package main

import (
	"bufio"
	"bytes"
	"context"
	"encoding/json"
	"fmt"
	"io"
	"log"
	"net/http"
	"os"
	"os/signal"
	"runtime/debug"
	"strconv"
	"strings"
	"sync"
	"syscall"
	"time"

	"github.com/prometheus/client_golang/prometheus"
	"github.com/prometheus/client_golang/prometheus/promauto"
	"github.com/prometheus/client_golang/prometheus/promhttp"

	"godoor/hash"
)

const (
	wiegand_a_default   = 17
	wiegand_b_default   = 18
	wiegand_bit_timeout = time.Millisecond * 8
	solenoid_default    = 21
)

type upstreamUpdate struct {
	AllowedHashes []string   `json:"allowed_hashes"`
	KeepOpenUntil *time.Time `json:"keep_open_until,omitempty"`
}

type ValidHashesT map[string]bool // bool has no meaning

type Config struct {
	door         string
	uidSalt      string
	doorOpenTime time.Duration
	mock         bool
	api          struct {
		allowed  string
		longpoll string
		swipe    string
		key      string
	}
	pins struct {
		wiegandA int
		wiegandB int
		solenoid int
	}
	prometheusMetricsBind string
}

type KeepDoorOpen struct {
	until time.Time
	timer *time.Timer
}

type OpenedTimestamp struct {
	Opened time.Time
	Closed *time.Time
}

var Commit = func() string {
	if info, ok := debug.ReadBuildInfo(); ok {
		for _, setting := range info.Settings {
			if setting.Key == "vcs.revision" {
				return setting.Value
			}
		}
	}

	return ""
}()

var Version string

var (
	config            Config
	VALID_HASHES_LOCK sync.Mutex
	VALID_HASHES      = make(ValidHashesT)
	wiegand           Wiegand
	keepDoorOpen      KeepDoorOpen
)

var (
	godoorBuildInfo = promauto.NewGaugeVec(prometheus.GaugeOpts{
		Name: "godoor_build_info",
		Help: "Build Information",
	}, []string{"version", "revision"})
	lastSyncTimestamp = promauto.NewGauge(prometheus.GaugeOpts{
		Name: "godoor_last_allow_list_sync_timestamp_seconds",
		Help: "Last time list of card hashes was pulled from the server",
	})
	apiFailuresCount = promauto.NewCounterVec(prometheus.CounterOpts{
		Name: "godoor_api_request_failures_total",
		Help: "HTTP API request failures count",
	}, []string{"api", "endpoint"})
	nrCardsInAllowList = promauto.NewGauge(prometheus.GaugeOpts{
		Name: "godoor_allowed_card_hashes_total",
		Help: "Number of card hashes in memory that can open the door",
	})
	doorOpenedCount = promauto.NewCounterVec(prometheus.CounterOpts{
		Name: "godoor_door_opens_total",
		Help: "Number of times door was opened",
	}, []string{"source"})
	cardSwipesCount = promauto.NewCounterVec(prometheus.CounterOpts{
		Name: "godoor_swipes_total",
		Help: "Number of times a card has been swiped",
	}, []string{"status"})
)

func main() {
	log.Printf("GoDoor ver: %s (%s)", Version, Commit)
	ctx, cancel := signal.NotifyContext(context.Background(), os.Interrupt, syscall.SIGTERM)
	defer cancel()

	loadConfig()
	log.Printf("Door name: %s\n", config.door)

	godoorBuildInfo.WithLabelValues(Version, Commit).Set(1)

	go func() {
		setup(ctx)
	}()

	<-ctx.Done()
	log.Printf("Cleanup\n")

	// cleanup
}

func loadConfig() {
	var err error

	config.door = os.Getenv("KDOORPI_DOOR")
	config.api.allowed = os.Getenv("KDOORPI_API_ALLOWED")
	config.api.longpoll = os.Getenv("KDOORPI_API_LONGPOLL")
	config.api.swipe = os.Getenv("KDOORPI_API_SWIPE")
	config.api.key = os.Getenv("KDOORPI_API_KEY")
	config.uidSalt = os.Getenv("KDOORPI_UID_SALT")

	config.doorOpenTime = 8 * time.Second
	if doorOpenTimeStr, ok := os.LookupEnv("KDOORPI_OPEN_TIME"); ok {
		if openTime, err := time.ParseDuration(doorOpenTimeStr); err != nil {
			log.Printf("parsing KDOORPI_OPEN_TIME: %v, keeping default %v", err, config.doorOpenTime)
		} else {
			config.doorOpenTime = openTime
		}
	}

