Source

mh-e / mh-seq.el

   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
1225
1226
1227
1228
1229
1230
1231
1232
1233
1234
1235
1236
1237
1238
1239
1240
1241
1242
1243
1244
1245
1246
1247
1248
1249
1250
1251
1252
1253
1254
1255
1256
1257
1258
1259
1260
1261
1262
1263
1264
1265
1266
1267
1268
1269
1270
1271
1272
1273
1274
1275
1276
1277
1278
1279
1280
1281
1282
1283
1284
1285
1286
1287
1288
1289
1290
1291
1292
1293
1294
1295
1296
1297
1298
1299
1300
1301
1302
1303
1304
1305
1306
1307
1308
1309
1310
1311
1312
1313
1314
1315
1316
1317
1318
;;; mh-seq.el --- MH-E sequences support

;; Copyright (C) 1993, 1995, 2001, 2002 Free Software Foundation, Inc.

;; Author: Bill Wohler <wohler@newt.com>
;; Maintainer: Bill Wohler <wohler@newt.com>
;; Keywords: mail
;; See: mh-e.el

;; This file is part of GNU Emacs.

;; GNU Emacs is free software; you can redistribute it and/or modify
;; it under the terms of the GNU General Public License as published by
;; the Free Software Foundation; either version 2, or (at your option)
;; any later version.

;; GNU Emacs is distributed in the hope that it will be useful,
;; but WITHOUT ANY WARRANTY; without even the implied warranty of
;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
;; GNU General Public License for more details.

;; You should have received a copy of the GNU General Public License
;; along with GNU Emacs; see the file COPYING.  If not, write to the
;; Free Software Foundation, Inc., 59 Temple Place - Suite 330,
;; Boston, MA 02111-1307, USA.

;;; Commentary:
;;
;;   This tries to implement the algorithm described at:
;;     http://www.jwz.org/doc/threading.html
;;   It is also a start to implementing the IMAP Threading extension RFC. The
;;   implementation lacks the reference and subject canonicalization of the
;;   RFC.
;;
;;   In the presentation buffer, children messages are shown indented with
;;   either [ ] or < > around them. Square brackets ([ ]) denote that the
;;   algorithm can point out some headers which when taken together implies
;;   that the unindented message is an ancestor of the indented message. If
;;   no such proof exists then angles (< >) are used.
;;
;;   Some issues and problems are as follows:
;;
;;    (1) Scan truncates the fields at length 512. So longer references:
;;        headers get mutilated. The same kind of MH format string works when
;;        composing messages. Is there a way to avoid this? My scan command
;;        is as follows:
;;          scan +folder -width 10000 \
;;               -format "%(msg)\n%{message-id}\n%{references}\n%{subject}\n"
;;        I would really appreciate it if someone would help me with this.
;;
;;    (2) Implement heuristics to recognize message identifiers in
;;        In-Reply-To: header. Right now it just assumes that the last text
;;        between angles (< and >) is the message identifier. There is the
;;        chance that this will incorrectly use an email address like a
;;        message identifier.
;;
;;    (3) Error checking of found message identifiers should be done.
;;
;;    (4) Since this breaks the assumption that message indices increase as
;;        one goes down the buffer, the binary search based mh-goto-msg
;;        doesn't work. I have a simpler replacement which may be less
;;        efficient.
;;
;;    (5) Better canonicalizing for message identifier and subject strings.
;;

;; Internal support for MH-E package.

;;; Change Log:

;; $Id$

;;; Code:

(require 'cl)
(require 'mh-e)

;; Shush the byte-compiler
(defvar tool-bar-mode)

;;; Data structures (used in message threading)...
(defstruct (mh-thread-message (:conc-name mh-message-)
                              (:constructor mh-thread-make-message))
  (id nil)
  (references ())
  (subject "")
  (subject-re-p nil))

(defstruct (mh-thread-container (:conc-name mh-container-)
                                (:constructor mh-thread-make-container))
  message parent children
  (real-child-p t))


;;; Internal variables:
(defvar mh-last-seq-used nil
  "Name of seq to which a msg was last added.")

(defvar mh-non-seq-mode-line-annotation nil
  "Saved value of `mh-mode-line-annotation' when narrowed to a seq.")

;;; Maps and hashes...
(defvar mh-thread-id-hash nil
  "Hashtable used to canonicalize message identifiers.")
(defvar mh-thread-subject-hash nil
  "Hashtable used to canonicalize subject strings.")
(defvar mh-thread-id-table nil
  "Thread ID table maps from message identifiers to message containers.")
(defvar mh-thread-id-index-map nil
  "Table to look up message index number from message identifier.")
(defvar mh-thread-index-id-map nil
  "Table to look up message identifier from message index.")
(defvar mh-thread-scan-line-map nil
  "Map of message index to various parts of the scan line.")
(defvar mh-thread-old-scan-line-map nil
  "Old map of message index to various parts of the scan line.
This is the original map that is stored when the folder is narrowed.")
(defvar mh-thread-subject-container-hash nil
  "Hashtable used to group messages by subject.")
(defvar mh-thread-duplicates nil
  "Hashtable used to associate messages with the same message identifier.")
(defvar mh-thread-history ()
  "Variable to remember the transformations to the thread tree.
When new messages are added, these transformations are rewound, then the
links are added from the newly seen messages. Finally the transformations are
redone to get the new thread tree. This makes incremental threading easier.")
(defvar mh-thread-body-width nil
  "Width of scan substring that contains subject and body of message.")

(make-variable-buffer-local 'mh-thread-id-hash)
(make-variable-buffer-local 'mh-thread-subject-hash)
(make-variable-buffer-local 'mh-thread-id-table)
(make-variable-buffer-local 'mh-thread-id-index-map)
(make-variable-buffer-local 'mh-thread-index-id-map)
(make-variable-buffer-local 'mh-thread-scan-line-map)
(make-variable-buffer-local 'mh-thread-old-scan-line-map)
(make-variable-buffer-local 'mh-thread-subject-container-hash)
(make-variable-buffer-local 'mh-thread-duplicates)
(make-variable-buffer-local 'mh-thread-history)

;;;###mh-autoload
(defun mh-delete-seq (sequence)
  "Delete the SEQUENCE."
  (interactive (list (mh-read-seq-default "Delete" t)))
  (let ((msg-list (mh-seq-to-msgs sequence)))
    (mh-undefine-sequence sequence '("all"))
    (mh-delete-seq-locally sequence)
    (mh-iterate-on-messages-in-region msg (point-min) (point-max)
      (when (and (member msg msg-list) (not (mh-seq-containing-msg msg nil)))
        (mh-notate nil ?  (1+ mh-cmd-note))))))

;; Avoid compiler warnings
(defvar view-exit-action)

