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path: root/translate_subx_emulated
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#!/bin/sh
# Translate SubX files to a bootable disk image.
#
# This script uses emulation, so it does not require x86 or Linux. However it
# is slow.

set -e
set -v

cat $*            |linux/bootstrap/bootstrap run linux/braces             > a.braces

cat a.braces      |linux/bootstrap/bootstrap run linux/calls              > a.calls

cat a.calls       |linux/bootstrap/bootstrap run linux/sigils             > a.sigils

cat a.sigils      |linux/bootstrap/bootstrap run linux/tests              > a.tests

# no assort since baremetal SubX doesn't have segments yet

cat a.tests       |linux/bootstrap/bootstrap run linux/dquotes            > a.dquotes

cat a.dquotes     |linux/bootstrap/bootstrap run linux/pack               > a.pack

cat a.pack        |linux/bootstrap/bootstrap run linux/survey_baremetal   > a.survey

cat a.survey      |linux/bootstrap/bootstrap run linux/hex                > a.bin

# Create disk.img containing boot.hex and a.bin
dd if=/dev/zero of=disk.img count=20160  # 512-byte sectors, so 10MB
linux/bootstrap/bootstrap run linux/hex < boot.hex  > boot.bin
cat boot.bin a.bin > disk.bin
dd if=disk.bin of=disk.img conv=notrunc

if [ `stat --printf="%s" disk.bin` -ge 193536 ]  # 6 tracks * 63 sectors per track * 512 bytes per sector (keep this sync'd with boot.hex)
then
  echo "disk.bin won't all be loaded on boot"
  exit 1
fi
id='n564' href='#n564'>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
(and-record trace [
  label:string-address
  contents:string-address
])
(address trace-address (trace))
(array trace-address-array (trace-address))
(address trace-address-array-address (trace-address-array))
(address trace-address-array-address-address (trace-address-array-address))

(and-record instruction-trace [
  call-stack:string-address-array-address
  pc:string-address  ; should be integer?
  instruction:string-address
  children:trace-address-array-address
])
(address instruction-trace-address (instruction-trace))
(array instruction-trace-address-array (instruction-trace-address))
(address instruction-trace-address-array-address (instruction-trace-address-array))

(function parse-traces [  ; stream-address -> instruction-trace-address-array-address
  (default-space:space-address <- new space:literal 30:literal)
;?   ($print (("parse-traces\n" literal))) ;? 2
  (in:stream-address <- next-input)
  ; check input size
  ($print (("counting lines\n" literal)))
  (n:integer <- copy 0:literal)
  { begin
    (done?:boolean <- end-of-stream? in:stream-address)
    (break-if done?:boolean)
;?     ($start-tracing) ;? 1
    (c:character <- read-character in:stream-address)
    { begin
      (newline?:boolean <- equal c:character ((#\newline literal)))
      (break-unless newline?:boolean)
      (n:integer <- add n:integer 1:literal)
      { begin
;?         (print?:boolean <- divides? n:integer 100:literal)
;?         (break-unless print?:boolean)
        ($print ((" " literal)))
        ($print n:integer)
        ($print (("\n" literal)))
      }
    }
;?     ($quit) ;? 1
    (loop)
  }
  ($print n:integer)
  ($print ((" lines\n" literal)))
  (in:stream-address <- rewind-stream in:stream-address)
  ; prepare result
  (result:buffer-address <- init-buffer 30:literal)
  (curr-tail:instruction-trace-address <- copy nil:literal)
  (ch:buffer-address <- init-buffer 5:literal)  ; accumulator for traces between instructions
  (run:string-address/const <- new "run")
  ($print (("parsing\n" literal)))
  (n:integer <- copy 0:literal)
  ; reading each line from 'in'
  { begin
    next-line
    (done?:boolean <- end-of-stream? in:stream-address)
;?     ($print done?:boolean) ;? 1
;?     ($print (("\n" literal))) ;? 1
    (break-if done?:boolean)
    ; parse next line as a generic trace
    (line:string-address <- read-line in:stream-address)
    { begin
      (n:integer <- add n:integer 1:literal)
      (print?:boolean <- divides? n:integer 100:literal)
      (break-unless print?:boolean)
      ($print ((" " literal)))
      ($print n:integer)
      ($print (("\n" literal)))
    }
;?     (print-string nil:literal/terminal line:string-address) ;? 1
    (f:trace-address <- parse-trace line:string-address)
    (l:string-address <- get f:trace-address/deref label:offset)
    { begin
      ; if it's an instruction trace with label 'run'
      (inst?:boolean <- string-equal l:string-address run:string-address/const)
      (break-unless inst?:boolean)
      ; add accumulated traces to curr-tail
      { begin
        (break-unless curr-tail:instruction-trace-address)
        (c:trace-address-array-address-address <- get-address curr-tail:instruction-trace-address/deref children:offset)
        (c:trace-address-array-address-address/deref <- to-array ch:buffer-address)
        ; clear 'ch'
        (ch:buffer-address <- init-buffer 5:literal)
      }
      ; append a new curr-tail to result
      (curr-tail:instruction-trace-address <- parse-instruction-trace f:trace-address)
      (result:buffer-address <- append result:buffer-address curr-tail:instruction-trace-address)
      (jump next-line:offset)  ; loop
    }
    ; otherwise accumulate trace
    (loop-unless curr-tail:instruction-trace-address)
    (ch:buffer-address <- append ch:buffer-address f:trace-address)
    (loop)
  }
  ; add accumulated traces to final curr-tail
  ; todo: test
  { begin
    (break-unless curr-tail:instruction-trace-address)
    (c:trace-address-array-address-address <- get-address curr-tail:instruction-trace-address/deref children:offset)
    (c:trace-address-array-address-address/deref <- to-array ch:buffer-address)
  }
  (s:instruction-trace-address-array-address <- to-array result:buffer-address)
  (reply s:instruction-trace-address-array-address)
])

(function parse-instruction-trace [  ; trace-address -> instruction-trace-address
  (default-space:space-address <- new space:literal 30:literal)
;?   ($print (("parse-instruction-trace\n" literal))) ;? 1
  (in:trace-address <- next-input)
  (buf:string-address <- get in:trace-address/deref contents:offset)
;?   (print-string nil:literal buf:string-address) ;? 1
;?   ($print (("\n" literal))) ;? 1
  (result:instruction-trace-address <- new instruction-trace:literal)
  (f1:string-address rest:string-address <- split-first buf:string-address ((#\space literal)))
;?   ($print (("call-stack: " literal))) ;? 1
;?   (print-string nil:literal f1:string-address) ;? 1
;?   ($print (("\n" literal))) ;? 1
  (cs:string-address-array-address-address <- get-address result:instruction-trace-address/deref call-stack:offset)
  (cs:string-address-array-address-address/deref <- split f1:string-address ((#\/ literal)))
  (p:string-address-address <- get-address result:instruction-trace-address/deref pc:offset)
  (delim:string-address <- new ": ")
  (p:string-address-address/deref rest:string-address <- split-first-at-substring rest:string-address delim:string-address)
  (inst:string-address-address <- get-address result:instruction-trace-address/deref instruction:offset)
  (inst:string-address-address/deref <- copy rest:string-address)
  (reply result:instruction-trace-address)
])

