require 'fileutils'
require 'iterator'

module Kernel
	def Path(str)
		Path === str ? str : Path.new(str)
	end
end

class String
	def to_path(separator="/")
		Path.new(self, separator)
	end
end

# you can use Path same as strings for hash-lookups, but not as keys
# Path is immutable
# FIXME: ::_load, #_dump for Marshal
class Path
	TruePattern = Object.new
	def TruePattern.===(other); true; end
	def TruePattern.=~(other); true; end

	include Comparable

	class <<self
		# returns the current working directory
		def current; new(Dir.getwd); end

		# returns the path of the current script (ENV["_"] if $0 doesn't exist)
		def program
			if File.exist?($0)
				new($0)
			elsif ENV.has_key?("_")
				new(ENV["_"])
			else
				nil
			end
		end

		# home environment variable if set, else nil
		def home
			ENV.has_key?("HOME") ? new(ENV["HOME"].to_str) : nil
		end
	end

	# always use "/" as separator, no matter on what platform
	def initialize(path, separator="/")
		raise ArgumentError, "Illegal null character in path #{path.inspect}" if /\0/ =~ path
		@pathname   = path.to_str
		@separator  = separator
		@segments   = @pathname.scan(/[^#{Regexp.escape(@separator)}]+/)
		@top        = (@segments.length == 0 ? @pathname : @pathname[0, @pathname.index(@segments[0])])
		taint if path.tainted?
	end

	# returns a String
	def pathname
		@pathname.dup
	end

	# returns a String
	def dirname
		File.dirname(@pathname)
	end

	# returns a String, if without_suffix is given (can be an array), it is removed
	def filename(without_suffix=nil)
		File.basename(@pathname, without_suffix)
	end
	alias name filename

	def extname
		File.extname(@pathname)
	end

	# returns a Path
	def path
		dup
	end

	# returns the Path of the containing directory
	def directory
		self.class.new(File.dirname(@pathname), @separator)
	end

	# returns the Path of the last segment, if without_suffix is
	# given (can be an array), it is removed
	def file(without_suffix=nil)
		self.class.new(File.basename(@pathname, without_suffix), @separator)
	end

	def segments
		@pathname.scan(/[^#{Regexp.escape(@separator)}]+/)
	end

	# checks whether two paths are refering the same file,
	# basically a.same_file?(b) is a short for Path(a).expanded.clean == Path(b).expanded.clean.
	# does not access file system, also see real_same?
	def same?(path, separator=@separator)
		expanded.clean == self.class.new(path, separator).expanded.clean
	end

	# checks if this path (assumed to be a directory) is base to other path
	# does not access file system, also see real_include?
	def include?(path, separator=@separator)
		self.class.new(path, separator).expanded.clean.index(expanded.clean) == 0
	end

	# checks whether two paths are refering the same file,
	# basically a.real_same_file?(b) is a short for Path(a).real == Path(b).real.
	# accesses file system, also see same?
	def real_same?(path, separator=@separator)
		real == self.class.new(path, separator).real
	end

	# checks if this path (must be a directory) is base to other path
	# accesses file system, also see include?
	def real_include?(path, separator=@separator)
		directory? && self.class.new(path, separator).real.index(real) == 0
	end

	# Path#+ appends a path fragment to this one to produce a new Path object.
	# also see Path#join
	#
	#   p1 = Path("/usr")       # <Path /usr>
	#   p2 = p1 + "bin/ruby"    # <Path /usr/bin/ruby>
	#   p3 = p1 + "../bin/ruby" # <Path /bin/ruby>
	#   p4 = p1 + "bin/../ruby" # <Path /usr/bin/../ruby>
	#   p5 = p1 + "/etc/passwd" # raises ArgumentError
	#
	# This method doesn't access the file system; it is pure string manipulation.
	def +(other)
		other    = other.to_str
		segments = other.scan(/[^#{Regexp.escape(@separator)}]+/)
		top      = (segments.length == 0 ? other : other[0, other.index(segments[0])])

		raise ArgumentError, "Can't append absolute path #{other.inspect}" unless top.empty?

		current     = @segments.dup
		while segments.last =~ /\A\.\.?\z/
			current.pop if segments.shift == ".."
		end
		self.class.new(@top + (current + segments).join(@separator), @separator)
	end

	def join(*others)
		self+others.join(@separator)
	end

	# returns start of the path if absolute, else nil
	# absolute paths start with either the path separator or <drive> ":" <path sep>
	# (windows' "C:\")
	def absolute?
		if @pathname =~ /\A([^#{Regexp.escape(@separator)}]+:#{Regexp.escape(@separator)})/ ||
			@pathname =~ /\A(#{Regexp.escape(@separator)})/ then
			$1
		else
			nil
		end
	end

