require 'marc4j4r'
require 'set'
require 'pp'
module MARCSpec

  # A ControlFieldSpec takes a control tag (generally 001..009) and an optional zero-based range
  # When called with marc_values(record), it returns either the complete value of all
  # occurances of the field in question (in the order they appear in the record), or 
  # the zero-based substrings based on the passed range. 
  #
  # @example Get the whole 001
  # cfs = MARCSpec::ControlTagSpec.new('001')
  # 
  # @example Get the first three characters of the 008
  # cfs = MARCSpec::ControlTagSpec.new('001', 0..2)
  #
  # Note that the use of the zero-based range in this manner conforms to the way MARC 
  # substrings are specified.
  
  class ControlFieldSpec
    attr_accessor :tag, :range
    
    def initialize (tag, range=nil)
      unless MARC4J4R::ControlField.control_tag? tag
        raise ArgumentError "Tag must be a control tag"
      end
      @tag = tag
      self.range = range
    end
    
    def == other
      return ((self.tag == other.tag) and
              (self.range = other.range))
    end
    
    
    # Always force a real range, since in Ruby 1.9 a string subscript with a single fixnum
    # will return the character code of that character (e.g., "Bill"[0] => 66, wherease 
    # "Bill"[0..0] gives the expected 'B'
    #
    # @param [nil, Fixnum, Range] range A zero-based substring range or character position
    # @return [MARCSpec::ControlFieldSpec] self
    
    def range= range
      if range.nil?
        @range = nil
        return self
      end
      if range.is_a? Fixnum
        if range < 0
          raise ArgumentError, "Range must be nil, an integer offset (1-based), or a Range, not #{range}"
        end
      
        @range = range..range
      
      elsif range.is_a? Range
        @range = range
      else
        raise ArgumentError, "Range must be nil, an integer offset (1-based), or a Range, not #{range.inspect}"
      end
      return self
    end
    
    
    def marc_values r
      vals = r.find_by_tag(@tag).map {|f| f.value}
      if @range
        return vals.map {|v| v[@range]}
      else
        return vals
      end
    end
    
    def pretty_print pp
      pp.pp eval(self.asPPString)
    end
    
    def asPPString
      s = StringIO.new
      if @range
        PP.pp([@tag, @range], s)
      else
        PP.pp([@tag], s)
      end
      return s.string
    end
    
    def self.fromPPString str
      a = eval(str)
      return self.new(*a)
    end
    
  end
  
  
  # A LeaderSpec deals only with the leader. It's basically the same as a controlfield spec, but
  # using the string 'LDR' to identify itself
  
  class LeaderSpec < ControlFieldSpec
    
    # Built to be syntax-compatible with ControlFieldSpec, the tag must always
    # be 'LDR' (case matters)
    #
    # @param ['LDR'] tag The 'tag'; in this case, always 'LDR'
    # @param [Fixnum, Range<Fixnum>] range substring specification (either one character or a range) to return
    # instead of the whole leader.
    
    def initialize (tag, range=nil)
      unless tag == 'LDR'
        raise ArgumentError "Tag must be 'LDR'"
      end
      @tag = 'LDR'
      self.range = range
    end
    
    # Return the appropriate value (either the leader or a subset of it) from the
    # given record
    #
    # @param [MARC4J4R::Record] r A MARC4J4R Record
    # @return [String] the leader or substring of the leader
    def marc_values r
      if @range
        return r.leader[@range]
      else
        return r.leader
      end
    end
  end    
    
  
  # A VariableFieldSpec has a tag (three chars) and a set of codes. Its #marc_values(r) method will return
  # all the values for the subfields for the given codes joined by the optional joiner (space by default)
  #
  # The subfield values are presented in the order they appear in the document, *not* the order the subfield
  # codes are specified
  #
  # @example Get the $a from the 245s
  # vfs = MARCSpec::VariableFieldSpec.new('245', 'a')
  #
  # vfs = MARCSpec::VariableFieldSpec.new('245', 'ab')
  
  
  class VariableFieldSpec
    
    attr_accessor :tag, :codes, :joiner
    
    def initialize tag, codes=nil, joiner=' '
      @tag = tag
      @joiner = joiner || ' '
      self.codes = codes
    end
    
    def == other
      return ((self.tag == other.tag) and
              (self.codes = other.codes) and
              (self.joiner = other.joiner))
    end
    
    def codes= c
      if c.nil?
        @codes = nil
        return nil
      end
      
      if( c.is_a? Array) or (c.is_a? Set) or (c.is_a? Range)
        @codes = c.to_a
      else
        @codes = c.split(//)
      end

      return @codes
    end
    
    def marc_values r
      fields = r.find_by_tag(@tag)
      vals = []
      fields.each do |f|
        subvals = f.sub_values(@codes)
        vals << subvals.join(@joiner) if subvals.size > 0
      end
      return vals
    end

    def pretty_print pp
      pp.pp eval(self.asPPString)
    end
    
    def asPPString
      s = StringIO.new
      if @joiner and @joiner != ' '
        PP.pp([@tag, '*', '*', @codes.join(''), @joiner], s)
      else
        PP.pp([@tag, '*', '*', @codes.join('')], s)
      end
      return s.string
    end

   def self.fromPPString str
     a = eval(str)
     return self.new(a[0], a[3], a[4])
   end

  end
  
end