<GeneralCategoryV1Marker>
            + DataProvider<ScriptNameToValueV2Marker>
            + DataProvider<ScriptV1Marker>
            + DataProvider<ScriptWithExtensionsPropertyV1Marker>
            + DataProvider<XidStartV1Marker>,
        NP: ?Sized
            + DataProvider<CanonicalDecompositionDataV1Marker>
            + DataProvider<CompatibilityDecompositionSupplementV1Marker>
            + DataProvider<CanonicalDecompositionTablesV1Marker>
            + DataProvider<CompatibilityDecompositionTablesV1Marker>
            + DataProvider<CanonicalCompositionsV1Marker>,
    {
        Ok(RuleCollectionProvider {
            collection: self,
            properties_provider,
            normalizer_provider,
            xid_start: CodePointSetData::try_new_unstable::<XidStart>(properties_provider)?,
            xid_continue: CodePointSetData::try_new_unstable::<XidContinue>(properties_provider)?,
            pat_ws: CodePointSetData::try_new_unstable::<PatternWhiteSpace>(properties_provider)?,
        })
    }
}

/// A provider that is usable by [`Transliterator::try_new_unstable`](crate::transliterate::Transliterator::try_new_unstable).
#[derive(Debug)]
pub struct RuleCollectionProvider<'a, PP: ?Sized, NP: ?Sized> {
    collection: &'a RuleCollection,
    properties_provider: &'a PP,
    normalizer_provider: &'a NP,
    xid_start: CodePointSetData,
    xid_continue: CodePointSetData,
    pat_ws: CodePointSetData,
}

impl<PP, NP> DataProvider<TransliteratorRulesV1Marker> for RuleCollectionProvider<'_, PP, NP>
where
    PP: ?Sized
        + DataProvider<AsciiHexDigitV1Marker>
        + DataProvider<AlphabeticV1Marker>
        + DataProvider<BidiControlV1Marker>
        + DataProvider<BidiMirroredV1Marker>
        + DataProvider<CanonicalCombiningClassV1Marker>
        + DataProvider<CanonicalCombiningClassNameToValueV2Marker>
        + DataProvider<CaseIgnorableV1Marker>
        + DataProvider<CasedV1Marker>
        + DataProvider<ChangesWhenCasefoldedV1Marker>
        + DataProvider<ChangesWhenCasemappedV1Marker>
        + DataProvider<ChangesWhenLowercasedV1Marker>
        + DataProvider<ChangesWhenNfkcCasefoldedV1Marker>
        + DataProvider<ChangesWhenTitlecasedV1Marker>
        + DataProvider<ChangesWhenUppercasedV1Marker>
        + DataProvider<DashV1Marker>
        + DataProvider<DefaultIgnorableCodePointV1Marker>
        + DataProvider<DeprecatedV1Marker>
        + DataProvider<DiacriticV1Marker>
        + DataProvider<EmojiV1Marker>
        + DataProvider<EmojiComponentV1Marker>
        + DataProvider<EmojiModifierV1Marker>
        + DataProvider<EmojiModifierBaseV1Marker>
        + DataProvider<EmojiPresentationV1Marker>
        + DataProvider<ExtendedPictographicV1Marker>
        + DataProvider<ExtenderV1Marker>
        + DataProvider<GraphemeBaseV1Marker>
        + DataProvider<GraphemeClusterBreakV1Marker>
        + DataProvider<GraphemeClusterBreakNameToValueV2Marker>
        + DataProvider<GraphemeExtendV1Marker>
        + DataProvider<HexDigitV1Marker>
        + DataProvider<IdsBinaryOperatorV1Marker>
        + DataProvider<IdsTrinaryOperatorV1Marker>
        + DataProvider<IdContinueV1Marker>
        + DataProvider<IdStartV1Marker>
        + DataProvider<IdeographicV1Marker>
        + DataProvider<JoinControlV1Marker>
        + DataProvider<LogicalOrderExceptionV1Marker>
        + DataProvider<LowercaseV1Marker>
        + DataProvider<MathV1Marker>
        + DataProvider<NoncharacterCodePointV1Marker>
        + DataProvider<PatternSyntaxV1Marker>
        + DataProvider<PatternWhiteSpaceV1Marker>
        + DataProvider<QuotationMarkV1Marker>
        + DataProvider<RadicalV1Marker>
        + DataProvider<RegionalIndicatorV1Marker>
        + DataProvider<SentenceBreakV1Marker>
        + DataProvider<SentenceBreakNameToValueV2Marker>
        + DataProvider<SentenceTerminalV1Marker>
        + DataProvider<SoftDottedV1Marker>
        + DataProvider<TerminalPunctuationV1Marker>
        + DataProvider<UnifiedIdeographV1Marker>
        + DataProvider<UppercaseV1Marker>
        + DataProvider<VariationSelectorV1Marker>
        + DataProvider<WhiteSpaceV1Marker>
        + DataProvider<WordBreakV1Marker>
        + DataProvider<WordBreakNameToValueV2Marker>
        + DataProvider<XidContinueV1Marker>
        + DataProvider<GeneralCategoryMaskNameToValueV2Marker>
        + DataProvider<GeneralCategoryV1Marker>
        + DataProvider<ScriptNameToValueV2Marker>
        + DataProvider<ScriptV1Marker>
        + DataProvider<ScriptWithExtensionsPropertyV1Marker>
        + DataProvider<XidStartV1Marker>,
    NP: ?Sized,
{
    fn load(
        &self,
        req: DataRequest,
    ) -> Result<DataResponse<TransliteratorRulesV1Marker>, DataError> {
        let mut exclusive_data = self.collection.data.borrow_mut();

