/*
 *  Copyright (C) 2002-2021  The DOSBox Team
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation; either version 2 of the License, or
 *  (at your option) any later version.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License along
 *  with this program; if not, write to the Free Software Foundation, Inc.,
 *  51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
 */


#include "dosbox.h"

#if C_DIRECTSERIAL

#include "logging.h"
#include "serialport.h"
#include "directserial.h"
#include "misc_util.h"
#include "pic.h"

#include "libserial.h"

#include <chrono>

/* This is a serial passthrough class.  Its amazingly simple to */
/* write now that the serial ports themselves were abstracted out */

static double tap_now_us() {
	using namespace std::chrono;
	return duration<double, std::micro>(
		steady_clock::now().time_since_epoch()).count();
}

/* One log line per byte on the wire. Host-relative microseconds tell the
 * real-time story (the RIO's ACK deadline is wall clock); PIC_FullIndex()
 * (emulated ms) ties each byte to game-side timing. */
void CDirectSerial::tapLine(char dir, unsigned val, unsigned err) {
	if (!tap_fp) return;
	double us = tap_now_us() - tap_t0_us;
	if (err)
		fprintf(tap_fp, "%12.1f %11.3f %c %02X err=%02X\n",
		        us, PIC_FullIndex(), dir, val, err);
	else
		fprintf(tap_fp, "%12.1f %11.3f %c %02X\n",
		        us, PIC_FullIndex(), dir, val);
	fflush(tap_fp);
}

CDirectSerial::CDirectSerial (Bitu id, CommandLine* cmd)
					:CSerial (id, cmd) {
	InstallationSuccessful = false;
	comport = nullptr;

	rx_retry = 0;
    rx_retry_max = 0;
    rx_state = 0;

	std::string tmpstring;
	if(!cmd->FindStringBegin("realport:",tmpstring,false)) return;

	LOG_MSG ("Serial%d: Opening %s", (int)(COMNUMBER), tmpstring.c_str());
	if(!SERIAL_open(tmpstring.c_str(), &comport)) {
		char errorbuffer[256];
		SERIAL_getErrorString(errorbuffer, sizeof(errorbuffer));
		LOG_MSG("Serial%d: Serial Port \"%s\" could not be opened.",
			(int)(COMNUMBER), tmpstring.c_str());
		LOG_MSG("%s",errorbuffer);
		return;
	}

	// rxdelay: How many milliseconds to wait before causing an
	// overflow when the application is unresponsive.
	if(getBituSubstring("rxdelay:", &rx_retry_max, cmd)) {
		if(!(rx_retry_max<=10000)) {
			rx_retry_max=0;
		}
	}

	// rxpollus: host-port receive polling tick in MICROSECONDS (50..1000,
	// default 1000 = the stock 1ms tick). Lower values discover incoming
	// bytes sooner -- needed for hard-real-time serial peripherals like the
	// VWE RIO cockpit board, which drops comms on ACKs late by a few ms.
	Bitu rx_poll_us = 0;
	if(getBituSubstring("rxpollus:", &rx_poll_us, cmd)) {
		if(rx_poll_us < 50) rx_poll_us = 50;
		if(rx_poll_us > 1000) rx_poll_us = 1000;
		rx_poll_ms = (float)rx_poll_us / 1000.0f;
		LOG_MSG("Serial%d: receive poll tick %uus", (int)(COMNUMBER),
		        (unsigned)rx_poll_us);
	}

	// rxburst: deliver host-buffered received bytes <n> times faster than
	// emulated wire speed (they already paid wire time on the real cable).
	Bitu rx_burst = 0;
	if(getBituSubstring("rxburst:", &rx_burst, cmd)) {
		if(rx_burst < 1) rx_burst = 1;
		if(rx_burst > 64) rx_burst = 64;
		rx_burst_div = (float)rx_burst;
		LOG_MSG("Serial%d: receive burst delivery x%u", (int)(COMNUMBER),
		        (unsigned)rx_burst);
	}

