summaryrefslogtreecommitdiff
path: root/vendor/github.com/BurntSushi/toml/lex.go
blob: ce7f546b4e3ba8f7925878e6e4850699cc3c968d (plain)
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
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
package toml

import (
	"fmt"
	"reflect"
	"runtime"
	"strings"
	"unicode"
	"unicode/utf8"
)

type itemType int

const (
	itemError itemType = iota
	itemNIL            // used in the parser to indicate no type
	itemEOF
	itemText
	itemString
	itemRawString
	itemMultilineString
	itemRawMultilineString
	itemBool
	itemInteger
	itemFloat
	itemDatetime
	itemArray // the start of an array
	itemArrayEnd
	itemTableStart
	itemTableEnd
	itemArrayTableStart
	itemArrayTableEnd
	itemKeyStart
	itemKeyEnd
	itemCommentStart
	itemInlineTableStart
	itemInlineTableEnd
)

const eof = 0

type stateFn func(lx *lexer) stateFn

func (p Position) String() string {
	return fmt.Sprintf("at line %d; start %d; length %d", p.Line, p.Start, p.Len)
}

type lexer struct {
	input string
	start int
	pos   int
	line  int
	state stateFn
	items chan item

	// Allow for backing up up to 4 runes. This is necessary because TOML
	// contains 3-rune tokens (""" and ''').
	prevWidths [4]int
	nprev      int  // how many of prevWidths are in use
	atEOF      bool // If we emit an eof, we can still back up, but it is not OK to call next again.

	// A stack of state functions used to maintain context.
	//
	// The idea is to reuse parts of the state machine in various places. For
	// example, values can appear at the top level or within arbitrarily nested
	// arrays. The last state on the stack is used after a value has been lexed.
	// Similarly for comments.
	stack []stateFn
}

type item struct {
	typ itemType
	val string
	err error
	pos Position
}

func (lx *lexer) nextItem() item {
	for {
		select {
		case item := <-lx.items:
			return item
		default:
			lx.state = lx.state(lx)
			//fmt.Printf("     STATE %-24s  current: %-10q	stack: %s\n", lx.state, lx.current(), lx.stack)
		}
	}
}

func lex(input string) *lexer {
	lx := &lexer{
		input: input,
		state: lexTop,
		items: make(chan item, 10),
		stack: make([]stateFn, 0, 10),
		line:  1,
	}
	return lx
}

func (lx *lexer) push(state stateFn) {
	lx.stack = append(lx.stack, state)
}

func (lx *lexer) pop() stateFn {
	if len(lx.stack) == 0 {
		return lx.errorf("BUG in lexer: no states to pop")
	}
	last := lx.stack[len(lx.stack)-1]
	lx.stack = lx.stack[0 : len(lx.stack)-1]
	return last
}

func (lx *lexer) current() string {
	return lx.input[lx.start:lx.pos]
}

func (lx lexer) getPos() Position {
	p := Position{
		Line:  lx.line,
		Start: lx.start,
		Len:   lx.pos - lx.start,
	}
	if p.Len <= 0 {
		p.Len = 1
	}
	return p
}

func (lx *lexer) emit(typ itemType) {
	// Needed for multiline strings ending with an incomplete UTF-8 sequence.
	if lx.start > lx.pos {
		lx.error(errLexUTF8{lx.input[lx.pos]})
		return
	}
	lx.items <- item{typ: typ, pos: lx.getPos(), val: lx.current()}
	lx.start = lx.pos
}

func (lx *lexer) emitTrim(typ itemType) {
	lx.items <- item{typ: typ, pos: lx.getPos(), val: strings.TrimSpace(lx.current())}
	lx.start = lx.pos
}

func (lx *lexer) next() (r rune) {
	if lx.atEOF {
		panic("BUG in lexer: next called after EOF")
	}
	if lx.pos >= len(lx.input) {
		lx.atEOF = true
		return eof
	}

	if lx.input[lx.pos] == '\n' {
		lx.line++
	}
	lx.prevWidths[3] = lx.prevWidths[2]
	lx.prevWidths[2] = lx.prevWidths[1]
	lx.prevWidths[1] = lx.prevWidths[0]
	if lx.nprev < 4 {
		lx.nprev++
	}

	r, w := utf8.DecodeRuneInString(lx.input[lx.pos:])
	if r == utf8.RuneError {
		lx.error(errLexUTF8{lx.input[lx.pos]})
		return utf8.RuneError
	}

