# A library of text transforms.  Each public module method returns a callable
# object which can be used to transform an array of lines.
module Germinate::TextTransforms

  IDENTITY_TRANSFORM = lambda {|hunk| hunk}
  def self.join_lines
    lambda { |hunk|
      paragraphs = hunk.inject([[]]) { |result, line|
        case line
        when /\S/
          result.last << line.strip
        when String
          result << [line]
          result << []
        else
          result << line
        end
        result
      }
      paragraphs.delete_if{|p| p.empty?}
      hunk.dup.replace(paragraphs.map {|paragraph|
        case paragraph
        when Germinate::Hunk then paragraph
        else paragraph.join(" ") 
        end
      })
    }
  end

  def self.strip_blanks
    lambda { |hunk|
      result = hunk.dup
      result.shift while result.first =~ /^\s*$/ && !result.empty?
      result.pop while result.last =~ /^\s*$/ && !result.empty?
      result
    }
  end

  def self.erase_comments(comment_prefix="")
    lambda { |hunk|
      hunk.dup.map! do |line|
        if comment_prefix && String === line
          if match_data = /^\s*(#{comment_prefix})+\s*/.match(line)
            offset = match_data.begin(0)
            length = match_data[0].length
            line_copy = line.dup
            line_copy[offset, length] = (" " * length)
            line_copy
          else
            line
          end
        else
          line
        end
      end
    }
  end

  def self.uncomment(comment_prefix=nil)
    lambda { |hunk|
      comment_prefix ||= hunk.comment_prefix
      hunk.dup.map! do |line|
        if comment_prefix && line.respond_to?(:sub)
          line.sub(/^#{Regexp.escape(comment_prefix.rstrip)}\s*/,"")
        else
          line
        end
      end
    }
  end

  def self.rstrip_lines
    lambda { |hunk|
      hunk.dup.map!{|line| String === line ? line.to_s.rstrip : line}
    }
  end

  def self.bracket(open_bracket=nil, close_bracket=nil)
    lambda { |hunk|
      result = hunk.dup
      result.clear
      result << (open_bracket || hunk.code_open_bracket)
      result.push(*Array(hunk))
      result << (close_bracket || hunk.code_close_bracket)
      result.compact!
      result
    }
  end

  def self.pipeline(pipeline=nil)
    lambda do |hunk|
      pipeline ||= hunk.pipeline
      pipeline.call(hunk)
    end
  end

  def self.expand_insertions
    lambda do |hunk|
      hunk.resolve_insertions
    end
  end

  def self.flatten_nested
    lambda do |hunk|
      result = hunk.flatten
      result.copy_shared_style_attributes_from(hunk)
      result
    end
  end

  eigenclss = class << self; self; end

  eigenclss.instance_eval do
    private
    def log
      @log ||= Germinate.logger
    end
  end
end