package lockserver

import (
	"bufio"
	"fmt"
	"net"
	"net/url"
	"strings"
	"time"

	log "github.com/sirupsen/logrus"
)

const (
	kabaSTX = 0x02
	kabaETX = 0x03
	kabaACK = 0x06
	kabaNAK = 0x15
)

// BuildCommand builds a key encoding request command for the dormakaba/Kaba lock server.
//	KR|KTD|WS192.168.135.20|KC2|RN41|KO000000|GA241213|TI16:56|GD241214|DT11:00|G#75|
func (lock *KabaLockServer) BuildCommand(doorReq DoorCardRequest, checkIn, checkOut time.Time) error {
	const funcName = "DormakabaLockServer.BuildCommand"

	room := strings.TrimSpace(doorReq.RoomField)
	if room == "" {
		return fmt.Errorf("[%s] roomField is required", funcName)
	}

	if checkIn.IsZero() {
		return fmt.Errorf("[%s] checkin time is required", funcName)
	}

	if checkOut.IsZero() {
		return fmt.Errorf("[%s] checkout time is required", funcName)
	}

	ws := dormakabaWorkstationID()

	ga := checkIn.Format("060102")    // yyMMdd, example: 241213
	gd := checkOut.Format("060102")   // yyMMdd, example: 241214
	ti := checkIn.Format("15:04")     // HH:mm,  example: 16:56
	dt := checkOut.Format("15:04")    // HH:mm,  example: 11:00

	payload := fmt.Sprintf(
		"KR|KTD|WS%s|KC%s|RN%s|KO000000|GA%s|TI%s|GD%s|DT%s|G#75|",
		ws,
		lock.encoderAddr,
		room,
		ga,
		ti,
		gd,
		dt,
	)

	lock.command = wrapKabaFrame(payload)

	return nil
}

// LockSequence starts the link and performs key encoding.
func (lock *KabaLockServer) LockSequence() error {
	const funcName = "KabaLockServer.LockSequence"

	conn, err := InitializeServerConnection(LockServerURL)
	if err != nil {
		return err
	}
	defer conn.Close()

	reader := bufio.NewReader(conn)

	regs, err := lock.linkStart(conn, reader)
	if err != nil {
		return fmt.Errorf("[%s] linkStart failed: %v", funcName, err)
	}

	for _, reg := range regs {
		log.Printf("Received: %q", reg)
	}

	raw, err := lock.requestEncoding(conn, reader)
	if err != nil {
		return fmt.Errorf("[%s] request encoding failed: %v", funcName, err)
	}

	log.Infof("Encoding response: %s", raw)

	return nil
}

// linkStart sends the dormakaba/Kaba LS command.
//	LS|DA241213|TI165607|WS192.168.135.20|PW1234|
func (lock *KabaLockServer) linkStart(conn net.Conn, reader *bufio.Reader) ([]string, error) {
	ws := dormakabaWorkstationID()
	pw := dormakabaPassword()

	payload := fmt.Sprintf(
		"LS|DA%s|TI%s|WS%s|PW%s|",
		time.Now().Format("060102"), // yyMMdd
		time.Now().Format("150405"), // HHmmss
		ws,
		pw,
	)

	command := wrapKabaFrame(payload)

	log.Printf("Sending Link Start command: %q", command)

	if _, err := conn.Write(command); err != nil {
		return nil, fmt.Errorf("failed to send Link Start command: %v", err)
	}

	var registers []string
	timeout := 10 * time.Second

	for {
		conn.SetReadDeadline(time.Now().Add(timeout))

		b, err := reader.ReadByte()
		if err != nil {
			if netErr, ok := err.(net.Error); ok && netErr.Timeout() {
				if len(registers) > 0 {
					return registers, nil
				}
			}

			return nil, fmt.Errorf("error reading Link Start response: %v", err)
		}

		switch b {
		case kabaACK:
			registers = append(registers, "ACK")
			continue

		case kabaNAK:
			return registers, fmt.Errorf("received NAK after Link Start")

		case kabaSTX:
			frame, err := readKabaFrame(conn, reader, b, timeout)
			if err != nil {
				return registers, fmt.Errorf("failed to read Link Start frame: %v", err)
			}

