package main

import (
	"backoff/fibonacci"
	"context"
	"flag"
	"fmt"
	"math"
	"os"
	"strconv"
	"time"
)

func FormatOutput(pause time.Duration, ns bool) string {
	switch ns {
	case true:
		return strconv.FormatInt(pause.Nanoseconds(), 10)
	default:
		return pause.String()
	}
}

func main() {
	start := time.Now()
	var (
		doPanic           bool
		doSleep           bool
		multiplier        time.Duration
		jitter            time.Duration
		iteration         int64
		nanosecondsOutput bool
	)
	flag.BoolVar(&doPanic, "panic", false, "panic instead of overflowing values (default returns the max value instead of overflowing).")
	flag.BoolVar(&doSleep, "sleep", false, "sleep for the resulting duration after calculating it. prints the run duration of the program instead of the calculated pause duration.")
	flag.DurationVar(&multiplier, "multiplier", time.Millisecond, "pause multiplier.")
	flag.DurationVar(&jitter, "jitter", 0, "jitter boundary. pause duration is randomly selected in the range of resultDuration+-jitter.")
	flag.Int64Var(&iteration, "iteration", 1, "iteration to use for calculating pause time.")
	flag.BoolVar(&nanosecondsOutput, "ns", false, "outputs int64 nanoseconds instead of string.")
	flag.Parse()

	if jitter < 0 {
		jitter = time.Duration(int(math.Abs(float64(jitter.Nanoseconds()))))
	}
	if iteration >= int64(len(fibonacci.TheFibonacciSequence)) {
		switch doPanic {
		case true:
			panic(fmt.Sprintf("error: input %d would overflow int64\n", iteration))
		default:
			maxIteration := int64(len(fibonacci.TheFibonacciSequence) - 1)
			fmt.Fprintf(os.Stderr, "iteration %d would overflow int64 - using %d\n", iteration, maxIteration)
			iteration = maxIteration
		}
	}

	backoff := &fibonacci.FibonacciBackoff{
		Iteration:       iteration,
		PauseMultiplier: multiplier,
		Jitter:          jitter,
	}

	var response string
	switch doSleep {
	case true:
		<-backoff.After(context.Background())
		response = FormatOutput(time.Since(start), nanosecondsOutput)
	default:
		response = FormatOutput(backoff.Next(), nanosecondsOutput)
	}
	fmt.Println(response)

}