/*
 * Copyright (c) 2009-Present, Redis Ltd.
 * All rights reserved.
 *
 * Licensed under your choice of (a) the Redis Source Available License 2.0
 * (RSALv2); or (b) the Server Side Public License v1 (SSPLv1); or (c) the
 * GNU Affero General Public License v3 (AGPLv3).
 */

#include "server.h"
#include "xxhash.h"
#include <math.h> /* isnan(), isinf() */

/* XXH3 64-bit hash produces 16 hex characters when formatted */
#define DIGEST_HEX_LENGTH 16

/* Forward declarations */
int getGenericCommand(client *c);

/*-----------------------------------------------------------------------------
 * String Commands
 *----------------------------------------------------------------------------*/

static int checkStringLength(client *c, long long size, long long append) {
    if (mustObeyClient(c))
        return C_OK;
    /* 'uint64_t' cast is there just to prevent undefined behavior on overflow */
    long long total = (uint64_t)size + append;
    /* Test configured max-bulk-len representing a limit of the biggest string object,
     * and also test for overflow. */
    if (total > server.proto_max_bulk_len || total < size || total < append) {
        addReplyError(c,"string exceeds maximum allowed size (proto-max-bulk-len)");
        return C_ERR;
    }
    return C_OK;
}

/* The setGenericCommand() function implements the SET operation with different
 * options and variants. This function is called in order to implement the
 * following commands: SET, SETEX, PSETEX, SETNX, GETSET.
 *
 * 'flags' changes the behavior of the command (NX, XX, GET, IFEQ, IFNE, IFDEQ
 * or IFDNE - see below).
 *
 * 'expire' represents an expire to set in form of a Redis object as passed
 * by the user. It is interpreted according to the specified 'unit'.
 *
 * 'match_value' is a value to check against if any of IFEQ/IFNE/IFDEQ/IFDNE is
 * present.
 *
 * 'ok_reply' and 'abort_reply' is what the function will reply to the client
 * if the operation is performed, or when it is not because of NX or
 * XX flags.
 *
 * If ok_reply is NULL "+OK" is used.
 * If abort_reply is NULL, "$-1" is used. */

#define OBJ_NO_FLAGS 0
#define OBJ_SET_NX (1<<0)          /* Set if key not exists. */
#define OBJ_SET_XX (1<<1)          /* Set if key exists. */
#define OBJ_EX (1<<2)              /* Set if time in seconds is given */
#define OBJ_PX (1<<3)              /* Set if time in ms in given */
#define OBJ_KEEPTTL (1<<4)         /* Set and keep the ttl */
#define OBJ_SET_GET (1<<5)         /* Set if want to get key before set */
#define OBJ_EXAT (1<<6)            /* Set if timestamp in second is given */
#define OBJ_PXAT (1<<7)            /* Set if timestamp in ms is given */
#define OBJ_PERSIST (1<<8)         /* Set if we need to remove the ttl */
#define OBJ_SET_IFEQ (1<<9)        /* Set if value equals match value */
#define OBJ_SET_IFNE (1<<10)       /* Set if value does not equal match value */
#define OBJ_SET_IFDEQ (1<<11)      /* Set if current digest equals match digest */
#define OBJ_SET_IFDNE (1<<12)      /* Set if current digest does not equal match digest */

/* Forward declaration */
static int getExpireMillisecondsOrReply(client *c, robj *expire, int flags, int unit, long long *milliseconds);

/* Generic SET command family (SET, SETEX, PSETEX, SETNX)
 *
 * Arguments:
 *   valref: A pointer to the robj to be set. This argument may be updated by the function.
 *           The object is expected to have a refcount of 1, allowing its ownership to be
 *           transferred directly to the database to avoid making a copy. If needed, the
 *           function will replace *valref with a new allocation and increment its refcount
 *           so that both the database and the caller maintain valid references.
 */
void setGenericCommand(client *c, int flags, robj *key, robj **valref, robj *expire,
                       int unit, robj *match_value, robj *ok_reply, robj *abort_reply)
{
    long long milliseconds = 0; /* initialized to avoid any harmless warning */
    int found = 0;
    int setkey_flags = 0;

    if (expire && getExpireMillisecondsOrReply(c, expire, flags, unit, &milliseconds) != C_OK) {
        return;
    }

    if (flags & OBJ_SET_GET) {
        if (getGenericCommand(c) == C_ERR) return;
    }

    dictEntryLink link = NULL;
    found = (lookupKeyWriteWithLink(c->db,key,&link) != NULL);

    if ((flags & OBJ_SET_NX && found) ||
        (flags & (OBJ_SET_XX | OBJ_SET_IFEQ | OBJ_SET_IFDEQ) && !found))
    {
        if (!(flags & OBJ_SET_GET)) {
            addReply(c, abort_reply ? abort_reply : shared.null[c->resp]);
        }
        return;
    }

    /* Handle conditional set operations - only set if key is found and condition
     * is met - otherwise return nil. */
    if (found && (flags & (OBJ_SET_IFEQ | OBJ_SET_IFNE | OBJ_SET_IFDEQ | OBJ_SET_IFDNE))) {
        kvobj *current = lookupKeyRead(c->db, key);
        if (checkType(c, current, OBJ_STRING)) {
            return;
        }

        if (flags & OBJ_SET_IFEQ || flags & OBJ_SET_IFNE) {
            robj *current_decoded = getDecodedObject(current);
            int condition = (flags & OBJ_SET_IFEQ) ?
                            sdscmp(current_decoded->ptr, match_value->ptr) == 0 :
                            sdscmp(current_decoded->ptr, match_value->ptr) != 0;
            decrRefCount(current_decoded);
            if (!condition) {
                if (!(flags & OBJ_SET_GET)) {
                    addReply(c, abort_reply ? abort_reply : shared.null[c->resp]);
                }
                return;
            }
        } else if (flags & OBJ_SET_IFDEQ || flags & OBJ_SET_IFDNE) {
            if (validateHexDigest(c, match_value->ptr) != C_OK)
                return;

            sds current_digest = stringDigest(current);
            int condition = flags & OBJ_SET_IFDEQ ?
                            strcasecmp(current_digest, match_value->ptr) == 0 :
                            strcasecmp(current_digest, match_value->ptr) != 0;
            sdsfree(current_digest);
            if (!condition) {
                if (!(flags & OBJ_SET_GET)) {
                    addReply(c, abort_reply ? abort_reply : shared.null[c->resp]);
                }
                return;
            }
        }
    }

