highlight

#!/usr/bin/env ruby

# Author:  Fraser Hanson
# Date:    2010-09
# Purpose: Highlight strings in the input.  
#          Grep color highlighting without the grepping.
# FIXME:
#   -error handling: no such file, no input given, no targets specified,
#    only one non-flag arg but no input, not enough colors, etc.

#     Options (such as i for case-insensitivity) may be passed to the s///
#     operator by specifying them as flags on the command line (eg. "-i" =>
#     s///i).

############################################################

require 'pp'
require 'stringio'

usage =<<EOF
usage:
    #{File.basename($0)} [options] pattern [ pattern ... ] [filename]

    Purpose: highlights in a bright color all occurrences of the string
    "pattern" inside "text", which is usually coming from a pipe.  

    If no input is piped in, then the last argument is assumed to be a
    filename.

    Options:
        -i			    case insensitive 
        -s			    use same colour for all patterns
        --colour=n	specify starting colour (as an integer)
        -w          highlight every word
        -f <file>   take patterns from lines of a file

EOF

# Special escaped strings to surround any text with to highlight it.
$Normal    = "\033[0m";
$Colorfmt  = "\033[1;%sm"
$color     = 31
$colors    = Hash.new
$same_color = false

############################################################

# highlight with case sensitive match
def highlight_line(string)
	$targets.each do |t|
	
		# match case insensitive if asked nicely
		if $options.match(/i/)
			re = Regexp.compile(t, true)
		else
			re = Regexp.compile(t, false)
		end

		# surround each match with terminal color control chars
		string.gsub!(re) do |s|
			"%s%s%s" % [get_color(t), $&, $Normal]
		end
	end

	string
end

# given a target string, return the assigned color for that target
def get_color(string)
	if $colors[string].nil?
		$colors[string] = $Colorfmt % $color
    unless $same_color
      $color += 1 
    end
	end
	$colors[string]
end
############################################################

# Just bail out if output is not to a tty.
exec "cat" unless $stdout.tty?

# Dump the command line flags into a string, targets into an array
$options = String.new
$targets = Array.new
parsing = :options
ARGV.each do |a|
	if "-" != a[0].chr
		parsing = :targets
	end
		
	if :options == parsing
		$options << a
	else
		$targets << a
	end
end

## # DEBUG output
## puts "Options: %s" % $options
## puts "Targets: [%s]" % $targets.join("] [")

# Print usage msg and die sometimes
if $options.match(/-h\>/) or 0 == ARGV.size
	puts usage
	exit
elsif $options.match(/--colou?r=(\d+)/)
	$color = $1.to_i
elsif $options.match(/-s\b/)
	$same_color = true
elsif $options.match(/-w\b/)
  ARGV.delete("-w")
	$every_word = true
elsif $options.match(/-f\s+([\S]+)/)
  ARGV.delete("-f")
	$pattern_file = $1
end

text = nil
if $every_word == true
  text = ARGF.read
  $targets = text.split.sort.uniq
elsif ! $pattern_file.nil?
  $targets = IO.readlines($pattern_file)
end


# Call get_color for each target in order.
# This is needed so that the assigned colour will depend on the order
# the targets are specified in on the cmd line, rather than the order
# they appear in the output.  This is convenient because the colours
# previously in use stay the same if you re-run highlight on the same input 
# with added arguments.
$targets.each do |target|
	get_color(target)
end

# FIXME: targets that are subsets of other targets mess this up.
# Even if the longer target is already highlighted, the smaller target will be
# highlighted too, leading to nested ANSI escape sequences, which does not
# work.
# Examples:
# Compare this:
#     echo -e 'dog o\nwood dowry wooden' | highlight.rb dog wood dowry
# With this:
#     echo -e 'dog o\nwood dowry wooden' | highlight.rb dog wood dowry o

# Get input lines from $stdin if possible.  
# Otherwise, assume the last argument is a filename to process.
lines = Array.new
if $every_word
  # Already read STDIN
  io = StringIO.new(text)
else
  if $stdin.tty?
    io = File.open($targets.pop)
  else
    io = $stdin
  end
end

begin
	while (line = io.readline)

		# Highlight and print each line
		line = highlight_line(line)
		puts line

	end

rescue EOFError, Interrupt, Errno::EPIPE
end