#
# Author:: John Keiser (<jkeiser@opscode.com>)
# Copyright:: Copyright (c) 2012 Opscode, 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_fs'
require 'pathname'

module ChefFS
  class PathUtils

    # If you are in 'source', this is what you would have to type to reach 'dest'
    # relative_to('/a/b/c/d/e', '/a/b/x/y') == '../../c/d/e'
    # relative_to('/a/b', '/a/b') == '.'
    def self.relative_to(dest, source)
      # Skip past the common parts
      source_parts = ChefFS::PathUtils.split(source)
      dest_parts = ChefFS::PathUtils.split(dest)
      i = 0
      until i >= source_parts.length || i >= dest_parts.length || source_parts[i] != dest_parts[i]
        i+=1
      end
      # dot-dot up from 'source' to the common ancestor, then
      # descend to 'dest' from the common ancestor
      result = ChefFS::PathUtils.join(*(['..']*(source_parts.length-i) + dest_parts[i,dest.length-i]))
      result == '' ? '.' : result
    end

    def self.join(*parts)
      return "" if parts.length == 0
      # Determine if it started with a slash
      absolute = parts[0].length == 0 || parts[0].length > 0 && parts[0] =~ /^#{regexp_path_separator}/
      # Remove leading and trailing slashes from each part so that the join will work (and the slash at the end will go away)
      parts = parts.map { |part| part.gsub(/^\/|\/$/, "") }
      # Don't join empty bits
      result = parts.select { |part| part != "" }.join("/")
      # Put the / back on
      absolute ? "/#{result}" : result
    end

    def self.split(path)
      path.split(Regexp.new(regexp_path_separator))
    end

    def self.regexp_path_separator
      ChefFS::windows? ? '[\/\\\\]' : '/'
    end

    # Given a path which may only be partly real (i.e. /x/y/z when only /x exists,
    # or /x/y/*/blah when /x/y/z/blah exists), call File.realpath on the biggest
    # part that actually exists.
    #
    # If /x is a symlink to /blarghle, and has no subdirectories, then:
    # PathUtils.realest_path('/x/y/z') == '/blarghle/y/z'
    # PathUtils.realest_path('/x/*/z') == '/blarghle/*/z'
    # PathUtils.realest_path('/*/y/z') == '/*/y/z'
    def self.realest_path(path)
      path = Pathname.new(path)
      begin
        path.realpath.to_s
      rescue Errno::ENOENT
        dirname = path.dirname
        if dirname
          PathUtils.join(realest_path(dirname), path.basename.to_s)
        else
          path.to_s
        end
      end
    end

    def self.is_absolute?(path)
      path =~ /^#{regexp_path_separator}/
    end
  end
end