(function parse-trace [  ; string-address -> trace-address
  (default-space:space-address <- new space:literal 30:literal)
;?   ($print (("parse-trace\n" literal))) ;? 1
  (in:string-address <- next-input)
  (result:trace-address <- new trace:literal)
  (delim:string-address <- new ": ")
  (first:string-address rest:string-address <- split-first-at-substring in:string-address delim:string-address)
  (l:string-address-address <- get-address result:trace-address/deref label:offset)
  (l:string-address-address/deref <- copy first:string-address)
  (c:string-address-address <- get-address result:trace-address/deref contents:offset)
  (c:string-address-address/deref <- copy rest:string-address)
  (reply result:trace-address)
])

(function print-trace [
  (default-space:space-address <- new space:literal 30:literal)
  (screen:terminal-address <- next-input)
  (x:trace-address <- next-input)
  (l:string-address <- get x:trace-address/deref label:offset)
  (clear-line screen:terminal-address)
  (print-string screen:terminal-address l:string-address)
  (print-character screen:terminal-address ((#\space literal)))
  (print-character screen:terminal-address ((#\: literal)))
  (print-character screen:terminal-address ((#\space literal)))
  (c:string-address <- get x:trace-address/deref contents:offset)
  (print-string screen:terminal-address c:string-address)
])

(function print-instruction-trace-parent [
  (default-space:space-address <- new space:literal 30:literal)
  (screen:terminal-address <- next-input)
  (x:instruction-trace-address <- next-input)
  (0:space-address/names:browser-state <- next-input)
  (clear-line screen:terminal-address)
  (print-character screen:terminal-address ((#\- literal)))
  (print-character screen:terminal-address ((#\space literal)))
  ; print call stack
  (c:string-address-array-address <- get x:instruction-trace-address/deref call-stack:offset)
  (i:integer <- copy 0:literal)
  (len:integer <- length c:string-address-array-address/deref)
  { begin
    (done?:boolean <- greater-or-equal i:integer len:integer)
    (break-if done?:boolean)
    (s:string-address <- index c:string-address-array-address/deref i:integer)
    (print-string screen:terminal-address s:string-address)
    (print-character screen:terminal-address ((#\/ literal)))
    (i:integer <- add i:integer 1:literal)
    (loop)
  }
  ; print pc
  (print-character screen:terminal-address ((#\space literal)))
  (p:string-address <- get x:instruction-trace-address/deref pc:offset)
  (print-string screen:terminal-address p:string-address)
  ; print instruction
  (print-character screen:terminal-address ((#\space literal)))
  (print-character screen:terminal-address ((#\: literal)))
  (print-character screen:terminal-address ((#\space literal)))
  (i:string-address <- get x:instruction-trace-address/deref instruction:offset)
  (print-string screen:terminal-address i:string-address)
  (add-line 0:space-address/browser-state screen:terminal-address)
])

(function print-instruction-trace [
  (default-space:space-address <- new space:literal 30:literal)
  (screen:terminal-address <- next-input)
  (x:instruction-trace-address <- next-input)
  (0:space-address/names:browser-state <- next-input)
  (print-instruction-trace-parent screen:terminal-address x:instruction-trace-address 0:space-address/browser-state)
  ; print children
  (ch:trace-address-array-address <- get x:instruction-trace-address/deref children:offset)
  (i:integer <- copy 0:literal)
  { begin
    ; todo: test
    (break-if ch:trace-address-array-address)
    (reply)
  }
  (len:integer <- length ch:trace-address-array-address/deref)
  (expanded-children:integer/space:1 <- copy len:integer)
  { begin
;?     ($print (("i: " literal))) ;? 1
;?     ($print i:integer) ;? 1
;?     ($print (("\n" literal))) ;? 1
    ; until done with trace
    (done?:boolean <- greater-or-equal i:integer len:integer)
    (break-if done?:boolean)
    ; or screen ends
    (screen-done?:boolean <- greater-or-equal cursor-row:integer/space:1 screen-height:integer/space:1)
    (break-if screen-done?:boolean)
    (t:trace-address <- index ch:trace-address-array-address/deref i:integer)
    (print-character screen:terminal-address ((#\space literal)))
    (print-character screen:terminal-address ((#\space literal)))
    (print-character screen:terminal-address ((#\space literal)))
    (print-trace screen:terminal-address t:trace-address)
    (add-line 0:space-address/browser-state screen:terminal-address)
    (last-subindex-on-page:integer/space:1 <- copy i:integer)
;?     ($print (("subindex: " literal))) ;? 1
;?     ($print last-subindex-on-page:integer/space:1) ;? 1
;?     ($print (("\n" literal))) ;? 1
    (i:integer <- add i:integer 1:literal)
    (loop)
  }
])

(function print-instruction-trace-collapsed [
  (default-space:space-address <- new space:literal 30:literal)
  (screen:terminal <- next-input)
  (x:instruction-trace-address <- next-input)
  (browser-state:space-address <- next-input)
  (clear-line screen:terminal-address)
  (print-character screen:terminal-address ((#\+ literal)))
  (print-character screen:terminal-address ((#\space literal)))
  ; print call stack
  (c:string-address-array-address <- get x:instruction-trace-address/deref call-stack:offset)
  (i:integer <- copy 0:literal)
  (len:integer <- length c:string-address-array-address/deref)
  { begin
    (done?:boolean <- greater-or-equal i:integer len:integer)
    (break-if done?:boolean)
    (s:string-address <- index c:string-address-array-address/deref i:integer)
    (print-string screen:terminal-address s:string-address)
;?     (print-character screen:terminal-address ((#\space literal)))
    (print-character screen:terminal-address ((#\/ literal)))
;?     (print-character screen:terminal-address ((#\space literal)))
    (i:integer <- add i:integer 1:literal)
    (loop)
  }
  ; print pc
  (print-character screen:terminal-address ((#\space literal)))
  (p:string-address <- get x:instruction-trace-address/deref pc:offset)
  (print-string screen:terminal-address p:string-address)
  ; print instruction
  (print-character screen:terminal-address ((#\space literal)))
  (print-character screen:terminal-address ((#\: literal)))
  (print-character screen:terminal-address ((#\space literal)))
  (i:string-address <- get x:instruction-trace-address/deref instruction:offset)
  (print-string screen:terminal-address i:string-address)
  (add-line browser-state:space-address screen:terminal-address)
])