;;;###mh-autoload
(defun mh-list-sequences ()
  "List the sequences defined in the folder being visited."
  (interactive)
  (let ((folder mh-current-folder)
        (temp-buffer mh-sequences-buffer)
        (seq-list mh-seq-list)
        (max-len 0))
    (with-output-to-temp-buffer temp-buffer
      (save-excursion
        (set-buffer temp-buffer)
        (erase-buffer)
        (message "Listing sequences ...")
        (insert "Sequences in folder " folder ":\n")
        (let ((seq-list seq-list))
          (while seq-list
            (setq max-len
                  (max (length (symbol-name (mh-seq-name (pop seq-list))))
                       max-len)))
          (setq max-len (+ 2 max-len)))
        (while seq-list
          (let ((name (mh-seq-name (car seq-list)))
                (sorted-seq-msgs
                 (mh-coalesce-msg-list
                  (sort (copy-sequence (mh-seq-msgs (car seq-list))) '<)))
                name-spec)
            (insert (setq name-spec (format (format "%%%ss:" max-len) name)))
            (while sorted-seq-msgs
              (let ((next-element (format " %s" (pop sorted-seq-msgs))))
                (when (>= (+ (current-column) (length next-element))
                          (window-width))
                  (insert "\n")
                  (insert (format (format "%%%ss" (length name-spec)) "")))
                (insert next-element)))
            (insert "\n"))
          (setq seq-list (cdr seq-list)))
        (goto-char (point-min))
        (view-mode 1)
        (setq view-exit-action 'kill-buffer)
        (message "Listing sequences...done")))))

;;;###mh-autoload
(defun mh-msg-is-in-seq (message)
  "Display the sequences that contain MESSAGE (default: current message)."
  (interactive (list (mh-get-msg-num t)))
  (let* ((dest-folder (loop for seq in mh-refile-list
                            when (member message (cdr seq)) return (car seq)))
         (deleted-flag (unless dest-folder (member message mh-delete-list))))
    (message "Message %d%s is in sequences: %s"
             message
             (cond (dest-folder (format " (to be refiled to %s)" dest-folder))
                   (deleted-flag (format " (to be deleted)"))
                   (t ""))
             (mapconcat 'concat
                        (mh-list-to-string (mh-seq-containing-msg message t))
                        " "))))

;;;###mh-autoload
(defun mh-narrow-to-seq (sequence)
  "Restrict display of this folder to just messages in SEQUENCE.
Use \\<mh-folder-mode-map>\\[mh-widen] to undo this command."
  (interactive (list (mh-read-seq "Narrow to" t)))
  (with-mh-folder-updating (t)
    (cond ((mh-seq-to-msgs sequence)
           (mh-widen)
           (mh-remove-all-notation)
           (let ((eob (point-max))
                 (msg-at-cursor (mh-get-msg-num nil)))
             (setq mh-thread-old-scan-line-map mh-thread-scan-line-map)
             (setq mh-thread-scan-line-map (make-hash-table :test #'eql))
             (mh-copy-seq-to-eob sequence)
             (narrow-to-region eob (point-max))
             (mh-notate-user-sequences)
             (mh-notate-deleted-and-refiled)
             (mh-notate-cur)
             (when msg-at-cursor (mh-goto-msg msg-at-cursor t t))
             (make-variable-buffer-local 'mh-non-seq-mode-line-annotation)
             (setq mh-non-seq-mode-line-annotation mh-mode-line-annotation)
             (setq mh-mode-line-annotation (symbol-name sequence))
             (mh-make-folder-mode-line)
             (mh-recenter nil)
             (if (and (boundp 'tool-bar-mode) tool-bar-mode)
                 (set (make-local-variable 'tool-bar-map)
                      mh-folder-seq-tool-bar-map))
             (setq mh-narrowed-to-seq sequence)
             (push 'widen mh-view-ops)))
          (t
           (error "No messages in sequence `%s'" (symbol-name sequence))))))

;;;###mh-autoload
(defun mh-put-msg-in-seq (msg-or-seq sequence)
  "Add MSG-OR-SEQ (default: displayed message) to SEQUENCE.
If optional prefix argument provided, then prompt for the message sequence.
If variable `transient-mark-mode' is non-nil and the mark is active, then
the selected region is added to the sequence."
  (interactive (list (cond
                      ((mh-mark-active-p t)
                       (cons (region-beginning) (region-end)))
                      (current-prefix-arg
                       (mh-read-seq-default "Add messages from" t))
                      (t
                       (cons (line-beginning-position) (line-end-position))))
                     (mh-read-seq-default "Add to" nil)))
  (let ((internal-seq-flag (mh-internal-seq sequence))
        msg-list)
    (cond ((and (consp msg-or-seq)
                (numberp (car msg-or-seq)) (numberp (cdr msg-or-seq)))
           (mh-iterate-on-messages-in-region m (car msg-or-seq) (cdr msg-or-seq)
             (push m msg-list)
             (unless internal-seq-flag
               (mh-notate nil mh-note-seq (1+ mh-cmd-note))))
           (mh-add-msgs-to-seq msg-list sequence internal-seq-flag t))
          ((or (numberp msg-or-seq) (listp msg-or-seq))
           (when (numberp msg-or-seq)
             (setq msg-or-seq (list msg-or-seq)))
           (mh-add-msgs-to-seq msg-or-seq sequence internal-seq-flag))
          (t (mh-add-msgs-to-seq (mh-seq-to-msgs msg-or-seq) sequence)))
    (if (not internal-seq-flag)
        (setq mh-last-seq-used sequence))))

(defun mh-valid-view-change-operation-p (op)
  "Check if the view change operation can be performed.
OP is one of 'widen and 'unthread."
  (cond ((eq (car mh-view-ops) op)
         (pop mh-view-ops))
        (t nil)))

;;;###mh-autoload
(defun mh-widen ()
  "Remove restrictions from current folder, thereby showing all messages."
  (interactive)
  (let ((msg (mh-get-msg-num nil)))
    (when mh-narrowed-to-seq
      (cond ((mh-valid-view-change-operation-p 'widen) nil)
            ((memq 'widen mh-view-ops)
             (while (not (eq (car mh-view-ops) 'widen))
               (setq mh-view-ops (cdr mh-view-ops)))
             (pop mh-view-ops))
            (t (error "Widening is not applicable")))
      (when (memq 'unthread mh-view-ops)
        (setq mh-thread-scan-line-map mh-thread-old-scan-line-map))
      (with-mh-folder-updating (t)
        (delete-region (point-min) (point-max))
        (widen)
        (setq mh-mode-line-annotation mh-non-seq-mode-line-annotation)
        (mh-make-folder-mode-line))
      (if msg
          (mh-goto-msg msg t t))
      (mh-notate-deleted-and-refiled)
      (mh-notate-user-sequences)
      (mh-notate-cur)
      (mh-recenter nil)))
  (if (and (boundp 'tool-bar-mode) tool-bar-mode)
      (set (make-local-variable 'tool-bar-map) mh-folder-tool-bar-map))
  (setq mh-narrowed-to-seq nil))

;; FIXME?  We may want to clear all notations and add one for current-message
;;         and process user sequences.
(defun mh-notate-deleted-and-refiled ()
  "Notate messages marked for deletion or refiling.
Messages to be deleted are given by `mh-delete-list' while messages to be
refiled are present in `mh-refile-list'."
  (let ((refiled-hash (make-hash-table))
        (deleted-hash (make-hash-table)))
    (dolist (msg mh-delete-list)
      (setf (gethash msg deleted-hash) t))
    (dolist (dest-msg-list mh-refile-list)
      (dolist (msg (cdr dest-msg-list))
        (setf (gethash msg refiled-hash) t)))
    (mh-iterate-on-messages-in-region msg (point-min) (point-max)
      (cond ((gethash msg refiled-hash)
             (mh-notate nil mh-note-refiled mh-cmd-note))
            ((gethash msg deleted-hash)
             (mh-notate nil mh-note-deleted mh-cmd-note))))))



;;; Commands to manipulate sequences.  Sequences are stored in an alist
;;; of the form:
;;;     ((seq-name msgs ...) (seq-name msgs ...) ...)

