// Copyright 2021, Roman Gershman.  All rights reserved.
// See LICENSE for licensing terms.
//

#include "server/generic_family.h"

extern "C" {
 #include "redis/object.h"
}

#include "base/logging.h"
#include "server/command_registry.h"
#include "server/conn_context.h"
#include "server/engine_shard_set.h"
#include "server/error.h"
#include "server/transaction.h"
#include "util/varz.h"

DEFINE_uint32(dbnum, 16, "Number of databases");

namespace dfly {
using namespace std;

namespace {

DEFINE_VARZ(VarzQps, ping_qps);

class Renamer {
 public:
  Renamer(DbIndex dind, ShardId source_id) : db_indx_(dind), src_sid_(source_id) {
  }

  OpResult<void> Find(ShardId shard_id, const ArgSlice& args);

  OpResult<void> status() const {
    return status_;
  };

  Transaction::RunnableType Finalize(bool skip_exist_dest);

 private:
  void MoveValues(EngineShard* shard, const ArgSlice& args);

  DbIndex db_indx_;
  ShardId src_sid_;

  struct FindResult {
    string_view key;
    PrimeValue val;
    uint64_t expire_ts;
    bool found = false;
  };

  FindResult src_res_, dest_res_;  // index 0 for source, 1 for destination

  OpResult<void> status_;
};

OpResult<void> Renamer::Find(ShardId shard_id, const ArgSlice& args) {
  CHECK_EQ(1u, args.size());
  FindResult* res = (shard_id == src_sid_) ? &src_res_ : &dest_res_;

  res->key = args.front();
  auto [it, exp_it] = EngineShard::tlocal()->db_slice().FindExt(db_indx_, res->key);

  res->found = IsValid(it);
  if (IsValid(it)) {
    res->val = it->second.AsRef();
    res->expire_ts = IsValid(exp_it) ? exp_it->second : 0;
  }

  return OpStatus::OK;
};

void Renamer::MoveValues(EngineShard* shard, const ArgSlice& args) {
  auto shard_id = shard->shard_id();

  // TODO: when we want to maintain heap per shard model this code will require additional
  // work
  if (shard_id == src_sid_) {  // Handle source key.
    // delete the source entry.
    auto it = shard->db_slice().FindExt(db_indx_, src_res_.key).first;
    CHECK(shard->db_slice().Del(db_indx_, it));
    return;
  }

  // Handle destination
  string_view dest_key = dest_res_.key;
  MainIterator dest_it = shard->db_slice().FindExt(db_indx_, dest_key).first;
  if (IsValid(dest_it)) {
    // we just move the source. We won't be able to do it with heap per shard model.
    dest_it->second = std::move(src_res_.val);
    shard->db_slice().Expire(db_indx_, dest_it, src_res_.expire_ts);
  } else {
    // we just add the key to destination with the source object.

    shard->db_slice().AddNew(db_indx_, dest_key, std::move(src_res_.val), src_res_.expire_ts);
  }
}

Transaction::RunnableType Renamer::Finalize(bool skip_exist_dest) {
  auto cleanup = [](Transaction* t, EngineShard* shard) { return OpStatus::OK; };

  if (!src_res_.found) {
    status_ = OpStatus::KEY_NOTFOUND;

    return cleanup;
  }

  if (dest_res_.found && skip_exist_dest) {
    status_ = OpStatus::KEY_EXISTS;

    return cleanup;
  }

  DCHECK(src_res_.val.IsRef());

  // We can not copy from the existing value and delete it at the same time.
  // TODO: if we want to allocate in shard, we must implement CompactObject::Clone.
  // For now we hack it for strings only.
  string val;
  src_res_.val.GetString(&val);
  src_res_.val.SetString(val);

