Added metadata parser

parser/meta.go

@@ -1,5 +1,41 @@
 package parser
 
+import "git.tebibyte.media/sashakoshka/arf/file"
+import "git.tebibyte.media/sashakoshka/arf/lexer"
+
+// parseMeta parsese the metadata header at the top of an arf file.
 func (parser *ParsingOperation) parseMeta () (err error) {
-	
+	for {
+		err = parser.expect (
+			lexer.TokenKindName,
+			lexer.TokenKindSeparator)
+		if err != nil { return }
+
+		if parser.token.Is(lexer.TokenKindSeparator) {
+			err = parser.nextToken()
+			return
+		}
+
+		field := parser.token.Value().(string)
+
+		err = parser.nextToken(lexer.TokenKindString)
+		if err != nil { return }
+		value := parser.token.Value().(string)
+		
+		switch field {
+		case "author":
+			parser.tree.author = value
+		case "license":
+			parser.tree.license = value
+		case "require":
+			parser.tree.requires = append(parser.tree.requires, value)
+		default:
+			parser.token.NewError (
+				"unrecognized metadata field: " + field,
+				file.ErrorKindError)
+		}
+
+		err = parser.nextToken(lexer.TokenKindNewline)
+		if err != nil { return }
+	}
 }

parser/parser.go

@@ -70,7 +70,7 @@ func (parser *ParsingOperation) parse (sourceFile *file.File) (err error) {
 // expect takes in a list of allowed token kinds, and returns an error if the
 // current token isn't one of them. If the length of allowed is zero, this
 // function will not return an error.
-func (parser *ParsingOperation) expect (allowed []lexer.TokenKind) (err error) {
+func (parser *ParsingOperation) expect (allowed ...lexer.TokenKind) (err error) {
 	if len(allowed) == 0 { return }
 
 	for _, kind := range allowed {
@@ -78,16 +78,17 @@ func (parser *ParsingOperation) expect (allowed []lexer.TokenKind) (err error) {
 	}
 
 	err = file.NewError (
-		parser.token.Location(), 1,
+		parser.token.Location(),
 		"unexpected token", file.ErrorKindError)
 	return
 }
 
 // nextToken is the same as expect, but it advances to the next token first.
-func (parser *ParsingOperation) nextToken (allowed []lexer.TokenKind) (err error) {
+func (parser *ParsingOperation) nextToken (allowed ...lexer.TokenKind) (err error) {
 	parser.tokenIndex ++
 	if parser.tokenIndex >= len(parser.tokens) { return io.EOF }
 	parser.token = parser.tokens[parser.tokenIndex]
-
+	
+	err = parser.expect(allowed...)
 	return
 }