// Copyright (c) 2020, Meir Shpilraien <meir at redislabs dot com>
// SPDX-FileCopyrightText: 2024 Redict Contributors
// SPDX-FileCopyrightText: 2024 Salvatore Sanfilippo <antirez at gmail dot com>
//
// SPDX-License-Identifier: BSD-3-Clause
// SPDX-License-Identifier: LGPL-3.0-only

/* This module allow to verify 'RedictModule_AddPostNotificationJob' by registering to 3
 * key space event:
 * * STRINGS - the module register to all strings notifications and set post notification job
 *             that increase a counter indicating how many times the string key was changed.
 *             In addition, it increase another counter that counts the total changes that
 *             was made on all strings keys.
 * * EXPIRED - the module register to expired event and set post notification job that that
 *             counts the total number of expired events.
 * * EVICTED - the module register to evicted event and set post notification job that that
 *             counts the total number of evicted events.
 *
 * In addition, the module register a new command, 'postnotification.async_set', that performs a set
 * command from a background thread. This allows to check the 'RedictModule_AddPostNotificationJob' on
 * notifications that was triggered on a background thread. */

#define _BSD_SOURCE
#define _DEFAULT_SOURCE /* For usleep */

#include "redictmodule.h"
#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <pthread.h>

static void KeySpace_PostNotificationStringFreePD(void *pd) {
    RedictModule_FreeString(NULL, pd);
}

static void KeySpace_PostNotificationReadKey(RedictModuleCtx *ctx, void *pd) {
    RedictModuleCallReply* rep = RedictModule_Call(ctx, "get", "!s", pd);
    RedictModule_FreeCallReply(rep);
}

static void KeySpace_PostNotificationString(RedictModuleCtx *ctx, void *pd) {
    REDICTMODULE_NOT_USED(ctx);
    RedictModuleCallReply* rep = RedictModule_Call(ctx, "incr", "!s", pd);
    RedictModule_FreeCallReply(rep);
}

static int KeySpace_NotificationExpired(RedictModuleCtx *ctx, int type, const char *event, RedictModuleString *key){
    REDICTMODULE_NOT_USED(type);
    REDICTMODULE_NOT_USED(event);
    REDICTMODULE_NOT_USED(key);

    RedictModuleString *new_key = RedictModule_CreateString(NULL, "expired", 7);
    int res = RedictModule_AddPostNotificationJob(ctx, KeySpace_PostNotificationString, new_key, KeySpace_PostNotificationStringFreePD);
    if (res == REDICTMODULE_ERR) KeySpace_PostNotificationStringFreePD(new_key);
    return REDICTMODULE_OK;
}

static int KeySpace_NotificationEvicted(RedictModuleCtx *ctx, int type, const char *event, RedictModuleString *key){
    REDICTMODULE_NOT_USED(type);
    REDICTMODULE_NOT_USED(event);
    REDICTMODULE_NOT_USED(key);

    const char *key_str = RedictModule_StringPtrLen(key, NULL);

    if (strncmp(key_str, "evicted", 7) == 0) {
        return REDICTMODULE_OK; /* do not count the evicted key */
    }

    if (strncmp(key_str, "before_evicted", 14) == 0) {
        return REDICTMODULE_OK; /* do not count the before_evicted key */
    }

    RedictModuleString *new_key = RedictModule_CreateString(NULL, "evicted", 7);
    int res = RedictModule_AddPostNotificationJob(ctx, KeySpace_PostNotificationString, new_key, KeySpace_PostNotificationStringFreePD);
    if (res == REDICTMODULE_ERR) KeySpace_PostNotificationStringFreePD(new_key);
    return REDICTMODULE_OK;
}

static int KeySpace_NotificationString(RedictModuleCtx *ctx, int type, const char *event, RedictModuleString *key){
    REDICTMODULE_NOT_USED(ctx);
    REDICTMODULE_NOT_USED(type);
    REDICTMODULE_NOT_USED(event);

    const char *key_str = RedictModule_StringPtrLen(key, NULL);

    if (strncmp(key_str, "string_", 7) != 0) {
        return REDICTMODULE_OK;
    }

    if (strcmp(key_str, "string_total") == 0) {
        return REDICTMODULE_OK;
    }