	// RIO_TAP=<path> (host env, like the VPX_* vars): append one line per
	// TX/RX byte. Appends across runs; each open writes a header line.
	const char *tp = getenv("RIO_TAP");
	if (tp && tp[0]) {
		tap_fp = fopen(tp, "a");
		if (tap_fp) {
			tap_t0_us = tap_now_us();
			fprintf(tap_fp, "# COM%d tap open (host-us rel | emu-ms | dir | byte)\n",
			        (int)COMNUMBER);
			fflush(tap_fp);
			LOG_MSG("Serial%d: RIO_TAP logging to '%s'", (int)COMNUMBER, tp);
		} else {
			LOG_MSG("Serial%d: RIO_TAP cannot open '%s'", (int)COMNUMBER, tp);
		}
	}

	CSerial::Init_Registers();
	InstallationSuccessful = true;
	rx_state = D_RX_IDLE;
	setEvent(SERIAL_POLLING_EVENT, rx_poll_ms); // receive tick
}

CDirectSerial::~CDirectSerial () {
	if(comport) SERIAL_close(comport);
	if(tap_fp) fclose(tap_fp);
	// We do not use own events so we don't have to clear them.
}

// CanReceive: true:UART part has room left
// doReceive:  true:there was really a byte to receive
// rx_retry is incremented in polling events

// in POLLING_EVENT: always add new polling event
// D_RX_IDLE + CanReceive + doReceive		-> D_RX_WAIT   , add RX_EVENT
// D_RX_IDLE + CanReceive + not doReceive	-> D_RX_IDLE
// D_RX_IDLE + not CanReceive				-> D_RX_BLOCKED, add RX_EVENT

// D_RX_BLOCKED + CanReceive + doReceive	-> D_RX_FASTWAIT, rem RX_EVENT
//											   rx_retry=0   , add RX_EVENT
// D_RX_BLOCKED + CanReceive + !doReceive	-> D_RX_IDLE,     rem RX_EVENT
//											   rx_retry=0
// D_RX_BLOCKED + !CanReceive + doReceive + retry < max	-> D_RX_BLOCKED, rx_retry++ 
// D_RX_BLOCKED + !CanReceive + doReceive + retry >=max	-> rx_retry=0 	

// to be continued...

void CDirectSerial::handleUpperEvent(uint16_t type) {
/*
#if SERIAL_DEBUG
		const char* s;
		const char* s2;
		switch(type) {
		case SERIAL_POLLING_EVENT: s = "POLLING_EVENT"; break;
		case SERIAL_RX_EVENT: s = "RX_EVENT"; break;
		case SERIAL_TX_EVENT: s = "TX_EVENT"; break;
		case SERIAL_THR_EVENT: s = "THR_EVENT"; break;
		}
		switch(rx_state) {
		case D_RX_IDLE: s2 = "RX_IDLE"; break;
		case D_RX_WAIT: s2 = "RX_WAIT"; break;
		case D_RX_BLOCKED: s2 = "RX_BLOCKED"; break;
		case D_RX_FASTWAIT: s2 = "RX_FASTWAIT"; break;
		}
		log_ser(dbg_aux,"Directserial: Event enter %s, %s",s,s2);
#endif
		*/

	switch(type) {
		case SERIAL_POLLING_EVENT: {
			setEvent(SERIAL_POLLING_EVENT, rx_poll_ms);
			// update Modem input line states
			switch(rx_state) {
				case D_RX_IDLE:
					if(CanReceiveByte()) {
						if(doReceive()) {
							// a byte was received
							rx_state=D_RX_WAIT;
							setEvent(SERIAL_RX_EVENT, bytetime*0.9f/rx_burst_div);
						} // else still idle
					} else {
#if SERIAL_DEBUG
						if(!dbgmsg_poll_block) {
							log_ser(dbg_aux,"Directserial: block on polling.");
							dbgmsg_poll_block=true;
						}
#endif
						rx_state=D_RX_BLOCKED;
						// have both delays (1ms + bytetime)
						setEvent(SERIAL_RX_EVENT, bytetime*0.9f/rx_burst_div);
					}
					break;
				case D_RX_BLOCKED:
                    // one timeout tick
					if(!CanReceiveByte()) {
						rx_retry++;
						if(rx_retry>=rx_retry_max) {
							// it has timed out:
							rx_retry=0;
							removeEvent(SERIAL_RX_EVENT);
							if(doReceive()) {
								// read away everything
								// this will set overrun errors
								while(doReceive());
								rx_state=D_RX_WAIT;
								setEvent(SERIAL_RX_EVENT, bytetime*0.9f/rx_burst_div);
							} else {
								// much trouble about nothing
                                rx_state=D_RX_IDLE;
							}
						} // else wait further
					} else {
						// good: we can receive again
#if SERIAL_DEBUG
						dbgmsg_poll_block=false;
						dbgmsg_rx_block=false;
#endif
						removeEvent(SERIAL_RX_EVENT);
						rx_retry=0;
						if(doReceive()) {
							rx_state=D_RX_FASTWAIT;
							setEvent(SERIAL_RX_EVENT, bytetime*0.65f/rx_burst_div);
						} else {
							// much trouble about nothing
							rx_state=D_RX_IDLE;
						}
					}
					break;

