/*
 * Copyright (c) 2023 joshua stein <jcs@jcs.org>
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */

#include <string.h>
#include "nomodem.h"

struct nomodem_session *
nomodem_send(struct session *s, FILE *fp, char *filename)
{
	struct nomodem_session *ns;
	
	if (!fp)
		return NULL;
		
	ns = xmalloczero(sizeof(struct nomodem_session));
	if (ns == NULL)
		return NULL;

	ns->mode = NOMODEM_MODE_SENDING;
	ns->session = s;
	ns->file = fp;
	strlcpy(ns->file_name, filename, sizeof(ns->file_name));

	fseek(ns->file, 0, SEEK_END);
	ns->file_size = ftell(ns->file);
	fseek(ns->file, 0, SEEK_SET);
	
	/* initiator */
	session_printf(ns->session, "%c%c%c%c%c%c",
	  (char)NOMODEM_START0, (char)NOMODEM_START1,
	  (char)NOMODEM_START2, (char)NOMODEM_START3,
	  (char)NOMODEM_VERSION, (char)NOMODEM_CMD_SEND);
	
	/* file name size (byte), file name */
	session_printf(ns->session, "%c%s",
	  (unsigned char)strlen(ns->file_name), ns->file_name);
	  
	/* 32-bit file size (big-endian) */
	session_printf(ns->session, "%c%c%c%c",
	  (unsigned char)((ns->file_size >> 24) & 0xff),
	  (unsigned char)((ns->file_size >> 16) & 0xff),
	  (unsigned char)((ns->file_size >> 8) & 0xff),
	  (unsigned char)(ns->file_size & 0xff));
	session_flush(ns->session);
	
	ns->last_input = Time;
	ns->need_header_ack = true;
	
	return ns;
}

struct nomodem_session *
nomodem_receive(struct session *s, char *path)
{
	struct nomodem_session *ns;
	
	if (path == NULL)
		return NULL;
		
	ns = xmalloczero(sizeof(struct nomodem_session));
	if (ns == NULL)
		return NULL;

	ns->mode = NOMODEM_MODE_RECEIVING;
	ns->session = s;
	ns->file_path = xstrdup(path);
	if (ns->file_path == NULL) {
		xfree(&ns);
		return NULL;
	}
	
	ns->buf_size = sizeof(ns->session->ibuf);
	ns->buf = xmalloc(ns->buf_size);
	if (ns->buf == NULL) {
		xfree(&ns->file_path);
		xfree(&ns);
		return NULL;
	}
		
	ns->file = fopen(ns->file_path, "wb+");
	if (ns->file == NULL) {
		session_printf(ns->session, "[nomodem] Failed opening %s for writing",
		  ns->file_path);
		xfree(&ns->file_path);
		xfree(&ns);
		return NULL;
	}

	/* initiator */
	session_printf(ns->session, "%c%c%c%c%c%c",
	  (char)NOMODEM_START0, (char)NOMODEM_START1,
	  (char)NOMODEM_START2, (char)NOMODEM_START3,
	  (char)NOMODEM_VERSION, (char)NOMODEM_CMD_RECEIVE);
	session_flush(ns->session);
	
	ns->last_input = Time;
	ns->need_header = true;
	
	return ns;
}
bool
nomodem_timed_out(struct nomodem_session *ns)
{
	if ((Time - ns->last_input) > NOMODEM_TIMEOUT)
		return true;
	
	return false;
}

unsigned short
nomodem_get_char(struct nomodem_session *ns)
{
	unsigned char b;
	
	while (session_get_char(ns->session, &b) == 0) {
		if (ns->session->ending || nomodem_timed_out(ns))
			return -1;
	}

	ns->last_input = Time;
	
	return (short)b;
}

bool
nomodem_continue(struct nomodem_session *ns)
{
	size_t size, rsize, pos, tsize;
	short resp;
	unsigned short file_name_size, file_name_pos;
	
	switch (ns->mode) {
	case NOMODEM_MODE_SENDING:
		if (ns->need_header_ack) {
			resp = nomodem_get_char(ns);
			if (resp < 0)
				return false;
			size = ((unsigned long)(resp & 0xff)) << 24;
			
			resp = nomodem_get_char(ns);
			if (resp < 0)
				return false;
			size |= ((unsigned long)(resp & 0xff)) << 16;
	
			resp = nomodem_get_char(ns);
			if (resp < 0)
				return false;
			size |= ((unsigned long)(resp & 0xff)) << 8;
			
			resp = nomodem_get_char(ns);
			if (resp < 0)
				return false;
			size |= (unsigned long)(resp & 0xff);
			
			if (size != ns->file_size) {
				session_logf(ns->session,
				  "[nomodem] Header ack size %ld != file size %ld, "
				  "canceling", size, ns->file_size);
				return false;
			}
			
