feat(code-editor): add collapse unchanged lines extension with expand…

apps/code/src/renderer/features/code-editor/hooks/collapseUnchangedExtension.test.ts

@@ -0,0 +1,166 @@
+import { EditorState } from "@codemirror/state";
+import { describe, expect, it } from "vitest";
+import {
+  applyExpandEffect,
+  buildDecorations,
+  type CollapsedRange,
+  expandAll,
+  expandDown,
+  expandUp,
+  mapPosBetweenSides,
+} from "./collapseUnchangedExtension";
+
+function makeState(lineCount: number): EditorState {
+  const lines = Array.from({ length: lineCount }, (_, i) => `line ${i + 1}`);
+  return EditorState.create({ doc: lines.join("\n") });
+}
+
+function range(
+  from: number,
+  to: number,
+  limitFrom?: number,
+  limitTo?: number,
+): CollapsedRange {
+  return {
+    fromLine: from,
+    toLine: to,
+    limitFromLine: limitFrom ?? from,
+    limitToLine: limitTo ?? to,
+  };
+}
+
+describe("mapPosBetweenSides", () => {
+  const chunks = [
+    { fromA: 10, toA: 20, fromB: 10, toB: 25 },
+    { fromA: 50, toA: 60, fromB: 55, toB: 70 },
+  ];
+
+  it("maps position before first chunk", () => {
+    expect(mapPosBetweenSides(5, chunks, true)).toBe(5);
+    expect(mapPosBetweenSides(5, chunks, false)).toBe(5);
+  });
+
+  it("maps position between chunks from side A", () => {
+    expect(mapPosBetweenSides(30, chunks, true)).toBe(35);
+  });
+
+  it("maps position between chunks from side B", () => {
+    expect(mapPosBetweenSides(35, chunks, false)).toBe(30);
+  });
+
+  it("maps position after last chunk from side A", () => {
+    expect(mapPosBetweenSides(80, chunks, true)).toBe(90);
+  });
+
+  it("handles empty chunks array", () => {
+    expect(mapPosBetweenSides(42, [], true)).toBe(42);
+    expect(mapPosBetweenSides(42, [], false)).toBe(42);
+  });
+
+  it("maps position at exact chunk boundary", () => {
+    expect(mapPosBetweenSides(10, chunks, true)).toBe(10);
+  });
+});
+
+describe("applyExpandEffect", () => {
+  const state = makeState(20);
+
+  const ranges: CollapsedRange[] = [range(1, 5), range(12, 18)];
+
+  it("expandAll removes the targeted range", () => {
+    const pos = state.doc.line(3).from;
+    const effect = expandAll.of(pos);
+    const result = applyExpandEffect(ranges, state, effect);
+
+    expect(result).toEqual([range(12, 18)]);
+  });
+
+  it("expandAll leaves non-targeted ranges intact", () => {
+    const pos = state.doc.line(8).from;
+    const effect = expandAll.of(pos);
+    const result = applyExpandEffect(ranges, state, effect);
+
+    expect(result).toEqual(ranges);
+  });
+
+  it("expandUp reveals lines above the collapsed range", () => {
+    const pos = state.doc.line(14).from;
+    const effect = expandUp.of({ pos, lines: 3 });
+    const result = applyExpandEffect(ranges, state, effect);
+
+    expect(result).toEqual([range(1, 5), range(15, 18, 12, 18)]);
+  });
+
+  it("expandDown reveals lines below the collapsed range", () => {
+    const pos = state.doc.line(14).from;
+    const effect = expandDown.of({ pos, lines: 3 });
+    const result = applyExpandEffect(ranges, state, effect);
+
+    expect(result).toEqual([range(1, 5), range(12, 15, 12, 18)]);
+  });
+
+  it("expandUp removes range when lines exceed range size", () => {
+    const pos = state.doc.line(3).from;
+    const effect = expandUp.of({ pos, lines: 100 });
+    const result = applyExpandEffect(ranges, state, effect);
+
+    expect(result).toEqual([range(12, 18)]);
+  });
+
+  it("expandDown removes range when lines exceed range size", () => {
+    const pos = state.doc.line(3).from;
+    const effect = expandDown.of({ pos, lines: 100 });
+    const result = applyExpandEffect(ranges, state, effect);
+
+    expect(result).toEqual([range(12, 18)]);
+  });
+
+  it("preserves original boundaries through multiple expansions", () => {
+    const pos = state.doc.line(14).from;
+    const first = applyExpandEffect(
+      ranges,
+      state,
+      expandUp.of({ pos, lines: 2 }),
+    );
+    const second = applyExpandEffect(
+      first,
+      state,
+      expandDown.of({ pos: state.doc.line(16).from, lines: 2 }),
+    );
+
+    expect(second).toEqual([range(1, 5), range(14, 16, 12, 18)]);
+  });
+});
+
+describe("buildDecorations", () => {
+  it("skips ranges where fromLine > toLine", () => {
+    const state = makeState(10);
+    const ranges: CollapsedRange[] = [range(5, 3)];
+    const deco = buildDecorations(state, ranges);
+
+    expect(deco.size).toBe(0);
+  });
+
+  it("creates decorations for valid ranges", () => {
+    const state = makeState(20);
+    const ranges: CollapsedRange[] = [range(3, 7), range(15, 18)];
+    const deco = buildDecorations(state, ranges);
+
+    expect(deco.size).toBe(2);
+  });
+
+  it("handles empty ranges array", () => {
+    const state = makeState(10);
+    const deco = buildDecorations(state, []);
+
+    expect(deco.size).toBe(0);
+  });
+
+  it("creates single-line range decoration", () => {
+    const state = makeState(10);
+    const ranges: CollapsedRange[] = [range(5, 5)];
+    const deco = buildDecorations(state, ranges);
+
+    expect(deco.size).toBe(1);
+  });
+});