			frameText := string(frame)
			registers = append(registers, frameText)

			clean := cleanKabaFrame(frameText)
			if strings.HasPrefix(clean, "LA|") {
				return registers, nil
			}

		default:
			log.Warnf("Ignoring unexpected byte during Link Start: 0x%X", b)
		}
	}
}

func (lock *KabaLockServer) requestEncoding(conn net.Conn, reader *bufio.Reader) (string, error) {
	log.Printf("Sending Encoding command: %q", lock.command)

	if _, err := conn.Write(lock.command); err != nil {
		return "", fmt.Errorf("failed to send Encoding command: %v", err)
	}

	deadline := time.Now().Add(60 * time.Second)

	for {
		remaining := time.Until(deadline)
		if remaining <= 0 {
			return "", fmt.Errorf("timeout waiting for dormakaba encoding response")
		}

		conn.SetReadDeadline(time.Now().Add(remaining))

		b, err := reader.ReadByte()
		if err != nil {
			return "", fmt.Errorf("error reading encoding response: %v", err)
		}

		switch b {
		case kabaACK:
			log.Debug("Received ACK after Encoding command")
			continue

		case kabaNAK:
			return "", fmt.Errorf("received NAK after Encoding command")

		case kabaSTX:
			frame, err := readKabaFrame(conn, reader, b, 60*time.Second)
			if err != nil {
				return "", fmt.Errorf("failed to read encoding response frame: %v", err)
			}

			raw := string(frame)
			clean := cleanKabaFrame(raw)

			log.Printf("Received Encoding frame: %q", clean)

			if strings.HasPrefix(clean, "KA|") {
				return parseDormakabaEncodingResponse(clean)
			}

			log.Warnf("Ignoring non-KA frame while waiting for encoding result: %q", clean)

		default:
			log.Warnf("Ignoring unexpected byte while waiting for encoding response: 0x%X", b)
		}
	}
}

func parseDormakabaEncodingResponse(clean string) (string, error) {
	if strings.Contains(clean, "|ASOK|") {
		return "Success: " + clean, nil
	}

	if strings.Contains(clean, "|AS") {
		return "", fmt.Errorf("negative dormakaba response: %s", clean)
	}

	return "", fmt.Errorf("unexpected dormakaba response: %s", clean)
}

func readKabaFrame(conn net.Conn, reader *bufio.Reader, firstByte byte, timeout time.Duration) ([]byte, error) {
	frame := []byte{firstByte}

	for {
		conn.SetReadDeadline(time.Now().Add(timeout))

		b, err := reader.ReadByte()
		if err != nil {
			return frame, fmt.Errorf("error reading frame body: %w", err)
		}

		frame = append(frame, b)

		if b == kabaETX {
			return frame, nil
		}
	}
}

func wrapKabaFrame(payload string) []byte {
	command := make([]byte, 0, len(payload)+2)
	command = append(command, kabaSTX)
	command = append(command, []byte(payload)...)
	command = append(command, kabaETX)

	return command
}

func cleanKabaFrame(raw string) string {
	return strings.Trim(raw, string([]byte{kabaSTX, kabaETX}))
}

func dormakabaPassword() string {
	if strings.TrimSpace(Cert) != "" {
		return strings.TrimSpace(Cert)
	}

	return "1234"
}

func dormakabaWorkstationID() string {
	parsed, err := url.Parse(LockServerURL)
	if err == nil && parsed.Host != "" {
		host := parsed.Host

		if h, _, splitErr := net.SplitHostPort(host); splitErr == nil {
			return h
		}

		return strings.Trim(host, "/")
	}

	raw := strings.TrimSpace(LockServerURL)
	raw = strings.TrimPrefix(raw, "http://")
	raw = strings.TrimPrefix(raw, "https://")
	raw = strings.Trim(raw, "/")

	if h, _, splitErr := net.SplitHostPort(raw); splitErr == nil {
		return h
	}

	if idx := strings.Index(raw, ":"); idx >= 0 {
		return raw[:idx]
	}

	return raw
}