ui-svelte: fix histogram calculation (#695)

- Fix the histogram calculation to use server provided generation
tokens/second.
- Move histogram to Activities page where it can exist with the rest of
the token metrics

Fixes #681

ui-svelte/src/lib/histogram.test.ts

@@ -0,0 +1,163 @@
+import { describe, it, expect } from "vitest";
+import { calculateHistogramData } from "./histogram";
+
+describe("calculateHistogramData", () => {
+  describe("edge cases", () => {
+    it("returns null for empty input", () => {
+      expect(calculateHistogramData([])).toBeNull();
+    });
+
+    it("handles single value", () => {
+      const result = calculateHistogramData([42]);
+      expect(result).not.toBeNull();
+      expect(result!.bins).toEqual([1]);
+      expect(result!.min).toBe(42);
+      expect(result!.max).toBe(42);
+      expect(result!.binSize).toBe(0);
+      expect(result!.p50).toBe(42);
+      expect(result!.p95).toBe(42);
+      expect(result!.p99).toBe(42);
+    });
+
+    it("handles all identical values", () => {
+      const result = calculateHistogramData([10, 10, 10, 10, 10]);
+      expect(result).not.toBeNull();
+      expect(result!.bins).toEqual([5]);
+      expect(result!.min).toBe(10);
+      expect(result!.max).toBe(10);
+      expect(result!.binSize).toBe(0);
+    });
+
+    it("handles two distinct values", () => {
+      const result = calculateHistogramData([10, 20]);
+      expect(result).not.toBeNull();
+      expect(result!.min).toBe(10);
+      expect(result!.max).toBe(20);
+      expect(result!.p50).toBe(15);
+      const binSum = result!.bins.reduce((s, b) => s + b, 0);
+      expect(binSum).toBe(2);
+    });
+  });
+
+  describe("bin distribution", () => {
+    it("bins sum to total number of values", () => {
+      const values = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10];
+      const result = calculateHistogramData(values);
+      expect(result).not.toBeNull();
+      const binSum = result!.bins.reduce((s, b) => s + b, 0);
+      expect(binSum).toBe(values.length);
+    });
+
+    it("distributes uniform values across bins", () => {
+      const values = Array.from({ length: 100 }, (_, i) => i);
+      const result = calculateHistogramData(values);
+      expect(result).not.toBeNull();
+      expect(result!.bins.length).toBe(20);
+      const binSum = result!.bins.reduce((s, b) => s + b, 0);
+      expect(binSum).toBe(100);
+    });
+
+    it("places values in correct bins", () => {
+      const values = [1, 1, 1, 5, 5, 9, 9, 9];
+      const result = calculateHistogramData(values, { minBins: 3, maxBins: 3, binScaling: 1 });
+      expect(result).not.toBeNull();
+      expect(result!.bins.length).toBe(3);
+      expect(result!.bins.reduce((s, b) => s + b, 0)).toBe(8);
+    });
+
+    it("handles skewed distribution", () => {
+      const values = [1, 1, 1, 1, 1, 100];
+      const result = calculateHistogramData(values);
+      expect(result).not.toBeNull();
+      const binSum = result!.bins.reduce((s, b) => s + b, 0);
+      expect(binSum).toBe(6);
+    });
+  });
+
+  describe("percentiles", () => {
+    it("calculates correct p50 for even-length array", () => {
+      const values = [1, 2, 3, 4];
+      const result = calculateHistogramData(values);
+      expect(result).not.toBeNull();
+      expect(result!.p50).toBe(2.5);
+    });
+
+    it("calculates correct p50 for odd-length array", () => {
+      const values = [1, 2, 3, 4, 5];
+      const result = calculateHistogramData(values);
+      expect(result).not.toBeNull();
+      expect(result!.p50).toBe(3);
+    });
+
+    it("calculates p99 with interpolation", () => {
+      const values = Array.from({ length: 100 }, (_, i) => i + 1);
+      const result = calculateHistogramData(values);
+      expect(result).not.toBeNull();
+      expect(result!.p99).toBeCloseTo(99.01);
+    });
+
+    it("calculates p95 with interpolation", () => {
+      const values = Array.from({ length: 100 }, (_, i) => i + 1);
+      const result = calculateHistogramData(values);
+      expect(result).not.toBeNull();
+      expect(result!.p95).toBeCloseTo(95.05);
+    });
+
+    it("percentiles are monotonically increasing", () => {
+      const values = Array.from({ length: 200 }, () => Math.random() * 100);
+      const result = calculateHistogramData(values);
+      expect(result).not.toBeNull();
+      expect(result!.p50).toBeLessThanOrEqual(result!.p95);
+      expect(result!.p95).toBeLessThanOrEqual(result!.p99);
+    });
+  });
+
+  describe("bin count adaptation", () => {
+    it("uses minimum bins for small datasets", () => {
+      const values = Array.from({ length: 20 }, (_, i) => i);
+      const result = calculateHistogramData(values);
+      expect(result!.bins.length).toBe(10);
+    });
+
+    it("scales bins with dataset size", () => {
+      const values = Array.from({ length: 100 }, (_, i) => i);
+      const result = calculateHistogramData(values);
+      expect(result!.bins.length).toBe(20);
+    });
+
+    it("caps bins at maximum", () => {
+      const values = Array.from({ length: 200 }, (_, i) => i);
+      const result = calculateHistogramData(values);
+      expect(result!.bins.length).toBe(30);
+    });
+
+    it("respects custom options", () => {
+      const values = Array.from({ length: 100 }, (_, i) => i);
+      const result = calculateHistogramData(values, { minBins: 5, maxBins: 10, binScaling: 2 });
+      expect(result!.bins.length).toBe(10);
+    });
+  });
+
+  describe("min and max", () => {
+    it("correctly identifies min and max", () => {
+      const values = [5, 3, 8, 1, 9, 2];
+      const result = calculateHistogramData(values);
+      expect(result!.min).toBe(1);
+      expect(result!.max).toBe(9);
+    });
+
+    it("handles negative values", () => {
+      const values = [-10, -5, 0, 5, 10];
+      const result = calculateHistogramData(values);
+      expect(result!.min).toBe(-10);
+      expect(result!.max).toBe(10);
+    });
+
+    it("handles floating point values", () => {
+      const values = [1.5, 2.7, 3.14, 0.5, 4.99];
+      const result = calculateHistogramData(values);
+      expect(result!.min).toBe(0.5);
+      expect(result!.max).toBe(4.99);
+    });
+  });
+});