    /* When expire is not NULL, we avoid deleting the TTL so it can be updated later instead of being deleted and then created again. */
    setkey_flags |= ((flags & OBJ_KEEPTTL) || expire) ? SETKEY_KEEPTTL : 0;
    setkey_flags |= found ? SETKEY_ALREADY_EXIST : SETKEY_DOESNT_EXIST;

    setKeyByLink(c, c->db, key, valref, setkey_flags, &link);
    /* If there's an expiration, setExpireByLink may reallocate the object.
     * We must update valref to reflect the new object if that happens. */
    if (expire) *valref = setExpireByLink(c, c->db, key->ptr, milliseconds, link);
    /* The client still holds a reference to the original object via c->argv[i],
     * and will call decrRefCount() at the end of call(). We increment the refcount
     * from 1 to 2 to ensure both DB and client have valid references. */
    incrRefCount(*valref); /* 1->2 */

    server.dirty++;
    notifyKeyspaceEvent(NOTIFY_STRING,"set",key,c->db->id);

    if (expire) {
        /* Propagate as SET Key Value PXAT millisecond-timestamp if there is
         * EX/PX/EXAT flag. */
        if (!(flags & OBJ_PXAT)) {
            robj *milliseconds_obj = createStringObjectFromLongLong(milliseconds);
            rewriteClientCommandVector(c, 5, shared.set, key, *valref, shared.pxat, milliseconds_obj);
            decrRefCount(milliseconds_obj);
        }
        notifyKeyspaceEvent(NOTIFY_GENERIC,"expire",key,c->db->id);
    }

    if (!(flags & OBJ_SET_GET)) {
        addReply(c, ok_reply ? ok_reply : shared.ok);
    }

    /* Propagate without the GET argument (Isn't needed if we had expire since in that case we completely re-written the command argv) */
    if ((flags & OBJ_SET_GET) && !expire) {
        int argc = 0;
        int j;
        robj **argv = zmalloc((c->argc-1)*sizeof(robj*));
        for (j=0; j < c->argc; j++) {
            char *a = c->argv[j]->ptr;
            /* Skip GET which may be repeated multiple times. */
            if (j >= 3 &&
                (a[0] == 'g' || a[0] == 'G') &&
                (a[1] == 'e' || a[1] == 'E') &&
                (a[2] == 't' || a[2] == 'T') && a[3] == '\0')
                continue;
            argv[argc++] = c->argv[j];
            incrRefCount(c->argv[j]);
        }
        replaceClientCommandVector(c, argc, argv);
    }
}

/*
 * Extract the `expire` argument of a given GET/SET command as an absolute timestamp in milliseconds.
 *
 * "client" is the client that sent the `expire` argument.
 * "expire" is the `expire` argument to be extracted.
 * "flags" represents the behavior of the command (e.g. PX or EX).
 * "unit" is the original unit of the given `expire` argument (e.g. UNIT_SECONDS).
 * "milliseconds" is output argument.
 *
 * If return C_OK, "milliseconds" output argument will be set to the resulting absolute timestamp.
 * If return C_ERR, an error reply has been added to the given client.
 */
static int getExpireMillisecondsOrReply(client *c, robj *expire, int flags, int unit, long long *milliseconds) {
    int ret = getLongLongFromObjectOrReply(c, expire, milliseconds, NULL);
    if (ret != C_OK) {
        return ret;
    }

    if (*milliseconds <= 0 || (unit == UNIT_SECONDS && *milliseconds > LLONG_MAX / 1000)) {
        /* Negative value provided or multiplication is gonna overflow. */
        addReplyErrorExpireTime(c);
        return C_ERR;
    }

    if (unit == UNIT_SECONDS) *milliseconds *= 1000;

    if ((flags & OBJ_PX) || (flags & OBJ_EX)) {
        *milliseconds += commandTimeSnapshot();
    }

    if (*milliseconds <= 0) {
        /* Overflow detected. */
        addReplyErrorExpireTime(c);
        return C_ERR;
    }

    return C_OK;
}

#define COMMAND_GET 0
#define COMMAND_SET 1
#define COMMAND_MSETEX 2

/* Extended string command arguments structure */
typedef struct {
    int flags;
    int unit;
    int expire_pos;  /* Position of EX/PX flag for replication rewriting */
    robj *expire;
    robj *match_value; /* For IFEQ/IFNE/IFDEQ/IFDNE conditions */
} extendedStringArgs;

/*
 * The parseExtendedStringArgumentsOrReply() function performs the common validation for extended
 * string arguments used in SET, GET and MSETEX commands.
 *
 * Get specific commands - PERSIST/DEL
 * Set specific commands - XX/NX/GET/IFEQ/IFNE/IFDEQ/IFDNE
 * Common commands - EX/EXAT/PX/PXAT/KEEPTTL
 *
 * Function takes pointers to client, start_pos for where to begin parsing, extendedStringArgs
 * structure to populate, and command_type which can be COMMAND_GET, COMMAND_SET, or COMMAND_MSETEX.
 *
 * If there are any syntax violations C_ERR is returned else C_OK is returned.
 *
 * The args structure is updated upon parsing the arguments. Unit and expire are updated if there are any
 * EX/EXAT/PX/PXAT arguments. Unit is updated to millisecond if PX/PXAT is set.
 * match_value is updated if any of IFEQ/IFNE/IFDEQ/IFDNE is set.
 */
int parseExtendedStringArgumentsOrReply(client *c, int start_pos, extendedStringArgs *args, int command_type) {
    /* Initialize arguments to defaults */
    memset(args, 0, sizeof(*args));
    args->expire_pos = -1;
    args->unit = UNIT_SECONDS;

    int j = start_pos;
   /* We can have either none or exactly one of these conditionals as they are
     * mutually exclusive. We'll make sure to check if none of the other flags
     * are already set if we are going to set one of them. This is done via the
     * check:
     *
     * if (opt == OBJ_SET_XXX && !(*flags & (cond_mut_excl & ~OBJ_SET_XXX)))
     *
     * A bit ugly - but concise.
     */
    int cond_mut_excl = OBJ_SET_NX | OBJ_SET_XX | OBJ_SET_IFEQ | OBJ_SET_IFNE |
                        OBJ_SET_IFDEQ | OBJ_SET_IFDNE;
    for (; j < c->argc; j++) {
        char *opt = c->argv[j]->ptr;
        robj *next = (j == c->argc-1) ? NULL : c->argv[j+1];

