package retryer

import (
	"errors"
	"time"
)

type RetrySignal = int

const (
	FuncFailure RetrySignal = iota
	FuncComplete
	FuncError
)

// Retry retries the provided function using exponential backoff, starting with `minDelay` between attempts, and increasing to
// `maxDelay` after each failure. Stops when the provided function returns `FuncComplete`, or `maxRetries` is reached.
func Retry(body func() (RetrySignal, error), maxRetries int, minDelay time.Duration, maxDelay time.Duration) error {
	currentDelay := minDelay
	var ticker *time.Ticker

	retries := 0
	for {
		response, err := body()
		if err != nil {
			return err
		}
		if response == FuncComplete {
			return nil
		}

		retries++
		if retries >= maxRetries {
			return errors.New("max retries exceeded")
		}

		if ticker == nil {
			ticker = time.NewTicker(currentDelay)
			defer ticker.Stop()
		} else {
			currentDelay = minDuration(currentDelay*2, maxDelay)
			ticker.Reset(currentDelay)
		}

		<-ticker.C
	}
}

func minDuration(a time.Duration, b time.Duration) time.Duration {
	if a < b {
		return a
	}
	return b
}