  // Src key exist and we need to override the destination.
  return [this](Transaction* t, EngineShard* shard) {
    this->MoveValues(shard, t->ShardArgsInShard(shard->shard_id()));

    return OpStatus::OK;
  };
}

const char* ObjTypeName(int type) {
  switch (type) {
    case OBJ_STRING:
      return "string";
    case OBJ_LIST:
      return "list";
    case OBJ_SET:
      return "set";
    case OBJ_ZSET:
      return "zset";
    case OBJ_HASH:
      return "hash";
    case OBJ_STREAM:
      return "stream";
    default:
      LOG(ERROR) << "Unsupported type " << type;
  }
  return "invalid";
};
}  // namespace

void GenericFamily::Init(util::ProactorPool* pp) {
  ping_qps.Init(pp);
}

void GenericFamily::Shutdown() {
  ping_qps.Shutdown();
}

void GenericFamily::Del(CmdArgList args, ConnectionContext* cntx) {
  Transaction* transaction = cntx->transaction;
  VLOG(1) << "Del " << ArgS(args, 1);

  atomic_uint32_t result{0};
  auto cb = [&result](const Transaction* t, EngineShard* shard) {
    ArgSlice args = t->ShardArgsInShard(shard->shard_id());
    auto res = OpDel(OpArgs{shard, t->db_index()}, args);
    result.fetch_add(res.value_or(0), memory_order_relaxed);

    return OpStatus::OK;
  };

  OpStatus status = transaction->ScheduleSingleHop(std::move(cb));
  CHECK_EQ(OpStatus::OK, status);

  DVLOG(2) << "Del ts " << transaction->txid();

  cntx->SendLong(result.load(memory_order_release));
}

void GenericFamily::Ping(CmdArgList args, ConnectionContext* cntx) {
  if (args.size() > 2) {
    return cntx->SendError("wrong number of arguments for 'ping' command");
  }
  ping_qps.Inc();

  // We synchronously block here until the engine sends us the payload and notifies that
  // the I/O operation has been processed.
  if (args.size() == 1) {
    return cntx->SendSimpleRespString("PONG");
  } else {
    string_view arg = ArgS(args, 1);
    DVLOG(2) << "Ping " << arg;

    return cntx->SendBulkString(arg);
  }
}

void GenericFamily::Exists(CmdArgList args, ConnectionContext* cntx) {
  Transaction* transaction = cntx->transaction;
  VLOG(1) << "Exists " << ArgS(args, 1);

  atomic_uint32_t result{0};

  auto cb = [&result](Transaction* t, EngineShard* shard) {
    ArgSlice args = t->ShardArgsInShard(shard->shard_id());
    auto res = OpExists(OpArgs{shard, t->db_index()}, args);
    result.fetch_add(res.value_or(0), memory_order_relaxed);

    return OpStatus::OK;
  };

  OpStatus status = transaction->ScheduleSingleHop(std::move(cb));
  CHECK_EQ(OpStatus::OK, status);

  return cntx->SendLong(result.load(memory_order_release));
}

void GenericFamily::Expire(CmdArgList args, ConnectionContext* cntx) {
  string_view key = ArgS(args, 1);
  string_view sec = ArgS(args, 2);
  int64_t int_arg;

  if (!absl::SimpleAtoi(sec, &int_arg)) {
    return cntx->SendError(kInvalidIntErr);
  }

  int_arg = std::max(int_arg, -1L);
  ExpireParams params{.ts = int_arg};

  auto cb = [&](Transaction* t, EngineShard* shard) {
    return OpExpire(OpArgs{shard, t->db_index()}, key, params);
  };
  OpStatus status = cntx->transaction->ScheduleSingleHop(move(cb));

  cntx->SendLong(status == OpStatus::OK);
}

void GenericFamily::ExpireAt(CmdArgList args, ConnectionContext* cntx) {
  string_view key = ArgS(args, 1);
  string_view sec = ArgS(args, 2);
  int64_t int_arg;

  if (!absl::SimpleAtoi(sec, &int_arg)) {
    return cntx->SendError(kInvalidIntErr);
  }
  int_arg = std::max(int_arg, 0L);
  ExpireParams params{.ts = int_arg, .absolute = true};

  auto cb = [&](Transaction* t, EngineShard* shard) {
    return OpExpire(OpArgs{shard, t->db_index()}, key, params);
  };
  OpStatus status = cntx->transaction->ScheduleSingleHop(std::move(cb));
  cntx->SendLong(status == OpStatus::OK);
}

