#
# Author:: Bryan McLellan <btm@loftninjas.org>
# Copyright:: Copyright (c) 2014 Chef Software, Inc.
# License:: Apache License, Version 2.0
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
#

require 'chef-config/windows'
require 'chef-config/logger'
require 'chef-config/exceptions'

module ChefConfig
  class PathHelper
    # Maximum characters in a standard Windows path (260 including drive letter and NUL)
    WIN_MAX_PATH = 259

    def self.dirname(path)
      if ChefConfig.windows?
        # Find the first slash, not counting trailing slashes
        end_slash = path.size
        loop do
          slash = path.rindex(/[#{Regexp.escape(File::SEPARATOR)}#{Regexp.escape(path_separator)}]/, end_slash - 1)
          if !slash
            return end_slash == path.size ? '.' : path_separator
          elsif slash == end_slash - 1
            end_slash = slash
          else
            return path[0..slash-1]
          end
        end
      else
        ::File.dirname(path)
      end
    end

    BACKSLASH = '\\'.freeze

    def self.path_separator
      if ChefConfig.windows?
        File::ALT_SEPARATOR || BACKSLASH
      else
        File::SEPARATOR
      end
    end

    def self.join(*args)
      path_separator_regex = Regexp.escape(File::SEPARATOR)
      unless path_separator == File::SEPARATOR
        path_separator_regex << Regexp.escape(path_separator)
      end

      trailing_slashes = /[#{path_separator_regex}]+$/
      leading_slashes = /^[#{path_separator_regex}]+/

      args.flatten.inject() do |joined_path, component|
        joined_path = joined_path.sub(trailing_slashes, '')
        component = component.sub(leading_slashes, '')
        joined_path += "#{path_separator}#{component}"
      end
    end

    def self.validate_path(path)
      if ChefConfig.windows?
        unless printable?(path)
          msg = "Path '#{path}' contains non-printable characters. Check that backslashes are escaped with another backslash (e.g. C:\\\\Windows) in double-quoted strings."
          ChefConfig.logger.error(msg)
          raise ChefConfig::InvalidPath, msg
        end

        if windows_max_length_exceeded?(path)
          ChefConfig.logger.debug("Path '#{path}' is longer than #{WIN_MAX_PATH}, prefixing with'\\\\?\\'")
          path.insert(0, "\\\\?\\")
        end
      end

      path
    end

    def self.windows_max_length_exceeded?(path)
      # Check to see if paths without the \\?\ prefix are over the maximum allowed length for the Windows API
      # http://msdn.microsoft.com/en-us/library/windows/desktop/aa365247%28v=vs.85%29.aspx
      unless path =~ /^\\\\?\\/
        if path.length > WIN_MAX_PATH
          return true
        end
      end

      false
    end

    def self.printable?(string)
      # returns true if string is free of non-printable characters (escape sequences)
      # this returns false for whitespace escape sequences as well, e.g. \n\t
      if string =~ /[^[:print:]]/
        false
      else
        true
      end
    end

    # Produces a comparable path.
    def self.canonical_path(path, add_prefix=true)
      # First remove extra separators and resolve any relative paths
      abs_path = File.absolute_path(path)

      if ChefConfig.windows?
        # Add the \\?\ API prefix on Windows unless add_prefix is false
        # Downcase on Windows where paths are still case-insensitive
        abs_path.gsub!(::File::SEPARATOR, path_separator)
        if add_prefix && abs_path !~ /^\\\\?\\/
          abs_path.insert(0, "\\\\?\\")
        end

        abs_path.downcase!
      end

      abs_path
    end

    def self.cleanpath(path)
      path = Pathname.new(path).cleanpath.to_s
      # ensure all forward slashes are backslashes
      if ChefConfig.windows?
        path = path.gsub(File::SEPARATOR, path_separator)
      end
      path
    end

    def self.paths_eql?(path1, path2)
      canonical_path(path1) == canonical_path(path2)
    end

