package parser import "io" import "os" import "path/filepath" import "git.tebibyte.media/sashakoshka/arf/file" import "git.tebibyte.media/sashakoshka/arf/lexer" // ParsingOperation holds information about an ongoing parsing operation. type ParsingOperation struct { modulePath string token lexer.Token tokens []lexer.Token tokenIndex int tree *SyntaxTree } // Parse reads the files located in the module specified by modulePath, and // converts them into an abstract syntax tree. func Parse (modulePath string) (tree *SyntaxTree, err error) { parser := ParsingOperation { modulePath: modulePath } if parser.modulePath[len(parser.modulePath) - 1] != '/' { parser.modulePath += "/" } var moduleFiles []os.DirEntry moduleFiles, err = os.ReadDir(parser.modulePath) if err != nil { return } for _, entry := range moduleFiles { if filepath.Ext(entry.Name()) != ".arf" || entry.IsDir() { continue } var sourceFile *file.File sourceFile, err = file.Open(parser.modulePath + entry.Name()) if err != nil { return } // parse the tokens into the module err = parser.parse(sourceFile) } tree = parser.tree return } // parse parses a file and adds it to the syntax tree. func (parser *ParsingOperation) parse (sourceFile *file.File) (err error) { var tokens []lexer.Token tokens, err = lexer.Tokenize(sourceFile) if err != nil { return } // reset the parser if parser.tree == nil { parser.tree = &SyntaxTree { } } if len(tokens) == 0 { return } parser.tokens = tokens parser.token = tokens[0] parser.tokenIndex = 0 err = parser.parseMeta() if err != nil { return } err = parser.parseBody() if err != nil { return } return } // 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) { if len(allowed) == 0 { return } for _, kind := range allowed { if parser.token.Is(kind) { return } } message := "unexpected " + parser.token.Kind().Describe() + " token, expected " for index, allowedItem := range allowed { if index > 0 { if index == len(allowed) - 1 { message += " or " } else { message += ", " } } message += allowedItem.Describe() } err = file.NewError ( parser.token.Location(), message, 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) { parser.tokenIndex ++ if parser.tokenIndex >= len(parser.tokens) { return io.EOF } parser.token = parser.tokens[parser.tokenIndex] err = parser.expect(allowed...) return } // previousToken goes back one token. If the parser is already at the beginning, // this does nothing. func (parser *ParsingOperation) previousToken () { parser.tokenIndex -- if parser.tokenIndex < 0 { parser.tokenIndex = 0 } parser.token = parser.tokens[parser.tokenIndex] return }