package webapp

import (
	"context"
	"crypto/sha256"
	"errors"
	"fmt"
	"log"
	"net"
	"net/http"
	"os"
	"path/filepath"
	"strconv"
	"strings"
	"sync"
	"time"

	"rocketgit.ru/rsmon/worker/internal/distworker"
)

// Phase 1 (MVP) defaults. Times match docs/distributed/worker-web-app.md
// section 5.5 (30-minute idle, 8-hour absolute).
const (
	defaultSessionIdle    = 30 * time.Minute
	defaultSessionAbs     = 8 * time.Hour
	defaultHTTPListenAddr = "0.0.0.0:27401"

	// Audit retention: 7 days per section 13.2 of the plan doc.
	defaultAuditRetention = 7 * 24 * time.Hour
	// Prune runs once per day; the timer survives a long-lived worker
	// because the store is appended to from every state-changing handler.
	defaultAuditPruneInterval = 24 * time.Hour

	// Server-read-header timeout. Keeps slowloris at bay without
	// truncating large form posts on the change-password page.
	readHeaderTimeout = 10 * time.Second

	// Cookie names. Kept short so they fit inside the browser cookie
	// per-domain limit even when the operator is running the worker
	// webapp next to other local services.
	sessionCookieName = "rsmon_wsess"
	csrfCookieName    = "rsmon_wcsrf"
)

// Config holds the runtime knobs for the local webapp server. The
// fields mirror the relevant env-var settings (with the same names)
// so cmd/rsmon-worker/main.go can build a Config from os.Environ.
//
// Phase 1 (MVP) honors WORKER_HOST, WORKER_PORT, WORKER_LOGIN,
// WORKER_PASSWORD, and the RSMON_WEBAPP_DATA_DIR knob. Basic auth
// (WORKER_LOGIN/PASSWORD) is the primary auth path now that
// deployments want the webapp reachable on non-loopback addresses;
// the per-machine bcrypt user remains the fallback for fully offline
// single-operator installs.
type Config struct {
	// Addr is the bind address for the HTTP listener. Operators
	// typically set WORKER_HOST=0.0.0.0 + WORKER_PORT to expose the
	// webapp on a public interface, with the network fronted by a
	// reverse proxy / Traefik.
	Addr string

	// DataDir is the on-disk directory the SQLite store and any other
	// state files live in. The directory is created on demand.
	DataDir string

	// SessionIdle / SessionAbs override the defaults above when set
	// to a positive value.
	SessionIdle time.Duration
	SessionAbs  time.Duration

	// StorePath is the on-disk path of the SQLite file. When empty,
	// the server derives it from DataDir + "webapp.db".
	StorePath string

	// BasicAuthLogin / BasicAuthPassword enable HTTP basic auth on
	// the webapp when both are non-empty. Both must be set; a mixed
	// state (XOR) is rejected by ValidateBasicAuth. Basic auth covers
	// the /web/api/* JSON endpoints AND the login form itself, so the
	// web UI works for an operator who only knows their credentials.
	BasicAuthLogin    string
	BasicAuthPassword string

	// ReleaseURL is the optional URL the worker polls to discover
	// the latest published version of the worker binary. When empty
	// the /updates page shows the placeholder "v1 (dev)". The URL
	// is expected to respond with a JSON body containing a
	// "tag_name" field (GitHub release JSON is the canonical
	// shape). WORKER_RELEASE_URL sets this.
	ReleaseURL string
}

