// Copyright 2015 by Thorsten von Eicken, see LICENSE.txt

#include "espmissingincludes.h"
#include "c_types.h"
#include "user_interface.h"
#include "espconn.h"
#include "mem.h"
#include "osapi.h"
#include "gpio.h"

#include "uart.h"
#include "serbridge.h"
#include "serled.h"
#include "config.h"
#include "console.h"
#include "tcpclient.h"

static struct espconn serbridgeConn;
static esp_tcp serbridgeTcp;
static int8_t mcu_reset_pin, mcu_isp_pin;

static sint8 ICACHE_FLASH_ATTR espbuffsend(serbridgeConnData *conn, const char *data, uint16 len);

// Connection pool
serbridgeConnData connData[MAX_CONN];
// Given a pointer to an espconn struct find the connection that correcponds to it
static serbridgeConnData ICACHE_FLASH_ATTR *serbridgeFindConnData(void *arg) {
	struct espconn *conn = arg;
	return arg == NULL ? NULL : (serbridgeConnData *)conn->reverse;
}

//===== TCP -> UART

// Telnet protocol characters
#define IAC        255  // escape
#define WILL       251  // negotiation
#define SB         250  // subnegotiation begin
#define SE         240  // subnegotiation end
#define ComPortOpt  44  // COM port options
#define SetControl   5  // Set control lines
#define DTR_ON       8  // used here to reset microcontroller
#define DTR_OFF      9
#define RTS_ON      11  // used here to signal ISP (in-system-programming) to uC
#define RTS_OFF     12

// telnet state machine states
enum { TN_normal, TN_iac, TN_will, TN_start, TN_end, TN_comPort, TN_setControl };

// process a buffer-full on a telnet connection and return the ending telnet state
static uint8_t ICACHE_FLASH_ATTR
telnetUnwrap(uint8_t *inBuf, int len, uint8_t state)
{
	for (int i=0; i<len; i++) {
		uint8_t c = inBuf[i];
		switch (state) {
		default:
		case TN_normal:
			if (c == IAC) state = TN_iac; // escape char: see what's next
			else uart0_write_char(c);     // regular char
			break;
		case TN_iac:
			switch (c) {
			case IAC:                     // second escape -> write one to outbuf and go normal again
				state = TN_normal;
				uart0_write_char(c);
				break;
			case WILL:                    // negotiation
				state = TN_will;
				break;
			case SB:                      // command sequence begin
				state = TN_start;
				break;
			case SE:                      // command sequence end
				state = TN_normal;
				break;
			default:                      // not sure... let's ignore
				uart0_write_char(IAC);
				uart0_write_char(c);
			}
			break;
		case TN_will:
			state = TN_normal;            // yes, we do COM port options, let's go back to normal
			break;
		case TN_start:                  // in command seq, now comes the type of cmd
			if (c == ComPortOpt) state = TN_comPort;
			else state = TN_end;          // an option we don't know, skip 'til the end seq
			break;
		case TN_end:                    // wait for end seq
			if (c == IAC) state = TN_iac; // simple wait to accept end or next escape seq
			break;
		case TN_comPort:
			if (c == SetControl) state = TN_setControl;
			else state = TN_end;
			break;
		case TN_setControl:             // switch control line and delay a tad
			switch (c) {
			case DTR_ON:
				if (mcu_reset_pin >= 0) {
					os_printf("MCU reset gpio%d\n", mcu_reset_pin);
					GPIO_OUTPUT_SET(mcu_reset_pin, 0);
					os_delay_us(100L);
				} else os_printf("MCU reset: no pin\n");
				break;
			case DTR_OFF:
				if (mcu_reset_pin >= 0) {
					GPIO_OUTPUT_SET(mcu_reset_pin, 1);
					os_delay_us(100L);
				}
				break;
			case RTS_ON:
				if (mcu_isp_pin >= 0) {
					os_printf("MCU ISP gpio%d\n", mcu_isp_pin);
					GPIO_OUTPUT_SET(mcu_isp_pin, 0);
					os_delay_us(100L);
				} else os_printf("MCU isp: no pin\n");
				break;
			case RTS_OFF:
				if (mcu_isp_pin >= 0) {
					GPIO_OUTPUT_SET(mcu_isp_pin, 1);
					os_delay_us(100L);
				}
				break;
			}
			state = TN_end;
			break;
		}
	}
	return state;
}

