/*
 * Copyright (c) 2019 TAOS Data, Inc. <jhtao@taosdata.com>
 *
 * This program is free software: you can use, redistribute, and/or modify
 * it under the terms of the GNU Affero General Public License, version 3
 * or later ("AGPL"), as published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.
 *
 * You should have received a copy of the GNU Affero General Public License
 * along with this program. If not, see <http://www.gnu.org/licenses/>.
 */

#include "tcache.h"
#include "hash.h"
#include "hashfunc.h"

#include "tlog.h"
#include "ttime.h"
#include "ttimer.h"
#include "tutil.h"

static FORCE_INLINE void __cache_wr_lock(SCacheObj *pCacheObj) {
#if defined(LINUX)
  pthread_rwlock_wrlock(&pCacheObj->lock);
#else
  pthread_mutex_lock(&pCacheObj->lock);
#endif
}

static FORCE_INLINE void __cache_rd_lock(SCacheObj *pCacheObj) {
#if defined(LINUX)
  pthread_rwlock_rdlock(&pCacheObj->lock);
#else
  pthread_mutex_lock(&pCacheObj->lock);
#endif
}

static FORCE_INLINE void __cache_unlock(SCacheObj *pCacheObj) {
#if defined(LINUX)
  pthread_rwlock_unlock(&pCacheObj->lock);
#else
  pthread_mutex_unlock(&pCacheObj->lock);
#endif
}

static FORCE_INLINE int32_t __cache_lock_init(SCacheObj *pCacheObj) {
#if defined(LINUX)
  return pthread_rwlock_init(&pCacheObj->lock, NULL);
#else
  return pthread_mutex_init(&pCacheObj->lock, NULL);
#endif
}

static FORCE_INLINE void __cache_lock_destroy(SCacheObj *pCacheObj) {
#if defined(LINUX)
  pthread_rwlock_destroy(&pCacheObj->lock);
#else
  pthread_mutex_destroy(&pCacheObj->lock);
#endif
}

static FORCE_INLINE void taosFreeNode(void *data) {
  SCacheDataNode *pNode = *(SCacheDataNode **)data;
  free(pNode);
}

/**
 * @param key      key of object for hash, usually a null-terminated string
 * @param keyLen   length of key
 * @param pData    actually data. required a consecutive memory block, no pointer is allowed
 *                 in pData. Pointer copy causes memory access error.
 * @param size     size of block
 * @param lifespan total survial expiredTime from now
 * @return         SCacheDataNode
 */
static SCacheDataNode *taosCreateHashNode(const char *key, size_t keyLen, const char *pData, size_t size,
                                          uint64_t duration) {
  size_t totalSize = size + sizeof(SCacheDataNode) + keyLen;
  
  SCacheDataNode *pNewNode = calloc(1, totalSize);
  if (pNewNode == NULL) {
    pError("failed to allocate memory, reason:%s", strerror(errno));
    return NULL;
  }
  
  memcpy(pNewNode->data, pData, size);
  
  pNewNode->key = (char *)pNewNode + sizeof(SCacheDataNode) + size;
  pNewNode->keySize = keyLen;
  
  memcpy(pNewNode->key, key, keyLen);
  
  pNewNode->addedTime = (uint64_t)taosGetTimestampMs();
  pNewNode->expiredTime = pNewNode->addedTime + duration;
  
  pNewNode->signature = (uint64_t)pNewNode;
  pNewNode->size = (uint32_t)totalSize;
  
  return pNewNode;
}

/**
 * addedTime object node into trash, and this object is closed for referencing if it is addedTime to trash
 * It will be removed until the pNode->refCount == 0
 * @param pCacheObj    Cache object
 * @param pNode   Cache slot object
 */
static void taosAddToTrash(SCacheObj *pCacheObj, SCacheDataNode *pNode) {
  if (pNode->inTrash) { /* node is already in trash */
    return;
  }
  