        if ((opt[0] == 'n' || opt[0] == 'N') &&
            (opt[1] == 'x' || opt[1] == 'X') && opt[2] == '\0' &&
            !(args->flags & OBJ_SET_XX) && (command_type == COMMAND_SET || command_type == COMMAND_MSETEX))
        {
            args->flags |= OBJ_SET_NX;
        } else if ((opt[0] == 'x' || opt[0] == 'X') &&
                   (opt[1] == 'x' || opt[1] == 'X') && opt[2] == '\0' &&
                   !(args->flags & OBJ_SET_NX) && (command_type == COMMAND_SET || command_type == COMMAND_MSETEX))
        {
            args->flags |= OBJ_SET_XX;
        } else if ((opt[0] == 'g' || opt[0] == 'G') &&
                   (opt[1] == 'e' || opt[1] == 'E') &&
                   (opt[2] == 't' || opt[2] == 'T') && opt[3] == '\0' &&
                   (command_type == COMMAND_SET))
        {
            args->flags |= OBJ_SET_GET;
        } else if (!strcasecmp(opt, "KEEPTTL") && !(args->flags & OBJ_PERSIST) &&
            !(args->flags & OBJ_EX) && !(args->flags & OBJ_EXAT) &&
            !(args->flags & OBJ_PX) && !(args->flags & OBJ_PXAT) &&
            (command_type == COMMAND_SET || command_type == COMMAND_MSETEX))
        {
            args->flags |= OBJ_KEEPTTL;
        } else if (!strcasecmp(opt,"PERSIST") && (command_type == COMMAND_GET) &&
               !(args->flags & OBJ_EX) && !(args->flags & OBJ_EXAT) &&
               !(args->flags & OBJ_PX) && !(args->flags & OBJ_PXAT) &&
               !(args->flags & OBJ_KEEPTTL))
        {
            args->flags |= OBJ_PERSIST;
        } else if ((opt[0] == 'e' || opt[0] == 'E') &&
                   (opt[1] == 'x' || opt[1] == 'X') && opt[2] == '\0' &&
                   !(args->flags & OBJ_KEEPTTL) && !(args->flags & OBJ_PERSIST) &&
                   !(args->flags & OBJ_EXAT) && !(args->flags & OBJ_PX) &&
                   !(args->flags & OBJ_PXAT) && next)
        {
            args->flags |= OBJ_EX;
            args->expire = next;
            args->expire_pos = j;
            j++;
        } else if ((opt[0] == 'p' || opt[0] == 'P') &&
                   (opt[1] == 'x' || opt[1] == 'X') && opt[2] == '\0' &&
                   !(args->flags & OBJ_KEEPTTL) && !(args->flags & OBJ_PERSIST) &&
                   !(args->flags & OBJ_EX) && !(args->flags & OBJ_EXAT) &&
                   !(args->flags & OBJ_PXAT) && next)
        {
            args->flags |= OBJ_PX;
            args->unit = UNIT_MILLISECONDS;
            args->expire = next;
            args->expire_pos = j;
            j++;
        } else if ((opt[0] == 'e' || opt[0] == 'E') &&
                   (opt[1] == 'x' || opt[1] == 'X') &&
                   (opt[2] == 'a' || opt[2] == 'A') &&
                   (opt[3] == 't' || opt[3] == 'T') && opt[4] == '\0' &&
                   !(args->flags & OBJ_KEEPTTL) && !(args->flags & OBJ_PERSIST) &&
                   !(args->flags & OBJ_EX) && !(args->flags & OBJ_PX) &&
                   !(args->flags & OBJ_PXAT) && next)
        {
            args->flags |= OBJ_EXAT;
            args->expire = next;
            j++;
        } else if ((opt[0] == 'p' || opt[0] == 'P') &&
                   (opt[1] == 'x' || opt[1] == 'X') &&
                   (opt[2] == 'a' || opt[2] == 'A') &&
                   (opt[3] == 't' || opt[3] == 'T') && opt[4] == '\0' &&
                   !(args->flags & OBJ_KEEPTTL) && !(args->flags & OBJ_PERSIST) &&
                   !(args->flags & OBJ_EX) && !(args->flags & OBJ_EXAT) &&
                   !(args->flags & OBJ_PX) && next)
        {
            args->flags |= OBJ_PXAT;
            args->unit = UNIT_MILLISECONDS;
            args->expire = next;
            j++;
        } else if (!strcasecmp(opt, "ifeq") && next &&
                   !(args->flags & (cond_mut_excl & ~OBJ_SET_IFEQ)) &&
                   (command_type == COMMAND_SET))
        {
            args->flags |= OBJ_SET_IFEQ;
            args->match_value = next;
            j++;
        } else if (!strcasecmp(opt, "ifne") && next &&
                   !(args->flags & (cond_mut_excl & ~OBJ_SET_IFNE)) &&
                   (command_type == COMMAND_SET))
        {
            args->flags |= OBJ_SET_IFNE;
            args->match_value = next;
            j++;
        } else if (!strcasecmp(opt, "ifdeq") && next &&
                   !(args->flags & (cond_mut_excl & ~OBJ_SET_IFDEQ)) &&
                   (command_type == COMMAND_SET))
        {
            args->flags |= OBJ_SET_IFDEQ;
            args->match_value = next;
            j++;
        } else if (!strcasecmp(opt, "ifdne") && next &&
                   !(args->flags & (cond_mut_excl & ~OBJ_SET_IFDNE)) &&
                   (command_type == COMMAND_SET))
        {
            args->flags |= OBJ_SET_IFDNE;
            args->match_value = next;
            j++;
        } else {
            addReplyErrorObject(c,shared.syntaxerr);
            return C_ERR;
        }
    }
    return C_OK;
}

