/*
 * This file is part of Go Responsiveness.
 *
 * Go Responsiveness is free software: you can redistribute it and/or modify it under
 * the terms of the GNU General Public License as published by the Free Software Foundation,
 * either version 3 of the License, or (at your option) any later version.
 * Go Responsiveness is distributed in the hope that it will be useful, but WITHOUT ANY
 * WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A
 * PARTICULAR PURPOSE. See the GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License along
 * with Foobar. If not, see <https://www.gnu.org/licenses/>.
 */

package utilities

import (
	"context"
	"io"
	"math"
	"net/http"
	"os"
	"reflect"
	"time"
)

func IsInterfaceNil(ifc interface{}) bool {
	return ifc == nil ||
		(reflect.ValueOf(ifc).Kind() == reflect.Ptr && reflect.ValueOf(ifc).IsNil())
}

func SignedPercentDifference(
	current float64,
	previous float64,
) (difference float64) {
	return ((current - previous) / (float64(current+previous) / 2.0)) * float64(
		100,
	)
}

func AbsPercentDifference(
	current float64,
	previous float64,
) (difference float64) {
	return (math.Abs(current-previous) / (float64(current+previous) / 2.0)) * float64(
		100,
	)
}

func Conditional(condition bool, t string, f string) string {
	if condition {
		return t
	}
	return f
}

func ToMbps(bytes float64) float64 {
	return ToMBps(bytes) * float64(8)
}

func ToMBps(bytes float64) float64 {
	return float64(bytes) / float64(1024*1024)
}

type GetLatency struct {
	Delay          time.Duration
	RoundTripCount uint16
	Err            error
}

func CalculateSequentialRTTsTime(
	ctx context.Context,
	saturated_client *http.Client,
	new_client *http.Client,
	url string,
) chan GetLatency {
	responseChannel := make(chan GetLatency)
	go func() {
		roundTripCount := uint16(0)
		before := time.Now()
		/*
			  TODO: We are not going to measure round-trip times on the load-generating connection
				right now because we are dealing with a massive amount of buffer bloat on the
				Apple CDN.

				c_a, err := saturated_client.Get(url)
				if err != nil {
					responseChannel <- GetLatency{Delay: 0, RTTs: 0, Err: err}
					return
				}
				// TODO: Make this interruptable somehow
				// by using _ctx_.
				_, err = io.ReadAll(c_a.Body)
				if err != nil {
					responseChannel <- GetLatency{Delay: 0, RTTs: 0, Err: err}
					return
				}
				roundTripCount += 5
				c_a.Body.Close()
		*/
		c_b, err := new_client.Get(url)
		if err != nil {
			responseChannel <- GetLatency{Delay: 0, RoundTripCount: 0, Err: err}
			return
		}
		// TODO: Make this interruptable somehow by using _ctx_.
		_, err = io.ReadAll(c_b.Body)
		if err != nil {
			responseChannel <- GetLatency{Delay: 0, Err: err}
			return
		}
		c_b.Body.Close()
		// We use 1 here according to the wording in 4.2.1.
		roundTripCount += 1
		responseChannel <- GetLatency{Delay: time.Since(before), RoundTripCount: roundTripCount, Err: nil}
	}()
	return responseChannel
}

func SeekForAppend(file *os.File) (err error) {
	_, err = file.Seek(0, 2)
	return
}