	// Note: don't use peek() here, as this calls next().
	if isControl(r) || (r == '\r' && (len(lx.input)-1 == lx.pos || lx.input[lx.pos+1] != '\n')) {
		lx.errorControlChar(r)
		return utf8.RuneError
	}

	lx.prevWidths[0] = w
	lx.pos += w
	return r
}

// ignore skips over the pending input before this point.
func (lx *lexer) ignore() {
	lx.start = lx.pos
}

// backup steps back one rune. Can be called 4 times between calls to next.
func (lx *lexer) backup() {
	if lx.atEOF {
		lx.atEOF = false
		return
	}
	if lx.nprev < 1 {
		panic("BUG in lexer: backed up too far")
	}
	w := lx.prevWidths[0]
	lx.prevWidths[0] = lx.prevWidths[1]
	lx.prevWidths[1] = lx.prevWidths[2]
	lx.prevWidths[2] = lx.prevWidths[3]
	lx.nprev--

	lx.pos -= w
	if lx.pos < len(lx.input) && lx.input[lx.pos] == '\n' {
		lx.line--
	}
}

// accept consumes the next rune if it's equal to `valid`.
func (lx *lexer) accept(valid rune) bool {
	if lx.next() == valid {
		return true
	}
	lx.backup()
	return false
}

// peek returns but does not consume the next rune in the input.
func (lx *lexer) peek() rune {
	r := lx.next()
	lx.backup()
	return r
}

// skip ignores all input that matches the given predicate.
func (lx *lexer) skip(pred func(rune) bool) {
	for {
		r := lx.next()
		if pred(r) {
			continue
		}
		lx.backup()
		lx.ignore()
		return
	}
}

// error stops all lexing by emitting an error and returning `nil`.
//
// Note that any value that is a character is escaped if it's a special
// character (newlines, tabs, etc.).
func (lx *lexer) error(err error) stateFn {
	if lx.atEOF {
		return lx.errorPrevLine(err)
	}
	lx.items <- item{typ: itemError, pos: lx.getPos(), err: err}
	return nil
}

// errorfPrevline is like error(), but sets the position to the last column of
// the previous line.
//
// This is so that unexpected EOF or NL errors don't show on a new blank line.
func (lx *lexer) errorPrevLine(err error) stateFn {
	pos := lx.getPos()
	pos.Line--
	pos.Len = 1
	pos.Start = lx.pos - 1
	lx.items <- item{typ: itemError, pos: pos, err: err}
	return nil
}

// errorPos is like error(), but allows explicitly setting the position.
func (lx *lexer) errorPos(start, length int, err error) stateFn {
	pos := lx.getPos()
	pos.Start = start
	pos.Len = length
	lx.items <- item{typ: itemError, pos: pos, err: err}
	return nil
}

// errorf is like error, and creates a new error.
func (lx *lexer) errorf(format string, values ...interface{}) stateFn {
	if lx.atEOF {
		pos := lx.getPos()
		pos.Line--
		pos.Len = 1
		pos.Start = lx.pos - 1
		lx.items <- item{typ: itemError, pos: pos, err: fmt.Errorf(format, values...)}
		return nil
	}
	lx.items <- item{typ: itemError, pos: lx.getPos(), err: fmt.Errorf(format, values...)}
	return nil
}

func (lx *lexer) errorControlChar(cc rune) stateFn {
	return lx.errorPos(lx.pos-1, 1, errLexControl{cc})
}

// lexTop consumes elements at the top level of TOML data.
func lexTop(lx *lexer) stateFn {
	r := lx.next()
	if isWhitespace(r) || isNL(r) {
		return lexSkip(lx, lexTop)
	}
	switch r {
	case '#':
		lx.push(lexTop)
		return lexCommentStart
	case '[':
		return lexTableStart
	case eof:
		if lx.pos > lx.start {
			return lx.errorf("unexpected EOF")
		}
		lx.emit(itemEOF)
		return nil
	}

	// At this point, the only valid item can be a key, so we back up
	// and let the key lexer do the rest.
	lx.backup()
	lx.push(lexTopEnd)
	return lexKeyStart
}