(defun mh-read-seq-default (prompt not-empty)
  "Read and return sequence name with default narrowed or previous sequence.
PROMPT is the prompt to use when reading. If NOT-EMPTY is non-nil then a
non-empty sequence is read."
  (mh-read-seq prompt not-empty
               (or mh-narrowed-to-seq
                   mh-last-seq-used
                   (car (mh-seq-containing-msg (mh-get-msg-num nil) nil)))))

(defun mh-read-seq (prompt not-empty &optional default)
  "Read and return a sequence name.
Prompt with PROMPT, raise an error if the sequence is empty and the NOT-EMPTY
flag is non-nil, and supply an optional DEFAULT sequence. A reply of '%'
defaults to the first sequence containing the current message."
  (let* ((input (completing-read (format "%s %s %s" prompt "sequence:"
                                         (if default
                                             (format "[%s] " default)
                                           ""))
                                 (mh-seq-names mh-seq-list)))
         (seq (cond ((equal input "%")
                     (car (mh-seq-containing-msg (mh-get-msg-num t) nil)))
                    ((equal input "") default)
                    (t (intern input))))
         (msgs (mh-seq-to-msgs seq)))
    (if (and (null msgs) not-empty)
        (error "No messages in sequence `%s'" seq))
    seq))

(defun mh-seq-names (seq-list)
  "Return an alist containing the names of the SEQ-LIST."
  (mapcar (lambda (entry) (list (symbol-name (mh-seq-name entry))))
          seq-list))

;;;###mh-autoload
(defun mh-rename-seq (sequence new-name)
  "Rename SEQUENCE to have NEW-NAME."
  (interactive (list (mh-read-seq "Old" t)
                     (intern (read-string "New sequence name: "))))
  (let ((old-seq (mh-find-seq sequence)))
    (or old-seq
        (error "Sequence %s does not exist" sequence))
    ;; create new sequence first, since it might raise an error.
    (mh-define-sequence new-name (mh-seq-msgs old-seq))
    (mh-undefine-sequence sequence (mh-seq-msgs old-seq))
    (rplaca old-seq new-name)))

;;;###mh-autoload
(defun mh-map-to-seq-msgs (func seq &rest args)
  "Invoke the FUNC at each message in the SEQ.
SEQ can either be a list of messages or a MH sequence. The remaining ARGS are
passed as arguments to FUNC."
  (save-excursion
    (let ((msgs (if (listp seq) seq (mh-seq-to-msgs seq))))
      (while msgs
        (if (mh-goto-msg (car msgs) t t)
            (apply func (car msgs) args))
        (setq msgs (cdr msgs))))))

;;;###mh-autoload
(defun mh-notate-seq (seq notation offset)
  "Mark the scan listing.
All messages in SEQ are marked with NOTATION at OFFSET from the beginning of
the line."
  (let ((msg-list (mh-seq-to-msgs seq)))
    (mh-iterate-on-messages-in-region msg (point-min) (point-max)
      (when (member msg msg-list)
        (mh-notate nil notation offset)))))

;;;###mh-autoload
(defun mh-notate-cur ()
  "Mark the MH sequence cur.
In addition to notating the current message with `mh-note-cur' the function
uses `overlay-arrow-position' to put a marker in the fringe."
  (let ((cur (car (mh-seq-to-msgs 'cur))))
    (when (and cur (mh-goto-msg cur t t))
      (mh-notate nil mh-note-cur mh-cmd-note)
      (beginning-of-line)
      (setq mh-arrow-marker (set-marker mh-arrow-marker (point)))
      (setq overlay-arrow-position mh-arrow-marker))))

;;;###mh-autoload
(defun mh-add-to-sequence (seq msgs)
  "The sequence SEQ is augmented with the messages in MSGS."
  ;; Add to a SEQUENCE each message the list of MSGS.
  (if (not (mh-folder-name-p seq))
      (if msgs
          (apply 'mh-exec-cmd "mark" mh-current-folder "-add"
                 "-sequence" (symbol-name seq)
                 (mh-coalesce-msg-list msgs)))))

;; This has a tricky bug. mh-map-to-seq-msgs uses mh-goto-msg, which assumes
;; that the folder buffer is sorted. However in this case that assumption
;; doesn't hold. So we will do this the dumb way.
;(defun mh-copy-seq-to-point (seq location)
;  ;; Copy the scan listing of the messages in SEQUENCE to after the point
;  ;; LOCATION in the current buffer.
;  (mh-map-to-seq-msgs 'mh-copy-line-to-point seq location))

(defun mh-copy-seq-to-eob (seq)
  "Copy SEQ to the end of the buffer."
  ;; It is quite involved to write something which will work at any place in
  ;; the buffer, so we will write something which works only at the end of
  ;; the buffer. If we ever need to insert sequences in the middle of the
  ;; buffer, this will need to be fixed.
  (save-excursion
    (let* ((msgs (mh-seq-to-msgs seq))
           (coalesced-msgs (mh-coalesce-msg-list msgs)))
      (goto-char (point-max))
      (save-restriction
        (narrow-to-region (point) (point))
        (mh-regenerate-headers coalesced-msgs t)
        (cond ((memq 'unthread mh-view-ops)
               ;; Populate restricted scan-line map
               (goto-char (point-min))
               (while (not (eobp))
                 (let ((msg (mh-get-msg-num nil)))
                   (when (numberp msg)
                     (setf (gethash msg mh-thread-scan-line-map)
                           (mh-thread-parse-scan-line))))
                 (forward-line))
               ;; Remove scan lines and read results from pre-computed tree
               (delete-region (point-min) (point-max))
               (let ((thread-tree (mh-thread-generate mh-current-folder ()))
                     (mh-thread-body-width
                      (- (window-width) mh-cmd-note
                         (1- mh-scan-field-subject-start-offset)))
                     (mh-thread-last-ancestor nil))
                 (mh-thread-generate-scan-lines thread-tree -2)))
              (mh-index-data
               (mh-index-insert-folder-headers)))))))

(defun mh-copy-line-to-point (msg location)
  "Copy current message line to a specific location.
The argument MSG is not used. The message in the current line is copied to
LOCATION."
  ;; msg is not used?
  ;; Copy the current line to the LOCATION in the current buffer.
  (beginning-of-line)
  (save-excursion
    (let ((beginning-of-line (point))
          end)
      (forward-line 1)
      (setq end (point))
      (goto-char location)
      (insert-buffer-substring (current-buffer) beginning-of-line end))))

;;;###mh-autoload
(defmacro mh-iterate-on-messages-in-region (var begin end &rest body)
  "Iterate over region.
VAR is bound to the message on the current line as we loop starting from BEGIN
till END. In each step BODY is executed.