void GenericFamily::Rename(CmdArgList args, ConnectionContext* cntx) {
  OpResult<void> st = RenameGeneric(args, false, cntx);
  cntx->SendError(st.status());
}

void GenericFamily::Ttl(CmdArgList args, ConnectionContext* cntx) {
  TtlGeneric(args, cntx, TimeUnit::SEC);
}

void GenericFamily::Pttl(CmdArgList args, ConnectionContext* cntx) {
  TtlGeneric(args, cntx, TimeUnit::MSEC);
}

void GenericFamily::TtlGeneric(CmdArgList args, ConnectionContext* cntx, TimeUnit unit) {
  string_view key = ArgS(args, 1);

  auto cb = [&](Transaction* t, EngineShard* shard) { return OpTtl(t, shard, key); };
  OpResult<uint64_t> result = cntx->transaction->ScheduleSingleHopT(std::move(cb));

  if (result) {
    long ttl = (unit == TimeUnit::SEC) ? (result.value() + 500) / 1000 : result.value();
    cntx->SendLong(ttl);
  } else {
    switch (result.status()) {
      case OpStatus::KEY_NOTFOUND:
        cntx->SendLong(-1);
        break;
      default:
        cntx->SendLong(-2);
    }
  }
}

void GenericFamily::Select(CmdArgList args, ConnectionContext* cntx) {
  string_view key = ArgS(args, 1);
  int64_t index;
  if (!absl::SimpleAtoi(key, &index)) {
    return cntx->SendError(kInvalidDbIndErr);
  }
  if (index < 0 || index >= FLAGS_dbnum) {
    return cntx->SendError(kDbIndOutOfRangeErr);
  }
  cntx->conn_state.db_index = index;
  auto cb = [index](EngineShard* shard) {
    shard->db_slice().ActivateDb(index);
    return OpStatus::OK;
  };
  cntx->shard_set->RunBriefInParallel(std::move(cb));

  return cntx->SendOk();
}

void GenericFamily::Type(CmdArgList args, ConnectionContext* cntx) {
  std::string_view key = ArgS(args, 1);

  auto cb = [&](Transaction* t, EngineShard* shard) -> OpResult<int> {
    auto it = shard->db_slice().FindExt(t->db_index(), key).first;
    if (!it.is_done()) {
      return it->second.ObjType();
    } else {
      return OpStatus::KEY_NOTFOUND;
    }
  };
  OpResult<int> result = cntx->transaction->ScheduleSingleHopT(std::move(cb));
  if (!result) {
    cntx->SendSimpleRespString("none");
  } else {
    cntx->SendSimpleRespString(ObjTypeName(result.value()));
  }
}

OpResult<void> GenericFamily::RenameGeneric(CmdArgList args, bool skip_exist_dest,
                                            ConnectionContext* cntx) {
  string_view key[2] = {ArgS(args, 1), ArgS(args, 2)};

  Transaction* transaction = cntx->transaction;

  if (transaction->unique_shard_cnt() == 1) {
    auto cb = [&](Transaction* t, EngineShard* shard) {
      return OpRen(OpArgs{shard, t->db_index()}, key[0], key[1], skip_exist_dest);
    };
    OpResult<void> result = transaction->ScheduleSingleHopT(std::move(cb));

    return result;
  }

  transaction->Schedule();
  unsigned shard_count = transaction->shard_set()->size();
  Renamer renamer{transaction->db_index(), Shard(key[0], shard_count)};

  // Phase 1 -> Fetch  keys from both shards.
  // Phase 2 -> If everything is ok, clone the source object, delete the destination object, and
  //            set its ptr to cloned one. we also copy the expiration data of the source key.
  transaction->Execute(
      [&renamer](Transaction* t, EngineShard* shard) {
        auto args = t->ShardArgsInShard(shard->shard_id());
        return renamer.Find(shard->shard_id(), args).status();
      },
      false);

  transaction->Execute(renamer.Finalize(skip_exist_dest), true);

  return renamer.status();
}

void GenericFamily::Echo(CmdArgList args, ConnectionContext* cntx) {
  string_view key = ArgS(args, 1);
  return cntx->SendBulkString(key);
}

void GenericFamily::Scan(CmdArgList args, ConnectionContext* cntx) {
  std::string_view token = ArgS(args, 1);
  uint64_t cursor = 0;
  EngineShardSet* ess = cntx->shard_set;
  unsigned shard_count = ess->size();

