package usbgadget

import (
	"fmt"
	"os"
)

var keyboardConfig = gadgetConfigItem{
	order:      1000,
	device:     "hid.usb0",
	path:       []string{"functions", "hid.usb0"},
	configPath: []string{"hid.usb0"},
	attrs: gadgetAttributes{
		"protocol":      "1",
		"subclass":      "1",
		"report_length": "8",
	},
	reportDesc: keyboardReportDesc,
}

// Source: https://www.kernel.org/doc/Documentation/usb/gadget_hid.txt
var keyboardReportDesc = []byte{
	0x05, 0x01, /* USAGE_PAGE (Generic Desktop)	          */
	0x09, 0x06, /* USAGE (Keyboard)                       */
	0xa1, 0x01, /* COLLECTION (Application)               */
	0x05, 0x07, /*   USAGE_PAGE (Keyboard)                */
	0x19, 0xe0, /*   USAGE_MINIMUM (Keyboard LeftControl) */
	0x29, 0xe7, /*   USAGE_MAXIMUM (Keyboard Right GUI)   */
	0x15, 0x00, /*   LOGICAL_MINIMUM (0)                  */
	0x25, 0x01, /*   LOGICAL_MAXIMUM (1)                  */
	0x75, 0x01, /*   REPORT_SIZE (1)                      */
	0x95, 0x08, /*   REPORT_COUNT (8)                     */
	0x81, 0x02, /*   INPUT (Data,Var,Abs)                 */
	0x95, 0x01, /*   REPORT_COUNT (1)                     */
	0x75, 0x08, /*   REPORT_SIZE (8)                      */
	0x81, 0x03, /*   INPUT (Cnst,Var,Abs)                 */
	0x95, 0x05, /*   REPORT_COUNT (5)                     */
	0x75, 0x01, /*   REPORT_SIZE (1)                      */
	0x05, 0x08, /*   USAGE_PAGE (LEDs)                    */
	0x19, 0x01, /*   USAGE_MINIMUM (Num Lock)             */
	0x29, 0x05, /*   USAGE_MAXIMUM (Kana)                 */
	0x91, 0x02, /*   OUTPUT (Data,Var,Abs)                */
	0x95, 0x01, /*   REPORT_COUNT (1)                     */
	0x75, 0x03, /*   REPORT_SIZE (3)                      */
	0x91, 0x03, /*   OUTPUT (Cnst,Var,Abs)                */
	0x95, 0x06, /*   REPORT_COUNT (6)                     */
	0x75, 0x08, /*   REPORT_SIZE (8)                      */
	0x15, 0x00, /*   LOGICAL_MINIMUM (0)                  */
	0x25, 0x65, /*   LOGICAL_MAXIMUM (101)                */
	0x05, 0x07, /*   USAGE_PAGE (Keyboard)                */
	0x19, 0x00, /*   USAGE_MINIMUM (Reserved)             */
	0x29, 0x65, /*   USAGE_MAXIMUM (Keyboard Application) */
	0x81, 0x00, /*   INPUT (Data,Ary,Abs)                 */
	0xc0, /* END_COLLECTION                         */
}

func (u *UsbGadget) keyboardWriteHidFile(data []byte) error {
	if u.keyboardHidFile == nil {
		var err error
		u.keyboardHidFile, err = os.OpenFile("/dev/hidg0", os.O_RDWR, 0666)
		if err != nil {
			return fmt.Errorf("failed to open hidg0: %w", err)
		}
	}

	_, err := u.keyboardHidFile.Write(data)
	if err != nil {
		u.log.Errorf("failed to write to hidg0: %w", err)
		u.keyboardHidFile.Close()
		u.keyboardHidFile = nil
		return err
	}

	return nil
}

func (u *UsbGadget) KeyboardReport(modifier uint8, keys []uint8) error {
	u.keyboardLock.Lock()
	defer u.keyboardLock.Unlock()

	if len(keys) > 6 {
		keys = keys[:6]
	}
	if len(keys) < 6 {
		keys = append(keys, make([]uint8, 6-len(keys))...)
	}

	err := u.keyboardWriteHidFile([]byte{modifier, 0, keys[0], keys[1], keys[2], keys[3], keys[4], keys[5]})
	if err != nil {
		return err
	}

	u.resetUserInputTime()
	return nil
}