If VAR is nil then the loop is executed without any binding."
  (unless (symbolp var)
    (error "Can not bind the non-symbol %s" var))
  (let ((binding-needed-flag var))
    `(save-excursion
       (goto-char ,begin)
       (while (and (<= (point) ,end) (not (eobp)))
         (when (looking-at mh-scan-valid-regexp)
           (let ,(if binding-needed-flag `((,var (mh-get-msg-num t))) ())
             ,@body))
         (forward-line 1)))))

;;;###mh-autoload
(defun mh-region-to-msg-list (begin end)
  "Return a list of messages within the region between BEGIN and END."
  ;; If end is end of buffer back up one position
  (setq end (if (equal end (point-max)) (1- end) end))
  (let ((result))
    (mh-iterate-on-messages-in-region index begin end
      (when (numberp index) (push index result)))
    result))



;;; Commands to handle new 'subject sequence.
;;; Or "Poor man's threading" by psg.

(defun mh-subject-to-sequence (all)
  "Put all following messages with same subject in sequence 'subject.
If arg ALL is t, move to beginning of folder buffer to collect all messages.
If arg ALL is nil, collect only messages fron current one on forward.

Return number of messages put in the sequence:

 nil -> there was no subject line.
 0   -> there were no later messages with the same subject (sequence not made)
 >1  -> the total number of messages including current one."
  (if (not (eq major-mode 'mh-folder-mode))
      (error "Not in a folder buffer"))
  (save-excursion
    (beginning-of-line)
    (if (or (not (looking-at mh-scan-subject-regexp))
            (not (match-string 3))
            (string-equal "" (match-string 3)))
        (progn (message "No subject line.")
               nil)
      (let ((subject (match-string-no-properties 3))
            (list))
        (if (> (length subject) 41)
            (setq subject (substring subject 0 41)))
        (save-excursion
          (if all
              (goto-char (point-min)))
          (while (re-search-forward mh-scan-subject-regexp nil t)
            (let ((this-subject (match-string-no-properties 3)))
              (if (> (length this-subject) 41)
                  (setq this-subject (substring this-subject 0 41)))
              (if (string-equal this-subject subject)
                  (setq list (cons (mh-get-msg-num t) list))))))
        (cond
         (list
          ;; If we created a new sequence, add the initial message to it too.
          (if (not (member (mh-get-msg-num t) list))
              (setq list (cons (mh-get-msg-num t) list)))
          (if (member '("subject") (mh-seq-names mh-seq-list))
              (mh-delete-seq 'subject))
          ;; sort the result into a sequence
          (let ((sorted-list (sort (copy-sequence list) 'mh-lessp)))
            (while sorted-list
              (mh-add-msgs-to-seq (car sorted-list) 'subject nil)
              (setq sorted-list (cdr sorted-list)))
            (safe-length list)))
         (t
          0))))))

;;;###mh-autoload
(defun mh-narrow-to-subject ()
  "Narrow to a sequence containing all following messages with same subject."
  (interactive)
  (let ((num (mh-get-msg-num nil))
        (count (mh-subject-to-sequence t)))
    (cond
     ((not count)                       ; No subject line, delete msg anyway
      nil)
     ((= 0 count)                       ; No other msgs, delete msg anyway.
      (message "No other messages with same Subject following this one.")
      nil)
     (t                                 ; We have a subject sequence.
      (message "Found %d messages for subject sequence." count)
      (mh-narrow-to-seq 'subject)
      (if (numberp num)
          (mh-goto-msg num t t))))))

;;;###mh-autoload
(defun mh-delete-subject ()
  "Mark all following messages with same subject to be deleted.
This puts the messages in a sequence named subject.  You can undo the last
deletion marks using `mh-undo' with a prefix argument and then specifying the
subject sequence."
  (interactive)
  (let ((count (mh-subject-to-sequence nil)))
    (cond
     ((not count)                       ; No subject line, delete msg anyway
      (mh-delete-msg (mh-get-msg-num t)))
     ((= 0 count)                       ; No other msgs, delete msg anyway.
      (message "No other messages with same Subject following this one.")
      (mh-delete-msg (mh-get-msg-num t)))
     (t                                 ; We have a subject sequence.
      (message "Marked %d messages for deletion" count)
      (mh-delete-msg 'subject)))))

;;;###mh-autoload
(defun mh-delete-subject-or-thread ()
  "Mark messages for deletion intelligently.
If the folder is threaded then `mh-thread-delete' is used to mark the current
message and all its descendants for deletion. Otherwise `mh-delete-subject' is
used to mark the current message and all messages following it with the same
subject for deletion."
  (interactive)
  (if (memq 'unthread mh-view-ops)
      (mh-thread-delete)
    (mh-delete-subject)))

;;; Message threading:

(defun mh-thread-initialize ()
  "Make hash tables, otherwise clear them."
  (cond
   (mh-thread-id-hash
    (clrhash mh-thread-id-hash)
    (clrhash mh-thread-subject-hash)
    (clrhash mh-thread-id-table)
    (clrhash mh-thread-id-index-map)
    (clrhash mh-thread-index-id-map)
    (clrhash mh-thread-scan-line-map)
    (clrhash mh-thread-subject-container-hash)
    (clrhash mh-thread-duplicates)
    (setq mh-thread-history ()))
   (t (setq mh-thread-id-hash (make-hash-table :test #'equal))
      (setq mh-thread-subject-hash (make-hash-table :test #'equal))
      (setq mh-thread-id-table (make-hash-table :test #'eq))
      (setq mh-thread-id-index-map (make-hash-table :test #'eq))
      (setq mh-thread-index-id-map (make-hash-table :test #'eql))
      (setq mh-thread-scan-line-map (make-hash-table :test #'eql))
      (setq mh-thread-subject-container-hash (make-hash-table :test #'eq))
      (setq mh-thread-duplicates (make-hash-table :test #'eq))
      (setq mh-thread-history ()))))

(defsubst mh-thread-id-container (id)
  "Given ID, return the corresponding container in `mh-thread-id-table'.
If no container exists then a suitable container is created and the id-table
is updated."
  (when (not id)
    (error "1"))
  (or (gethash id mh-thread-id-table)
      (setf (gethash id mh-thread-id-table)
            (let ((message (mh-thread-make-message :id id)))
              (mh-thread-make-container :message message)))))