    RedictModuleString *new_key;
    if (strncmp(key_str, "string_changed{", 15) == 0) {
        new_key = RedictModule_CreateString(NULL, "string_total", 12);
    } else {
        new_key = RedictModule_CreateStringPrintf(NULL, "string_changed{%s}", key_str);
    }

    int res = RedictModule_AddPostNotificationJob(ctx, KeySpace_PostNotificationString, new_key, KeySpace_PostNotificationStringFreePD);
    if (res == REDICTMODULE_ERR) KeySpace_PostNotificationStringFreePD(new_key);
    return REDICTMODULE_OK;
}

static int KeySpace_LazyExpireInsidePostNotificationJob(RedictModuleCtx *ctx, int type, const char *event, RedictModuleString *key){
    REDICTMODULE_NOT_USED(ctx);
    REDICTMODULE_NOT_USED(type);
    REDICTMODULE_NOT_USED(event);

    const char *key_str = RedictModule_StringPtrLen(key, NULL);

    if (strncmp(key_str, "read_", 5) != 0) {
        return REDICTMODULE_OK;
    }

    RedictModuleString *new_key = RedictModule_CreateString(NULL, key_str + 5, strlen(key_str) - 5);;
    int res = RedictModule_AddPostNotificationJob(ctx, KeySpace_PostNotificationReadKey, new_key, KeySpace_PostNotificationStringFreePD);
    if (res == REDICTMODULE_ERR) KeySpace_PostNotificationStringFreePD(new_key);
    return REDICTMODULE_OK;
}

static int KeySpace_NestedNotification(RedictModuleCtx *ctx, int type, const char *event, RedictModuleString *key){
    REDICTMODULE_NOT_USED(ctx);
    REDICTMODULE_NOT_USED(type);
    REDICTMODULE_NOT_USED(event);

    const char *key_str = RedictModule_StringPtrLen(key, NULL);

    if (strncmp(key_str, "write_sync_", 11) != 0) {
        return REDICTMODULE_OK;
    }

    /* This test was only meant to check REDICTMODULE_OPTIONS_ALLOW_NESTED_KEYSPACE_NOTIFICATIONS.
     * In general it is wrong and discourage to perform any writes inside a notification callback.  */
    RedictModuleString *new_key = RedictModule_CreateString(NULL, key_str + 11, strlen(key_str) - 11);;
    RedictModuleCallReply* rep = RedictModule_Call(ctx, "set", "!sc", new_key, "1");
    RedictModule_FreeCallReply(rep);
    RedictModule_FreeString(NULL, new_key);
    return REDICTMODULE_OK;
}

static void *KeySpace_PostNotificationsAsyncSetInner(void *arg) {
    RedictModuleBlockedClient *bc = arg;
    RedictModuleCtx *ctx = RedictModule_GetThreadSafeContext(bc);
    RedictModule_ThreadSafeContextLock(ctx);
    RedictModuleCallReply* rep = RedictModule_Call(ctx, "set", "!cc", "string_x", "1");
    RedictModule_ThreadSafeContextUnlock(ctx);
    RedictModule_ReplyWithCallReply(ctx, rep);
    RedictModule_FreeCallReply(rep);

    RedictModule_UnblockClient(bc, NULL);
    RedictModule_FreeThreadSafeContext(ctx);
    return NULL;
}

static int KeySpace_PostNotificationsAsyncSet(RedictModuleCtx *ctx, RedictModuleString **argv, int argc) {
    REDICTMODULE_NOT_USED(argv);
    if (argc != 1)
        return RedictModule_WrongArity(ctx);

    pthread_t tid;
    RedictModuleBlockedClient *bc = RedictModule_BlockClient(ctx,NULL,NULL,NULL,0);

    if (pthread_create(&tid,NULL,KeySpace_PostNotificationsAsyncSetInner,bc) != 0) {
        RedictModule_AbortBlock(bc);
        return RedictModule_ReplyWithError(ctx,"-ERR Can't start thread");
    }
    return REDICTMODULE_OK;
}

typedef struct KeySpace_EventPostNotificationCtx {
    RedictModuleString *triggered_on;
    RedictModuleString *new_key;
} KeySpace_EventPostNotificationCtx;

static void KeySpace_ServerEventPostNotificationFree(void *pd) {
    KeySpace_EventPostNotificationCtx *pn_ctx = pd;
    RedictModule_FreeString(NULL, pn_ctx->new_key);
    RedictModule_FreeString(NULL, pn_ctx->triggered_on);
    RedictModule_Free(pn_ctx);
}

static void KeySpace_ServerEventPostNotification(RedictModuleCtx *ctx, void *pd) {
    REDICTMODULE_NOT_USED(ctx);
    KeySpace_EventPostNotificationCtx *pn_ctx = pd;
    RedictModuleCallReply* rep = RedictModule_Call(ctx, "lpush", "!ss", pn_ctx->new_key, pn_ctx->triggered_on);
    RedictModule_FreeCallReply(rep);
}

