diff --git a/src/compiler/compiler.go b/src/compiler/compiler.go
index 35c7da7..660e461 100644
--- a/src/compiler/compiler.go
+++ b/src/compiler/compiler.go
@@ -1,7 +1,259 @@
-package main 
+package main
 
-import "fmt"
+import (
+	"bufio"
+	"fmt"
+	"io"
+	"log"
+	"os"
+	"strings"
+)
+
+var tokens []Token
+var buffer []rune
+
+type TokenType int
+const (
+	TextFragment TokenType = iota
+	QuestionEnd               
+	ElementDashStart          
+	ElementPlusStart          
+	Identifier                
+	IdentifierStart            
+	IdentifierEnd             
+	SectionStart
+	SectionEnd
+)
+
+type Token struct {
+	tokenType   TokenType;
+	content        string;
+	row		        int32;
+	column          int32;
+} 
+
+type Flashcard struct {
+	question string;
+	answer   string;
+}
+
+func toString (ttype *TokenType) string {
+	switch *ttype {
+	case TextFragment:
+		return "TextFragment"
+	case QuestionEnd:
+		return "QuestionEnd"               
+	case ElementDashStart:
+		return "ElementDashStart"          
+	case ElementPlusStart:
+		return "ElementPlusStart"          
+	case Identifier:
+		return "Identifier"                
+	case IdentifierStart:
+		return "IdentifierStart"            
+	case IdentifierEnd:
+		return "IdentifierEnd"             
+	case SectionStart:
+		return "SectionStart"             
+	case SectionEnd:
+		return "SectionEnd"             
+	default:
+		return "NOT_DEFINED"
+	}
+}
+
+type LexingErr struct {
+	message string;	
+	row	     int32;
+	column   int32;
+}
+
+func (e LexingErr) Error() string {
+	return fmt.Sprintf("%d:%d - %s", e.row, e.column, e.message)
+}
+
+var	row int32          =  1
+var	column int32       =  1
+var	previous_row int32 = -1
+var	previous_col int32 = -1
+var can_have_text bool = false
+
+func makePostTextToken(ttype TokenType, tokenLen int32) {
+	if (len(strings.Trim(string(buffer), " \n")) - 1 > 0) {
+		textFragment := []rune{}
+		for i := 0; i < len(buffer) - int(tokenLen); i++ {
+			element := buffer[i]
+			textFragment = append(textFragment, element)
+		}
+		tokens = append(
+			tokens,
+			Token{
+				tokenType: TextFragment,
+				content: string(textFragment),
+				row: int32(previous_row),
+				column: int32(previous_col),
+			},
+		)
+	}
+	tokens = append(
+		tokens,
+		Token{
+			tokenType: ttype,
+			content: string(buffer[len(buffer)-int(tokenLen):]),
+			row: int32(row),
+			column: int32(column),
+		},
+	)
+	previous_row = row
+	previous_col = column
+	buffer = []rune{}
+}
+
+func tokenize(contents string) error {
+	tokens = []Token{} 
+	buffer = []rune{} 
+
+	previous_row = -1
+	previous_col = -1
+	reader := bufio.NewReader(
+		strings.NewReader(contents),
+	)
+	for {
+		c, sz, err := reader.ReadRune()
+		// TODO previous token start and end
+		if err != nil {
+			if err == io.EOF {
+				break
+			} else {
+				log.Fatal(err)
+			}
+		}
+		_ = sz
+		if (c == '\n') {
+			row += 1
+			column = 1
+		}
+		buffer = append(buffer, c)
+
+		trimmedBuffer := strings.Trim(string(buffer), " \n")
+		if (len(trimmedBuffer) > 2) {
+			lastTwo := buffer[len(trimmedBuffer) - 1:]
+			switch string(lastTwo) {
+			case "|>":
+				if (len(trimmedBuffer) - 2 > 0 && !can_have_text) {
+					return LexingErr{"Text cannot be here", previous_row, previous_col}
+				}
+				makePostTextToken(SectionStart, 2)
+				can_have_text = true
+				continue
+			case "<|":
+				if (len(trimmedBuffer) - 2 > 0 && !can_have_text) {
+					return LexingErr{"Text cannot be here", previous_row, previous_col}
+				}
+				makePostTextToken(SectionEnd, 2)
+				can_have_text = false 
+				continue
+			}
+		}
+
+		switch c {
+		case ']':
+			if (len(trimmedBuffer) - 1 > 0 && !can_have_text) {
+				return LexingErr{"Text cannot be here", row, column}
+			}
+			tokens = append(
+				tokens,
+				Token{
+					tokenType: ElementDashStart,
+					content: "[",
+					row: int32(row),
+					column: int32(column),
+				},
+			)
+			if (len(buffer) - 1 > 1) {
+				textFragment := []rune{}
+				trimmedStr := strings.Trim(string(buffer), " ")
+				for i := 1; i <  len(trimmedStr) - 1; i++ {
+					element := trimmedStr[i]
+					textFragment = append(textFragment, rune(element))
+				}
+				tokens = append(
+					tokens,
+					Token{
+						tokenType: Identifier,
+						content: string(textFragment),
+						row: int32(previous_row),
+						column: int32(previous_col),
+					},
+				)
+				can_have_text = true
+			}
+			tokens = append(
+				tokens,
+				Token{
+					tokenType: ElementDashStart,
+					content: "]",
+					row: int32(row),
+					column: int32(column),
+				},
+			)
+			previous_row = row
+			previous_col = column
+			buffer = []rune{}
+		case '+':
+			if (len(trimmedBuffer) - 1 > 0 && !can_have_text) {
+				return LexingErr{"Text cannot be here", previous_row, previous_col}
+			}
+			makePostTextToken(ElementPlusStart, 1)
+			can_have_text = true
+		case '-':
+			// fmt.Printf("%s %d\n", trimmedBuffer, len(trimmedBuffer))
+			if (len(trimmedBuffer) - 1 > 0 && !can_have_text) {
+				return LexingErr{"Text cannot be here", previous_row, previous_col}			}
+			makePostTextToken(ElementDashStart, 1)
+			can_have_text = true
+		case '>':
+			if (len(trimmedBuffer) - 1 > 0 && !can_have_text) {
+				return LexingErr{"Text cannot be here", previous_row, previous_col}			
+			}
+			makePostTextToken(QuestionEnd, 1)
+			can_have_text = false 
+		}
+		column += 1
+	}
+	return nil
+}
 