        if let Some(response) = exclusive_data.1.get(req.id.marker_attributes.as_str()) {
            return response.clone();
        };

        let result = || -> Result<DataResponse<TransliteratorRulesV1Marker>, DataError> {
            let Some((source, reverse, visible)) =
                exclusive_data.0.remove(req.id.marker_attributes as &str)
            else {
                return Err(DataErrorKind::IdentifierNotFound
                    .with_req(TransliteratorRulesV1Marker::INFO, req));
            };

            let rules = parse::Parser::run(
                &source,
                &self.xid_start.to_code_point_inversion_list(),
                &self.xid_continue.to_code_point_inversion_list(),
                &self.pat_ws.to_code_point_inversion_list(),
                self.properties_provider,
            )
            .map_err(|e| {
                e.explain(&source)
                    .with_req(TransliteratorRulesV1Marker::INFO, req)
            })?;

            let pass1 = pass1::Pass1::run(
                if reverse {
                    Direction::Reverse
                } else {
                    Direction::Forward
                },
                &rules,
            )
            .map_err(|e| {
                e.explain(&source)
                    .with_req(TransliteratorRulesV1Marker::INFO, req)
            })?;

            let mut transliterator = pass2::Pass2::run(
                if reverse {
                    pass1.reverse_result
                } else {
                    pass1.forward_result
                },
                &pass1.variable_definitions,
                &self.collection.id_mapping,
            )
            .map_err(|e| {
                e.explain(&source)
                    .with_req(TransliteratorRulesV1Marker::INFO, req)
            })?;

            transliterator.visibility = visible;

            Ok(DataResponse {
                metadata: Default::default(),
                payload: DataPayload::from_owned(transliterator),
            })
        }();

        exclusive_data
            .1
            .insert(req.id.marker_attributes.to_string(), result.clone());

        result
    }
}

macro_rules! redirect {
    ($($marker:ty),*) => {
        $(
            impl<PP: ?Sized, NP: ?Sized + DataProvider<$marker>> DataProvider<$marker> for RuleCollectionProvider<'_, PP, NP> {
                fn load(&self, req: DataRequest) -> Result<DataResponse<$marker>, DataError> {
                    self.normalizer_provider.load(req)
                }
            }
        )*
    }
}

redirect!(
    CanonicalDecompositionDataV1Marker,
    CompatibilityDecompositionSupplementV1Marker,
    CanonicalDecompositionTablesV1Marker,
    CompatibilityDecompositionTablesV1Marker,
    CanonicalCompositionsV1Marker
);