// lexTopEnd is entered whenever a top-level item has been consumed. (A value
// or a table.) It must see only whitespace, and will turn back to lexTop
// upon a newline. If it sees EOF, it will quit the lexer successfully.
func lexTopEnd(lx *lexer) stateFn {
	r := lx.next()
	switch {
	case r == '#':
		// a comment will read to a newline for us.
		lx.push(lexTop)
		return lexCommentStart
	case isWhitespace(r):
		return lexTopEnd
	case isNL(r):
		lx.ignore()
		return lexTop
	case r == eof:
		lx.emit(itemEOF)
		return nil
	}
	return lx.errorf(
		"expected a top-level item to end with a newline, comment, or EOF, but got %q instead",
		r)
}

// lexTable lexes the beginning of a table. Namely, it makes sure that
// it starts with a character other than '.' and ']'.
// It assumes that '[' has already been consumed.
// It also handles the case that this is an item in an array of tables.
// e.g., '[[name]]'.
func lexTableStart(lx *lexer) stateFn {
	if lx.peek() == '[' {
		lx.next()
		lx.emit(itemArrayTableStart)
		lx.push(lexArrayTableEnd)
	} else {
		lx.emit(itemTableStart)
		lx.push(lexTableEnd)
	}
	return lexTableNameStart
}

func lexTableEnd(lx *lexer) stateFn {
	lx.emit(itemTableEnd)
	return lexTopEnd
}

func lexArrayTableEnd(lx *lexer) stateFn {
	if r := lx.next(); r != ']' {
		return lx.errorf("expected end of table array name delimiter ']', but got %q instead", r)
	}
	lx.emit(itemArrayTableEnd)
	return lexTopEnd
}

func lexTableNameStart(lx *lexer) stateFn {
	lx.skip(isWhitespace)
	switch r := lx.peek(); {
	case r == ']' || r == eof:
		return lx.errorf("unexpected end of table name (table names cannot be empty)")
	case r == '.':
		return lx.errorf("unexpected table separator (table names cannot be empty)")
	case r == '"' || r == '\'':
		lx.ignore()
		lx.push(lexTableNameEnd)
		return lexQuotedName
	default:
		lx.push(lexTableNameEnd)
		return lexBareName
	}
}

// lexTableNameEnd reads the end of a piece of a table name, optionally
// consuming whitespace.
func lexTableNameEnd(lx *lexer) stateFn {
	lx.skip(isWhitespace)
	switch r := lx.next(); {
	case isWhitespace(r):
		return lexTableNameEnd
	case r == '.':
		lx.ignore()
		return lexTableNameStart
	case r == ']':
		return lx.pop()
	default:
		return lx.errorf("expected '.' or ']' to end table name, but got %q instead", r)
	}
}

// lexBareName lexes one part of a key or table.
//
// It assumes that at least one valid character for the table has already been
// read.
//
// Lexes only one part, e.g. only 'a' inside 'a.b'.
func lexBareName(lx *lexer) stateFn {
	r := lx.next()
	if isBareKeyChar(r) {
		return lexBareName
	}
	lx.backup()
	lx.emit(itemText)
	return lx.pop()
}

// lexBareName lexes one part of a key or table.
//
// It assumes that at least one valid character for the table has already been
// read.
//
// Lexes only one part, e.g. only '"a"' inside '"a".b'.
func lexQuotedName(lx *lexer) stateFn {
	r := lx.next()
	switch {
	case isWhitespace(r):
		return lexSkip(lx, lexValue)
	case r == '"':
		lx.ignore() // ignore the '"'
		return lexString
	case r == '\'':
		lx.ignore() // ignore the "'"
		return lexRawString
	case r == eof:
		return lx.errorf("unexpected EOF; expected value")
	default:
		return lx.errorf("expected value but found %q instead", r)
	}
}

// lexKeyStart consumes all key parts until a '='.
func lexKeyStart(lx *lexer) stateFn {
	lx.skip(isWhitespace)
	switch r := lx.peek(); {
	case r == '=' || r == eof:
		return lx.errorf("unexpected '=': key name appears blank")
	case r == '.':
		return lx.errorf("unexpected '.': keys cannot start with a '.'")
	case r == '"' || r == '\'':
		lx.ignore()
		fallthrough
	default: // Bare key
		lx.emit(itemKeyStart)
		return lexKeyNameStart
	}
}

func lexKeyNameStart(lx *lexer) stateFn {
	lx.skip(isWhitespace)
	switch r := lx.peek(); {
	case r == '=' || r == eof:
		return lx.errorf("unexpected '='")
	case r == '.':
		return lx.errorf("unexpected '.'")
	case r == '"' || r == '\'':
		lx.ignore()
		lx.push(lexKeyEnd)
		return lexQuotedName
	default:
		lx.push(lexKeyEnd)
		return lexBareName
	}
}

