added LRANGE keyword and serializeRESP function

1 files changed, 78 insertions, 0 deletions

diff --git a/main.go b/main.go
index 96d4b8a..8aa1354 100644
--- a/main.go
+++ b/main.go
@@ -183,6 +183,76 @@ func handleRpush(conn net.Conn, args []string) {
 	conn.Write([]byte(":" + strconv.Itoa(len(list)) + "\r\n"))
 }
 
+func handleLrange(conn net.Conn, key string, start, stop int) {
+    db.mu.Lock()
+    defer db.mu.Unlock()
+
+    value, exists := db.data[key]
+    if !exists {
+        conn.Write([]byte("*0\r\n"))
+        return
+    }
+    
+    typedList, ok := value.([]string)
+    if !ok {
+        conn.Write([]byte("-WRONGTYPE Operation against a key holding the wrong kind of value\r\n"))
+        return
+    }
+    
+    size := len(typedList)
+
+    if start < 0 {
+        start += size
+        if start < 0 {
+            start = 0
+        }
+    }
+    
+    if stop < 0 {
+        stop += size
+        if stop < 0 {
+            stop = 0
+        }
+    }
+
+    if stop >= size {
+        stop = size - 1
+    }
+
+    if start > stop || start >= size {
+        conn.Write([]byte("*0\r\n"))
+        return
+    }
+
+    resultList := typedList[start : stop+1]
+    conn.Write(serializeRESP(resultList))
+}
+
+func serializeRESP(v any) []byte {
+    switch val := v.(type) {
+    case string:
+		bulkString := fmt.Sprintf("$%d\r\n%s\r\n", len(val), val)
+        return []byte(bulkString)
+    case int:
+		integerString := fmt.Sprintf(":%d\r\n",val)
+        return []byte(integerString)
+    case nil:
+		return []byte("$-1\r\n")
+    case error:
+        errorString := fmt.Sprintf("-ERR %s\r\n",val.Error())
+		return []byte(errorString)
+    case []string:
+        size := len(val)
+		result := []byte(fmt.Sprintf("*%d\r\n", size))
+		for i := 0; i < size; i++ {
+			result = append(result, serializeRESP(val[i])...)
+		}
+		return result
+    default:
+        return []byte("-ERR internal server error: unknown type\r\n")
+    }
+}
+
 func parseRESP(reader *bufio.Reader) ([]string, error) {
 	line, err := reader.ReadString('\n')
 	if err != nil {
@@ -276,6 +346,14 @@ func handleConnection(conn net.Conn) {
 			handleFlushall(conn)
 		case command == "RPUSH" && len(args) >= 3:
             handleRpush(conn, args)
+		case command == "LRANGE" && len(args) == 4:
+            start, err1 := strconv.Atoi(args[2])
+            stop, err2 := strconv.Atoi(args[3])
+            if err1 != nil || err2 != nil {
+                conn.Write([]byte("-ERR value is not an integer or out of range\r\n"))
+                break 
+            }
+            handleLrange(conn, args[1], start, stop)
 		default:
 			conn.Write([]byte("-ERR unknown command or wrong arguments\r\n"))
 		}