#[cfg(feature = "datagen")]
impl<PP, NP> IterableDataProvider<TransliteratorRulesV1Marker>
    for RuleCollectionProvider<'_, PP, NP>
where
    PP: ?Sized
        + DataProvider<AsciiHexDigitV1Marker>
        + DataProvider<AlphabeticV1Marker>
        + DataProvider<BidiControlV1Marker>
        + DataProvider<BidiMirroredV1Marker>
        + DataProvider<CanonicalCombiningClassV1Marker>
        + DataProvider<CanonicalCombiningClassNameToValueV2Marker>
        + DataProvider<CaseIgnorableV1Marker>
        + DataProvider<CasedV1Marker>
        + DataProvider<ChangesWhenCasefoldedV1Marker>
        + DataProvider<ChangesWhenCasemappedV1Marker>
        + DataProvider<ChangesWhenLowercasedV1Marker>
        + DataProvider<ChangesWhenNfkcCasefoldedV1Marker>
        + DataProvider<ChangesWhenTitlecasedV1Marker>
        + DataProvider<ChangesWhenUppercasedV1Marker>
        + DataProvider<DashV1Marker>
        + DataProvider<DefaultIgnorableCodePointV1Marker>
        + DataProvider<DeprecatedV1Marker>
        + DataProvider<DiacriticV1Marker>
        + DataProvider<EmojiV1Marker>
        + DataProvider<EmojiComponentV1Marker>
        + DataProvider<EmojiModifierV1Marker>
        + DataProvider<EmojiModifierBaseV1Marker>
        + DataProvider<EmojiPresentationV1Marker>
        + DataProvider<ExtendedPictographicV1Marker>
        + DataProvider<ExtenderV1Marker>
        + DataProvider<GraphemeBaseV1Marker>
        + DataProvider<GraphemeClusterBreakV1Marker>
        + DataProvider<GraphemeClusterBreakNameToValueV2Marker>
        + DataProvider<GraphemeExtendV1Marker>
        + DataProvider<HexDigitV1Marker>
        + DataProvider<IdsBinaryOperatorV1Marker>
        + DataProvider<IdsTrinaryOperatorV1Marker>
        + DataProvider<IdContinueV1Marker>
        + DataProvider<IdStartV1Marker>
        + DataProvider<IdeographicV1Marker>
        + DataProvider<JoinControlV1Marker>
        + DataProvider<LogicalOrderExceptionV1Marker>
        + DataProvider<LowercaseV1Marker>
        + DataProvider<MathV1Marker>
        + DataProvider<NoncharacterCodePointV1Marker>
        + DataProvider<PatternSyntaxV1Marker>
        + DataProvider<PatternWhiteSpaceV1Marker>
        + DataProvider<QuotationMarkV1Marker>
        + DataProvider<RadicalV1Marker>
        + DataProvider<RegionalIndicatorV1Marker>
        + DataProvider<SentenceBreakV1Marker>
        + DataProvider<SentenceBreakNameToValueV2Marker>
        + DataProvider<SentenceTerminalV1Marker>
        + DataProvider<SoftDottedV1Marker>
        + DataProvider<TerminalPunctuationV1Marker>
        + DataProvider<UnifiedIdeographV1Marker>
        + DataProvider<UppercaseV1Marker>
        + DataProvider<VariationSelectorV1Marker>
        + DataProvider<WhiteSpaceV1Marker>
        + DataProvider<WordBreakV1Marker>
        + DataProvider<WordBreakNameToValueV2Marker>
        + DataProvider<XidContinueV1Marker>
        + DataProvider<GeneralCategoryMaskNameToValueV2Marker>
        + DataProvider<GeneralCategoryV1Marker>
        + DataProvider<ScriptNameToValueV2Marker>
        + DataProvider<ScriptV1Marker>
        + DataProvider<ScriptWithExtensionsPropertyV1Marker>
        + DataProvider<XidStartV1Marker>,
    NP: ?Sized,
{
    fn iter_ids(&self) -> Result<std::collections::BTreeSet<DataIdentifierCow>, DataError> {
        let exclusive_data = self.collection.data.borrow();
        Ok(exclusive_data
            .0
            .keys()
            .cloned()
            .chain(exclusive_data.1.keys().cloned())
            .filter_map(|s| {
                Some(DataIdentifierCow::from_marker_attributes_owned(
                    DataMarkerAttributes::try_from_string(s).ok()?,
                ))
            })
            .collect())
    }
}

