1 files changed, 144 insertions, 0 deletions
diff --git a/lib/csv/writer.rb b/lib/csv/writer.rb
new file mode 100644
index 0000000000..2f2ab095d7
--- /dev/null
+++ b/lib/csv/writer.rb
@@ -0,0 +1,144 @@
+# frozen_string_literal: true
+
+require_relative "match_p"
+require_relative "row"
+
+using CSV::MatchP if CSV.const_defined?(:MatchP)
+
+class CSV
+  class Writer
+    attr_reader :lineno
+    attr_reader :headers
+
+    def initialize(output, options)
+      @output = output
+      @options = options
+      @lineno = 0
+      prepare
+      if @options[:write_headers] and @headers
+        self << @headers
+      end
+    end
+
+    def <<(row)
+      case row
+      when Row
+        row = row.fields
+      when Hash
+        row = @headers.collect {|header| row[header]}
+      end
+
+      @headers ||= row if @use_headers
+      @lineno += 1
+
+      line = row.collect(&@quote).join(@column_separator) + @row_separator
+      if @output_encoding
+        line = line.encode(@output_encoding)
+      end
+      @output << line
+
+      self
+    end
+
+    def rewind
+      @lineno = 0
+      @headers = nil if @options[:headers].nil?
+    end
+
+    private
+    def prepare
+      @encoding = @options[:encoding]
+
+      prepare_header
+      prepare_format
+      prepare_output
+    end
+
+    def prepare_header
+      headers = @options[:headers]
+      case headers
+      when Array
+        @headers = headers
+        @use_headers = true
+      when String
+        @headers = CSV.parse_line(headers,
+                                  col_sep: @options[:column_separator],
+                                  row_sep: @options[:row_separator],
+                                  quote_char: @options[:quote_character])
+        @use_headers = true
+      when true
+        @headers = nil
+        @use_headers = true
+      else
+        @headers = nil
+        @use_headers = false
+      end
+      return unless @headers
+
+      converter = @options[:header_fields_converter]
+      @headers = converter.convert(@headers, nil, 0)
+      @headers.each do |header|
+        header.freeze if header.is_a?(String)
+      end
+    end
+
+    def prepare_format
+      @column_separator = @options[:column_separator].to_s.encode(@encoding)
+      row_separator = @options[:row_separator]
+      if row_separator == :auto
+        @row_separator = $INPUT_RECORD_SEPARATOR.encode(@encoding)
+      else
+        @row_separator = row_separator.to_s.encode(@encoding)
+      end
+      quote_character = @options[:quote_character]
+      quote = lambda do |field|
+        field = String(field)
+        encoded_quote_character = quote_character.encode(field.encoding)
+        encoded_quote_character +
+          field.gsub(encoded_quote_character,
+                     encoded_quote_character * 2) +
+          encoded_quote_character
+      end
+      if @options[:force_quotes]
+        @quote = quote
+      else
+        quotable_pattern =
+          Regexp.new("[\r\n".encode(@encoding) +
+                     Regexp.escape(@column_separator) +
+                     Regexp.escape(quote_character.encode(@encoding)) +
+                     "]".encode(@encoding))
+        @quote = lambda do |field|
+          if field.nil?  # represent +nil+ fields as empty unquoted fields
+            ""
+          else
+            field = String(field)  # Stringify fields
+            # represent empty fields as empty quoted fields
+            if field.empty? or quotable_pattern.match?(field)
+              quote.call(field)
+            else
+              field  # unquoted field
+            end
+          end
+        end
+      end
+    end
+
+    def prepare_output
+      @output_encoding = nil
+      return unless @output.is_a?(StringIO)
+
+      output_encoding = @output.internal_encoding || @output.external_encoding
+      if @encoding != output_encoding
+        if @options[:force_encoding]
+          @output_encoding = output_encoding
+        else
+          compatible_encoding = Encoding.compatible?(@encoding, output_encoding)
+          if compatible_encoding
+            @output.set_encoding(compatible_encoding)
+            @output.seek(0, IO::SEEK_END)
+          end
+        end
+      end
+    end
+  end
+end