  // Dash table returns a cursor with its right byte empty. We will use it
  // for encoding shard index. For now scan has a limitation of 255 shards.
  CHECK_LT(shard_count, 1024u);

  if (!absl::SimpleAtoi(token, &cursor)) {
    return cntx->SendError("invalid cursor");
  }

  ShardId sid = cursor % 1024;
  if (sid >= shard_count) {
    return cntx->SendError("invalid cursor");
  }

  cursor >>= 10;

  vector<string> keys;
  do {
    ess->Await(sid, [&] {
      OpArgs op_args{EngineShard::tlocal(), cntx->conn_state.db_index};
      OpScan(op_args, &cursor, &keys);
    });
    if (cursor == 0) {
      ++sid;
      if (unsigned(sid) == shard_count)
        break;
    }
  } while (keys.size() < 10);

  if (sid < shard_count) {
    cursor = (cursor << 10) | sid;
  } else {
    DCHECK_EQ(0u, cursor);
  }

  string res("*2\r\n$");
  string curs_str = absl::StrCat(cursor);
  absl::StrAppend(&res, curs_str.size(), "\r\n", curs_str, "\r\n*", keys.size(), "\r\n");
  for (const auto& k : keys) {
    absl::StrAppend(&res, "$", k.size(), "\r\n", k, "\r\n");
  }

  return cntx->SendRespBlob(res);
}


OpStatus GenericFamily::OpExpire(const OpArgs& op_args, string_view key,
                                 const ExpireParams& params) {
  auto& db_slice = op_args.shard->db_slice();
  auto [it, expire_it] = db_slice.FindExt(op_args.db_ind, key);
  if (!IsValid(it))
    return OpStatus::KEY_NOTFOUND;

  int64_t abs_msec = (params.unit == TimeUnit::SEC) ? params.ts * 1000 : params.ts;

  if (!params.absolute) {
    abs_msec += db_slice.Now();
  }

  if (abs_msec <= int64_t(db_slice.Now())) {
    CHECK(db_slice.Del(op_args.db_ind, it));
  } else if (IsValid(expire_it)) {
    expire_it->second = abs_msec;
  } else {
    db_slice.Expire(op_args.db_ind, it, abs_msec);
  }

  return OpStatus::OK;
}

OpResult<uint64_t> GenericFamily::OpTtl(Transaction* t, EngineShard* shard, string_view key) {
  auto& db_slice = shard->db_slice();
  auto [it, expire] = db_slice.FindExt(t->db_index(), key);
  if (!IsValid(it))
    return OpStatus::KEY_NOTFOUND;

  if (!IsValid(expire))
    return OpStatus::SKIPPED;

  int64_t ttl_ms = expire->second - db_slice.Now();
  DCHECK_GT(ttl_ms, 0);  // Otherwise FindExt would return null.
  return ttl_ms;
}

OpResult<uint32_t> GenericFamily::OpDel(const OpArgs& op_args, ArgSlice keys) {
  DVLOG(1) << "Del: " << keys[0];
  auto& db_slice = op_args.shard->db_slice();

  uint32_t res = 0;

  for (uint32_t i = 0; i < keys.size(); ++i) {
    auto fres = db_slice.FindExt(op_args.db_ind, keys[i]);
    if (!IsValid(fres.first))
      continue;
    res += int(db_slice.Del(op_args.db_ind, fres.first));
  }

  return res;
}

OpResult<uint32_t> GenericFamily::OpExists(const OpArgs& op_args, ArgSlice keys) {
  DVLOG(1) << "Exists: " << keys[0];
  auto& db_slice = op_args.shard->db_slice();
  uint32_t res = 0;

  for (uint32_t i = 0; i < keys.size(); ++i) {
    auto find_res = db_slice.FindExt(op_args.db_ind, keys[i]);
    res += IsValid(find_res.first);
  }
  return res;
}