  STrashElem *pElem = calloc(1, sizeof(STrashElem));
  pElem->pData = pNode;
  
  pElem->next = pCacheObj->pTrash;
  if (pCacheObj->pTrash) {
    pCacheObj->pTrash->prev = pElem;
  }
  
  pElem->prev = NULL;
  pCacheObj->pTrash = pElem;
  
  pNode->inTrash = true;
  pCacheObj->numOfElemsInTrash++;
  
  pTrace("key:%s %p move to trash, numOfElem in trash:%d", pNode->key, pNode, pCacheObj->numOfElemsInTrash);
}

static void taosRemoveFromTrash(SCacheObj *pCacheObj, STrashElem *pElem) {
  if (pElem->pData->signature != (uint64_t)pElem->pData) {
    pError("key:sig:%d %p data has been released, ignore", pElem->pData->signature, pElem->pData);
    return;
  }
  
  pCacheObj->numOfElemsInTrash--;
  if (pElem->prev) {
    pElem->prev->next = pElem->next;
  } else { /* pnode is the header, update header */
    pCacheObj->pTrash = pElem->next;
  }
  
  if (pElem->next) {
    pElem->next->prev = pElem->prev;
  }
  
  pElem->pData->signature = 0;
  free(pElem->pData);
  free(pElem);
}
/**
 * remove nodes in trash with refCount == 0 in cache
 * @param pNode
 * @param pCacheObj
 * @param force   force model, if true, remove data in trash without check refcount.
 *                may cause corruption. So, forece model only applys before cache is closed
 */
static void taosTrashEmpty(SCacheObj *pCacheObj, bool force) {
  __cache_wr_lock(pCacheObj);
  
  if (pCacheObj->numOfElemsInTrash == 0) {
    if (pCacheObj->pTrash != NULL) {
      pError("key:inconsistency data in cache, numOfElem in trash:%d", pCacheObj->numOfElemsInTrash);
    }
    pCacheObj->pTrash = NULL;
    
    __cache_unlock(pCacheObj);
    return;
  }
  
  STrashElem *pElem = pCacheObj->pTrash;
  
  while (pElem) {
    T_REF_VAL_CHECK(pElem->pData);
    if (pElem->next == pElem) {
      pElem->next = NULL;
    }
    
    if (force || (T_REF_VAL_GET(pElem->pData) == 0)) {
      pTrace("key:%s %p removed from trash. numOfElem in trash:%d", pElem->pData->key, pElem->pData,
             pCacheObj->numOfElemsInTrash - 1);
      STrashElem *p = pElem;
      
      pElem = pElem->next;
      taosRemoveFromTrash(pCacheObj, p);
    } else {
      pElem = pElem->next;
    }
  }
  
  assert(pCacheObj->numOfElemsInTrash >= 0);
  __cache_unlock(pCacheObj);
}

/**
 * release node
 * @param pCacheObj      cache object
 * @param pNode     data node
 */
static FORCE_INLINE void taosCacheReleaseNode(SCacheObj *pCacheObj, SCacheDataNode *pNode) {
  if (pNode->signature != (uint64_t)pNode) {
    pError("key:%s, %p data is invalid, or has been released", pNode->key, pNode);
    return;
  }
  
  int32_t size = pNode->size;
  taosHashRemove(pCacheObj->pHashTable, pNode->key, pNode->keySize);
  
  pTrace("key:%s is removed from cache,total:%d,size:%ldbytes", pNode->key, pCacheObj->totalSize, size);
  free(pNode);
}

/**
 * move the old node into trash
 * @param pCacheObj
 * @param pNode
 */
static FORCE_INLINE void taosCacheMoveToTrash(SCacheObj *pCacheObj, SCacheDataNode *pNode) {
  taosHashRemove(pCacheObj->pHashTable, pNode->key, pNode->keySize);
  taosAddToTrash(pCacheObj, pNode);
}

/**
 * update data in cache
 * @param pCacheObj
 * @param pNode
 * @param key
 * @param keyLen
 * @param pData
 * @param dataSize
 * @return
 */
static SCacheDataNode *taosUpdateCacheImpl(SCacheObj *pCacheObj, SCacheDataNode *pNode, const char *key, int32_t keyLen,
                                           const void *pData, uint32_t dataSize, uint64_t duration) {
  SCacheDataNode *pNewNode = NULL;
  
