/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements. See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership. The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License. You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied. See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */

package thrift

import (
	"errors"
)

// Generic Thrift exception
type TException interface {
	error

	TExceptionType() TExceptionType
}

// Prepends additional information to an error without losing the Thrift exception interface
func PrependError(prepend string, err error) error {
	msg := prepend + err.Error()

	if te, ok := err.(TException); ok {
		switch te.TExceptionType() {
		case TExceptionTypeTransport:
			if t, ok := err.(TTransportException); ok {
				return prependTTransportException(prepend, t)
			}
		case TExceptionTypeProtocol:
			if t, ok := err.(TProtocolException); ok {
				return prependTProtocolException(prepend, t)
			}
		case TExceptionTypeApplication:
			if t, ok := err.(TApplicationException); ok {
				return NewTApplicationException(t.TypeId(), msg)
			}
		}

		return wrappedTException{
			err:            err,
			msg:            msg,
			tExceptionType: te.TExceptionType(),
		}
	}

	return errors.New(msg)
}

// TExceptionType is an enum type to categorize different "subclasses" of TExceptions.
type TExceptionType byte

// TExceptionType values
const (
	TExceptionTypeUnknown     TExceptionType = iota
	TExceptionTypeCompiled                   // TExceptions defined in thrift files and generated by thrift compiler
	TExceptionTypeApplication                // TApplicationExceptions
	TExceptionTypeProtocol                   // TProtocolExceptions
	TExceptionTypeTransport                  // TTransportExceptions
)

// WrapTException wraps an error into TException.
//
// If err is nil or already TException, it's returned as-is.
// Otherwise it will be wraped into TException with TExceptionType() returning
// TExceptionTypeUnknown, and Unwrap() returning the original error.
func WrapTException(err error) TException {
	if err == nil {
		return nil
	}

	if te, ok := err.(TException); ok {
		return te
	}

	return wrappedTException{
		err:            err,
		msg:            err.Error(),
		tExceptionType: TExceptionTypeUnknown,
	}
}

type wrappedTException struct {
	err            error
	msg            string
	tExceptionType TExceptionType
}

func (w wrappedTException) Error() string {
	return w.msg
}

func (w wrappedTException) TExceptionType() TExceptionType {
	return w.tExceptionType
}

func (w wrappedTException) Unwrap() error {
	return w.err
}

var _ TException = wrappedTException{}