first commit

scanner.go

@@ -0,0 +1,61 @@
+package settings
+
+import (
+	"bufio"
+	"fmt"
+	"io"
+	"strings"
+)
+
+var (
+	KeyValueDelimiterChars = []byte{':', '='}
+
+	ErrNoValidDelimiter = fmt.Errorf("no valid delimiter found (use %s)", KeyValueDelimiterCharsToString())
+)
+
+func KeyValueDelimiterCharsToString() string {
+	var builder strings.Builder
+	for i, char := range KeyValueDelimiterChars {
+		builder.WriteString(fmt.Sprintf("'%c'", char))
+		if i < len(KeyValueDelimiterChars)-1 {
+			builder.WriteString(" or ")
+		}
+	}
+	return builder.String()
+}
+
+func LineIsComment(line string) bool {
+	return strings.HasPrefix(line, "//") || strings.HasPrefix(line, "#")
+}
+
+type Scanner struct {
+	lineNumber int
+	scanner    *bufio.Scanner
+}
+
+// returns errors without any key/value.
+// does not clone the strings it extracted.
+func (s *Scanner) ReadNextLine() (key, value string, err error) {
+	for s.scanner.Scan() {
+		s.lineNumber++
+		line := strings.TrimSpace(s.scanner.Text())
+		if len(line) == 0 || LineIsComment(line) {
+			continue
+		}
+		splitIndex := strings.IndexAny(line, string(KeyValueDelimiterChars))
+		if splitIndex == -1 {
+			return "", "", fmt.Errorf("line %d: %w", s.lineNumber, ErrNoValidDelimiter)
+		}
+		key = strings.TrimSpace(line[:splitIndex])
+		value = strings.TrimSpace(line[splitIndex+1:])
+		return
+	}
+	return "", "", io.EOF
+}
+
+func NewScanner(r io.Reader) *Scanner {
+	return &Scanner{
+		lineNumber: 0,
+		scanner:    bufio.NewScanner(r),
+	}
+}