:(before "End Primitive Recipe Declarations")
_BROWSE_TRACE,
:(before "End Primitive Recipe Numbers")
put(Recipe_ordinal, "$browse-trace", _BROWSE_TRACE);
:(before "End Primitive Recipe Checks")
case _BROWSE_TRACE: {
  break;
}
:(before "End Primitive Recipe Implementations")
case _BROWSE_TRACE: {
  start_trace_browser();
  break;
}

:(before "End Globals")
set<long long int> Visible;
long long int Top_of_screen = 0;
long long int Last_printed_row = 0;
map<int, long long int> Trace_index;  // screen row -> trace index

:(code)
void start_trace_browser() {
  if (!Trace_stream) return;
  cerr << "computing depth to display\n";
  long long int min_depth = 9999;
  for (long long int i = 0; i < SIZE(Trace_stream->past_lines); ++i) {
    trace_line& curr_line = Trace_stream->past_lines.at(i);
    if (curr_line.depth == 0) continue;
    if (curr_line.depth < min_depth) min_depth = curr_line.depth;
  }
  cerr << "depth is " << min_depth << '\n';
  cerr << "computing lines to display\n";
  for (long long int i = 0; i < SIZE(Trace_stream->past_lines); ++i) {
    if (Trace_stream->past_lines.at(i).depth == min_depth)
      Visible.insert(i);
  }
  tb_init();
  Display_row = Display_column = 0;
  tb_event event;
  Top_of_screen = 0;
  refresh_screen_rows();
  while (true) {
    render();
    do {
      tb_poll_event(&event);
    } while (event.type != TB_EVENT_KEY);
    long long int key = event.key ? event.key : event.ch;
    if (key == 'q' || key == 'Q') break;
    if (key == 'j' || key == TB_KEY_ARROW_DOWN) {
      // move cursor one line down
      if (Display_row < Last_printed_row) ++Display_row;
    }
    if (key == 'k' || key == TB_KEY_ARROW_UP) {
      // move cursor one line up
      if (Display_row > 0) --Display_row;
    }
    if (key == 'H') {
      // move cursor to top of screen
      Display_row = 0;
    }
    if (key == 'M') {
      // move cursor to center of screen
      Display_row = tb_height()/2;
    }
    if (key == 'L') {
      // move cursor to bottom of screen
      Display_row = tb_height()-1;
    }
    if (key == 'J' || key == TB_KEY_PGDN) {
      // page-down
      if (Trace_index.find(tb_height()-1) != Trace_index.end()) {
        Top_of_screen = Trace_index[tb_height()-1]+1;
        refresh_screen_rows();
      }
    }
    if (key == 'K' || key == TB_KEY_PGUP) {
      // page-up is more convoluted
      for (int screen_row = tb_height(); screen_row > 0 && Top_of_screen > 0; --screen_row) {
        --Top_of_screen;
        if (Top_of_screen <= 0) break;
        while (Top_of_screen > 0 && !contains_key(Visible, Top_of_screen))
          --Top_of_screen;
      }
      if (Top_of_screen > 0)
        refresh_screen_rows();
    }
    if (key == 'G') {
      // go to bottom of screen; largely like page-up, interestingly
      Top_of_screen = SIZE(Trace_stream->past_lines)-1;
      for (int screen_row = tb_height(); screen_row > 0 && Top_of_screen > 0; --screen_row) {
        --Top_of_screen;
        if (Top_of_screen <= 0) break;
        while (Top_of_screen > 0 && !contains_key(Visible, Top_of_screen))
          --Top_of_screen;
      }
      refresh_screen_rows();
      // move cursor to bottom
      Display_row = Last_printed_row;
      refresh_screen_rows();
    }
    if (key == TB_KEY_CARRIAGE_RETURN) {
      // expand lines under current by one level
      assert(contains_key(Trace_index, Display_row));
      long long int start_index = Trace_index[Display_row];
      long long int index = 0;
      // simultaneously compute end_index and min_depth
      int min_depth = 9999;
      for (index = start_index+1; index < SIZE(Trace_stream->past_lines); ++index) {
        if (contains_key(Visible, index)) break;
        trace_line& curr_line = Trace_stream->past_lines.at(index);
        if (curr_line.depth == 0) continue;
        assert(curr_line.depth > Trace_stream->past_lines.at(start_index).depth);
        if (curr_line.depth < min_depth) min_depth = curr_line.depth;
      }
      long long int end_index = index;
      // mark as visible all intervening indices at min_depth
      for (index = start_index; index < end_index; ++index) {
        trace_line& curr_line = Trace_stream->past_lines.at(index);
        if (curr_line.depth == min_depth) {
          Visible.insert(index);
        }
      }
      refresh_screen_rows();
    }
    if (key == TB_KEY_BACKSPACE || key == TB_KEY_BACKSPACE2) {
      // collapse all lines under current
      assert(contains_key(Trace_index, Display_row));
      long long int start_index = Trace_index[Display_row];
      long long int index = 0;
      // end_index is the next line at a depth same as or lower than start_index
      int initial_depth = Trace_stream->past_lines.at(start_index).depth;
      for (index = start_index+1; index < SIZE(Trace_stream->past_lines); pre { line-height: 125%; }
td.linenos .normal { color: inherit; background-color: transparent; padding-left: 5px; padding-right: 5px; }
span.linenos { color: inherit; background-color: transparent; padding-left: 5px; padding-right: 5px; }
td.linenos .special { color: #000000; background-color: #ffffc0; padding-left: 5px; padding-right: 5px; }
span.linenos.special { color: #000000; background-color: #ffffc0; padding-left: 5px; padding-right: 5px; }
.highlight .hll { background-color: #ffffcc }
.highlight .c { color: #888888 } /* Comment */
