// 2017 Rackspace, Inc.
//
// Licensed 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 tools serves as helper or utility functions for other applications within the Migrations App.
package tools

import (
	"math/rand"
	"time"
)

// StopRetry type is a specific type to test
// against so that we can purposely break the
// retry loop external to this package.
type StopRetry struct {
	error
}

func init() {
	rand.Seed(time.Now().UnixNano())
}

// Retry function will take a
func Retry(attempts int, sleep time.Duration, f func() error) error {
	// If there was an error in the calling function, check to see if the
	// error type is of type StopRety, if so, return the error back to the client.
	// However, if we are still in the attempt loop, recursively call the Retry
	// function again.
	if err := f(); err != nil {

		if s, ok := err.(StopRetry); ok {
			// Return the original error for later checking
			return s.error
		}

		if attempts--; attempts > 0 {
			// Adjust sleep timer for a random interval to prevent too many
			// request hammering the call at once.
			//nolint:gosec
			sleep = sleep + time.Duration(rand.Int63n(int64(sleep)))/2

			// Pause and wait for the specified interval
			time.Sleep(sleep)

			// Recursively call the Retry function again.
			return Retry(attempts, 2*sleep, f)
		}

		// If we are outside of the attempt count, go ahead and return the
		// error.
		return err
	}

	// Represents a successful call.
	return nil
}