void ICACHE_FLASH_ATTR serbridgeReset() {
	if (mcu_reset_pin >= 0) {
		os_printf("MCU reset gpio%d\n", mcu_reset_pin);
		GPIO_OUTPUT_SET(mcu_reset_pin, 0);
		os_delay_us(100L);
		GPIO_OUTPUT_SET(mcu_reset_pin, 1);
	} else os_printf("MCU reset: no pin\n");
}

// Receive callback
static void ICACHE_FLASH_ATTR serbridgeRecvCb(void *arg, char *data, unsigned short len) {
	serbridgeConnData *conn = serbridgeFindConnData(arg);
	//os_printf("Receive callback on conn %p\n", conn);
	if (conn == NULL) return;

	// at the start of a connection we're in cmInit mode and we wait for the first few characters
	// to arrive in order to decide what type of connection this is.. The following if statements
	// do this dispatch. An issue here is that we assume that the first few characters all arrive
	// in the same TCP packet, which is true if the sender is a program, but not necessarily
	// if the sender is a person typing (although in that case the line-oriented TTY input seems
	// to make it work too). If this becomes a problem we need to buffer the first few chars...
	if (conn->conn_mode == cmInit) {

		// If the connection starts with the Arduino or ARM reset sequence we perform a RESET
		if ((len == 2 && strncmp(data, "0 ", 2) == 0) ||
				(len == 2 && strncmp(data, "?\n", 2) == 0) ||
				(len == 3 && strncmp(data, "?\r\n", 3) == 0)) {
			os_printf("MCU Reset=%d ISP=%d\n", mcu_reset_pin, mcu_isp_pin);
			os_delay_us(2*1000L); // time for os_printf to happen
			// send reset to arduino/ARM
			if (mcu_reset_pin >= 0) GPIO_OUTPUT_SET(mcu_reset_pin, 0);
			os_delay_us(100L);
			if (mcu_isp_pin >= 0) GPIO_OUTPUT_SET(mcu_isp_pin, 0);
			os_delay_us(100L);
			if (mcu_reset_pin >= 0) GPIO_OUTPUT_SET(mcu_reset_pin, 1);
			os_delay_us(100L);
			if (mcu_isp_pin >= 0) GPIO_OUTPUT_SET(mcu_isp_pin, 1);
			os_delay_us(1000L);
			conn->conn_mode = cmAVR;


		// If the connection starts with a telnet negotiation we will do telnet
		} else if (len >= 3 && strncmp(data, (char[]){IAC, WILL, ComPortOpt}, 3) == 0) {
			conn->conn_mode = cmTelnet;
			conn->telnet_state = TN_normal;
			// note that the three negotiation chars will be gobbled-up by telnetUnwrap
			os_printf("telnet mode\n");

		// looks like a plain-vanilla connection!
		} else {
			conn->conn_mode = cmTransparent;
		}

	// Process return data on TCP client connections
	} else if (conn->conn_mode == cmTcpClient) {
	}

	// write the buffer to the uart
	if (conn->conn_mode == cmTelnet) {
		conn->telnet_state = telnetUnwrap((uint8_t *)data, len, conn->telnet_state);
	} else {
		uart0_tx_buffer(data, len);
	}

	serledFlash(50); // short blink on serial LED
}

//===== UART -> TCP

// Transmit buffers for the connection pool
static char txbuffer[MAX_CONN][MAX_TXBUFFER];