(function instruction-trace-num-children [
  (default-space:space-address <- new space:literal 30:literal)
  (traces:instruction-trace-address-array-address <- next-input)
  (index:integer <- next-input)
  (tr:instruction-trace-address <- index traces:instruction-trace-address-array-address/deref index:integer)
  (tr-children:trace-address-array-address <- get tr:instruction-trace-address/deref children:offset)
  (n:integer <- length tr-children:instruction-trace-address-array-address/deref)
  (reply n:integer)
])

;; data structure
(function browser-state [
  (default-space:space-address <- new space:literal 30:literal/capacity)
  ; trace state
  (traces:instruction-trace-address-array-address <- next-input)  ; the ground truth being rendered
  (expanded-index:integer <- copy -1:literal)  ; currently trace browser only ever shows one item expanded
  (expanded-children:integer <- copy -1:literal)
  (first-index-on-page:integer <- copy 0:literal)  ; 'outer' line with label 'run'
  (first-subindex-on-page:integer <- copy -2:literal)  ; 'inner' line with other labels; -2 or lower => not expanded; -1 => expanded and include parent; 0 => expanded and start at first child
  (last-index-on-page:integer <- copy 0:literal)
  (last-subindex-on-page:integer <- copy -2:literal)
  ; screen state
  (screen-height:integer <- next-input)  ; 'hardware' limitation
  (app-height:integer <- copy 0:literal)  ; area of the screen we're responsible for; can't be larger than screen-height
  (printed-height:integer <- copy 0:literal)  ; part of screen that currently has text; can't be larger than app-height
  (cursor-row:integer <- copy 0:literal)  ; position of cursor on screen; can't be larger than printed-height + 1
  (reply default-space:space-address)
])

(function $dump-browser-state [
  (default-space:space-address/names:browser-state <- next-input)
  ($print expanded-index:integer)
  ($print (("*" literal)))
  ($print expanded-children:integer)
  ($print ((": " literal)))
  ($print first-index-on-page:integer)
  ($print (("/" literal)))
  ($print first-subindex-on-page:integer)
  ($print ((" => " literal)))
  ($print last-index-on-page:integer)
  ($print (("/" literal)))
  ($print last-subindex-on-page:integer)
  ($print (("\n" literal)))
  ($print cursor-row:integer)
  ($print ((" " literal)))
  ($print printed-height:integer)
  ($print ((" " literal)))
  ($print app-height:integer)
  ($print ((" " literal)))
  ($print screen-height:integer)
  ($print (("\n" literal)))
])

(function down [
  (default-space:space-address <- new space:literal 30:literal/capacity)
  (0:space-address/names:browser-state <- next-input)
  (screen:terminal-address <- next-input)
  ; if at expanded, skip past nested lines
  { begin
    (no-expanded?:boolean <- less-than expanded-index:integer/space:1 0:literal)
    (break-if no-expanded?:boolean)
    (at-expanded?:boolean <- equal cursor-row:integer/space:1 expanded-index:integer/space:1)
    (break-unless at-expanded?:boolean)
;?     ($print (("down: at expanded index\n" literal))) ;? 1
    (n:integer <- instruction-trace-num-children traces:instruction-trace-address-array-address/space:1 expanded-index:integer/space:1)
    (n:integer <- add n:integer 1:literal)
    (i:integer <- copy 0:literal)
    { begin
      (done?:boolean <- greater-or-equal i:integer n:integer)
      (break-if done?:boolean)
      (at-bottom?:boolean <- greater-or-equal cursor-row:integer/space:1 printed-height:integer/space:1)
      (break-if at-bottom?:boolean)
;?       ($print (("down: incrementing\n" literal))) ;? 1
      (cursor-row:integer/space:1 <- add cursor-row:integer/space:1 1:literal)
      (cursor-down screen:terminal-address)
      (i:integer <- add i:integer 1:literal)
      (loop)
    }
    (reply)
  }
  ; if not at bottom, move cursor down
  { begin
    (at-bottom?:boolean <- greater-or-equal cursor-row:integer/space:1 printed-height:integer/space:1)
    (break-if at-bottom?:boolean)
    (cursor-row:integer/space:1 <- add cursor-row:integer/space:1 1:literal)
    (cursor-down screen:terminal-address)
  }
])

(function up [
  (default-space:space-address <- new space:literal 30:literal/capacity)
  (0:space-address/names:browser-state <- next-input)
  (screen:terminal-address <- next-input)
  ; if at expanded, skip past nested lines
  { begin
    (no-expanded?:boolean <- less-than expanded-index:integer/space:1 0:literal)
    (break-if no-expanded?:boolean)
    (n:integer <- instruction-trace-num-children traces:instruction-trace-address-array-address/space:1 expanded-index:integer/space:1)
    (n:integer <- add n:integer 1:literal)
    (cursor-row-below-expanded:integer <- add expanded-index:integer/space:1 n:integer)
    (just-below-expanded?:boolean <- equal cursor-row:integer/space:1 cursor-row-below-expanded:integer)
    (break-unless just-below-expanded?:boolean)
    (i:integer <- copy 0:literal)
    { begin
      (done?:boolean <- greater-or-equal i:integer n:integer)
      (break-if done?:boolean)
      (at-top?:boolean <- lesser-or-equal cursor-row:integer/space:1 0:literal)
      (break-if at-top?:boolean)
      (cursor-row:integer/space:1 <- subtract cursor-row:integer/space:1 1:literal)
      (cursor-up screen:terminal-address)
      (i:integer <- add i:integer 1:literal)
      (loop)
    }
    (reply)
  }
  ; if not at top, move cursor up
  { begin
    (at-top?:boolean <- lesser-or-equal cursor-row:integer/space:1 0:literal)
    (break-if at-top?:boolean)
    (cursor-row:integer/space:1 <- subtract cursor-row:integer/space:1 1:literal)
    (cursor-up screen:terminal-address)
  }
])

(function to-bottom [
  (default-space:space-address <- new space:literal 30:literal/capacity)
  (0:space-address/names:browser-state <- next-input)
  (screen:terminal-address <- next-input)
  { begin
    (at-bottom?:boolean <- greater-or-equal cursor-row:integer/space:1 printed-height:integer/space:1)
    (break-if at-bottom?:boolean)
    (down 0:space-address screen:terminal-address)
    (loop)
  }
])

(function to-top [
  (default-space:space-address <- new space:literal 30:literal/capacity)
  (0:space-address/names:browser-state <- next-input)
  (screen:terminal-address <- next-input)
  { begin
    (at-top?:boolean <- lesser-or-equal cursor-row:integer/space:1 0:literal)
    (break-if at-top?:boolean)
    (up 0:space-address screen:terminal-address)
    (loop)
  }
])