	_, config.mock = os.LookupEnv("KDOORPI_MOCK_HW")
	config.prometheusMetricsBind = os.Getenv("KDOORPI_PROMETHEUS_METRICS_BIND")
	if config.prometheusMetricsBind == "" {
		config.prometheusMetricsBind = ":3334"
	}

	config.pins.wiegandA, err = strconv.Atoi(os.Getenv("KDOORPI_PIN_WIEGAND_A"))
	if err != nil {
		config.pins.wiegandA = wiegand_a_default
	}
	config.pins.wiegandB, err = strconv.Atoi(os.Getenv("KDOORPI_PIN_WIEGAND_B"))
	if err != nil {
		config.pins.wiegandB = wiegand_b_default
	}
	config.pins.solenoid, err = strconv.Atoi(os.Getenv("KDOORPI_PIN_SOLENOID"))
	if err != nil {
		config.pins.solenoid = solenoid_default
	}
}

func setup(ctx context.Context) {
	if config.mock {
		log.Println("MOCK mode enabled")
		if config.door == "" {
			config.door = "mockdoor"
		}
		wiegand = &WiegandMock{}
	} else {
		wiegand = WiegandSetup(config.pins.wiegandA, config.pins.wiegandB, wiegand_bit_timeout, config.pins.solenoid)
	}
	log.Println("HW Setup done")

	go runHttpServer()

	http.DefaultClient.Timeout = 120 * time.Second

	for {
		log.Println("Start initial token population")
		err := reloadInfo()
		if err == nil {
			break
		}
		apiFailuresCount.WithLabelValues("allowed", config.api.allowed).Inc()
		log.Printf("Initial token population failed. err: %v", err)
		log.Println("Retrying in 10 seconds...")
		time.Sleep(10 * time.Second)
	}

	log.Println("Initial token population success")

	allowedPollInterval := 15 * time.Second
	if intervalStr, ok := os.LookupEnv("KDOORPI_ALLOWED_POLL_INTERVAL"); ok {
		if interval, err := time.ParseDuration(intervalStr); err != nil {
			log.Printf("parsing KDOORPI_ALLOWED_POLL_INTERVAL: %v, keeping default %v", err, allowedPollInterval)
		} else if interval <= 0 {
			// time.NewTicker panics on a non-positive duration, so a malformed
			// setting like "0" or "-1s" would crash the controller. Keep the
			// safe default instead.
			log.Printf("KDOORPI_ALLOWED_POLL_INTERVAL must be positive, got %v, keeping default %v", interval, allowedPollInterval)
		} else {
			allowedPollInterval = interval
		}
	}

	go func() {
		ticker := time.NewTicker(allowedPollInterval)
		defer ticker.Stop()
		for range ticker.C {
			pollAllowedOnce()
		}
	}()

	go func() {
		for {
			err := waitEvents()
			if err != nil {
				apiFailuresCount.WithLabelValues("longpoll", config.api.longpoll).Inc()
				log.Printf("LongPoll for events failed: %v", err)
				log.Println("Will try to LongPoll again soon")
			}
			time.Sleep(1 * time.Second)
			go func() {
				err := reloadInfo()
				if err != nil {
					log.Printf("reloadTokens failed: %q", err)
					apiFailuresCount.WithLabelValues("allowed", config.api.allowed).Inc()
					// Intentionally no cancelKeepOpenDoor() here: the hold
					// fail-safe is owned by the fixed-interval periodic poll
					// above. Cancelling from this best-effort, per-iteration
					// refresh too would only add door flapping. Worst-case
					// stuck-open after proxy loss is ~reloadInfoTimeout + one
					// poll interval (a hung-but-connected proxy blocks the
					// in-flight reloadInfo until its request timeout).
				}
			}()
		}
	}()

	go listenSig1(ctx, wiegand)

	log.Println("Initialized longpoll event loop")

	go cardRunner(wiegand)

