# 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.

module Build
	module Files
		# Represents a specific file on disk with a specific mtime.
		class FileTime
			include Comparable
		
			def initialize(path, time)
				@path = path
				@time = time
			end
		
			attr :path
			attr :time
		
			def <=> other
				@time <=> other.time
			end
			
			def inspect
				"<FileTime #{@path.inspect} #{@time.inspect}>"
			end
		end
		
		class State
			def initialize(files)
				raise ArgumentError.new("Invalid files list: #{files}") unless Files::List === files
			
				@files = files
		
				@times = {}
			
				update!
			end
	
			attr :files
	
			attr :added
			attr :removed
			attr :changed
			attr :missing
		
			attr :times
		
			def update!
				last_times = @times
				@times = {}
			
				@added = []
				@removed = []
				@changed = []
				@missing = []
			
				file_times = []
				
				@files.each do |path|
					# When processing the same path twice (perhaps by accident), we should skip it otherwise it might cause issues when being deleted from last_times multuple times.
					next if @times.include? path
					
					if File.exist?(path)
						modified_time = File.mtime(path)
					
						if last_time = last_times.delete(path)
							# Path was valid last update:
							if modified_time != last_time
								@changed << path
								# puts "Changed: #{path}"
							end
						else
							# Path didn't exist before:
							@added << path
							# puts "Added: #{path}"
						end
					
						@times[path] = modified_time
					
						unless File.directory?(path)
							file_times << FileTime.new(path, modified_time)
						end
					else
						@missing << path
						# puts "Missing: #{path}"
					end
				end
				
				@removed = last_times.keys
				
				@oldest_time = file_times.min
				@newest_time = file_times.max
				
				return @added.size > 0 || @changed.size > 0 || @removed.size > 0 || @missing.size > 0
			end
			
			attr :oldest_time
			attr :newest_time
			
			attr :missing
			
			def missing?
				!@missing.empty?
			end
			
			# Outputs is a list of full paths and must not include any patterns/globs.
			def intersects?(outputs)
				@files.intersects?(outputs)
			end
			
			def empty?
				@files.to_a.empty?
			end
			
			def inspect
				"<State Added:#{@added} Removed:#{@removed} Changed:#{@changed} Missing:#{@missing}>"
			end
		end
	
		class IOState
			def initialize(inputs, outputs)
				@input_state = State.new(inputs)
				@output_state = State.new(outputs)
			end
			
			attr :input_state
			attr :output_state
			
			# Output is dirty if files are missing or if latest input is older than any output.
			def dirty?
				@dirty = []
				
				if @output_state.missing?
					# puts "Output file missing: #{output_state.missing.inspect}"
					
					return true
				end
				
				# If there are no inputs, we are always clean as long as outputs exist:
				# if @input_state.empty?
				#	return false
				# end
				
				oldest_output_time = @output_state.oldest_time
				newest_input_time = @input_state.newest_time
				
				if newest_input_time and oldest_output_time
					# if newest_input_time > oldest_output_time
					#	puts "Out of date file: #{newest_input_time.inspect} > #{oldest_output_time.inspect}"
					# end
					
					return newest_input_time > oldest_output_time
				end
				
				# puts "Missing file dates: #{newest_input_time.inspect} < #{oldest_output_time.inspect}"
				
				return true
			end
			
			def fresh?
				not dirty?
			end
			
			def files
				@input_state.files + @output_state.files
			end
			
			def added
				@input_state.added + @output_state.added
			end
			
			def removed
				@input_state.removed + @output_state.removed
			end
			
			def changed
				@input_state.changed + @output_state.changed
			end
			
			def update!
				input_changed = @input_state.update!
				output_changed = @output_state.update!
			
				input_changed or output_changed
			end
			
			def intersects?(outputs)
				@input_state.intersects?(outputs) or @output_state.intersects?(outputs)
			end
			
			def inspect
				"<IOState Input:#{@input_state.inspect} Output:#{@output_state.inspect}>"
			end
		end
	
		class Handle
			def initialize(monitor, files, &block)
				@monitor = monitor
				@state = State.new(files)
				@on_changed = block
			end
		
			attr :monitor
		
			def commit!
				@state.update!
			end
		
			def directories
				@state.files.roots
			end
		
			def remove!
				monitor.delete(self)
			end
		
			def changed!
				@on_changed.call(@state) if @state.update!
			end
		end
	end
end