	# returns true or false
	def relative?
		!absolute?
	end

	# true if file/directory exists and its size is zero or it's entries only . and ..
	def empty?
		if File.directory?(@pathname)
			Dir.entries(@pathname).all? { |x| x == '.' || x == '..' }
		else
			File.size(@pathname) == 0
		end
	end

	# prepends the current directory or home if path starts with ~
	def expanded
		absolute? ? dup : self.class.new(File.expand_path(@pathname), @separator)
	end

	def relative(to=self.class.current)
		to = self.class.new(to.to_str) unless to.class == self.class #to.respond_to?(:to_a) - to_a at the moment is implemented in Object, thus a useless test
		return dup if relative? && to == self.class.current
		segments = self.expanded.segments
		other    = to.expanded.segments
		while other[0] == segments[0] && other.length > 0
			other.shift
			segments.shift
		end
		segments.unshift(*([".."]*other.length))
		self.class.new(segments.join(@separator),@separator)
	end

	# Clean the path simply by resolving and removing excess "." and ".." entries.
	# Pure stringmanipulation.
	def clean(consider_symlink=false)
		if consider_symlink then
			cleanpath_conservative
		else
			cleanpath_aggressive
		end
	end

	# cleanpath_aggressive assumes:
	# * no symlink
	# * all path prefix contained in the path is existing directory
	def cleanpath_aggressive
		return self.class.new('', @separator) if @pathname == ''
		absolute = absolute?
		names    = []
		@segments.each { |name|
			next if name == '.'
			if name == '..'
				if names.empty?
					next if absolute
				else
					if names.last != '..'
						names.pop
						next
					end
				end
			end
			names << name
		}
		return self.class.new(absolute ? absolute : '.', @separator) if names.empty?
		path = absolute ? absolute : ''
		path << names.join(@separator)
		self.class.new(path, @separator)
	end
	private :cleanpath_aggressive

	def cleanpath_conservative
		return self.class.new('', @separator) if @pathname == ''
		names    = @segments.dup
		absolute = absolute?
		last_dot = names.last == '.'
		names.delete('.')
		names.shift while names.first == '..' if absolute
		return self.class.new(absolute ? absolute : '.', @separator) if names.empty?
		path = absolute ? absolute : ''
		path << names.join(@separator)
		if names.last != '..'
			if last_dot
				path << @separator+'.'
			elsif %r{#{@separator}\z} =~ @pathname
				path << @separator
			end
		end
		self.class.new(path, @separator)
	end
	private :cleanpath_conservative

	# helper for realpath, get's top + segments (top beeing "" for non absolutes and "/" on *nix,
	# something like "C:\" on win or whatever else absolute? returns. segments beeing a list
	# of segments besides top
	def top_segments #:nodoc:
		top = absolute? || ""
		if top then
			path = @pathname
		else
			path = self.class.current+@pathname
			top  = path.absolute? || ""
			path = path.to_str
		end
		segments = path[top.length..-1].scan(/[^#{Regexp.escape(@separator)}]+/)
		return top, segments
	end

	# Returns a real (absolute) path of +self+ in the actual filesystem.
	# The real path doesn't contain symlinks or useless dots.
	# Set resolve_nonexisting to true if you don't want it to raise an error
	# if a non existing path is resolved.
	def real(resolve_nonexisting=false)
		top, unresolved = top_segments
		resolved   = []
		inexistent = []
		if resolve_nonexisting
			while !File.exist?(top + unresolved.join(@separator)) && !unresolved.empty?
				inexistent.unshift unresolved.pop
			end
		end

		until unresolved.empty?
			case unresolved.last
				when '.'
					unresolved.pop
				when '..'
					resolved.unshift unresolved.pop
				else
					loop_check = {}
					while (stat = File.lstat(path = top + unresolved.join(@separator))).symlink?
						symlink_id = "#{stat.dev}:#{stat.ino}" #∆ won't work on windows (stat.ino always 0), OTOH, windows doesn't seem to have symlinks
						raise Errno::ELOOP.new(path) if loop_check[symlink_id]
						loop_check[symlink_id] = true
						top, unresolved        = top_segments
					end
					next if (filename = unresolved.pop) == '.'
					if filename != '..' && resolved.first == '..'
						resolved.shift
					else
						resolved.unshift filename
					end
			end #case
		end

		resolved.shift while resolved[0] == '..'
		resolved.push(*inexistent)

		if resolved.empty? then
			self.class.new(top.empty? ? '.' : @separator, @separator)
		else
			self.class.new(top + resolved.join(@separator), @separator)
		end
	end