(function back-to [
  (default-space:space-address <- new space:literal 30:literal/capacity)
  (0:space-address/names:browser-state <- next-input)
  (screen:terminal-address <- next-input)
  (target-row:integer <- next-input)
;?   ($print (("before back-to: " literal))) ;? 1
;?   ($print cursor-row:integer/space:1) ;? 1
;?   ($print (("\n" literal))) ;? 1
  { begin
    (below-target?:boolean <- greater-than cursor-row:integer/space:1 target-row:integer)
    (break-unless below-target?:boolean)
;?     ($print (("below target\n" literal))) ;? 1
    (up 0:space-address screen:terminal-address)
    (loop)
  }
  { begin
    (above-target?:boolean <- less-than cursor-row:integer/space:1 target-row:integer)
    (break-unless above-target?:boolean)
;?     ($print (("above target\n" literal))) ;? 1
    (down 0:space-address screen:terminal-address)
    (loop)
  }
;?   ($print (("after back-to: " literal))) ;? 1
;?   ($print cursor-row:integer/space:1) ;? 1
;?   ($print (("\n" literal))) ;? 1
])

(function add-line [  ; move down, adding line if necessary
  (default-space:space-address <- new space:literal 30:literal/capacity)
  (0:space-address/names:browser-state <- next-input)
  (screen:terminal-address <- next-input)
  { begin
    (at-bottom?:boolean <- greater-or-equal cursor-row:integer/space:1 printed-height:integer/space:1)
    (break-unless at-bottom?:boolean)
    { begin
      (screen-full?:boolean <- greater-or-equal app-height:integer/space:1 screen-height:integer/space:1)
      (break-unless screen-full?:boolean)
      (cursor-to-next-line screen:terminal-address)
      (cursor-up screen:terminal-address)
      (reply)
    }
    (printed-height:integer/space:1 <- add printed-height:integer/space:1 1:literal)
    ; update app-height if necessary
    { begin
      (grow-max?:boolean <- greater-than printed-height:integer/space:1 app-height:integer/space:1)
      (break-unless grow-max?:boolean)
      (app-height:integer/space:1 <- copy printed-height:integer/space:1)
    }
  }
  (cursor-row:integer/space:1 <- add cursor-row:integer/space:1 1:literal)
  (cursor-to-next-line screen:terminal-address)
])

;; initial screen state
(function print-traces-collapsed [
  (default-space:space-address <- new space:literal 30:literal/capacity)
  (0:space-address/names:browser-state <- next-input)
  (screen:terminal-address <- next-input)
;?   ($print (("print traces collapsed\n" literal))) ;? 1
  (print-traces-collapsed-from 0:space-address/browser-state screen:terminal-address 0:literal/from)
  (clear-rest-of-page 0:space-address/browser-state screen:terminal-address)
])

(function print-traces-collapsed-from [
  (default-space:space-address <- new space:literal 30:literal/capacity)
  (0:space-address/names:browser-state <- next-input)
  (screen:terminal-address <- next-input)
  (trace-index:integer <- next-input)
  (limit-index:integer <- next-input)  ; print until this index (exclusive)
  ; compute bound
  (max:integer <- length traces:instruction-trace-address-array-address/space:1/deref)
  { begin
    (break-unless limit-index:integer)
    (max:integer <- min max:integer limit-index:integer)
  }
  ; print remaining traces collapsed
  { begin
    ; until trace ends
    (trace-done?:boolean <- greater-or-equal trace-index:integer max:integer)
    (break-if trace-done?:boolean)
    ; or screen ends
    (screen-done?:boolean <- greater-or-equal cursor-row:integer/space:1 screen-height:integer/space:1)
    (break-if screen-done?:boolean)
;?     ($print (("screen not done\n" literal))) ;? 1
    ; continue printing trace lines
    (tr:instruction-trace-address <- index traces:instruction-trace-address-array-address/space:1/deref trace-index:integer)
    (last-index-on-page:integer/space:1 <- copy trace-index:integer)
;?     ($print (("setting last index: " literal))) ;? 1
;?     ($print last-index-on-page:integer/space:1) ;? 1
;?     ($print (("\n" literal))) ;? 1
    (last-subindex-on-page:integer/space:1 <- copy -2:literal)
    (print-instruction-trace-collapsed screen:terminal-address tr:instruction-trace-address 0:space-address/browser-state)
    (trace-index:integer <- add trace-index:integer 1:literal)
    (loop)
  }
])

(function clear-rest-of-page [
  (default-space:space-address <- new space:literal 30:literal/capacity)
  (0:space-address/names:browser-state <- next-input)
  (screen:terminal-address <- next-input)
  { begin
    (done?:boolean <- greater-or-equal cursor-row:integer/space:1 app-height:integer/space:1)
    (break-if done?:boolean)
    (clear-line screen:terminal-address)
    (down 0:space-address/browser-state screen:terminal-address)
    (loop)
  }
])