	log.Println("Setup completed")
}

func pollAllowedOnce() {
	err := reloadInfo()
	if err != nil {
		log.Printf("Periodic reloadInfo failed: %v", err)
		apiFailuresCount.WithLabelValues("allowed", config.api.allowed).Inc()
		// Fail safe: we can no longer confirm the door should stay
		// held open, so close it now rather than trusting a stale
		// deadline (up to 6h away). A later successful poll re-opens
		// it if the hold is still active server-side.
		cancelKeepOpenDoor()
	}
}

func listenSig1(ctx context.Context, wiegand Wiegand) {
	usrSig := make(chan os.Signal, 1)
	signal.Notify(usrSig, syscall.SIGUSR1)

	for {
		select {
		case <-usrSig:
			err := OpenAndCloseDoor(wiegand)
			log.Printf("Emergecy opening door as prompted by SIGUSR1")
			if err != nil {
				log.Printf("opening door: %v", err)
			}
		case <-ctx.Done():
			return
		}
	}
}

func runHttpServer() {
	http.Handle("/metrics", promhttp.Handler())
	log.Printf("Running prometheus metrics on http://%s/metrics", config.prometheusMetricsBind)
	log.Fatal(http.ListenAndServe(config.prometheusMetricsBind, nil))
}

func OpenAndCloseDoor(w Wiegand) error {
	err := OpenDoor(w)
	if err != nil {
		return err
	}

	keepDoorOpenLock.Lock()
	keepOpenUntil := keepDoorOpen.until
	keepDoorOpenLock.Unlock()
	if keepOpenUntil.After(time.Now()) {
		fmt.Println("Door is already open")
		return nil
	}

	fmt.Println("Door is now open")

	time.Sleep(config.doorOpenTime)

	// A hold may have been armed while we were sleeping. Re-check under the
	// lock and skip the close if so, holding the lock across the close decision
	// so an in-flight updateKeepOpenDoor cannot slip a hold in between the
	// check and the close. Otherwise this pulse would close a held-open door
	// and subsequent polls, seeing the timer as already valid, would never
	// reopen it, locking the door for the whole hold duration.
	keepDoorOpenLock.Lock()
	defer keepDoorOpenLock.Unlock()
	if keepDoorOpen.until.After(time.Now()) {
		fmt.Println("Door is held open, leaving open")
		return nil
	}

	err = CloseDoor(w)
	if err != nil {
		return err
	}
	fmt.Println("Door is now closed")

	return nil
}

func OpenDoor(w Wiegand) error {
	open, _ := w.IsDoorOpen()
	if open {
		return nil
	}
	return w.OpenDoor()
}

func CloseDoor(w Wiegand) error {
	open, _ := w.IsDoorOpen()
	if !open {
		return nil
	}
	return w.CloseDoor()
}

func cardRunner(w Wiegand) {
	for {
		card, err := w.GetCardUid()
		if err != nil {
			continue
		}

		// printCardId(card)
		hashedHex := hash.HashCardUid(card)
		log.Println(hashedHex)

		VALID_HASHES_LOCK.Lock()
		ok := VALID_HASHES[hashedHex]
		VALID_HASHES_LOCK.Unlock()

		go func() {
			err := sendSwipeEvent(hashedHex, ok)
			if err != nil {
				apiFailuresCount.WithLabelValues("swipe", config.api.swipe).Inc()
				log.Printf("Failed to send swipe event: %v", err)
			}
		}()

		if ok {
			log.Println("Opening door")
			err := OpenAndCloseDoor(w)
			cardSwipesCount.WithLabelValues("accepted").Inc()
			doorOpenedCount.WithLabelValues("card").Inc()
			if err != nil {
				log.Println("There was an error opening and closing the Door")
			}
		} else {
			cardSwipesCount.WithLabelValues("denied").Inc()
			log.Println("Unknown card")
		}