// lexKeyEnd consumes the end of a key and trims whitespace (up to the key
// separator).
func lexKeyEnd(lx *lexer) stateFn {
	lx.skip(isWhitespace)
	switch r := lx.next(); {
	case isWhitespace(r):
		return lexSkip(lx, lexKeyEnd)
	case r == eof:
		return lx.errorf("unexpected EOF; expected key separator '='")
	case r == '.':
		lx.ignore()
		return lexKeyNameStart
	case r == '=':
		lx.emit(itemKeyEnd)
		return lexSkip(lx, lexValue)
	default:
		return lx.errorf("expected '.' or '=', but got %q instead", r)
	}
}

// lexValue starts the consumption of a value anywhere a value is expected.
// lexValue will ignore whitespace.
// After a value is lexed, the last state on the next is popped and returned.
func lexValue(lx *lexer) stateFn {
	// We allow whitespace to precede a value, but NOT newlines.
	// In array syntax, the array states are responsible for ignoring newlines.
	r := lx.next()
	switch {
	case isWhitespace(r):
		return lexSkip(lx, lexValue)
	case isDigit(r):
		lx.backup() // avoid an extra state and use the same as above
		return lexNumberOrDateStart
	}
	switch r {
	case '[':
		lx.ignore()
		lx.emit(itemArray)
		return lexArrayValue
	case '{':
		lx.ignore()
		lx.emit(itemInlineTableStart)
		return lexInlineTableValue
	case '"':
		if lx.accept('"') {
			if lx.accept('"') {
				lx.ignore() // Ignore """
				return lexMultilineString
			}
			lx.backup()
		}
		lx.ignore() // ignore the '"'
		return lexString
	case '\'':
		if lx.accept('\'') {
			if lx.accept('\'') {
				lx.ignore() // Ignore """
				return lexMultilineRawString
			}
			lx.backup()
		}
		lx.ignore() // ignore the "'"
		return lexRawString
	case '.': // special error case, be kind to users
		return lx.errorf("floats must start with a digit, not '.'")
	case 'i', 'n':
		if (lx.accept('n') && lx.accept('f')) || (lx.accept('a') && lx.accept('n')) {
			lx.emit(itemFloat)
			return lx.pop()
		}
	case '-', '+':
		return lexDecimalNumberStart
	}
	if unicode.IsLetter(r) {
		// Be permissive here; lexBool will give a nice error if the
		// user wrote something like
		//   x = foo
		// (i.e. not 'true' or 'false' but is something else word-like.)
		lx.backup()
		return lexBool
	}
	if r == eof {
		return lx.errorf("unexpected EOF; expected value")
	}
	return lx.errorf("expected value but found %q instead", r)
}

// lexArrayValue consumes one value in an array. It assumes that '[' or ','
// have already been consumed. All whitespace and newlines are ignored.
func lexArrayValue(lx *lexer) stateFn {
	r := lx.next()
	switch {
	case isWhitespace(r) || isNL(r):
		return lexSkip(lx, lexArrayValue)
	case r == '#':
		lx.push(lexArrayValue)
		return lexCommentStart
	case r == ',':
		return lx.errorf("unexpected comma")
	case r == ']':
		return lexArrayEnd
	}

	lx.backup()
	lx.push(lexArrayValueEnd)
	return lexValue
}

// lexArrayValueEnd consumes everything between the end of an array value and
// the next value (or the end of the array): it ignores whitespace and newlines
// and expects either a ',' or a ']'.
func lexArrayValueEnd(lx *lexer) stateFn {
	switch r := lx.next(); {
	case isWhitespace(r) || isNL(r):
		return lexSkip(lx, lexArrayValueEnd)
	case r == '#':
		lx.push(lexArrayValueEnd)
		return lexCommentStart
	case r == ',':
		lx.ignore()
		return lexArrayValue // move on to the next value
	case r == ']':
		return lexArrayEnd
	default:
		return lx.errorf("expected a comma (',') or array terminator (']'), but got %s", runeOrEOF(r))
	}
}

