import { describe, expect, it } from "vitest";

import { reinsertAt } from "./reinsert";

describe("reinsertAt", () => {
  it("puts a row back where it was when nothing changed", () => {
    expect(reinsertAt(["a", "b", "c"], ["b"], ["a", "c"])).toEqual({
      keys: ["b"],
      positions: [1],
    });
  });

  it("follows its neighbour when a row was added above it meanwhile", () => {
    // "x" landed at the top between the removal and the Undo: index 1 would now sit before "a".
    expect(reinsertAt(["a", "b", "c"], ["b"], ["x", "a", "c"])).toEqual({
      keys: ["b"],
      positions: [2],
    });
  });

  it("follows its neighbour through a reorder", () => {
    expect(reinsertAt(["a", "b", "c"], ["b"], ["c", "a"])).toEqual({ keys: ["b"], positions: [2] });
  });

  it("walks further back when its neighbour is gone too", () => {
    expect(reinsertAt(["a", "b", "c", "d"], ["c"], ["b", "d"])).toEqual({
      keys: ["c"],
      positions: [1],
    });
  });

  it("goes to the start when it was first or no earlier row is left", () => {
    expect(reinsertAt(["a", "b"], ["a"], ["x", "b"])).toEqual({ keys: ["a"], positions: [0] });
    expect(reinsertAt(["a", "b", "c"], ["b"], ["c"])).toEqual({ keys: ["b"], positions: [0] });
  });

  it("keeps scattered and adjacent removed rows in their order, ascending", () => {
    // A season's episodes interleaved with another's: b and d out, then "x" added at the top.
    expect(reinsertAt(["a", "b", "c", "d", "e"], ["d", "b"], ["x", "a", "c", "e"])).toEqual({
      keys: ["b", "d"],
      positions: [2, 4],
    });
    expect(reinsertAt(["a", "b", "c", "d"], ["b", "c"], ["a", "d"])).toEqual({
      keys: ["b", "c"],
      positions: [1, 2],
    });
  });

  it("skips a row that is already back", () => {
    expect(reinsertAt(["a", "b", "c"], ["b", "c"], ["a", "c"])).toEqual({
      keys: ["b"],
      positions: [1],
    });
  });
});