feat(scanner): main markdown features

scanner/scanner.go

@@ -0,0 +1,145 @@
+package scanner
+
+import (
+	"bufio"
+	"fmt"
+	"log"
+	"os"
+)
+
+type Scanner struct {
+	scan    *bufio.Scanner
+	isAtEnd bool    // indicates if EOF is hit
+	curLine []rune  // contains the characters of the current line
+	curChar rune    // contains the character at the linePos of curLine
+	linePos uint    // indicates the scanners position on curLine
+	line    uint    // indicates the scanners position in the file
+	tokens  []Token // holds scanned token
+}
+
+// Returns a new instance of scanner.Scanner.
+// To do so, it opens the file, creates a bufio.Scanner with it, scans the first line and assigns all values in the scanner.Scanner struct accordingly
+func NewScanner(fileName string) Scanner {
+	file, err := os.Open(fileName)
+	if err != nil {
+		log.Fatalln("couldn't open file", err)
+	}
+	scan := bufio.NewScanner(file)
+	// get first line
+	scan.Scan()
+
+	firstLine := []rune(scan.Text())
+
+	return Scanner{
+		scan:    scan,
+		curLine: firstLine,
+		curChar: firstLine[0],
+		line:    0,
+		linePos: 0,
+	}
+}
+
+// creates a scanner.Token struct with kind, position, value, line and appends it to the scanner.Scanner.tokens array
+func (s *Scanner) addToken(kind TokenKind, value string) {
+	s.tokens = append(s.tokens, Token{
+		Pos:   s.linePos,
+		Kind:  kind,
+		Value: value,
+		Line:  s.line,
+	})
+}
+
+// getter for scanner.Scanner.tokens
+func (s *Scanner) Tokens() []Token {
+	return s.tokens
+}
+
+// performs a lookup for the Token.Kind value for each token and prints the token values
+func (s *Scanner) PrintTokens() {
+	for _, token := range s.tokens {
+		fmt.Printf("[ '%s' | %d | %d | '%s' ]\n",
+			TOKEN_LOOKUP_MAP[token.Kind],
+			token.Pos,
+			token.Line,
+			token.Value,
+		)
+	}
+}
+
+// getter for scanner.Scanner.isAtEnd
+func (s *Scanner) atEnd() bool {
+	return s.isAtEnd
+}
+
+// increments s.linePos by one and assigns the next char to s.curChar
+func (s *Scanner) advance() {
+	if s.linePos+1 >= uint(len(s.curLine)) {
+		s.curChar = '\n'
+		s.linePos++
+		return
+	}
+
+	s.linePos++
+	s.curChar = s.curLine[s.linePos]
+}
+
+// increments s.line by one, assigns the next line to s.curChar and assigns the next char to s.curChar
+func (s *Scanner) advanceLine() {
+	ok := s.scan.Scan()
+
+	if s.scan.Err() != nil || !ok {
+		s.isAtEnd = true
+		return
+	}
+
+	s.curLine = []rune(s.scan.Text())
+	s.line++
+	s.linePos = 0
+	for len(s.curLine) == 0 {
+		s.scan.Scan()
+		s.curLine = []rune(s.scan.Text())
+		s.line++
+	}
+	s.curChar = s.curLine[s.linePos]
+}
+
+// parses the file given to the Scanner line by line
+func (s *Scanner) Parse() {
+	for !s.atEnd() {
+		switch s.curChar {
+		case '#':
+			s.addToken(HASH, "")
+		case '_':
+			s.addToken(UNDERSCORE, "")
+		case '*':
+			s.addToken(STAR, "")
+		case '\n':
+			s.addToken(NEWLINE, "")
+			s.advanceLine()
+			continue
+		case '-':
+			s.addToken(DASH, "")
+		case '[':
+			s.addToken(STRAIGHTBRACEOPEN, "")
+		case ']':
+			s.addToken(STRAIGHTBRACECLOSE, "")
+		case '(':
+			s.addToken(PARENOPEN, "")
+		case ')':
+			s.addToken(PARENCLOSE, "")
+		case '`':
+			s.addToken(BACKTICK, "")
+		default:
+			var res []rune
+			for s.curChar != '\n' {
+				res = append(res, s.curChar)
+				s.advance()
+			}
+			s.addToken(TEXT, string(res))
+			s.addToken(NEWLINE, "")
+			s.advanceLine()
+			continue
+		}
+		s.advance()
+	}
+}