// lexArrayEnd finishes the lexing of an array.
// It assumes that a ']' has just been consumed.
func lexArrayEnd(lx *lexer) stateFn {
	lx.ignore()
	lx.emit(itemArrayEnd)
	return lx.pop()
}

// lexInlineTableValue consumes one key/value pair in an inline table.
// It assumes that '{' or ',' have already been consumed. Whitespace is ignored.
func lexInlineTableValue(lx *lexer) stateFn {
	r := lx.next()
	switch {
	case isWhitespace(r):
		return lexSkip(lx, lexInlineTableValue)
	case isNL(r):
		return lx.errorPrevLine(errLexInlineTableNL{})
	case r == '#':
		lx.push(lexInlineTableValue)
		return lexCommentStart
	case r == ',':
		return lx.errorf("unexpected comma")
	case r == '}':
		return lexInlineTableEnd
	}
	lx.backup()
	lx.push(lexInlineTableValueEnd)
	return lexKeyStart
}

// lexInlineTableValueEnd consumes everything between the end of an inline table
// key/value pair and the next pair (or the end of the table):
// it ignores whitespace and expects either a ',' or a '}'.
func lexInlineTableValueEnd(lx *lexer) stateFn {
	switch r := lx.next(); {
	case isWhitespace(r):
		return lexSkip(lx, lexInlineTableValueEnd)
	case isNL(r):
		return lx.errorPrevLine(errLexInlineTableNL{})
	case r == '#':
		lx.push(lexInlineTableValueEnd)
		return lexCommentStart
	case r == ',':
		lx.ignore()
		lx.skip(isWhitespace)
		if lx.peek() == '}' {
			return lx.errorf("trailing comma not allowed in inline tables")
		}
		return lexInlineTableValue
	case r == '}':
		return lexInlineTableEnd
	default:
		return lx.errorf("expected a comma or an inline table terminator '}', but got %s instead", runeOrEOF(r))
	}
}

func runeOrEOF(r rune) string {
	if r == eof {
		return "end of file"
	}
	return "'" + string(r) + "'"
}

// lexInlineTableEnd finishes the lexing of an inline table.
// It assumes that a '}' has just been consumed.
func lexInlineTableEnd(lx *lexer) stateFn {
	lx.ignore()
	lx.emit(itemInlineTableEnd)
	return lx.pop()
}

// lexString consumes the inner contents of a string. It assumes that the
// beginning '"' has already been consumed and ignored.
func lexString(lx *lexer) stateFn {
	r := lx.next()
	switch {
	case r == eof:
		return lx.errorf(`unexpected EOF; expected '"'`)
	case isNL(r):
		return lx.errorPrevLine(errLexStringNL{})
	case r == '\\':
		lx.push(lexString)
		return lexStringEscape
	case r == '"':
		lx.backup()
		lx.emit(itemString)
		lx.next()
		lx.ignore()
		return lx.pop()
	}
	return lexString
}

// lexMultilineString consumes the inner contents of a string. It assumes that
// the beginning '"""' has already been consumed and ignored.
func lexMultilineString(lx *lexer) stateFn {
	r := lx.next()
	switch r {
	default:
		return lexMultilineString
	case eof:
		return lx.errorf(`unexpected EOF; expected '"""'`)
	case '\\':
		return lexMultilineStringEscape
	case '"':
		/// Found " → try to read two more "".
		if lx.accept('"') {
			if lx.accept('"') {
				/// Peek ahead: the string can contain " and "", including at the
				/// end: """str"""""
				/// 6 or more at the end, however, is an error.
				if lx.peek() == '"' {
					/// Check if we already lexed 5 's; if so we have 6 now, and
					/// that's just too many man!
					if strings.HasSuffix(lx.current(), `"""""`) {
						return lx.errorf(`unexpected '""""""'`)
					}
					lx.backup()
					lx.backup()
					return lexMultilineString
				}

				lx.backup() /// backup: don't include the """ in the item.
				lx.backup()
				lx.backup()
				lx.emit(itemMultilineString)
				lx.next() /// Read over ''' again and discard it.
				lx.next()
				lx.next()
				lx.ignore()
				return lx.pop()
			}
			lx.backup()
		}
		return lexMultilineString
	}
}

