# Copyright, 2014, by Samuel G. D. Williams. <http://www.codeotaku.com>
# 
# 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 'set'

require 'build/files/state'

module Build
	module Files
		class Monitor
			def initialize
				@directories = Hash.new { |hash, key| hash[key] = Set.new }
				
				@updated = false
			end
			
			attr :updated
			
			# Notify the monitor that files in these directories have changed.
			def update(directories, *args)
				directories.each do |directory|
					# directory = File.realpath(directory)
					
					@directories[directory].each do |handle|
						handle.changed!(*args)
					end
				end
			end
	
			def roots
				@directories.keys
			end
	
			def delete(handle)
				handle.directories.each do |directory|
					@directories[directory].delete(handle)
			
					# Remove the entire record if there are no handles:
					if @directories[directory].size == 0
						@directories.delete(directory)
				
						@updated = true
					end
				end
			end
	
			def track_changes(files, &block)
				handle = Handle.new(self, files, &block)
		
				add(handle)
			end
	
			def add(handle)
				handle.directories.each do |directory|
					@directories[directory] << handle
			
					# We just added the first handle:
					if @directories[directory].size == 1
						# If the handle already existed, this might trigger unnecessarily.
						@updated = true
					end
				end
		
				handle
			end
		end
		
		def self.run_with_fsevent(monitor, options = {}, &block)
			require 'rb-fsevent'
			
			fsevent ||= FSEvent.new
			
			catch(:interrupt) do
				while true
					fsevent.watch monitor.roots do |directories|
						monitor.update(directories)
				
						yield
				
						if monitor.updated
							fsevent.stop
						end
					end
			
					fsevent.run
				end
			end
		end
		
		def self.run_with_polling(monitor, options = {}, &block)
			catch(:interrupt) do
				while true
					monitor.update(monitor.roots)
			
					yield
			
					sleep(options[:latency] || 5.0)
				end
			end
		end
		
		def run(monitor, options = {}, &block)
			self.class.run_with_polling(monitor, options, &block)
		end
	end
end