(defsubst mh-thread-remove-parent-link (child)
  "Remove parent link of CHILD if it exists."
  (let* ((child-container (if (mh-thread-container-p child)
                              child (mh-thread-id-container child)))
         (parent-container (mh-container-parent child-container)))
    (when parent-container
      (setf (mh-container-children parent-container)
            (loop for elem in (mh-container-children parent-container)
                  unless (eq child-container elem) collect elem))
      (setf (mh-container-parent child-container) nil))))

(defsubst mh-thread-add-link (parent child &optional at-end-p)
  "Add links so that PARENT becomes a parent of CHILD.
Doesn't make any changes if CHILD is already an ancestor of PARENT. If
optional argument AT-END-P is non-nil, the CHILD is added to the end of the
children list of PARENT."
  (let ((parent-container (cond ((null parent) nil)
                                ((mh-thread-container-p parent) parent)
                                (t (mh-thread-id-container parent))))
        (child-container (if (mh-thread-container-p child)
                             child (mh-thread-id-container child))))
    (when (and parent-container
               (not (mh-thread-ancestor-p child-container parent-container))
               (not (mh-thread-ancestor-p parent-container child-container)))
      (mh-thread-remove-parent-link child-container)
      (cond ((not at-end-p)
             (push child-container (mh-container-children parent-container)))
            ((null (mh-container-children parent-container))
             (push child-container (mh-container-children parent-container)))
            (t (let ((last-child (mh-container-children parent-container)))
                 (while (cdr last-child)
                   (setq last-child (cdr last-child)))
                 (setcdr last-child (cons child-container nil)))))
      (setf (mh-container-parent child-container) parent-container))
    (unless parent-container
      (mh-thread-remove-parent-link child-container))))

(defun mh-thread-ancestor-p (ancestor successor)
  "Return t if ANCESTOR is really an ancestor of SUCCESSOR and nil otherwise.
In the limit, the function returns t if ANCESTOR and SUCCESSOR are the same
containers."
  (block nil
    (while successor
      (when (eq ancestor successor) (return t))
      (setq successor (mh-container-parent successor)))
    nil))

(defsubst mh-thread-get-message-container (message)
  "Return container which has MESSAGE in it.
If there is no container present then a new container is allocated."
  (let* ((id (mh-message-id message))
         (container (gethash id mh-thread-id-table)))
    (cond (container (setf (mh-container-message container) message)
                     container)
          (t (setf (gethash id mh-thread-id-table)
                   (mh-thread-make-container :message message))))))

(defsubst mh-thread-get-message (id subject-re-p subject refs)
  "Return appropriate message.
Otherwise update message already present to have the proper ID, SUBJECT-RE-P,
SUBJECT and REFS fields."
  (let* ((container (gethash id mh-thread-id-table))
         (message (if container (mh-container-message container) nil)))
    (cond (message
           (setf (mh-message-subject-re-p message) subject-re-p)
           (setf (mh-message-subject message) subject)
           (setf (mh-message-id message) id)
           (setf (mh-message-references message) refs)
           message)
          (container
           (setf (mh-container-message container)
                 (mh-thread-make-message :subject subject
                                         :subject-re-p subject-re-p
                                         :id id :references refs)))
          (t (let ((message (mh-thread-make-message
                             :subject subject
                             :subject-re-p subject-re-p
                             :id id :references refs)))
               (prog1 message
                 (mh-thread-get-message-container message)))))))

(defsubst mh-thread-canonicalize-id (id)
  "Produce canonical string representation for ID.
This allows cheap string comparison with EQ."
  (or (and (equal id "") (copy-sequence ""))
      (gethash id mh-thread-id-hash)
      (setf (gethash id mh-thread-id-hash) id)))

(defsubst mh-thread-prune-subject (subject)
  "Prune leading Re:'s, Fwd:'s etc. and trailing (fwd)'s from SUBJECT.
If the result after pruning is not the empty string then it is canonicalized
so that subjects can be tested for equality with eq. This is done so that all
the messages without a subject are not put into a single thread."
  (let ((case-fold-search t)
        (subject-pruned-flag nil))
    ;; Prune subject leader
    (while (or (string-match "^[ \t]*\\(re\\|fwd?\\)\\(\\[[0-9]*\\]\\)?:[ \t]*"
                             subject)
               (string-match "^[ \t]*\\[[^\\]][ \t]*" subject))
      (setq subject-pruned-flag t)
      (setq subject (substring subject (match-end 0))))
    ;; Prune subject trailer
    (while (or (string-match "(fwd)$" subject)
               (string-match "[ \t]+$" subject))
      (setq subject-pruned-flag t)
      (setq subject (substring subject 0 (match-beginning 0))))
    ;; Canonicalize subject only if it is non-empty
    (cond ((equal subject "") (values subject subject-pruned-flag))
          (t (values
              (or (gethash subject mh-thread-subject-hash)
                  (setf (gethash subject mh-thread-subject-hash) subject))
              subject-pruned-flag)))))

(defun mh-thread-container-subject (container)
  "Return the subject of CONTAINER.
If CONTAINER is empty return the subject info of one of its children."
  (cond ((and (mh-container-message container)
              (mh-message-id (mh-container-message container)))
         (mh-message-subject (mh-container-message container)))
        (t (block nil
             (dolist (kid (mh-container-children container))
               (when (and (mh-container-message kid)
                          (mh-message-id (mh-container-message kid)))
                 (let ((kid-message (mh-container-message kid)))
                   (return (mh-message-subject kid-message)))))
             (error "This can't happen!")))))

(defun mh-thread-rewind-pruning ()
  "Restore the thread tree to its state before pruning."
  (while mh-thread-history
    (let ((action (pop mh-thread-history)))
      (cond ((eq (car action) 'DROP)
             (mh-thread-remove-parent-link (cadr action))
             (mh-thread-add-link (caddr action) (cadr action)))
            ((eq (car action) 'PROMOTE)
             (let ((node (cadr action))
                   (parent (caddr action))
                   (children (cdddr action)))
               (dolist (child children)
                 (mh-thread-remove-parent-link child)
                 (mh-thread-add-link node child))
               (mh-thread-add-link parent node)))
            ((eq (car action) 'SUBJECT)
             (let ((node (cadr action)))
               (mh-thread-remove-parent-link node)
               (setf (mh-container-real-child-p node) t)))))))

