package metrics

import (
	"fmt"
	"sort"

	"github.com/owncast/owncast/core"
	"github.com/owncast/owncast/core/data"
	"github.com/owncast/owncast/models"
	"github.com/owncast/owncast/utils"
)

const (
	healthyPercentageValue = 75
	maxCPUUsage            = 90
)

// GetStreamHealthOverview will return the stream health overview.
func GetStreamHealthOverview() *models.StreamHealthOverview {
	return metrics.streamHealthOverview
}

func generateStreamHealthOverview() {
	overview := &models.StreamHealthOverview{
		Healthy:           true,
		HealthyPercentage: 100,
		Message:           "",
	}

	if cpuUseOverview := cpuUsageHealthOverview(); cpuUseOverview != nil {
		overview = cpuUseOverview
	} else if networkSpeedOverview := networkSpeedHealthOverview(); networkSpeedOverview != nil {
		overview = networkSpeedOverview
	} else if errorCountOverview := errorCountHealthOverview(); errorCountOverview != nil {
		overview = errorCountOverview
	}

	// Determine what percentage of total players are represented in our overview.
	totalPlayerCount := len(core.GetActiveViewers())
	representation := utils.IntPercentage(len(windowedBandwidths), totalPlayerCount)
	overview.Representation = representation

	metrics.streamHealthOverview = overview
}

func networkSpeedHealthOverview() *models.StreamHealthOverview {
	type singleVariant struct {
		isVideoPassthrough bool
		bitrate            int
	}

	outputVariants := data.GetStreamOutputVariants()

	streamSortVariants := make([]singleVariant, len(outputVariants))
	for i, variant := range outputVariants {
		variantSort := singleVariant{
			bitrate:            variant.VideoBitrate,
			isVideoPassthrough: variant.IsVideoPassthrough,
		}
		streamSortVariants[i] = variantSort
	}

	sort.Slice(streamSortVariants, func(i, j int) bool {
		if streamSortVariants[i].isVideoPassthrough && !streamSortVariants[j].isVideoPassthrough {
			return true
		}

		if !streamSortVariants[i].isVideoPassthrough && streamSortVariants[j].isVideoPassthrough {
			return false
		}

		return streamSortVariants[i].bitrate > streamSortVariants[j].bitrate
	})

	lowestSupportedBitrate := float64(streamSortVariants[0].bitrate)
	totalNumberOfClients := len(windowedBandwidths)

	if totalNumberOfClients == 0 {
		return nil
	}

	// Determine healthy status based on bandwidth speeds of clients.
	unhealthyClientCount := 0

	for _, speed := range windowedBandwidths {
		if int(speed) < int(lowestSupportedBitrate*1.1) {
			unhealthyClientCount++
		}
	}

	if unhealthyClientCount == 0 {
		return nil
	}

	percentUnhealthy := 100 - ((float64(unhealthyClientCount) / float64(totalNumberOfClients)) * 100)
	healthyPercentage := int(percentUnhealthy)

	return &models.StreamHealthOverview{
		Healthy:           healthyPercentage > healthyPercentageValue,
		Message:           fmt.Sprintf("%d of %d clients (%d%%) are consuming video slower than, or too close to your bitrate of %d kbps.", unhealthyClientCount, totalNumberOfClients, int((float64(unhealthyClientCount)/float64(totalNumberOfClients))*100), int(lowestSupportedBitrate)),
		HealthyPercentage: healthyPercentage,
	}
}

func cpuUsageHealthOverview() *models.StreamHealthOverview {
	if len(metrics.CPUUtilizations) < 2 {
		return nil
	}

	totalNumberOfClients := len(windowedBandwidths)

	recentCPUUses := metrics.CPUUtilizations[len(metrics.CPUUtilizations)-2:]
	values := make([]float64, len(recentCPUUses))
	for i, val := range recentCPUUses {
		values[i] = val.Value
	}
	recentCPUUse := utils.Avg(values)
	if recentCPUUse < maxCPUUsage {
		return nil
	}

	clientsWithErrors := 0
	for _, errors := range windowedErrorCounts {
		if errors > 0 {
			clientsWithErrors++
		}
	}

	healthyPercentage := int(100 - ((float64(clientsWithErrors) / float64(totalNumberOfClients)) * 100))

	return &models.StreamHealthOverview{
		Healthy:           false,
		Message:           fmt.Sprintf("The CPU usage on your server is over %d%%. This may cause video to be provided slower than necessary, causing buffering for your viewers. Consider increasing the resources available or reducing the number of output variants you made available.", maxCPUUsage),
		HealthyPercentage: healthyPercentage,
	}
}

func errorCountHealthOverview() *models.StreamHealthOverview {
	totalNumberOfClients := len(windowedBandwidths)
	if totalNumberOfClients == 0 {
		return nil
	}

	clientsWithErrors := 0
	for _, errors := range windowedErrorCounts {
		if errors > 0 {
			clientsWithErrors++
		}
	}

	if clientsWithErrors == 0 {
		return nil
	}

	healthyPercentage := 100 - utils.IntPercentage(clientsWithErrors, totalNumberOfClients)

	return &models.StreamHealthOverview{
		Healthy:           healthyPercentage > healthyPercentageValue,
		Message:           fmt.Sprintf("%d of %d clients (%d%%) are experiencing different, unspecified, playback issues.", clientsWithErrors, totalNumberOfClients, healthyPercentage),
		HealthyPercentage: healthyPercentage,
	}
}