// ValidateBasicAuth enforces that WORKER_LOGIN and WORKER_PASSWORD
// are both set or both empty. A mixed state is a config bug and is
// rejected so an operator notices immediately. Both empty disables
// basic auth and falls back to the local bcrypt user.
func ValidateBasicAuth(login, password string) error {
	loginSet := strings.TrimSpace(login) != ""
	passSet := password != ""
	if loginSet != passSet {
		return fmt.Errorf(
			"webapp: WORKER_LOGIN and WORKER_PASSWORD must be both set or both empty (got login=%s password=%s)",
			boolStr(loginSet), boolStr(passSet))
	}
	return nil
}

func boolStr(b bool) string {
	if b {
		return "set"
	}
	return "empty"
}

// ClusterEnabledFromEnv is a tiny helper that returns true when the
// WORKER_CLUSTER_ENABLED env var is set to a truthy value. The exact
// parsing rules match the cmd binary: only the literal string "true"
// (case-insensitive) is treated as enabled. This keeps the webapp
// package's env-handling dependency-free of the workercluster
// package.
func ClusterEnabledFromEnv(env map[string]string) bool {
	v := strings.ToLower(strings.TrimSpace(env[envClusterEnabled]))
	return v == truthyTrue || v == truthyOne || v == truthyYes
}

// Truthy literal constants hoisted to satisfy goconst. parseBool
// and ClusterEnabledFromEnv share the same vocabulary.
const (
	truthyTrue = "true"
	truthyOne  = "1"
	truthyYes  = "yes"
)

// envOr returns the env var value or fallback.
func envOr(env map[string]string, key, fallback string) string {
	if v, ok := env[key]; ok && v != "" {
		return v
	}
	return fallback
}

// ConfigFromEnv builds a Config from a process-style environment map.
// It rejects XOR WORKER_LOGIN/WORKER_PASSWORD (ValidateBasicAuth) and
// reuses distworker.HTTPConfigFromEnv so the webapp and the cmd
// binary agree on host/port/url semantics.
//
// WORKER_HOST defaults to distworker.DefaultHTTPHost (0.0.0.0) and
// WORKER_PORT to distworker.DefaultHTTPPort (27401). The previous
// Phase 1 policy of binding to loopback only was removed: production
// deployments now expose the webapp on a real interface, with TLS
// terminated by a reverse proxy.
func ConfigFromEnv(env map[string]string, defaultDataDir string) (Config, error) {
	login := strings.TrimSpace(env["WORKER_LOGIN"])
	password := env["WORKER_PASSWORD"]
	if err := ValidateBasicAuth(login, password); err != nil {
		return Config{}, err
	}
	httpCfg := distworker.HTTPConfigFromEnv()
	host := httpCfg.Host
	if raw := strings.TrimSpace(env["WORKER_HOST"]); raw != "" {
		host = raw
	}
	port := httpCfg.Port
	if raw := strings.TrimSpace(env["WORKER_PORT"]); raw != "" {
		if v, err := strconv.Atoi(raw); err == nil && v > 0 && v <= 65535 {
			port = v
		}
	}
	addr := net.JoinHostPort(host, strconv.Itoa(port))
	dataDir := envOr(env, "RSMON_WEBAPP_DATA_DIR", defaultDataDir)
	cfg := Config{
		Addr:              addr,
		DataDir:           dataDir,
		BasicAuthLogin:    login,
		BasicAuthPassword: password,
	}
	if v := env["RSMON_WEBAPP_STORE_PATH"]; v != "" {
		cfg.StorePath = v
	}
	cfg.ReleaseURL = strings.TrimSpace(env[envReleaseURL])
	return cfg, nil
}

// parseBool returns true for the strings "true", "1", "yes" (any
// case, trimmed). Anything else is false. Used for opt-in feature
// flags wired through env vars without dragging in a config-package
// dependency.
func parseBool(v string) bool {
	switch strings.ToLower(strings.TrimSpace(v)) {
	case truthyTrue, truthyOne, truthyYes:
		return true
	}
	return false
}

