Add support for LCS Command (redis#2480)

* feat: initial set up for LCSCmd

* feat: adding test for LCS with no additional params

* feat: adding test for LCS with LEN param

* feat: resolving conflicts in command.go

* fix: changing reply and query structure

* feat: commands test for lcs and lcs with len

* fix: using dynamic args length

* fix: read

* fix: Cmd init

* sorting out the LCS commands

Signed-off-by: monkey92t <golang@88.com>

* fix: Adding error case test

* fix: adding correct error message

* fix: removed blank lines

---------

Signed-off-by: monkey92t <golang@88.com>
Co-authored-by: Anuragkillswitch <70265851+Anuragkillswitch@users.noreply.github.com>
Co-authored-by: monkey92t <golang@88.com>

Author: SoulPancake

command.go

@@ -3993,9 +3993,178 @@ func (cmd *FunctionListCmd) readFunctions(rd *proto.Reader) ([]Function, error)
 	return functions, nil
 }
 
-type FilterBy struct {
-	Module  string
-	ACLCat  string
-	Pattern string
+//------------------------------------------------------------------------------
+
+// LCSQuery is a parameter used for the LCS command
+type LCSQuery struct {
+	Key1         string
+	Key2         string
+	Len          bool
+	Idx          bool
+	MinMatchLen  int
+	WithMatchLen bool
+}
+
+// LCSMatch is the result set of the LCS command.
+type LCSMatch struct {
+	MatchString string
+	Matches     []LCSMatchedPosition
+	Len         int64
+}
+
+type LCSMatchedPosition struct {
+	Key1 LCSPosition
+	Key2 LCSPosition
+
+	// only for withMatchLen is true
+	MatchLen int64
+}
+
+type LCSPosition struct {
+	Start int64
+	End   int64
+}
+
+type LCSCmd struct {
+	baseCmd
+
+	// 1: match string
+	// 2: match len
+	// 3: match idx LCSMatch
+	readType uint8
+	val      *LCSMatch
+}
+
+func NewLCSCmd(ctx context.Context, q *LCSQuery) *LCSCmd {
+	args := make([]interface{}, 3, 7)
+	args[0] = "lcs"
+	args[1] = q.Key1
+	args[2] = q.Key2
+
+	cmd := &LCSCmd{readType: 1}
+	if q.Len {
+		cmd.readType = 2
+		args = append(args, "len")
+	} else if q.Idx {
+		cmd.readType = 3
+		args = append(args, "idx")
+		if q.MinMatchLen != 0 {
+			args = append(args, "minmatchlen", q.MinMatchLen)
+		}
+		if q.WithMatchLen {
+			args = append(args, "withmatchlen")
+		}
+	}
+	cmd.baseCmd = baseCmd{
+		ctx:  ctx,
+		args: args,
+	}
+
+	return cmd
+}
+
+func (cmd *LCSCmd) SetVal(val *LCSMatch) {
+	cmd.val = val
+}
+
+func (cmd *LCSCmd) String() string {
+	return cmdString(cmd, cmd.val)
+}
+
+func (cmd *LCSCmd) Val() *LCSMatch {
+	return cmd.val
+}
+
+func (cmd *LCSCmd) Result() (*LCSMatch, error) {
+	return cmd.val, cmd.err
+}
+
+func (cmd *LCSCmd) readReply(rd *proto.Reader) (err error) {
+	lcs := &LCSMatch{}
+	switch cmd.readType {
+	case 1:
+		// match string
+		if lcs.MatchString, err = rd.ReadString(); err != nil {
+			return err
+		}
+	case 2:
+		// match len
+		if lcs.Len, err = rd.ReadInt(); err != nil {
+			return err
+		}
+	case 3:
+		// read LCSMatch
+		if err = rd.ReadFixedMapLen(2); err != nil {
+			return err
+		}
+
+		// read matches or len field
+		for i := 0; i < 2; i++ {
+			key, err := rd.ReadString()
+			if err != nil {
+				return err
+			}
+
+			switch key {
+			case "matches":
+				// read array of matched positions
+				if lcs.Matches, err = cmd.readMatchedPositions(rd); err != nil {
+					return err
+				}
+			case "len":
+				// read match length
+				if lcs.Len, err = rd.ReadInt(); err != nil {
+					return err
+				}
+			}
+		}
+	}
+
+	cmd.val = lcs
+	return nil
 }
 
+func (cmd *LCSCmd) readMatchedPositions(rd *proto.Reader) ([]LCSMatchedPosition, error) {
+	n, err := rd.ReadArrayLen()
+	if err != nil {
+		return nil, err
+	}
+
+	positions := make([]LCSMatchedPosition, n)
+	for i := 0; i < n; i++ {
+		pn, err := rd.ReadArrayLen()
+		if err != nil {
+			return nil, err
+		}
+
+		if positions[i].Key1, err = cmd.readPosition(rd); err != nil {
+			return nil, err
+		}
+		if positions[i].Key2, err = cmd.readPosition(rd); err != nil {
+			return nil, err
+		}
+
+		// read match length if WithMatchLen is true
+		if pn > 2 {
+			if positions[i].MatchLen, err = rd.ReadInt(); err != nil {
+				return nil, err
+			}
+		}
+	}
+
+	return positions, nil
+}
+
+func (cmd *LCSCmd) readPosition(rd *proto.Reader) (pos LCSPosition, err error) {
+	if err = rd.ReadFixedArrayLen(2); err != nil {
+		return pos, err
+	}
+	if pos.Start, err = rd.ReadInt(); err != nil {
+		return pos, err
+	}
+	if pos.End, err = rd.ReadInt(); err != nil {
+		return pos, err
+	}
+
+	return pos, nil
+}

