feat(lexer): Scan alphanumeric

src/lexer/Lexer.kt

@@ -9,25 +9,25 @@ class Lexer(private val source: String) {
 
     fun scan(): List<Token> {
         while (hasNext()) {
-            val token = scanToken()
-            tokens += token
+            tokens += scanToken()
         }
 
+        position.length = 0
         tokens += Token(TokenType.EOF, position)
 
         return tokens
     }
 
     private fun scanToken(): Token {
-        val c = peek()
-        val token = when (c) {
-            '.' -> Token(TokenType.DOT, position)
-            else -> throw Error("Unknown symbol: $c", position)
-        }
+        val char: Char = peek()
 
-        offset++
-        position.column++
-        return token
+        position.length = 1
+
+        return when {
+            char == '.' -> scanDot()
+            char.isLetterOrDigit() -> scanAlphanumeric()
+            else -> throw Error("Unknown symbol: $char", position)
+        }
     }
 
     private fun hasNext(): Boolean {
@@ -41,4 +41,27 @@ class Lexer(private val source: String) {
 
         return source[offset]
     }
+
+    // Scanners
+
+    private fun scanDot(): Token {
+        val token = Token(TokenType.DOT, position)
+        offset++
+        position.column++
+        return token
+    }
+
+    private fun scanAlphanumeric(): Token {
+        val token = Token(TokenType.ALPHANUMERIC, position)
+        offset++
+        position.column++
+
+        while (hasNext() && peek().isLetterOrDigit()) {
+            offset++
+            position.column++
+            position.length++
+        }
+
+        return token
+    }
 }

src/lexer/LexerPosition.kt

@@ -1,5 +1,5 @@
 package lexer
 
-class LexerPosition(val line: Int, var column: Int, val length: Int) {
+class LexerPosition(val line: Int, var column: Int, var length: Int) {
     // Do nothing
 }

src/lexer/TokenType.kt

@@ -1,6 +1,8 @@
 package lexer
 
 enum class TokenType {
+    ALPHANUMERIC,
+
     DOT,
 
     EOF

tests/lexer/LexerScanTest.kt

@@ -9,15 +9,15 @@ import kotlin.test.assertEquals
 
 class LexerScanTest {
     @Test
-    fun scan_emptyString_returnsEOF() {
+    fun scan_emptyString_returns_EOF() {
         val lexer = Lexer("")
         val tokens = lexer.scan()
-        assertEquals(1, tokens.size)
-        assertEquals(TokenType.EOF, tokens[0].type)
+        assertEquals(1, tokens.size, "Expected 1 token, got ${tokens.size}")
+        assertEquals(TokenType.EOF, tokens[0].type, "Expected EOF token, got ${tokens[0].type}")
     }
 
     @Test
-    fun scan_unknownSymbol_returnsError() {
+    fun scan_unknownSymbol_returns_Error() {
         val lexer = Lexer("€")
         assertThrows<Error>({
             val tokens = lexer.scan()
@@ -25,11 +25,47 @@ class LexerScanTest {
     }
 
     @Test
-    fun scan_dot_returnsDot() {
+    fun scan_dot_returns_Dot() {
         val lexer = Lexer(".")
         val tokens = lexer.scan()
         assertEquals(2, tokens.size)
         assertEquals(TokenType.DOT, tokens[0].type, "Expected DOT token, got ${tokens[0].type}")
         assertEquals(TokenType.EOF, tokens[1].type, "Expected EOF token, got ${tokens[1].type}")
     }
+
+    @Test
+    fun scan_two_dots_returns_two_dots() {
+        val lexer = Lexer("..")
+        val tokens = lexer.scan()
+        assertEquals(3, tokens.size)
+        assertEquals(TokenType.DOT, tokens[0].type, "Expected DOT token, got ${tokens[0].type}")
+        assertEquals(TokenType.DOT, tokens[1].type, "Expected DOT token, got ${tokens[1].type}")
+        assertEquals(TokenType.EOF, tokens[2].type, "Expected EOF token, got ${tokens[2].type}")
+    }
+    
+    @Test
+    fun scan_letter_returns_letter() {
+        val lexer = Lexer("a")
+        val tokens = lexer.scan()
+
+        assertEquals(2, tokens.size)
+
+        assertEquals(TokenType.ALPHANUMERIC, tokens[0].type, "Expected ALPHANUMERIC token, got ${tokens[0].type}")
+        assertEquals(TokenType.EOF, tokens[1].type, "Expected EOF token, got ${tokens[1].type}")
+
+        assertEquals(1, tokens[0].position.length, "Expected length 1, got ${tokens[0].position.length}")
+    }
+
+    @Test
+    fun scan_word_returns_alphanumerics() {
+        val lexer = Lexer("word")
+        val tokens = lexer.scan()
+
+        assertEquals(2, tokens.size)
+
+        assertEquals(TokenType.ALPHANUMERIC, tokens[0].type, "Expected ALPHANUMERIC token, got ${tokens[0].type}")
+        assertEquals(TokenType.EOF, tokens[1].type, "Expected EOF token, got ${tokens[1].type}")
+
+        assertEquals(4, tokens[0].position.length, "Expected length 4, got ${tokens[0].position.length}")
+    }
 }