// Send all data in conn->txbuffer
// returns result from espconn_sent if data in buffer or ESPCONN_OK (0)
// Use only internally from espbuffsend and serbridgeSentCb
static sint8 ICACHE_FLASH_ATTR sendtxbuffer(serbridgeConnData *conn) {
	sint8 result = ESPCONN_OK;
	if (conn->txbufferlen != 0) {
		//os_printf("%d TX %d\n", system_get_time(), conn->txbufferlen);
		conn->readytosend = false;
		result = espconn_sent(conn->conn, (uint8_t*)conn->txbuffer, conn->txbufferlen);
		conn->txbufferlen = 0;
		if (result != ESPCONN_OK) {
			os_printf("sendtxbuffer: espconn_sent error %d on conn %p\n", result, conn);
		}
	}
	return result;
}

// espbuffsend adds data to the send buffer. If the previous send was completed it calls
// sendtxbuffer and espconn_sent.
// Returns ESPCONN_OK (0) for success, -128 if buffer is full or error from  espconn_sent
// Use espbuffsend instead of espconn_sent as it solves the problem that espconn_sent must
// only be called *after* receiving an espconn_sent_callback for the previous packet.
static sint8 ICACHE_FLASH_ATTR espbuffsend(serbridgeConnData *conn, const char *data, uint16 len) {
	if (conn->txbufferlen + len > MAX_TXBUFFER) {
		os_printf("espbuffsend: txbuffer full on conn %p\n", conn);
		return -128;
	}
	os_memcpy(conn->txbuffer + conn->txbufferlen, data, len);
	conn->txbufferlen += len;
	if (conn->readytosend) {
		return sendtxbuffer(conn);
	} else {
		//os_printf("%d QU %d\n", system_get_time(), conn->txbufferlen);
	}
	return ESPCONN_OK;
}

//callback after the data are sent
static void ICACHE_FLASH_ATTR
serbridgeSentCb(void *arg) {
	serbridgeConnData *conn = serbridgeFindConnData(arg);
	//os_printf("Sent callback on conn %p\n", conn);
	if (conn == NULL) return;
	//os_printf("%d ST\n", system_get_time());
	conn->readytosend = true;
	sendtxbuffer(conn); // send possible new data in txbuffer
}

// TCP client connection state machine
// This processes commands from the attached uC to open outboud TCP connections
enum {
	TC_idle,       // in-between commands
	TC_newline,    // newline seen
	TC_start,      // start character (~) seen
	TC_cmd,        // command start (@) seen
	TC_cmdChar,    // command character seen
	TC_cmdLine,    // accumulating command
	TC_tdchan,     // saw data channel character
	TC_tdlen1,     // saw first data length character
	TC_tdata0,     // accumulate data, zero-terminated
	TC_tdataN,     // accumulate data, length-terminated
};
static uint8_t tcState = TC_newline;
static uint8_t tcChan; // channel for current command (index into tcConn)

#define CMD_MAX 256
static char tcCmdBuf[CMD_MAX];
static short tcCmdBufLen = 0;
static char tcCmdChar;
static short tcLen;