struct CompileError {
    /// offset is the index to an arbitrary byte in the last character in the source that makes sense
    /// to display as location for the error, e.g., the unexpected character itself or
    /// for an unknown property name the last character of the name.
    offset: Option<usize>,
    /// The type of compile error
    kind: CompileErrorKind,
}

impl CompileError {
    fn explain(self, source: &str) -> DataError {
        let e = DataError::custom("Invalid transliterator");
        if let Some(mut col_number) = self.offset {
            let mut line_number = 1;
            if let Some(snippet) = source
                .lines()
                .filter_map(|line| {
                    if let Some(snippet) = line.get(col_number..) {
                        Some(snippet)
                    } else {
                        col_number -= line.len();
                        col_number -= 1; // \n
                        line_number += 1;
                        None
                    }
                })
                .next()
            {
                e.with_display_context(&format!("at {line_number}:{col_number} '{snippet}'"));
            }
        }
        e.with_debug_context(&self.kind);
        e
    }
}

/// The kind of compile error that occurred.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
enum CompileErrorKind {
    /// An unexpected character was encountered. This variant implies the other variants
    /// (notably `UnknownProperty` and `Unimplemented`) do not apply.
    UnexpectedChar(char),
    /// A reference to an unknown variable.
    UnknownVariable,
    /// The source is incomplete.
    Eof,
    /// Something unexpected went wrong with our code. Please file a bug report on GitHub.
    Internal(&'static str),
    /// The provided syntax is not supported by us. Please file an issue on GitHub if you need
    /// this feature.
    Unimplemented,
    /// The provided escape sequence is not a valid Unicode code point.
    InvalidEscape,
    /// The provided transform ID is invalid.
    InvalidId,
    /// The provided number is invalid, which likely means it's too big.
    InvalidNumber,
    /// Duplicate variable definition.
    DuplicateVariable,
    /// Invalid UnicodeSet syntax. See `crate::unicodeset_parse`'s [`ParseError`](crate::unicodeset_parse::ParseError).
    UnicodeSetError(crate::unicodeset_parse::ParseError),

    // errors originating from compilation step
    /// A global filter (forward or backward) in an unexpected position.
    UnexpectedGlobalFilter,
    /// A global filter (forward or backward) may not contain strings.
    GlobalFilterWithStrings,
    /// An element appeared on the source side of a rule, but that is prohibited.
    UnexpectedElementInSource(&'static str),
    /// An element appeared on the target side of a rule, but that is prohibited.
    UnexpectedElementInTarget(&'static str),
    /// An element appeared in a variable definition, but that is prohibited.
    UnexpectedElementInVariableDefinition(&'static str),
    /// The start anchor `^` was not placed at the beginning of a source.
    AnchorStartNotAtStart,
    /// The end anchor `$` was not placed at the end of a source.
    AnchorEndNotAtEnd,
    /// A variable that contains source-only matchers (e.g., UnicodeSets) was used on the target side.
    SourceOnlyVariable,
    /// No matching segment for this backreference was found.
    BackReferenceOutOfRange,
    /// The cursor is in an invalid position.
    InvalidCursor,
    /// Multiple cursors were defined.
    DuplicateCursor,
    /// There are too many special matchers/replacers/variables in the source.
    TooManySpecials,
}

