andreschaffer/event-sourcing-cqrs-examples

package bankservice.projection.clientaccounts;

import static java.util.Collections.emptyMap;

import com.google.common.collect.ImmutableList;
import java.math.BigDecimal;
import java.util.AbstractMap;
import java.util.List;
import java.util.Map;
import java.util.UUID;
import java.util.concurrent.ConcurrentHashMap;
import java.util.stream.Collectors;
import java.util.stream.Stream;

public class InMemoryAccountsRepository implements AccountsRepository {

  private final Map<UUID, Map<UUID, AccountProjection>> clientAccounts = new ConcurrentHashMap<>();
  private final Map<UUID, UUID> accountClientIndex = new ConcurrentHashMap<>();

  @Override
  public void save(AccountProjection accountProjection) {
    clientAccounts.merge(
        accountProjection.getClientId(),
        newAccountsMap(accountProjection),
        (oldValue, value) -> {
          oldValue.putAll(value);
          return oldValue;
        }
    );
    accountClientIndex.put(accountProjection.getAccountId(), accountProjection.getClientId());
  }

  @Override
  public void updateBalance(UUID accountId, BigDecimal balance, int version) {
    UUID clientId = accountClientIndex.get(accountId);
    clientAccounts.get(clientId).merge(
        accountId,
        new AccountProjection(accountId, clientId, balance, version),
        (oldValue, value) -> value.getVersion() > oldValue.getVersion() ? value : oldValue);
  }

  @Override
  public List<AccountProjection> getAccounts(UUID clientId) {
    Map<UUID, AccountProjection> accounts = clientAccounts.getOrDefault(clientId, emptyMap());
    return ImmutableList.copyOf(accounts.values());
  }

  private Map<UUID, AccountProjection> newAccountsMap(AccountProjection accountProjection) {
    return Stream.of(
        new AbstractMap.SimpleEntry<>(accountProjection.getAccountId(), accountProjection))
        .collect(Collectors.toMap(Map.Entry::getKey, Map.Entry::getValue));
  }
}