(defun mh-thread-prune-containers (roots)
  "Prune empty containers in the containers ROOTS."
  (let ((dfs-ordered-nodes ())
        (work-list roots))
    (while work-list
      (let ((node (pop work-list)))
        (dolist (child (mh-container-children node))
          (push child work-list))
        (push node dfs-ordered-nodes)))
    (while dfs-ordered-nodes
      (let ((node (pop dfs-ordered-nodes)))
        (cond ((gethash (mh-message-id (mh-container-message node))
                        mh-thread-id-index-map)
               ;; Keep it
               (setf (mh-container-children node)
                     (mh-thread-sort-containers (mh-container-children node))))
              ((and (mh-container-children node)
                    (or (null (cdr (mh-container-children node)))
                        (mh-container-parent node)))
               ;; Promote kids
               (let ((children ()))
                 (dolist (kid (mh-container-children node))
                   (mh-thread-remove-parent-link kid)
                   (mh-thread-add-link (mh-container-parent node) kid)
                   (push kid children))
                 (push `(PROMOTE ,node ,(mh-container-parent node) ,@children)
                       mh-thread-history)
                 (mh-thread-remove-parent-link node)))
              ((mh-container-children node)
               ;; Promote the first orphan to parent and add the other kids as
               ;; his children
               (setf (mh-container-children node)
                     (mh-thread-sort-containers (mh-container-children node)))
               (let ((new-parent (car (mh-container-children node)))
                     (other-kids (cdr (mh-container-children node))))
                 (mh-thread-remove-parent-link new-parent)
                 (dolist (kid other-kids)
                   (mh-thread-remove-parent-link kid)
                   (setf (mh-container-real-child-p kid) nil)
                   (mh-thread-add-link new-parent kid t))
                 (push `(PROMOTE ,node ,(mh-container-parent node)
                                 ,new-parent ,@other-kids)
                       mh-thread-history)
                 (mh-thread-remove-parent-link node)))
              (t
               ;; Drop it
               (push `(DROP ,node ,(mh-container-parent node))
                     mh-thread-history)
               (mh-thread-remove-parent-link node)))))
    (let ((results ()))
      (maphash #'(lambda (k v)
                   (declare (ignore k))
                   (when (and (null (mh-container-parent v))
                              (gethash (mh-message-id (mh-container-message v))
                                       mh-thread-id-index-map))
                     (push v results)))
               mh-thread-id-table)
      (mh-thread-sort-containers results))))

(defun mh-thread-sort-containers (containers)
  "Sort a list of message CONTAINERS to be in ascending order wrt index."
  (sort containers
        #'(lambda (x y)
            (when (and (mh-container-message x) (mh-container-message y))
              (let* ((id-x (mh-message-id (mh-container-message x)))
                     (id-y (mh-message-id (mh-container-message y)))
                     (index-x (gethash id-x mh-thread-id-index-map))
                     (index-y (gethash id-y mh-thread-id-index-map)))
                (and (integerp index-x) (integerp index-y)
                     (< index-x index-y)))))))

(defsubst mh-thread-group-by-subject (roots)
  "Group the set of message containers, ROOTS based on subject.
Bug: Check for and make sure that something without Re: is made the parent in
preference to something that has it."
  (clrhash mh-thread-subject-container-hash)
  (let ((results ()))
    (dolist (root roots)
      (let* ((subject (mh-thread-container-subject root))
             (parent (gethash subject mh-thread-subject-container-hash)))
        (cond (parent (mh-thread-remove-parent-link root)
                      (mh-thread-add-link parent root t)
                      (setf (mh-container-real-child-p root) nil)
                      (push `(SUBJECT ,root) mh-thread-history))
              (t
               (setf (gethash subject mh-thread-subject-container-hash) root)
               (push root results)))))
    (nreverse results)))

(defsubst mh-thread-process-in-reply-to (reply-to-header)
  "Extract message id's from REPLY-TO-HEADER.
Ideally this should have some regexp which will try to guess if a string
between < and > is a message id and not an email address. For now it will
take the last string inside angles."
  (let ((end (mh-search-from-end ?> reply-to-header)))
    (when (numberp end)
      (let ((begin (mh-search-from-end ?< (substring reply-to-header 0 end))))
        (when (numberp begin)
          (list (substring reply-to-header begin (1+ end))))))))

(defun mh-thread-set-tables (folder)
  "Use the tables of FOLDER in current buffer."
  (flet ((mh-get-table (symbol)
                       (save-excursion
                         (set-buffer folder)
                         (symbol-value symbol))))
    (setq mh-thread-id-hash (mh-get-table 'mh-thread-id-hash))
    (setq mh-thread-subject-hash (mh-get-table 'mh-thread-subject-hash))
    (setq mh-thread-id-table (mh-get-table 'mh-thread-id-table))
    (setq mh-thread-id-index-map (mh-get-table 'mh-thread-id-index-map))
    (setq mh-thread-index-id-map (mh-get-table 'mh-thread-index-id-map))
    (setq mh-thread-scan-line-map (mh-get-table 'mh-thread-scan-line-map))
    (setq mh-thread-subject-container-hash
          (mh-get-table 'mh-thread-subject-container-hash))
    (setq mh-thread-duplicates (mh-get-table 'mh-thread-duplicates))
    (setq mh-thread-history (mh-get-table 'mh-thread-history))))

(defsubst mh-thread-update-id-index-maps (id index)
  "Message with id, ID is the message in INDEX.
The function also checks for duplicate messages (that is multiple messages
with the same ID). These messages are put in the `mh-thread-duplicates' hash
table."
  (let ((old-index (gethash id mh-thread-id-index-map)))
    (when old-index (push old-index (gethash id mh-thread-duplicates)))
    (setf (gethash id mh-thread-id-index-map) index)
    (setf (gethash index mh-thread-index-id-map) id)))



;;; Generate Threads...

(defvar mh-message-id-regexp "^<.*@.*>$"
  "Regexp to recognize whether a string is a message identifier.")

(defun mh-thread-generate (folder msg-list)
  "Scan FOLDER to get info for threading.
Only information about messages in MSG-LIST are added to the tree."
  (with-temp-buffer
    (mh-thread-set-tables folder)
    (when msg-list
      (apply
       #'call-process (expand-file-name mh-scan-prog mh-progs) nil '(t nil) nil
       "-width" "10000" "-format"
       "%(msg)\n%{message-id}\n%{references}\n%{in-reply-to}\n%{subject}\n"
       folder (mapcar #'(lambda (x) (format "%s" x)) msg-list)))
    (goto-char (point-min))
    (let ((roots ())
          (case-fold-search t))
      (block nil
        (while (not (eobp))
          (block process-message
            (let* ((index-line
                    (prog1 (buffer-substring (point) (line-end-position))
                      (forward-line)))
                   (index (car (read-from-string index-line)))
                   (id (prog1 (buffer-substring (point) (line-end-position))
                         (forward-line)))
                   (refs (prog1 (buffer-substring (point) (line-end-position))
                           (forward-line)))
                   (in-reply-to (prog1 (buffer-substring (point)
                                                         (line-end-position))
                                  (forward-line)))
                   (subject (prog1
                                (buffer-substring (point) (line-end-position))
                              (forward-line)))
                   (subject-re-p nil))
              (unless (gethash index mh-thread-scan-line-map)
                (return-from process-message))
              (unless (integerp index) (return)) ;Error message here
              (multiple-value-setq (subject subject-re-p)
                (mh-thread-prune-subject subject))
              (setq in-reply-to (mh-thread-process-in-reply-to in-reply-to))
              (setq refs (loop for x in (append (split-string refs) in-reply-to)
                               when (string-match mh-message-id-regexp x)
                               collect x))
              (setq id (mh-thread-canonicalize-id id))
              (mh-thread-update-id-index-maps id index)
              (setq refs (mapcar #'mh-thread-canonicalize-id refs))
              (mh-thread-get-message id subject-re-p subject refs)
              (do ((ancestors refs (cdr ancestors)))
                  ((null (cdr ancestors))
                   (when (car ancestors)
                     (mh-thread-remove-parent-link id)
                     (mh-thread-add-link (car ancestors) id)))
                (mh-thread-add-link (car ancestors) (cadr ancestors)))))))
      (maphash #'(lambda (k v)
                   (declare (ignore k))
                   (when (null (mh-container-parent v))
                     (push v roots)))
               mh-thread-id-table)
      (setq roots (mh-thread-prune-containers roots))
      (prog1 (setq roots (mh-thread-group-by-subject roots))
        (let ((history mh-thread-history))
          (set-buffer folder)
          (setq mh-thread-history history))))))

