Add comparison generation logic with tests

Co-authored-by: oBusk <13413409+oBusk@users.noreply.github.com>

Author: Copilot

src/lib/utils/generateComparisons.test.ts

@@ -0,0 +1,205 @@
+import { generateComparisons } from "./generateComparisons";
+
+describe("generateComparisons", () => {
+    it("returns empty array for package with 0 versions", () => {
+        const result = generateComparisons([], {});
+        expect(result).toEqual([]);
+    });
+
+    it("returns empty array for package with 1 version", () => {
+        const versions = ["1.0.0"];
+        const versionMap = { "1.0.0": { time: "2020-01-01" } };
+        const result = generateComparisons(versions, versionMap);
+        expect(result).toEqual([]);
+    });
+
+    it("generates exactly 10 comparisons for a package with many versions", () => {
+        const versions = [
+            "1.0.0",
+            "1.0.1",
+            "1.1.0",
+            "1.1.1",
+            "2.0.0",
+            "2.0.1",
+            "2.1.0",
+            "2.1.1",
+            "3.0.0",
+            "3.0.1",
+            "3.1.0",
+            "3.1.1",
+            "3.1.2",
+            "3.1.3",
+            "3.1.4",
+            "3.1.5",
+        ];
+        const versionMap: Record<string, { time: string }> = {};
+        versions.forEach((v, i) => {
+            versionMap[v] = { time: `2020-01-${String(i + 1).padStart(2, "0")}` };
+        });
+
+        const result = generateComparisons(versions, versionMap);
+        expect(result).toHaveLength(10);
+    });
+
+    it("identifies major bumps correctly", () => {
+        const versions = [
+            "1.0.0",
+            "1.9.4",
+            "2.0.0",
+            "2.5.0",
+            "3.0.0",
+            "3.1.0",
+        ];
+        const versionMap: Record<string, { time: string }> = {
+            "1.0.0": { time: "2020-01-01" },
+            "1.9.4": { time: "2020-06-01" },
+            "2.0.0": { time: "2020-07-01" },
+            "2.5.0": { time: "2020-12-01" },
+            "3.0.0": { time: "2021-01-01" },
+            "3.1.0": { time: "2021-02-01" },
+        };
+
+        const result = generateComparisons(versions, versionMap);
+
+        // Should include major bumps: 3.0.0 vs 2.5.0, 2.0.0 vs 1.9.4
+        const majorBumps = result.filter((c) => c.type === "major");
+        expect(majorBumps.length).toBeGreaterThan(0);
+        expect(majorBumps).toContainEqual({
+            from: "2.5.0",
+            to: "3.0.0",
+            type: "major",
+        });
+        expect(majorBumps).toContainEqual({
+            from: "1.9.4",
+            to: "2.0.0",
+            type: "major",
+        });
+    });
+
+    it("identifies minor bumps correctly", () => {
+        const versions = ["2.0.0", "2.0.12", "2.1.0", "2.1.3", "2.2.0"];
+        const versionMap: Record<string, { time: string }> = {
+            "2.0.0": { time: "2020-01-01" },
+            "2.0.12": { time: "2020-06-01" },
+            "2.1.0": { time: "2020-07-01" },
+            "2.1.3": { time: "2020-12-01" },
+            "2.2.0": { time: "2021-01-01" },
+        };
+
+        const result = generateComparisons(versions, versionMap);
+
+        const minorBumps = result.filter((c) => c.type === "minor");
+        expect(minorBumps.length).toBeGreaterThan(0);
+        expect(minorBumps).toContainEqual({
+            from: "2.1.3",
+            to: "2.2.0",
+            type: "minor",
+        });
+        expect(minorBumps).toContainEqual({
+            from: "2.0.12",
+            to: "2.1.0",
+            type: "minor",
+        });
+    });
+
+    it("identifies patch bumps correctly", () => {
+        const versions = ["2.1.3", "2.1.4", "2.1.5", "2.1.6"];
+        const versionMap: Record<string, { time: string }> = {
+            "2.1.3": { time: "2020-01-01" },
+            "2.1.4": { time: "2020-02-01" },
+            "2.1.5": { time: "2020-03-01" },
+            "2.1.6": { time: "2020-04-01" },
+        };
+
+        const result = generateComparisons(versions, versionMap);
+
+        const patchBumps = result.filter((c) => c.type === "patch");
+        expect(patchBumps.length).toBeGreaterThan(0);
+        expect(patchBumps).toContainEqual({
+            from: "2.1.5",
+            to: "2.1.6",
+            type: "patch",
+        });
+    });
+
+    it("returns fewer than 10 comparisons for packages with few versions", () => {
+        const versions = ["1.0.0", "1.0.1", "1.0.2"];
+        const versionMap: Record<string, { time: string }> = {
+            "1.0.0": { time: "2020-01-01" },
+            "1.0.1": { time: "2020-02-01" },
+            "1.0.2": { time: "2020-03-01" },
+        };
+
+        const result = generateComparisons(versions, versionMap);
+        expect(result.length).toBeLessThanOrEqual(2);
+    });
+
+    it("backfills from majors when not enough minor/patch bumps", () => {
+        const versions = [
+            "1.0.0",
+            "2.0.0",
+            "3.0.0",
+            "4.0.0",
+            "5.0.0",
+            "6.0.0",
+            "7.0.0",
+            "8.0.0",
+            "9.0.0",
+            "10.0.0",
+            "11.0.0",
+        ];
+        const versionMap: Record<string, { time: string }> = {};
+        versions.forEach((v, i) => {
+            versionMap[v] = { time: `2020-${String(i + 1).padStart(2, "0")}-01` };
+        });
+
+        const result = generateComparisons(versions, versionMap);
+
+        // Should have 10 major bumps (since there are no minor/patch bumps)
+        expect(result).toHaveLength(10);
+        const majorBumps = result.filter((c) => c.type === "major");
+        expect(majorBumps.length).toBe(10);
+    });
+
+    it("sorts comparisons by publish date (newest first)", () => {
+        const versions = ["1.0.0", "1.0.1", "2.0.0", "2.0.1"];
+        const versionMap: Record<string, { time: string }> = {
+            "1.0.0": { time: "2020-01-01" },
+            "1.0.1": { time: "2020-02-01" },
+            "2.0.0": { time: "2020-03-01" },
+            "2.0.1": { time: "2020-04-01" },
+        };
+
+        const result = generateComparisons(versions, versionMap);
+
+        // Should be sorted by the "to" version's publish date, newest first
+        for (let i = 0; i < result.length - 1; i++) {
+            const timeA = versionMap[result[i].to].time;
+            const timeB = versionMap[result[i + 1].to].time;
+            expect(timeA >= timeB).toBe(true);
+        }
+    });
+
+    it("handles versions with prerelease tags", () => {
+        const versions = [
+            "1.0.0",
+            "1.0.1",
+            "2.0.0-beta.1",
+            "2.0.0",
+            "2.0.1",
+        ];
+        const versionMap: Record<string, { time: string }> = {};
+        versions.forEach((v, i) => {
+            versionMap[v] = { time: `2020-01-${String(i + 1).padStart(2, "0")}` };
+        });
+
+        const result = generateComparisons(versions, versionMap);
+
+        // Should include all valid semver versions, including prereleases
+        expect(result.length).toBeGreaterThan(0);
+        result.forEach((comparison) => {
+            expect(comparison.from).toBeTruthy();
+            expect(comparison.to).toBeTruthy();
+        });
+    });
+});