	# creates a directory and all intermediary directories
	def create
		FileUtils.mkpath(@pathname)
	end

	# creates a file in path, creates intermediary directories if necessary
	# warning, if the file already exists it will be deleted
	def create_file(delete_existing=false)
		directory.create
		delete if exists? and delete_existing
		FileUtils.touch(@pathname) unless exists?
	end

	# removes file or directory (and all it's contents)
	def delete
		if File.directory?(@pathname)
			FileUtils.rm_r(@pathname)
		else
			File.unlink(@pathname)
		end
	end

	# yield each line of a file, if no block is given
	# returns an Iterator over the lines.
	def lines(sep_string=$/, &block)
		if block then
			File.open(@pathname, "rb") { |fh| fh.each_line(sep_string, &block) }
		else
			Iterator.new { |iter|
				File.open(@pathname, "rb") { |fh|
					fh.each_line(sep_string) { |line| iter.yield(line) }
				}
			}
		end
	end

	# yields chunks of size bytes, if no block is given returns
	# an Iterator over those chunks.
	def chunks(size=4096, &block)
		if block then
			File.open(@pathname, "rb") { |fh|
				while line = fh.read(size)
					yield(line)
				end
			}
		else
			Iterator.new { |iter|
				File.open(@pathname, "rb") { |fh|
					while line = fh.read(size)
						iter.yield(line)
					end
				}
			}
		end
	end

	# See +IO.read+
	def read(*args, &block); File.read(@pathname, *args, &block); end

	# See +IO.open+
	def open(*args, &block); File.open(@pathname, *args, &block); end

	# Write text to file and close it
	def write(text); File.open(@pathname, "wb") { |fh| fh.write(text) }; end

	# Append text to file and close it
	def append(text); File.open(@pathname, "ab") { |fh| fh.write(text) }; end

	# Truncates the file _file_name_ to be at most _integer_ bytes long.
	# Not available on all platforms.
	def truncate(integer); File.truncate(@pathname, integer); end

	# See +IO.sysopen+
	def sysopen(*args, &block); File.sysopen(@pathname, *args, &block); end

	# all entries in a directory, except . and ..
	# if no block is given it will return an Iterator over the entries
	def entries(pattern=nil)
		pattern ||= TruePattern
		if block_given? then
			Dir.entries(@pathname).each { |entry|
				next if entry == "." or entry == ".."
				path = self+entry
				yield(path) if pattern =~ entry
			}
		else
			Iterator.new { |iter|
				Dir.entries(@pathname).each { |entry|
					next if entry == "." or entry == ".."
					path = self+entry
					iter.yield(path) if pattern =~ entry
				}
			}
		end
	end

	# if a block is given it will yield all files
	# matching the optional pattern, else it will return an Iterator (Enumerable)
	# over those.
	def files(pattern=nil)
		pattern ||= TruePattern
		if block_given? then
			Dir.entries(@pathname).each { |entry|
				path = self+entry
				yield(path) if pattern =~ entry and path.file?
			}
		else
			Iterator.new { |iter|
				Dir.entries(@pathname).each { |entry|
					path = self+entry
					iter.yield(path) if pattern =~ entry and path.file?
				}
			}
		end
	end

	# if a block is given it will yield all directories (except . and ..)
	# matching the optional pattern, else it will return an Iterator (Enumerable)
	# over those.
	def directories(pattern=nil)
		pattern ||= TruePattern
		if block_given? then
			Dir.entries(@pathname).each { |entry|
				next if entry == "." or entry == ".."
				path = self+entry
				yield(path) if pattern =~ entry and path.directory?
			}
		else
			Iterator.new { |iter|
				Dir.entries(@pathname).each { |entry|
					next if entry == "." or entry == ".."
					path = self+entry
					iter.yield(path) if pattern =~ entry and path.directory?
				}
			}
		end
	end

	# Returns the last access time for the file as a Time object.
	# If parameter format is given, strftime is applied on the Time
	def accessed(format=nil)
		format ? File.atime(@pathname).strftime(format) : File.atime(@pathname)
	end

	# Returns the change time for the file (the time at which directory
	# information about the file was changed, not the file itself).
	# If parameter format is given, strftime is applied on the Time
	def changed(format=nil)
		format ? File.ctime(@pathname).strftime(format) : File.ctime(@pathname)
	end

	# Returns the modification time for the named file as a Time object.
	# If parameter format is given, strftime is applied on the Time
	def modified(format=nil)
		format ? File.mtime(@pathname).strftime(format) : File.mtime(@pathname)
	end

