1 files changed, 180 insertions, 0 deletions
diff --git a/src/features/workspaces/logic/drag-controller.test.ts b/src/features/workspaces/logic/drag-controller.test.ts
new file mode 100644
index 0000000..459063a
--- /dev/null
+++ b/src/features/workspaces/logic/drag-controller.test.ts
@@ -0,0 +1,180 @@
+import { describe, expect, it } from "vitest";
+import { type DragPhase, type DragTransition, nextDragPhase } from "./drag-controller";
+
+const OPTS = { dragThresholdPx: 6 };
+
+function down(over: Partial<Parameters<typeof nextDragPhase>[1] & { type: "pointer-down" }> = {}) {
+  return {
+    type: "pointer-down" as const,
+    id: "t1",
+    x: 10,
+    y: 10,
+    touch: false,
+    ...over,
+  };
+}
+
+function press(touch = false): DragPhase {
+  return nextDragPhase({ kind: "idle" }, down({ touch }), OPTS).phase;
+}
+
+describe("nextDragPhase — mouse", () => {
+  it("a pointer-down enters the undecided pressing state", () => {
+    expect(press()).toEqual({ kind: "pressing", id: "t1", x: 10, y: 10, touch: false });
+  });
+
+  it("movement past the threshold starts a drag", () => {
+    const transition = nextDragPhase(
+      press(),
+      { type: "pointer-move", x: 20, y: 12, targetCell: { col: 4, row: 1 } },
+      OPTS,
+    );
+    expect(transition.phase).toEqual({
+      kind: "dragging",
+      id: "t1",
+      x: 20,
+      y: 12,
+      targetCell: { col: 4, row: 1 },
+      touch: false,
+    });
+    expect(transition.emit).toBeUndefined();
+  });
+
+  it("movement within the threshold stays pressing", () => {
+    const transition = nextDragPhase(
+      press(),
+      { type: "pointer-move", x: 12, y: 14, targetCell: { col: 1, row: 1 } },
+      OPTS,
+    );
+    expect(transition.phase).toEqual({ kind: "pressing", id: "t1", x: 10, y: 10, touch: false });
+  });
+
+  it("release without moving emits a tap (open the workspace)", () => {
+    const transition = nextDragPhase(press(), { type: "pointer-up" }, OPTS);
+    expect(transition.phase).toEqual({ kind: "idle" });
+    expect(transition.emit).toEqual({ kind: "tap", id: "t1" });
+  });
+
+  it("release while dragging emits a drop with the last tracked index", () => {
+    let transition: DragTransition = nextDragPhase(
+      press(),
+      { type: "pointer-move", x: 30, y: 30, targetCell: { col: 3, row: 1 } },
+      OPTS,
+    );
+    transition = nextDragPhase(
+      transition.phase,
+      { type: "pointer-move", x: 31, y: 31, targetCell: { col: 6, row: 1 } },
+      OPTS,
+    );
+    transition = nextDragPhase(transition.phase, { type: "pointer-up" }, OPTS);
+    expect(transition.emit).toEqual({ kind: "drop", id: "t1", targetCell: { col: 6, row: 1 } });
+    expect(transition.phase).toEqual({ kind: "idle" });
+  });
+});
+
+describe("nextDragPhase — touch", () => {
+  it("a long-press lifts the tile and emits lift (arm the drag + select)", () => {
+    const transition = nextDragPhase(press(true), { type: "long-press" }, OPTS);
+    expect(transition.emit).toEqual({ kind: "lift", id: "t1" });
+    expect(transition.phase).toEqual({
+      kind: "dragging",
+      id: "t1",
+      x: 10,
+      y: 10,
+      targetCell: null,
+      touch: true,
+    });
+  });
+
+  it("movement past the threshold BEFORE the lift cancels (vertical scrolling wins)", () => {
+    const transition = nextDragPhase(
+      press(true),
+      { type: "pointer-move", x: 10, y: 80, targetCell: { col: 1, row: 1 } },
+      OPTS,
+    );
+    expect(transition.phase).toEqual({ kind: "idle" });
+    expect(transition.emit).toBeUndefined();
+  });
+
+  it("movement within the threshold before the lift keeps pressing", () => {
+    const transition = nextDragPhase(
+      press(true),
+      { type: "pointer-move", x: 13, y: 12, targetCell: { col: 1, row: 1 } },
+      OPTS,
+    );
+    expect(transition.phase?.kind).toBe("pressing");
+  });
+
+  it("after the lift, movement drags (never cancels)", () => {
+    let transition = nextDragPhase(press(true), { type: "long-press" }, OPTS);
+    transition = nextDragPhase(
+      transition.phase,
+      { type: "pointer-move", x: 10, y: 90, targetCell: { col: 5, row: 1 } },
+      OPTS,
+    );
+    expect(transition.phase).toEqual({
+      kind: "dragging",
+      id: "t1",
+      x: 10,
+      y: 90,
+      targetCell: { col: 5, row: 1 },
+      touch: true,
+    });
+  });
+
+  it("a long-press never lifts a mouse press (desktop selects via right-click)", () => {
+    const transition = nextDragPhase(press(false), { type: "long-press" }, OPTS);
+    expect(transition.emit).toBeUndefined();
+    expect(transition.phase?.kind).toBe("pressing");
+  });
+
+  it("release while lifted (no movement) drops at the lifted tile's own slot", () => {
+    let transition = nextDragPhase(press(true), { type: "long-press" }, OPTS);
+    transition = nextDragPhase(transition.phase, { type: "pointer-up" }, OPTS);
+    expect(transition.emit).toEqual({ kind: "drop", id: "t1", targetCell: null });
+  });
+});
+
+describe("nextDragPhase — cancellations", () => {
+  it("cancel returns to idle from any phase without emitting", () => {
+    for (const phase of [
+      { kind: "idle" as const },
+      press(),
+      nextDragPhase(
+        press(),
+        { type: "pointer-move", x: 40, y: 40, targetCell: { col: 2, row: 1 } },
+        OPTS,
+      ).phase,
+    ]) {
+      const transition = nextDragPhase(phase, { type: "cancel" }, OPTS);
+      expect(transition.phase).toEqual({ kind: "idle" });
+      expect(transition.emit).toBeUndefined();
+    }
+  });
+
+  it("events in idle are inert", () => {
+    expect(nextDragPhase({ kind: "idle" }, { type: "pointer-up" }, OPTS).phase).toEqual({
+      kind: "idle",
+    });
+    expect(
+      nextDragPhase(
+        { kind: "idle" },
+        { type: "pointer-move", x: 1, y: 1, targetCell: { col: 1, row: 1 } },
+        OPTS,
+      ).phase,
+    ).toEqual({ kind: "idle" });
+    expect(nextDragPhase({ kind: "idle" }, { type: "long-press" }, OPTS).phase).toEqual({
+      kind: "idle",
+    });
+  });
+
+  it("a second pointer-down restarts the gesture with the new tile", () => {
+    const dragging = nextDragPhase(
+      press(),
+      { type: "pointer-move", x: 40, y: 40, targetCell: { col: 2, row: 1 } },
+      OPTS,
+    ).phase;
+    const transition = nextDragPhase(dragging, down({ id: "t2" }), OPTS);
+    expect(transition.phase).toEqual({ kind: "pressing", id: "t2", x: 10, y: 10, touch: false });
+  });
+});