(function print-page [
  (default-space:space-address <- new space:literal 30:literal/capacity)
  (0:space-address/names:browser-state <- next-input)
  (screen:terminal-address <- next-input)
;?   ($dump-browser-state 0:space-address/browser-state) ;? 3
  ; if top inside expanded index, complete existing trace
  (first-full-index:integer <- copy first-index-on-page:integer/space:1)
  { begin
    (screen-done?:boolean <- greater-or-equal cursor-row:integer/space:1 screen-height:integer/space:1)
    (break-unless screen-done?:boolean)
    (reply)
  }
;?   ($print (("\nAAA\n" literal))) ;? 4
  { begin
    (partial-trace?:boolean <- equal first-index-on-page:integer/space:1 expanded-index:integer/space:1)
    (break-unless partial-trace?:boolean)
;?   ($print (("AAA: partial\n" literal))) ;? 4
    (first-full-index:integer <- add first-full-index:integer 1:literal)
    (tr:instruction-trace-address <- index traces:instruction-trace-address-array-address/space:1/deref first-index-on-page:integer/space:1)
    { begin
      (print-parent?:boolean <- equal first-subindex-on-page:integer/space:1 -1:literal)
      (break-unless print-parent?:boolean)
      (print-instruction-trace-parent screen:terminal-address tr:instruction-trace-address 0:space-address/browser-state)
    }
    (ch:trace-address-array-address <- get tr:instruction-trace-address/deref children:offset)
    (i:integer <- max first-subindex-on-page:integer/space:1 0:literal)
    ; print any remaining data in the currently expanded trace
    { begin
      ; until done with trace
      (done?:boolean <- greater-or-equal i:integer expanded-children:integer/space:1)
      (break-if done?:boolean)
      ; or screen ends
      (screen-done?:boolean <- greater-or-equal cursor-row:integer/space:1 screen-height:integer/space:1)
      (break-if screen-done?:boolean)
;?       ($print (("AAA printing subtrace\n" literal))) ;? 3
      (t:trace-address <- index ch:trace-address-array-address/deref i:integer)
      (print-character screen:terminal-address ((#\space literal)))
      (print-character screen:terminal-address ((#\space literal)))
      (print-character screen:terminal-address ((#\space literal)))
      (print-trace screen:terminal-address t:trace-address)
      (add-line 0:space-address/browser-state screen:terminal-address)
      (last-subindex-on-page:integer/space:1 <- copy i:integer)
      (i:integer <- add i:integer 1:literal)
      (loop)
    }
  }
;?   ($print (("AAA 3: " literal))) ;? 5
;?   ($print cursor-row:integer/space:1) ;? 4
;?   ($print (("\n" literal))) ;? 4
  { begin
    (screen-done?:boolean <- greater-or-equal cursor-row:integer/space:1 screen-height:integer/space:1)
    (break-unless screen-done?:boolean)
    (reply)
  }
;?   ($print (("AAA 4\n" literal))) ;? 5
  { begin
    (has-expanded?:boolean <- greater-or-equal expanded-index:integer/space:1 0:literal)
    (break-if has-expanded?:boolean)
;?     ($print (("AAA 5a\n" literal))) ;? 4
    (print-traces-collapsed-from 0:space-address/browser-state screen:terminal-address first-full-index:integer)
    (clear-rest-of-page 0:space-address/browser-state screen:terminal-address)
    (reply)
  }
  { begin
    (below-expanded?:boolean <- greater-than first-full-index:integer expanded-index:integer/space:1)
    (break-unless below-expanded?:boolean)
;?     ($print (("AAA 5b\n" literal))) ;? 4
    (print-traces-collapsed-from 0:space-address/browser-state screen:terminal-address first-full-index:integer)
    (clear-rest-of-page 0:space-address/browser-state screen:terminal-address)
    (reply)
  }
  ; trace has an expanded index and it's below first-full-index
  ; print traces collapsed until expanded index
;?   ($print (("AAA 5c\n" literal))) ;? 4
  (print-traces-collapsed-from 0:space-address/browser-state screen:terminal-address first-full-index:integer expanded-index:integer/space:1/until)
  ; if room, start printing expanded index
  { begin
    (done?:boolean <- greater-or-equal cursor-row:integer/space:1 screen-height:integer/space:1)
    (break-if done?:boolean)
    (tr:instruction-trace-address <- index traces:instruction-trace-address-array-address/space:1/deref expanded-index:integer/space:1)
    (print-instruction-trace screen:terminal-address tr:instruction-trace-address 0:space-address/browser-state)
    (clear-rest-of-page 0:space-address/browser-state screen:terminal-address)
  }
])

(function cursor-row-to-trace-index [
  (default-space:space-address <- new space:literal 30:literal/capacity)
  (0:space-address/names:browser-state <- next-input)
  (n:integer/screen <- next-input)
;?   ($print (("to trace index: first subindex " literal))) ;? 1
;?   ($print first-subindex-on-page:integer/space:1) ;? 1
;?   ($print (("\n" literal))) ;? 1
;?   ($print (("cursor-to-index: n " literal))) ;? 2
;?   ($print n:integer) ;? 2
;?   ($print (("\n" literal))) ;? 2
;?   ($print (("cursor-to-index: first index " literal))) ;? 2
;?   ($print first-index-on-page:integer/space:1) ;? 2
;?   ($print (("\n" literal))) ;? 2
  (simple-result:integer <- add first-index-on-page:integer/space:1 n:integer)
;?   ($print (("cursor-to-index: simple result " literal))) ;? 2
;?   ($print simple-result:integer) ;? 2
;?   ($print (("\n" literal))) ;? 2
  ; no row expanded? no munging needed
  { begin
    (has-expanded?:boolean <- greater-or-equal expanded-index:integer/space:1 0:literal)
    (break-if has-expanded?:boolean)
    (reply simple-result:integer)
  }
  ; expanded row above current page? no munging needed
  { begin
    (below-expanded?:boolean <- less-than expanded-index:integer/space:1 first-index-on-page:integer/space:1)
    (break-unless below-expanded?:boolean)
    (reply simple-result:integer)
  }
  ; expanded row at top of current page and partial?
  { begin
    (expanded-at-top?:boolean <- equal first-index-on-page:integer/space:1 expanded-index:integer/space:1)
;?     ($print (("cursor-to-index: first subindex " literal))) ;? 2
;?     ($print first-subindex-on-page:integer/space:1) ;? 2
;?     ($print (("\n" literal))) ;? 2
    (partial-at-top?:boolean <- greater-or-equal first-subindex-on-page:integer/space:1 0:literal)
;?     ($print (("AAA\n" literal))) ;? 1
    (partial-expanded-at-top?:boolean <- and expanded-at-top?:boolean partial-at-top?:boolean)
    (break-unless partial-expanded-at-top?:boolean)
;?     ($print (("expanded child at top of page\n" literal))) ;? 2
    (expanded-children-on-page:integer <- subtract expanded-children:integer/space:1 first-subindex-on-page:integer/space:1)
    (result:integer <- subtract simple-result:integer expanded-children-on-page:integer)
    (result:integer <- add result:integer 1:literal)
    (result:integer <- max result:integer first-index-on-page:integer/space:1)
    (reply result:integer)
  }
  ; expanded row is below current page? no munging needed
  { begin
    (above-expanded?:boolean <- lesser-or-equal last-index-on-page:integer/space:1 expanded-index:integer/space:1 )
    (break-unless above-expanded?:boolean)
    (reply simple-result:integer)
  }
  (expanded-index-cursor-row:integer <- subtract expanded-index:integer/space:1 first-index-on-page:integer/space:1)
  ; cursor is above expanded index? no munging needed
  { begin
    (above-expanded?:boolean <- lesser-or-equal cursor-row:integer/space:1 expanded-index-cursor-row:integer)
    (break-unless above-expanded?:boolean)
    (reply simple-result:integer)
  }
  (result:integer/index <- subtract simple-result:integer expanded-children:integer/space:1)
  (reply result:integer/index)
])