.highlight .err { color: #a61717; background-color: #e3d2d2 } /* Error */
.highlight .k { color: #008800; font-weight: bold } /* Keyword */
.highlight .ch { color: #888888 } /* Comment.Hashbang */
.highlight .cm { color: #888888 } /* Comment.Multiline */
.highlight .cp { color: #cc0000; font-weight: bold } /* Comment.Preproc */
.highlight .cpf { color: #888888 } /* Comment.PreprocFile */
.highlight .c1 { color: #888888 } /* Comment.Single */
.highlight .cs { color: #cc0000; font-weight: bold; background-color: #fff0f0 } /* Comment.Special */
.highlight .gd { color: #000000; background-color: #ffdddd } /* Generic.Deleted */
.highlight .ge { font-style: italic } /* Generic.Emph */
.highlight .ges { font-weight: bold; font-style: italic } /* Generic.EmphStrong */
.highlight .gr { color: #aa0000 } /* Generic.Error */
.highlight .gh { color: #333333 } /* Generic.Heading */
.highlight .gi { color: #000000; background-color: #ddffdd } /* Generic.Inserted */
.highlight .go { color: #888888 } /* Generic.Output */
.highlight .gp { color: #555555 } /* Generic.Prompt */
.highlight .gs { font-weight: bold } /* Generic.Strong */
.highlight .gu { color: #666666 } /* Generic.Subheading */
.highlight .gt { color: #aa0000 } /* Generic.Traceback */
.highlight .kc { color: #008800; font-weight: bold } /* Keyword.Constant */
.highlight .kd { color: #008800; font-weight: bold } /* Keyword.Declaration */
.highlight .kn { color: #008800; font-weight: bold } /* Keyword.Namespace */
.highlight .kp { color: #008800 } /* Keyword.Pseudo */
.highlight .kr { color: #008800; font-weight: bold } /* Keyword.Reserved */
.highlight .kt { color: #888888; font-weight: bold } /* Keyword.Type */
.highlight .m { color: #0000DD; font-weight: bold } /* Literal.Number */
.highlight .s { color: #dd2200; background-color: #fff0f0 } /* Literal.String */
.highlight .na { color: #336699 } /* Name.Attribute */
.highlight .nb { color: #003388 } /* Name.Builtin */
.highlight .nc { color: #bb0066; font-weight: bold } /* Name.Class */
.highlight .no { color: #003366; font-weight: bold } /* Name.Constant */
.highlight .nd { color: #555555 } /* Name.Decorator */
.highlight .ne { color: #bb0066; font-weight: bold } /* Name.Exception */
.highlight .nf { color: #0066bb; font-weight: bold } /* Name.Function */
.highlight .nl { color: #336699; font-style: italic } /* Name.Label */
.highlight .nn { color: #bb0066; font-weight: bold } /* Name.Namespace */
.highlight .py { color: #336699; font-weight: bold } /* Name.Property */
.highlight .nt { color: #bb0066; font-weight: bold } /* Name.Tag */
.highlight .nv { color: #336699 } /* Name.Variable */
.highlight .ow { color: #008800 } /* Operator.Word */
.highlight .w { color: #bbbbbb } /* Text.Whitespace */
.highlight .mb { color: #0000DD; font-weight: bold } /* Literal.Number.Bin */
.highlight .mf { color: #0000DD; font-weight: bold } /* Literal.Number.Float */
.highlight .mh { color: #0000DD; font-weight: bold } /* Literal.Number.Hex */
.highlight .mi { color: #0000DD; font-weight: bold } /* Literal.Number.Integer */
.highlight .mo { color: #0000DD; font-weight: bold } /* Literal.Number.Oct */
.highlight .sa { color: #dd2200; background-color: #fff0f0 } /* Literal.String.Affix */
.highlight .sb { color: #dd2200; background-color: #fff0f0 } /* Literal.String.Backtick */
.highlight .sc { color: #dd2200; background-color: #fff0f0 } /* Literal.String.Char */
.highlight .dl { color: #dd2200; background-color: #fff0f0 } /* Literal.String.Delimiter */
.highlight .sd { color: #dd2200; background-color: #fff0f0 } /* Literal.String.Doc */
.highlight .s2 { color: #dd2200; background-color: #fff0f0 } /* Literal.String.Double */
.highlight .se { color: #0044dd; background-color: #fff0f0 } /* Literal.String.Escape */
.highlight .sh { color: #dd2200; background-color: #fff0f0 } /* Literal.String.Heredoc */
.highlight .si { color: #3333bb; background-color: #fff0f0 } /* Literal.String.Interpol */
.highlight .sx { color: #22bb22; background-color: #f0fff0 } /* Literal.String.Other */
.highlight .sr { color: #008800; background-color: #fff0ff } /* Literal.String.Regex */
.highlight .s1 { color: #dd2200; background-color: #fff0f0 } /* Literal.String.Single */
.highlight .ss { color: #aa6600; background-color: #fff0f0 } /* Literal.String.Symbol */
.highlight .bp { color: #003388 } /* Name.Builtin.Pseudo */
.highlight .fm { color: #0066bb; font-weight: bold } /* Name.Function.Magic */
.highlight .vc { color: #336699 } /* Name.Variable.Class */
.highlight .vg { color: #dd7700 } /* Name.Variable.Global */
.highlight .vi { color: #3333bb } /* Name.Variable.Instance */
.highlight .vm { color: #336699 } /* Name.Variable.Magic */
.highlight .il { color: #0000DD; font-weight: bold } /* Literal.Number.Integer.Long */
//: The bedrock level 1 of abstraction is now done, and we're going to start
//: building levels above it that make programming in x86 machine code a
//: little more ergonomic.
//:
//: All levels will be "pass through by default". Whatever they don't
//: understand they will silently pass through to lower levels.
//:
//: Since raw hex bytes of machine code are always possible to inject, SubX is
//: not a language, and we aren't building a compiler. This is something
//: deliberately leakier. Levels are more for improving auditing, checks and
//: error messages rather than for hiding low-level details.

