package tester

import (
	"errors"
	"time"
)

// ErrNotConnected is returned by Read() when Connect() has not been called.
var ErrNotConnected = errors.New("tester: not connected — call Connect() first")

// CableType identifies the physical cable standard being tested.
type CableType int

const (
	CableTypeUSB  CableType = iota
	CableTypeDP
	CableTypeHDMI
)

// TestResult captures all measurements from a single cable test run.
type TestResult struct {
	CableType     CableType
	USBVersion    string
	DPVersion     string
	HDMIVersion   string
	SpeedGbps     float64
	MaxWatts      int
	PinContinuity bool
	HasEMarker    bool
	ResistanceOhm float64
}

// LiveReading is a single sample from a streaming power/protocol meter (e.g. FNB58).
type LiveReading struct {
	Voltage     float64
	CurrentAmps float64
	PowerWatts  float64
	PDProtocol  string
	Timestamp   time.Time
}

// TesterDriver is the common interface for all discrete cable testers.
// Connect must be called before Read.
// Disconnect is idempotent.
type TesterDriver interface {
	Connect() error
	Read() (TestResult, error)
	Disconnect() error
}

// StreamingTesterDriver extends TesterDriver for devices that continuously
// emit live power/protocol readings (e.g. FNIRSI FNB58).
// Stream() returns a read-only channel that emits LiveReading values and is
// closed when the stream ends or Disconnect() is called.
// Calling Stream() before Connect() returns a pre-closed channel.
type StreamingTesterDriver interface {
	TesterDriver
	Stream() <-chan LiveReading
}