// scan a buffer for tcp client commands
static int ICACHE_FLASH_ATTR
tcpClientProcess(char *buf, int len)
{
	char *in=buf, *out=buf;
	for (short i=0; i<len; i++) {
		char c = *in++;
		//os_printf("tcState=%d c=%c\n", tcState, c);
		switch (tcState) {
		case TC_idle:
			if (c == '\n') tcState = TC_newline;
			break;
		case TC_newline: // saw newline, expect ~
			if (c == '~') {
				tcState = TC_start;
				continue; // gobble up the ~
			} else {
				break;
			}
		case TC_start: // saw ~, expect channel number
			if (c == '@') {
				tcState = TC_cmd;
				continue;
			} else if (c >= '0' && c <= '9') {
				tcChan = c-'0';
				tcState = TC_tdchan;
				continue;
			}
			*out++ = '~'; // make up for '~' we skipped
			break;
		case TC_cmd: // saw control char (@), expect channel char
			if (c >= '0' && c <= '9') {
				tcChan = c-'0';
				tcState = TC_cmdChar;
				continue;
			} else {
				*out++ = '~'; // make up for '~' we skipped
				*out++ = '@'; // make up for '@' we skipped
				break;
			}
		case TC_cmdChar: // saw channel number, expect command char
			tcCmdChar = c;   // save command character
			tcCmdBufLen = 0; // empty the command buffer
			tcState = TC_cmdLine;
			continue;
		case TC_cmdLine: // accumulating command in buffer
			if (c != '\n') {
				if (tcCmdBufLen < CMD_MAX) tcCmdBuf[tcCmdBufLen++] = c;
			} else {
				tcpClientCommand(tcChan, tcCmdChar, tcCmdBuf);
				tcState = TC_newline;
			}
			continue;
		case TC_tdchan: // saw channel number, getting first length char
			if (c >= '0' && c <= '9') {
				tcLen = c-'0';
			} else if (c >= 'A' && c <= 'F') {
				tcLen = c-'A'+10;
			} else {
				*out++ = '~'; // make up for '~' we skipped
				*out++ = '0'+tcChan;
				break;
			}
			tcState = TC_tdlen1;
			continue;
		case TC_tdlen1: // saw first length char, get second
			tcLen *= 16;
			if (c >= '0' && c <= '9') {
				tcLen += c-'0';
			} else if (c >= 'A' && c <= 'F') {
				tcLen += c-'A'+10;
			} else {
				*out++ = '~'; // make up for '~' we skipped
				*out++ = '0'+tcChan;
				break;
			}
			tcState = tcLen == 0 ? TC_tdata0 : TC_tdataN;
			continue;
		case TC_tdata0: // saw data length, getting data characters zero-terminated
			if (c != 0) {
				tcpClientSendChar(tcChan, c);
			} else {
				tcpClientSendPush(tcChan);
				tcState = TC_idle;
			}
			continue;
		case TC_tdataN: // saw data length, getting data characters length-terminated
			tcpClientSendChar(tcChan, c);
			tcLen--;
			if (tcLen == 0) {
				tcpClientSendPush(tcChan);
				tcState = TC_idle;
			}
			continue;
		}
		*out++ = c;
	}
	//if (tcState != TC_idle) os_printf("tcState=%d\n", tcState);
	return out-buf;
}

// callback with a buffer of characters that have arrived on the uart
void ICACHE_FLASH_ATTR
serbridgeUartCb(char *buf, int length) {
	// push the buffer into the microcontroller console
	for (int i=0; i<length; i++)
		console_write_char(buf[i]);
	// parse the buffer for TCP commands, this may remove characters from the buffer
	length = tcpClientProcess(buf, length);
	// push the buffer into each open connection
	if (length > 0) {
		for (int i=0; i<MAX_CONN; i++) {
			if (connData[i].conn && connData[i].conn_mode != cmTcpClient) {
				espbuffsend(&connData[i], buf, length);
			}
		}
	}
	serledFlash(50); // short blink on serial LED
}

//===== Connect / disconnect

// Error callback (it's really poorly named, it's not a "connection reconnected" callback,
// it's really a "connection broken, please reconnect" callback)
static void ICACHE_FLASH_ATTR serbridgeReconCb(void *arg, sint8 err) {
	serbridgeConnData *sbConn = serbridgeFindConnData(arg);
	if (sbConn == NULL) return;
	// Close the connection
	espconn_disconnect(sbConn->conn);
	// free connection slot
	sbConn->conn = NULL;
}

// Disconnection callback
static void ICACHE_FLASH_ATTR serbridgeDisconCb(void *arg) {
	serbridgeConnData *sbConn = serbridgeFindConnData(arg);
	if (sbConn == NULL) return;
	// send reset to arduino/ARM
	if (sbConn->conn_mode == cmAVR && mcu_reset_pin >= 0) {
		GPIO_OUTPUT_SET(mcu_reset_pin, 0);
		os_delay_us(100L);
		GPIO_OUTPUT_SET(mcu_reset_pin, 1);
	}
	// free connection slot
	sbConn->conn = NULL;
}