 func main() {
-	fmt.Println("Hello from compiler!")
+	// openAndExtractFileContents
+	log.Println("Compilation started")
+
+	file, err := os.ReadFile("./input.mdem")
+	if (err != nil) { log.Fatal("Cannot open the input file")
+		return
+	}
+	fileContents := string(file)
+
+	err = tokenize(fileContents)
+	if (err != nil) {
+		fmt.Printf("%s\n", err.Error())	
+		return
+	}
+
+	for i := 0; i < len(tokens); i++ {
+		token := tokens[i]
+		content := token.content
+		if (token.tokenType == TextFragment) {
+			content = strings.Replace(strings.Trim(content, " "), "\n", "\\n", -1)
+		}
+		fmt.Printf(
+			"%s: \"%s\" %d:%d\n",
+			toString(&token.tokenType),
+			content,
+			token.row,
+			token.column,
+		)
+	} 
+
+	log.Println("Compilation completed")
 }
diff --git a/src/compiler/go.mod b/src/compiler/go.mod
index 58dc732..d9afeb0 100644
--- a/src/compiler/go.mod
+++ b/src/compiler/go.mod
@@ -1,3 +1,5 @@
 module github.com/jorenchik/mdemory/src/compiler
 
 go 1.22.5
+
+require golang.org/x/text v0.16.0
diff --git a/src/compiler/go.sum b/src/compiler/go.sum
new file mode 100644
index 0000000..e85a4c4
--- /dev/null
+++ b/src/compiler/go.sum
@@ -0,0 +1,2 @@
+golang.org/x/text v0.16.0 h1:a94ExnEXNtEwYLGJSIUxnWoxoRz/ZcCsV63ROupILh4=
+golang.org/x/text v0.16.0/go.mod h1:GhwF1Be+LQoKShO3cGOHzqOgRrGaYc9AvblQOmPVHnI=