#
# Author:: Nuo Yan (<nuo@opscode.com>)
# Copyright:: Copyright (c) 2009 Opscode, Inc.
# License:: Apache License, Version 2.0
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
# 
#     http://www.apache.org/licenses/LICENSE-2.0
# 
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

require 'ftools'
require 'fileutils'
require 'tempfile'

class Chef
	class Util
		class FileEdit

			private
			
			attr_accessor :original_pathname, :contents, :file_edited

			public
			
			def initialize(filepath)
				@original_pathname = filepath
				@file_edited = false
				
				raise ArgumentError, "File doesn't exist" unless File.exist? @original_pathname
				raise ArgumentError, "File is blank" unless (@contents = File.new(@original_pathname).readlines).length > 0
			end
			
			#search the file line by line and match each line with the given regex
			#if matched, replace the whole line with newline.
			def search_file_replace_line(regex, newline)
				search_match(regex, newline, 'r', 1)
			end

			#search the file line by line and match each line with the given regex
			#if matched, replace the match (all occurances)  with the replace parameter
			def search_file_replace(regex, replace)
				search_match(regex, replace, 'r', 2)
			end
			
			#search the file line by line and match each line with the given regex
			#if matched, delete the line
			def search_file_delete_line(regex)
				search_match(regex, " ", 'd', 1)
			end
			
			#search the file line by line and match each line with the given regex
			#if matched, delete the match (all occurances) from the line
			def search_file_delete(regex)
				search_match(regex, " ", 'd', 2)
			end

			#search the file line by line and match each line with the given regex
			#if matched, insert newline after each matching line
			def insert_line_after_match(regex, newline)
				search_match(regex, newline, 'i', 0)
			end
			 
			#Make a copy of old_file and write new file out (only if file changed)
			def write_file
				
				# file_edited is false when there was no match in the whole file and thus no contents have changed.
				if file_edited
					backup_pathname = original_pathname + ".old"
					File.copy(original_pathname, backup_pathname)
					Tempfile.open("w") do |newfile|
						contents.each do |line|
							newfile.puts(line)
						end
						newfile.flush
						FileUtils.mv(newfile.path, original_pathname)
					end
				end
				self.file_edited = false

			end
			
			private
			
			#helper method to do the match, replace, delete, and insert operations
			#command is the switch of delete, replace, and insert ('d', 'r', 'i')
			#method is to control operation on whole line or only the match (1 for line, 2 for match)
			def search_match(regex, replace, command, method)
				
				#convert regex to a Regexp object (if not already is one) and store it in exp.
				exp = Regexp.new(regex)

				#loop through contents and do the appropriate operation depending on 'command' and 'method'
				new_contents = []
				
				contents.each do |line|
					if line.match(exp) 
						self.file_edited = true
						case
						when command == 'r'
							new_contents << ((method == 1) ? replace : line.gsub!(exp, replace))
						when command == 'd'
							if method == 2
								new_contents << line.gsub!(exp, "")
							end
						when command == 'i'
							new_contents << line
							new_contents << replace
						end
					else
						new_contents << line
					end
				end

				self.contents = new_contents
			end
		end
	end
end