	}
}

func ParseNextMessage(r *bufio.Reader) (string, error) {
	var message string

	for {
		s, err := r.ReadString('\n')
		if err != nil {
			return message, err
		}

		message = message + s
		nextBytes, err := r.ReadByte()
		if err != nil {
			return message, err
		}

		if nextBytes == '\n' {
			return message, nil
		}

		r.UnreadByte()
	}
}

func waitEvents() error {
	req, err := http.NewRequest(http.MethodGet, config.api.longpoll, nil)
	if err != nil {
		return err
	}
	req.Header.Add("KEY", config.api.key)
	resp, err := http.DefaultClient.Do(req)
	if err != nil {
		return err
	}
	log.Printf("%v\n", resp)

	reader := bufio.NewReader(resp.Body)
	for {
		msg, err := ParseNextMessage(reader)
		if err != nil {
			if err == io.EOF {
				return nil
			}
			return err
		}

		for _, line := range strings.Split(msg, "\n") {
			data, found_data := strings.CutPrefix(line, "data: ")
			if !found_data {
				continue
			}
			log.Printf("got server data: %q\n", data)
			if strings.TrimSpace(data) == config.door {
				err := OpenAndCloseDoor(wiegand)
				doorOpenedCount.WithLabelValues("api").Inc()
				if err != nil {
					log.Println("There was an error opening and closing the Door")
				}
			}
		}

	}
}

// reloadInfoLock serializes reloadInfo so the periodic-poll and longpoll-driven
// callers cannot apply /allowed responses out of order (a slow stale response
// must not overwrite a newer one and, e.g., cancel a just-armed hold).
var reloadInfoLock sync.Mutex

// reloadInfoTimeout bounds a single /allowed fetch. The shared http client has a
// 120s timeout (needed by the longpoll), but the allow-list/keep-open fetch must
// be quick: a hung-but-connected proxy otherwise blocks the fail-safe close for
// up to 120s. This caps the worst-case stuck-open window to ~this + one interval.
const reloadInfoTimeout = 30 * time.Second

func reloadInfo() error {
	reloadInfoLock.Lock()
	defer reloadInfoLock.Unlock()

	ctx, cancel := context.WithTimeout(context.Background(), reloadInfoTimeout)
	defer cancel()
	req, err := http.NewRequestWithContext(ctx, http.MethodGet, config.api.allowed, nil)
	if err != nil {
		return err
	}
	req.Header.Add("KEY", config.api.key)
	req.Header.Add("DOOR_NAME", config.door)
	resp, err := http.DefaultClient.Do(req)
	if err != nil {
		return err
	}
	defer resp.Body.Close()
	if resp.StatusCode != 200 {
		log.Printf("%v\n", resp)
		// Treat a non-200 as a failure rather than parsing a possibly-cached or
		// error body: otherwise a stale future keep_open_until would defeat the
		// fail-safe, or a body lacking it would wrongly cancel a live hold. The
		// caller's error path then drives the documented fail-safe close.
		return fmt.Errorf("allowed endpoint returned status %d", resp.StatusCode)
	}

	var info upstreamUpdate

	body, err := io.ReadAll(resp.Body)
	if err != nil {
		return err
	}

	err = json.Unmarshal(body, &info)
	if err != nil {
		return err
	}

	// Update Allowed hashes
	validHashesPre := make(ValidHashesT)
	for _, hash := range info.AllowedHashes {
		validHashesPre[hash] = true
	}

	VALID_HASHES_LOCK.Lock()
	VALID_HASHES = validHashesPre
	VALID_HASHES_LOCK.Unlock()

	log.Printf("Got %d cards from server", len(info.AllowedHashes))
	nrCardsInAllowList.Set(float64(len(info.AllowedHashes)))

	// Update Keep open

	if info.KeepOpenUntil != nil {
		updateKeepOpenDoor(*info.KeepOpenUntil)
	} else {
		cancelKeepOpenDoor()
	}

	lastSyncTimestamp.SetToCurrentTime()

	return nil
}

func sendSwipeEvent(cardUidHash string, approved bool) error {
	swipeEvent := map[string]any{
		"uid_hash":  cardUidHash,
		"door":      config.door,
		"timestamp": time.Now().Format(time.RFC3339),
		"approved":   approved,
	}

	data, err := json.Marshal(swipeEvent)
	if err != nil {
		return err
	}

	req, err := http.NewRequest(http.MethodPost, config.api.swipe, bytes.NewReader(data))
	if err != nil {
		return err
	}
	req.Header.Add("KEY", config.api.key)
	req.Header.Add("Content-Type", "application/json")
	resp, err := http.DefaultClient.Do(req)
	if err != nil {
		return err
	}

	if !(resp.StatusCode >= 200 && resp.StatusCode < 300) {
		return fmt.Errorf("Server responded with %d", resp.StatusCode)
	}

	return nil
}