(function back-to-index [
  (default-space:space-address <- new space:literal 30:literal/capacity)
  (0:space-address/names:browser-state <- next-input)
  (screen:terminal-address <- next-input)
  (target-index:integer <- next-input)
;?   ($print (("back-to-index: target " literal))) ;? 3
;?   ($print target-index:integer) ;? 3
;?   ($print (("\n" literal))) ;? 3
;?   ($print (("back-to-index: first subindex " literal))) ;? 1
;?   ($print first-subindex-on-page:integer/space:1) ;? 1
;?   ($print (("\n" literal))) ;? 1
  ; scan up until top, or *before* target-index (to skip expanded children)
  { begin
;?     ($print cursor-row:integer/space:1) ;? 1
;?     ($print (("\n" literal))) ;? 1
    (at-top?:boolean <- equal cursor-row:integer/space:1 0:literal)
    (break-if at-top?:boolean)
    (index:integer <- cursor-row-to-trace-index 0:space-address/browser-state cursor-row:integer/space:1)
;?     ($print cursor-row:integer/space:1) ;? 3
;?     ($print ((" " literal))) ;? 3
;?     ($print index:integer) ;? 3
;?     ($print (("\n" literal))) ;? 3
    (done?:boolean <- less-than index:integer target-index:integer)
    (break-if done?:boolean)
    (up 0:space-address screen:terminal-address)
    (loop)
  }
  ; now if we're before target-index, down 1
;?   ($print (("final down?\n" literal))) ;? 1
  (index:integer <- cursor-row-to-trace-index 0:space-address/browser-state cursor-row:integer/space:1)
;?   ($print (("done scanning; cursor at row " literal))) ;? 2
;?   ($print cursor-row:integer/space:1) ;? 2
;?   ($print ((", which is index " literal))) ;? 2
;?   ($print index:integer) ;? 2
;?   ($print (("\n" literal))) ;? 2
  { begin
    (at-target?:boolean <- greater-or-equal index:integer target-index:integer)
    (break-if at-target?:boolean)
;?     ($print (("down 1\n" literal))) ;? 2
    ; above expanded
    (down 0:space-address screen:terminal-address)
  }
])

;; pagination helpers
(function at-first-page [
  (default-space:space-address <- new space:literal 30:literal/capacity)
  (0:space-address/names:browser-state <- next-input)  ; read-only
  (result:boolean <- lesser-or-equal first-index-on-page:integer/space:1 0:literal)
  { begin
    (break-if result:boolean)
    (reply nil:literal)
  }
  (expanded?:boolean <- equal expanded-index:integer/space:1 0:literal)
  { begin
    (break-if expanded?:boolean)
    (reply t:literal)
  }
  ; if first subindex is 0, the top-level line is on a previous page
  (result:boolean <- less-than first-subindex-on-page:integer/space:1 0:literal)
  (reply result:boolean)
])

(function at-final-page [
  (default-space:space-address <- new space:literal 30:literal/capacity)
  (0:space-address/names:browser-state <- next-input)  ; read-only
  (len:integer <- length traces:instruction-trace-address-array-address/space:1/deref)
  (final-index:integer <- subtract len:integer 1:literal)
  (result:boolean <- greater-or-equal last-index-on-page:integer/space:1 final-index:integer)
  { begin
    (break-if result:boolean)
    (reply nil:literal)
  }
  (last-trace-expanded?:boolean <- equal expanded-index:integer/space:1 len:integer)
  { begin
    (break-if last-trace-expanded?:boolean)
    (reply t:literal)
  }
  (result:boolean <- greater-or-equal last-subindex-on-page:integer/space:1 expanded-children:integer/space:1)
  (reply result:boolean)
])

(function next-page [
  (default-space:space-address <- new space:literal 30:literal/capacity)
  (0:space-address/names:browser-state <- next-input)
  { begin
;?     ($print (("expanded: " literal))) ;? 3
;?     ($print expanded-index:integer/space:1) ;? 3
;?     ($print ((" last index: " literal))) ;? 3
;?     ($print last-index-on-page:integer/space:1) ;? 3
;?     ($print (("\n" literal))) ;? 3
    (last-index-expanded?:boolean <- equal expanded-index:integer/space:1 last-index-on-page:integer/space:1)
    (break-unless last-index-expanded?:boolean)
    ; expanded
;?     ($print (("last expanded\n" literal))) ;? 3
    { begin
      (expanded-index-done?:boolean <- equal expanded-children:integer/space:1 last-subindex-on-page:integer/space:1)
      (break-if expanded-index-done?:boolean 2:blocks)
;?       ($print (("children left\n" literal))) ;? 3
      ; children left to open
      (first-index-on-page:integer/space:1 <- copy last-index-on-page:integer/space:1)
      (first-subindex-on-page:integer/space:1 <- add last-subindex-on-page:integer/space:1 1:literal)
      (reply)
    }
  }
  (first-index-on-page:integer/space:1 <- add last-index-on-page:integer/space:1 1:literal)
  (first-subindex-on-page:integer/space:1 <- copy -2:literal)
])

