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fix: guard division-by-zero in WinCheck when all tiles have fallout #3882

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fix: guard division-by-zero in WinCheck when all tiles have fallout #3882

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14 changes: 12 additions & 2 deletions src/core/execution/WinCheckExecution.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -68,6 +68,11 @@ export class WinCheckExecution implements Execution {
(this.mg.ticks() - this.mg.config().numSpawnPhaseTurns()) / 10;
const numTilesWithoutFallout =
this.mg.numLandTiles() - this.mg.numTilesWithFallout();
Comment on lines 69 to 70
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@evanpelle evanpelle May 8, 2026

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why nut just do:

if numTilesWithoutFallout === this.mg.numLandTiles() {
return
}


if (numTilesWithoutFallout === 0) {
return;
}
Comment on lines +72 to +74
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@coderabbitai coderabbitai Bot May 8, 2026

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⚠️ Potential issue | 🟠 Major | ⚡ Quick win

Timer-based win conditions are suppressed when all tiles have fallout.

The early return before the combined if block bypasses all three win conditions — tile-percentage, maxTimerValue countdown, and HARD_TIME_LIMIT_SECONDS. The timer conditions have nothing to do with numTilesWithoutFallout, so a game where all tiles have fallout when the timer expires (or the hard limit fires) will never declare a winner. The server's hard kill then ends the game without a graceful winner, which defeats the purpose of HARD_TIME_LIMIT_SECONDS.

The guard should wrap only the tile-percentage term:

-    if (numTilesWithoutFallout === 0) {
-      return;
-    }
-
     if (
-      (max.numTilesOwned() / numTilesWithoutFallout) * 100 >
-        this.mg.config().percentageTilesOwnedToWin() ||
+      (numTilesWithoutFallout > 0 &&
+        (max.numTilesOwned() / numTilesWithoutFallout) * 100 >
+          this.mg.config().percentageTilesOwnedToWin()) ||
       (this.mg.config().gameConfig().maxTimerValue !== undefined &&
         timeElapsed - this.mg.config().gameConfig().maxTimerValue! * 60 >= 0) ||
       timeElapsed >= WinCheckExecution.HARD_TIME_LIMIT_SECONDS

Apply the same pattern in checkWinnerTeam (lines 113-115 and 117-119).

Also applies to: 113-115

🤖 Prompt for AI Agents 
Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

In `@src/core/execution/WinCheckExecution.ts` around lines 72 - 74, In
WinCheckExecution.ts adjust the guard so timer-based win conditions still run
when all tiles have fallout: in the win-checking logic (functions checkWinner
and checkWinnerTeam) remove the early "if (numTilesWithoutFallout === 0)
return;" that short-circuits the whole combined if, and instead apply the
numTilesWithoutFallout === 0 check only to the tile-percentage term inside the
combined if (i.e., wrap the tile-percentage comparison with "&&
numTilesWithoutFallout > 0" or equivalent). Keep the other terms (maxTimerValue
countdown and HARD_TIME_LIMIT_SECONDS) evaluated normally so timer expiries can
still declare a winner.


if (
(max.numTilesOwned() / numTilesWithoutFallout) * 100 >
this.mg.config().percentageTilesOwnedToWin() ||
Expand Down Expand Up @@ -104,9 +109,14 @@ export class WinCheckExecution implements Execution {
(this.mg.ticks() - this.mg.config().numSpawnPhaseTurns()) / 10;
const numTilesWithoutFallout =
this.mg.numLandTiles() - this.mg.numTilesWithFallout();
const percentage = (max[1] / numTilesWithoutFallout) * 100;

if (numTilesWithoutFallout === 0) {
return;
}

if (
percentage > this.mg.config().percentageTilesOwnedToWin() ||
(max[1] / numTilesWithoutFallout) * 100 >
this.mg.config().percentageTilesOwnedToWin() ||
Comment on lines +118 to +119
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@coderabbitai coderabbitai Bot May 8, 2026

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⚠️ Potential issue | 🟠 Major | ⚡ Quick win

Floating-point division on a changed line violates the src/core/ determinism guideline.