;;;###mh-autoload
(defun mh-thread-inc (folder start-point)
  "Update thread tree for FOLDER.
All messages after START-POINT are added to the thread tree."
  (mh-thread-rewind-pruning)
  (goto-char start-point)
  (let ((msg-list ()))
    (while (not (eobp))
      (let ((index (mh-get-msg-num nil)))
        (when (numberp index)
          (push index msg-list)
          (setf (gethash index mh-thread-scan-line-map)
                (mh-thread-parse-scan-line)))
        (forward-line)))
    (let ((thread-tree (mh-thread-generate folder msg-list))
          (buffer-read-only nil)
          (old-buffer-modified-flag (buffer-modified-p)))
      (delete-region (point-min) (point-max))
      (let ((mh-thread-body-width (- (window-width) mh-cmd-note
                                     (1- mh-scan-field-subject-start-offset)))
            (mh-thread-last-ancestor nil))
        (mh-thread-generate-scan-lines thread-tree -2))
      (mh-notate-user-sequences)
      (mh-notate-deleted-and-refiled)
      (mh-notate-cur)
      (set-buffer-modified-p old-buffer-modified-flag))))

(defvar mh-thread-last-ancestor)

(defun mh-thread-generate-scan-lines (tree level)
  "Generate scan lines.
TREE is the hierarchical tree of messages, SCAN-LINE-MAP maps message indices
to the corresponding scan lines and LEVEL used to determine indentation of
the message."
  (cond ((null tree) nil)
        ((mh-thread-container-p tree)
         (let* ((message (mh-container-message tree))
                (id (mh-message-id message))
                (index (gethash id mh-thread-id-index-map))
                (duplicates (gethash id mh-thread-duplicates))
                (new-level (+ level 2))
                (dupl-flag t)
                (force-angle-flag nil)
                (increment-level-flag nil))
           (dolist (scan-line (mapcar (lambda (x)
                                        (gethash x mh-thread-scan-line-map))
                                      (reverse (cons index duplicates))))
             (when scan-line
               (when (and dupl-flag (equal level 0)
                          (mh-thread-ancestor-p mh-thread-last-ancestor tree))
                 (setq level (+ level 2)
                       new-level (+ new-level 2)
                       force-angle-flag t))
               (when (equal level 0)
                 (setq mh-thread-last-ancestor tree)
                 (while (mh-container-parent mh-thread-last-ancestor)
                   (setq mh-thread-last-ancestor
                         (mh-container-parent mh-thread-last-ancestor))))
               (let* ((lev (if dupl-flag level new-level))
                      (square-flag (or (and (mh-container-real-child-p tree)
                                            (not force-angle-flag)
                                            dupl-flag)
                                       (equal lev 0))))
                 (insert (car scan-line)
                         (format (format "%%%ss" lev) "")
                         (if square-flag "[" "<")
                         (cadr scan-line)
                         (if square-flag "]" ">")
                         (truncate-string-to-width
                          (caddr scan-line) (- mh-thread-body-width lev))
                         "\n"))
               (setq increment-level-flag t)
               (setq dupl-flag nil)))
           (unless increment-level-flag (setq new-level level))
           (dolist (child (mh-container-children tree))
             (mh-thread-generate-scan-lines child new-level))))
        (t (let ((nlevel (+ level 2)))
             (dolist (ch tree)
               (mh-thread-generate-scan-lines ch nlevel))))))

;; Another and may be better approach would be to generate all the info from
;; the scan which generates the threading info. For now this will have to do.
(defun mh-thread-parse-scan-line (&optional string)
  "Parse a scan line.
If optional argument STRING is given then that is assumed to be the scan line.
Otherwise uses the line at point as the scan line to parse."
  (let* ((string (or string
                     (buffer-substring-no-properties (line-beginning-position)
                                                     (line-end-position))))
         (first-string (substring string 0 (+ mh-cmd-note 8))))
    (setf (elt first-string mh-cmd-note) ? )
    (when (equal (elt first-string (1+ mh-cmd-note)) (elt mh-note-seq 0))
      (setf (elt first-string (1+ mh-cmd-note)) ? ))
    (list first-string
          (substring string
                     (+ mh-cmd-note mh-scan-field-from-start-offset)
                     (+ mh-cmd-note mh-scan-field-from-end-offset -2))
          (substring string (+ mh-cmd-note mh-scan-field-from-end-offset))
          string)))

;;;###mh-autoload
(defun mh-thread-add-spaces (count)
  "Add COUNT spaces to each scan line in `mh-thread-scan-line-map'."
  (let ((spaces (format (format "%%%ss" count) "")))
    (while (not (eobp))
      (let* ((msg-num (mh-get-msg-num nil))
             (old-line (nth 3 (gethash msg-num mh-thread-scan-line-map))))
        (when (numberp msg-num)
          (setf (gethash msg-num mh-thread-scan-line-map)
                (mh-thread-parse-scan-line (format "%s%s" spaces old-line)))))
      (forward-line 1))))

(defun mh-thread-folder ()
  "Generate thread view of folder."
  (message "Threading %s..." (buffer-name))
  (mh-thread-initialize)
  (goto-char (point-min))
  (let ((msg-list ()))
    (while (not (eobp))
      (let ((index (mh-get-msg-num nil)))
        (when (numberp index)
          (push index msg-list)
          (setf (gethash index mh-thread-scan-line-map)
                (mh-thread-parse-scan-line))))
      (forward-line))
    (let* ((range (mh-coalesce-msg-list msg-list))
           (thread-tree (mh-thread-generate (buffer-name) range)))
      (delete-region (point-min) (point-max))
      (let ((mh-thread-body-width (- (window-width) mh-cmd-note
                                     (1- mh-scan-field-subject-start-offset)))
            (mh-thread-last-ancestor nil))
        (mh-thread-generate-scan-lines thread-tree -2))
      (mh-notate-user-sequences)
      (mh-notate-deleted-and-refiled)
      (mh-notate-cur)
      (message "Threading %s...done" (buffer-name)))))

