X-Git-Url: http://nitlanguage.org

diff --git a/lib/csv/csv.nit b/lib/csv/csv.nit
index e3d0c0b..257d565 100644
--- a/lib/csv/csv.nit
+++ b/lib/csv/csv.nit
@@ -12,13 +12,54 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-# CSV output facilities
+# CSV document handling.
 module csv
 
+# Specifies a CSV format.
+class CsvFormat
+	# The character that delimits escaped value.
+	#
+	# The delimiter is escaped by doubling it.
+	var delimiter: Char
+
+	# The character that split each cell in a row.
+	var separator: Char
+
+	# The character that ends a row (end of line).
+	var eol: String
+
+	# Escape sequence for the delimiter.
+	private var escaping = "{delimiter}{delimiter}" is lazy
+
+	# Escape the specified cell.
+	private fun escape_cell(cell: String): Text do
+		var result = new RopeBuffer
+		result.add delimiter
+		result.append cell.replace(delimiter, escaping)
+		result.add delimiter
+		return result
+	end
+
+	# Can the specified value be inserted without any escaping?
+	private fun is_value_clean(value: String): Bool do
+		for c in value.chars do
+			if c == delimiter then return false
+			if c == separator then return false
+			if eol.chars.has(c) then return false
+		end
+		return true
+	end
+end
+
 # A CSV document representation.
 class CsvDocument
 	super Streamable
 
+	# The format to use.
+	#
+	# Defaults to `rfc4180`.
+	var format: CsvFormat = rfc4180 is writable
+
 	# The header.
 	#
 	# Contains the name of all fields in this table.
@@ -45,26 +86,96 @@ class CsvDocument
 		records.add(record)
 	end
 
-	private fun write_line_to(line: Collection[String], stream: OStream)
-	do
-		var i = line.iterator
-		if i.is_ok then
-			stream.write(i.item)
+	redef fun write_to(stream) do
+		var writer = new CsvWriter.with_format(stream, format)
+		writer.write_sequence(header)
+		for record in records do writer.write_sequence(record)
+	end
+
+	# Deprecated alias for `write_to_file`.
+	fun save(file: String) do write_to_file(file)
+end
+
+# Appends CSV rows to a file.
+#
+# By default, uses the format recommended by RFC 4180 (see `rfc4180`).
+#
+# Note: If a row contains only an empty cell, its representation is
+# undistinguishable from an empty line. This is because the empty values are
+# always written unescaped in order to avoid them to be interpreted as escaped
+# delimiters by some parsers.
+#
+# ~~~nit
+# var out = new StringOStream
+# var writer = new CsvWriter(out)
+# writer.write_row(1, 2.0, "foo\nbar")
+# writer.write_sequence([""])
+# assert out.to_s == """1,2.0,"foo\nbar"\r\n\r\n"""
+# ~~~
+class CsvWriter
+
+	# The output stream.
+	var ostream: OStream
+
+	# The format to use.
+	#
+	# Defaults to `rfc4180`.
+	var format: CsvFormat = rfc4180
+
+	# Do we escape all cells (except empty ones)?
+	#
+	# If `false` (the default), escape only cells that contain a metacharacter
+	# of the format. In all cases, empty cells are not escaped. This option
+	# permits to choose between the optimization of the performances (when
+	# `true`) and optimization of the size of the output (when `false`).
+	#
+	# Note: Escaping may not be correctly recognized by some parsers.
+	var always_escape = false is writable
+
+	# Create a new writer with the specified format.
+	init with_format(ostream:OStream, format: CsvFormat) do
+		self.ostream = ostream
+		self.format = format
+	end
+
+	# Append the specified sequence as a row.
+	#
+	# The representation of each cell is determined by `to_s`.
+	fun write_sequence(row: SequenceRead[Object]) do
+		if not row.is_empty then
+			var i = row.iterator
+			var separator = format.separator.to_s
+			write_cell i.item.to_s
 			i.next
-			while i.is_ok do
-				stream.write(";")
-				stream.write(i.item)
-				i.next
+			for cell in i do
+				ostream.write separator
+				write_cell cell.to_s
 			end
 		end
-		stream.write("\n")
+		ostream.write format.eol
 	end
 
-	redef fun write_to(stream) do
-		write_line_to(header, stream)
-		for record in records do write_line_to(record, stream)
-	end
+	# Append the specified row.
+	#
+	# The representation of each cell is determined by `to_s`.
+	fun write_row(row: Object...) do write_sequence(row)
 
-	# Deprecated alias for `write_to_file`.
-	fun save(file: String) do write_to_file(file)
+	# Close the output stream.
+	fun close do ostream.close
+
+	private fun write_cell(cell: String) do
+		if cell.is_empty then return
+		if not always_escape and format.is_value_clean(cell) then
+			ostream.write cell
+		else
+			ostream.write format.escape_cell(cell)
+		end
+	end
 end
+
+# The CSV format recommended by RFC 4180.
+#
+# * `delimiter`: `'"'`
+# * `separator`: `','`
+# * `eol`: `"\r\n"`
+fun rfc4180: CsvFormat do return once new CsvFormat('"', ',', "\r\n")