// ConfigFromEnvOrDefault builds a Config from the process
// environment via os.Getenv. Exposed so the cmd rsmon-worker binary
// can wire the webapp without passing an env map around.
func ConfigFromEnvOrDefault() Config {
	env := map[string]string{}
	for _, k := range []string{
		envWorkerHost, envWorkerPort, envWorkerURL, envWorkerLogin, envWorkerPassword,
		"RSMON_WEBAPP_DATA_DIR", "RSMON_WEBAPP_STORE_PATH",
		"WORKER_CLUSTER_ENABLED",
		envReleaseURL,
	} {
		if v := os.Getenv(k); v != "" {
			env[k] = v
		}
	}
	cfg, err := ConfigFromEnv(env, defaultDataDir())
	if err != nil {
		log.Printf("webapp: %v; falling back to safe defaults", err)
		cfg = Config{Addr: defaultHTTPListenAddr}
	}
	return cfg
}

// Deps are the in-process interfaces the webapp reads from the
// worker. Each field is optional; the page that needs it must
// tolerate a nil value. Splitting the deps from the runner keeps
// tests focused and lets cmd/rsmon-worker wire a thin facade.
type Deps struct {
	Runner       WorkerView
	Cluster      ClusterView // optional; nil means no cluster endpoints are registered
	Version      string
	BuildDate    string
	Commit       string
	StartedAt    time.Time
	Logger       *log.Logger
	TokenRotator func(ctx context.Context) (newToken string, err error) // optional; nil disables rotation

	// ReleaseHTTPClient is the *http.Client the /updates page uses
	// to poll Config.ReleaseURL. When nil the page falls back to a
	// 3s-timeout default client. cmd/rsmon-worker wires a shared
	// client so transport-level settings (TLS, proxy) are honored
	// without each handler opening its own connection pool.
	ReleaseHTTPClient *http.Client
}

// ClusterView is the narrow surface webapp needs from the worker
// cluster. The concrete type lives in cmd/rsmon-worker; webapp only
// depends on this interface so it can be stubbed in tests without
// pulling in the raft package or bbolt.
type ClusterView interface {
	Stats() ClusterStats
	ClusterID() string
	LocalAddr() string
}

// ClusterStats is the wire-stable view of a cluster. Field names
// mirror the JSON the GET /web/api/cluster/status endpoint returns.
//
// FSMConfigVersion / FSMOutboxLen / FSMPartition carry the FSM-side
// operator signals from plan section 6.1. The webapp's ClusterView
// adapter copies them from the workercluster ClusterStats so the JSON
// endpoint can surface the FSM state without taking a separate code
// path through the FSM type.
type ClusterStats struct {
	NodeID           string
	LocalAddr        string
	State            string
	Leader           string
	Term             uint64
	AppliedIndex     uint64
	LastIndex        uint64
	NumPeers         int
	Voters           []string
	FSMChecks        int
	FSMMembers       int
	FSMConfigVersion uint64
	FSMOutboxLen     int
	FSMPartition     string
}

// WorkerView is the surface the webapp needs from the distworker
// runner. It is a narrow interface so tests can mock it without
// touching the websocket loop or pool plumbing.
type WorkerView interface {
	HTTPConfig() distworker.HTTPConfig
	Token() string
	TokenRotatedAt() time.Time
	WorkerID() string
	RegionCode() string
	WorkerVersion() string
	WorkerCapabilities() []string
	LastHeartbeatAck() time.Time
	RecentResults(n int) []ResultRow
	RecentNotifications(n int) []NotificationRow
	// MasterStatus returns the most recent local selfcheck verdict
	// and the wall-clock time it was produced. The first return
	// value is nil when no probe has run yet. The webapp renders
	// the verdict at /api/peer/status so peer workers can join
	// the consensus (see
	// docs/distributed/worker-to-worker-raft.md).
	MasterStatus() (up *bool, observedAt time.Time)
}

// ResultRow is one row from the worker's in-memory result ring
// buffer. It is the same shape the checks page renders as a table.
type ResultRow struct {
	MonitorID  int64
	CheckID    int64
	Kind       string
	Host       string
	State      string
	DurationMs int64
	Error      string
	At         time.Time
}

// NotificationRow is one row from the worker's in-memory notification ring.
type NotificationRow struct {
	Kind    string // "email", "telegram_private", "telegram_group"
	Channel string
	Subject string
	Body    string
	OK      bool
	Error   string
	At      time.Time

