parser: implement basic dosini parsing

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

parser/lexer.go

@@ -23,9 +23,17 @@ func (p *Parser) lexStart() (lexer.StateFn, error) {
 		case IsSpace(r):
 			// whitespace
 			p.stepRune()
-		default:
+		case IsCommentStart(r):
+			// switch to comment lexer
 			p.src.UnreadRune()
-			return p.lexToken, nil
+			return p.lexComment, nil
+		case IsSectionStart(r):
+			// section
+			return p.lexSectionStart, nil
+		default:
+			// entry
+			p.src.UnreadRune()
+			return p.lexEntryStart, nil
 		}
 	}
 }
@@ -59,9 +67,78 @@ func (p *Parser) lexMoreNewLine(r1 rune) {
 	}
 }
 
-func (p *Parser) lexToken() (lexer.StateFn, error) {
-	p.src.AcceptAll(IsNotSpace)
+func (p *Parser) lexComment() (lexer.StateFn, error) {
+	// until the end of the line
+	p.src.AcceptAll(IsNotNewLine)
+
+	err := p.emitString(TokenComment)
+	return p.lexStart, err
+}
+
+func (p *Parser) lexSectionStart() (lexer.StateFn, error) {
+	if err := p.emitString(TokenSectionStart); err != nil {
+		return nil, err
+	}
+
+	// remove whitespace between `[` and the name
+	if p.src.AcceptAll(IsSpaceNotNewLine) {
+		p.stepString()
+	}
+
+	if !p.src.AcceptAll(IsName) {
+		// no name
+		return p.emitError("section name missing", lexer.ErrUnacceptableRune)
+	}
+
+	if err := p.emitString(TokenSectionName); err != nil {
+		return nil, err
+	}
+
+	// remove whitespace between the name andthe closing `]`
+	if p.src.AcceptAll(IsSpaceNotNewLine) {
+		p.stepString()
+	}
+
+	r, _, err := p.src.ReadRune()
+	switch {
+	case err != nil:
+		return p.emitError("", err)
+	case IsSectionEnd(r):
+		err := p.emitString(TokenSectionEnd)
+		return p.lexStart, err
+	default:
+		return p.emitInvalidRune(r)
+	}
+}
+
+func (p *Parser) lexEntryStart() (lexer.StateFn, error) {
+	p.src.AcceptAll(IsName)
+	if err := p.emitString(TokenFieldKey); err != nil {
+		return nil, err
+	}
+
+	// ignore whitespace between key and the '=' sign
+	if p.src.AcceptAll(IsSpaceNotNewLine) {
+		p.stepString()
+	}
+
+	r, _, err := p.src.ReadRune()
+	switch {
+	case err != nil:
+		return p.emitError("", err)
+	case r != RuneFieldEqual:
+		return p.emitInvalidRune(r)
+	}
+
+	// ignore whitespace between the '=' and the value
+	if p.src.AcceptAll(IsSpaceNotNewLine) {
+		p.stepString()
+	}
+
+	p.src.AcceptAll(IsNotNewLine)
+	if err := p.emitString(TokenFieldValue); err != nil {
+		return nil, err
+	}
 
-	err := p.emitString(TokenUnknown)
 	return p.lexStart, err
 }