Feature improvement: automatic deck submissions now add lands sensibly (#10159)

* Make automatic deck submissions use sensible land suggestions

* Cover edge case of no colored mana symbols among cards in deck

* Add comments

* Get minimum deck size from deck validator

Mage/src/main/java/mage/util/DeckBuildUtils.java

@@ -0,0 +1,59 @@
+package mage.util;
+
+import mage.cards.Card;
+
+import java.util.Set;
+
+public final class DeckBuildUtils {
+
+    public static int[] landCountSuggestion(int deckSize, Set<Card> deckList) {
+        /*
+        Returns the number of basic lands suggested to complete a deck
+        as an array of five ints: plains, islands, swamps, mountains, forests
+        Total number of lands always sufficient to reach deckSize
+         */
+        int plains = 0, islands = 0, swamps = 0, mountains = 0, forests = 0;
+        int landsNeeded = deckSize - deckList.size();
+        if (landsNeeded > 0) {
+            int white = 0, blue = 0, black = 0, red = 0, green = 0;
+            // Rudimentary algorithm that simply counts number of cards with each mana symbol
+            for (Card cd : deckList) {
+                for (String s : cd.getManaCostSymbols()) {
+                    if (s.contains("W")) white++;
+                    if (s.contains("U")) blue++;
+                    if (s.contains("B")) black++;
+                    if (s.contains("R")) red++;
+                    if (s.contains("G")) green++;
+                }
+            }
+            int total = white + blue + black + red + green;
+            // If no colored mana symbols, distribute evenly
+            if (total == 0) {
+                total = 5; white = 1; blue = 1; black = 1; red = 1;
+            }
+
+            plains = Math.round(landsNeeded * ((float) white / (float) total));
+            total -= white;
+            landsNeeded -= plains;
+
+            islands = Math.round(landsNeeded * ((float) blue / (float) total));
+            total -= blue;
+            landsNeeded -= islands;
+
+            swamps = Math.round(landsNeeded * ((float) black / (float) total));
+            total -= black;
+            landsNeeded -= swamps;
+
+            mountains = Math.round(landsNeeded * ((float) red / (float) total));
+            landsNeeded -= mountains;
+
+            forests = landsNeeded;
+        }
+        return new int[] {plains, islands, swamps, mountains, forests};
+    }
+
+    // Hide constructor - not to be instantiated
+    private DeckBuildUtils() {
+    }
+
+}