static void KeySpace_ServerEventCallback(RedictModuleCtx *ctx, RedictModuleEvent eid, uint64_t subevent, void *data) {
    REDICTMODULE_NOT_USED(eid);
    REDICTMODULE_NOT_USED(data);
    if (subevent > 3) {
        RedictModule_Log(ctx, "warning", "Got an unexpected subevent '%llu'", (unsigned long long)subevent);
        return;
    }
    static const char* events[] = {
            "before_deleted",
            "before_expired",
            "before_evicted",
            "before_overwritten",
    };

    const RedictModuleString *key_name = RedictModule_GetKeyNameFromModuleKey(((RedictModuleKeyInfo*)data)->key);
    const char *key_str = RedictModule_StringPtrLen(key_name, NULL);

    for (int i = 0 ; i < 4 ; ++i) {
        const char *event = events[i];
        if (strncmp(key_str, event , strlen(event)) == 0) {
            return; /* don't log any event on our tracking keys */
        }
    }

    KeySpace_EventPostNotificationCtx *pn_ctx = RedictModule_Alloc(sizeof(*pn_ctx));
    pn_ctx->triggered_on = RedictModule_HoldString(NULL, (RedictModuleString*)key_name);
    pn_ctx->new_key = RedictModule_CreateString(NULL, events[subevent], strlen(events[subevent]));
    int res = RedictModule_AddPostNotificationJob(ctx, KeySpace_ServerEventPostNotification, pn_ctx, KeySpace_ServerEventPostNotificationFree);
    if (res == REDICTMODULE_ERR) KeySpace_ServerEventPostNotificationFree(pn_ctx);
}

/* This function must be present on each Redict module. It is used in order to
 * register the commands into the Redict server. */
int RedictModule_OnLoad(RedictModuleCtx *ctx, RedictModuleString **argv, int argc) {
    REDICTMODULE_NOT_USED(argv);
    REDICTMODULE_NOT_USED(argc);

    if (RedictModule_Init(ctx,"postnotifications",1,REDICTMODULE_APIVER_1) == REDICTMODULE_ERR){
        return REDICTMODULE_ERR;
    }

    if (!(RedictModule_GetModuleOptionsAll() & REDICTMODULE_OPTIONS_ALLOW_NESTED_KEYSPACE_NOTIFICATIONS)) {
        return REDICTMODULE_ERR;
    }

    int with_key_events = 0;
    if (argc >= 1) {
        const char *arg = RedictModule_StringPtrLen(argv[0], 0);
        if (strcmp(arg, "with_key_events") == 0) {
            with_key_events = 1;
        }
    }

    RedictModule_SetModuleOptions(ctx, REDICTMODULE_OPTIONS_ALLOW_NESTED_KEYSPACE_NOTIFICATIONS);

    if(RedictModule_SubscribeToKeyspaceEvents(ctx, REDICTMODULE_NOTIFY_STRING, KeySpace_NotificationString) != REDICTMODULE_OK){
        return REDICTMODULE_ERR;
    }

    if(RedictModule_SubscribeToKeyspaceEvents(ctx, REDICTMODULE_NOTIFY_STRING, KeySpace_LazyExpireInsidePostNotificationJob) != REDICTMODULE_OK){
        return REDICTMODULE_ERR;
    }

    if(RedictModule_SubscribeToKeyspaceEvents(ctx, REDICTMODULE_NOTIFY_STRING, KeySpace_NestedNotification) != REDICTMODULE_OK){
        return REDICTMODULE_ERR;
    }

    if(RedictModule_SubscribeToKeyspaceEvents(ctx, REDICTMODULE_NOTIFY_EXPIRED, KeySpace_NotificationExpired) != REDICTMODULE_OK){
        return REDICTMODULE_ERR;
    }

    if(RedictModule_SubscribeToKeyspaceEvents(ctx, REDICTMODULE_NOTIFY_EVICTED, KeySpace_NotificationEvicted) != REDICTMODULE_OK){
        return REDICTMODULE_ERR;
    }

    if (with_key_events) {
        if(RedictModule_SubscribeToServerEvent(ctx, RedictModuleEvent_Key, KeySpace_ServerEventCallback) != REDICTMODULE_OK){
            return REDICTMODULE_ERR;
        }
    }

    if (RedictModule_CreateCommand(ctx, "postnotification.async_set", KeySpace_PostNotificationsAsyncSet,
                                      "write", 0, 0, 0) == REDICTMODULE_ERR){
        return REDICTMODULE_ERR;
    }

    return REDICTMODULE_OK;
}

int RedictModule_OnUnload(RedictModuleCtx *ctx) {
    REDICTMODULE_NOT_USED(ctx);
    return REDICTMODULE_OK;
}