#define BAUD_RATE 115200

#include "tty.h"
#include "config.h"
#include "fw.h"

#include "rom/crc.h"

#include <USB.h>
#include <HardwareSerial.h>

#define SOH  '\001'
#define STX  '\002'
#define ETX  '\003'
#define EOT  '\004'
#define ENQ  '\005'
#define ACK  '\006'
#define XON  '\021'		// DC1
#define WRST '\022'		// DC2 - window = 0
#define XOFF '\023'		// DC3
#define WGO  '\024'		// DC4 - window + 256 bytes
#define NAK  '\025'
#define SYN  '\026'
#define ETB  '\027'		// Not in upload mode
#define CAN  '\030'
#define EM   '\031'		// Packet offset too high
#define FS   '\034'
#define GS   '\035'
#define RS   '\036'
#define US   '\037'

#define WGO_CHUNK	256

#define STREAMBUF_SIZE	8192

static char enq_str[] = "\026\035MAX80 v0\004\r\n";
static const char fwupload_start[] =
    "\034\001: /// MAX80 FW UPLOAD ~@~ $\035\r\n";

void TTY::reset()
{
    rx.state  = rx_state::normal;
}

TTY::TTY(Stream &port)
{
    _port = &port;
    rx_sbuf = NULL;
    win_sem = xSemaphoreCreateMutexStatic(&win_sem_ss);
    reset();
}

TTY::~TTY()
{
    if (rx_sbuf)
	vStreamBufferDelete(rx_sbuf);
}

void TTY::_update_window(bool rst)
{
    xSemaphoreTake(win_sem, portMAX_DELAY);

    if (rst) {
	port().write(WRST);
	tx_window = 0;
    }

    while (xStreamBufferSpacesAvailable(rx_sbuf) >= tx_window + WGO_CHUNK) {
	tx_window += WGO_CHUNK;
	port().write(WGO);	// Space for one more window
    }

    xSemaphoreGive(win_sem);
}

int TTY::rxdata(void *buf, size_t len)
{
    if (!rx_sbuf)
	return 0;

    size_t rcv = xStreamBufferReceive(rx_sbuf, buf, len, portMAX_DELAY);
    _update_window(false);

    return rcv;
}

int TTY::rxdata(token_t me, void *buf, size_t len)
{
    TTY *tty = (TTY *)me;
    return tty->rxdata(buf, len);
}

void TTY::_upload_begin()
{
    if (rx_sbuf)
	xStreamBufferReset(rx_sbuf);
    else
	rx_sbuf = xStreamBufferCreate(STREAMBUF_SIZE, 1);

    if (!rx_sbuf)
	goto nak;

    if (firmware_update_start((read_func_t)TTY::rxdata, (token_t)this))
	goto nak;

    // Respond with WRST + n*WGO
    _update_window(true);
    rx.state = rx_state::hdr;
    return;

 nak:
    port().write(NAK);
    rx.state = rx_state::normal;
    return;
}

void TTY::_onerr()
{
    if (rx.state != rx_state::normal)
	_update_window(true);
}

// Change this to be a buffer...
void TTY::_onrx()
{
    int byte;
    int len;

    while (1) {
	int byte = port().read();
	if (byte == -1)
	    break;		// No more data

	switch (rx.state) {
	case rx_state::normal:
	    if (byte == fwupload_start[rx.rlen]) {
		if (!fwupload_start[++rx.rlen])
		    _upload_begin();
	    } else {
		rx.rlen = 0;
		switch (byte) {
		case ENQ:
		    port().write(enq_str);
		    byte = ETB;
		    break;
		case ETX:
		case EOT:
		case CAN:
		    byte = ETB;	// Not in file upload state
		    break;
		default:
		    // Normal echo
		    break;
		}
	    }
	    break;

	case rx_state::hdr:
	    if (rx.rlen > 0 || byte == STX) {
		rx.hdr_raw[rx.rlen++] = byte;
		byte = -1;
		if (rx.rlen == sizeof rx.hdr) {
		    // Start of data packet
		    rx.state = rx_state::data;
		    rx.rlen = 0;
		}
	    } else {
		switch (byte) {
		case ETX:
		case EOT:
		case CAN:
		    reset();
		    byte = CAN;
		    break;
		case ENQ:
		    byte = SYN;	// In file upload state
		    break;
		default:
		    // Normal echo
		    break;
		}
	    }
	    break;

	case rx_state::data:
	    rx_data[rx.rlen++] = byte;
	    byte = -1;
	    // rx.hdr.len = packet data len - 1
	    if (rx.rlen > rx.hdr.len) {
		int have = rx.rlen;
		uint32_t crc  = ~crc32_le(0, rx_data, have);

		if (crc != rx.hdr.crc) {
		    byte = NAK;
		} else if (rx.hdr.offs > rx.last_ack) {
		    byte = EM;
		} else {
		    int sent = 0;

		    tx_window -= rx.rlen;

		    if (rx.hdr.offs + rx.rlen <= rx.last_ack) {
			have = 0;
		    } else {
			uint32_t skip = rx.last_ack - rx.hdr.offs;
			have -= skip;
			sent = xStreamBufferSend(rx_sbuf, rx_data+skip, have, 0);
			rx.last_ack += sent;
		    }

		    if (sent == have)
			byte = ACK;
		    else
			_update_window(true);

		    rx.state = rx_state::hdr;
		    rx.rlen  = 0;
		}
	    }
	    break;
	}

	if (byte >= 0)
	    port().write(byte);
    }
}

void TTY::_onconnect()
{
    port().write(XON);
}

void TTY::_onbreak()
{
    reset();
}

void TTY::_ondisconnect()
{
    reset();
}

static TTY *uart_tty, *usb_tty;

void TTY::usb_onevent(void *arg, esp_event_base_t event_base,
		      int32_t event_id, void *event_data)
{
    switch (event_id) {
    case ARDUINO_USB_CDC_CONNECTED_EVENT:
    case ARDUINO_USB_CDC_LINE_STATE_EVENT:
	usb_tty->_onconnect();
	break;
    case ARDUINO_USB_CDC_DISCONNECTED_EVENT:
	usb_tty->_ondisconnect();
	break;
    case ARDUINO_USB_CDC_RX_EVENT:
	usb_tty->_onrx();
	break;
    case ARDUINO_USB_CDC_RX_OVERFLOW_EVENT:
	usb_tty->_onerr();
	break;
    default:
	// Do nothing
	break;
    }
}

void TTY::uart_onrx(void)
{
    uart_tty->_onrx();
}

void TTY::uart_onerr(hardwareSerial_error_t err)
{
    switch (err) {
    case UART_BREAK_ERROR:
	uart_tty->_onbreak();
	break;
    default:
	uart_tty->_onerr();
	break;
    }
}

void TTY::init()
{
    enq_str[sizeof(enq_str)-5] += max80_board_version;

    uart_tty = new TTY(Serial0);
    Serial0.begin(BAUD_RATE);
    Serial0.onReceive(uart_onrx, false);
    Serial0.onReceiveError(uart_onerr);

    usb_tty  = new TTY(Serial);
    Serial.onEvent(usb_onevent);
}

void TTY::ping()
{
}