Arimaa: Fix traps and minimum requirements in free placement

Author: Perlkonig

locales/en/apgames.json

@@ -3411,6 +3411,7 @@
             "PARTIAL_PLAY": "Continue placing your pieces.",
             "PARTIAL_PUSH": "You must now complete the push.",
             "PARTIAL_FREE": "You may continue placing pieces, or click Complete Move to end your turn.",
+            "PARTIAL_FREE_NO": "You may continue placing pieces, but you must place at least one rabbit, and you may not place any rabbits on the goal row.",
             "REPEAT": "You may not repeat a given position a third time.",
             "TOO_MANY": "You may only take up to {{num}} actions this turn."
         },

src/games/arimaa.ts

@@ -599,10 +599,19 @@ export class ArimaaGame extends GameBase {
             // now we just have to check completeness and return
             let complete: -1|0|1;
             let message: string;
-            // in free mode, always 0 with specific message
+            // in free mode:
+            // - usually 0 with specific message
+            // - but must have 1 rabbit and none on the goal row
             if (this.variants.includes("free")) {
-                complete = 0;
-                message = i18next.t("apgames:validation.arimaa.PARTIAL_FREE")
+                const rabbits = [...cloned.board.entries()].filter(e => e[1][1] === cloned.currplayer && e[1][0] === "R").map(e => e[0]);
+                const goal = cloned.currplayer === 1 ? "8" : "1";
+                if (rabbits.length === 0 || rabbits.filter(cell => cell.endsWith(goal)).length > 0) {
+                    complete = -1;
+                    message = i18next.t("apgames:validation.arimaa.PARTIAL_FREE_NO")
+                } else {
+                    complete = 0;
+                    message = i18next.t("apgames:validation.arimaa.PARTIAL_FREE")
+                }
             }
             // otherwise, you have to place all your pieces
             else {
@@ -906,6 +915,18 @@ export class ArimaaGame extends GameBase {
             this.hands = undefined;
         }
 
+        // After free setup, activate all traps
+        if (this.variants.includes("free") && this.stack.length === 2) {
+            for (const trap of traps) {
+                if (this.board.has(trap) && this.isAlone(trap)) {
+                    const [trapPc, trapOwner] = this.board.get(trap)!;
+                    this.board.delete(trap);
+                    this.results.push({type: "destroy", what: trapOwner === 1 ? trapPc : trapPc.toLowerCase(), where: trap});
+                    lastmove.push(`x${trapOwner === 1 ? trapPc : trapPc.toLowerCase()}${trap}`);
+                }
+            }
+        }
+
         // update currplayer
         this.lastmove = lastmove.join(",");
         let newplayer = (this.currplayer as number) + 1;