/* multipart-replace.c - handle mixed/x-multipart-replace streams
 *
 * Copyright (C) 2016  Luke Shumaker
 *
 * 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 3 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, see <http://www.gnu.org/licenses/>.
 */

#include <errno.h>
#include <error.h>
#include <stdio.h>
#include <stdlib.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

#include "multipart-replace.h"
#include "util.h"

#define error(stat, errnum, ...) do { \
		error(0, errnum, __VA_ARGS__); \
		ret = stat; \
		goto end; \
	} while(0)
#define stdioerror(stream, name) do {	  \
		if (feof(stream)) { \
			error(0, 0, "%s: EOF", name); \
		} else { \
			int err = ferror(stream); \
			if (err != 0) { \
				error(0, err, "%s", name); \
			} else { \
				error(0, 0, "%s: panic: neither feof nor ferror", name); \
			} \
			ret = EXIT_FAILURE; \
		} \
		goto end; \
	} while(0)

static
char *boundary_line(const char *old) {
	size_t len = strlen(old);
	char *new = xrealloc(NULL, len+5);
	new[0] = '-';
	new[1] = '-';
	strcpy(&new[2], old);
	new[2+len+0] = '\r';
	new[2+len+1] = '\n';
	new[2+len+2] = '\0';
	return new;
}

static
ssize_t safe_atoi(char *str) {
	while (*str == ' ')
		str++;
	size_t len = 0;
	while ('0' <= str[len] && str[len] <= '9')
		len++;
	size_t i = len;
	while (str[i] == ' ')
		i++;
	if (len < 1 || strcmp(&str[i], "\r\n") != 0)
		return -1;
	return atoi(str);
}

int multipart_replace_reader(struct multipart_replace_stream *s, int fd, const char *_boundary) {
	int ret = 0;
	FILE *stream = fdopen(fd, "r");
	char *boundary = boundary_line(_boundary);

	char *line_buf = NULL;
	size_t line_cap = 0;
	ssize_t line_len = 0;
	ssize_t content_length = -1;

	while (running) {
		content_length = -1;
		/* scan for the first non-empty line */
		do {
			line_len = getline(&line_buf, &line_cap, stream);
			if (line_len < 0)
				stdioerror(stream, "src");
		} while (strcmp(line_buf, "\r\n") == 0);
		/* make sure it matches the boundary separator */
		if (strcmp(line_buf, boundary) != 0)
			error(EXIT_FAILURE, 0, "line does not match boundary: \"%s\"", line_buf);
		/* read the frame header (MIME headers) */
		s->back->len = 0;
		do {
			line_len = getline(&line_buf, &line_cap, stream);
			if (line_len < 0)
				stdioerror(stream, "src");
			/* append the line to the frame contents */
			if ((ssize_t)s->back->cap < s->back->len + line_len)
				s->back->buf = xrealloc(s->back->buf, s->back->cap = s->back->len + line_len);
			memcpy(&s->back->buf[s->back->len], line_buf, line_len);
			s->back->len += line_len;
			/* parse the Content-length (if applicable) */
			if (strncasecmp(line_buf, "Content-length:", strlen("Content-length:")) == 0) {
				content_length = safe_atoi(&line_buf[strlen("Content-length:")]);
			}
		} while (strcmp(line_buf, "\r\n") != 0);
		/* make sure that it included a Content-length header */
		if (content_length < 0)
			error(EXIT_FAILURE, 0, "did not get frame length");
		/* read the frame contents */
		if ((ssize_t)s->back->cap < s->back->len + content_length)
			s->back->buf = xrealloc(s->back->buf, s->back->cap = s->back->len + content_length);
		if (fread(&s->back->buf[s->back->len], content_length, 1, stream) != 1)
			stdioerror(stream, "src");
		s->back->len += content_length;

		/* swap the frames */
		pthread_rwlock_wrlock(&s->frontlock);
		struct frame *tmp = s->front;
		s->front = s->back;
		s->back = tmp;
		pthread_cond_broadcast(&s->newframe);
		pthread_rwlock_unlock(&s->frontlock);
	}
 end:
	free(boundary);
	free(line_buf);
	fclose(stream);
	return ret;
}

int multipart_replace_writer(struct multipart_replace_stream *s, int fd, const char *_boundary) {
	int ret = 0;
	FILE *stream = fdopen(fd, "w");
	struct frame myframe = { 0 };
	char *boundary = boundary_line(_boundary);
	size_t boundary_len = strlen(boundary);

	while (running) {
		pthread_cond_wait(&s->newframe, &s->newframe_lock);

		/* get the most recent frame (copy `s->front` to `myframe`) */
		pthread_rwlock_rdlock(&s->frontlock);
		if (myframe.cap < (size_t)s->front->len)
			myframe.buf = xrealloc(myframe.buf, myframe.cap = s->front->len);
		memcpy(myframe.buf, s->front->buf, myframe.len = s->front->len);

		pthread_rwlock_unlock(&s->frontlock);

		if (myframe.len != 0) {
			/* send the frame to the client */
			if (fwrite(boundary, boundary_len, 1, stream) < 1)
				stdioerror(stream, "dst <- boundary");
			if (fwrite(myframe.buf, myframe.len, 1, stream) < 1)
				stdioerror(stream, "dst <- frame");
			/* send a blank line for pleasantness */
			if (fwrite("\r\n", 2, 1, stream) < 1)
				stdioerror(stream, "dst <- nl");
			fflush(stream);
		}
	}
 end:
	free(boundary);
	free(myframe.buf);
	fclose(stream);
	return ret;
}

void init_multipart_replace_stream(struct multipart_replace_stream *s) {
	ZERO(s->a);
	ZERO(s->b);
	s->front = &s->a;
	s->back = &s->b;
	pthread_rwlock_init(&s->frontlock, NULL);
	pthread_cond_init(&s->newframe, NULL);
	pthread_mutex_init(&s->newframe_lock, NULL);
}

void destroy_multipart_replace_stream(struct multipart_replace_stream *s) {
	free(s->a.buf);
	free(s->b.buf);
	pthread_rwlock_destroy(&s->frontlock);
	pthread_cond_destroy(&s->newframe);
	pthread_mutex_destroy(&s->newframe_lock);
}