//: Translator workflow: read 'source' file. Run a series of transforms on it,
//: each passing through what it doesn't understand. The final program should
//: be just machine code, suitable to write to an ELF binary.
//:
//: Higher levels usually transform code on the basis of metadata.

:(before "End Main")
if (is_equal(argv[1], "translate")) {
  START_TRACING_UNTIL_END_OF_SCOPE;
  reset();
  // Begin subx translate
  program p;
  string output_filename;
  for (int i = /*skip 'subx translate'*/2;  i < argc;  ++i) {
    if (is_equal(argv[i], "-o")) {
      ++i;
      if (i >= argc) {
        print_translate_usage();
        cerr << "'-o' must be followed by a filename to write results to\n";
        exit(1);
      }
      output_filename = argv[i];
    }
    else {
      ifstream fin(argv[i]);
      if (!fin) {
        cerr << "could not open " << argv[i] << '\n';
        return 1;
      }
      parse(fin, p);
      if (trace_contains_errors()) return 1;
    }
  }
  if (p.segments.empty()) {
    print_translate_usage();
    cerr << "nothing to do; must provide at least one file to read\n";
    exit(1);
  }
  if (output_filename.empty()) {
    print_translate_usage();
    cerr << "must provide a filename to write to using '-o'\n";
    exit(1);
  }
  transform(p);
  if (trace_contains_errors()) return 1;
  save_elf(p, output_filename);
  if (trace_contains_errors()) {
    unlink(output_filename.c_str());
    return 1;
  }
  // End subx translate
  return 0;
}

:(code)
void print_translate_usage() {
  cerr << "Usage: subx translate file1 file2 ... -o output\n";
}

