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package tech.ydb.core;

import java.util.Objects;
import java.util.function.Function;

import javax.annotation.Nonnull;


/**
 * @author Sergey Polovko
 * @author Alexandr Gorshenin
 * @param  type of result value
 */
public interface Result {
    @Nonnull
    Status getStatus();

    @Nonnull
    T getValue() throws UnexpectedResultException;

    @Nonnull
     Result map(Function mapper);

    default boolean isSuccess() {
        return getStatus().getCode() == StatusCode.SUCCESS;
    }

    static  Result success(V value) {
        return new Success<>(Objects.requireNonNull(value), Status.SUCCESS);
    }

    static  Result success(V value, Status status) {
        return new Success<>(Objects.requireNonNull(value), Objects.requireNonNull(status));
    }

    static  Result fail(Status status) {
        return new Fail<>(Objects.requireNonNull(status));
    }

    static  Result fail(UnexpectedResultException unexpected) {
        return new Fail<>(unexpected.getStatus());
    }

    static  Result error(String message, Throwable throwable) {
        return new Error<>(message, throwable);
    }

    /*
     * SUCCESS
     */
    final class Success implements Result {
        private final V value;
        private final Status status;

        private Success(V value, Status status) {
            assert status.getCode() == StatusCode.SUCCESS;
            this.value = value;
            this.status = status;
        }

        @Override
        public Status getStatus() {
            return status;
        }

        @Override
        public V getValue() {
            return value;
        }

        @Override
        public  Success map(Function mapper) {
            return new Success<>(mapper.apply(value), status);
        }

        @Override
        public boolean equals(Object o) {
            if (this == o) {
                return true;
            }
            if (o == null || getClass() != o.getClass()) {
                return false;
            }

            Success success = (Success) o;
            return Objects.equals(status, success.status)
                    && Objects.equals(value, success.value);
        }

        @Override
        public int hashCode() {
            return Objects.hash(status, value);
        }

        @Override
        public String toString() {
            return "Success{" + value + ", status=" + status + "}";
        }
    }

    /*
     * FAIL
     */
    final class Fail implements Result {
        private final Status status;

        private Fail(Status status) {
            assert status.getCode() != StatusCode.SUCCESS;
            this.status = status;
        }

        @Override
        @SuppressWarnings("unchecked")
        public  Fail map(Function mapper) {
            return (Fail) this;
        }

        @Override
        public Status getStatus() {
            return status;
        }

        @Override
        public V getValue() {
            throw new UnexpectedResultException("Cannot get value", status);
        }

        @Override
        public boolean equals(Object o) {
            if (this == o) {
                return true;
            }
            if (o == null || getClass() != o.getClass()) {
                return false;
            }

            Fail fail = (Fail) o;
            return Objects.equals(status, fail.status);
        }

        @Override
        public int hashCode() {
            return status.hashCode();
        }

        @Override
        public String toString() {
            return "Fail{" + status + "}";
        }
    }

    /*
     * ERROR
     */
    final class Error implements Result {
        private static final Status ERROR = Status.of(StatusCode.CLIENT_INTERNAL_ERROR, null);
        private final String message;
        private final Throwable cause;
        private final Status status;

        private Error(String message, Throwable cause) {
            this.message = message;
            this.cause = cause;
            if (cause != null && cause instanceof UnexpectedResultException) {
                this.status = ((UnexpectedResultException) cause).getStatus();
            } else {
                this.status = ERROR;
            }
        }

        @Override
        public Status getStatus() {
            return status;
        }

        @Override
        public V getValue() {
            throw new UnexpectedResultException(message, status, cause);
        }

        @Override
        @SuppressWarnings("unchecked")
        public  Error map(Function mapper) {
            return (Error) this;
        }

        @Override
        public boolean equals(Object o) {
            if (this == o) {
                return true;
            }
            if (o == null || getClass() != o.getClass()) {
                return false;
            }

            Error error = (Error) o;
            return Objects.equals(message, error.message)
                    && Objects.equals(status, error.status)
                    && Objects.equals(cause, error.cause);
        }

        @Override
        public int hashCode() {
            return Objects.hash(message, status, cause);
        }

        @Override
        public String toString() {
            return "Error{message=" + message + ", cause=" + cause + '}';
        }
    }
}