// (C) 2024 by Folkert van Heusden
// Released under MIT license

#if defined(ESP32)
#include <lwip/sockets.h>
#else
#include <poll.h>
#endif
#include <cstring>
#include <unistd.h>
#include <arpa/inet.h>
#include <sys/socket.h>

#include "bus.h"
#include "cpu.h"
#include "dc11.h"
#include "log.h"
#include "utils.h"


const char *const dc11_register_names[] { "RCSR", "RBUF", "TSCR", "TBUF" };

dc11::dc11(const int base_port, bus *const b):
	base_port(base_port),
	b(b)
{
	pfds = new pollfd[dc11_n_lines * 2]();

	// TODO move to begin()
	th = new std::thread(std::ref(*this));
}

dc11::~dc11()
{
	stop_flag = true;

	if (th) {
		th->join();
		delete th;
	}

	delete [] pfds;
}

void dc11::trigger_interrupt(const int line_nr, const bool is_tx)
{
	b->getCpu()->queue_interrupt(5, 0300 + line_nr * 010 + 4 * is_tx);
}

void dc11::operator()()
{
	set_thread_name("kek:DC11");

	DOLOG(info, true, "DC11 thread started");

	for(int i=0; i<dc11_n_lines; i++) {
		// client session
		pfds[dc11_n_lines + i].fd     = -1;
		pfds[dc11_n_lines + i].events = POLLIN;

		// listen on port
		int port = base_port + i + 1;

		pfds[i].fd = socket(AF_INET, SOCK_STREAM, 0);

		int reuse_addr = 1;
		if (setsockopt(pfds[i].fd, SOL_SOCKET, SO_REUSEADDR, (char *)&reuse_addr, sizeof(reuse_addr)) == -1) {
			close(pfds[i].fd);
			pfds[i].fd = -1;

			DOLOG(warning, true, "Cannot set reuseaddress for port %d (DC11)", port);
			continue;
		}

		set_nodelay(pfds[i].fd);

	        sockaddr_in listen_addr;
		memset(&listen_addr, 0, sizeof(listen_addr));
		listen_addr.sin_family      = AF_INET;
		listen_addr.sin_addr.s_addr = htonl(INADDR_ANY);
		listen_addr.sin_port        = htons(port);

		if (bind(pfds[i].fd, reinterpret_cast<struct sockaddr *>(&listen_addr), sizeof(listen_addr)) == -1) {
			close(pfds[i].fd);
			pfds[i].fd = -1;

			DOLOG(warning, true, "Cannot bind to port %d (DC11)", port);
			continue;
		}

		if (listen(pfds[i].fd, SOMAXCONN) == -1) {
			close(pfds[i].fd);
			pfds[i].fd = -1;

			DOLOG(warning, true, "Cannot listen on port %d (DC11)", port);
			continue;
		}

		pfds[i].events = POLLIN;
	}

	while(!stop_flag) {
		int rc = poll(pfds, dc11_n_lines * 2, 100);
		if (rc == 0)
			continue;

		// accept any new session
		for(int i=0; i<dc11_n_lines; i++) {
			if (pfds[i].revents != POLLIN)
				continue;

			int client_i = dc11_n_lines + i;

			// disconnect any existing client session
			// yes, one can ddos with this
			if (pfds[client_i].fd != -1) {
				close(pfds[client_i].fd);
				DOLOG(info, false, "Restarting session for port %d", base_port + i + 1);
			}

			pfds[client_i].fd = accept(pfds[i].fd, nullptr, nullptr);

			if (pfds[client_i].fd != -1) {
				set_nodelay(pfds[client_i].fd);

				std::unique_lock<std::mutex> lck(input_lock[i]);

				registers[i * 4 + 0] |= 0160000;  // "ERROR", RING INDICATOR, CARRIER TRANSITION
				if (is_rx_interrupt_enabled(i))
					trigger_interrupt(i, false);
			}
		}

		// receive data
		for(int i=dc11_n_lines; i<dc11_n_lines * 2; i++) {
			if (pfds[i].revents != POLLIN)
				continue;

			char buffer[32] { };
			int rc = read(pfds[i].fd, buffer, sizeof buffer);

			int  line_nr = i - dc11_n_lines;

			std::unique_lock<std::mutex> lck(input_lock[line_nr]);

			if (rc <= 0) {  // closed or error?
				DOLOG(info, false, "Failed reading from port %d", i - dc11_n_lines + 1);

				registers[line_nr * 4 + 0] |= 0140000;  // "ERROR", CARRIER TRANSITION

				close(pfds[i].fd);
				pfds[i].fd = -1;
			}
			else {
				for(int k=0; k<rc; k++)
					recv_buffers[line_nr].push_back(buffer[k]);

				registers[line_nr * 4 + 0] |= 128;  // DONE: bit 7
			}

			if (is_rx_interrupt_enabled(line_nr))
				trigger_interrupt(line_nr, false);
		}
	}

