feat: add limit size to download flow

web/src/lib/core/compress.test.ts

@@ -1,5 +1,9 @@
 import { describe, expect, it } from "vitest";
-import { COMPRESSION_LEVELS, findMaxColorsWithin } from "./compress";
+import {
+	COMPRESSION_LEVELS,
+	findMaxColorsWithin,
+	findQualityWithin,
+} from "./compress";
 
 describe("COMPRESSION_LEVELS", () => {
 	it("presets ordered by descending colors", () => {
@@ -38,3 +42,38 @@ describe("findMaxColorsWithin", () => {
 		expect(calls).toBeLessThanOrEqual(12); // log2(254)+probe(2)
 	});
 });
+
+describe("findQualityWithin", () => {
+	const sizeOf = (q: number) => 500 + q * 50; // size grows with quality
+
+	it("picks max quality fitting the target", async () => {
+		// target 5000 -> q<=90 fits
+		const q = await findQualityWithin(5000, async (qq) => sizeOf(qq));
+		expect(q).toBe(90);
+		expect(sizeOf(q)).toBeLessThanOrEqual(5000);
+	});
+
+	it("everything fits - returns max quality", async () => {
+		const q = await findQualityWithin(999999, async (qq) => sizeOf(qq));
+		expect(q).toBe(100);
+	});
+
+	it("target unreachable even at minimum - returns min", async () => {
+		const q = await findQualityWithin(10, async (qq) => sizeOf(qq));
+		expect(q).toBe(1);
+	});
+
+	it("encodeSize null treated as failure", async () => {
+		const q = await findQualityWithin(999999, async () => null);
+		expect(q).toBe(1);
+	});
+
+	it("binary search converges faster than full scan", async () => {
+		let calls = 0;
+		await findQualityWithin(3000, async (qq) => {
+			calls++;
+			return sizeOf(qq);
+		});
+		expect(calls).toBeLessThanOrEqual(10); // log2(99)+2 probes
+	});
+});