// lexRawString consumes a raw string. Nothing can be escaped in such a string.
// It assumes that the beginning "'" has already been consumed and ignored.
func lexRawString(lx *lexer) stateFn {
	r := lx.next()
	switch {
	default:
		return lexRawString
	case r == eof:
		return lx.errorf(`unexpected EOF; expected "'"`)
	case isNL(r):
		return lx.errorPrevLine(errLexStringNL{})
	case r == '\'':
		lx.backup()
		lx.emit(itemRawString)
		lx.next()
		lx.ignore()
		return lx.pop()
	}
}

// lexMultilineRawString consumes a raw string. Nothing can be escaped in such
// a string. It assumes that the beginning "'''" has already been consumed and
// ignored.
func lexMultilineRawString(lx *lexer) stateFn {
	r := lx.next()
	switch r {
	default:
		return lexMultilineRawString
	case eof:
		return lx.errorf(`unexpected EOF; expected "'''"`)
	case '\'':
		/// Found ' → try to read two more ''.
		if lx.accept('\'') {
			if lx.accept('\'') {
				/// Peek ahead: the string can contain ' and '', including at the
				/// end: '''str'''''
				/// 6 or more at the end, however, is an error.
				if lx.peek() == '\'' {
					/// Check if we already lexed 5 's; if so we have 6 now, and
					/// that's just too many man!
					if strings.HasSuffix(lx.current(), "'''''") {
						return lx.errorf(`unexpected "''''''"`)
					}
					lx.backup()
					lx.backup()
					return lexMultilineRawString
				}

				lx.backup() /// backup: don't include the ''' in the item.
				lx.backup()
				lx.backup()
				lx.emit(itemRawMultilineString)
				lx.next() /// Read over ''' again and discard it.
				lx.next()
				lx.next()
				lx.ignore()
				return lx.pop()
			}
			lx.backup()
		}
		return lexMultilineRawString
	}
}

// lexMultilineStringEscape consumes an escaped character. It assumes that the
// preceding '\\' has already been consumed.
func lexMultilineStringEscape(lx *lexer) stateFn {
	// Handle the special case first:
	if isNL(lx.next()) {
		return lexMultilineString
	}
	lx.backup()
	lx.push(lexMultilineString)
	return lexStringEscape(lx)
}

func lexStringEscape(lx *lexer) stateFn {
	r := lx.next()
	switch r {
	case 'b':
		fallthrough
	case 't':
		fallthrough
	case 'n':
		fallthrough
	case 'f':
		fallthrough
	case 'r':
		fallthrough
	case '"':
		fallthrough
	case ' ', '\t':
		// Inside """ .. """ strings you can use \ to escape newlines, and any
		// amount of whitespace can be between the \ and \n.
		fallthrough
	case '\\':
		return lx.pop()
	case 'u':
		return lexShortUnicodeEscape
	case 'U':
		return lexLongUnicodeEscape
	}
	return lx.error(errLexEscape{r})
}

func lexShortUnicodeEscape(lx *lexer) stateFn {
	var r rune
	for i := 0; i < 4; i++ {
		r = lx.next()
		if !isHexadecimal(r) {
			return lx.errorf(
				`expected four hexadecimal digits after '\u', but got %q instead`,
				lx.current())
		}
	}
	return lx.pop()
}

func lexLongUnicodeEscape(lx *lexer) stateFn {
	var r rune
	for i := 0; i < 8; i++ {
		r = lx.next()
		if !isHexadecimal(r) {
			return lx.errorf(
				`expected eight hexadecimal digits after '\U', but got %q instead`,
				lx.current())
		}
	}
	return lx.pop()
}

// lexNumberOrDateStart processes the first character of a value which begins
// with a digit. It exists to catch values starting with '0', so that
// lexBaseNumberOrDate can differentiate base prefixed integers from other
// types.
func lexNumberOrDateStart(lx *lexer) stateFn {
	r := lx.next()
	switch r {
	case '0':
		return lexBaseNumberOrDate
	}

	if !isDigit(r) {
		// The only way to reach this state is if the value starts
		// with a digit, so specifically treat anything else as an
		// error.
		return lx.errorf("expected a digit but got %q", r)
	}

	return lexNumberOrDate
}

// lexNumberOrDate consumes either an integer, float or datetime.
func lexNumberOrDate(lx *lexer) stateFn {
	r := lx.next()
	if isDigit(r) {
		return lexNumberOrDate
	}
	switch r {
	case '-', ':':
		return lexDatetime
	case '_':
		return lexDecimalNumber
	case '.', 'e', 'E':
		return lexFloat
	}