	DOLOG(info, true, "DC11 thread terminating");

	for(int i=0; i<dc11_n_lines * 2; i++) {
		if (pfds[i].fd != -1)
			close(pfds[i].fd);
	}
}

void dc11::reset()
{
}

bool dc11::is_rx_interrupt_enabled(const int line_nr)
{
	return !!(registers[line_nr * 4 + 0] & 64);
}

bool dc11::is_tx_interrupt_enabled(const int line_nr)
{
	return !!(registers[line_nr * 4 + 2] & 64);
}

uint8_t dc11::read_byte(const uint16_t addr)
{
	uint16_t v = read_word(addr & ~1);

	if (addr & 1)
		return v >> 8;

	return v;
}

uint16_t dc11::read_word(const uint16_t addr)
{
	int      reg     = (addr - DC11_BASE) / 2;
	int      line_nr = reg / 4;
	int      sub_reg = reg & 3;

	std::unique_lock<std::mutex> lck(input_lock[line_nr]);

	uint16_t vtemp   = registers[reg];

	if (sub_reg == 0) {  // receive status
		// emulate DTR, CTS & READY
		registers[line_nr * 4 + 0] &= ~1;  // DTR: bit 0  [RCSR]
		registers[line_nr * 4 + 0] &= ~4;  // CD : bit 2

		if (pfds[line_nr + dc11_n_lines].fd != -1) {
			registers[line_nr * 4 + 0] |= 1;
			registers[line_nr * 4 + 0] |= 4;
		}

		vtemp = registers[line_nr * 4 + 0];

		// clear error(s)
		registers[line_nr * 4 + 0] &= ~0160000;
	}
	else if (sub_reg == 1) {  // read data register
		TRACE("DC11: %zu characters in buffer for line %d", recv_buffers[line_nr].size(), line_nr);

		// get oldest byte in buffer
		if (recv_buffers[line_nr].empty() == false) {
			vtemp = *recv_buffers[line_nr].begin();

			// parity check
			registers[line_nr * 4 + 0] &= ~(1 << 5);
			registers[line_nr * 4 + 0] |= parity(vtemp) << 5;

			recv_buffers[line_nr].erase(recv_buffers[line_nr].begin());

			// still data in buffer? generate interrupt
			if (recv_buffers[line_nr].empty() == false) {
				registers[line_nr * 4 + 0] |= 128;  // DONE: bit 7

				if (is_rx_interrupt_enabled(line_nr))
					trigger_interrupt(line_nr, false);
			}
		}
	}
	else if (sub_reg == 2) {  // transmit status
		registers[line_nr * 4 + 2] &= ~2;  // CTS: bit 1  [TSCR]
		registers[line_nr * 4 + 2] &= ~128;  // READY: bit 7

		if (pfds[line_nr + dc11_n_lines].fd != -1) {
			registers[line_nr * 4 + 2] |= 2;
			registers[line_nr * 4 + 2] |= 128;
		}

		vtemp = registers[line_nr * 4 + 2];
	}

	TRACE("DC11: read register %06o (\"%s\", %d line %d): %06o", addr, dc11_register_names[sub_reg], sub_reg, line_nr, vtemp);

	return vtemp;
}

void dc11::write_byte(const uint16_t addr, const uint8_t v)
{
	uint16_t vtemp = registers[(addr - DC11_BASE) / 2];
	
	if (addr & 1) {
		vtemp &= ~0xff00;
		vtemp |= v << 8;
	}
	else {
		vtemp &= ~0x00ff;
		vtemp |= v;
	}

	write_word(addr, vtemp);
}

void dc11::write_word(const uint16_t addr, uint16_t v)
{
	int reg     = (addr - DC11_BASE) / 2;
	int line_nr = reg / 4;
	int sub_reg = reg & 3;

	std::unique_lock<std::mutex> lck(input_lock[line_nr]);

	TRACE("DC11: write register %06o (\"%s\", %d line_nr %d) to %06o", addr, dc11_register_names[sub_reg], sub_reg, line_nr, v);

	if (sub_reg == 3) {  // transmit buffer
		char c = v & 127;  // strip parity

		if (c <= 32 || c >= 127)
			TRACE("DC11: transmit [%d] on line %d", c, line_nr);
		else
			TRACE("DC11: transmit %c on line %d", c, line_nr);

		int fd = pfds[dc11_n_lines + line_nr].fd;

		if (fd != -1 && write(fd, &c, 1) != 1) {
			DOLOG(info, false, "DC11 line %d disconnected\n", line_nr + 1);

			registers[line_nr * 4 + 0] |= 0140000;  // "ERROR", CARRIER TRANSITION

			close(fd);
			pfds[dc11_n_lines + line_nr].fd = -1;
		}

		if (is_tx_interrupt_enabled(line_nr))
			trigger_interrupt(line_nr, true);
	}

	registers[reg] = v;
}