#  Phusion Passenger - http://www.modrails.com/
#  Copyright (c) 2010 Phusion
#
#  "Phusion Passenger" is a trademark of Hongli Lai & Ninh Bui.
#
#  Permission is hereby granted, free of charge, to any person obtaining a copy
#  of this software and associated documentation files (the "Software"), to deal
#  in the Software without restriction, including without limitation the rights
#  to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
#  copies of the Software, and to permit persons to whom the Software is
#  furnished to do so, subject to the following conditions:
#
#  The above copyright notice and this permission notice shall be included in
#  all copies or substantial portions of the Software.
#
#  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
#  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
#  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
#  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
#  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
#  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
#  THE SOFTWARE.

require 'phusion_passenger/native_support'

module PhusionPassenger
module Utils

# Watches changes on one or more files or directories. To use this class,
# construct an object, passing it file or directory names to watch, then
# call #wait_for_change. #wait_for_change waits until one of the following
# events has happened since the constructor was called:
#
# - One of the specified files has been renamed, deleted, or its access
#   revoked. This will cause +true+ to be returned.
# - One of the specified directories has been modified, renamed, deleted,
#   or its access revoked. This will cause +true+ to be returned.
# - +termination_pipe+ (as passed to the constructor) becomes readable.
#   This will cause +nil+ to be returned.
# - The thread is interrupted. This will cause +nil+ to be returned.
# 
# The constructor will attempt to stat and possible also open all specified
# files/directories. If one of them cannot be statted or opened, then
# +false+ will be returned by #wait_for_change.
#
# #wait_for_change may only be called once. After calling it one should
# create a new object if one wishes to watch the filesystem again.
#
# Always call #close when a FileSystemWatcher object is no longer needed
# in order to free resources.
#
# This class tries to use kqueue for efficient filesystem watching on
# platforms that support it. On other platforms it'll fallback to stat
# polling instead.

if defined?(NativeSupport::FileSystemWatcher)
	FileSystemWatcher = NativeSupport::FileSystemWatcher
	
	FileSystemWatcher.class_eval do
		def self.new(filenames, termination_pipe = nil)
			# Default parameter values, type conversion and exception
			# handling in C is too much of a pain.
			filenames = filenames.map do |filename|
				filename.to_s
			end
			return _new(filenames, termination_pipe)
		end
		
		def self.opens_files?
			return true
		end
	end
else
	class FileSystemWatcher
		attr_accessor :poll_interval
		
		def self.opens_files?
			return false
		end
		
		def initialize(filenames, termination_pipe = nil)
			@poll_interval = 3
			@termination_pipe = termination_pipe
			@dirs  = []
			@files = []
		
			begin
				filenames.each do |filename|
					stat = File.stat(filename)
					if stat.directory?
						@dirs << DirInfo.new(filename, stat)
					else
						@files << FileInfo.new(filename, stat)
					end
				end
			rescue Errno::EACCES, Errno::ENOENT
				@dirs = @files = nil
			end
		end
		
		def wait_for_change
			if !@dirs
				return false
			end
			
			while true
				if changed?
					return true
				elsif select([@termination_pipe], nil, nil, @poll_interval)
					return nil
				end
			end
		end
	
		def close
		end
		
	private
		class DirInfo
			DOT    = "."
			DOTDOT = ".."
			
			def initialize(filename, stat)
				@filename = filename
				@stat = stat
				@subfiles = {}
				Dir.foreach(filename) do |entry|
					next if entry == DOT || entry == DOTDOT
					subfilename = "#{filename}/#{entry}"
					@subfiles[entry] = FileInfo.new(subfilename, File.stat(subfilename))
				end
			end
			
			def changed?
				new_stat = File.stat(@filename)
				if @stat.ino != new_stat.ino || !new_stat.directory? || @stat.mtime != new_stat.mtime
					return true
				end
				
				count = 0
				Dir.foreach(@filename) do |entry|
					next if entry == DOT || entry == DOTDOT
					subfilename = "#{@filename}/#{entry}"
				
					file_info = @subfiles[entry]
					if !file_info || file_info.changed?(false)
						return true
					else
						count += 1
					end
				end
				
				return count != @subfiles.size
			rescue Errno::EACCES, Errno::ENOENT
				return true
			end
		end
		
		class FileInfo
			def initialize(filename, stat)
				@filename = filename
				@stat = stat
			end
			
			def changed?(check_mtime = true)
				new_stat = File.stat(@filename)
				if check_mtime
					mtime_changed = @stat.mtime != new_stat.mtime || @stat.size != new_stat.size
				else
					mtime_changed = false
				end
				return @stat.ino != new_stat.ino || @stat.ftype != new_stat.ftype || mtime_changed
			rescue Errno::EACCES, Errno::ENOENT
				return true
			end
		end
		
		def changed?
			return @dirs.any?  { |dir_info| dir_info.changed? } ||
			       @files.any? { |file_info| file_info.changed? }
		end
	end
end

end # module Utils
end # module PhusionPassenger