	lx.backup()
	lx.emit(itemInteger)
	return lx.pop()
}

// lexDatetime consumes a Datetime, to a first approximation.
// The parser validates that it matches one of the accepted formats.
func lexDatetime(lx *lexer) stateFn {
	r := lx.next()
	if isDigit(r) {
		return lexDatetime
	}
	switch r {
	case '-', ':', 'T', 't', ' ', '.', 'Z', 'z', '+':
		return lexDatetime
	}

	lx.backup()
	lx.emitTrim(itemDatetime)
	return lx.pop()
}

// lexHexInteger consumes a hexadecimal integer after seeing the '0x' prefix.
func lexHexInteger(lx *lexer) stateFn {
	r := lx.next()
	if isHexadecimal(r) {
		return lexHexInteger
	}
	switch r {
	case '_':
		return lexHexInteger
	}

	lx.backup()
	lx.emit(itemInteger)
	return lx.pop()
}

// lexOctalInteger consumes an octal integer after seeing the '0o' prefix.
func lexOctalInteger(lx *lexer) stateFn {
	r := lx.next()
	if isOctal(r) {
		return lexOctalInteger
	}
	switch r {
	case '_':
		return lexOctalInteger
	}

	lx.backup()
	lx.emit(itemInteger)
	return lx.pop()
}

// lexBinaryInteger consumes a binary integer after seeing the '0b' prefix.
func lexBinaryInteger(lx *lexer) stateFn {
	r := lx.next()
	if isBinary(r) {
		return lexBinaryInteger
	}
	switch r {
	case '_':
		return lexBinaryInteger
	}

	lx.backup()
	lx.emit(itemInteger)
	return lx.pop()
}

// lexDecimalNumber consumes a decimal float or integer.
func lexDecimalNumber(lx *lexer) stateFn {
	r := lx.next()
	if isDigit(r) {
		return lexDecimalNumber
	}
	switch r {
	case '.', 'e', 'E':
		return lexFloat
	case '_':
		return lexDecimalNumber
	}

	lx.backup()
	lx.emit(itemInteger)
	return lx.pop()
}

// lexDecimalNumber consumes the first digit of a number beginning with a sign.
// It assumes the sign has already been consumed. Values which start with a sign
// are only allowed to be decimal integers or floats.
//
// The special "nan" and "inf" values are also recognized.
func lexDecimalNumberStart(lx *lexer) stateFn {
	r := lx.next()

	// Special error cases to give users better error messages
	switch r {
	case 'i':
		if !lx.accept('n') || !lx.accept('f') {
			return lx.errorf("invalid float: '%s'", lx.current())
		}
		lx.emit(itemFloat)
		return lx.pop()
	case 'n':
		if !lx.accept('a') || !lx.accept('n') {
			return lx.errorf("invalid float: '%s'", lx.current())
		}
		lx.emit(itemFloat)
		return lx.pop()
	case '0':
		p := lx.peek()
		switch p {
		case 'b', 'o', 'x':
			return lx.errorf("cannot use sign with non-decimal numbers: '%s%c'", lx.current(), p)
		}
	case '.':
		return lx.errorf("floats must start with a digit, not '.'")
	}

	if isDigit(r) {
		return lexDecimalNumber
	}

	return lx.errorf("expected a digit but got %q", r)
}

// lexBaseNumberOrDate differentiates between the possible values which
// start with '0'. It assumes that before reaching this state, the initial '0'
// has been consumed.
func lexBaseNumberOrDate(lx *lexer) stateFn {
	r := lx.next()
	// Note: All datetimes start with at least two digits, so we don't
	// handle date characters (':', '-', etc.) here.
	if isDigit(r) {
		return lexNumberOrDate
	}
	switch r {
	case '_':
		// Can only be decimal, because there can't be an underscore
		// between the '0' and the base designator, and dates can't
		// contain underscores.
		return lexDecimalNumber
	case '.', 'e', 'E':
		return lexFloat
	case 'b':
		r = lx.peek()
		if !isBinary(r) {
			lx.errorf("not a binary number: '%s%c'", lx.current(), r)
		}
		return lexBinaryInteger
	case 'o':
		r = lx.peek()
		if !isOctal(r) {
			lx.errorf("not an octal number: '%s%c'", lx.current(), r)
		}
		return lexOctalInteger
	case 'x':
		r = lx.peek()
		if !isHexadecimal(r) {
			lx.errorf("not a hexidecimal number: '%s%c'", lx.current(), r)
		}
		return lexHexInteger
	}