	JobID      string
	Method     string
	Status     string
	DurationMs int
}

// Server is the local HTTP server for the worker webapp. It owns the
// SQLite store, the template bundle, the in-memory log buffer, and
// the inventory snapshot. A single instance is bound to a single
// Config and is safe for concurrent use after Start returns.
type Server struct {
	cfg       Config
	store     *Store
	deps      Deps
	mux       *http.ServeMux
	templates *Templates
	logBuffer *LogBuffer
	inventory *Inventory
	metrics   *Metrics
	cluster   ClusterView
	pruneStop chan struct{}
	pruneWG   sync.WaitGroup

	releasePoller *releasePoller

	// basicAuthHash is the SHA-256 hash of BasicAuthPassword (or the
	// zero value when basic auth is not configured). Computed once in
	// New so the middleware uses constant-time comparison. Login is
	// kept plaintext in cfg because the comparison happens in the
	// login form handler too.
	basicAuthHash [32]byte
	basicAuthOK   bool

	httpServer *http.Server
}

// New constructs a Server with the given config and dependencies.
// The store is opened (and the schema applied) synchronously; the
// caller must call Close to release the SQLite handle.
func New(cfg Config, deps *Deps) (*Server, error) { //nolint:gocritic // Config is widely passed by value in this package
	if cfg.Addr == "" {
		cfg.Addr = defaultHTTPListenAddr
	}
	if _, _, err := net.SplitHostPort(cfg.Addr); err != nil {
		return nil, fmt.Errorf("webapp: bind address %q: %w", cfg.Addr, err)
	}
	if cfg.SessionIdle <= 0 {
		cfg.SessionIdle = defaultSessionIdle
	}
	if cfg.SessionAbs <= 0 {
		cfg.SessionAbs = defaultSessionAbs
	}
	if cfg.DataDir == "" {
		cfg.DataDir = defaultDataDir()
	}
	if cfg.StorePath == "" {
		if err := os.MkdirAll(cfg.DataDir, 0o700); err != nil {
			return nil, fmt.Errorf("webapp: mkdir data dir: %w", err)
		}
		cfg.StorePath = filepath.Join(cfg.DataDir, "webapp.db")
	}
	store, err := OpenStore(cfg.StorePath)
	if err != nil {
		return nil, err
	}
	if deps.Logger == nil {
		deps.Logger = log.New(os.Stderr, "webapp: ", log.LstdFlags|log.Lshortfile)
	}
	if deps.StartedAt.IsZero() {
		deps.StartedAt = time.Now().UTC()
	}
	tmpl, err := loadTemplates()
	if err != nil {
		_ = store.Close()
		return nil, err
	}
	s := &Server{
		cfg:           cfg,
		store:         store,
		deps:          *deps,
		mux:           http.NewServeMux(),
		templates:     tmpl,
		logBuffer:     NewLogBuffer(5000),
		inventory:     NewInventory(store, deps.Logger),
		metrics:       NewMetrics(),
		cluster:       deps.Cluster,
		pruneStop:     make(chan struct{}),
		releasePoller: &releasePoller{},
	}
	if cfg.ReleaseURL != "" {
		s.releasePoller.setURL(cfg.ReleaseURL)
	}
	if cfg.BasicAuthLogin != "" && cfg.BasicAuthPassword != "" {
		s.basicAuthHash = sha256.Sum256([]byte(cfg.BasicAuthPassword))
		s.basicAuthOK = true
	}
	s.routes()
	s.httpServer = &http.Server{
		Addr:              cfg.Addr,
		Handler:           s.securityHeaders(s.mux),
		ReadHeaderTimeout: readHeaderTimeout,
		IdleTimeout:       2 * time.Minute,
	}
	return s, nil
}

// BasicAuthEnabled reports whether the server is configured with
// WORKER_LOGIN / WORKER_PASSWORD basic auth. Exposed for templates
// that need to vary the login form (username field + explanatory copy).
func (s *Server) BasicAuthEnabled() bool {
	return s != nil && s.basicAuthOK
}

