# encoding: utf-8
module Mail
  # Provides a single class to call to create a new structured or unstructured
  # field.  Works out per RFC what field of field it is being given and returns
  # the correct field of class back on new.
  # 
  # ===Per RFC 2822
  #  
  #  2.2. Header Fields
  #  
  #     Header fields are lines composed of a field name, followed by a colon
  #     (":"), followed by a field body, and terminated by CRLF.  A field
  #     name MUST be composed of printable US-ASCII characters (i.e.,
  #     characters that have values between 33 and 126, inclusive), except
  #     colon.  A field body may be composed of any US-ASCII characters,
  #     except for CR and LF.  However, a field body may contain CRLF when
  #     used in header "folding" and  "unfolding" as described in section
  #     2.2.3.  All field bodies MUST conform to the syntax described in
  #     sections 3 and 4 of this standard.
  #  
  class Field
    
    include Patterns
    include Comparable
    
    STRUCTURED_FIELDS = %w[ bcc cc content-description content-disposition
                            content-id content-transfer-encoding content-type 
                            date from in-reply-to keywords message-id
                            mime-version received references reply-to
                            resent-bcc resent-cc resent-date resent-from
                            resent-message-id resent-sender resent-to
                            return-path sender to ]

    KNOWN_FIELDS = STRUCTURED_FIELDS + ['comments', 'subject']
    
    # Generic Field Exception
    class FieldError < StandardError
    end

    # Raised when a parsing error has occurred (ie, a StructuredField has tried
    # to parse a field that is invalid or improperly written)
    class ParseError < FieldError #:nodoc:
    end

    # Raised when attempting to set a structured field's contents to an invalid syntax
    class SyntaxError < FieldError #:nodoc:
    end
    
    # Accepts a text string in the format of:
    # 
    #  "field-name: field data"
    # 
    # Note, does not want a terminating carriage return.  Returns
    # self appropriately parsed
    def initialize(raw_field_text)
      if raw_field_text !~ /:/
        name = raw_field_text
        create_field(name, nil)
      else
        name, value = split(raw_field_text)
        create_field(name, value)
      end
      return self
    end

    def field=(value)
      @field = value
    end
    
    def field
      @field
    end
    
    def name
      field.name
    end
    
    def value
      field.value
    end
    
    def value=(str)
      create_field(name, str)
    end
    
    def to_s
      field.to_s
    end
    
    def update(name, value)
      create_field(name, value)
    end
    
    def same( other )
      match_to_s(other.name, field.name)
    end
    
    def <=>( other )
      self_order = FIELD_ORDER.rindex(self.name.downcase) || 100
      other_order = FIELD_ORDER.rindex(other.name.downcase) || 100
      self_order <=> other_order
    end
    
    def method_missing(name, *args, &block)
      field.send(name, *args, &block)
    end
    
    FIELD_ORDER = %w[ return-path received
                      resent-date resent-from resent-sender resent-to
                      resent-cc resent-bcc resent-message-id
                      date from sender reply-to to cc bcc
                      message-id in-reply-to references
                      subject comments keywords
                      mime-version content-type content-transfer-encoding
                      content-disposition content-description ]
    
    private
    
    def split(raw_field)
      match_data = raw_field.match(/^(#{FIELD_NAME})\s*:\s*(#{FIELD_BODY})$/)
      [match_data[1].to_s.strip, match_data[2].to_s.strip]
    rescue
      STDERR.puts "WARNING: Could not parse (and so ignorning) '#{raw_field}'"
    end

    def create_field(name, value)
      begin
        self.field = new_field(name, value)
      rescue
        self.field = Mail::UnstructuredField.new(name, value)
      end
    end

    def new_field(name, value)
      # Could do this with constantize and make it as DRY as, but a simple case is,
      # well, simpler... 
      case name.downcase
      when /^to$/
        ToField.new(name,value)
      when /^cc$/
        CcField.new(name,value)
      when /^bcc$/
        BccField.new(name, value)
      when /^message-id$/
        MessageIdField.new(name, value)
      when /^in-reply-to$/
        InReplyToField.new(name, value)
      when /^references$/
        ReferencesField.new(name, value)
      when /^subject$/
        SubjectField.new(name, value)
      when /^comments$/
        CommentsField.new(name, value)
      when /^keywords$/
        KeywordsField.new(name, value)
      when /^date$/
        DateField.new(name, value)
      when /^from$/
        FromField.new(name, value)
      when /^sender$/
        SenderField.new(name, value)
      when /^reply-to$/
        ReplyToField.new(name, value)
      when /^resent-date$/
        ResentDateField.new(name, value)
      when /^resent-from$/
        ResentFromField.new(name, value)
      when /^resent-sender$/ 
        ResentSenderField.new(name, value)
      when /^resent-to$/
        ResentToField.new(name, value)
      when /^resent-cc$/
        ResentCcField.new(name, value)
      when /^resent-bcc$/
        ResentBccField.new(name, value)
      when /^resent-message-id$/
        ResentMessageIdField.new(name, value)
      when /^return-path$/
        ReturnPathField.new(name, value)
      when /^received$/
        ReceivedField.new(name, value)
      when /^mime-version$/
        MimeVersionField.new(name, value)
      when /^content-transfer-encoding$/
        ContentTransferEncodingField.new(name, value)
      when /^content-description$/
        ContentDescriptionField.new(name, value)
      when /^content-disposition$/
        ContentDispositionField.new(name, value)
      when /^content-type$/
        ContentTypeField.new(name, value)
      when /^content-id$/
        ContentIdField.new(name, value)
      else 
        OptionalField.new(name, value)
      end
      
    end

  end
  
end