// New connection callback, use one of the connection descriptors, if we have one left.
static void ICACHE_FLASH_ATTR serbridgeConnectCb(void *arg) {
	struct espconn *conn = arg;
	// Find empty conndata in pool
	int i;
	for (i=0; i<MAX_CONN; i++) if (connData[i].conn==NULL) break;
	os_printf("Accept port 23, conn=%p, pool slot %d\n", conn, i);

	if (i==MAX_CONN) {
		os_printf("Aiee, conn pool overflow!\n");
		espconn_disconnect(conn);
		return;
	}

	conn->reverse = connData+i;
	connData[i].conn = conn;
	connData[i].txbufferlen = 0;
	connData[i].readytosend = true;
	connData[i].telnet_state = 0;
	connData[i].conn_mode = cmInit;

	espconn_regist_recvcb(conn, serbridgeRecvCb);
	espconn_regist_reconcb(conn, serbridgeReconCb);
	espconn_regist_disconcb(conn, serbridgeDisconCb);
	espconn_regist_sentcb(conn, serbridgeSentCb);

	espconn_set_opt(conn, ESPCONN_REUSEADDR|ESPCONN_NODELAY);
}

//===== Initialization

void ICACHE_FLASH_ATTR serbridgeInitPins() {
	mcu_reset_pin = flashConfig.reset_pin;
	mcu_isp_pin = flashConfig.isp_pin;
	os_printf("Serbridge pins: reset=%d isp=%d swap=%d\n",
			mcu_reset_pin, mcu_isp_pin, flashConfig.swap_uart);

	if (flashConfig.swap_uart) {
		PIN_FUNC_SELECT(PERIPHS_IO_MUX_MTCK_U, 4);
		PIN_FUNC_SELECT(PERIPHS_IO_MUX_MTDO_U, 4);
		PIN_PULLUP_DIS(PERIPHS_IO_MUX_MTCK_U);
		PIN_PULLUP_DIS(PERIPHS_IO_MUX_MTDO_U);
		system_uart_swap();
	} else {
		PIN_FUNC_SELECT(PERIPHS_IO_MUX_U0TXD_U, 0);
		PIN_FUNC_SELECT(PERIPHS_IO_MUX_U0RXD_U, 0);
		system_uart_de_swap();
	}

	// set both pins to 1 before turning them on so we don't cause a reset
	if (mcu_isp_pin >= 0)   GPIO_OUTPUT_SET(mcu_isp_pin, 1);
	if (mcu_reset_pin >= 0) GPIO_OUTPUT_SET(mcu_reset_pin, 1);
	// switch pin mux to make these pins GPIO pins
	if (mcu_reset_pin >= 0) makeGpio(mcu_reset_pin);
	if (mcu_isp_pin >= 0)   makeGpio(mcu_isp_pin);
}

// Start transparent serial bridge TCP server on specified port (typ. 23)
void ICACHE_FLASH_ATTR serbridgeInit(int port) {
	serbridgeInitPins();

	int i;
	for (i = 0; i < MAX_CONN; i++) {
		connData[i].conn = NULL;
		connData[i].txbuffer = txbuffer[i];
	}
	serbridgeConn.type = ESPCONN_TCP;
	serbridgeConn.state = ESPCONN_NONE;
	serbridgeTcp.local_port = port;
	serbridgeConn.proto.tcp = &serbridgeTcp;

	espconn_regist_connectcb(&serbridgeConn, serbridgeConnectCb);
	espconn_accept(&serbridgeConn);
	espconn_tcp_set_max_con_allow(&serbridgeConn, MAX_CONN);
	espconn_regist_time(&serbridgeConn, SER_BRIDGE_TIMEOUT, 0);
}