parser: implement basic dosini parsing

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

parser/lexer_runes.go

@@ -1,9 +1,35 @@
 package parser
 
 import (
+	"strings"
+
 	"asciigoat.org/core/lexer"
 )
 
+const (
+	RuneComment      = ';' // RuneComment is the standard dosini comment character
+	RuneCommentExtra = '#' // RuneCommentExtra is UNIX shell's comment character
+	RuneSectionStart = '[' // RuneSectionStart indicates the start of a section declaration
+	RuneSectionEnd   = ']' // RuneSectionEnd indiciates the end of a section declaration
+	RuneFieldEqual   = '=' // RuneFieldEqual separates field keys from their values
+)
+
+var (
+	// RunesComment is a string containing all runes acceptable to start comments
+	RunesComment = string([]rune{
+		RuneComment,
+		RuneCommentExtra,
+	})
+	// RunesSpecial is a string containing all the runes with special meaning
+	RunesSpecial = string([]rune{
+		RuneComment,
+		RuneCommentExtra,
+		RuneSectionStart,
+		RuneSectionEnd,
+		RuneFieldEqual,
+	})
+)
+
 var (
 	// IsNewLine tells if the rune indicates a line break or the start of one
 	IsNewLine = lexer.NewIsIn("\r\n")
@@ -13,4 +39,29 @@ var (
 	IsSpace = lexer.IsSpace
 	// IsNotSpace tells if the rune is not considered whitespace by Unicode
 	IsNotSpace = lexer.NewIsNot(IsSpace)
+	// IsCommentStart ...
+	IsCommentStart = lexer.NewIsIn(RunesComment)
 )
+
+// IsSpaceNotNewLine indicates a rune is whitespace but not a new line
+func IsSpaceNotNewLine(r rune) bool {
+	return IsSpace(r) && !IsNewLine(r)
+}
+
+// IsSectionStart indicates the rune starts the section declaration
+func IsSectionStart(r rune) bool { return r == RuneSectionStart }
+
+// IsSectionEnd indicates the rune ends the section declaration
+func IsSectionEnd(r rune) bool { return r == RuneSectionEnd }
+
+// IsName indicates a rune is acceptable for section or field names
+func IsName(r rune) bool {
+	switch {
+	case IsSpace(r):
+		return false
+	case strings.ContainsRune(RunesSpecial, r):
+		return false
+	default:
+		return true
+	}
+}