// write out a program to a bare-bones ELF file
void save_elf(const program& p, const string& filename) {
  ofstream out(filename.c_str(), ios::binary);
  write_elf_header(out, p);
  for (size_t i = 0;  i < p.segments.size();  ++i)
    write_segment(p.segments.at(i), out);
  out.close();
}

void write_elf_header(ostream& out, const program& p) {
  char c = '\0';
#define O(X)  c = (X); out.write(&c, sizeof(c))
// host is required to be little-endian
#define emit(X)  out.write(reinterpret_cast<const char*>(&X), sizeof(X))
  //// ehdr
  // e_ident
  O(0x7f); O(/*E*/0x45); O(/*L*/0x4c); O(/*F*/0x46);
    O(0x1);  // 32-bit format
    O(0x1);  // little-endian
    O(0x1); O(0x0);
  for (size_t i = 0;  i < 8;  ++i) { O(0x0); }
  // e_type
  O(0x02); O(0x00);
  // e_machine
  O(0x03); O(0x00);
  // e_version
  O(0x01); O(0x00); O(0x00); O(0x00);
  // e_entry
  int e_entry = p.segments.at(0).start;  // convention
  emit(e_entry);
  // e_phoff -- immediately after ELF header
  int e_phoff = 0x34;
  emit(e_phoff);
  // e_shoff; unused
  int dummy32 = 0;
  emit(dummy32);
  // e_flags; unused
  emit(dummy32);
  // e_ehsize
  uint16_t e_ehsize = 0x34;
  emit(e_ehsize);
  // e_phentsize
  uint16_t e_phentsize = 0x20;
  emit(e_phentsize);
  // e_phnum
  uint16_t e_phnum = SIZE(p.segments);
  emit(e_phnum);
  // e_shentsize
  uint16_t dummy16 = 0x0;
  emit(dummy16);
  // e_shnum
  emit(dummy16);
  // e_shstrndx
  emit(dummy16);

  uint32_t p_offset = /*size of ehdr*/0x34 + SIZE(p.segments)*0x20/*size of each phdr*/;
  for (int i = 0;  i < SIZE(p.segments);  ++i) {
    //// phdr
    // p_type
    uint32_t p_type = 0x1;
    emit(p_type);
    // p_offset
    emit(p_offset);
    // p_vaddr
    uint32_t p_start = p.segments.at(i).start;
    emit(p_start);
    // p_paddr
    emit(p_start);
    // p_filesz
    uint32_t size = num_words(p.segments.at(i));
    assert(p_offset + size < SEGMENT_ALIGNMENT);
    emit(size);
    // p_memsz
    emit(size);
    // p_flags
    uint32_t p_flags = (i == 0) ? /*r-x*/0x5 : /*rw-*/0x6;  // convention: only first segment is code
    emit(p_flags);

    // p_align
    // "As the system creates or augments a process image, it logically copies
    // a file's segment to a virtual memory segment.  When—and if— the system
    // physically reads the file depends on the program's execution behavior,
    // system load, and so on.  A process does not require a physical page
    // unless it references the logical page during execution, and processes
    // commonly leave many pages unreferenced. Therefore delaying physical
    // reads frequently obviates them, improving system performance. To obtain
    // this efficiency in practice, executable and shared object files must
    // have segment images whose file offsets and virtual addresses are
    // congruent, modulo the page size." -- http://refspecs.linuxbase.org/elf/elf.pdf (page 95)
    uint32_t p_align = 0x1000;  // default page size on linux
    emit(p_align);
    if (p_offset % p_align != p_start % p_align) {
      raise << "segment starting at 0x" << HEXWORD << p_start << " is improperly aligned; alignment for p_offset " << p_offset << " should be " << (p_offset % p_align) << " but is " << (p_start % p_align) << '\n' << end();
      return;
    }

    // prepare for next segment
    p_offset += size;
  }
#undef O
#undef emit
}

void write_segment(const segment& s, ostream& out) {
  for (int i = 0;  i < SIZE(s.lines);  ++i) {
    const vector<word>& w = s.lines.at(i).words;
    for (int j = 0;  j < SIZE(w);  ++j) {
      uint8_t x = hex_byte(w.at(j).data);  // we're done with metadata by this point
      out.write(reinterpret_cast<const char*>(&x), /*sizeof(byte)*/1);
    }
  }
}

uint32_t num_words(const segment& s) {
  uint32_t sum = 0;
  for (int i = 0;  i < SIZE(s.lines);  ++i)
    sum += SIZE(s.lines.at(i).words);
  return sum;
}

:(before "End Includes")
using std::ios;