Line 118 still computes (max[1] / numTilesWithoutFallout) * 100, which is floating-point division. The PR description said this would be replaced with integer cross-multiplication, but it was not. The coding guideline for src/core/ requires avoiding floating-point math to keep simulation deterministic.

Replace with an integer comparison (no division, no floats):

-      (max[1] / numTilesWithoutFallout) * 100 >
-        this.mg.config().percentageTilesOwnedToWin() ||
+      max[1] * 100 >
+        this.mg.config().percentageTilesOwnedToWin() * numTilesWithoutFallout ||

As per coding guidelines: "Ensure deterministic behavior in src/core/ by using seeded PRNG and avoiding floating-point math."

📝 Committable suggestion

‼️ IMPORTANT
Carefully review the code before committing. Ensure that it accurately replaces the highlighted code, contains no missing lines, and has no issues with indentation. Thoroughly test & benchmark the code to ensure it meets the requirements.

Suggested change
(max[1] / numTilesWithoutFallout) * 100 >
this.mg.config().percentageTilesOwnedToWin() ||
max[1] * 100 >
this.mg.config().percentageTilesOwnedToWin() * numTilesWithoutFallout ||
🤖 Prompt for AI Agents 
Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

In `@src/core/execution/WinCheckExecution.ts` around lines 118 - 119, The
comparison uses floating-point division in WinCheckExecution (the expression
"(max[1] / numTilesWithoutFallout) * 100") which violates src/core/ determinism
rules; replace it with an integer cross-multiplication to avoid floats: compare
max[1] * 100 against this.mg.config().percentageTilesOwnedToWin() *
numTilesWithoutFallout (using the same identifiers max, numTilesWithoutFallout
and this.mg.config().percentageTilesOwnedToWin()) so the logic is identical but
uses only integer arithmetic.

(this.mg.config().gameConfig().maxTimerValue !== undefined &&
timeElapsed - this.mg.config().gameConfig().maxTimerValue! * 60 >= 0) ||
timeElapsed >= WinCheckExecution.HARD_TIME_LIMIT_SECONDS
Expand Down
47 changes: 47 additions & 0 deletions tests/core/executions/WinCheckExecution.test.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -87,6 +87,53 @@ describe("WinCheckExecution", () => {
it("should return false for activeDuringSpawnPhase", () => {
expect(winCheck.activeDuringSpawnPhase()).toBe(false);
});

it("should not set winner via tile percentage when all land tiles have fallout (FFA)", () => {
const player = {
numTilesOwned: vi.fn(() => 100),
name: vi.fn(() => "P1"),
};
mg.players = vi.fn(() => [player]);
mg.numLandTiles = vi.fn(() => 100);
mg.numTilesWithFallout = vi.fn(() => 100);
mg.config = vi.fn(() => ({
gameConfig: vi.fn(() => ({
gameMode: GameMode.FFA,
maxTimerValue: undefined,
})),
percentageTilesOwnedToWin: vi.fn(() => 80),
numSpawnPhaseTurns: vi.fn(() => 0),
}));
mg.ticks = vi.fn(() => 0);
mg.stats = vi.fn(() => ({ stats: () => ({}) }));
winCheck.init(mg, 0);
winCheck.checkWinnerFFA();
expect(mg.setWinner).not.toHaveBeenCalled();
});

it("should not set winner via tile percentage when all land tiles have fallout (Team)", () => {
const player = {
numTilesOwned: vi.fn(() => 100),
name: vi.fn(() => "P1"),
team: vi.fn(() => "Red"),
};
mg.players = vi.fn(() => [player]);
mg.numLandTiles = vi.fn(() => 100);
mg.numTilesWithFallout = vi.fn(() => 100);
mg.config = vi.fn(() => ({
gameConfig: vi.fn(() => ({
gameMode: GameMode.Team,
maxTimerValue: undefined,
})),
percentageTilesOwnedToWin: vi.fn(() => 80),
numSpawnPhaseTurns: vi.fn(() => 0),
}));
mg.ticks = vi.fn(() => 0);
mg.stats = vi.fn(() => ({ stats: () => ({}) }));
winCheck.init(mg, 0);
winCheck.checkWinnerTeam();
expect(mg.setWinner).not.toHaveBeenCalled();
});
});

describe("WinCheckExecution - Nation Winners", () => {
Expand Down
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