// BasicAuthLogin returns the configured WORKER_LOGIN. Used by the
// login form so an operator with curl / scripts can copy the value
// straight out of the /settings page.
func (s *Server) BasicAuthLogin() string {
	if s == nil {
		return ""
	}
	return s.cfg.BasicAuthLogin
}

// Store returns the embedded store for tests and for the cmd
// rsmon-worker binary that needs to provision the first user.
func (s *Server) Store() *Store { return s.store }

// LogBuffer returns the in-memory worker-log ring buffer so the
// worker process can attach an slog/JSON sink.
func (s *Server) LogBuffer() *LogBuffer { return s.logBuffer }

// SetCluster attaches a cluster subsystem after construction. The
// cluster admin endpoints (/web/api/cluster/status and the test-config
// applier) are not registered until SetCluster is called. Pass nil to
// detach. Intended for cmd/rsmon-worker to wire the cluster after
// webapp.New; tests should construct a fresh Server with the cluster
// already on the Deps.
func (s *Server) SetCluster(c ClusterView) { s.cluster = c }

// Cluster returns the attached cluster subsystem (or nil).
func (s *Server) Cluster() ClusterView { return s.cluster }

// Close shuts down the HTTP listener, the prune goroutine, and the
// embedded store. Safe to call multiple times.
func (s *Server) Close(ctx context.Context) error {
	if s == nil {
		return nil
	}
	select {
	case <-s.pruneStop:
	default:
		close(s.pruneStop)
	}
	s.pruneWG.Wait()
	if s.httpServer != nil {
		shutdownCtx, cancel := context.WithTimeout(ctx, 5*time.Second)
		defer cancel()
		if err := s.httpServer.Shutdown(shutdownCtx); err != nil &&
			!errors.Is(err, http.ErrServerClosed) {
			s.deps.Logger.Printf("shutdown: %v", err)
		}
	}
	if s.store != nil {
		_ = s.store.Close()
	}
	return nil
}

// Start launches the audit-prune goroutine and binds the HTTP
// listener. Blocks until ctx is canceled or the listener errors
// out. Call Close to ensure cleanup.
func (s *Server) Start(ctx context.Context) error {
	s.pruneWG.Add(1)
	go s.pruneLoop(ctx)

	// Run ListenAndServe in a goroutine so we can race it against ctx.
	errCh := make(chan error, 1)
	go func() {
		s.deps.Logger.Printf("listening on http://%s (data dir=%s)", s.cfg.Addr, s.cfg.DataDir)
		if err := s.httpServer.ListenAndServe(); err != nil &&
			!errors.Is(err, http.ErrServerClosed) {
			errCh <- err
			return
		}
		errCh <- nil
	}()

	select {
	case <-ctx.Done():
		shutdownCtx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
		defer cancel()
		_ = s.httpServer.Shutdown(shutdownCtx)
		return nil
	case err := <-errCh:
		return err
	}
}

// Addr returns the actual bind address the server is using.
func (s *Server) Addr() string { return s.cfg.Addr }

// Handler returns the http.Handler the server registers with
// http.Server. Exposed for tests that want to wrap the mux in an
// httptest.Server so the bound port is observable. Production code
// should call ListenAndServe / Start instead.
func (s *Server) Handler() http.Handler {
	return s.securityHeaders(s.mux)
}

// SessionIdle / SessionAbs expose the configured timeouts so the
// handlers can compute the expiry without hard-coding.
func (s *Server) SessionIdle() time.Duration { return s.cfg.SessionIdle }

// SessionAbs returns the absolute session lifetime configured for
// this server. Used by handlers that need to compute the absolute
// cap of a session relative to its creation time.
func (s *Server) SessionAbs() time.Duration { return s.cfg.SessionAbs }

