feat: add support for COPY command (#2016)

Author: akahn

commands.go

@@ -143,6 +143,7 @@ type Cmdable interface {
 	SetXX(ctx context.Context, key string, value interface{}, expiration time.Duration) *BoolCmd
 	SetRange(ctx context.Context, key string, offset int64, value string) *IntCmd
 	StrLen(ctx context.Context, key string) *IntCmd
+	Copy(ctx context.Context, sourceKey string, destKey string, db int, replace bool) *IntCmd
 
 	GetBit(ctx context.Context, key string, offset int64) *IntCmd
 	SetBit(ctx context.Context, key string, offset int64, value int) *IntCmd
@@ -1025,6 +1026,16 @@ func (c cmdable) StrLen(ctx context.Context, key string) *IntCmd {
 	return cmd
 }
 
+func (c cmdable) Copy(ctx context.Context, sourceKey, destKey string, db int, replace bool) *IntCmd {
+	args := []interface{}{"copy", sourceKey, destKey, "DB", db}
+	if replace {
+		args = append(args, "REPLACE")
+	}
+	cmd := NewIntCmd(ctx, args...)
+	_ = c(ctx, cmd)
+	return cmd
+}
+
 //------------------------------------------------------------------------------
 
 func (c cmdable) GetBit(ctx context.Context, key string, offset int64) *IntCmd {

commands_test.go

@@ -1633,6 +1633,32 @@ var _ = Describe("Commands", func() {
 			Expect(strLen.Err()).NotTo(HaveOccurred())
 			Expect(strLen.Val()).To(Equal(int64(0)))
 		})
+
+		It("should Copy", func() {
+			set := client.Set(ctx, "key", "hello", 0)
+			Expect(set.Err()).NotTo(HaveOccurred())
+			Expect(set.Val()).To(Equal("OK"))
+
+			copy := client.Copy(ctx, "key", "newKey", redisOptions().DB, false)
+			Expect(copy.Err()).NotTo(HaveOccurred())
+			Expect(copy.Val()).To(Equal(int64(1)))
+
+			// Value is available by both keys now
+			getOld := client.Get(ctx, "key")
+			Expect(getOld.Err()).NotTo(HaveOccurred())
+			Expect(getOld.Val()).To(Equal("hello"))
+			getNew := client.Get(ctx, "newKey")
+			Expect(getNew.Err()).NotTo(HaveOccurred())
+			Expect(getNew.Val()).To(Equal("hello"))
+
+			// Overwriting an existing key should not succeed
+			overwrite := client.Copy(ctx, "newKey", "key", redisOptions().DB, false)
+			Expect(overwrite.Val()).To(Equal(int64(0)))
+
+			// Overwrite is allowed when replace=rue
+			replace := client.Copy(ctx, "newKey", "key", redisOptions().DB, true)
+			Expect(replace.Val()).To(Equal(int64(1)))
+		})
 	})
 
 	Describe("hashes", func() {