package tech.ydb.yoj.repository.db.internal;

import lombok.AccessLevel;
import lombok.NoArgsConstructor;
import lombok.NonNull;
import lombok.RequiredArgsConstructor;
import tech.ydb.yoj.ExperimentalApi;
import tech.ydb.yoj.InternalApi;
import tech.ydb.yoj.repository.db.IsolationLevel;
import tech.ydb.yoj.repository.db.RepositoryTransaction;
import tech.ydb.yoj.repository.db.bulk.BulkParams;
import tech.ydb.yoj.repository.db.readtable.ReadTableParams;

import javax.annotation.Nullable;

/**
 * Describes a single request to the database performed by a {@link RepositoryTransaction},
 * typically in a transaction <em>but not always</em>.
 * <p>For ease of use, requests that don't take any arguments are available as constants:
 * <ul>
 * <li>{@link Commit#INSTANCE Commit.INSTANCE - commit()}</li>
 * <li>{@link Rollback#INSTANCE Rollback.INSTANCE - rollback()}</li>
 * <li>{@link GetSession#INSTANCE GetSession.INSTANCE - getSession()}</li>
 * </ul>
 */
@InternalApi
@ExperimentalApi(issue = "https://github.com/ydb-platform/yoj-project/issues/165")
public sealed interface DbRequest permits
        DbRequest.Commit,
        DbRequest.Rollback,
        DbRequest.GetSession,
        DbRequest.DataQuery,
        DbRequest.ScanQuery,
        DbRequest.ReadTable,
        DbRequest.BulkUpsert
{
    /**
     * Returns a human-readable representation of the database request.
     */
    String toLogString();

    /**
     * Commit the transaction.
     */
    @NoArgsConstructor(access = AccessLevel.PRIVATE)
    final class Commit implements DbRequest {
        public static final Commit INSTANCE = new Commit();

        @Override
        public String toLogString() {
            return ".commit()";
        }
    }

    /**
     * Rollback the transaction.
     */
    @NoArgsConstructor(access = AccessLevel.PRIVATE)
    final class Rollback implements DbRequest {
        public static final Rollback INSTANCE = new Rollback();

        @Override
        public String toLogString() {
            return ".rollback()";
        }
    }

    /**
     * Obtain a database session (connection), most likely from a pool.
     * Not all {@link RepositoryTransaction} implementations use this request type.
     */
    @NoArgsConstructor(access = AccessLevel.PRIVATE)
    final class GetSession implements DbRequest {
        public static final GetSession INSTANCE = new GetSession();

        @Override
        public String toLogString() {
            return ".getSession()";
        }
    }

    /**
     * Execute a single statement in ordinary query mode. Consistency and allowed operations (reads and writes,
     * or only reads) depend on the transaction's isolation level.
     */
    @RequiredArgsConstructor
    final class DataQuery implements DbRequest {
        @Nullable private final String log;

        @Override
        public String toLogString() {
            return ".dataQuery()" + log;
        }
    }

    /**
     * Execute a single statement in scan query mode. Not quite a transactional action, but users may consider
     * scan query isolation to be that of the {@link IsolationLevel#SNAPSHOT_READ_ONLY} isolation level.
     */
    @RequiredArgsConstructor
    final class ScanQuery implements DbRequest {
        @Nullable private final String log;

        @Override
        public String toLogString() {
            return ".scanQuery()" + log;
        }
    }

    /**
     * Stream the whole table or a range of it (non-transactional).
     */
    @RequiredArgsConstructor
    final class ReadTable implements DbRequest {
        @NonNull private final String tableName;
        @NonNull private final ReadTableParams<?> params;

        @Override
        public String toLogString() {
            return ".readTable()" + tableName + ", " + params;
        }
    }

    /**
     * Bulk upsert data (non-transactional).
     */
    @RequiredArgsConstructor
    final class BulkUpsert implements DbRequest {
        @NonNull private final String tableName;
        private final long size;
        @NonNull private final BulkParams bulkParams;

        @Override
        public String toLogString() {
            return ".bulkUpsert()" + tableName + ", [" + size + "], " + bulkParams;
        }
    }
}