  // only a node is not referenced by any other object, in-place update it
  if (T_REF_VAL_GET(pNode) == 0) {
    size_t newSize = sizeof(SCacheDataNode) + dataSize + keyLen;
    
    pNewNode = (SCacheDataNode *)realloc(pNode, newSize);
    if (pNewNode == NULL) {
      return NULL;
    }
    
    pNewNode->signature = (uint64_t)pNewNode;
    memcpy(pNewNode->data, pData, dataSize);
    
    pNewNode->key = (char *)pNewNode + sizeof(SCacheDataNode) + dataSize;
    pNewNode->keySize = keyLen;
    memcpy(pNewNode->key, key, keyLen);
    
    // update the timestamp information for updated key/value
    pNewNode->addedTime = taosGetTimestampMs();
    pNewNode->expiredTime = pNewNode->addedTime + duration;
    
    T_REF_INC(pNewNode);
    
    // the address of this node may be changed, so the prev and next element should update the corresponding pointer
    taosHashPut(pCacheObj->pHashTable, key, keyLen, &pNewNode, sizeof(void *));
  } else {
    taosCacheMoveToTrash(pCacheObj, pNode);
    
    pNewNode = taosCreateHashNode(key, keyLen, pData, dataSize, duration);
    if (pNewNode == NULL) {
      return NULL;
    }
    
    T_REF_INC(pNewNode);
    
    // addedTime new element to hashtable
    taosHashPut(pCacheObj->pHashTable, key, keyLen, &pNewNode, sizeof(void *));
  }
  
  return pNewNode;
}

/**
 * addedTime data into hash table
 * @param key
 * @param pData
 * @param size
 * @param pCacheObj
 * @param keyLen
 * @param pNode
 * @return
 */
static FORCE_INLINE SCacheDataNode *taosAddToCacheImpl(SCacheObj *pCacheObj, const char *key, size_t keyLen, const void *pData,
                                                       size_t dataSize, uint64_t duration) {
  SCacheDataNode *pNode = taosCreateHashNode(key, keyLen, pData, dataSize, duration);
  if (pNode == NULL) {
    return NULL;
  }
  
  T_REF_INC(pNode);
  taosHashPut(pCacheObj->pHashTable, key, keyLen, &pNode, sizeof(void *));
  return pNode;
}

static void doCleanupDataCache(SCacheObj *pCacheObj) {
  __cache_wr_lock(pCacheObj);
  
  if (taosHashGetSize(pCacheObj->pHashTable) > 0) {
    taosHashCleanup(pCacheObj->pHashTable);
  }
  
  __cache_unlock(pCacheObj);
  
  taosTrashEmpty(pCacheObj, true);
  __cache_lock_destroy(pCacheObj);
  
  memset(pCacheObj, 0, sizeof(SCacheObj));
  free(pCacheObj);
}

/**
 * refresh cache to remove data in both hash list and trash, if any nodes' refcount == 0, every pCacheObj->refreshTime
 * @param handle   Cache object handle
 */
static void taosCacheRefresh(void *handle, void *tmrId) {
  SCacheObj *pCacheObj = (SCacheObj *)handle;
  
  if (pCacheObj == NULL || taosHashGetSize(pCacheObj->pHashTable) == 0) {
    pTrace("object is destroyed. no refresh retry");
    return;
  }
  
  if (pCacheObj->deleting == 1) {
    doCleanupDataCache(pCacheObj);
    return;
  }
  
  uint64_t expiredTime = taosGetTimestampMs();
  pCacheObj->statistics.refreshCount++;
  
  SHashMutableIterator *pIter = taosHashCreateIter(pCacheObj->pHashTable);
  
  __cache_wr_lock(pCacheObj);
  while (taosHashIterNext(pIter)) {
    if (pCacheObj->deleting == 1) {
      taosHashDestroyIter(pIter);
      break;
    }
    
    SCacheDataNode *pNode = *(SCacheDataNode **)taosHashIterGet(pIter);
    if (pNode->expiredTime <= expiredTime && T_REF_VAL_GET(pNode) <= 0) {
      taosCacheReleaseNode(pCacheObj, pNode);
    }
  }
  