(function previous-page [
  (default-space:space-address <- new space:literal 30:literal/capacity)
  (0:space-address/names:browser-state <- next-input)
;?   ($print (("before: " literal))) ;? 2
;?   ($print first-index-on-page:integer/space:1) ;? 2
;?   ($print ((" " literal))) ;? 2
;?   ($print first-subindex-on-page:integer/space:1) ;? 2
;?   ($print (("\n" literal))) ;? 2
  ; easy case: no expanded-index
  (jump-unless expanded-index:integer/space:1)
;?   ($print (("b\n" literal))) ;? 4
  (x:boolean <- less-than expanded-index:integer/space:1 0:literal)
  (jump-if x:boolean easy-case:offset)
  ; easy case: expanded-index lies below top of current page
;?   ($print (("c\n" literal))) ;? 4
  (x:boolean <- greater-than expanded-index:integer/space:1 first-index-on-page:integer/space:1)
  (jump-if x:boolean easy-case:offset)
  ; easy case: expanded-index *starts* at top of current page
;?   ($print (("d\n" literal))) ;? 5
  (top-of-screen-inside-expanded:boolean <- equal expanded-index:integer/space:1 first-index-on-page:integer/space:1)
  (y:boolean <- lesser-or-equal first-subindex-on-page:integer/space:1 -1:literal)
  (y:boolean <- and top-of-screen-inside-expanded:boolean y:boolean)
  (jump-if y:boolean easy-case:offset)
  ; easy case: expanded-index too far up for previous page
;?   ($print (("e\n" literal))) ;? 5
  (delta-to-expanded:integer <- subtract first-index-on-page:integer/space:1 expanded-index:integer/space:1)
;?   ($print delta-to-expanded:integer) ;? 1
;?   ($print (("\n" literal))) ;? 1
  (x:boolean <- greater-than delta-to-expanded:integer screen-height:integer/space:1)
  (jump-if x:boolean easy-case:offset)
;?   ($print (("f\n" literal))) ;? 5
  ; tough case: expanded index overlaps current and/or previous page
  (lines-remaining-to-decrement:integer <- copy screen-height:integer/space:1)
  ; a) scroll to just below expanded-index if necessary
  (below-expanded-index:integer <- add expanded-index:integer/space:1 1:literal)
  { begin
    (done?:boolean <- done-scrolling-up default-space:space-address)
    (break-if done?:boolean)
    (done?:boolean <- lesser-or-equal first-index-on-page:integer/space:1 below-expanded-index:integer)
    (break-if done?:boolean)
;?     ($print (("g\n" literal))) ;? 2
    (first-index-on-page:integer/space:1 <- subtract first-index-on-page:integer/space:1 1:literal)
    (lines-remaining-to-decrement:integer <- subtract lines-remaining-to-decrement:integer 1:literal)
    (loop)
  }
  { begin
;?     ($print (("h\n" literal))) ;? 2
    (x:boolean <- equal first-index-on-page:integer/space:1 below-expanded-index:integer)
    (break-unless x:boolean)
    (first-index-on-page:integer/space:1 <- copy expanded-index:integer/space:1)
    (first-subindex-on-page:integer/space:1 <- subtract expanded-children:integer/space:1 1:literal)
    (lines-remaining-to-decrement:integer <- subtract lines-remaining-to-decrement:integer 1:literal)
  }
  ; b) scroll through expanded-children if necessary
  { begin
    (done?:boolean <- done-scrolling-up default-space:space-address)
    (break-if done?:boolean)
    (done?:boolean <- less-than first-subindex-on-page:integer/space:1 0:literal)
    (break-if done?:boolean)
;?     ($print (("i\n" literal))) ;? 2
    (first-subindex-on-page:integer/space:1 <- subtract first-subindex-on-page:integer/space:1 1:literal)
    (lines-remaining-to-decrement:integer <- subtract lines-remaining-to-decrement:integer 1:literal)
    (loop)
  }
  ; c) jump past expanded-index parent if necessary
;?   ($print (("j\n" literal))) ;? 2
  { begin
    (done?:boolean <- done-scrolling-up default-space:space-address)
    (break-if done?:boolean)
;?     ($print (("k\n" literal))) ;? 2
    (first-index-on-page:integer/space:1 <- subtract first-index-on-page:integer/space:1 1:literal)
    (first-subindex-on-page:integer/space:1 <- copy -2:literal)
    (lines-remaining-to-decrement:integer <- subtract lines-remaining-to-decrement:integer 1:literal)
  }
  ; d) scroll up before expanded-index if necessary
;?   ($print (("l\n" literal))) ;? 2
  { begin
    (done?:boolean <- done-scrolling-up default-space:space-address)
    (break-if done?:boolean)
;?     ($print (("m\n" literal))) ;? 2
    (first-index-on-page:integer/space:1 <- subtract first-index-on-page:integer/space:1 1:literal)
    (lines-remaining-to-decrement:integer <- subtract lines-remaining-to-decrement:integer 1:literal)
    (loop)
  }
  (reply)
  easy-case
  (first-index-on-page:integer/space:1 <- subtract first-index-on-page:integer/space:1 screen-height:integer/space:1)
  (first-index-on-page:integer/space:1 <- max first-index-on-page:integer/space:1 0:literal)
  (first-subindex-on-page:integer/space:1 <- copy -2:literal)
])

(function done-scrolling-up [
  (default-space:space-address/names:previous-page <- next-input)
  (0:space-address/names:browser-state <- copy 0:space-address)  ; just to wire up names for space/1
  (at-top-of-screen?:boolean <- lesser-or-equal lines-remaining-to-decrement:integer 0:literal)
  (jump-if at-top-of-screen?:boolean done:offset)
  (at-first-index:boolean <- lesser-or-equal first-index-on-page:integer/space:1 0:literal)
  (at-first-subindex:boolean <- lesser-or-equal first-subindex-on-page:integer/space:1 -1:literal)
  (trace-done?:boolean <- and at-first-index:boolean at-first-subindex:boolean)
  (jump-if trace-done?:boolean done:offset)
  (reply nil:literal)
  done
  (reply t:literal)
])

