Adds a best train route finder function

[gvalfonso]

Description:

There was a dev note that said that train routes could be improved by picking a lucrative route. The update adds a function for that purpose. There were no changes to the balancing of trains. I did not replace the current random station picker.

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• I have added screenshots for all UI updates
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• I have added relevant tests to the test directory
• I confirm I have thoroughly tested these changes and take full responsibility for any bugs introduced

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tribesdev

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[coderabbitai]

Walkthrough

Adds two private helpers to TrainStationExecution for destination selection and profit calculation; updates a comment. Current spawn flow still uses random destination selection. No exported APIs changed.

Changes

Cohort / File(s)	Summary of Changes
Train station execution helpers src/core/execution/TrainStationExecution.ts	- Added private selectBestDestination(source, available) - Added private calculateProfit(source, destination) - Left existing random selection logic in place (helpers not yet invoked) - Tweaked inline comment about future destination selection path

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

Poem

Rails hum soft with unspent might,
New maps drawn in profit’s light.
Helpers wait, patient and keen,
Counting gold along the green.
For now, chance rolls the station’s die—
Soon, the richest route will fly.

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[coderabbitai]

Actionable comments posted: 0

🧹 Nitpick comments (7)

src/core/execution/TrainStationExecution.ts (7)

80-84: Avoid selecting the source station; prevent wasted ticks when randomizing

Today the random pick can choose the same station, which then aborts the spawn and wastes the tick. Filter the current station out before picking. Keeps behavior “random” as per PR scope while removing the no-op.

-    // Can use the selectBestDestination function for best destination.
-    const destination: TrainStation =
-      this.random.randFromSet(availableForTrade);
+    // Prefer not selecting self to avoid wasting a tick on a no-op spawn.
+    const candidates = new Set([...availableForTrade].filter((s) => s !== station));
+    if (candidates.size === 0) return;
+    const destination: TrainStation = this.random.randFromSet(candidates);

---

99-114: Safer fallback: do not allow the helper to return the source station

If all profits are 0n, bestStation stays null and the fallback can pick source. Tighten the fallback to exclude source. This makes the helper safe in isolation and future-proof if it gets used elsewhere.

-    return bestStation ?? this.random.randFromSet(available);
+    const pool = new Set([...available].filter((s) => s !== source));
+    return bestStation ?? (pool.size ? this.random.randFromSet(pool) : source);

---

116-130: Do not count the source station in “profit”

Counting the origin inflates the score by one stop. Usually “profit along the route” means from the first hop after source to the destination. Skip index 0.

-    let totalProfit = 0n;
-    for (const station of route) {
-      const stationOwner = station.unit.owner();
-      const isFriendly = sourceOwner.isFriendly(stationOwner);
-      totalProfit += this.mg.config().trainGold(isFriendly);
-    }
+    let totalProfit = 0n;
+    // Skip the source station to avoid counting it toward profit.
+    for (let i = 1; i < route.length; i++) {
+      const station = route[i];
+      const stationOwner = station.unit.owner();
+      const isFriendly = sourceOwner.isFriendly(stationOwner);
+      totalProfit += this.mg.config().trainGold(isFriendly);
+    }

Please confirm intended semantics: should we also exclude the final station, or include it? If you want “per-hop” profit, a per-edge accumulation may be clearer.

---

99-130: Tie-breaking on equal profits: pick randomly among the best

Current code picks the first max. For fair distribution, prefer random among top scorers. Simple and keeps behavior stable.

-  private selectBestDestination(source: TrainStation, available: Set<TrainStation>): TrainStation {
-    let bestStation: TrainStation | null = null;
-    let bestProfit = 0n;
-
-    for (const station of available) {
-      if (station === source) continue;
-
-      const profit = this.calculateProfit(source, station);
-      if (profit > bestProfit) {
-        bestProfit = profit;
-        bestStation = station;
-      }
-    }
-
-    return bestStation ?? this.random.randFromSet(available);
-  }
+  private selectBestDestination(source: TrainStation, available: Set<TrainStation>): TrainStation {
+    let bestProfit = -1n;
+    const best: TrainStation[] = [];
+
+    for (const station of available) {
+      if (station === source) continue;
+      const profit = this.calculateProfit(source, station);
+      if (profit > bestProfit) {
+        bestProfit = profit;
+        best.length = 0;
+        best.push(station);
+      } else if (profit === bestProfit) {
+        best.push(station);
+      }
+    }
+
+    if (best.length > 0) return this.random.randFromSet(new Set(best));
+    const pool = new Set([...available].filter((s) => s !== source));
+    return pool.size ? this.random.randFromSet(pool) : source;
+  }

---

80-84: Optional: feature-flag the “best destination” without changing current balance

You can keep default behavior “random” and allow turning on the best-route selector later. This aligns with the PR note about not replacing the random picker yet.

-    // Prefer not selecting self to avoid wasting a tick on a no-op spawn.
-    const candidates = new Set([...availableForTrade].filter((s) => s !== station));
-    if (candidates.size === 0) return;
-    const destination: TrainStation = this.random.randFromSet(candidates);
+    const candidates = new Set([...availableForTrade].filter((s) => s !== station));
+    if (candidates.size === 0) return;
+    const destination: TrainStation =
+      (this.mg.config().useBestTrainRoute?.() === true)
+        ? this.selectBestDestination(station, candidates)
+        : this.random.randFromSet(candidates);

If you want, I can follow up with a small PR to add useBestTrainRoute() to config with a typed union for strategy: "random" | "best".

---

116-130: Scoring model favors very long routes; consider normalizing by travel time

Summing per-station gold makes long paths always win (even through enemy territory if per-stop gold is positive). If desired, normalize by hops or apply a cap to avoid “always go far” behavior.

Possible tweaks (choose any):

• Divide by route length to compute average gain per hop.
• Subtract a per-hop cost.
• Cap max considered hops.
• Weight friendly/hostile differently, e.g., hostile reduces score.

---

99-130: Add unit tests for the new helpers

Targeted tests will keep future refactors safe.

Suggested cases:

• No route between source and destination → 0n.
• Single-edge route with friendly destination only.
• Mixed friendly/hostile stations on the path.
• All candidates yield 0n profit → fallback excludes source.
• Tie on profit across multiple destinations → randomized pick among ties (if you adopt tie-breaking).
• BigInt boundaries: very long route accumulations.
  Want me to scaffold these tests?

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📥 Commits

Reviewing files that changed from the base of the PR and between add81b9 and 1dcc8aa.

📒 Files selected for processing (1)

• src/core/execution/TrainStationExecution.ts (2 hunks)

🧰 Additional context used

🧬 Code graph analysis (1)

src/core/execution/TrainStationExecution.ts (2)

src/core/game/TrainStation.ts (2)

• TrainStation (87-170)
• availableForTrade (226-234)

src/core/game/PlayerImpl.ts (1)

• isFriendly (754-756)

🔇 Additional comments (1)

src/core/execution/TrainStationExecution.ts (1)

116-130: No BigInt Coercion Needed
config().trainGold(isFriendly) already returns Gold, which is aliased to bigint in Game.ts. The current totalProfit += this.mg.config().trainGold(isFriendly) is type-safe and needs no change.

The merge-base changed after approval.