From 7a5dc59929f7addabfbaf68721cbe72e03f70fad Mon Sep 17 00:00:00 2001
From: Alejandro Mery <amery@jpi.io>
Date: Wed, 30 Aug 2023 02:27:46 +0100
Subject: [PATCH] parser: WIP

Signed-off-by: Alejandro Mery <amery@jpi.io>
---
 parser/lexer.go       | 46 +++++++++++++++++++++++++++++++------------
 parser/lexer_error.go |  4 ++++
 parser/lexer_runes.go |  6 ++++++
 3 files changed, 43 insertions(+), 13 deletions(-)

diff --git a/parser/lexer.go b/parser/lexer.go
index 5ee901e..52730cd 100644
--- a/parser/lexer.go
+++ b/parser/lexer.go
@@ -30,24 +30,23 @@ func (p *Parser) lexStart() (lexer.StateFn, error) {
 			// whitespace
 			p.src.Discard()
 			p.pos.Step()
-		default:
-			// token
+		case IsCommentStart(r):
+			// switch to comment lexer
 			p.src.UnreadRune()
-			return p.lexToken, nil
+			return p.lexComment, nil
+		case IsSectionStart(r):
+			// section
+			p.src.Discard()
+			p.pos.Step()
+			return p.lexSectionStart, nil
+		default:
+			// entry
+			p.src.UnreadRune()
+			return p.lexEntryStart, nil
 		}
 	}
 }
 
-func (p *Parser) lexToken() (lexer.StateFn, error) {
-	p.src.AcceptAll(IsNotSpace)
-
-	s := p.src.Emit()
-	log.Printf("%s: %s: %q", p.pos, "token", s)
-	p.pos.StepN(len(s))
-
-	return p.lexStart, nil
-}
-
 func (p *Parser) lexNewLine(r1 rune) {
 	// r1 is warrantied to be either \n or \r
 	r2, _, err := p.src.ReadRune()
@@ -77,3 +76,24 @@ func (p *Parser) lexNewLine(r1 rune) {
 		panic("unreachable")
 	}
 }
+
+func (p *Parser) lexComment() (lexer.StateFn, error) {
+	// until the end of the line
+	p.src.AcceptAll(IsNotNewLine)
+
+	err := p.OnComment(p.pos, p.src.Emit())
+	return p.lexStart, err
+}
+
+func (*Parser) lexSectionStart() (lexer.StateFn, error) { return nil, nil }
+func (*Parser) lexEntryStart() (lexer.StateFn, error)   { return nil, nil }
+
+func (p *Parser) lexToken() (lexer.StateFn, error) {
+	p.src.AcceptAll(IsNotSpace)
+
+	s := p.src.Emit()
+	log.Printf("%s: %s: %q", p.pos, "token", s)
+	p.pos.StepN(len(s))
+
+	return p.lexStart, nil
+}
diff --git a/parser/lexer_error.go b/parser/lexer_error.go
index 9eaa98b..afe6fab 100644
--- a/parser/lexer_error.go
+++ b/parser/lexer_error.go
@@ -13,3 +13,7 @@ func (p *Parser) emitError(content string, err error) (lexer.StateFn, error) {
 		return nil, err
 	}
 }
+
+func (p *Parser) emitInvalidRune(r rune) (lexer.StateFn, error) {
+	return p.emitError(string([]rune{r}), lexer.ErrUnacceptableRune)
+}
diff --git a/parser/lexer_runes.go b/parser/lexer_runes.go
index 25d37d6..79f3b1a 100644
--- a/parser/lexer_runes.go
+++ b/parser/lexer_runes.go
@@ -11,4 +11,10 @@ var (
 	IsNotNewLine = lexer.NewIsNot(IsNewLine)
 	// IsNotSpace tells if a rune is anything other than whitespace
 	IsNotSpace = lexer.NewIsNot(IsSpace)
+
+	IsCommentStart = lexer.NewIsIn(";#")
 )
+
+func IsSectionStart(r rune) bool {
+	return r == '['
+}