// Logstream: a syslog (UDP/TCP), Docker and host system logs sink stored in VictoriaLogs,
// with a web interface to browse and search the logs.
package main

import (
	"context"
	"embed"
	"errors"
	"io/fs"
	"log"
	"net"
	"net/http"
	"os"
	"os/signal"
	"path/filepath"
	"strconv"
	"strings"
	"syscall"
	"time"
	_ "time/tzdata" // embedded time zones: TZ works without a system package
)

//go:embed web
var webFS embed.FS

type config struct {
	syslogAddr string
	httpAddr   string
	vlogsURL   string
	dataDir    string
	auth       authConfig
	rdns       bool
	dnsServer  string
	allowPurge bool
	exportMax  int
	dockerLogs bool
	dockerHost string
	backfill   time.Duration
	hostRoot   string
	hostFill   time.Duration
	kmsgDevice string
	kmsgFill   time.Duration
	auditLog   string
	auditHost  string
	auditFill  time.Duration
	filesFill  time.Duration
	batchSize  int
	queueSize  int
	flushEvery time.Duration
	spoolMax   int64
}

func getenv(key, def string) string {
	if v := os.Getenv(key); v != "" {
		return v
	}
	return def
}

func getenvInt(key string, def int) int {
	if v, err := strconv.Atoi(os.Getenv(key)); err == nil && v > 0 {
		return v
	}
	return def
}

// getenvIntZero is getenvInt that also accepts 0 (to turn a feature off).
func getenvIntZero(key string, def int) int {
	if v, err := strconv.Atoi(os.Getenv(key)); err == nil && v >= 0 {
		return v
	}
	return def
}

func getenvBool(key string, def bool) bool {
	switch strings.ToLower(os.Getenv(key)) {
	case "1", "true", "yes", "on":
		return true
	case "0", "false", "no", "off":
		return false
	}
	return def
}

func getenvDuration(key string, def time.Duration) time.Duration {
	if d, err := time.ParseDuration(os.Getenv(key)); err == nil && d >= 0 {
		return d
	}
	return def
}

func main() {
	cfg := config{
		syslogAddr: getenv("SYSLOG_ADDR", ":5514"),
		httpAddr:   getenv("HTTP_ADDR", ":8080"),
		vlogsURL:   getenv("VLOGS_URL", "http://victorialogs:9428"),
		dataDir:    getenv("DATA_DIR", "/data"),
		auth: authConfig{
			mode:         getenv("AUTH_MODE", "local"),
			user:         os.Getenv("AUTH_USER"),
			pass:         os.Getenv("AUTH_PASS"),
			viewerUser:   os.Getenv("AUTH_VIEWER_USER"),
			viewerPass:   os.Getenv("AUTH_VIEWER_PASS"),
			adminGroup:   os.Getenv("OIDC_ADMIN_GROUP"),
			groupsClaim:  os.Getenv("OIDC_GROUPS_CLAIM"),
			issuer:       os.Getenv("OIDC_ISSUER"),
			clientID:     os.Getenv("OIDC_CLIENT_ID"),
			clientSecret: os.Getenv("OIDC_CLIENT_SECRET"),
			redirectURL:  os.Getenv("OIDC_REDIRECT_URL"),
			scopes:       os.Getenv("OIDC_SCOPES"),
			// SESSION_TTL applies to both modes; OIDC_SESSION_TTL is its former name.
			sessionTTL: getenvDuration("SESSION_TTL", getenvDuration("OIDC_SESSION_TTL", 12*time.Hour)),
			loginLogo:  os.Getenv("LOGIN_LOGO"),
		},
		rdns:       getenvBool("RDNS", true),
		dnsServer:  os.Getenv("DNS_SERVER"),
		allowPurge: getenvBool("ALLOW_PURGE", false),
		exportMax:  getenvInt("EXPORT_MAX", 100000),
		dockerLogs: getenvBool("DOCKER_LOGS", false),
		dockerHost: getenv("DOCKER_HOST", "unix:///var/run/docker.sock"),
		backfill:   getenvDuration("DOCKER_BACKFILL", time.Hour),
		hostRoot:   getenv("HOST_LOGS_ROOT", "/host"),
		hostFill:   getenvDuration("HOST_LOGS_BACKFILL", time.Hour),
		kmsgDevice: getenv("DMESG_DEVICE", "/dev/kmsg"),
		kmsgFill:   getenvDuration("DMESG_BACKFILL", time.Hour),
		auditLog:   getenv("AUDIT_LOG", "/var/log/audit/audit.log"),
		auditHost:  os.Getenv("AUDIT_HOST"),
		auditFill:  getenvDuration("AUDIT_BACKFILL", time.Hour),
		filesFill:  getenvDuration("FILES_BACKFILL", time.Hour),
		batchSize:  getenvInt("BATCH_SIZE", 1000),
		queueSize:  getenvInt("QUEUE_SIZE", 100000),
		flushEvery: time.Duration(getenvInt("FLUSH_MS", 1000)) * time.Millisecond,
		spoolMax:   int64(getenvIntZero("SPOOL_MAX_MB", 1024)) << 20,
	}

	cfg.auth.dataDir = cfg.dataDir

	ctx, stop := signal.NotifyContext(context.Background(), os.Interrupt, syscall.SIGTERM)
	defer stop()

	tags, err := LoadTagStore(filepath.Join(cfg.dataDir, "tags.json"))
	if err != nil {
		log.Fatalf("tags: %v", err)
	}

