package usb

import (
	"errors"
	"strings"
)

// DeviceRole classifies what a USB device is used for in HWLab.
type DeviceRole int

const (
	RolePrinter    DeviceRole = iota
	RoleCableTester           // reserved for Phase 5
	RoleUnknown
)

// DeviceSpec describes a known USB peripheral by VID and PID.
type DeviceSpec struct {
	VID      string     // 4-hex-digit vendor ID, e.g. "0525"
	PID      string     // 4-hex-digit product ID, e.g. "a4a7"
	Name     string     // human-readable label for logs
	Role     DeviceRole
	BaudRate int // serial baud rate; 0 means use 9600 default
}

// VIDPID returns the canonical "VID:PID" key string.
func (s DeviceSpec) VIDPID() string { return s.VID + ":" + s.PID }

// String returns "VID:PID (Name)" format for logging.
func (s DeviceSpec) String() string { return s.VIDPID() + " (" + s.Name + ")" }

// KnownDevices maps "VID:PID" to DeviceSpec for all peripherals HWLab manages.
// Update VID/PID values after hardware characterization on 2026-04-13.
var KnownDevices = map[string]DeviceSpec{
	"0525:a4a7": {VID: "0525", PID: "a4a7", Name: "PRT Qutie", Role: RolePrinter, BaudRate: 9600},
	// TODO(hardware): Replace placeholder VID:PIDs after characterization 2026-04-13
	"dead0:0001": {VID: "dead0", PID: "0001", Name: "Treedix USB Tester", Role: RoleCableTester, BaudRate: 115200},
	"dead0:0002": {VID: "dead0", PID: "0002", Name: "Treedix DP Tester", Role: RoleCableTester, BaudRate: 115200},
	"dead0:0003": {VID: "dead0", PID: "0003", Name: "Treedix HDMI Tester", Role: RoleCableTester, BaudRate: 115200},
	// TODO(hardware): BaudRate 0 = HID protocol — replace VID:PID after characterization
	"dead0:0004": {VID: "dead0", PID: "0004", Name: "FNIRSI FNB58", Role: RoleCableTester, BaudRate: 0},
}

// DeviceState represents the current connection status of a managed device.
type DeviceState int

const (
	StateDisconnected DeviceState = iota
	StateConnected
)

// DeviceEvent is emitted on the Manager.Events() channel for any state change.
type DeviceEvent struct {
	VIDPID string
	Spec   DeviceSpec
	State  DeviceState
}

// Command is sent to a device goroutine via its command channel.
type Command struct {
	Type    CommandType
	Payload []byte
	Reply   chan<- error // caller closes or receives result
}

// CommandType discriminates Command variants.
type CommandType int

const (
	CmdWrite CommandType = iota
	CmdClose
)

// ParseVIDPID splits a "VID:PID" string into its constituent parts.
// Returns an error if the format is not exactly "xxxx:xxxx".
func ParseVIDPID(s string) (vid, pid string, err error) {
	parts := strings.SplitN(s, ":", 2)
	if len(parts) != 2 || parts[0] == "" || parts[1] == "" {
		return "", "", errors.New("invalid VID:PID format: expected \"xxxx:xxxx\", got " + s)
	}
	return parts[0], parts[1], nil
}