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package org.babyfish.jimmer.sql.runtime;

import org.jetbrains.annotations.NotNull;
import org.jetbrains.annotations.Nullable;

import java.util.Collection;

/**
 * Exception translator for database exception,
 * no matter it is low-level JDBC exception,
 * such as {@link java.sql.SQLException};
 * or a relatively advanced Jimmer exception,
 * such as @{@link SaveException.NotUnique}
 *
 * Example: 
{@code
 * new ExceptionTranslator() {
 *     @Override
 *     public @Nullable Exception translate(
 *             @NotNull SaveException.NotUnique exception,
 *             @NotNull Args args
 *     ) {
 *         if (exception.isMatched(BookProps.NAME, BookProps.EDITION)) {
 *             return new IllegalArgumentException(
 *                 "The book whose name is \"" +
 *                 exception.getValue(BookProps.NAME) +
 *                 "\" and edition is \"" +
 *                 exception.getValue(BookProps.EDITION) +
 *                 "\" already exists"
 *             );
 *         }
 *         return null;
 *     }
 * }
 * }
 *
 * After being translated, exceptions can
 * continue to be translated until there is no
 * matching translator. To avoid potential infinite
 * recursion problems, the same translator will
 * not be used twice.
 *
 * If the final translated exception is
 * {@link RuntimeException}, it will be thrown directly;
 * otherwise, it will be wrapped and thrown as
 * {@link ExecutionException}
 *
 * There are 3 ways to setup exception translators.
 *
 * 
 *     Add it to save command, like this {@code
 *     sqlClient.getEntities()
 *          .saveCommand(...entity...)
 *          .addExceptionTranslator(
 *              new ExceptionTranslator() {
 *                  ...
 *              }
 *          )
 *     }
This configuration has a higher priority. If the
 *     same exception type is configured twice by this method and
 *     the global configuration, the configuration of this method
 *     takes precedence.
 *     Global configuration without spring-starter, like this {@code
 *     JSqlClient sqlClient = JSqlClient
 *          .newBuilder()
 *          .addExceptionTranslator(
 *              new ExceptionTranslator() {
 *                  ...
 *              }
 *          )
 *     }
 *     Global configuration by jimmer-spring-starter,
 *     by {@code @Component} of spring framework, such as {@code
 *     @Component // Let spring know your translator
 *     public NotUniqueExceptionTranslator
 *         implements ExceptionTranslator {
 *         ...
 *     }
 *     }
 * 
 * @param  The translated exception type.
 *           Note, this generic type must be specified by any class
 *           implements this interface, otherwise, exception will be raised
 */
public interface ExceptionTranslator {

    /**
     * Translate the exception.
     *
     * If the exception is not known how to be translated,
     * return null or the original argument.
     */
    @Nullable
    default Exception translate(@NotNull E exception, @NotNull Args args) {
        return exception;
    }

    interface Args {
        JSqlClientImplementor sqlClient();
        String sql();
        ExecutionPurpose purpose();
        ExecutorContext ctx();
    }

    static ExceptionTranslator of(Collection> translators) {
        return RuntimeExceptionTranslator.of(translators);
    }
}