module SmarterCSV

  class HeaderSizeMismatch < Exception
  end

  def SmarterCSV.process(input, options={}, &block)   # first parameter: filename or input object with readline method
    default_options = {:col_sep => ',' , :row_sep => $/ , :quote_char => '"', :force_simple_split => false , :verbose => false ,
      :remove_empty_values => true, :remove_zero_values => false , :remove_values_matching => nil , :remove_empty_hashes => true , :strip_whitespace => true,
      :convert_values_to_numeric => true, :strip_chars_from_headers => nil , :user_provided_headers => nil , :headers_in_file => true,
      :comment_regexp => /^#/, :chunk_size => nil , :key_mapping_hash => nil , :downcase_header => true, :strings_as_keys => false, :file_encoding => 'utf-8'
    }
    options = default_options.merge(options)
    csv_options = options.select{|k,v| [:col_sep, :row_sep, :quote_char].include?(k)} # options.slice(:col_sep, :row_sep, :quote_char)
    headerA = []
    result = []
    old_row_sep = $/
    line_count = 0
    begin
      $/ = options[:row_sep]
      f = input.respond_to?(:readline) ? input : File.open(input, "r:#{options[:file_encoding]}")

      if options[:headers_in_file]        # extract the header line
        # process the header line in the CSV file..
        # the first line of a CSV file contains the header .. it might be commented out, so we need to read it anyhow
        header = f.readline.sub(options[:comment_regexp],'').chomp(options[:row_sep])
        line_count += 1
        header = header.gsub(options[:strip_chars_from_headers], '') if options[:strip_chars_from_headers]
        if (header =~ %r{#{options[:quote_char]}}) and (! options[:force_simple_split])
          file_headerA = CSV.parse( header, csv_options ).flatten.collect!{|x| x.nil? ? '' : x} # to deal with nil values from CSV.parse
        else
          file_headerA =  header.split(options[:col_sep])
        end
        file_headerA.map!{|x| x.gsub(%r/options[:quote_char]/,'') }
        file_headerA.map!{|x| x.strip}  if options[:strip_whitespace]
        file_headerA.map!{|x| x.gsub(/\s+/,'_')}
        file_headerA.map!{|x| x.downcase }   if options[:downcase_header]
        file_header_size = file_headerA.size
      end
      if options[:user_provided_headers] && options[:user_provided_headers].class == Array && ! options[:user_provided_headers].empty?
        # use user-provided headers
        headerA = options[:user_provided_headers]
        if defined?(file_header_size) && ! file_header_size.nil?
          if headerA.size != file_header_size
            raise SmarterCSV::HeaderSizeMismatch , "ERROR [smarter_csv]: :user_provided_headers defines #{headerA.size} headers !=  CSV-file #{input} has #{file_header_size} headers"
          else
            # we could print out the mapping of file_headerA to headerA here
          end
        end
      else
        headerA = file_headerA
      end
      headerA.map!{|x| x.to_sym } unless options[:strings_as_keys]

      unless options[:user_provided_headers] # wouldn't make sense to re-map user provided headers
        key_mappingH = options[:key_mapping]

        # do some key mapping on the keys in the file header
        #   if you want to completely delete a key, then map it to nil or to ''
        if ! key_mappingH.nil? && key_mappingH.class == Hash && key_mappingH.keys.size > 0
          headerA.map!{|x| key_mappingH.has_key?(x) ? (key_mappingH[x].nil? ? nil : key_mappingH[x].to_sym) : x}
        end
      end

      # in case we use chunking.. we'll need to set it up..
      if ! options[:chunk_size].nil? && options[:chunk_size].to_i > 0
        use_chunks = true
        chunk_size = options[:chunk_size].to_i
        chunk_count = 0
        chunk = []
      else
        use_chunks = false
      end

      # now on to processing all the rest of the lines in the CSV file:
      while ! f.eof?    # we can't use f.readlines() here, because this would read the whole file into memory at once, and eof => true
        line = f.readline  # read one line.. this uses the input_record_separator $/ which we set previously!
        line_count += 1
        print "processing line %10d\r" % line_count if options[:verbose]
        next  if  line =~ options[:comment_regexp]  # ignore all comment lines if there are any
        line.chomp!    # will use $/ which is set to options[:col_sep]

        if (line =~ %r{#{options[:quote_char]}}) and (! options[:force_simple_split])
          dataA = CSV.parse( line, csv_options ).flatten.collect!{|x| x.nil? ? '' : x} # to deal with nil values from CSV.parse
        else
          dataA =  line.split(options[:col_sep])
        end
        dataA.map!{|x| x.gsub(%r/options[:quote_char]/,'') }
        dataA.map!{|x| x.strip}  if options[:strip_whitespace]
        hash = Hash.zip(headerA,dataA)  # from Facets of Ruby library
        # make sure we delete any key/value pairs from the hash, which the user wanted to delete:
        # Note: Ruby < 1.9 doesn't allow empty symbol literals!
        hash.delete(nil); hash.delete('');
        if RUBY_VERSION.to_f > 1.8
          eval('hash.delete(:"")')
        end

        hash.delete_if{|k,v| v.nil? || v =~ /^\s*$/}  if options[:remove_empty_values]
        hash.delete_if{|k,v| ! v.nil? && v =~ /^(\d+|\d+\.\d+)$/ && v.to_f == 0} if options[:remove_zero_values]   # values are typically Strings!
        hash.delete_if{|k,v| v =~ options[:remove_values_matching]} if options[:remove_values_matching]
        if options[:convert_values_to_numeric]
          hash.each do |k,v|
            case v
            when /^[+-]?\d+\.\d+$/
              hash[k] = v.to_f
            when /^[+-]?\d+$/
              hash[k] = v.to_i
            end
          end
        end
        next if hash.empty? if options[:remove_empty_hashes]

        if use_chunks
          chunk << hash  # append temp result to chunk

          if chunk.size >= chunk_size || f.eof?   # if chunk if full, or EOF reached
            # do something with the chunk
            if block_given?
              yield chunk  # do something with the hashes in the chunk in the block
            else
              result << chunk  # not sure yet, why anybody would want to do this without a block
            end
            chunk_count += 1
            chunk = []  # initialize for next chunk of data
          end
          # while a chunk is being filled up we don't need to do anything else here

        else # no chunk handling
          if block_given?
            yield [hash]  # do something with the hash in the block (better to use chunking here)
          else
            result << hash
          end
        end
      end
    ensure
      $/ = old_row_sep   # make sure this stupid global variable is always reset to it's previous value after we're done!
    end
    if block_given?
      return chunk_count  # when we do processing through a block we only care how many chunks we processed
    else
      return result # returns either an Array of Hashes, or an Array of Arrays of Hashes (if in chunked mode)
    end
  end

  def SmarterCSV.process_csv(*args)
    warn "[DEPRECATION] `process_csv` is deprecated.  Please use `process` instead."
    SmarterCSV.process(*args)
  end
end