/* SET key value [NX] [XX] [KEEPTTL] [GET] [EX <seconds>] [PX <milliseconds>]
 *     [EXAT <seconds-timestamp>][PXAT <milliseconds-timestamp>]
 *     [IFEQ <match-value>|IFNE <match-value>|IFDEQ <match-digest>|
 *      IFDNE <match-digest>]*/
void setCommand(client *c) {
    extendedStringArgs args;

    if (parseExtendedStringArgumentsOrReply(c, 3, &args, COMMAND_SET) != C_OK) {
        return;
    }

    c->argv[2] = tryObjectEncoding(c->argv[2]);
    setGenericCommand(c, args.flags, c->argv[1], &(c->argv[2]), args.expire, args.unit, args.match_value, NULL, NULL);
}

void setnxCommand(client *c) {
    c->argv[2] = tryObjectEncoding(c->argv[2]);
    setGenericCommand(c, OBJ_SET_NX, c->argv[1], &(c->argv[2]), NULL, 0, NULL, shared.cone, shared.czero);
}

void setexCommand(client *c) {
    c->argv[3] = tryObjectEncoding(c->argv[3]);
    setGenericCommand(c, OBJ_EX, c->argv[1], &(c->argv[3]), c->argv[2], UNIT_SECONDS, NULL, NULL, NULL);
}

void psetexCommand(client *c) {
    c->argv[3] = tryObjectEncoding(c->argv[3]);
    setGenericCommand(c, OBJ_PX, c->argv[1], &(c->argv[3]), c->argv[2], UNIT_MILLISECONDS, NULL, NULL, NULL);
}

int getGenericCommand(client *c) {
    kvobj *o;

    if ((o = lookupKeyReadOrReply(c, c->argv[1], shared.null[c->resp])) == NULL)
        return C_OK;

    if (checkType(c,o,OBJ_STRING)) {
        return C_ERR;
    }

    addReplyBulk(c,o);
    return C_OK;
}

void getCommand(client *c) {
    getGenericCommand(c);
}

/*
 * GETEX <key> [PERSIST][EX seconds][PX milliseconds][EXAT seconds-timestamp][PXAT milliseconds-timestamp]
 *
 * The getexCommand() function implements extended options and variants of the GET command. Unlike GET
 * command this command is not read-only.
 *
 * The default behavior when no options are specified is same as GET and does not alter any TTL.
 *
 * Only one of the below options can be used at a given time.
 *
 * 1. PERSIST removes any TTL associated with the key.
 * 2. EX Set expiry TTL in seconds.
 * 3. PX Set expiry TTL in milliseconds.
 * 4. EXAT Same like EX instead of specifying the number of seconds representing the TTL
 *      (time to live), it takes an absolute Unix timestamp
 * 5. PXAT Same like PX instead of specifying the number of milliseconds representing the TTL
 *      (time to live), it takes an absolute Unix timestamp
 *
 * Command would either return the bulk string, error or nil.
 */
void getexCommand(client *c) {
    extendedStringArgs args;

    if (parseExtendedStringArgumentsOrReply(c, 2, &args, COMMAND_GET) != C_OK) {
        return;
    }

    kvobj *o;

    if ((o = lookupKeyReadOrReply(c,c->argv[1],shared.null[c->resp])) == NULL)
        return;

    if (checkType(c,o,OBJ_STRING)) {
        return;
    }

    /* Validate the expiration time value first */
    long long milliseconds = 0;
    if (args.expire && getExpireMillisecondsOrReply(c, args.expire, args.flags, args.unit, &milliseconds) != C_OK) {
        return;
    }

    /* We need to do this before we expire the key or delete it */
    addReplyBulk(c,o);

    /* This command is never propagated as is. It is either propagated as PEXPIRE[AT],DEL,UNLINK or PERSIST.
     * This why it doesn't need special handling in feedAppendOnlyFile to convert relative expire time to absolute one. */
    if (((args.flags & OBJ_PXAT) || (args.flags & OBJ_EXAT)) && checkAlreadyExpired(milliseconds)) {
        /* When PXAT/EXAT absolute timestamp is specified, there can be a chance that timestamp
         * has already elapsed so delete the key in that case. */
        int deleted = dbGenericDelete(c->db, c->argv[1], server.lazyfree_lazy_expire, DB_FLAG_KEY_EXPIRED);
        serverAssert(deleted);
        robj *aux = server.lazyfree_lazy_expire ? shared.unlink : shared.del;
        rewriteClientCommandVector(c,2,aux,c->argv[1]);
        signalModifiedKey(c, c->db, c->argv[1]);
        notifyKeyspaceEvent(NOTIFY_GENERIC, "del", c->argv[1], c->db->id);
        server.dirty++;
    } else if (args.expire) {
        o = setExpire(c,c->db,c->argv[1],milliseconds);
        /* Propagate as PXEXPIREAT millisecond-timestamp if there is
         * EX/PX/EXAT/PXAT flag and the key has not expired. */
        robj *milliseconds_obj = createStringObjectFromLongLong(milliseconds);
        rewriteClientCommandVector(c,3,shared.pexpireat,c->argv[1],milliseconds_obj);
        decrRefCount(milliseconds_obj);
        signalModifiedKey(c, c->db, c->argv[1]);
        notifyKeyspaceEvent(NOTIFY_GENERIC,"expire",c->argv[1],c->db->id);
        server.dirty++;
    } else if (args.flags & OBJ_PERSIST) {
        if (removeExpire(c->db, c->argv[1])) {
            signalModifiedKey(c, c->db, c->argv[1]);
            rewriteClientCommandVector(c, 2, shared.persist, c->argv[1]);
            notifyKeyspaceEvent(NOTIFY_GENERIC,"persist",c->argv[1],c->db->id);
            server.dirty++;
        }
    }
}

void getdelCommand(client *c) {
    if (getGenericCommand(c) == C_ERR) return;
    if (dbSyncDelete(c->db, c->argv[1])) {
        /* Propagate as DEL command */
        rewriteClientCommandVector(c,2,shared.del,c->argv[1]);
        signalModifiedKey(c, c->db, c->argv[1]);
        notifyKeyspaceEvent(NOTIFY_GENERIC, "del", c->argv[1], c->db->id);
        server.dirty++;
    }
}

void getsetCommand(client *c) {
    if (getGenericCommand(c) == C_ERR) return;
    c->argv[2] = tryObjectEncoding(c->argv[2]);
    setKey(c, c->db, c->argv[1], &c->argv[2], 0);
    incrRefCount(c->argv[2]);
    notifyKeyspaceEvent(NOTIFY_STRING,"set",c->argv[1],c->db->id);
    server.dirty++;

