parser: Unquoted(), AcceptQuotedString()

TODO: reduce quoted strings with escaped characters

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

parser/text_quoted.go

@@ -0,0 +1,97 @@
+package parser
+
+import (
+	"strings"
+
+	"asciigoat.org/core/lexer"
+)
+
+// AcceptQuotedString consumes a quoted string from the source
+// and returns it unquoted and unescaped
+func (p *TextParser) AcceptQuotedString() (string, bool, error) {
+	r, _, err := p.ReadRune()
+	switch {
+	case err != nil:
+		// nothing here
+		return "", false, err
+	case r != RuneQuotes:
+		// not for us
+		p.UnreadRune()
+		return "", false, nil
+	default:
+		// let's roll
+		s, err := lexQuotedString(p)
+		switch {
+		case err != nil:
+			// bad quoted string
+			return "", false, err
+		default:
+			// success
+			return s, true, nil
+		}
+	}
+}
+
+func lexQuotedString(p *TextParser) (string, *lexer.Error) {
+	for {
+		r, _, err := p.ReadRune()
+		switch {
+		case err != nil:
+			// incomplete
+			return "", NewErrIncompleteQuotedString(p)
+		case r == RuneQuotes:
+			// end, remove quotes and process escaped characters
+			return lexReturnUnescapedQuotedString(p)
+		case r == RuneEscape:
+			// escaped, take another
+			_, _, err := p.ReadRune()
+			if err != nil {
+				// incomplete
+				return "", NewErrIncompleteQuotedString(p)
+			}
+		case IsNewLine(r):
+			// new lines within quoted values are acceptable
+			p.UnreadRune()
+			p.AcceptNewLine()
+		default:
+			// continue
+		}
+	}
+}
+
+func lexReturnUnescapedQuotedString(p *TextParser) (string, *lexer.Error) {
+	// remove quotes
+	s := p.String()
+	l := len(s)
+	s = s[1 : l-1]
+
+	if strings.ContainsRune(s, RuneEscape) {
+		// TODO: implement unescaping
+		err := NewError(p.Position(), s, "escaped characters", lexer.ErrNotImplemented)
+		return "", err
+	}
+
+	return s, nil
+}
+
+// Unquoted removes quotes the content and unescapes the content
+func Unquoted(s string) (string, error) {
+	var p TextParser
+	if s == "" {
+		return "", nil
+	}
+
+	p.InitString(s)
+	unquoted, ok, err := p.AcceptQuotedString()
+	switch {
+	case err != nil:
+		// bad string
+		return "", err
+	case ok:
+		// success
+		return unquoted, nil
+	default:
+		// not quoted
+		return s, nil
+	}
+}