package stats

import "time"

// Server is the latest server statistics: named's process, memory, cache
// and sockets, and the host's memory and load. It is sampled with the
// counters, once a minute.
type Server struct {
	At         time.Time `json:"at"`
	Version    string    `json:"version,omitempty"`
	BootTime   string    `json:"boot_time,omitempty"`
	ConfigTime string    `json:"config_time,omitempty"`
	// From /proc (0 when named's process isn't visible).
	PID        int     `json:"pid,omitempty"`
	RSS        int64   `json:"rss,omitempty"` // resident memory, bytes
	Threads    int64   `json:"threads,omitempty"`
	CPUPercent float64 `json:"cpu_percent"`           // of one CPU, over the last minute
	CPUSeconds float64 `json:"cpu_seconds,omitempty"` // user + system time since named started
	// From the statistics channel.
	MemInUse           int64 `json:"mem_in_use"` // named's own count of the memory it uses
	CacheRRsets        int64 `json:"cache_rrsets"`
	CacheMem           int64 `json:"cache_mem"`
	SocketsUDP         int64 `json:"sockets_udp"`
	SocketsTCP         int64 `json:"sockets_tcp"`
	RecursionHighwater int64 `json:"recursion_highwater"` // most recursive clients at once since named started
	TCPHighwater       int64 `json:"tcp_highwater"`
	Host               *Host `json:"host"`
}

// Gauge keys: each is stored as two counters, "g:KEY" (the sum of the
// minute samples) and "gn:KEY" (their number), so hours and days add up
// like counters and a bucket's value is their average (see Timeline).
const (
	GaugeRSS      = "named:rss"
	GaugeMem      = "named:mem"
	GaugeCPU      = "named:cpu" // tenths of a percent of one CPU
	GaugeCacheMem = "cache:mem"
	GaugeCacheRRs = "cache:rrsets"
	GaugeHostMem  = "host:mem-used"
	GaugeHostLoad = "host:load" // the 1-minute load average, times 100
)

// gauge records a sample of a gauge for a minute (none when minute < 0).
func (c *Collector) gauge(minute int64, key string, v int64) {
	if minute < 0 {
		return
	}
	c.count(minute, "g:"+key, v)
	c.count(minute, "gn:"+key, 1)
}

// sampleServer records the gauges for a minute and keeps the latest
// values (minute -1: only those). snap is nil when named's statistics
// channel didn't answer.
// Called with c.mu held.
func (c *Collector) sampleServer(minute int64, now time.Time, snap *Snapshot) {
	srv := &Server{At: now, Host: readHost()}
	if c.proc == nil || c.proc.PID == 0 {
		c.proc = &namedProc{PID: findNamed(c.opts.MainConfig)}
	}
	p, ok := readNamedProc(c.proc.PID, now)
	if !ok {
		// named restarted with a new PID: look again next minute.
		c.proc = nil
	} else {
		srv.PID, srv.RSS, srv.Threads = p.PID, p.RSS, p.Threads
		srv.CPUSeconds = float64(p.CPU) / clockTicks
		if prev := c.proc; prev.At.Before(now) && !prev.At.IsZero() && p.CPU >= prev.CPU {
			// Tenths of a percent of one CPU: ticks / clockTicks is CPU seconds.
			permille := (p.CPU - prev.CPU) * 1000 / clockTicks / max(int64(now.Sub(prev.At)/time.Second), 1)
			srv.CPUPercent = float64(permille) / 10
			c.gauge(minute, GaugeCPU, permille)
		}
		c.proc = p
		c.gauge(minute, GaugeRSS, p.RSS)
	}
	if h := srv.Host; h.MemTotal > 0 {
		c.gauge(minute, GaugeHostMem, h.MemTotal-h.MemAvailable)
	}
	if h := srv.Host; len(h.Load) > 0 {
		c.gauge(minute, GaugeHostLoad, int64(h.Load[0]*100))
	}
	if snap != nil && snap.Gauges != nil {
		g := snap.Gauges
		srv.Version, srv.BootTime, srv.ConfigTime = snap.Version, snap.BootTime, snap.ConfigTime
		srv.MemInUse, srv.CacheRRsets, srv.CacheMem = g["named:mem"], g["cache:rrsets"], g["cache:mem"]
		srv.SocketsUDP, srv.SocketsTCP = g["sockets:udp"], g["sockets:tcp"]
		srv.RecursionHighwater, srv.TCPHighwater = g["named:recursion-highwater"], g["named:tcp-highwater"]
		c.gauge(minute, GaugeMem, srv.MemInUse)
		c.gauge(minute, GaugeCacheMem, srv.CacheMem)
		c.gauge(minute, GaugeCacheRRs, srv.CacheRRsets)
	}
	c.server = srv
}

// Server returns the latest server statistics (nil before the first
// minute).
func (c *Collector) Server() *Server {
	c.mu.Lock()
	defer c.mu.Unlock()
	if c.server == nil {
		return nil
	}
	s := *c.server
	return &s
}

// Disk is the space on a file system Jarl and named use.
type Disk struct {
	Path  string   `json:"path"`  // the first of the directories on it
	Holds []string `json:"holds"` // what is on it: zone files, logs, ...
	Total int64    `json:"total"`
	Free  int64    `json:"free"` // available to unprivileged users
}