    /* Propagate as SET command */
    rewriteClientCommandArgument(c,0,shared.set);
}

void setrangeCommand(client *c) {
    int64_t oldLen = -1, newLen;
    long offset;
    sds value = c->argv[3]->ptr;
    const size_t value_len = sdslen(value);

    if (getLongFromObjectOrReply(c,c->argv[2],&offset,NULL) != C_OK)
        return;

    if (offset < 0) {
        addReplyError(c,"offset is out of range");
        return;
    }

    dictEntryLink link;
    kvobj *kv = lookupKeyWriteWithLink(c->db, c->argv[1], &link);
    if (kv == NULL) {
        /* Return 0 when setting nothing on a non-existing string */
        if (value_len == 0) {
            addReply(c,shared.czero);
            return;
        }

        /* Return when the resulting string exceeds allowed size */
        if (checkStringLength(c,offset,value_len) != C_OK)
            return;

        newLen = offset+value_len;
        robj *o = createObject(OBJ_STRING,sdsnewlen(NULL, newLen));
        kv = dbAddByLink(c->db, c->argv[1], &o, &link);
    } else {
        /* Key exists, check type */
        if (checkType(c,kv,OBJ_STRING))
            return;

        /* Return existing string length when setting nothing */
        oldLen = stringObjectLen(kv);
        if (value_len == 0) {
            addReplyLongLong(c, oldLen);
            return;
        }

        /* Return when the resulting string exceeds allowed size */
        if (checkStringLength(c,offset,value_len) != C_OK)
            return;

        /* Create a copy when the object is shared or encoded. */
        kv = dbUnshareStringValueByLink(c->db, c->argv[1], kv, link);

        newLen = max(oldLen, (int64_t) (offset + value_len));
        updateKeysizesHist(c->db, getKeySlot(c->argv[1]->ptr), OBJ_STRING, oldLen, newLen);            
    }

    if (value_len > 0) {
        size_t oldsize = 0;
        if (server.memory_tracking_per_slot)
            oldsize = stringObjectAllocSize(kv);
        kv->ptr = sdsgrowzero(kv->ptr,offset+value_len);
        if (server.memory_tracking_per_slot)
            updateSlotAllocSize(c->db, getKeySlot(c->argv[1]->ptr), oldsize, stringObjectAllocSize(kv));
        memcpy((char*)kv->ptr+offset,value,value_len);
        signalModifiedKey(c,c->db,c->argv[1]);
        notifyKeyspaceEvent(NOTIFY_STRING,
            "setrange",c->argv[1],c->db->id);
        server.dirty++;
    }

    addReplyLongLong(c,newLen);
}

void getrangeCommand(client *c) {
    kvobj *o;
    long long start, end;
    char *str, llbuf[32];
    size_t strlen;

    if (getLongLongFromObjectOrReply(c,c->argv[2],&start,NULL) != C_OK)
        return;
    if (getLongLongFromObjectOrReply(c,c->argv[3],&end,NULL) != C_OK)
        return;
    if ((o = lookupKeyReadOrReply(c,c->argv[1],shared.emptybulk)) == NULL ||
        checkType(c,o,OBJ_STRING)) return;

    if (o->encoding == OBJ_ENCODING_INT) {
        str = llbuf;
        strlen = ll2string(llbuf,sizeof(llbuf),(long)o->ptr);
    } else {
        str = o->ptr;
        strlen = sdslen(str);
    }

    /* Convert negative indexes */
    if (start < 0 && end < 0 && start > end) {
        addReply(c,shared.emptybulk);
        return;
    }
    if (start < 0) start = strlen+start;
    if (end < 0) end = strlen+end;
    if (start < 0) start = 0;
    if (end < 0) end = 0;
    if ((unsigned long long)end >= strlen) end = strlen-1;

    /* Precondition: end >= 0 && end < strlen, so the only condition where
     * nothing can be returned is: start > end. */
    if (start > end || strlen == 0) {
        addReply(c,shared.emptybulk);
    } else {
        addReplyBulkCBuffer(c,(char*)str+start,end-start+1);
    }
}

void mgetCommand(client *c) {
    int j;

    addReplyArrayLen(c,c->argc-1);
    for (j = 1; j < c->argc; j++) {
        kvobj *o = lookupKeyRead(c->db, c->argv[j]);
        if (o == NULL) {
            addReplyNull(c);
        } else {
            if (o->type != OBJ_STRING) {
                addReplyNull(c);
            } else {
                addReplyBulk(c,o);
            }
        }
    }
}

void msetGenericCommand(client *c, int nx) {
    int j;

    if ((c->argc % 2) == 0) {
        addReplyErrorArity(c);
        return;
    }

    /* Handle the NX flag. The MSETNX semantic is to return zero and don't
     * set anything if at least one key already exists. */
    if (nx) {
        for (j = 1; j < c->argc; j += 2) {
            if (lookupKeyWrite(c->db,c->argv[j]) != NULL) {
                addReply(c, shared.czero);
                return;
            }
        }
    }

    for (j = 1; j < c->argc; j += 2) {
        c->argv[j+1] = tryObjectEncoding(c->argv[j+1]);
        /* if 'NX', no need set flags SETKEY_DOESNT_EXIST. Already verified earlier! */
        setKey(c, c->db, c->argv[j], &(c->argv[j+1]) , 0 /*flags*/);
        incrRefCount(c->argv[j+1]);  /* refcnt not incr by setKey() */
        notifyKeyspaceEvent(NOTIFY_STRING,"set",c->argv[j],c->db->id);
    }
    server.dirty += (c->argc-1)/2;
    addReply(c, nx ? shared.cone : shared.ok);
}

void msetCommand(client *c) {
    msetGenericCommand(c,0);
}

void msetnxCommand(client *c) {
    msetGenericCommand(c,1);
}

void msetexCommand(client *c) {
    /* Parse numkeys parameter */
    long kv_count;
    if (getRangeLongFromObjectOrReply(c, c->argv[1], 1, INT_MAX,
        &kv_count, "invalid numkeys value") != C_OK)
    {
        return;
    }