impl CompileErrorKind {
    fn with_offset(self, offset: usize) -> CompileError {
        CompileError {
            offset: Some(offset),
            kind: self,
        }
    }
}

impl From<CompileErrorKind> for CompileError {
    fn from(kind: CompileErrorKind) -> Self {
        CompileError { offset: None, kind }
    }
}

#[cfg(test)]
mod tests {
    use alloc::borrow::Cow;

    use super::*;
    use crate::transliterate::provider as ds;
    use icu_locale_core::locale;
    use std::collections::HashSet;
    use zerovec::{vecs::Index32, VarZeroVec};

    fn parse_set(source: &str) -> super::parse::UnicodeSet {
        crate::unicodeset_parse::parse_unstable(source, &icu_properties::provider::Baked)
            .expect("Parsing failed")
            .0
    }

    fn parse_set_cp(source: &str) -> super::parse::FilterSet {
        crate::unicodeset_parse::parse_unstable(source, &icu_properties::provider::Baked)
            .expect("Parsing failed")
            .0
            .code_points()
            .clone()
    }

    #[test]
    fn test_source_to_struct() {
        let source = r"
        use variable range 0xFFF 0xFFFF ;
        :: [1] ;
        :: Latin-InterIndic ;
        $a = [a] [b]+ ;
        $unused = [c{string}]+? ;
        $b = $a? 'literal chars' ;
        x } [a-z] > |@@@y ;
        $a > ab ;
        'reverse output:' &RevFnCall($1 'padding') @@ | < ($b) ;
        ^ left } $ <> ^ { rig|ht } [0-9] $ ;
        :: [\ ] Remove (AnyRev-AddRandomSpaces/FiftyPercent) ;
        # splits up the forward rules
        forward rule that > splits up rule groups ;
        :: InterIndic-Devanagari ;
        :: NFC ;
        ";

        let mut collection = RuleCollection::default();
        collection.register_source(&locale!("fwd"), source.into(), [], false, true);
        collection.register_source(&locale!("rev"), source.into(), [], true, true);
        collection.register_source(
            &"und-t-d0-addrndsp-m0-fifty-s0-anyrev".parse().unwrap(),
            "unparsed dummy".into(),
            ["AnyRev-AddRandomSpaces/FiftyPercent"],
            false,
            true,
        );

        let forward: DataResponse<TransliteratorRulesV1Marker> = collection
            .as_provider()
            .load(DataRequest {
                id: DataIdentifierBorrowed::for_marker_attributes(
                    DataMarkerAttributes::from_str_or_panic("fwd"),
                ),
                ..Default::default()
            })
            .unwrap();

        let reverse: DataResponse<TransliteratorRulesV1Marker> = collection
            .as_provider()
            .load(DataRequest {
                id: DataIdentifierBorrowed::for_marker_attributes(
                    DataMarkerAttributes::from_str_or_panic("rev"),
                ),

                ..Default::default()
            })
            .unwrap();
        {
            let expected_filter = parse_set_cp("[1]");

            let expected_id_group1 = vec![ds::SimpleId {
                filter: parse::FilterSet::all(),
                id: Cow::Borrowed("x-latin-interindic"),
            }];
            let expected_id_group2 = vec![ds::SimpleId {
                filter: parse_set_cp(r"[\ ]"),
                id: Cow::Borrowed("any-remove"),
            }];
            let expected_id_group3 = vec![
                ds::SimpleId {
                    filter: parse::FilterSet::all(),
                    id: Cow::Borrowed("x-interindic-devanagari"),
                },
                ds::SimpleId {
                    filter: parse::FilterSet::all(),
                    id: Cow::Borrowed("any-nfc"),
                },
            ];

