#! /usr/bin/gawk -f
# Last edited on 2004-02-07 04:56:45 by stolfi

BEGIN {
  # Lists occurrences of a pattern with context 
  if (pat == "") { arg_error("must specify \"pat\""); }
  if (sep == "") { sep = "|"; }
}

/^[ ]*([\#@]|$)/ { next; }

/./ { 
  lin = $0;
  # Replace inlined @{}{}-constructs by their text content:
  lin = gensub(/[@][{][^{}]*[}][{]([^{}]*)[}]/, "\\1", "g", lin); 
  # Remove {}-comments:
  gsub(/[{][^{}]*[}]/, "", lin); 
  # Continue processing:
  $0 = lin;
}

(match($0, pat)) {
  lin = $0;
  a = substr(lin, 1, RSTART-1);
  b = substr(lin, RSTART, RLENGTH);
  c = substr(lin, RSTART+RLENGTH);
  nb = length(b);
  wa = int((80 - nb)/2);
  wc = 80 - wa - nb;
  printf "%*s%s%s%s%s\n", wa, substr(a, length(a)+1-wa), sep, b, sep, substr(c, 1, wc); 
  next;
}

function arg_error(msg)
{
  printf "%d: %s\n", FNR, msg > "/dev/stderr";
  exit 1;
}