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#!/usr/bin/env ruby
# Start Date: Sunday January 4, 2009
# Current Version: 1
# Author: Joseph Pecoraro
# Contact: joepeck02@gmail.com
# Decription: Grab certain lines of a file
# with a simple syntax (see usage). Silent
# usage useful for piping output and Pipe
# option for piping input into it

# Wrapper around functionality
class FileLines
	
	attr_accessor :lines, :stdin
	
	def initialize(options, filename=nil)
		if filename.nil?
			@stdin = true
			@lines = []
			while line = STDIN.gets
				@lines << line
			end
		else
			@stdin = false
			@lines = File.readlines(filename)
		end
		@silent = false
		parse_options(options)
	end
	
	def parse_options(options)
		options.each do |option|
			if option.match(/^-(-silent|s)$/)
				@silent = true
			end
		end
	end
	
	def parse(args)
		args.each do |arg|
			
			# String: all
			if m = arg.match( /^all$/ )
				print_lines(0, @lines.size)
			
			# Ranges: 3-7
			elsif m = arg.match( /^(\d+)-(\d+)$/ )
				lower = m[1].to_i
				upper = m[2].to_i
				lower = 1 if lower.zero? # 0 => 1
				print_lines( lower-1, upper-lower+1 ) if upper >= lower
				
			# Lookarounds: 3~7   <before_and_after>~<line>
			elsif m = arg.match( /^(\d+)?~(\d+)$/ )
				range  = m[1].nil? ? 2 : m[1].to_i
				lineno = m[2].to_i
				lower  = lineno-range
				lower  = 1 if lower < 0
				upper  = lineno + range
				print_lines( lower-1, upper-lower+1 )
				
			# Down: *7
			elsif m = arg.match( /^\*(\d+)$/ )
				lower = 1
				upper = m[1].to_i
				print_lines( lower-1, upper-lower+1 )
				
			# Up: 7*
			elsif m = arg.match( /^(\d+)\*$/ )
				lower = m[1].to_i
				upper = @lines.size
				print_lines( lower-1, upper-lower+1 )
				
			# Skipping 2:1/2   <offset>:<range>/<skip>
			elsif m = arg.match( /^((\d+):)?(\d+)\/(\d+)$/ )
				offset = m[2].nil? ? 1 : m[2].to_i
				range = m[3].to_i
				skip  = m[4].to_i
				print_with_skips(offset, range, skip)
				
			# Single Lines
			else
				lineno = arg.to_i
				lineno = 1 if lineno.zero? # 0 => 1
				lineno = lineno-1 if lineno > 0 # Handle Negatives
				print_line( lineno )
			end

		end
	end
	
	def print_lines(lower, upper)
		return if lower > @lines.size
		i = lower
		@lines[lower, upper].each do |line|
			if @silent
				puts line
			else
				puts "[#{i+1}]: #{line}"
			end
			i += 1
		end
	end
	
	def print_line(line)
		real = line>@lines.size ? @lines.size-1 : line
		if @silent
			puts @lines[real]
		else
			if line < 0
				puts "[#{real}]: #{@lines[real]}"
			else
				puts "[#{real+1}]: #{@lines[real]}"
			end
		end
	end
	
	def print_with_skips(offset, range, skip)
		offset = 1 if offset < 0
		range = 1 if range < 1
		skip = 1 if skip < 1
		cnt = 0
		lineno = offset-1
		skipping = false
		@lines[offset-1, @lines.size].each do |line|
			lineno += 1
			cnt += 1
			if skipping
				if cnt >= skip
					skipping = false
					cnt = 0
				end
				next
			else
				if cnt >= range
					skipping = true
					cnt = 1
				end
				if @silent
					puts line
				else
					puts "[#{lineno}]: #{line}"
				end
			end
		end
	end

end


# When run as as script
if $0 == __FILE__
	
	# Pull out the Options
	options = ARGV.select { |arg| arg.match(/-[a-z]/i) }
	ARGV.delete_if { |arg| arg.match(/-[a-z]/i) }
	
	# Special Handling for Pipes (don't require a filename)
	is_pipe = !STDIN.tty?

	# Check Cmd Line Args and Print Usage if needed
	if ARGV.size <= 1 && !is_pipe
		puts "usage: line [options] filename numbers"
		puts
		puts " options:"
		puts "   --silent or -s   Just print the line, without [#]"
		puts
		puts " number formats:"
		puts "   1-3              Prints lines 1 through 3"
		puts "   5                Prints line 5"
		puts "   -1               Prints the last line, (negative)"
		puts
		puts " extra formats:"
		puts "   all              Prints out all lines"
		puts "   ~5               Prints 2 (default) lines before and after 5"
		puts "   4~10             Prints 4 lines before and after 10"
		puts "   *7 or 8*         Prints all lines before or after the number"
		puts "   5/1              Prints 5 lines, then skips 1 line..."
		puts "   2:5/1            Starts at line 2, prints and skips..."
		puts
		exit 1
	end
		
	# Pipe Usage
	if is_pipe
		FileLines.new(options).parse(ARGV)		
	
	# Unreadable File
	elsif !File.readable?(ARGV[0])
		puts "line: file '#{ARGV[0]}' did not exist or was unreadable."
		exit 1

	# Run the Program
	else
		FileLines.new(options, ARGV[0]).parse(ARGV[1, ARGV.size])
	end

end