/*
 * 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 2 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 Go Responsiveness. If not, see <https://www.gnu.org/licenses/>.
 */

package utilities

import (
	"context"
	"fmt"
	"math"
	"math/rand"
	"os"
	"reflect"
	"strings"
	"sync"
	"sync/atomic"
	"time"
)

// GitVersion is the Git revision hash
var GitVersion = "dev"

func Iota(low int, high int) (made []int) {
	made = make([]int, high-low)
	for counter := low; counter < high; counter++ {
		made[counter-low] = counter
	}
	return
}

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

func Conditional[T any](condition bool, t T, f T) T {
	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 MeasurementResult struct {
	Delay            time.Duration
	MeasurementCount uint16
	Err              error
}

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

var GenerateUniqueId func() uint64 = func() func() uint64 {
	var nextConnectionId uint64 = 0
	return func() uint64 {
		return atomic.AddUint64(&nextConnectionId, 1)
	}
}()

type Optional[S any] struct {
	value S
	some  bool
}

func Some[S any](value S) Optional[S] {
	return Optional[S]{value: value, some: true}
}

func None[S any]() Optional[S] {
	return Optional[S]{some: false}
}

func IsNone[S any](optional Optional[S]) bool {
	return !optional.some
}

func IsSome[S any](optional Optional[S]) bool {
	return optional.some
}

func GetSome[S any](optional Optional[S]) S {
	if !optional.some {
		panic("Attempting to access Some of a None.")
	}
	return optional.value
}

func (optional Optional[S]) String() string {
	if IsSome(optional) {
		return fmt.Sprintf("Some: %v", optional.some)
	} else {
		return "None"
	}
}

func RandBetween(max int) int {
	return rand.New(rand.NewSource(int64(time.Now().Nanosecond()))).Int() % max
}

func ChannelToSlice[S any](channel <-chan S) (slice []S) {
	slice = make([]S, 0)
	for element := range channel {
		slice = append(slice, element)
	}
	return
}

func Reverse[T any](elements []T) []T {
	result := make([]T, len(elements))
	iterator := len(elements) - 1
	for _, v := range elements {
		result[iterator] = v
		iterator--
	}
	return result
}

func Filter[S any](elements []S, filterer func(S) bool) []S {
	result := make([]S, 0)
	for _, s := range elements {
		if filterer(s) {
			result = append(result, s)
		}
	}
	return result
}

func Fmap[S any, F any](elements []S, mapper func(S) F) []F {
	result := make([]F, 0)
	for _, s := range elements {
		result = append(result, mapper(s))
	}
	return result
}

func OrTimeout(f func(), timeout time.Duration) {
	completeChannel := func() chan interface{} {
		completed := make(chan interface{})
		go func() {
			// This idea taken from https://stackoverflow.com/a/32843750.
			// Closing the channel will let the read of it proceed immediately.
			// Making that operation a defer ensures that it will happen even if
			// the function f panics during its execution.
			defer close(completed)
			f()
		}()
		return completed
	}()
	select {
	case <-completeChannel:
		break
	case <-time.After(timeout):
		break
	}
}

func FilenameAppend(filename, appendage string) string {
	pieces := strings.SplitN(filename, ".", 2)
	result := pieces[0] + appendage
	if len(pieces) > 1 {
		result = result + "." + strings.Join(pieces[1:], ".")
	}
	return result
}

func ApproximatelyEqual[T float32 | float64](truth T, maybe T, fudge T) bool {
	bTruth := float64(truth)
	bMaybe := float64(maybe)
	bFudge := float64(fudge)
	diff := math.Abs((bTruth - bMaybe))
	return diff < bFudge
}

func UserAgent() string {
	return fmt.Sprintf("goresponsiveness/%s", GitVersion)
}

func WaitWithContext(ctxt context.Context, condition *func() bool, mu *sync.Mutex, c *sync.Cond) bool {
	mu.Lock()
	for !(*condition)() && ctxt.Err() == nil {
		c.Wait()
	}
	return ctxt.Err() == nil
}

func ContextSignaler(ctxt context.Context, st time.Duration, condition *func() bool, c *sync.Cond) {
	for !(*condition)() && ctxt.Err() == nil {
		time.Sleep(st)
	}
	if ctxt.Err() != nil {
		c.Broadcast()
		return
	}
}

type Pair[T1, T2 any] struct {
	First  T1
	Second T2
}

func PerSecondToInterval(rate int64) time.Duration {
	return time.Duration(time.Second.Nanoseconds() / rate)
}

func IndentOutput(output string, depth uint, character string) string {
	finalNewline := false
	if strings.LastIndex(output, "\n") == len(output)-1 {
		finalNewline = true
		output = strings.TrimSuffix(output, "\n")
	}
	indentedOutput := strings.Join(Fmap[string](strings.SplitAfter(output, "\n"), func(line string) string {
		return strings.Repeat(character, int(depth)) + line
	}), "")
	if finalNewline {
		indentedOutput += "\n"
	}
	return indentedOutput
}