Day 2: Sum calculation in program

src/main/kotlin/day2/Day2.kt

@@ -4,13 +4,29 @@ import java.io.File
 
 object Day2 {
 
-    fun readGames(file: File = File("src/main/resources/day2/input.txt")): List<Game> = file
+    fun sumOfCompatibleGames(hand: Hand) = readGames()
+        .filter { it.isCompatibleWith(hand) }
+        .map(Game::id)
+        .sum()
+
+    private fun readGames(): List<Game> =
+        File("src/main/resources/day2/input.txt")
             .readLines()
             .map(Game.Companion::parse)
 
 }
 
 data class Game(val id: Int, val hands: List<Hand>) {
+    fun isCompatibleWith(hand: Hand) =
+        hand.fitsIn(
+            hands.fold(Hand(0, 0, 0)) { currentMax: Hand, next: Hand ->
+                Hand(
+                    maxOf(currentMax.red, next.red),
+                    maxOf(currentMax.green, next.green),
+                    maxOf(currentMax.blue, next.blue)
+                )
+            })
+
     companion object {
 
         /**
@@ -30,6 +46,8 @@ data class Game(val id: Int, val hands: List<Hand>) {
 }
 
 data class Hand(val red: Int, val green: Int, val blue: Int) {
+    fun fitsIn(other: Hand) = red >= other.red && green >= other.green && blue >= other.blue
+
     companion object {
 
         /**

src/test/kotlin/day2/Day2Test.kt

@@ -6,6 +6,6 @@ class Day2Test {
 
     @Test
     fun readGames() {
-        Day2.readGames()
+        assert(Day2.sumOfCompatibleGames(Hand(12, 13, 14)) == 8)
     }
 }