	lx.backup()
	lx.emit(itemInteger)
	return lx.pop()
}

// lexFloat consumes the elements of a float. It allows any sequence of
// float-like characters, so floats emitted by the lexer are only a first
// approximation and must be validated by the parser.
func lexFloat(lx *lexer) stateFn {
	r := lx.next()
	if isDigit(r) {
		return lexFloat
	}
	switch r {
	case '_', '.', '-', '+', 'e', 'E':
		return lexFloat
	}

	lx.backup()
	lx.emit(itemFloat)
	return lx.pop()
}

// lexBool consumes a bool string: 'true' or 'false.
func lexBool(lx *lexer) stateFn {
	var rs []rune
	for {
		r := lx.next()
		if !unicode.IsLetter(r) {
			lx.backup()
			break
		}
		rs = append(rs, r)
	}
	s := string(rs)
	switch s {
	case "true", "false":
		lx.emit(itemBool)
		return lx.pop()
	}
	return lx.errorf("expected value but found %q instead", s)
}

// lexCommentStart begins the lexing of a comment. It will emit
// itemCommentStart and consume no characters, passing control to lexComment.
func lexCommentStart(lx *lexer) stateFn {
	lx.ignore()
	lx.emit(itemCommentStart)
	return lexComment
}

// lexComment lexes an entire comment. It assumes that '#' has been consumed.
// It will consume *up to* the first newline character, and pass control
// back to the last state on the stack.
func lexComment(lx *lexer) stateFn {
	switch r := lx.next(); {
	case isNL(r) || r == eof:
		lx.backup()
		lx.emit(itemText)
		return lx.pop()
	default:
		return lexComment
	}
}

// lexSkip ignores all slurped input and moves on to the next state.
func lexSkip(lx *lexer, nextState stateFn) stateFn {
	lx.ignore()
	return nextState
}

func (s stateFn) String() string {
	name := runtime.FuncForPC(reflect.ValueOf(s).Pointer()).Name()
	if i := strings.LastIndexByte(name, '.'); i > -1 {
		name = name[i+1:]
	}
	if s == nil {
		name = "<nil>"
	}
	return name + "()"
}

func (itype itemType) String() string {
	switch itype {
	case itemError:
		return "Error"
	case itemNIL:
		return "NIL"
	case itemEOF:
		return "EOF"
	case itemText:
		return "Text"
	case itemString, itemRawString, itemMultilineString, itemRawMultilineString:
		return "String"
	case itemBool:
		return "Bool"
	case itemInteger:
		return "Integer"
	case itemFloat:
		return "Float"
	case itemDatetime:
		return "DateTime"
	case itemTableStart:
		return "TableStart"
	case itemTableEnd:
		return "TableEnd"
	case itemKeyStart:
		return "KeyStart"
	case itemKeyEnd:
		return "KeyEnd"
	case itemArray:
		return "Array"
	case itemArrayEnd:
		return "ArrayEnd"
	case itemCommentStart:
		return "CommentStart"
	case itemInlineTableStart:
		return "InlineTableStart"
	case itemInlineTableEnd:
		return "InlineTableEnd"
	}
	panic(fmt.Sprintf("BUG: Unknown type '%d'.", int(itype)))
}

func (item item) String() string {
	return fmt.Sprintf("(%s, %s)", item.typ.String(), item.val)
}

func isWhitespace(r rune) bool { return r == '\t' || r == ' ' }
func isNL(r rune) bool         { return r == '\n' || r == '\r' }
func isControl(r rune) bool { // Control characters except \t, \r, \n
	switch r {
	case '\t', '\r', '\n':
		return false
	default:
		return (r >= 0x00 && r <= 0x1f) || r == 0x7f
	}
}
func isDigit(r rune) bool  { return r >= '0' && r <= '9' }
func isBinary(r rune) bool { return r == '0' || r == '1' }
func isOctal(r rune) bool  { return r >= '0' && r <= '7' }
func isHexadecimal(r rune) bool {
	return (r >= '0' && r <= '9') || (r >= 'a' && r <= 'f') || (r >= 'A' && r <= 'F')
}
func isBareKeyChar(r rune) bool {
	return (r >= 'A' && r <= 'Z') ||
		(r >= 'a' && r <= 'z') ||
		(r >= '0' && r <= '9') ||
		r == '_' || r == '-'
}