/* Copyright 2016 Luke Shumaker */

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

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

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);
}

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

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

	while (1) {
		content_length = -1;
		/* scan for the first non-empty line */
		do {
			line_len = getline(&line_buf, &line_cap, stream);
			if (line_len < 0) {
				error(0, 0, "source hung up");
				return;
			}
		} while (strcmp(line_buf, "\r\n") == 0);
		/* make sure it matches the boundary separator */
		if (strcmp(line_buf, boundary) != 0) {
			error(0, 0, "line does not match boundary: \"%s\"", line_buf);
			return;
		}
		/* read the frame header (MIME headers) */
		do {
			line_len = getline(&line_buf, &line_cap, stream);
			if (line_len < 0) {
				error(0, 0, "source hung up");
				return;
			}
			/* 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(0, 0, "did not get frame length");
			return;
		}
		/* 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) {
			error(0, ferror(stream), "fread(%zd)", s->back->len);
			return;
		}
		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;
		s->framecount++;
		pthread_rwlock_unlock(&s->frontlock);
	}
}

void multipart_replace_writer(struct multipart_replace_stream *s, int fd, const char *boundary) {
	struct frame myframe = { 0 };
	long lastframe = 0;
	boundary = boundary_line(boundary);
	size_t boundary_len = strlen(boundary);

	while(1) {
		/* poll until there's a new frame */
		pthread_rwlock_rdlock(&s->frontlock);
		while (s->framecount == lastframe) {
			pthread_rwlock_unlock(&s->frontlock);
			usleep(30000); /* a bit over 30 FPS */
			pthread_rwlock_rdlock(&s->frontlock);
		}

		/* get the most recent frame (copy `s->front` to `myframe`) */
		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);
		lastframe = s->framecount;

		pthread_rwlock_unlock(&s->frontlock);

		/* send the frame to the client */
		if (write(fd, boundary, boundary_len) < (ssize_t)boundary_len) {
			error(0, errno, "write");
			return;
		}
		if (write(fd, myframe.buf, myframe.len) < myframe.len) {
			error(0, errno, "write");
			return;
		}
		/* send a blank line for pleasantness */
		if (write(fd, "\r\n", 2) < 2) {
			error(0, errno, "write");
			return;
		}
	}
}

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);
}