/*
 * 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/>.
 */

#ifndef _TDB_PAGE_H_
#define _TDB_PAGE_H_

#ifdef __cplusplus
extern "C" {
#endif

typedef u8 SCell;

typedef struct __attribute__((__packed__)) {
  u8 cksm[4];
} SPageFtr;

typedef struct __attribute__((__packed__)) {
  u16   flags;
  u16   nCells;
  u16   cellCont;
  u16   freeCell;
  u16   nFree;
  SPgno rChild;
} SPageHdr;

struct SPage {
  pthread_spinlock_t lock;
  u8                *pData;
  int                pageSize;
  u8                 szOffset;
  // Fields below used by pager and am
  SPgid     pgid;
  SPageHdr *pPageHdr;
  SPageFtr *pPageFtr;
  u8       *aCellIdx;
  u8       *pFreeStart;
  u8       *pFreeEnd;
  int       kLen;
  int       vLen;
  int       nFree;
  int       maxLocal;
  int       minLocal;
  int       nOverflow;
  SCell    *apOvfl[4];
  int       aiOvfl[4];
  // Fields used by SPCache
  TDB_PCACHE_PAGE
};

// Macros
#define TDB_PAGE_CELL_OFFSET_AT(pPage, idx) ((pPage)->aCellIdx[idx])
#define TDB_PAGE_CELL_AT(pPage, idx)        ((pPage)->pData + TDB_PAGE_CELL_OFFSET_AT(pPage, idx))

// For page lock
#define P_LOCK_SUCC 0
#define P_LOCK_BUSY 1
#define P_LOCK_FAIL -1

#define TDB_INIT_PAGE_LOCK(pPage)    pthread_spin_init(&((pPage)->lock), 0)
#define TDB_DESTROY_PAGE_LOCK(pPage) pthread_spin_destroy(&((pPage)->lock))
#define TDB_LOCK_PAGE(pPage)         pthread_spin_lock(&((pPage)->lock))
#define TDB_UNLOCK_PAGE(pPage)       pthread_spin_unlock(&((pPage)->lock))
#define TDB_TRY_LOCK_PAGE(pPage)                       \
  ({                                                   \
    int ret;                                           \
    if (pthread_spin_trylock(&((pPage)->lock)) == 0) { \
      ret = P_LOCK_SUCC;                               \
    } else if (errno == EBUSY) {                       \
      ret = P_LOCK_BUSY;                               \
    } else {                                           \
      ret = P_LOCK_FAIL;                               \
    }                                                  \
    ret;                                               \
  })

// For page ref
#define TDB_INIT_PAGE_REF(pPage) ((pPage)->nRef = 0)
#if 0
#define TDB_REF_PAGE(pPage)     (++(pPage)->nRef)
#define TDB_UNREF_PAGE(pPage)   (--(pPage)->nRef)
#define TDB_GET_PAGE_REF(pPage) ((pPage)->nRef)
#else
#define TDB_REF_PAGE(pPage)     atomic_add_fetch_32(&((pPage)->nRef), 1)
#define TDB_UNREF_PAGE(pPage)   atomic_sub_fetch_32(&((pPage)->nRef), 1)
#define TDB_GET_PAGE_REF(pPage) atomic_load_32(&((pPage)->nRef))
#endif

// APIs
int tdbPageCreate(int pageSize, SPage **ppPage, void *(*xMalloc)(void *, size_t), void *arg);
int tdbPageDestroy(SPage *pPage, void (*xFree)(void *arg, void *ptr), void *arg);
int tdbPageInsertCell(SPage *pPage, int idx, SCell *pCell, int szCell);
int tdbPageDropCell(SPage *pPage, int idx);

#ifdef __cplusplus
}
#endif

#endif /*_TDB_PAGE_H_*/