    /* Validate we have enough arguments: command + numkeys + (key-value pairs) * 2
     * Be careful to avoid overflow when calculating kv_count * 2 */
    if ((long long)kv_count * 2 + 2 > c->argc) {
        addReplyError(c, "wrong number of key-value pairs");
        return;
    }

    extendedStringArgs args;
    if (parseExtendedStringArgumentsOrReply(c, kv_count * 2 + 2, &args, COMMAND_MSETEX) != C_OK) {
        return;
    }

    /* Validate the expiration time value first */
    long long milliseconds = 0;
    if (args.expire && getExpireMillisecondsOrReply(c, args.expire, args.flags, args.unit, &milliseconds) != C_OK) {
        return;
    }

    if (args.flags & (OBJ_SET_NX | OBJ_SET_XX)) {
        /* Check NX/XX conditions for each key - pattern from setGenericCommand */
        for (int j = 0; j < kv_count; j++) {
            int key_idx = (j * 2) + 2;
            robj *found = lookupKeyWrite(c->db, c->argv[key_idx]);

            if ((args.flags & OBJ_SET_NX && found) ||
                (args.flags & OBJ_SET_XX && !found))
            {
                addReply(c, shared.czero);
                return;
            }
        }
    }

    /* Set all key-value pairs */
    for (int j = 0; j < kv_count; j++) {
        int key_idx = (j * 2) + 2;
        int val_idx = key_idx + 1;

        c->argv[val_idx] = tryObjectEncoding(c->argv[val_idx]);

        /* Handle KEEPTTL - preserve existing TTL */
        int setkey_flags = 0;
        if (args.flags & OBJ_KEEPTTL) {
            setkey_flags |= SETKEY_KEEPTTL;
        }

        setKey(c, c->db, c->argv[key_idx], &(c->argv[val_idx]), setkey_flags);
        incrRefCount(c->argv[val_idx]);

        /* Set expiration for each key (but not for KEEPTTL) */
        if (args.expire && !(args.flags & OBJ_KEEPTTL)) {
            setExpire(c, c->db, c->argv[key_idx], milliseconds);
            notifyKeyspaceEvent(NOTIFY_GENERIC,"expire",c->argv[key_idx],c->db->id);
        }
        notifyKeyspaceEvent(NOTIFY_STRING,"set",c->argv[key_idx],c->db->id);
    }

    /* Handle replication rewriting for relative expiration times */
    if (args.expire && !(args.flags & OBJ_PXAT) && !(args.flags & OBJ_EXAT) && args.expire_pos != -1) {
        /* Convert EX/PX (relative) to PXAT (absolute) for consistent replication */
        robj *milliseconds_obj = createStringObjectFromLongLong(milliseconds);
        rewriteClientCommandArgument(c, args.expire_pos, shared.pxat);
        rewriteClientCommandArgument(c, args.expire_pos + 1, milliseconds_obj);
        decrRefCount(milliseconds_obj);
    }

    server.dirty += kv_count;
    addReply(c, shared.cone);
}

void incrDecrCommand(client *c, long long incr) {
    long long value, oldvalue;
    robj *new;
    dictEntryLink link;
    kvobj *o = lookupKeyWriteWithLink(c->db, c->argv[1], &link);
    if (checkType(c,o,OBJ_STRING)) return;
    if (getLongLongFromObjectOrReply(c,o,&value,NULL) != C_OK) return;

    oldvalue = value;
    if ((incr < 0 && oldvalue < 0 && incr < (LLONG_MIN-oldvalue)) ||
        (incr > 0 && oldvalue > 0 && incr > (LLONG_MAX-oldvalue))) {
        addReplyError(c,"increment or decrement would overflow");
        return;
    }
    value += incr;

    if (o && o->refcount == 1 && o->encoding == OBJ_ENCODING_INT &&
        value >= LONG_MIN && value <= LONG_MAX)
    {
        new = o;
        o->ptr = (void*)((long)value);
        updateKeysizesHist(c->db, getKeySlot(c->argv[1]->ptr),
                           OBJ_STRING,
                           (int64_t) sdigits10(oldvalue),
                           (int64_t) sdigits10(value));
    } else {
        new = createStringObjectFromLongLongForValue(value);
        if (o) {
            /* replace value in db and also update keysizes hist */
            dbReplaceValueWithLink(c->db, c->argv[1], &new, link);
        } else {
            /* Add new key to db and also update keysizes hist */
            dbAddByLink(c->db, c->argv[1], &new, &link);
        }
    }
    addReplyLongLongFromStr(c,new);
    signalModifiedKey(c,c->db,c->argv[1]);
    notifyKeyspaceEvent(NOTIFY_STRING,"incrby",c->argv[1],c->db->id);
    server.dirty++;
}

void incrCommand(client *c) {
    incrDecrCommand(c,1);
}

void decrCommand(client *c) {
    incrDecrCommand(c,-1);
}

void incrbyCommand(client *c) {
    long long incr;

    if (getLongLongFromObjectOrReply(c, c->argv[2], &incr, NULL) != C_OK) return;
    incrDecrCommand(c,incr);
}

void decrbyCommand(client *c) {
    long long incr;

    if (getLongLongFromObjectOrReply(c, c->argv[2], &incr, NULL) != C_OK) return;
    /* Overflow check: negating LLONG_MIN will cause an overflow */
    if (incr == LLONG_MIN) {
        addReplyError(c, "decrement would overflow");
        return;
    }
    incrDecrCommand(c,-incr);
}

void incrbyfloatCommand(client *c) {
    long double incr, value;

    dictEntryLink link;
    kvobj *o = lookupKeyWriteWithLink(c->db,c->argv[1],&link);
    if (checkType(c,o,OBJ_STRING)) return;
    if (getLongDoubleFromObjectOrReply(c,o,&value,NULL) != C_OK ||
        getLongDoubleFromObjectOrReply(c,c->argv[2],&incr,NULL) != C_OK)
        return;

    value += incr;
    if (isnan(value) || isinf(value)) {
        addReplyError(c,"increment would produce NaN or Infinity");
        return;
    }
    robj *new = createStringObjectFromLongDouble(value,1);
    if (o)
        dbReplaceValueWithLink(c->db, c->argv[1], &new, link);
    else
        dbAddByLink(c->db, c->argv[1], &new, &link);
    signalModifiedKey(c,c->db,c->argv[1]);
    notifyKeyspaceEvent(NOTIFY_STRING,"incrbyfloat",c->argv[1],c->db->id);
    server.dirty++;
    addReplyBulk(c,new);

