package drm

import (
	"fmt"
	"os"
	"path"
	"regexp"
	"strconv"
	"strings"

	"edge-infra.dev/pkg/sds/lib/edid"
)

const DRMPath = "/sys/class/drm"

const (
	SubSystem        = "drm"
	cardPrefix       = "card"
	edidFileName     = "edid"
	connectorPattern = "^card[0-9](-[A-Za-z0-9]+)+$"
)

// Connector represents a connector in /sys/class/drm,
// e.g. "card0-HDMI-A-1" or "card1-DP-2".
type Connector struct {
	card int
	port string
	edid *edid.EDID
}

// The full connector name, e.g. "card0-HDMI-A-1".
func (connector Connector) String() string {
	return fmt.Sprintf("%s%d-%s", cardPrefix, connector.card, connector.port)
}

// The connector's card, e.g. "card0".
func (connector Connector) Card() string {
	return fmt.Sprintf("%s%d", cardPrefix, connector.card)
}

// The connector's card number.
func (connector Connector) CardNum() int {
	return connector.card
}

// The connector's port, e.g. "HDMI-A-1".
func (connector Connector) Port() string {
	return connector.port
}

// The path to the connector, e.g. "/sys/class/drm/card0-HDMI-A-1".
func (connector Connector) Path() string {
	return path.Join(DRMPath, connector.String())
}

// The connector's EDID.
func (connector Connector) EDID() *edid.EDID {
	return connector.edid
}

// Override the connector's EDID.
func (connector *Connector) WithEDID(edid *edid.EDID) {
	connector.edid = edid
}

func NewConnector(name string) (*Connector, error) {
	cardName, port, err := SplitConnectorName(name)
	if err != nil {
		return nil, err
	}

	// we can ignore the error check as we already validated name
	card, err := strconv.Atoi(strings.TrimPrefix(cardName, cardPrefix))
	if err != nil {
		return nil, err
	}

	connector := &Connector{
		card: card,
		port: port,
	}

	// add EDID if it is present
	edid, err := edid.NewFromFile(path.Join(connector.Path(), edidFileName))
	if err == nil {
		connector.edid = edid
	}

	return connector, nil
}

// Splits connector into card and port,
// e.g. "card0-HDMI-A-1" becomes "card0" and "HDMI-A-1".
func SplitConnectorName(name string) (card, port string, err error) {
	if err := ValidateConnectorName(name); err != nil {
		return "", "", err
	}
	card, port, _ = strings.Cut(name, "-")
	return card, port, nil
}

// Checks connector name is of format "card<%d>-<port>",
// i.e. matches the pattern ^card[0-9](-[A-Za-z0-9]+)+$
func ValidateConnectorName(name string) error {
	re, err := regexp.Compile(connectorPattern)
	if err != nil {
		return err
	}

	if match := re.MatchString(name); !match {
		return fmt.Errorf("%s is not a valid connector name", name)
	}

	return nil
}

// Returns a list of all connectors in /sys/class/drm.
func Connectors() ([]Connector, error) {
	files, err := os.ReadDir(DRMPath)
	if err != nil {
		return nil, fmt.Errorf("failed to read directory %s: %w", DRMPath, err)
	}

	connectors := []Connector{}
	for _, file := range files {
		connector, err := NewConnector(file.Name())
		if err == nil {
			connectors = append(connectors, *connector)
		}
	}

	return connectors, nil
}