parser: Unescaped [WIP]

Signed-off-by: Alejandro Mery <amery@jpi.io>

parser/error.go

@@ -35,9 +35,28 @@ func NewErrIncompleteQuotedString(p *TextParser) *lexer.Error {
 	return newErrIncomplete(p, "incomplete quoted string")
 }
 
+// NewErrIncompleteEscaped returns a [lexer.Error]
+// indicating the text being parsed wasn't correctly
+// terminated
+func NewErrIncompleteEscaped(p *TextParser) *lexer.Error {
+	return newErrIncomplete(p, "incomplete escaped string")
+}
+
 func newErrIncomplete(p *TextParser, hint string) *lexer.Error {
 	pos, s := p.Emit()
 	pos.Add(GetPositionalLength(s))
 
 	return NewError(pos, s, hint, fs.ErrInvalid)
 }
+
+// NewErrInvalidEscapeSequence returns a [lexer.Error] indicating
+// the specified sequence, at the end of the accepted buffer,
+// is invalid
+func NewErrInvalidEscapeSequence(p *TextParser, seq string) *lexer.Error {
+	pos, s := p.Position(), p.String()
+
+	s = s[:len(s)-len(seq)]
+	pos.Add(GetPositionalLength(s))
+
+	return NewError(pos, seq, "invalid escape character", fs.ErrInvalid)
+}

parser/text_quoted.go

@@ -33,22 +33,34 @@ func (p *TextParser) AcceptQuotedString() (string, bool, error) {
 }
 
 func lexQuotedString(p *TextParser) (string, *lexer.Error) {
+	s, ok, err := lexQuotedStringNoEscape(p)
+	switch {
+	case err != nil:
+		return "", err
+	case ok:
+		return s, nil
+	default:
+		// escape character detected
+		return lexQuotedStringEscaped(p)
+	}
+}
+
+func lexQuotedStringNoEscape(p *TextParser) (string, bool, *lexer.Error) {
 	for {
 		r, _, err := p.ReadRune()
 		switch {
 		case err != nil:
 			// incomplete
-			return "", NewErrIncompleteQuotedString(p)
+			return "", false, NewErrIncompleteQuotedString(p)
 		case r == RuneQuotes:
-			// end, remove quotes and process escaped characters
-			return lexReturnUnescapedQuotedString(p)
+			// end, just remove the quotes
+			s := p.String()
+			l := len(s)
+			return s[1 : l-1], true, nil
 		case r == RuneEscape:
-			// escaped, take another
-			_, _, err := p.ReadRune()
-			if err != nil {
-				// incomplete
-				return "", NewErrIncompleteQuotedString(p)
-			}
+			// things just got complicated...
+			p.UnreadRune()
+			return "", false, nil
 		case IsNewLine(r):
 			// new lines within quoted values are acceptable
 			p.UnreadRune()
@@ -59,22 +71,48 @@ func lexQuotedString(p *TextParser) (string, *lexer.Error) {
 	}
 }
 
-func lexReturnUnescapedQuotedString(p *TextParser) (string, *lexer.Error) {
-	// remove quotes
-	s := p.String()
-	l := len(s)
-	s = s[1 : l-1]
+// Unquoted removes quotes the content and unescapes the content
+func lexQuotedStringEscaped(p *TextParser) (string, *lexer.Error) {
+	var result strings.Builder
 
-	if strings.ContainsRune(s, RuneEscape) {
-		// TODO: implement unescaping
-		err := NewError(p.Position(), s, "escaped characters", lexer.ErrNotImplemented)
+	// append what was accepted before the escape character
+	_, _ = result.WriteString(p.String()[1:])
+
+	for {
+		r, _, err := p.ReadRune()
+		switch {
+		case err != nil:
+			// incomplete quoted
+			return "", NewErrIncompleteQuotedString(p)
+		case r == RuneQuotes:
+			// end
+			return result.String(), nil
+		case r == RuneEscape:
+			// escaped
+			r2, _, err := p.ReadRune()
+			switch {
+			case err != nil:
+				// incomplete escaped
+				return "", NewErrIncompleteEscaped(p)
+			case IsNewLine(r2):
+				// escaped new line, skip
+				p.UnreadRune()
+				p.AcceptNewLine()
+			default:
+				// TODO: check valid escape character and
+				// append to result
+				s := string([]rune{r, r2})
+				err := NewErrInvalidEscapeSequence(p, s)
 				return "", err
 			}
-
-	return s, nil
+		default:
+			// normal, append to result
+			_, _ = result.WriteRune(r)
+		}
+	}
 }
 
-// Unquoted removes quotes the content and unescapes the content
+// Unquoted removes quotes and unescapes the content
 func Unquoted(s string) (string, error) {
 	var p TextParser
 	if s == "" {