;;;###mh-autoload
(defun mh-toggle-threads ()
  "Toggle threaded view of folder."
  (interactive)
  (let ((msg-at-point (mh-get-msg-num nil))
        (old-buffer-modified-flag (buffer-modified-p))
        (buffer-read-only nil))
    (cond ((memq 'unthread mh-view-ops)
           (unless (mh-valid-view-change-operation-p 'unthread)
             (error "Can't unthread folder"))
           (let ((msg-list ()))
             (goto-char (point-min))
             (while (not (eobp))
               (let ((index (mh-get-msg-num t)))
                 (when index
                   (push index msg-list)))
               (forward-line))
             (mh-scan-folder mh-current-folder
                             (mapcar #'(lambda (x) (format "%s" x))
                                     (mh-coalesce-msg-list msg-list))
                             t))
           (when mh-index-data
             (mh-index-insert-folder-headers)
             (mh-notate-cur)))
          (t (mh-thread-folder)
             (push 'unthread mh-view-ops)))
    (when msg-at-point (mh-goto-msg msg-at-point t t))
    (set-buffer-modified-p old-buffer-modified-flag)
    (mh-recenter nil)))

;;;###mh-autoload
(defun mh-thread-forget-message (index)
  "Forget the message INDEX from the threading tables."
  (let* ((id (gethash index mh-thread-index-id-map))
         (id-index (gethash id mh-thread-id-index-map))
         (duplicates (gethash id mh-thread-duplicates)))
    (remhash index mh-thread-index-id-map)
    (cond ((and (eql index id-index) (null duplicates))
           (remhash id mh-thread-id-index-map))
          ((eql index id-index)
           (setf (gethash id mh-thread-id-index-map) (car duplicates))
           (setf (gethash (car duplicates) mh-thread-index-id-map) id)
           (setf (gethash id mh-thread-duplicates) (cdr duplicates)))
          (t
           (setf (gethash id mh-thread-duplicates)
                 (remove index duplicates))))))



;;; Operations on threads

(defun mh-thread-current-indentation-level ()
  "Find the number of spaces by which current message is indented."
  (save-excursion
    (let ((address-start-offset (+ mh-cmd-note mh-scan-date-flag-width
                                   mh-scan-date-width 1))
          (level 0))
      (beginning-of-line)
      (forward-char address-start-offset)
      (while (char-equal (char-after) ? )
        (incf level)
        (forward-char))
      level)))

;;;###mh-autoload
(defun mh-thread-next-sibling (&optional previous-flag)
  "Jump to next sibling.
With non-nil optional argument PREVIOUS-FLAG jump to the previous sibling."
  (interactive)
  (cond ((not (memq 'unthread mh-view-ops))
         (error "Folder isn't threaded"))
        ((eobp)
         (error "No message at point")))
  (beginning-of-line)
  (let ((point (point))
        (done nil)
        (my-level (mh-thread-current-indentation-level)))
    (while (and (not done)
                (equal (forward-line (if previous-flag -1 1)) 0)
                (not (eobp)))
      (let ((level (mh-thread-current-indentation-level)))
        (cond ((equal level my-level)
               (setq done 'success))
              ((< level my-level)
               (message "No %s sibling" (if previous-flag "previous" "next"))
               (setq done 'failure)))))
    (cond ((eq done 'success) (mh-maybe-show))
          ((eq done 'failure) (goto-char point))
          (t (message "No %s sibling" (if previous-flag "previous" "next"))
             (goto-char point)))))

;;;###mh-autoload
(defun mh-thread-previous-sibling ()
  "Jump to previous sibling."
  (interactive)
  (mh-thread-next-sibling t))

(defun mh-thread-immediate-ancestor ()
  "Jump to immediate ancestor in thread tree."
  (beginning-of-line)
  (let ((point (point))
        (ancestor-level (- (mh-thread-current-indentation-level) 2))
        (done nil))
    (if (< ancestor-level 0)
        nil
      (while (and (not done) (equal (forward-line -1) 0))
        (when (equal ancestor-level (mh-thread-current-indentation-level))
          (setq done t)))
      (unless done
        (goto-char point))
      done)))

;;;###mh-autoload
(defun mh-thread-ancestor (&optional thread-root-flag)
  "Jump to the ancestor of current message.
If optional argument THREAD-ROOT-FLAG is non-nil then jump to the root of the
thread tree the message belongs to."
  (interactive "P")
  (beginning-of-line)
  (cond ((not (memq 'unthread mh-view-ops))
         (error "Folder isn't threaded"))
        ((eobp)
         (error "No message at point")))
  (let ((current-level (mh-thread-current-indentation-level)))
    (cond (thread-root-flag
           (while (mh-thread-immediate-ancestor))
           (mh-maybe-show))
          ((equal current-level 1)
           (message "Message has no ancestor"))
          (t (mh-thread-immediate-ancestor)
             (mh-maybe-show)))))

(defun mh-thread-find-children ()
  "Return a region containing the current message and its children.
The result is returned as a list of two elements. The first is the point at the
start of the region and the second is the point at the end."
  (beginning-of-line)
  (if (eobp)
      nil
    (let ((address-start-offset (+ mh-cmd-note mh-scan-date-flag-width
                                   mh-scan-date-width 1))
          (level (mh-thread-current-indentation-level))
          spaces begin)
      (setq begin (point))
      (setq spaces (format (format "%%%ss" (1+ level)) ""))
      (forward-line)
      (block nil
        (while (not (eobp))
          (forward-char address-start-offset)
          (unless (equal (string-match spaces (buffer-substring-no-properties
                                               (point) (line-end-position)))
                         0)
            (beginning-of-line)
            (backward-char)
            (return))
          (forward-line)))
      (list begin (point)))))

;;;###mh-autoload
(defun mh-thread-delete ()
  "Mark current message and all its children for subsequent deletion."
  (interactive)
  (cond ((not (memq 'unthread mh-view-ops))
         (error "Folder isn't threaded"))
        ((eobp)
         (error "No message at point"))
        (t (let ((region (mh-thread-find-children)))
             (mh-iterate-on-messages-in-region () (car region) (cadr region)
               (mh-delete-a-msg nil))
             (mh-next-msg)))))

;;;###mh-autoload
(defun mh-thread-refile (folder)
  "Mark current message and all its children for refiling to FOLDER."
  (interactive (list (intern (mh-prompt-for-refile-folder))))
  (cond ((not (memq 'unthread mh-view-ops))
         (error "Folder isn't threaded"))
        ((eobp)
         (error "No message at point"))
        (t (let ((region (mh-thread-find-children)))
             (mh-iterate-on-messages-in-region () (car region) (cadr region)
               (mh-refile-a-msg nil folder))
             (mh-next-msg)))))

(provide 'mh-seq)

;;; Local Variables:
;;; indent-tabs-mode: nil
;;; sentence-end-double-space: nil
;;; End:

;;; mh-seq.el ends here