package spi

import (
	"periph.io/x/periph/conn/physic"
	xspi "periph.io/x/periph/conn/spi"
	xsysfs "periph.io/x/periph/host/sysfs"
)

const (
	// NotInitialized is the initial value for a bus/chip
	NotInitialized = -1
)

// Operations are the wrappers around the actual functions used by the SPI device interface
type Operations interface {
	Close() error
	Tx(w, r []byte) error
}

// Connector lets Adaptors provide the interface for Drivers
// to get access to the SPI buses on platforms that support SPI.
type Connector interface {
	// GetSpiConnection returns a connection to a SPI device at the specified bus and chip.
	// Bus numbering starts at index 0, the range of valid buses is
	// platform specific. Same with chip numbering.
	GetSpiConnection(busNum, chip, mode, bits int, maxSpeed int64) (device Connection, err error)

	// GetSpiDefaultBus returns the default SPI bus index
	GetSpiDefaultBus() int

	// GetSpiDefaultChip returns the default SPI chip index
	GetSpiDefaultChip() int

	// GetDefaultMode returns the default SPI mode (0/1/2/3)
	GetSpiDefaultMode() int

	// GetDefaultMode returns the default SPI number of bits (8)
	GetSpiDefaultBits() int

	// GetSpiDefaultMaxSpeed returns the max SPI speed
	GetSpiDefaultMaxSpeed() int64
}

// Connection is a connection to a SPI device with a specific bus/chip.
// Provided by an Adaptor, usually just by calling the spi package's GetSpiConnection() function.
type Connection Operations

// SpiConnection is the implementation of the SPI interface using the periph.io
// sysfs implementation for Linux.
type SpiConnection struct {
	Operations
	port     xspi.PortCloser
	dev      xspi.Conn
	bus      int
	chip     int
	bits     int
	mode     int
	maxSpeed int64
}

// NewConnection creates and returns a new connection to a specific
// spi device on a bus/chip using the periph.io interface.
func NewConnection(port xspi.PortCloser, conn xspi.Conn) (connection *SpiConnection) {
	return &SpiConnection{port: port, dev: conn}
}

// Close the SPI connection.
func (c *SpiConnection) Close() error {
	return c.port.Close()
}

// Tx uses the SPI device to send/receive data.
func (c *SpiConnection) Tx(w, r []byte) error {
	return c.dev.Tx(w, r)
}

// GetSpiConnection is a helper to return a SPI device.
func GetSpiConnection(busNum, chipNum, mode, bits int, maxSpeed int64) (Connection, error) {
	p, err := xsysfs.NewSPI(busNum, chipNum)
	if err != nil {
		return nil, err
	}
	c, err := p.Connect(physic.Frequency(maxSpeed)*physic.Hertz, xspi.Mode(mode), bits)
	if err != nil {
		return nil, err
	}
	return NewConnection(p, c), nil
}