/*
 * 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/>.
 */

#define _DEFAULT_SOURCE
#include "syncCommit.h"
#include "syncIndexMgr.h"
#include "syncRaftLog.h"
#include "syncRaftStore.h"
#include "syncUtil.h"

// \* Leader i advances its commitIndex.
// \* This is done as a separate step from handling AppendEntries responses,
// \* in part to minimize atomic regions, and in part so that leaders of
// \* single-server clusters are able to mark entries committed.
// AdvanceCommitIndex(i) ==
//     /\ state[i] = Leader
//     /\ LET \* The set of servers that agree up through index.
//            Agree(index) == {i} \cup {k \in Server :
//                                          matchIndex[i][k] >= index}
//            \* The maximum indexes for which a quorum agrees
//            agreeIndexes == {index \in 1..Len(log[i]) :
//                                 Agree(index) \in Quorum}
//            \* New value for commitIndex'[i]
//            newCommitIndex ==
//               IF /\ agreeIndexes /= {}
//                  /\ log[i][Max(agreeIndexes)].term = currentTerm[i]
//               THEN
//                   Max(agreeIndexes)
//               ELSE
//                   commitIndex[i]
//        IN commitIndex' = [commitIndex EXCEPT ![i] = newCommitIndex]
//     /\ UNCHANGED <<messages, serverVars, candidateVars, leaderVars, log>>
//

bool syncAgreeIndex(SSyncNode* pSyncNode, SRaftId* pRaftId, SyncIndex index) {
  // I am leader, I agree
  if (syncUtilSameId(pRaftId, &(pSyncNode->myRaftId)) && pSyncNode->state == TAOS_SYNC_STATE_LEADER) {
    return true;
  }

  // follower agree
  SyncIndex matchIndex = syncIndexMgrGetIndex(pSyncNode->pMatchIndex, pRaftId);
  if (matchIndex >= index) {
    return true;
  }

  // not agree
  return false;
}

static inline int64_t syncNodeAbs64(int64_t a, int64_t b) {
  ASSERT(a >= 0);
  ASSERT(b >= 0);

  int64_t c = a > b ? a - b : b - a;
  return c;
}

int32_t syncNodeDynamicQuorum(const SSyncNode* pSyncNode) { return pSyncNode->quorum; }

bool syncNodeAgreedUpon(SSyncNode* pNode, SyncIndex index) {
  int            count = 0;
  SSyncIndexMgr* pMatches = pNode->pMatchIndex;
  ASSERT(pNode->replicaNum == pMatches->replicaNum);

  for (int i = 0; i < pNode->replicaNum; i++) {
    SyncIndex matchIndex = pMatches->index[i];
    if (matchIndex >= index) {
      count++;
    }
  }

  return count >= pNode->quorum;
}

bool syncAgree(SSyncNode* pNode, SyncIndex index) {
  int agreeCount = 0;
  for (int i = 0; i < pNode->replicaNum; ++i) {
    if (syncAgreeIndex(pNode, &(pNode->replicasId[i]), index)) {
      ++agreeCount;
    }
    if (agreeCount >= pNode->quorum) {
      return true;
    }
  }
  return false;
}

int64_t syncNodeUpdateCommitIndex(SSyncNode* ths, SyncIndex commitIndex) {
  SyncIndex lastVer = ths->pLogStore->syncLogLastIndex(ths->pLogStore);
  commitIndex = TMAX(commitIndex, ths->commitIndex);
  ths->commitIndex = TMIN(commitIndex, lastVer);
  ths->pLogStore->syncLogUpdateCommitIndex(ths->pLogStore, ths->commitIndex);
  return ths->commitIndex;
}

int64_t syncNodeCheckCommitIndex(SSyncNode* ths, SyncIndex indexLikely) {
  if (indexLikely > ths->commitIndex && syncNodeAgreedUpon(ths, indexLikely)) {
    SyncIndex commitIndex = indexLikely;
    syncNodeUpdateCommitIndex(ths, commitIndex);
    sTrace("vgId:%d, agreed upon. role:%d, term:%" PRId64 ", index:%" PRId64 "", ths->vgId, ths->state,
           raftStoreGetTerm(ths), commitIndex);
  }
  return ths->commitIndex;
}