			ns->need_header_ack = false;
		}
	
		while (ns->session->obuflen > 0) {
			session_flush(ns->session);
			if (ns->session->ending)
				return false;
			if (nomodem_timed_out(ns))
				return false;
		}
	
		pos = ftell(ns->file);
		if (feof(ns->file))
			return false;
		size = fread(ns->session->obuf + 4, 1,
		  sizeof(ns->session->obuf) - 4, ns->file);
		if (size == 0)
			return false;
			
		ns->session->obuf[0] = (size >> 24) & 0xff;
		ns->session->obuf[1] = (size >> 16) & 0xff;
		ns->session->obuf[2] = (size >> 8) & 0xff;
		ns->session->obuf[3] = size & 0xff;
		
		ns->session->obuflen = size + 4;
		session_flush(ns->session);
		
		/* wait for ack */
		resp = nomodem_get_char(ns);
		
		if (resp != NOMODEM_ACK) {
			session_logf(ns->session, "[nomodem] Failed ack at chunk "
			  "%ld/%ld: %d", pos, ns->file_size, resp);
			return false;
		}
	
		if (feof(ns->file))
			return false;
		break;
	case NOMODEM_MODE_RECEIVING:
		if (ns->need_header) {
			file_name_size = nomodem_get_char(ns);
			if (file_name_size < 0)
				return false;
			
			/* get filename */
			file_name_pos = 0;
			while (file_name_size != 0) {
				resp = nomodem_get_char(ns);
				if (resp < 0)
					return false;
				
				if (file_name_pos < sizeof(ns->file_name) - 1) {
					ns->file_name[file_name_pos++] = (char)resp;
					ns->file_name[file_name_pos] = 0;
				}
				file_name_size--;
			}
			
			/* get file size */
			resp = nomodem_get_char(ns);
			if (resp < 0)
				return false;
			ns->file_size = ((unsigned long)(resp & 0xff)) << 24;
			
			resp = nomodem_get_char(ns);
			if (resp < 0)
				return false;
			ns->file_size |= ((unsigned long)(resp & 0xff)) << 16;
	
			resp = nomodem_get_char(ns);
			if (resp < 0)
				return false;
			ns->file_size |= ((unsigned long)(resp & 0xff)) << 8;
			
			resp = nomodem_get_char(ns);
			if (resp < 0)
				return false;
			ns->file_size |= (unsigned long)(resp & 0xff);
			
			/* ack */
			session_printf(ns->session, "%c%c%c%c",
			  (char)((ns->file_size >> 24) & 0xff),
			  (char)((ns->file_size >> 16) & 0xff),
			  (char)((ns->file_size >> 8) & 0xff),
			  (char)(ns->file_size & 0xff));
	
			ns->need_header = false;
		}
		
		pos = ftell(ns->file);
		if (pos >= ns->file_size)
			return false;
		
		/* get chunk size */
		resp = nomodem_get_char(ns);
		if (resp < 0)
			return false;
		size = ((unsigned long)(resp & 0xff)) << 24;
		
		resp = nomodem_get_char(ns);
		if (resp < 0)
			return false;
		size |= ((unsigned long)(resp & 0xff)) << 16;

		resp = nomodem_get_char(ns);
		if (resp < 0)
			return false;
		size |= ((unsigned long)(resp & 0xff)) << 8;
		
		resp = nomodem_get_char(ns);
		if (resp < 0)
			return false;
		size |= (unsigned long)(resp & 0xff);
		
		if (size > (1024 * 10)) {
			session_logf(ns->session, "[nomodem] Chunk size too large: %ld",
			  size);
			return false;
		}
		
		for (rsize = 0; rsize < size; ) {
			tsize = session_get_chars(ns->session, ns->buf,
			  MIN(ns->buf_size, size - rsize));
			if (ns->session->ending || nomodem_timed_out(ns))
				return false;
			if (tsize == 0) {
				uthread_yield();
				continue;
			}

			ns->last_input = Time;

			if (fwrite(ns->buf, 1, tsize, ns->file) != tsize) {
				session_logf(ns->session, "[nomodem] Failed writing to %s",
				  ns->file_path);
				return false;
			}
			
			rsize += tsize;
		}
		
		session_printf(ns->session, "%c", (char)NOMODEM_ACK);
		session_flush(ns->session);
		
		pos = ftell(ns->file);
		if (pos >= ns->file_size)
			return false;
	}

	return true;
}

void
nomodem_finish(struct nomodem_session **nsp)
{
	struct nomodem_session *ns = (struct nomodem_session *)*nsp;
	
	if (ns->file_path != NULL)
		xfree(&ns->file_path);
		
	if (ns->file)
		fclose(ns->file);
	
	if (ns->buf)
		xfree(&ns->buf);
	xfree(nsp);
}