    /* Always replicate INCRBYFLOAT as a SET command with the final value
     * in order to make sure that differences in float precision or formatting
     * will not create differences in replicas or after an AOF restart. */
    rewriteClientCommandArgument(c,0,shared.set);
    rewriteClientCommandArgument(c,2,new);
    rewriteClientCommandArgument(c,3,shared.keepttl);
}

void appendCommand(client *c) {
    size_t totlen;
    robj *append;
    kvobj *o;
    size_t oldsize = 0;

    dictEntryLink link;
    o = lookupKeyWriteWithLink(c->db,c->argv[1],&link);
    if (o == NULL) {
        /* Create the key */
        c->argv[2] = tryObjectEncoding(c->argv[2]);
        dbAddByLink(c->db, c->argv[1], &c->argv[2], &link);
        incrRefCount(c->argv[2]);
        totlen = stringObjectLen(c->argv[2]);
    } else {
        /* Key exists, check type */
        if (checkType(c,o,OBJ_STRING))
            return;

        /* "append" is an argument, so always an sds */
        append = c->argv[2];
        size_t append_len = sdslen(append->ptr);
        if (checkStringLength(c,stringObjectLen(o),append_len) != C_OK)
            return;

        /* Append the value */
        o = dbUnshareStringValueByLink(c->db,c->argv[1],o,link);
        if (server.memory_tracking_per_slot)
            oldsize = stringObjectAllocSize(o);
        o->ptr = sdscatlen(o->ptr,append->ptr,append_len);
        if (server.memory_tracking_per_slot)
            updateSlotAllocSize(c->db, getKeySlot(c->argv[1]->ptr), oldsize, stringObjectAllocSize(o));
        totlen = sdslen(o->ptr);
        int64_t oldlen = totlen - append_len;
        updateKeysizesHist(c->db, getKeySlot(c->argv[1]->ptr), OBJ_STRING, oldlen, totlen);
    }
    signalModifiedKey(c,c->db,c->argv[1]);
    notifyKeyspaceEvent(NOTIFY_STRING,"append",c->argv[1],c->db->id);
    server.dirty++;

    addReplyLongLong(c,totlen);
}

void strlenCommand(client *c) {
    kvobj *kv;
    if ((kv = lookupKeyReadOrReply(c, c->argv[1], shared.czero)) == NULL ||
        checkType(c, kv, OBJ_STRING)) return;
    addReplyLongLong(c,stringObjectLen(kv));
}

/* LCS key1 key2 [LEN] [IDX] [MINMATCHLEN <len>] [WITHMATCHLEN] */
void lcsCommand(client *c) {
    uint32_t i, j;
    long long minmatchlen = 0;
    sds a = NULL, b = NULL;
    int getlen = 0, getidx = 0, withmatchlen = 0;

    kvobj *obja = lookupKeyRead(c->db, c->argv[1]);
    kvobj *objb = lookupKeyRead(c->db, c->argv[2]);
    if ((obja && obja->type != OBJ_STRING) ||
        (objb && objb->type != OBJ_STRING))
    {
        addReplyError(c,
            "The specified keys must contain string values");
        /* Don't cleanup the objects, we need to do that
         * only after calling getDecodedObject(). */
        obja = NULL;
        objb = NULL;
        goto cleanup;
    }
    obja = obja ? getDecodedObject(obja) : createStringObject("",0);
    objb = objb ? getDecodedObject(objb) : createStringObject("",0);
    a = obja->ptr;
    b = objb->ptr;

    for (j = 3; j < (uint32_t)c->argc; j++) {
        char *opt = c->argv[j]->ptr;
        int moreargs = (c->argc-1) - j;

        if (!strcasecmp(opt,"IDX")) {
            getidx = 1;
        } else if (!strcasecmp(opt,"LEN")) {
            getlen = 1;
        } else if (!strcasecmp(opt,"WITHMATCHLEN")) {
            withmatchlen = 1;
        } else if (!strcasecmp(opt,"MINMATCHLEN") && moreargs) {
            if (getLongLongFromObjectOrReply(c,c->argv[j+1],&minmatchlen,NULL)
                != C_OK) goto cleanup;
            if (minmatchlen < 0) minmatchlen = 0;
            j++;
        } else {
            addReplyErrorObject(c,shared.syntaxerr);
            goto cleanup;
        }
    }

    /* Complain if the user passed ambiguous parameters. */
    if (getlen && getidx) {
        addReplyError(c,
            "If you want both the length and indexes, please just use IDX.");
        goto cleanup;
    }

    /* Detect string truncation or later overflows. */
    if (sdslen(a) >= UINT32_MAX-1 || sdslen(b) >= UINT32_MAX-1) {
        addReplyError(c, "String too long for LCS");
        goto cleanup;
    }

    /* Compute the LCS using the vanilla dynamic programming technique of
     * building a table of LCS(x,y) substrings. */
    uint32_t alen = sdslen(a);
    uint32_t blen = sdslen(b);

    /* Setup an uint32_t array to store at LCS[i,j] the length of the
     * LCS A0..i-1, B0..j-1. Note that we have a linear array here, so
     * we index it as LCS[j+(blen+1)*i] */
    #define LCS(A,B) lcs[(B)+((A)*(blen+1))]

    /* Try to allocate the LCS table, and abort on overflow or insufficient memory. */
    unsigned long long lcssize = (unsigned long long)(alen+1)*(blen+1); /* Can't overflow due to the size limits above. */
    unsigned long long lcsalloc = lcssize * sizeof(uint32_t);
    uint32_t *lcs = NULL;
    if (lcsalloc < SIZE_MAX && lcsalloc / lcssize == sizeof(uint32_t)) {
        if (lcsalloc > (size_t)server.proto_max_bulk_len) {
            addReplyError(c, "Insufficient memory, transient memory for LCS exceeds proto-max-bulk-len");
            goto cleanup;
        }
        lcs = ztrymalloc(lcsalloc);
    }
    if (!lcs) {
        addReplyError(c, "Insufficient memory, failed allocating transient memory for LCS");
        goto cleanup;
    }