    # Paths which may contain glob-reserved characters need
    # to be escaped before globbing can be done.
    # http://stackoverflow.com/questions/14127343
    def self.escape_glob(*parts)
      path = cleanpath(join(*parts))
      path.gsub(/[\\\{\}\[\]\*\?]/) { |x| "\\"+x }
    end

    def self.relative_path_from(from, to)
      Pathname.new(cleanpath(to)).relative_path_from(Pathname.new(cleanpath(from)))
    end

    # Retrieves the "home directory" of the current user while trying to ascertain the existence
    # of said directory.  The path returned uses / for all separators (the ruby standard format).
    # If the home directory doesn't exist or an error is otherwise encountered, nil is returned.
    #
    # If a set of path elements is provided, they are appended as-is to the home path if the
    # homepath exists.
    #
    # If an optional block is provided, the joined path is passed to that block if the home path is
    # valid and the result of the block is returned instead.
    #
    # Home-path discovery is performed once.  If a path is discovered, that value is memoized so
    # that subsequent calls to home_dir don't bounce around.
    #
    # See self.all_homes.
    def self.home(*args)
      @@home_dir ||= self.all_homes { |p| break p }
      if @@home_dir
        path = File.join(@@home_dir, *args)
        block_given? ? (yield path) : path
      end
    end

    # See self.home.  This method performs a similar operation except that it yields all the different
    # possible values of 'HOME' that one could have on this platform.  Hence, on windows, if
    # HOMEDRIVE\HOMEPATH and USERPROFILE are different, the provided block will be called twice.
    # This method goes out and checks the existence of each location at the time of the call.
    #
    # The return is a list of all the returned values from each block invocation or a list of paths
    # if no block is provided.
    def self.all_homes(*args)
      paths = []
      if ChefConfig.windows?
        # By default, Ruby uses the the following environment variables to determine Dir.home:
        # HOME
        # HOMEDRIVE HOMEPATH
        # USERPROFILE
        # Ruby only checks to see if the variable is specified - not if the directory actually exists.
        # On Windows, HOMEDRIVE HOMEPATH can point to a different location (such as an unavailable network mounted drive)
        # while USERPROFILE points to the location where the user application settings and profile are stored.  HOME
        # is not defined as an environment variable (usually).  If the home path actually uses UNC, then the prefix is
        # HOMESHARE instead of HOMEDRIVE.
        #
        # We instead walk down the following and only include paths that actually exist.
        # HOME
        # HOMEDRIVE HOMEPATH
        # HOMESHARE HOMEPATH
        # USERPROFILE

        paths << ENV['HOME']
        paths << ENV['HOMEDRIVE'] + ENV['HOMEPATH'] if ENV['HOMEDRIVE'] && ENV['HOMEPATH']
        paths << ENV['HOMESHARE'] + ENV['HOMEPATH'] if ENV['HOMESHARE'] && ENV['HOMEPATH']
        paths << ENV['USERPROFILE']
      end
      paths << Dir.home if ENV['HOME']

      # Depending on what environment variables we're using, the slashes can go in any which way.
      # Just change them all to / to keep things consistent.
      # Note: Maybe this is a bad idea on some unixy systems where \ might be a valid character depending on
      # the particular brand of kool-aid you consume.  This code assumes that \ and / are both
      # path separators on any system being used.
      paths = paths.map { |home_path| home_path.gsub(path_separator, ::File::SEPARATOR) if home_path }

      # Filter out duplicate paths and paths that don't exist.
      valid_paths = paths.select { |home_path| home_path && Dir.exists?(home_path) }
      valid_paths = valid_paths.uniq

      # Join all optional path elements at the end.
      # If a block is provided, invoke it - otherwise just return what we've got.
      joined_paths = valid_paths.map { |home_path| File.join(home_path, *args) }
      if block_given?
        joined_paths.each { |p| yield p }
      else
        joined_paths
      end
    end
  end
end