	var spool *Spool
	if cfg.spoolMax > 0 {
		if spool, err = OpenSpool(filepath.Join(cfg.dataDir, "spool"), cfg.spoolMax); err != nil {
			log.Printf("disk buffer disabled: %v", err) // before the self-logs exist
			spool = nil
		}
	}
	store := NewStore(cfg.vlogsURL, cfg.batchSize, cfg.queueSize, cfg.flushEvery, spool)
	// The store stops after everything else, so the stop event is still stored.
	storeCtx, stopStore := context.WithCancel(context.Background())
	storeDone := make(chan struct{})
	go func() {
		store.Run(storeCtx)
		close(storeDone)
	}()

	hub := NewHub()
	rdns := NewReverseDNS(cfg.rdns, cfg.dnsServer)
	sink := func(e *Entry) {
		// Host sent as an IP (or no host in the header): replace it with its DNS name.
		// A new IP waits at most 300 ms, without holding up the listener; slower
		// lookups finish in the background.
		rdns.Resolve(e.Host, 300*time.Millisecond, func(name string) {
			if name != "" {
				e.HostIP, e.Host = e.Host, name
			}
			store.Enqueue(e)
			hub.Publish(e)
		})
	}
	// Internal events of LogStream (host=logstream), WARNING and above unless
	// changed in Settings > Sources.
	selfLog = NewSelfLog(cfg.dataDir, func(e *Entry) {
		store.Enqueue(e)
		hub.Publish(e)
	})
	selfCtx, stopSelf := context.WithCancel(context.Background())
	selfDone := make(chan struct{})
	go func() {
		selfLog.Run(selfCtx)
		close(selfDone)
	}()
	logEvent("main", 5, "LogStream started")

	tcpMaxConns = getenvInt("SYSLOG_TCP_MAX_CONNS", tcpMaxConns)
	if d := getenvDuration("SYSLOG_TCP_IDLE", tcpIdle); d > 0 {
		tcpIdle = d
	}
	// Listening errors (port already used…) are shown in Settings > Sources.
	syslogSrv := NewSyslogServer(ctx, cfg.syslogAddr, getenv("SYSLOG_PUBLIC_PORT", ""), cfg.dataDir, sink)

	static, err := fs.Sub(webFS, "web")
	if err != nil {
		log.Fatal(err)
	}
	mux := http.NewServeMux()
	presets := getenv("PRESETS_FILE", filepath.Join(cfg.dataDir, "presets.json"))
	api := &API{store: store, hub: hub, tags: tags, presets: presets, rdns: rdns, allowPurge: cfg.allowPurge, exportMax: cfg.exportMax, syslog: syslogSrv}
	if cfg.dockerLogs {
		dm, err := NewDockerManager(cfg.dockerHost, cfg.dataDir, cfg.backfill, sink)
		if err != nil {
			logEvent("docker", 3, "Docker logs disabled: %v", err)
		} else {
			go dm.Run(ctx)
			api.docker = dm
			log.Printf("docker logs enabled through %s", cfg.dockerHost)
		}
	}
	// System logs of the host (journal or /var/log), off until enabled in Settings > Sources.
	api.host = NewHostLogs(cfg.hostRoot, cfg.dataDir, cfg.hostFill, sink)
	go api.host.Run(ctx)
	// Kernel messages of the host (/dev/kmsg), off until enabled in Settings > Sources.
	api.dmesg = NewDmesg(cfg.kmsgDevice, cfg.dataDir, cfg.kmsgFill, sink)
	go api.dmesg.Run(ctx)
	// Linux audit log of the host (auditd), off until enabled in Settings > Sources.
	api.audit = NewAudit(cfg.auditLog, cfg.hostRoot, cfg.auditHost, cfg.dataDir, cfg.auditFill, sink)
	go api.audit.Run(ctx)
	// Log files of other programs (Traefik, nginx…) mounted in the container,
	// declared in Settings > Sources.
	api.files = NewFiles(cfg.hostRoot, cfg.dataDir, cfg.filesFill, sink)
	go api.files.Run(ctx)
	api.selfLog = selfLog
	api.Routes(mux)
	mux.Handle("GET /", http.FileServer(http.FS(static)))

	handler, err := newAuth(cfg.auth, readOnly(mux))
	if err != nil {
		log.Fatalf("auth: %v", err)
	}
	if o, ok := handler.(*OIDC); ok {
		go o.checkProvider()
	}
	_, local := handler.(*Local)
	_, oidc := handler.(*OIDC)
	authOn := local || oidc
	if !authOn {
		log.Printf("warning: no authentication (AUTH_USER is empty): anyone who can reach %s can read the logs and change the settings", cfg.httpAddr)
	}
	handler = secure(handler, contentSecurityPolicy(static), authOn)
	srv := &http.Server{
		Addr:              cfg.httpAddr,
		Handler:           handler,
		ReadHeaderTimeout: 10 * time.Second,
		IdleTimeout:       2 * time.Minute,
		// Requests inherit the global context so SSE streams end on shutdown.
		BaseContext: func(net.Listener) context.Context { return ctx },
	}
	go func() {
		<-ctx.Done()
		shutdownCtx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
		defer cancel()
		_ = srv.Shutdown(shutdownCtx)
	}()

	log.Printf("web UI on %s, syslog on %s (udp+tcp), storage %s", cfg.httpAddr, cfg.syslogAddr, cfg.vlogsURL)
	if err := srv.ListenAndServe(); err != nil && !errors.Is(err, http.ErrServerClosed) {
		log.Fatalf("http: %v", err)
	}
	logEvent("main", 5, "LogStream stopping")
	stopSelf()
	<-selfDone
	stopStore()
	<-storeDone
	log.Println("shutdown complete")
}