proc-gen equipment drops from monsters can be picked up

[sketchy-heroes.git] / src / lib / weighted.ts

diff --git a/src/lib/weighted.ts b/src/lib/weighted.ts
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+++ b/src/lib/weighted.ts
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+// given an array, will grab a weighted version of it
+import { random } from 'lodash';
+import { logger } from './logger';
+
+export type Weighted = {
+  weight: number;
+}
+
+export function weighted<T>(options: T[], getWeight: (item: T) => number, weightPrecision: number = 100, defaultReturn?: T): T | undefined {
+  let maxWeight = 0;
+  let segments: {start: number, end: number, item: T}[] = [];
+
+  options.forEach(option => {
+    const start = maxWeight;
+    maxWeight += (getWeight(option) * weightPrecision)
+    const end = maxWeight;
+    segments.push({
+      start: start,
+      end: end,
+      item: option
+    });
+  });
+
+  const selection = random(0, 100);
+
+  logger.info({
+    random: selection,
+    maxWeight: maxWeight
+  }, 'random weighted selection for item');
+
+  if(selection >= maxWeight) {
+    // there's a chance that the player actually gest nothing!
+    return undefined;
+  }
+
+  const found = segments.find(segment => {
+    return segment.start <= selection && segment.end >= selection;
+  });
+
+  return found ? found.item : defaultReturn;
+}