#!/usr/bin/env ruby
# Start Date: Sunday December 2, 2007 (v0.9)
# Most Recent Update: Saturday January 26, 2008
# Current Version: 1.2
# Author: Joseph Pecoraro
# Contact: joepeck02@gmail.com
# Decription: Default behavior is a multi-line search and replace utility that
#  uses a regular expression for searching and allows back references to 
#  captured groups from the pattern to appear in the replacement text

# Global States
line_processing = false
case_sensitive = false
global_replace = true
modify_original = false

# Usage Message to print
$program_name = $0.split(/\//).last
usage = <<USAGE
usage: #{$program_name} [options] find replace [filenames]
       #{$program_name} [options] s/find/replace/ [filenames]
  find      - a regular expression to be run on the entire file as one string
  replace   - replacement text, \\1-\\9 and metachars (\\n, etc.) are allowed
  filenames - names of the input files to be parsed, if blank uses STDIN
  
options:
  --line or -l    process line by line instead of all at once (not default)
  --case or -c    makes the regular expression case sensitive (not default)
  --global or -g  process all occurrences in the text (default)
  --modify or -m  changes will directly modify the original file (not default)

negated options are done by adding 'not' or 'n' in switches like so:
  --notline or -nl

special note:
  When using bash, if you want backslashes in the replace portion make sure
  to use the multiple argument usage with single quotes for the replacement.

example usage:
  Replace all a's with e's
  #{$program_name} s/a/e/ file
  #{$program_name} a e file

  Doubles the last character on each line and doubles the newline.
  #{$program_name} "(.)\\n" "\\1\\1\\n\\n" file

USAGE

# Print an error message and exit
def err(msg)  
  puts "#{$program_name}: #{msg}"
  exit 1
end

# Possible Switches
ARGV.each_index do |i|
  arg = ARGV[i]
  if arg[0] == ?- then
    case arg
      when "--line"     , "-l"  then line_processing = true
      when "--notline"  , "-nl" then line_processing = false
      when "--case"     , "-c"  then case_sensitive = true
      when "--notcase"  , "-nc" then case_sensitive = false
      when "--global"   , "-g"  then global_replace = true
      when "--notglobal", "-ng" then global_replace = false
      when "--modify"   , "-m"  then modify_original = true
      when "--notmodify", "-nm" then modify_original = false
      else err("illegal option #{arg}")
    end
  end
end

# Remove the Switches from ARGV
ARGV.delete_if { |elem| elem[0] == ?- }

# Check if it is quick mode (meaning cmdline argument is s/find/replace/)
find_str = find = replace = filename = nil
if ARGV.first =~ /^s\/(.*)?\/(.*)?\/(\w*)?$/
  find_str = $1
  replace = $2
  first_filename = 1
  ARGV << nil if ARGV.size == 1
  
# Not Quick Mode, Arguments are seperate on the cmdline
elsif ARGV.size >= 2
  find_str = ARGV[0]
  replace = ARGV[1].dup
  first_filename = 2
  ARGV << nil if ARGV.size == 2
  
  # User is allowed to wrap the find regex in /'s (this removes them)
  find_str = find_str[1..(find_str.length-2)] if find_str =~ /^\/.*?\/$/

# Bad Arguments, show usage
else
  puts usage
  exit 1
end

# Make find_str into a Regexp object
if case_sensitive
  find = Regexp.new( find_str )
else
  find = Regexp.new( find_str, Regexp::IGNORECASE )
end

# Map metacharacters in the replace portion
replace.gsub!(/\\[\\ntrvfbae]/) do |match|
  case match
    when "\\\\" then match = "\\" # A backslash
    when "\\n"  then match = "\n" # Newline
    when "\\t"  then match = "\t" # Tab
    when "\\r"  then match = "\r" # Carriage Return
    when "\\v"  then match = "\v" # Vertical Tab
    when "\\f"  then match = "\f" # Formfeed
    when "\\b"  then match = "\b" # Backspace
    when "\\a"  then match = "\a" # Bell
    when "\\e"  then match = "\e" # Escape
  end
end

# Loop through all the filenames doing the find/replace
first_filename.upto(ARGV.size-1) do |i|
  
  # Check for Possible File Errors or if the filename is nil make it STDIN
  filename = ARGV[i]
  unless filename.nil?
    if !File.exist? filename
      err("#{filename}: No such file")
    elsif File.directory? filename
      err("#{filename}: This is a directory, not a file.")
    elsif !File.readable? filename
      err("#{filename}: File is not readable by this user.")
    elsif !File.writable? filename
      err("#{filename}: File is not writable by this user.")
    end
  else
    filename = STDIN.fileno
  end

  # Setup the stream to print to
  if modify_original && filename != STDIN.fileno then
    temp_filename = filename + '.tmp'
    stream = File.new(temp_filename, File::CREAT|File::TRUNC|File::RDWR, 0644)
  else
    stream = STDOUT
  end

  # Default Behavior (and basicically what they all do)
  # 1. Open the file
  # 2. Read text as 1 big sting (memory intensive) or Line by Line
  # 3. Run the Find/Replace globally or non-globally
  # 4. Print the result to a stream
  if line_processing and global_replace then
    File.new(filename).readlines.each { |line| stream.puts line.gsub(find,replace) }
  elsif line_processing and !global_replace then
    File.new(filename).readlines.each { |line| stream.puts line.sub(find,replace) }
  elsif !line_processing and global_replace
    stream.puts File.new(filename).read.gsub(find,replace)
  else
    stream.puts File.new(filename).read.sub(find,replace)
  end

  # If the stream was a temp file then clean up
  if modify_original && filename != STDIN.fileno then
    stream.close
    File.rename(temp_filename, filename)
  end

end
  
# Successful
exit 0