            let expected_id_group_list: Vec<VarZeroVec<'_, ds::SimpleIdULE>> = vec![
                VarZeroVec::from(&expected_id_group1),
                VarZeroVec::from(&expected_id_group2),
                VarZeroVec::from(&expected_id_group3),
            ];

            let expected_rule_group1 = vec![
                ds::Rule {
                    ante: Cow::Borrowed(""),
                    key: Cow::Borrowed("x"),
                    post: Cow::Borrowed("\u{F0002}"),
                    replacer: Cow::Borrowed("\u{F0007}y"), // `|@@@`
                },
                ds::Rule {
                    ante: Cow::Borrowed(""),
                    key: Cow::Borrowed("\u{F0000}"),
                    post: Cow::Borrowed(""),
                    replacer: Cow::Borrowed("ab"),
                },
                ds::Rule {
                    ante: Cow::Borrowed(""),
                    key: Cow::Borrowed("\u{FFFFC}left"),
                    post: Cow::Borrowed("\u{FFFFD}"),
                    replacer: Cow::Borrowed("rig\u{FFFFB}ht"), // `|`
                },
            ];
            let expected_rule_group2 = vec![ds::Rule {
                ante: Cow::Borrowed(""),
                key: Cow::Borrowed("forwardrulethat"),
                post: Cow::Borrowed(""),
                replacer: Cow::Borrowed("splitsuprulegroups"),
            }];

            let expected_rule_group_list: Vec<VarZeroVec<'_, ds::RuleULE, Index32>> = vec![
                VarZeroVec::from(&expected_rule_group1),
                VarZeroVec::from(&expected_rule_group2),
                VarZeroVec::new(), // empty rule group after the last transform rule
            ];

            let expected_compounds = vec![
                "\u{F0003}\u{F0001}", // [a] and [b]+ (the quantifier contains [b])
            ];

            let expected_quantifiers_kleene_plus = vec![
                "\u{F0004}", // [b] from [b]+
            ];

            let expected_unicode_sets =
                vec![parse_set("[a-z]"), parse_set("[a]"), parse_set("[b]")];

            let expected_var_table = ds::VarTable {
                compounds: VarZeroVec::from(&expected_compounds),
                quantifiers_opt: VarZeroVec::new(),
                quantifiers_kleene: VarZeroVec::new(),
                quantifiers_kleene_plus: VarZeroVec::from(&expected_quantifiers_kleene_plus),
                segments: VarZeroVec::new(),
                unicode_sets: VarZeroVec::from(&expected_unicode_sets),
                function_calls: VarZeroVec::new(),
                max_left_placeholder_count: 0,
                max_right_placeholder_count: 3,
            };

            let expected_rbt = ds::RuleBasedTransliterator {
                filter: expected_filter,
                id_group_list: VarZeroVec::from(&expected_id_group_list),
                rule_group_list: VarZeroVec::from(&expected_rule_group_list),
                variable_table: expected_var_table,
                visibility: true,
            };
            assert_eq!(*forward.payload.get(), expected_rbt);

            assert_eq!(
                forward.payload.get().deps().collect::<HashSet<_>>(),
                HashSet::from_iter([
                    Cow::Borrowed("any-nfc"),
                    Cow::Borrowed("any-remove"),
                    Cow::Borrowed("x-interindic-devanagari"),
                    Cow::Borrowed("x-latin-interindic"),
                ])
            );
        }
        {
            let expected_filter = parse::FilterSet::all();

            let expected_id_group1 = vec![
                ds::SimpleId {
                    filter: parse::FilterSet::all(),
                    id: Cow::Borrowed("any-nfd"),
                },
                ds::SimpleId {
                    filter: parse::FilterSet::all(),
                    id: Cow::Borrowed("x-devanagari-interindic"),
                },
                ds::SimpleId {
                    filter: parse::FilterSet::all(),
                    id: Cow::Borrowed("und-t-d0-addrndsp-m0-fifty-s0-anyrev"),
                },
            ];
            let expected_id_group2 = vec![ds::SimpleId {
                filter: parse::FilterSet::all(),
                id: Cow::Borrowed("x-interindic-latin"),
            }];

