package sensor

import (
	"errors"
	"time"

	"git.mial.net/mokhtar/x1208-exporter/internal/max17040"
	"git.mial.net/mokhtar/x1208-exporter/internal/pld"
)

// Hardware composes the fuel gauge and the AC-present line into one Sensor.
//
// Each device owns its own reacquire-on-error policy, so a fault on one bus
// does not discard a healthy handle on the other.
type Hardware struct {
	gauge *max17040.Gauge
	line  *pld.Line
	now   func() time.Time
}

// NewHardware returns a Sensor backed by the real HAT. Neither device is opened
// until the first Read.
func NewHardware(i2cDevice, gpioChip string, gpioLine int) *Hardware {
	return &Hardware{
		gauge: max17040.New(i2cDevice),
		line:  pld.New(gpioChip, gpioLine),
		now:   time.Now,
	}
}

// Read returns a complete sample or an error. It never returns a partially
// populated Reading: a sample that is missing a channel cannot be rendered or
// acted on, so there is nothing useful to pass upwards.
//
// Both channels are attempted even when the first fails, so one tick reports
// every fault rather than hiding the second behind the first.
func (h *Hardware) Read() (Reading, error) {
	acPresent, acErr := h.line.Read()
	volts, soc, batErr := h.gauge.Read()
	if err := errors.Join(acErr, batErr); err != nil {
		return Reading{}, err
	}
	return Reading{
		ACPresent: acPresent,
		Volts:     volts,
		SOC:       soc,
		At:        h.now(),
	}, nil
}

// Close releases both devices, reporting every failure.
func (h *Hardware) Close() error {
	return errors.Join(h.line.Close(), h.gauge.Close())
}