feat(commands): add new command LMOVE (#1292)

Co-authored-by: Philip Nicholls <[email protected]>

src/commands/index.js

@@ -55,6 +55,7 @@ export * from './lastsave'
 export * from './lindex'
 export * from './linsert'
 export * from './llen'
+export * from './lmove'
 export * from './lolwut'
 export * from './lpop'
 export * from './lpush'

src/commands/lmove.js

@@ -0,0 +1,48 @@
+export function lmove(listKey1, listKey2, position1, position2) {
+
+  if (this.data.has(listKey1) && !(this.data.get(listKey1) instanceof Array)) {
+    throw new Error(`Key ${listKey1} does not contain a list`)
+  }
+  if (this.data.has(listKey2) && !(this.data.get(listKey2) instanceof Array)) {
+    throw new Error(`Key ${listKey2} does not contain a list`)
+  }
+
+  if (position1 !== "LEFT" && position1 !== "RIGHT") {
+    throw new Error("Position1 argument must be 'LEFT' or 'RIGHT'");
+  }
+  if (position2 !== "LEFT" && position2 !== "RIGHT") {
+    throw new Error("Position2 argument must be 'LEFT' or 'RIGHT'");
+  }
+
+  const list1 = this.data.get(listKey1) || []
+  let list2 = list1; // Operate on the same list
+  if (listKey1 !== listKey2) {
+    // Operate on two different lists
+    list2 = this.data.get(listKey2) || []
+  }
+
+  if (list1.length === 0) {
+    return null;
+  }
+
+  let value;
+  if (position1 === "LEFT") {
+    value = list1.shift();
+  } else {
+    value = list1.pop();
+  }
+
+  if (position2 === "LEFT") {
+    list2.unshift(value);
+  } else {
+    list2.push(value);
+  }
+
+  this.data.set(listKey1, list1);
+  if (listKey2 !== listKey1) {
+    this.data.set(listKey2, list2);
+  }
+
+  return value
+
+}

test/integration/commands/lmove.js

@@ -0,0 +1,132 @@
+import Redis from 'ioredis'
+
+// eslint-disable-next-line import/no-relative-parent-imports
+import { runTwinSuite } from '../../../test-utils'
+
+runTwinSuite('lmove', command => {
+  describe(command, () => {
+    const redis = new Redis()
+    afterAll(() => {
+      redis.disconnect()
+    })
+
+    const listId1 = "LIST1";
+    const listId2 = "LIST2";
+    const emptyList = "EMPTY";
+    const notalist = "NOTALIST";
+
+    beforeEach(async () => {
+      await redis.del(listId1);
+      await redis.del(listId2);
+      await redis.del(notalist);
+
+      await redis.lpush(emptyList, "TEST");
+      await redis.lpop(emptyList);
+      const membersEmpty = await redis.lrange(listId1, 0, -1);
+      expect(membersEmpty).toEqual([]);
+
+      await redis.lpush(listId1, ['two', 'one']);
+      await redis.lpush(listId2, ['four', 'three']);
+      await redis.set(notalist, "TEST");
+      const members1 = await redis.lrange(listId1, 0, -1);
+      const members2 = await redis.lrange(listId2, 0, -1);
+      expect(members1).toEqual(['one', 'two']);
+      expect(members2).toEqual(['three', 'four']);
+    });
+
+    it('should move the value from LEFT of list1 to LEFT of list2', async () => {
+      const result = await redis.lmove(listId1, listId2, "LEFT", "LEFT");
+      expect(result).toEqual('one');
+
+      const current1 = await redis.lrange(listId1, 0, -1);
+      const current2 = await redis.lrange(listId2, 0, -1);
+      expect(current1).toEqual(['two']);
+      expect(current2).toEqual(['one', 'three', 'four']);
+    });
+
+    it('should move the value from RIGHT of list1 to LEFT of list2', async () => {
+      const result = await redis.lmove(listId1, listId2, "RIGHT", "LEFT");
+      expect(result).toEqual('two');
+
+      const current1 = await redis.lrange(listId1, 0, -1);
+      const current2 = await redis.lrange(listId2, 0, -1);
+      expect(current1).toEqual(['one']);
+      expect(current2).toEqual(['two', 'three', 'four']);
+    });
+
+    it('should move the value from LEFT of list1 to RIGHT of list2', async () => {
+      const result = await redis.lmove(listId1, listId2, "LEFT", "RIGHT");
+      expect(result).toEqual('one');
+
+      const current1 = await redis.lrange(listId1, 0, -1);
+      const current2 = await redis.lrange(listId2, 0, -1);
+      expect(current1).toEqual(['two']);
+      expect(current2).toEqual(['three', 'four', 'one']);
+    });
+
+    it('should move the value from RIGHT of list1 to RIGHT of list2', async () => {
+      const result = await redis.lmove(listId1, listId2, "RIGHT", "RIGHT");
+      expect(result).toEqual('two');
+
+      const current1 = await redis.lrange(listId1, 0, -1);
+      const current2 = await redis.lrange(listId2, 0, -1);
+      expect(current1).toEqual(['one']);
+      expect(current2).toEqual(['three', 'four', 'two']);
+    });
+
+    it('should rotate the list if the source and destination are the same', async () => {
+      const result = await redis.lmove(listId2, listId2, "LEFT", "RIGHT");
+      expect(result).toEqual('three');
+
+      const current1 = await redis.lrange(listId1, 0, -1);
+      const current2 = await redis.lrange(listId2, 0, -1);
+      expect(current1).toEqual(['one', 'two']);
+      expect(current2).toEqual(['four', 'three']);
+    });
+
+    it('should perform no operation if the source is an empty list', async () => {
+      const result = await redis.lmove(emptyList, listId2, "LEFT", "LEFT");
+      expect(result).toEqual(null);
+
+      const current1 = await redis.lrange(listId1, 0, -1);
+      const current2 = await redis.lrange(listId2, 0, -1);
+      expect(current1).toEqual(['one', 'two']);
+      expect(current2).toEqual(['three', 'four']);
+    });
+
+    it('should perform no operation if the source and destination are the same and both positions are LEFT', async () => {
+      const result = await redis.lmove(listId2, listId2, "LEFT", "LEFT");
+      expect(result).toEqual('three');
+
+      const current1 = await redis.lrange(listId1, 0, -1);
+      const current2 = await redis.lrange(listId2, 0, -1);
+      expect(current1).toEqual(['one', 'two']);
+      expect(current2).toEqual(['three', 'four']);
+    });
+
+    it('should perform no operation if the source and destination are the same and both positions are RIGHT', async () => {
+      const result = await redis.lmove(listId2, listId2, "RIGHT", "RIGHT");
+      expect(result).toEqual('four');
+
+      const current1 = await redis.lrange(listId1, 0, -1);
+      const current2 = await redis.lrange(listId2, 0, -1);
+      expect(current1).toEqual(['one', 'two']);
+      expect(current2).toEqual(['three', 'four']);
+    });
+
+
+    it('should perform no operation and return nil when source does not exist', async () => {
+      const value = await redis.get("unknown");
+      expect(value).toEqual(null); // Ensures nil is being represented by null
+
+      const result = await redis.lmove("unknown", listId2, "LEFT", "LEFT");
+      expect(result).toEqual(null);
+    });
+
+    it('should error if the value is not a list', async () => {
+      expect(async () => {
+        await redis.lmove(notalist, listId2, "LEFT", "LEFT");
+      }).rejects.toThrow("Key NOTALIST does not contain a list");
+    });
+  })
+})