require "fileutils"

module Berkshelf
  module FileSyncer
    extend self

    # Files to be ignored during a directory globbing
    IGNORED_FILES = %w{. ..}.freeze

    #
    # Glob across the given pattern, accounting for dotfiles, removing Ruby's
    # dumb idea to include +'.'+ and +'..'+ as entries.
    #
    # @param [String] pattern
    #   the path or glob pattern to get all files from
    #
    # @return [Array<String>]
    #   the list of all files
    #
    # @note
    #   Globbing on windows is strange. Do not pass a path that contains
    #   "symlinked" directories. Dir.glob will not see them. As an example,
    #   'C:\Documents and Settings' is not a real directory and int recent
    #   versions of windows points at 'C:\users'. Some users have their
    #   temp directory still referring to 'C:\Documents and Settings'.
    #
    def glob(pattern)
      Dir.glob(pattern, File::FNM_DOTMATCH).sort.reject do |file|
        basename = File.basename(file)
        IGNORED_FILES.include?(basename)
      end
    end

    #
    # Copy the files from +source+ to +destination+, while removing any files
    # in +destination+ that are not present in +source+.
    #
    # The method accepts an optional +:exclude+ parameter to ignore files and
    # folders that match the given pattern(s). Note the exclude pattern behaves
    # on paths relative to the given source. If you want to exclude a nested
    # directory, you will need to use something like +**/directory+.
    #
    # @raise ArgumentError
    #   if the +source+ parameter is not a directory
    #
    # @param [String] source
    #   the path on disk to sync from
    # @param [String] destination
    #   the path on disk to sync to
    #
    # @option options [String, Array<String>] :exclude
    #   a file, folder, or globbing pattern of files to ignore when syncing
    #
    # @return [true]
    #
    def sync(source, destination, options = {})
      unless File.directory?(source)
        raise ArgumentError, "`source' must be a directory, but was a " \
          "`#{File.ftype(source)}'! If you just want to sync a file, use " \
          "the `copy' method instead."
      end

      # Reject any files that match the excludes pattern
      excludes = Array(options[:exclude]).map do |exclude|
        [exclude, "#{exclude}/*"]
      end.flatten

      source_files = Dir.chdir(source) do
        glob("**/*").reject do |source_file|
          excludes.any? { |exclude| File.fnmatch?(exclude, source_file, File::FNM_DOTMATCH) }
        end
      end

      # Ensure the destination directory exists
      FileUtils.mkdir_p(destination) unless File.directory?(destination)

      # Copy over the filtered source files
      source_files.each do |relative_path|
        source_file = File.join(source, relative_path)
        # Create the parent directory
        parent = File.join(destination, File.dirname(relative_path))
        FileUtils.mkdir_p(parent) unless File.directory?(parent)

        case File.ftype(source_file).to_sym
        when :directory
          FileUtils.mkdir_p("#{destination}/#{relative_path}")
        when :link
          target = File.readlink(source_file)

          destination = File.expand_path(destination)
          Dir.chdir(destination) do
            FileUtils.ln_sf(target, "#{destination}/#{relative_path}")
          end
        when :file
          FileUtils.cp(source_file, "#{destination}/#{relative_path}")
        else
          type = File.ftype(source_file)
          raise "Unknown file type: `#{type}' at " \
            "`#{source_file}'. Failed to sync `#{source_file}' to " \
            "`#{destination}/#{relative_path}'!"
        end
      end

      if options[:delete]
        # Remove any files in the destination that are not in the source files
        destination_files = Dir.chdir(destination) do
          glob("**/*")
        end

        # Remove any extra files that are present in the destination, but are
        # not in the source list
        extra_files = destination_files - source_files
        extra_files.each do |file|
          FileUtils.rm_rf(File.join(destination, file))
        end
      end

      true
    end
  end
end