first commit

internal/rrd/rrd.go

@@ -0,0 +1,111 @@
+package rrd
+
+import (
+	"bytes"
+	"context"
+	"errors"
+	"fmt"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"strconv"
+	"strings"
+	"sync"
+	"time"
+)
+
+type Manager struct {
+	Tool     string
+	Path     string
+	GraphDir string
+	mu       sync.Mutex
+}
+
+type Range struct{ Key, Start, Title string }
+
+var Ranges = []Range{
+	{"hour", "-12h", "Ostatnie 12 godzin"},
+	{"day", "-24h", "Ostatnie 24 godziny"},
+	{"72h", "-72h", "Ostatnie 72 godziny"},
+	{"week", "-1w", "Ostatni tydzień"},
+	{"month", "-1m", "Ostatni miesiąc"},
+	{"year", "-1y", "Ostatni rok"},
+}
+
+func (m *Manager) Validate() error {
+	if _, err := exec.LookPath(m.Tool); err != nil {
+		return fmt.Errorf("rrdtool not found: %w", err)
+	}
+	if st, err := os.Stat(m.Path); err != nil || st.IsDir() {
+		return fmt.Errorf("RRD file unavailable: %s", m.Path)
+	}
+	return os.MkdirAll(m.GraphDir, 0750)
+}
+
+func (m *Manager) Update(ctx context.Context, online int) error {
+	if online < 0 {
+		return errors.New("online count cannot be negative")
+	}
+	cmd := exec.CommandContext(ctx, m.Tool, "update", m.Path, "N:"+strconv.Itoa(online))
+	var stderr bytes.Buffer
+	cmd.Stderr = &stderr
+	if err := cmd.Run(); err != nil {
+		return fmt.Errorf("rrd update: %w: %s", err, strings.TrimSpace(stderr.String()))
+	}
+	return nil
+}
+
+func (m *Manager) Last(ctx context.Context) (int, error) {
+	cmd := exec.CommandContext(ctx, m.Tool, "lastupdate", m.Path)
+	out, err := cmd.Output()
+	if err != nil {
+		return 0, err
+	}
+	lines := strings.Split(strings.TrimSpace(string(out)), "\n")
+	if len(lines) < 2 {
+		return 0, errors.New("unexpected rrd lastupdate output")
+	}
+	fields := strings.Fields(lines[len(lines)-1])
+	if len(fields) < 2 {
+		return 0, errors.New("unexpected rrd lastupdate data")
+	}
+	v := fields[len(fields)-1]
+	if v == "U" {
+		return 0, nil
+	}
+	f, err := strconv.ParseFloat(v, 64)
+	return int(f + 0.5), err
+}
+
+func (m *Manager) Graph(ctx context.Context, key string) (string, error) {
+	var rg *Range
+	for i := range Ranges {
+		if Ranges[i].Key == key {
+			rg = &Ranges[i]
+			break
+		}
+	}
+	if rg == nil {
+		return "", errors.New("unknown graph range")
+	}
+	if err := os.MkdirAll(m.GraphDir, 0750); err != nil {
+		return "", err
+	}
+	out := filepath.Join(m.GraphDir, key+".png")
+
+	m.mu.Lock()
+	defer m.mu.Unlock()
+	if st, err := os.Stat(out); err == nil && time.Since(st.ModTime()) < 55*time.Second {
+		return out, nil
+	}
+
+	def := "DEF:online=" + m.Path + ":online:LAST"
+	args := []string{"graph", out, "--imgformat", "PNG", "--start", rg.Start, "--end", "now", "--width", "1200", "--height", "320", "--lower-limit", "0", "--alt-autoscale-max", "--title", rg.Title, "--vertical-label", "użytkownicy", "--border", "0", def, "LINE2:online#2F6FED:Online", "GPRINT:online:LAST:Aktualnie\\: %4.0lf", "GPRINT:online:AVERAGE:Średnio\\: %4.0lf", "GPRINT:online:MAX:Maks.\\: %4.0lf\\n"}
+	cmd := exec.CommandContext(ctx, m.Tool, args...)
+	var stderr bytes.Buffer
+	cmd.Stderr = &stderr
+	if err := cmd.Run(); err != nil {
+		return "", fmt.Errorf("rrd graph: %w: %s", err, strings.TrimSpace(stderr.String()))
+	}
+	return out, nil
+}