  __cache_unlock(pCacheObj);
  
  taosHashDestroyIter(pIter);
  
  if (pCacheObj->deleting == 1) {  // clean up resources and abort
    doCleanupDataCache(pCacheObj);
  } else {
    taosTrashEmpty(pCacheObj, false);
    taosTmrReset(taosCacheRefresh, pCacheObj->refreshTime, pCacheObj, pCacheObj->tmrCtrl, &pCacheObj->pTimer);
  }
}

SCacheObj *taosCacheInit(void *tmrCtrl, int64_t refreshTime) {
  if (tmrCtrl == NULL || refreshTime <= 0) {
    return NULL;
  }
  
  SCacheObj *pCacheObj = (SCacheObj *)calloc(1, sizeof(SCacheObj));
  if (pCacheObj == NULL) {
    pError("failed to allocate memory, reason:%s", strerror(errno));
    return NULL;
  }
  
  pCacheObj->pHashTable = taosHashInit(1024, taosGetDefaultHashFunction(TSDB_DATA_TYPE_BINARY), false);
  if (pCacheObj->pHashTable == NULL) {
    free(pCacheObj);
    pError("failed to allocate memory, reason:%s", strerror(errno));
    return NULL;
  }
  
  // set free cache node callback function for hash table
  taosHashSetFreecb(pCacheObj->pHashTable, taosFreeNode);
  
  pCacheObj->refreshTime = refreshTime * 1000;
  pCacheObj->tmrCtrl = tmrCtrl;
  
  taosTmrReset(taosCacheRefresh, pCacheObj->refreshTime, pCacheObj, pCacheObj->tmrCtrl, &pCacheObj->pTimer);
  
  if (__cache_lock_init(pCacheObj) != 0) {
    taosTmrStopA(&pCacheObj->pTimer);
    taosHashCleanup(pCacheObj->pHashTable);
    free(pCacheObj);
    
    pError("failed to init lock, reason:%s", strerror(errno));
    return NULL;
  }
  
  return pCacheObj;
}

void *taosCachePut(SCacheObj *pCacheObj, const char *key, const void *pData, size_t dataSize, int duration) {
  SCacheDataNode *pNode;
  
  if (pCacheObj == NULL || pCacheObj->pHashTable == NULL) {
    return NULL;
  }
  
  size_t keyLen = strlen(key);
  
  __cache_wr_lock(pCacheObj);
  SCacheDataNode **pt = (SCacheDataNode **)taosHashGet(pCacheObj->pHashTable, key, keyLen);
  SCacheDataNode * pOld = (pt != NULL) ? (*pt) : NULL;
  
  if (pOld == NULL) {  // do addedTime to cache
    pNode = taosAddToCacheImpl(pCacheObj, key, keyLen, pData, dataSize, duration * 1000L);
    if (NULL != pNode) {
      pCacheObj->totalSize += pNode->size;
      
      pTrace("key:%s %p added into cache, added:%" PRIu64 ", expire:%" PRIu64 ", total:%d, size:%" PRId64 " bytes",
             key, pNode, pNode->addedTime, pNode->expiredTime, pCacheObj->totalSize, dataSize);
    }
  } else {  // old data exists, update the node
    pNode = taosUpdateCacheImpl(pCacheObj, pOld, key, keyLen, pData, dataSize, duration * 1000L);
    pTrace("key:%s %p exist in cache, updated", key, pNode);
  }
  
  __cache_unlock(pCacheObj);
  
  return (pNode != NULL) ? pNode->data : NULL;
}

void *taosCacheAcquireByName(SCacheObj *pCacheObj, const char *key) {
  if (pCacheObj == NULL || taosHashGetSize(pCacheObj->pHashTable) == 0) {
    return NULL;
  }
  
  uint32_t keyLen = (uint32_t)strlen(key);
  
  __cache_rd_lock(pCacheObj);
  
  SCacheDataNode **ptNode = (SCacheDataNode **)taosHashGet(pCacheObj->pHashTable, key, keyLen);
  if (ptNode != NULL) {
    T_REF_INC(*ptNode);
  }
  