            let expected_id_group_list: Vec<VarZeroVec<'_, ds::SimpleIdULE>> = vec![
                VarZeroVec::from(&expected_id_group1),
                VarZeroVec::from(&expected_id_group2),
            ];

            let expected_rule_group1 = vec![
                ds::Rule {
                    ante: Cow::Borrowed(""),
                    key: Cow::Borrowed("\u{F0004}"),
                    post: Cow::Borrowed(""),
                    replacer: Cow::Borrowed("reverse output:\u{F0008}\u{F000A}"), /* `@@|` and function call */
                },
                ds::Rule {
                    ante: Cow::Borrowed("\u{FFFFC}"), // start anchor
                    key: Cow::Borrowed("right"),
                    post: Cow::Borrowed("\u{F0007}\u{FFFFD}"), // [0-9] and end anchor
                    replacer: Cow::Borrowed("left"),
                },
            ];

            let expected_rule_group_list: Vec<VarZeroVec<'_, ds::RuleULE, Index32>> =
                vec![VarZeroVec::from(&expected_rule_group1), VarZeroVec::new()];

            let expected_compounds = vec![
                "\u{F0005}\u{F0003}",     // $a = [a] [b]+ (quantifier contains [b])
                "\u{F0002}literal chars", // $b = $a? (quantifier contains $a)
            ];

            let expected_quantifers_opt = vec![
                "\u{F0000}", // $a from $a?
            ];

            let expected_quantifiers_kleene_plus = vec![
                "\u{F0006}", // [b] from [b]+
            ];

            let expected_segments = vec![ds::Segment {
                idx: 0,
                content: Cow::Borrowed("\u{F0001}"), // $b from ($b)
            }];

            let expected_unicode_sets =
                vec![parse_set("[a]"), parse_set("[b]"), parse_set("[0-9]")];

            let expected_function_calls = vec![ds::FunctionCall {
                arg: Cow::Borrowed("\u{F000B}padding"), // $1 and 'padding'
                translit: ds::SimpleId {
                    filter: parse::FilterSet::all(),
                    id: Cow::Borrowed("x-any-revfncall"),
                },
            }];

            let expected_var_table = ds::VarTable {
                compounds: VarZeroVec::from(&expected_compounds),
                quantifiers_opt: VarZeroVec::from(&expected_quantifers_opt),
                quantifiers_kleene: VarZeroVec::new(),
                quantifiers_kleene_plus: VarZeroVec::from(&expected_quantifiers_kleene_plus),
                segments: VarZeroVec::from(&expected_segments),
                unicode_sets: VarZeroVec::from(&expected_unicode_sets),
                function_calls: VarZeroVec::from(&expected_function_calls),
                max_left_placeholder_count: 2,
                max_right_placeholder_count: 0,
            };

            let expected_rbt = ds::RuleBasedTransliterator {
                filter: expected_filter,
                id_group_list: VarZeroVec::from(&expected_id_group_list),
                rule_group_list: VarZeroVec::from(&expected_rule_group_list),
                variable_table: expected_var_table,
                visibility: true,
            };
            assert_eq!(*reverse.payload.get(), expected_rbt);

            assert_eq!(
                reverse.payload.get().deps().collect::<HashSet<_>>(),
                HashSet::from_iter([
                    Cow::Borrowed("und-t-d0-addrndsp-m0-fifty-s0-anyrev"),
                    Cow::Borrowed("any-nfd"),
                    Cow::Borrowed("x-any-revfncall"),
                    Cow::Borrowed("x-devanagari-interindic"),
                    Cow::Borrowed("x-interindic-latin"),
                ])
            );
        }
    }
}