package cluster

import (
	"math"
	"sort"
	"strings"
	"time"

	"pxmon/internal/history"
)

type AvailabilityVM struct {
	Name         string  `json:"name"`
	Availability float64 `json:"availability_pct"`
	Samples      int     `json:"samples"`
	Running      int     `json:"running_samples"`
}

type AvailabilityReport struct {
	Cluster      string           `json:"cluster"`
	Range        string           `json:"range"`
	Samples      int              `json:"samples"`
	UpSamples    int              `json:"up_samples"`
	Availability float64          `json:"availability_pct"`
	VMs          []AvailabilityVM `json:"vms,omitempty"`
}

func (s *Service) AvailabilityReport(selector string, since time.Time, vmFilter string) (AvailabilityReport, error) {
	c, err := s.Get(selector)
	if err != nil {
		return AvailabilityReport{}, err
	}
	store := history.NewAvailabilityStore(s.DataDir())
	snaps, err := store.Load(c.ID, since)
	if err != nil {
		return AvailabilityReport{}, err
	}
	rep := AvailabilityReport{Cluster: c.Name, Samples: len(snaps)}
	if len(snaps) == 0 {
		return rep, nil
	}
	vmFilter = strings.TrimSpace(vmFilter)
	totalUp := 0
	type acc struct{ samples, running int }
	vmap := map[string]*acc{}
	for _, snap := range snaps {
		if snap.ClusterUp {
			totalUp++
		}
		for vm, st := range snap.VMStates {
			if vmFilter != "" && !strings.EqualFold(vmFilter, vm) {
				continue
			}
			a := vmap[vm]
			if a == nil {
				a = &acc{}
				vmap[vm] = a
			}
			a.samples++
			if strings.EqualFold(strings.TrimSpace(st), "running") {
				a.running++
			}
		}
	}
	rep.UpSamples = totalUp
	rep.Availability = 100 * float64(totalUp) / float64(len(snaps))
	for vm, a := range vmap {
		if a.samples == 0 {
			continue
		}
		rep.VMs = append(rep.VMs, AvailabilityVM{
			Name:         vm,
			Samples:      a.samples,
			Running:      a.running,
			Availability: 100 * float64(a.running) / float64(a.samples),
		})
	}
	sort.Slice(rep.VMs, func(i, j int) bool { return rep.VMs[i].Name < rep.VMs[j].Name })
	return rep, nil
}

type CapacityForecastItem struct {
	Mount         string  `json:"mount"`
	UsedPct       float64 `json:"used_pct"`
	SlopeBytesSec float64 `json:"slope_bytes_per_sec"`
	DaysTo90      float64 `json:"days_to_90_pct"`
	DaysTo95      float64 `json:"days_to_95_pct"`
}

type CapacityForecastReport struct {
	Cluster string                 `json:"cluster"`
	Samples int                    `json:"samples"`
	Items   []CapacityForecastItem `json:"items,omitempty"`
}

func (s *Service) CapacityForecast(selector string, since time.Time) (CapacityForecastReport, error) {
	c, err := s.Get(selector)
	if err != nil {
		return CapacityForecastReport{}, err
	}
	store := history.NewCapacityStore(s.DataDir())
	snaps, err := store.Load(c.ID, since)
	if err != nil {
		return CapacityForecastReport{}, err
	}
	rep := CapacityForecastReport{Cluster: c.Name, Samples: len(snaps)}
	if len(snaps) < 2 {
		return rep, nil
	}
	type point struct {
		ts   time.Time
		used float64
		tot  float64
	}
	byMount := map[string][]point{}
	for _, snap := range snaps {
		for _, d := range snap.Disks {
			if d.TotalBytes == 0 {
				continue
			}
			byMount[d.Mount] = append(byMount[d.Mount], point{ts: snap.Timestamp, used: float64(d.UsedBytes), tot: float64(d.TotalBytes)})
		}
	}
	for mnt, pts := range byMount {
		if len(pts) < 2 {
			continue
		}
		sort.Slice(pts, func(i, j int) bool { return pts[i].ts.Before(pts[j].ts) })
		first := pts[0]
		last := pts[len(pts)-1]
		dt := last.ts.Sub(first.ts).Seconds()
		if dt <= 0 {
			continue
		}
		slope := (last.used - first.used) / dt
		usedPct := 100 * last.used / last.tot
		d90 := daysToTarget(last.used, last.tot*0.90, slope)
		d95 := daysToTarget(last.used, last.tot*0.95, slope)
		rep.Items = append(rep.Items, CapacityForecastItem{
			Mount:         mnt,
			UsedPct:       usedPct,
			SlopeBytesSec: slope,
			DaysTo90:      d90,
			DaysTo95:      d95,
		})
	}
	sort.Slice(rep.Items, func(i, j int) bool { return rep.Items[i].UsedPct > rep.Items[j].UsedPct })
	return rep, nil
}

func daysToTarget(current, target, slope float64) float64 {
	if target <= current {
		return 0
	}
	if slope <= 0 {
		return math.Inf(1)
	}
	return (target - current) / slope / 86400
}