add reverse

packages/json-patch-plus/src/reverse.spec.ts

@@ -0,0 +1,155 @@
+import { reverse } from "./reverse";
+
+it("reverses a primitive delta (replace)", () => {
+  expect(reverse([1, 2])).toStrictEqual([2, 1]);
+});
+
+it("reverses a primitive delta (replace and no previous value)", () => {
+  expect(reverse([null, 2])).toStrictEqual([2, null]);
+});
+
+it("reverses a nested delta (replace)", () => {
+  expect(reverse({ a: [1, 2] })).toStrictEqual({ a: [2, 1] });
+});
+
+it("reverses a nested delta (replace and no previous value)", () => {
+  expect(reverse({ a: [null, 2] })).toStrictEqual({ a: [2, null] });
+});
+
+it("reverses a nested delta (add)", () => {
+  expect(reverse({ a: [2] })).toStrictEqual({ a: [2, 0, 0] });
+});
+
+it("reverses a nested delta (key removed)", () => {
+  expect(
+    reverse({
+      b: [2, 0, 0],
+    })
+  ).toStrictEqual({
+    b: [2],
+  });
+});
+
+it("reverses a deeply nested delta (replace)", () => {
+  expect(reverse({ a: { a: [1, 2] } })).toStrictEqual({ a: { a: [2, 1] } });
+});
+
+it("reverses a deeply nested delta (replace and no previous value)", () => {
+  expect(reverse({ a: { a: [null, 2] } })).toStrictEqual({
+    a: { a: [2, null] },
+  });
+});
+
+it("reverses a deeply nested delta (add)", () => {
+  expect(reverse({ a: { a: [2] } })).toStrictEqual({ a: { a: [2, 0, 0] } });
+});
+
+it("reverses a deeply nested delta (remove)", () => {
+  expect(reverse({ a: { a: [2, 0, 0] } })).toStrictEqual({ a: { a: [2] } });
+});
+
+it("reverses a deeply nested delta (replace and no previous value)", () => {
+  expect(reverse({ a: { a: [null, 2] } })).toStrictEqual({
+    a: { a: [2, null] },
+  });
+});
+
+it("reverses a text added delta", () => {
+  expect(reverse(["some text"])).toStrictEqual(["some text", 0, 0]);
+});
+
+it("reverses an array added delta", () => {
+  expect(reverse([[1, 2, 3]])).toStrictEqual([[1, 2, 3], 0, 0]);
+});
+
+it("reverses an array delta (simple values)", () => {
+  expect(
+    reverse({
+      _t: "a",
+      _1: [2, 0, 0],
+      _5: [6, 0, 0],
+      _6: [7, 0, 0],
+      6: [9.1],
+    })
+  ).toStrictEqual({
+    _t: "a",
+    1: [2],
+    5: [6],
+    6: [7],
+    _6: [9.1, 0, 0],
+  });
+});
+
+it("reverses array delta (remove first member)", () => {
+  expect(
+    reverse({
+      // indicates that this is an array operation
+      _t: "a",
+      // _ + index of the item
+      _0: [
+        // the item that is modified
+        1,
+        // 0, 0 indicates that the item got deleted
+        0, 0,
+      ],
+    })
+  ).toStrictEqual([2]);
+});
+
+it("nested changes among array insertions and deletions", () => {
+  expect(
+    reverse({
+      _t: "a",
+      0: [{ id: 3 }],
+      2: {
+        inner: {
+          property: ["abc", "abcd"],
+        },
+      },
+      3: [{ id: 9 }],
+      _0: [{ id: 1 }, 0, 0],
+      _1: [{ id: 2 }, 0, 0],
+      _3: [{ id: 5 }, 0, 0],
+      _5: [{ id: 7 }, 0, 0],
+      _6: [{ id: 8 }, 0, 0],
+      _7: [{ id: 10 }, 0, 0],
+      _8: [{ id: 11 }, 0, 0],
+      _9: [{ id: 12 }, 0, 0],
+    })
+  ).toStrictEqual({
+    _t: "a",
+    0: [{ id: 1 }],
+    1: [{ id: 2 }],
+    3: [{ id: 5 }],
+    4: {
+      inner: {
+        property: ["abcd", "abc"],
+      },
+    },
+    5: [{ id: 7 }],
+    6: [{ id: 8 }],
+    7: [{ id: 10 }],
+    8: [{ id: 11 }],
+    9: [{ id: 12 }],
+    _0: [{ id: 3 }, 0, 0],
+    _3: [{ id: 9 }, 0, 0],
+  });
+});
+
+it("reverses text delta (larger than min length)", () => {
+  expect(
+    reverse(["@@ -1,10 +1,11 @@\n -\n-M\n+P\n adre,%0Acu\n+a\n", 0, 2])
+  ).toStrictEqual(["@@ -1,11 +1,10 @@\n -\n-P\n+M\n adre,%0Acu\n-a\n", 0, 2]);
+});
+
+it("reverses text delta (shorter than min length)", () => {
+  expect(reverse(["-Madre,\nc", "-Padre,\ncua"])).toStrictEqual([
+    "-Padre,\ncua",
+    "-Madre,\nc",
+  ]);
+});
+
+it("returns undefined when reversing undefined", () => {
+  // @ts-ignore
+  expect(reverse(undefined)).toStrictEqual(undefined);
+});