				case D_RX_WAIT:
				case D_RX_FASTWAIT:
					break;
			}
			updateMSR();
			break;
		}
		case SERIAL_RX_EVENT: {
			switch(rx_state) {
				case D_RX_IDLE:
					LOG_MSG("internal error in directserial");
					break;

				case D_RX_BLOCKED: // try to receive
				case D_RX_WAIT:
				case D_RX_FASTWAIT:
					if(CanReceiveByte()) {
						// just works or unblocked
						rx_retry=0; // not waiting anymore
						if(doReceive()) {
							if(rx_state==D_RX_WAIT) setEvent(SERIAL_RX_EVENT, bytetime*0.9f/rx_burst_div);
							else {
								// maybe unblocked
								rx_state=D_RX_FASTWAIT;
								setEvent(SERIAL_RX_EVENT, bytetime*0.65f/rx_burst_div);
							}
						} else {
							// didn't receive anything
							rx_state=D_RX_IDLE;
						}
					} else {
						// blocking now or still blocked
#if SERIAL_DEBUG
						if(rx_state==D_RX_BLOCKED) {
							if(!dbgmsg_rx_block) {
                                log_ser(dbg_aux,"Directserial: rx still blocked (retry=%d)",rx_retry);
								dbgmsg_rx_block=true;
							}
						}






						else log_ser(dbg_aux,"Directserial: block on continued rx (retry=%d).",rx_retry);
#endif
						setEvent(SERIAL_RX_EVENT, bytetime*0.65f/rx_burst_div);
						rx_state=D_RX_BLOCKED;
					}

					break;
			}
			updateMSR();
			break;
		}
		case SERIAL_TX_EVENT: {
			// Maybe echo circuit works a bit better this way
			if(rx_state==D_RX_IDLE && CanReceiveByte()) {
				if(doReceive()) {
					// a byte was received
					rx_state=D_RX_WAIT;
					setEvent(SERIAL_RX_EVENT, bytetime*0.9f/rx_burst_div);
				}
			}
			ByteTransmitted();
			updateMSR();
			break;
		}
		case SERIAL_THR_EVENT: {
			ByteTransmitting();
			setEvent(SERIAL_TX_EVENT,bytetime*1.1f);
			break;				   
		}
	}
	/*
	#if SERIAL_DEBUG
		switch(type) {
		case SERIAL_POLLING_EVENT: s = "POLLING_EVENT"; break;
		case SERIAL_RX_EVENT: s = "RX_EVENT"; break;
		case SERIAL_TX_EVENT: s = "TX_EVENT"; break;
		case SERIAL_THR_EVENT: s = "THR_EVENT"; break;
		}
		switch(rx_state) {
			case D_RX_IDLE: s2 = "RX_IDLE"; break;
			case D_RX_WAIT: s2 = "RX_WAIT"; break;
			case D_RX_BLOCKED: s2 = "RX_BLOCKED"; break;
			case D_RX_FASTWAIT: s2 = "RX_FASTWAIT"; break;
		}
		log_ser(dbg_aux,"Directserial: Event exit %s, %s",s,s2);
#endif*/
}

bool CDirectSerial::doReceive() {
	int value = SERIAL_getextchar(comport);
	if(value) {
		tapLine('R', (unsigned)(value & 0xff), (unsigned)((value >> 8) & 0xff));
		receiveByteEx((uint8_t)(value&0xff),(uint8_t)((value&0xff00)>>8));
		return true;
	}
	return false;
}