	# See <tt>File.utime</tt>.  Update the access and modification times.
	def utime(atime, mtime) File.utime(atime, mtime, @pathname) end
	# Returns a +File::Stat+ object for the named file (see +File::Stat+).
	def stat; File.stat(@pathname); end
	# Same as +Path::stat+, but does not follow the last symbolic link.
	# Instead, reports on the link itself.
	def lstat; File.lstat(@pathname); end
	# Identifies the type of the named file; the return string is one of
	# "+file+", "+directory+", "+characterSpecial+", "+blockSpecial+",
	# "+fifo+", "+link+", "+socket+", or "+unknown+".
	def type; File.ftype(@pathname); end
	# See <tt>File.chmod</tt>.  Changes permissions.
	def chmod(mode) File.chmod(mode, @pathname) end
	# See <tt>File.lchmod</tt>.
	def lchmod(mode) File.lchmod(mode, @pathname) end
	# See <tt>File.chown</tt>.  Change owner and group of file.
	def chown(owner, group) File.chown(owner, group, @pathname) end
	# See <tt>File.lchown</tt>.
	def lchown(owner, group) File.lchown(owner, group, @pathname) end
	# See <tt>File.fnmatch?</tt>. Return +true+ if the receiver matches the given
	# pattern.
	def fnmatch?(pattern, *args) File.fnmatch?(pattern, @pathname, *args) end
	# See <tt>File.link</tt>.  Creates a hard link.
	def link(from)        File.link(@pathname, from) end
	# See <tt>File.readlink</tt>.  Read symbolic link.
	def readlink()        self.class.new(File.readlink(@pathname), @separator) end
	# See <tt>File.symlink</tt>.  Creates a symbolic link in from
	def symlink(from)     File.symlink(@pathname, from) end
	# See <tt>File.blockdev?</tt>.
	def blockdev?;        File.blockdev?(@pathname);        end
	# See <tt>File.chardev?</tt>.
	def chardev?;         File.chardev?(@pathname);         end
	# See <tt>File.executable?</tt>.
	def executable?;      File.executable?(@pathname);      end
	# See <tt>File.executable_real?</tt>.
	def executable_real?; File.executable_real?(@pathname); end
	# See <tt>File.exist?</tt>.
	def exist?;           File.exist?(@pathname);           end
	# See <tt>File.exist?</tt>.
	def exists?;          File.exist?(@pathname);           end
	# See <tt>File.grpowned?</tt>.
	def grpowned?;        File.grpowned?(@pathname);        end
	# See <tt>File.directory?</tt>.
	def directory?;       File.directory?(@pathname);       end
	# See <tt>File.file?</tt>.
	def file?;            File.file?(@pathname);            end
	# See <tt>File.pipe?</tt>.
	def pipe?;            File.pipe?(@pathname);            end
	# See <tt>File.socket?</tt>.
	def socket?;          File.socket?(@pathname);          end
	# See <tt>File.readable?</tt>.
	def readable?;        File.readable?(@pathname);        end
	# See <tt>File.readable_real?</tt>.
	def readable_real?;   File.readable_real?(@pathname);   end
	# See <tt>File.setuid?</tt>.
	def setuid?;          File.setuid?(@pathname);          end
	# See <tt>File.setgid?</tt>.
	def setgid?;          File.setgid?(@pathname);          end
	# See <tt>File.size</tt>.
	def size;             File.size(@pathname);             end
	# See <tt>File.size?</tt>.
	def size?;            File.size?(@pathname);            end
	# See <tt>File.sticky?</tt>.
	def sticky?;          File.sticky?(@pathname);          end
	# See <tt>File.symlink?</tt>.
	def symlink?;         File.symlink?(@pathname);         end
	# See <tt>File.writable?</tt>.
	def writable?;        File.writable?(@pathname);        end
	# See <tt>File.writable_real?</tt>.
	def writable_real?;   File.writable_real?(@pathname);   end


	def to_str
		@pathname.dup
	end

	def inspect # :nodoc:
		"<Path #{@pathname}>"
	end
	alias to_s inspect

	def to_path
		dup
	end

	def dup
		self.class.new(@pathname, @separator)
	end

	def hash # :nodoc:
		@pathname.hash
	end

	# compares on string basis, can be compared to a String
	def <=>(other)
		other.to_str.gsub(@separator, 0.chr) <=> @pathname.gsub(@separator, 0.chr)
	end

	# compares on string basis, can be compared to a String
	def ==(other)
		other.to_str == @pathname
	end

	def eql?(other) # :nodoc:
		other.to_str.eql?(@pathname)
	end

	def taint # :nodoc:
		super
		@pathname.taint
		@segments.taint
		@segments.map { |e| e.taint }
		self
	end

	def untaint # :nodoc:
		super
		@pathname.untaint
		@segments.untaint
		@segments.map { |e| e.untaint }
	end
end