// Copyright 2013 Google Inc.  All rights reserved.
// Copyright 2016 the gousb Authors.  All rights reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package usb

// #include <libusb-1.0/libusb.h>
import "C"

import (
	"fmt"
	"log"
	"time"
	"unsafe"
)

type Endpoint interface {
	Read(b []byte) (int, error)
	Write(b []byte) (int, error)
	Interface() InterfaceSetup
	Info() EndpointInfo
}

type endpoint struct {
	*Device
	InterfaceSetup
	EndpointInfo
}

func (e *endpoint) Read(buf []byte) (int, error) {
	if EndpointDirection(e.Address)&ENDPOINT_DIR_MASK != ENDPOINT_DIR_IN {
		return 0, fmt.Errorf("usb: read: not an IN endpoint")
	}

	return e.transfer(buf, e.ReadTimeout)
}

func (e *endpoint) Write(buf []byte) (int, error) {
	if EndpointDirection(e.Address)&ENDPOINT_DIR_MASK != ENDPOINT_DIR_OUT {
		return 0, fmt.Errorf("usb: write: not an OUT endpoint")
	}

	return e.transfer(buf, e.WriteTimeout)
}

func (e *endpoint) Interface() InterfaceSetup { return e.InterfaceSetup }
func (e *endpoint) Info() EndpointInfo        { return e.EndpointInfo }

func (e *endpoint) transfer(buf []byte, timeout time.Duration) (int, error) {
	if len(buf) == 0 {
		return 0, nil
	}

	tt := e.TransferType()
	t, err := e.newUSBTransfer(tt, buf)
	if err != nil {
		return 0, err
	}
	defer t.free()

	if err := t.submit(timeout); err != nil {
		log.Printf("bulk: %s failed to submit: %s", tt, err)
		return 0, err
	}

	n, err := t.wait()
	if err != nil {
		log.Printf("bulk: %s failed: %s", tt, err)
		return 0, err
	}
	return n, err
}

func (e *endpoint) newUSBTransfer(tt TransferType, buf []byte) (*usbTransfer, error) {
	var isoPackets int
	if tt == TRANSFER_TYPE_ISOCHRONOUS {
		isoPackets = len(buf) / int(e.EndpointInfo.MaxIsoPacket)
	}

	xfer := C.libusb_alloc_transfer(C.int(isoPackets))
	if xfer == nil {
		return nil, fmt.Errorf("libusb_alloc_transfer(%d) failed", isoPackets)
	}

	done := make(chan struct{}, 1)
	xfer.user_data = (unsafe.Pointer)(&done)

	xfer.dev_handle = e.Device.handle
	xfer.endpoint = C.uchar(e.Address)
	xfer._type = C.uchar(tt)

	xfer.buffer = (*C.uchar)((unsafe.Pointer)(&buf[0]))
	xfer.length = C.int(len(buf))

	if tt == TRANSFER_TYPE_ISOCHRONOUS {
		xfer.num_iso_packets = C.int(isoPackets)
		C.libusb_set_iso_packet_lengths(xfer, C.uint(e.EndpointInfo.MaxIsoPacket))
	}

	return &usbTransfer{
		xfer: xfer,
		done: done,
		buf:  buf,
	}, nil
}