// updatePortConfig is called when emulated app changes the serial port
// parameters baudrate, stopbits, number of databits, parity.
void CDirectSerial::updatePortConfig (uint16_t divider, uint8_t lcr) {
	uint8_t parity = 0;

	switch ((lcr & 0x38)>>3) {
	case 0x1: parity='o'; break;
	case 0x3: parity='e'; break;
	case 0x5: parity='m'; break;
	case 0x7: parity='s'; break;
	default: parity='n'; break;
	}

	uint8_t bytelength = (lcr & 0x3)+5;

	// baudrate
	Bitu baudrate;
	if(divider==0) baudrate=115200u;
	else baudrate = 115200u / divider;

	// stopbits
	uint8_t stopbits;
	if (lcr & 0x4) {
		if (bytelength == 5) stopbits = SERIAL_15STOP;
		else stopbits = SERIAL_2STOP;
	} else stopbits = SERIAL_1STOP;

	if (tap_fp) {
		fprintf(tap_fp, "# %12.1f %11.3f config %u baud %d%c%d\n",
		        tap_now_us() - tap_t0_us, PIC_FullIndex(),
		        (unsigned)baudrate, (int)bytelength, (char)parity, (int)stopbits);
		fflush(tap_fp);
	}
	if(!SERIAL_setCommParameters(comport, (int)baudrate, (char)parity, (char)stopbits, (char)bytelength)) {
#if SERIAL_DEBUG
		log_ser(dbg_aux,"Serial port settings not supported by host." );
#endif
		LOG_MSG ("Serial%d: Desired serial mode not supported (%d,%d,%c,%d)",
			(int)(COMNUMBER),(int)baudrate,(int)bytelength,parity,(int)stopbits);
	} 
	CDirectSerial::setRTSDTR(getRTS(), getDTR());
}

void CDirectSerial::updateMSR () {
	int new_status = SERIAL_getmodemstatus(comport);

	setCTS((new_status&SERIAL_CTS)? true:false);
	setDSR((new_status&SERIAL_DSR)? true:false);
	setRI((new_status&SERIAL_RI)? true:false);
	setCD((new_status&SERIAL_CD)? true:false);
}

void CDirectSerial::transmitByte (uint8_t val, bool first) {
	tapLine('T', val, 0);
	if(!SERIAL_sendchar(comport, (char)val))
		LOG_MSG("Serial%d: COM port error: write failed!", (int)COMNUMBER);
	if(first) setEvent(SERIAL_THR_EVENT, bytetime/8);
	else setEvent(SERIAL_TX_EVENT, bytetime);
}


// setBreak(val) switches break on or off
void CDirectSerial::setBreak (bool value) {
	if (tap_fp) {
		fprintf(tap_fp, "# %12.1f %11.3f break=%d\n",
		        tap_now_us() - tap_t0_us, PIC_FullIndex(), value ? 1 : 0);
		fflush(tap_fp);
	}
	SERIAL_setBREAK(comport,value);
}

// updateModemControlLines(mcr) sets DTR and RTS.
void CDirectSerial::setRTSDTR(bool rts, bool dtr) {
	if (tap_fp) {
		fprintf(tap_fp, "# %12.1f %11.3f rts=%d dtr=%d\n",
		        tap_now_us() - tap_t0_us, PIC_FullIndex(),
		        rts ? 1 : 0, dtr ? 1 : 0);
		fflush(tap_fp);
	}
	SERIAL_setRTS(comport,rts);
	SERIAL_setDTR(comport,dtr);
}

void CDirectSerial::setRTS(bool val) {
	if (tap_fp) {
		fprintf(tap_fp, "# %12.1f %11.3f rts=%d\n",
		        tap_now_us() - tap_t0_us, PIC_FullIndex(), val ? 1 : 0);
		fflush(tap_fp);
	}
	SERIAL_setRTS(comport,val);
}

void CDirectSerial::setDTR(bool val) {
	if (tap_fp) {
		fprintf(tap_fp, "# %12.1f %11.3f dtr=%d\n",
		        tap_now_us() - tap_t0_us, PIC_FullIndex(), val ? 1 : 0);
		fflush(tap_fp);
	}
	SERIAL_setDTR(comport,val);
}

#endif