class Build::Files::Monitor::Polling

def add(handle)
	@logger.debug{"Adding handle: #{handle}"}
	
	handle.directories.each do |directory|
		# We want the full path as a plain string:
		directory = directory.to_s
		
		@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

def delay_deletions
	@deletions = []
	
	yield
	
	@deletions.each do |handle|
		purge(handle)
	end
	
	@deletions = nil
end

def delete(handle)
	if @deletions
		@logger.debug{"Delayed delete handle: #{handle}"}
		@deletions << handle
	else
		purge(handle)
	end
end

def initialize(logger: nil)
	@directories = Hash.new do |hash, key|
		hash[key] = Set.new
	end
	
	@updated = false
	
	@deletions = nil
	
	@logger = logger || Logger.new(nil)
end

def purge(handle)
	@logger.debug{"Purge handle: #{handle}"}
	
	handle.directories.each do |directory|
		directory = directory.to_s
		
		@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 roots
	@directories.keys
end

def run(**options, &block)
	catch(:interrupt) do
		while true
			monitor.update(monitor.roots)
			
			yield
			
			sleep(options[:latency] || 1.0)
		end
	end
end

def track_changes(files, &block)
	handle = Handle.new(self, files, &block)
	
	add(handle)
end

def update(directories, *args)
	@logger.debug{"Update: #{directories} #{args.inspect}"}
	
	delay_deletions do
		directories.each do |directory|
			@logger.debug{"Directory: #{directory}"}
			
			@directories[directory].each do |handle|
				@logger.debug{"Handle changed: #{handle.inspect}"}
				
				# Changes here may not actually require an update to the handle:
				handle.changed!(*args)
			end
		end
	end
end