/*
 * Copyright (c) 2019 TAOS Data, Inc. <cli@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 TDENGINE_RAFT_SYNC_H
#define TDENGINE_RAFT_SYNC_H

#ifdef __cplusplus
extern "C" {
#endif

#include <stdint.h>
#include "taosdef.h"
#include "wal.h"

typedef uint32_t SyncNodeId;
typedef int32_t SyncGroupId;
typedef int64_t   SyncIndex;
typedef uint64_t SSyncTerm;

typedef enum {
  TAOS_SYNC_ROLE_FOLLOWER  = 0,
  TAOS_SYNC_ROLE_CANDIDATE = 1,
  TAOS_SYNC_ROLE_LEADER  = 2,
} ESyncRole;

typedef struct {
  void* data;
  size_t len;
} SSyncBuffer;

typedef struct {
  SyncNodeId  nodeId;    // node ID assigned by TDengine
  uint16_t  nodePort;  // node sync Port
  char      nodeFqdn[TSDB_FQDN_LEN]; // node FQDN  
} SNodeInfo;

typedef struct {
  int selfIndex;
  int nNode;
  SNodeInfo*  nodeInfo;
} SSyncCluster;

typedef struct {
  int32_t  selfIndex;
  int nNode;
  SyncNodeId* nodeId;
  ESyncRole*  role;
} SNodesRole;

struct SSyncFSM;
typedef struct SSyncFSM {
  void* pData;

  // apply committed log, bufs will be free by raft module
  int (*applyLog)(struct SSyncFSM *fsm, SyncIndex index, const SSyncBuffer *buf, void *pData);

  // cluster commit callback 
  int (*onClusterChanged)(struct SSyncFSM *fsm, const SSyncCluster* cluster, void *pData);

  // fsm return snapshot in ppBuf, bufs will be free by raft module
  // TODO: getSnapshot SHOULD be async?
  int (*getSnapshot)(struct SSyncFSM *fsm, SSyncBuffer **ppBuf, int* objId, bool *isLast);

  // fsm apply snapshot with pBuf data
  int (*applySnapshot)(struct SSyncFSM *fsm, SSyncBuffer *pBuf, int objId, bool isLast);

  // call when restore snapshot and log done
  int (*onRestoreDone)(struct SSyncFSM *fsm);

  void (*onRollback)(struct SSyncFSM *fsm, SyncIndex index, const SSyncBuffer *buf);

  void (*onRoleChanged)(struct SSyncFSM *fsm, const SNodesRole* pRole);

} SSyncFSM;

typedef struct SSyncServerState {
  SyncNodeId voteFor;
  SSyncTerm term;  
} SSyncServerState;

typedef struct SStateManager {
  void* pData;

  void (*saveServerState)(struct SStateManager* stateMng, const SSyncServerState* state);

  const SSyncServerState* (*readServerState)(struct SStateManager* stateMng);

  void (*saveCluster)(struct SStateManager* stateMng, const SSyncCluster* cluster);

  const SSyncCluster* (*readCluster)(struct SStateManager* stateMng);
} SStateManager;

typedef struct {
  SyncGroupId  vgId;

  twalh walHandle;

  SyncIndex snapshotIndex;    // initial version
  SSyncCluster syncCfg;    // configuration from mgmt

  SSyncFSM fsm;

  SStateManager stateManager;
} SSyncInfo;

int32_t syncInit();
void    syncCleanUp();

SyncNodeId syncStart(const SSyncInfo *);
void    syncStop(SyncNodeId);

int32_t syncPropose(SyncNodeId nodeId, SSyncBuffer buffer, void *pData, bool isWeak);

extern int32_t  raftDebugFlag;

#ifdef __cplusplus
}
#endif

#endif  // TDENGINE_RAFT_SYNC_H