feat(commands): add new command LINSERT

src/commands/index.js

@@ -52,6 +52,7 @@ export * from './llen';
 export * from './lpop';
 export * from './lpopBuffer';
 export * from './lpush';
+export * from './linsert';
 export * from './lpushx';
 export * from './lrange';
 export * from './lrem';

src/commands/linsert.js

@@ -0,0 +1,25 @@
+export function linsert(key, position, pivot, element) {
+  if (this.data.has(key) && !(this.data.get(key) instanceof Array)) {
+    throw new Error(`Key ${key} does not contain a list`);
+  }
+  const list = this.data.get(key) || [];
+  const pivotIndex = list.indexOf(pivot);
+  if (pivotIndex < 0) return -1;
+  let elementIndex = pivotIndex;
+  switch (position) {
+    case `BEFORE`:
+      elementIndex = pivotIndex;
+      break;
+    case `AFTER`:
+      elementIndex = pivotIndex + 1;
+      break;
+    default:
+      throw new Error(
+        `The position of the new element must be BEFORE the pivot or AFTER the pivot`
+      );
+  }
+  list.splice(elementIndex, 0, element);
+  const {length} = list;
+  this.data.set(key, list);
+  return length;
+}

test/commands/linsert.js

@@ -0,0 +1,62 @@
+import MockRedis from '../../src';
+
+describe('linsert', () => {
+  it('should add the value to the list at the correct position', () => {
+    const redis = new MockRedis({
+      data: {
+        foo: ['1'],
+      },
+    });
+
+    return redis
+      .linsert('foo', `BEFORE`, 1, 0)
+      .then(() => expect(redis.data.get('foo')).toEqual(['0', '1']))
+      .then(() => redis.linsert('foo', `AFTER`, 1, 2))
+      .then(() => expect(redis.data.get('foo')).toEqual(['0', '1', '2']));
+  });
+
+  it('should return the new length of the list', () => {
+    let redis = new MockRedis({
+      data: {},
+    });
+
+    return redis
+      .linsert('foo', `BEFORE`, 1, 0)
+      .then((length) => expect(length).toBe(-1))
+      .then(() => {
+        redis = new MockRedis({
+          data: { foo: ['1'] },
+        });
+      })
+      .then(() => redis.linsert('foo', `BEFORE`, 1, 0))
+      .then((length) => expect(length).toBe(2));
+  });
+
+  it('should throw an exception if the key contains something other than a list', () => {
+    const redis = new MockRedis({
+      data: {
+        foo: 'not a list',
+      },
+    });
+
+    return redis
+      .linsert('foo', `BEFORE`, 1, 0)
+      .catch((err) =>
+        expect(err.message).toBe('Key foo does not contain a list')
+      );
+  });
+
+  it('should throw an exception if the position is not allowed', () => {
+    const redis = new MockRedis({
+      data: {},
+    });
+
+    return redis
+      .linsert(`foo`, `POSITION_UNKNOWN`, 1, 0)
+      .catch((err) =>
+        expect(err.message).toBe(
+          `The position of the new element must be BEFORE the pivot or AFTER the pivot`
+        )
+      );
+  });
+});