    /* Start building the LCS table. */
    for (uint32_t i = 0; i <= alen; i++) {
        for (uint32_t j = 0; j <= blen; j++) {
            if (i == 0 || j == 0) {
                /* If one substring has length of zero, the
                 * LCS length is zero. */
                LCS(i,j) = 0;
            } else if (a[i-1] == b[j-1]) {
                /* The len LCS (and the LCS itself) of two
                 * sequences with the same final character, is the
                 * LCS of the two sequences without the last char
                 * plus that last char. */
                LCS(i,j) = LCS(i-1,j-1)+1;
            } else {
                /* If the last character is different, take the longest
                 * between the LCS of the first string and the second
                 * minus the last char, and the reverse. */
                uint32_t lcs1 = LCS(i-1,j);
                uint32_t lcs2 = LCS(i,j-1);
                LCS(i,j) = lcs1 > lcs2 ? lcs1 : lcs2;
            }
        }
    }

    /* Store the actual LCS string in "result" if needed. We create
     * it backward, but the length is already known, we store it into idx. */
    uint32_t idx = LCS(alen,blen);
    sds result = NULL;        /* Resulting LCS string. */
    void *arraylenptr = NULL; /* Deferred length of the array for IDX. */
    uint32_t arange_start = alen, /* alen signals that values are not set. */
             arange_end = 0,
             brange_start = 0,
             brange_end = 0;

    /* Do we need to compute the actual LCS string? Allocate it in that case. */
    int computelcs = getidx || !getlen;
    if (computelcs) result = sdsnewlen(SDS_NOINIT,idx);

    /* Start with a deferred array if we have to emit the ranges. */
    uint32_t arraylen = 0;  /* Number of ranges emitted in the array. */
    if (getidx) {
        addReplyMapLen(c,2);
        addReplyBulkCString(c,"matches");
        arraylenptr = addReplyDeferredLen(c);
    }

    i = alen, j = blen;
    while (computelcs && i > 0 && j > 0) {
        int emit_range = 0;
        if (a[i-1] == b[j-1]) {
            /* If there is a match, store the character and reduce
             * the indexes to look for a new match. */
            result[idx-1] = a[i-1];

            /* Track the current range. */
            if (arange_start == alen) {
                arange_start = i-1;
                arange_end = i-1;
                brange_start = j-1;
                brange_end = j-1;
            } else {
                /* Let's see if we can extend the range backward since
                 * it is contiguous. */
                if (arange_start == i && brange_start == j) {
                    arange_start--;
                    brange_start--;
                } else {
                    emit_range = 1;
                }
            }
            /* Emit the range if we matched with the first byte of
             * one of the two strings. We'll exit the loop ASAP. */
            if (arange_start == 0 || brange_start == 0) emit_range = 1;
            idx--; i--; j--;
        } else {
            /* Otherwise reduce i and j depending on the largest
             * LCS between, to understand what direction we need to go. */
            uint32_t lcs1 = LCS(i-1,j);
            uint32_t lcs2 = LCS(i,j-1);
            if (lcs1 > lcs2)
                i--;
            else
                j--;
            if (arange_start != alen) emit_range = 1;
        }

        /* Emit the current range if needed. */
        uint32_t match_len = arange_end - arange_start + 1;
        if (emit_range) {
            if (minmatchlen == 0 || match_len >= minmatchlen) {
                if (arraylenptr) {
                    addReplyArrayLen(c,2+withmatchlen);
                    addReplyArrayLen(c,2);
                    addReplyLongLong(c,arange_start);
                    addReplyLongLong(c,arange_end);
                    addReplyArrayLen(c,2);
                    addReplyLongLong(c,brange_start);
                    addReplyLongLong(c,brange_end);
                    if (withmatchlen) addReplyLongLong(c,match_len);
                    arraylen++;
                }
            }
            arange_start = alen; /* Restart at the next match. */
        }
    }

    /* Signal modified key, increment dirty, ... */

    /* Reply depending on the given options. */
    if (arraylenptr) {
        addReplyBulkCString(c,"len");
        addReplyLongLong(c,LCS(alen,blen));
        setDeferredArrayLen(c,arraylenptr,arraylen);
    } else if (getlen) {
        addReplyLongLong(c,LCS(alen,blen));
    } else {
        addReplyBulkSds(c,result);
        result = NULL;
    }

    /* Cleanup. */
    sdsfree(result);
    zfree(lcs);

cleanup:
    if (obja) decrRefCount(obja);
    if (objb) decrRefCount(objb);
    return;
}

/* Validate that a digest string has the correct length (DIGEST_HEX_LENGTH characters).
 * Note: This only validates length, not whether characters are valid hex digits.
 * Invalid hex characters will simply fail to match during comparison.
 * Returns C_OK if length is correct, C_ERR otherwise. */
int validateHexDigest(client *c, const sds digest) {
    size_t len = sdslen(digest);
    if (len != DIGEST_HEX_LENGTH) {
        addReplyErrorFormat(c, "must be exactly %d hexadecimal characters", DIGEST_HEX_LENGTH);
        return C_ERR;
    }
    return C_OK;
}

/* Return the xxh3 hash of a string object as a hex string stored in an sds.
 * The user is responsible for freeing the sds. */
sds stringDigest(robj *o) {
    serverAssert(o && o->type == OBJ_STRING);

    XXH64_hash_t hash = 0;
    if (sdsEncodedObject(o)) {
        hash = XXH3_64bits(o->ptr, sdslen(o->ptr));
    } else if (o->encoding == OBJ_ENCODING_INT) {
        char buf[LONG_STR_SIZE];
        size_t len = ll2string(buf,sizeof(buf),(long)o->ptr);
        hash = XXH3_64bits(buf, len);
    } else {
        serverPanic("Wrong obj->encoding stringDigest()");
    }

    sds hexhash = sdsempty();
    hexhash = sdscatprintf(hexhash, "%0" STRINGIFY(DIGEST_HEX_LENGTH) PRIx64, hash);
    return hexhash;
}

/* DIGEST key
 *
 * Return digest of the key's value computed via XXH3 hash. The key must be a
 * STRING object. */
void digestCommand(client *c) {
    kvobj *o;

    if ((o = lookupKeyReadOrReply(c, c->argv[1], shared.null[c->resp])) == NULL)
        return;

    if (checkType(c,o,OBJ_STRING))
        return;

    addReplyBulkSds(c, stringDigest(o));
}