OpResult<void> GenericFamily::OpRen(const OpArgs& op_args, string_view from,
                                    string_view to, bool skip_exists) {
  auto& db_slice = op_args.shard->db_slice();
  auto [from_it, expire_it] = db_slice.FindExt(op_args.db_ind, from);
  if (!IsValid(from_it))
    return OpStatus::KEY_NOTFOUND;

  auto [to_it, to_expire] = db_slice.FindExt(op_args.db_ind, to);
  if (IsValid(to_it)) {
    if (skip_exists)
      return OpStatus::KEY_EXISTS;
  }

  uint64_t exp_ts = IsValid(expire_it) ? expire_it->second : 0;
  if (IsValid(to_it)) {
    to_it->second = std::move(from_it->second);
    from_it->second.SetExpire(IsValid(expire_it));

    if (IsValid(to_expire)) {
      to_it->second.SetExpire(true);
      to_expire->second = exp_ts;
    } else {
      to_it->second.SetExpire(false);
      db_slice.Expire(op_args.db_ind, to_it, exp_ts);
    }
  } else {
    db_slice.AddNew(op_args.db_ind, to, std::move(from_it->second), exp_ts);
    // Need search again since the container might invalidate the iterators.
    from_it = db_slice.FindExt(op_args.db_ind, from).first;
  }
  CHECK(db_slice.Del(op_args.db_ind, from_it));
  return OpStatus::OK;
}

void GenericFamily::OpScan(const OpArgs& op_args, uint64_t* cursor, vector<string>* vec) {
  auto& db_slice = op_args.shard->db_slice();
  DCHECK(db_slice.IsDbValid(op_args.db_ind));

  unsigned cnt = 0;
  auto scan_cb = [&](MainIterator it) {
    if (it->second.HasExpire()) {
      it = db_slice.ExpireIfNeeded(op_args.db_ind, it).first;
    }
    vec->push_back(it->first.ToString());
    ++cnt;
  };

  VLOG(1) << "PrimeTable " << db_slice.shard_id() << "/" << op_args.db_ind
          << " has " << db_slice.DbSize(op_args.db_ind);

  uint64_t cur = *cursor;
  auto [prime_table, expire_table] = db_slice.GetTables(op_args.db_ind);
  do {
    cur = prime_table->Traverse(cur, scan_cb);
  } while (cur && cnt < 10);

  VLOG(1) << "OpScan " << db_slice.shard_id() << " cursor: " << cur;
  *cursor = cur;
}

using CI = CommandId;

#define HFUNC(x) SetHandler(&GenericFamily::x)

void GenericFamily::Register(CommandRegistry* registry) {
  constexpr auto kSelectOpts = CO::LOADING | CO::FAST | CO::STALE;
  *registry << CI{"DEL", CO::WRITE, -2, 1, -1, 1}.HFUNC(Del)
            << CI{"PING", CO::STALE | CO::FAST, -1, 0, 0, 0}.HFUNC(Ping)
            << CI{"ECHO", CO::READONLY | CO::FAST, 2, 0, 0, 0}.HFUNC(Echo)
            << CI{"EXISTS", CO::READONLY | CO::FAST, -2, 1, -1, 1}.HFUNC(Exists)
            << CI{"EXPIRE", CO::WRITE | CO::FAST, 3, 1, 1, 1}.HFUNC(Expire)
            << CI{"EXPIREAT", CO::WRITE | CO::FAST, 3, 1, 1, 1}.HFUNC(ExpireAt)
            << CI{"RENAME", CO::WRITE, 3, 1, 2, 1}.HFUNC(Rename)
            << CI{"SELECT", kSelectOpts, 2, 0, 0, 0}.HFUNC(Select)
            << CI{"SCAN", CO::READONLY | CO::FAST, -2, 0, 0, 0}.HFUNC(Scan)
            << CI{"TTL", CO::READONLY | CO::FAST | CO::RANDOM, 2, 1, 1, 1}.HFUNC(Ttl)
            << CI{"PTTL", CO::READONLY | CO::FAST | CO::RANDOM, 2, 1, 1, 1}.HFUNC(Pttl)
            << CI{"TYPE", CO::READONLY | CO::FAST, 2, 1, 1, 1}.HFUNC(Type);
}

}  // namespace dfly