// ProvisionFirstRunIfNeeded mints a fresh first-run password and
// seeds the user row if no user exists yet. Prints the plaintext
// once via the supplied logger so the operator can read it from the
// worker log. Subsequent starts do nothing — the bcrypt hash on
// disk is the source of truth.
//
// When basic auth is configured the operator never types a password
// into the webapp login form, so the first-run bcrypt seed is
// unnecessary. We still create an anonymous user row so the basic-auth
// login flow has a stable user_id to anchor sessions on; the row's
// bcrypt hash is intentionally unusable.
//
// Called by cmd/rsmon-worker/main.go after New() and before
// Start() so the listener accepts the login form even before the
// worker has a websocket connection to the main app.
func ProvisionFirstRunIfNeeded(srv *Server, logger *log.Logger) error {
	if srv == nil || srv.store == nil {
		return fmt.Errorf("webapp: nil server")
	}
	ctx := context.Background()
	existing, err := srv.store.GetUser(ctx)
	if err == nil && existing != nil {
		// User already provisioned — leave it alone.
		return nil
	}
	if srv.basicAuthOK {
		// Basic-auth operator never logs in via bcrypt; the user
		// row is just a placeholder for session.user_id.
		if err := srv.store.EnsureAnonymousUser(ctx); err != nil {
			return fmt.Errorf("webapp: provision anonymous user: %w", err)
		}
		logger.Printf("webapp: WORKER_LOGIN/WORKER_PASSWORD basic auth enabled; bcrypt first-run password skipped")
		return nil
	}
	plain, err := GenerateFirstRunPassword()
	if err != nil {
		return fmt.Errorf("webapp: mint first-run password: %w", err)
	}
	hash, err := HashPassword(plain)
	if err != nil {
		return fmt.Errorf("webapp: hash first-run password: %w", err)
	}
	if _, err := srv.store.CreateFirstRunUser(ctx, hash); err != nil {
		return fmt.Errorf("webapp: create first-run user: %w", err)
	}
	logger.Printf("==============================================================")
	logger.Printf("webapp: first-run password generated — print this NOW and store safely:")
	logger.Printf("webapp: password = %s", plain)
	logger.Printf("webapp: this password is shown only once. Log in and change it.")
	logger.Printf("==============================================================")
	return nil
}

func (s *Server) pruneLoop(ctx context.Context) {
	defer s.pruneWG.Done()
	ticker := time.NewTicker(defaultAuditPruneInterval)
	defer ticker.Stop()
	// Run once shortly after startup so a long-lived worker does not
	// wait a full day for the first prune.
	first := time.NewTimer(5 * time.Minute)
	defer first.Stop()
	for {
		select {
		case <-ctx.Done():
			return
		case <-s.pruneStop:
			return
		case <-first.C:
			if n, err := s.store.PruneAudit(ctx, defaultAuditRetention); err != nil {
				s.deps.Logger.Printf("audit prune: %v", err)
			} else if n > 0 {
				s.deps.Logger.Printf("audit prune: deleted %d old rows", n)
			}
		case <-ticker.C:
			if n, err := s.store.PruneAudit(ctx, defaultAuditRetention); err != nil {
				s.deps.Logger.Printf("audit prune: %v", err)
			} else if n > 0 {
				s.deps.Logger.Printf("audit prune: deleted %d old rows", n)
			}
		}
	}
}

// defaultDataDir returns the per-user state directory the worker
// webapp uses by default. Matches the path documented in the plan
// doc: $XDG_DATA_HOME/rsmon-worker (fallback ~/.local/share/rsmon-worker).
func defaultDataDir() string {
	if v := os.Getenv("RSMON_WEBAPP_DATA_DIR"); v != "" {
		return v
	}
	if v := os.Getenv("XDG_DATA_HOME"); v != "" {
		return filepath.Join(v, "rsmon-worker")
	}
	home, err := os.UserHomeDir()
	if err != nil || home == "" {
		return "/var/lib/rsmon-worker"
	}
	return filepath.Join(home, ".local", "share", "rsmon-worker")
}