package api

import (
	"context"
	"strings"
	"sync"
	"time"

	"hamlab/internal/sensors"
	"hamlab/internal/storage"
)

// statusSensors is the sensors.Provider for what isn't a /proc number: failed services,
// pending updates, pool health, drive health. Each source costs an exec or several, so
// they are read in the background on their own clocks and served from memory; every
// sensor's t says how old its reading really is.
type statusSensors struct {
	s  *Server
	mu sync.RWMutex
	by map[string][]sensors.Sensor // source → its sensors
}

const (
	servicesEvery = 30 * time.Second
	updatesEvery  = 5 * time.Minute
	zfsEvery      = time.Minute
	smartEvery    = 10 * time.Minute // storage.Manager caches SMART that long anyway, and never wakes a sleeping disk
)

func newStatusSensors(s *Server) *statusSensors {
	p := &statusSensors{s: s, by: map[string][]sensors.Sensor{}}
	go p.loop("services", servicesEvery, p.services)
	go p.loop("updates", updatesEvery, p.updates)
	go p.loop("zfs", zfsEvery, p.zfs)
	go p.loop("smart", smartEvery, p.smart)
	return p
}

func (p *statusSensors) loop(name string, every time.Duration, read func(context.Context, int64) []sensors.Sensor) {
	for {
		ctx, cancel := context.WithTimeout(context.Background(), 2*time.Minute)
		got := read(ctx, time.Now().UnixMilli())
		cancel()
		p.mu.Lock()
		p.by[name] = got
		p.mu.Unlock()
		time.Sleep(every)
	}
}

func (p *statusSensors) Sensors() []sensors.Sensor {
	p.mu.RLock()
	defer p.mu.RUnlock()
	var out []sensors.Sensor
	for _, v := range p.by {
		out = append(out, v...)
	}
	return out
}

func (p *statusSensors) services(ctx context.Context, t int64) []sensors.Sensor {
	units, err := p.s.svc.List(ctx)
	if err != nil {
		return nil
	}
	var failed, running float64
	var names []string
	for _, u := range units {
		if u.Failed {
			failed++
			names = append(names, u.Name)
		}
		if u.Sub == "running" {
			running++
		}
	}
	return []sensors.Sensor{
		{ID: "services.failed", Name: "Failed services", Kind: "count", Value: failed, T: t, Warn: sensors.F(1)},
		{ID: "services.failed_names", Name: "Failed services", Kind: "state", Value: strings.Join(names, ", "), T: t},
		{ID: "services.running", Name: "Running services", Kind: "count", Value: running, T: t},
	}
}

func (p *statusSensors) updates(ctx context.Context, t int64) []sensors.Sensor {
	st := p.s.updates.Status(ctx)
	if st.Manager == "" {
		return nil
	}
	return []sensors.Sensor{
		{ID: "updates.pending", Name: "Pending updates", Kind: "count", Value: float64(len(st.Packages)), T: t, Labels: map[string]string{"manager": st.Manager}},
		{ID: "updates.security", Name: "Pending security updates", Kind: "count", Value: float64(st.SecurityCount), T: t, Warn: sensors.F(1)},
		{ID: "updates.reboot_required", Name: "Reboot required", Kind: "state", Value: st.RebootNeeded, T: t},
	}
}

func (p *statusSensors) zfs(ctx context.Context, t int64) []sensors.Sensor {
	z := p.s.storage.ZFS(ctx)
	var out []sensors.Sensor
	for _, pool := range z.Pools {
		id, l := "zfs."+sensors.Seg(pool.Name), map[string]string{"pool": pool.Name}
		out = append(out,
			sensors.Sensor{ID: id + ".health", Name: pool.Name + " health", Kind: "state", Value: pool.Health, T: t, Labels: l},
			sensors.Sensor{ID: id + ".healthy", Name: pool.Name + " healthy", Kind: "state", Value: pool.Health == "ONLINE", T: t, Labels: l},
			sensors.Sensor{ID: id + ".size", Name: pool.Name + " size", Kind: "bytes", Unit: "B", Value: float64(pool.Size), T: t, Labels: l},
			sensors.Sensor{ID: id + ".used", Name: pool.Name + " used", Kind: "bytes", Unit: "B", Value: float64(pool.Alloc), T: t, Min: sensors.F(0), Max: sensors.F(float64(pool.Size)), Labels: l},
			sensors.Sensor{ID: id + ".used_pct", Name: pool.Name + " used", Kind: "usage", Unit: "%", Value: float64(pool.Cap), T: t, Min: sensors.F(0), Max: sensors.F(100), Labels: l},
			sensors.Sensor{ID: id + ".frag", Name: pool.Name + " fragmentation", Kind: "fragmentation", Unit: "%", Value: float64(pool.Frag), T: t, Min: sensors.F(0), Max: sensors.F(100), Labels: l},
		)
	}
	return out
}

func (p *statusSensors) smart(ctx context.Context, t int64) []sensors.Sensor {
	devs, err := storage.Devices(ctx)
	if err != nil {
		return nil
	}
	var out []sensors.Sensor
	for _, d := range devs {
		sm := p.s.storage.Smart(ctx, d.Name, false)
		if sm.Passed == nil || sm.Standby || sm.Error != "" {
			continue // no verdict to report: no smartctl, asleep, or not a SMART device
		}
		id, l := "smart."+sensors.Seg(d.Name), map[string]string{"device": d.Name, "model": d.Model}
		out = append(out,
			sensors.Sensor{ID: id + ".passed", Name: d.Name + " health", Kind: "state", Value: *sm.Passed, T: sm.FetchedAt, Labels: l},
			sensors.Sensor{ID: id + ".warnings", Name: d.Name + " warnings", Kind: "count", Value: float64(len(sm.Warnings)), T: sm.FetchedAt, Warn: sensors.F(1), Labels: l},
		)
		if sm.PowerOnHours > 0 {
			out = append(out, sensors.Sensor{ID: id + ".power_on", Name: d.Name + " powered on", Kind: "duration", Unit: "s", Value: float64(sm.PowerOnHours) * 3600, T: sm.FetchedAt, Labels: l})
		}
		if sm.NVMe != nil {
			out = append(out, sensors.Sensor{ID: id + ".wear", Name: d.Name + " endurance used", Kind: "usage", Unit: "%", Value: float64(sm.NVMe.PercentageUsed), T: sm.FetchedAt, Min: sensors.F(0), Max: sensors.F(100), Labels: l})
		}
	}
	return out
}