  __cache_unlock(pCacheObj);
  
  if (ptNode != NULL) {
    atomic_add_fetch_32(&pCacheObj->statistics.hitCount, 1);
    pTrace("key:%s is retrieved from cache, %p refcnt:%d", key, (*ptNode), T_REF_VAL_GET(*ptNode));
  } else {
    atomic_add_fetch_32(&pCacheObj->statistics.missCount, 1);
    pTrace("key:%s not in cache, retrieved failed", key);
  }
  
  atomic_add_fetch_32(&pCacheObj->statistics.totalAccess, 1);
  return (ptNode != NULL) ? (*ptNode)->data : NULL;
}

void *taosCacheAcquireByData(SCacheObj *pCacheObj, void *data) {
  if (pCacheObj == NULL || data == NULL) return NULL;
  
  size_t          offset = offsetof(SCacheDataNode, data);
  SCacheDataNode *ptNode = (SCacheDataNode *)((char *)data - offset);
  
  if (ptNode->signature != (uint64_t)ptNode) {
    pError("key: %p the data from cache is invalid", ptNode);
    return NULL;
  }
  
  int32_t ref = T_REF_INC(ptNode);
  pTrace("%p add data ref in cache, refcnt:%d", ptNode, ref)
  
  // the data if referenced by at least one object, so the reference count must be greater than the value of 2.
  assert(ref >= 2);
  return data;
}

void *taosCacheTransfer(SCacheObj *pCacheObj, void **data) {
  if (pCacheObj == NULL || data == NULL) return NULL;
  
  size_t          offset = offsetof(SCacheDataNode, data);
  SCacheDataNode *ptNode = (SCacheDataNode *)((char *)(*data) - offset);
  
  if (ptNode->signature != (uint64_t)ptNode) {
    pError("key: %p the data from cache is invalid", ptNode);
    return NULL;
  }
  
  assert(T_REF_VAL_GET(ptNode) >= 1);
  
  char *d = *data;
  
  // clear its reference to old area
  *data = NULL;
  
  return d;
}

void taosCacheRelease(SCacheObj *pCacheObj, void **data, bool _remove) {
  if (pCacheObj == NULL || (*data) == NULL || (taosHashGetSize(pCacheObj->pHashTable) + pCacheObj->numOfElemsInTrash == 0)) {
    return;
  }
  
  size_t offset = offsetof(SCacheDataNode, data);
  
  SCacheDataNode *pNode = (SCacheDataNode *)((char *)(*data) - offset);
  
  if (pNode->signature != (uint64_t)pNode) {
    pError("key: %p release invalid cache data", pNode);
    return;
  }
  
  *data = NULL;
  int16_t ref = T_REF_DEC(pNode);
  pTrace("%p is released, refcnt:%d", pNode, ref);
  
  if (_remove) {
    __cache_wr_lock(pCacheObj);
    // pNode may be released immediately by other thread after the reference count of pNode is set to 0,
    // So we need to lock it in the first place.
    taosCacheMoveToTrash(pCacheObj, pNode);
    __cache_unlock(pCacheObj);
  }
}

void taosCacheEmpty(SCacheObj *pCacheObj) {
  SHashMutableIterator *pIter = taosHashCreateIter(pCacheObj->pHashTable);
  
  __cache_wr_lock(pCacheObj);
  while (taosHashIterNext(pIter)) {
    if (pCacheObj->deleting == 1) {
      taosHashDestroyIter(pIter);
      break;
    }
    
    SCacheDataNode *pNode = *(SCacheDataNode **)taosHashIterGet(pIter);
    taosCacheMoveToTrash(pCacheObj, pNode);
  }
  __cache_unlock(pCacheObj);
  
  taosHashDestroyIter(pIter);
  taosTrashEmpty(pCacheObj, false);
}

void taosCacheCleanup(SCacheObj *pCacheObj) {
  if (pCacheObj == NULL) {
    return;
  }
  
  pCacheObj->deleting = 1;
}