;; modify screen state in response to a single key
(function process-key [
  (default-space:space-address <- new space:literal 30:literal/capacity)
  (0:space-address/names:browser-state <- next-input)
  (k:keyboard-address <- next-input)
  (screen:terminal-address <- next-input)
  (c:character <- read-key k:keyboard-address silent:literal/terminal)
  { begin
    ; no key yet
    (break-if c:character)
    (reply nil:literal)
  }
;?   ($print (("key pressed: " literal))) ;? 1
;?   ($write c:character) ;? 1
;?   ($print (("\n" literal))) ;? 1
  { begin
    ; user quit
    (q-pressed?:boolean <- equal c:character ((#\q literal)))
    (end-of-fake-keyboard-input?:boolean <- equal c:character ((#\null literal)))
    (quit?:boolean <- or q-pressed?:boolean end-of-fake-keyboard-input?:boolean)
    (break-unless quit?:boolean)
    (reply t:literal)
  }
  ; up/down navigation
  { begin
    (up?:boolean <- equal c:character ((up literal)))
    (k?:boolean <- equal c:character ((#\k literal)))
    (up?:boolean <- or up?:boolean k?:boolean)
    (break-unless up?:boolean)
    (up 0:space-address/browser-state screen:terminal-address)
    (reply nil:literal)
  }
  { begin
    (down?:boolean <- equal c:character ((down literal)))
    (j?:boolean <- equal c:character ((#\j literal)))
    (down?:boolean <- or down?:boolean j?:boolean)
    (break-unless down?:boolean)
    (down 0:space-address/browser-state screen:terminal-address)
    (reply nil:literal)
  }
  ; page up/page down
  { begin
    ; if page-up pressed
    (page-up?:boolean <- equal c:character ((pgup literal)))
    (K?:boolean <- equal c:character ((#\K literal)))
    (page-up?:boolean <- or page-up?:boolean K?:boolean)
    (break-unless page-up?:boolean)
    ; if we're not already at start of trace
    (first-page?:boolean <- at-first-page 0:space-address/browser-state)
    (break-if first-page?:boolean)
    ; move cursor to top of screen
    (to-top 0:space-address/browser-state screen:terminal-address)
    ; switch browser state
    (previous-page 0:space-address/browser-state)
;?     ($dump-browser-state 0:space-address) ;? 3
    ; redraw
    (print-page 0:space-address/browser-state screen:terminal-address)
    (reply nil:literal)
  }
  { begin
    ; if page-down pressed
    (page-down?:boolean <- equal c:character ((pgdn literal)))
    (J?:boolean <- equal c:character ((#\J literal)))
    (page-down?:boolean <- or page-down?:boolean J?:boolean)
    (break-unless page-down?:boolean)
    ; if we're not already at end of trace
    (final-page?:boolean <- at-final-page 0:space-address/browser-state)
    (break-if final-page?:boolean)
    ; move cursor to top of screen
    (to-top 0:space-address/browser-state screen:terminal-address)
;?     ($print (("before: " literal))) ;? 1
;?     ($print first-index-on-page:integer/space:1) ;? 1
;?     ($print (("\n" literal))) ;? 1
    ; switch browser state
    (next-page 0:space-address/browser-state)
;?     ($print (("after: " literal))) ;? 1
;?     ($print first-index-on-page:integer/space:1) ;? 1
;?     ($print (("\n" literal))) ;? 1
    ; redraw
    (print-page 0:space-address/browser-state screen:terminal-address)
    ; move cursor back to top of screen
    (to-top 0:space-address/browser-state screen:terminal-address)
    (reply nil:literal)
  }
  ; enter: expand/collapse current row
  { begin
    (toggle?:boolean <- equal c:character ((#\newline literal)))
    (break-unless toggle?:boolean)
;?     ($print (("expand: first subindex " literal))) ;? 1
;?     ($print first-subindex-on-page:integer/space:1) ;? 1
;?     ($print (("\n" literal))) ;? 1
    (original-cursor-row:integer <- copy cursor-row:integer/space:1)
;?     ($print (("cursor starts at row " literal))) ;? 6
;?     ($print original-cursor-row:integer) ;? 7
;?     ($print (("\n" literal))) ;? 7
    (original-trace-index:integer <- cursor-row-to-trace-index 0:space-address/browser-state original-cursor-row:integer)
;?     ($print (("which maps to index " literal))) ;? 7
;?     ($print original-trace-index:integer) ;? 9
;?     ($print (("\n" literal))) ;? 9
    ; is expanded-index already set?
    { begin
      (expanded?:boolean <- greater-or-equal expanded-index:integer/space:1 0:literal)
      (break-unless expanded?:boolean)
      (too-early?:boolean <- less-than expanded-index:integer/space:1 first-index-on-page:integer/space:1)
      (break-if too-early?:boolean)
      (too-late?:boolean <- greater-than expanded-index:integer/space:1 last-index-on-page:integer/space:1)
      (break-if too-late?:boolean)
      ; expanded-index is now on this page
;?       ($print (("expanded index on this page\n" literal))) ;? 6
      { begin
        ; are we at the expanded row?
        (at-expanded?:boolean <- equal original-trace-index:integer expanded-index:integer/space:1)
        (break-unless at-expanded?:boolean)
;?         ($print (("at expanded index\n" literal))) ;? 5
        ; print remaining lines collapsed and return
        (back-to-index 0:space-address/browser-state screen:terminal-address expanded-index:integer/space:1)
        (expanded-index:integer/space:1 <- copy -1:literal)
        (expanded-children:integer/space:1 <- copy -1:literal)
        (print-traces-collapsed-from 0:space-address/browser-state screen:terminal-address original-trace-index:integer)
        (clear-rest-of-page 0:space-address/browser-state screen:terminal-address)
        (back-to 0:space-address/browser-state screen:terminal-address original-cursor-row:integer)
        (reply nil:literal)
      }
      ; are we below the expanded row?
      { begin
        (below-expanded?:boolean <- greater-than original-trace-index:integer expanded-index:integer/space:1)
        (break-unless below-expanded?:boolean)
;?         ($print (("below expanded index\n" literal))) ;? 6
        (back-to-index 0:space-address/browser-state screen:terminal-address expanded-index:integer/space:1)
;?         ($print (("scanning up to row " literal))) ;? 3
;?         ($print cursor-row:integer/space:1) ;? 3
;?         ($print (("\n" literal))) ;? 3
        ; print traces collapsed until just before original row
        (print-traces-collapsed-from 0:space-address/browser-state screen:terminal-address expanded-index:integer/space:1 original-trace-index:integer/until)
        ; fall through
      }
    }
    ; expand original row and print traces below it
;?     ($print (("done collapsing previously expanded index\n" literal))) ;? 6
    (expanded-index:integer/space:1 <- copy original-trace-index:integer)
    (last-index-on-page:integer/space:1 <- copy original-trace-index:integer)
    (tr:instruction-trace-address <- index traces:instruction-trace-address-array-address/space:1/deref original-trace-index:integer)
;?     ($print (("expanded\n" literal))) ;? 6
    (print-instruction-trace screen:terminal-address tr:instruction-trace-address 0:space-address/browser-state)
    (next-index:integer <- add original-trace-index:integer 1:literal)
;?     ($print (("printing collapsed lines from " literal))) ;? 7
;?     ($print next-index:integer) ;? 8
;?     ($print (("\n" literal))) ;? 8
    (print-traces-collapsed-from 0:space-address/browser-state screen:terminal-address next-index:integer)
;?     ($print (("clearing rest of page\n" literal))) ;? 6
    (clear-rest-of-page 0:space-address/browser-state screen:terminal-address)
;?     ($print (("moving cursor back up\n" literal))) ;? 6
    (back-to-index 0:space-address/browser-state screen:terminal-address original-trace-index:integer)
;?     ($print (("returning\n" literal))) ;? 5
    (reply nil:literal)
  }
  (reply nil:literal)
])

(function browse-trace [
  (default-space:space-address <- new space:literal 30:literal/capacity)
  ($print (("parsing trace... (might take a while, depending on how long the trace is)\n" literal)))
  (x:string-address <- next-input)
  (screen-height:integer <- next-input)
;?   (print-string nil:literal/terminal x:string-address) ;? 1
  (s:stream-address <- init-stream x:string-address)
  (traces:instruction-trace-address-array-address <- parse-traces s:stream-address)
  (0:space-address/names:browser-state <- browser-state traces:instruction-trace-address-array-address screen-height:integer)
  (cursor-mode)
  (print-traces-collapsed 0:space-address/browser-state nil:literal/terminal)
  { begin
    (quit?:boolean <- process-key 0:space-address/browser-state nil:literal/keyboard nil:literal/terminal)
    (break-if quit?:boolean)
    (loop)
  }
  ; move cursor to bottom before exiting
  (to-bottom 0:space-address/browser-state nil:literal/terminal)
  (retro-mode)
])

(function main [
  (default-space:space-address <- new space:literal 30:literal/capacity)
  ($print (("loading trace.. (takes ~10s)\n" literal)))
  (x:string-address <- new
"run: main 0: a b c
mem: 0
run: main 1: d e f
mem: 1
mem: 1
mem: 1
mem: 1
mem: 1
run: main 2: g hi
run: main 3: j
mem: 3
run: main 4: k
run: main 5: l
run: main 6: m
run: main 7: n
run: main 8: o")
  (browse-trace x:string-address 3:literal/screen-height)
])