commands.go

@@ -227,6 +227,7 @@ type Cmdable interface {
 	BLMPop(ctx context.Context, timeout time.Duration, direction string, count int64, keys ...string) *KeyValuesCmd
 	BRPop(ctx context.Context, timeout time.Duration, keys ...string) *StringSliceCmd
 	BRPopLPush(ctx context.Context, source, destination string, timeout time.Duration) *StringCmd
+	LCS(ctx context.Context, q *LCSQuery) *LCSCmd
 	LIndex(ctx context.Context, key string, index int64) *StringCmd
 	LInsert(ctx context.Context, key, op string, pivot, value interface{}) *IntCmd
 	LInsertBefore(ctx context.Context, key string, pivot, value interface{}) *IntCmd
@@ -543,6 +544,13 @@ func (c cmdable) Command(ctx context.Context) *CommandsInfoCmd {
 	return cmd
 }
 
+// FilterBy is used for the `CommandList` command parameter.
+type FilterBy struct {
+	Module  string
+	ACLCat  string
+	Pattern string
+}
+
 func (c cmdable) CommandList(ctx context.Context, filter *FilterBy) *StringSliceCmd {
 	args := make([]interface{}, 0, 5)
 	args = append(args, "command", "list")
@@ -1524,6 +1532,12 @@ func (c cmdable) BRPopLPush(ctx context.Context, source, destination string, tim
 	return cmd
 }
 
+func (c cmdable) LCS(ctx context.Context, q *LCSQuery) *LCSCmd {
+	cmd := NewLCSCmd(ctx, q)
+	_ = c(ctx, cmd)
+	return cmd
+}
+
 func (c cmdable) LIndex(ctx context.Context, key string, index int64) *StringCmd {
 	cmd := NewStringCmd(ctx, "lindex", key, index)
 	_ = c(ctx, cmd)

commands_test.go

@@ -2251,6 +2251,86 @@ var _ = Describe("Commands", func() {
 			Expect(v).To(Equal("c"))
 		})
 
+		It("should LCS", func() {
+			err := client.MSet(ctx, "key1", "ohmytext", "key2", "mynewtext").Err()
+			Expect(err).NotTo(HaveOccurred())
+
+			lcs, err := client.LCS(ctx, &redis.LCSQuery{
+				Key1: "key1",
+				Key2: "key2",
+			}).Result()
+
+			Expect(err).NotTo(HaveOccurred())
+			Expect(lcs.MatchString).To(Equal("mytext"))
+
+			lcs, err = client.LCS(ctx, &redis.LCSQuery{
+				Key1: "nonexistent_key1",
+				Key2: "key2",
+			}).Result()
+
+			Expect(err).NotTo(HaveOccurred())
+			Expect(lcs.MatchString).To(Equal(""))
+
+			lcs, err = client.LCS(ctx, &redis.LCSQuery{
+				Key1: "key1",
+				Key2: "key2",
+				Len:  true,
+			}).Result()
+			Expect(err).NotTo(HaveOccurred())
+			Expect(lcs.MatchString).To(Equal(""))
+			Expect(lcs.Len).To(Equal(int64(6)))
+
+			lcs, err = client.LCS(ctx, &redis.LCSQuery{
+				Key1: "key1",
+				Key2: "key2",
+				Idx:  true,
+			}).Result()
+			Expect(err).NotTo(HaveOccurred())
+			Expect(lcs.MatchString).To(Equal(""))
+			Expect(lcs.Len).To(Equal(int64(6)))
+			Expect(lcs.Matches).To(Equal([]redis.LCSMatchedPosition{
+				{
+					Key1:     redis.LCSPosition{Start: 4, End: 7},
+					Key2:     redis.LCSPosition{Start: 5, End: 8},
+					MatchLen: 0,
+				},
+				{
+					Key1:     redis.LCSPosition{Start: 2, End: 3},
+					Key2:     redis.LCSPosition{Start: 0, End: 1},
+					MatchLen: 0,
+				},
+			}))
+
+			lcs, err = client.LCS(ctx, &redis.LCSQuery{
+				Key1:         "key1",
+				Key2:         "key2",
+				Idx:          true,
+				MinMatchLen:  3,
+				WithMatchLen: true,
+			}).Result()
+			Expect(err).NotTo(HaveOccurred())
+			Expect(lcs.MatchString).To(Equal(""))
+			Expect(lcs.Len).To(Equal(int64(6)))
+			Expect(lcs.Matches).To(Equal([]redis.LCSMatchedPosition{
+				{
+					Key1:     redis.LCSPosition{Start: 4, End: 7},
+					Key2:     redis.LCSPosition{Start: 5, End: 8},
+					MatchLen: 4,
+				},
+			}))
+
+			_, err = client.Set(ctx, "keywithstringvalue", "golang", 0).Result()
+			Expect(err).NotTo(HaveOccurred())
+			_, err = client.LPush(ctx, "keywithnonstringvalue", "somevalue").Result()
+			Expect(err).NotTo(HaveOccurred())
+			_, err = client.LCS(ctx, &redis.LCSQuery{
+				Key1: "keywithstringvalue",
+				Key2: "keywithnonstringvalue",
+			}).Result()
+			Expect(err).To(HaveOccurred())
+			Expect(err.Error()).To(Equal("ERR The specified keys must contain string values"))
+		})
+
 		It("should LIndex", func() {
 			lPush := client.LPush(ctx, "list", "World")
 			Expect(lPush.Err()).NotTo(HaveOccurred())