// memmem
#define _GNU_SOURCE

#include <sys/mman.h>
#include <sys/stat.h>
#include <sys/types.h>

#include <errno.h>
#include <fcntl.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
#include <unistd.h>

#include "blaze822.h"
#include "blaze822_priv.h"

#define bufsiz 4096

static long
parse_posint(char **s, size_t minn, size_t maxn)
{
        long n;
        char *end;

        errno = 0;
        n = strtol(*s, &end, 10);
        if (errno) {
//                perror("strtol");
		return -1;
        }
        if (n < (long)minn || n > (long)maxn) {
//                fprintf(stderr, "number outside %zd <= n < %zd\n", minn, maxn);
		return -1;
        }
        *s = end;
        return n;
}

time_t
blaze822_date(char *s) {
	struct tm tm;
	int c;

#if 0
#define i4(m) (s[0] && (s[0]|0x20) == m[0] && \
               s[1] && (s[1]|0x20) == m[1] && \
               s[2] && (s[2]|0x20) == m[2] && \
               s[3] && (s[3]|0x20) == m[3] && (s = s+4) )

#define i3(m) (s[0] && (s[0]|0x20) == m[0] && \
               s[1] && (s[1]|0x20) == m[1] && \
               s[2] && (s[2]|0x20) == m[2] && (s = s+3) )
#endif

#define i4(m) (((uint32_t) m[0]<<24 | m[1]<<16 | m[2]<<8 | m[3]) == \
	       ((uint32_t) s[0]<<24 | s[1]<<16 | s[2]<<8 | s[3] | 0x20202020) \
	       && (s += 4))

#define i3(m) (((uint32_t) m[0]<<24 | m[1]<<16 | m[2]<<8) == \
	       ((uint32_t) s[0]<<24 | s[1]<<16 | s[2]<<8 | 0x20202000) \
	       && (s += 3))

	while (iswsp(*s))
		s++;
	if (i4("mon,") || i4("tue,") || i4("wed,") || i4("thu,") ||
	    i4("fri,") || i4("sat,") || i4("sun,"))
		while (iswsp(*s))
			s++;

	if ((c = parse_posint(&s, 1, 31)) < 0) goto fail;
	tm.tm_mday = c;

	while (iswsp(*s))
		s++;
	
	if      (i3("jan")) tm.tm_mon = 0;
	else if (i3("feb")) tm.tm_mon = 1;
	else if (i3("mar")) tm.tm_mon = 2;
	else if (i3("apr")) tm.tm_mon = 3;
	else if (i3("may")) tm.tm_mon = 4;
	else if (i3("jun")) tm.tm_mon = 5;
	else if (i3("jul")) tm.tm_mon = 6;
	else if (i3("aug")) tm.tm_mon = 7;
	else if (i3("sep")) tm.tm_mon = 8;
	else if (i3("oct")) tm.tm_mon = 9;
	else if (i3("nov")) tm.tm_mon = 10;
	else if (i3("dec")) tm.tm_mon = 11;
	else goto fail;

	while (iswsp(*s))
		s++;
	
	if ((c = parse_posint(&s, 1000, 9999)) > 0) {
		tm.tm_year = c - 1900;
	} else if ((c = parse_posint(&s, 0, 49)) > 0) {
		tm.tm_year = c + 100;
	} else if ((c = parse_posint(&s, 50, 99)) > 0) {
		tm.tm_year = c;
	} else goto fail;

	while (iswsp(*s))
		s++;

	if ((c = parse_posint(&s, 0, 24)) < 0) goto fail;
	tm.tm_hour = c;
	if (*s++ != ':') goto fail;
	if ((c = parse_posint(&s, 0, 59)) < 0) goto fail;
	tm.tm_min = c;
	if (*s++ == ':') {
		if ((c = parse_posint(&s, 0, 61)) < 0) goto fail;
		tm.tm_sec = c;
	} else {
		tm.tm_sec = 0;
	}

	while (iswsp(*s))
		s++;

	if (*s == '+' || *s == '-') {
		int neg = (*s == '-');
		s++;
		if ((c = parse_posint(&s, 0, 10000)) < 0) goto fail;
		if (neg) {
                        tm.tm_hour += c / 100;
                        tm.tm_min  += c % 100;
		} else {
                        tm.tm_hour -= c / 100;
                        tm.tm_min  -= c % 100;
                }
	}

	tm.tm_isdst = -1;

	time_t r = mktime(&tm);
	return r;

fail:
	return -1;
}

char *
blaze822_addr(char *s, char **dispo, char **addro)
{
	static char disp[1024];
	static char addr[1024];
//	char *disp = disp+sizeof disp;
//	char *addr = addr+sizeof addr;
	char *c, *e;

//	printf("RAW : |%s|\n", s);
	
	while (iswsp(*s))
		s++;
	
	c = disp;
	e = disp + sizeof disp;

	*disp = 0;
	*addr = 0;

	while (*s) {
		if (*s == '<') {
			char *c = addr;
			char *e = addr + sizeof addr;

			s++;
			while (*s && c < e && *s != '>')
				*c++ = *s++;
			if (*s == '>')
				s++;
			*c = 0;
		} else if (*s == '"') {
			s++;
			while (*s && c < e && *s != '"')
				*c++ = *s++;
			if (*s == '"')
				s++;
		} else if (*s == '(') {
			s++;

			if (!*addr) {   // assume: user@host (name)
				*c-- = 0;
				while (c > disp && iswsp(*c))
					*c-- = 0;
				strcpy(addr, disp);
				c = disp;
				*c = 0;
			}

			while (*s && c < e && *s != ')')
				*c++ = *s++;
			if (*s == ')')
				s++;
		} else if (*s == ',') {
			s++;
			break;
		} else {
			*c++ = *s++;
		}
	}

	*c-- = 0;
	// strip trailing ws
	while (c > disp && iswsp(*c))
		*c-- = 0;

	if (*disp && !*addr && strchr(disp, '@')) {
		// just mail address was given
		strcpy(addr, disp);
		*disp = 0;
	}

//	printf("DISP :: |%s|\n", disp);
//	printf("ADDR :: |%s|\n", addr);

	if (dispo) *dispo = disp;
	if (addro) *addro = addr;

	return s;
}

static void
compress_hdr(char *s, char *end)
{
	char *t, *h;

	if ((t = h = strchr(s, '\n'))) {
		while (h < end && *h) {
			if (*h == '\n') {
				*t++ = ' ';
				while (*h && isfws(*h))
					h++;
			}
			*t++ = *h++;
		}
		// remove trailing whitespace
		while (s < t && isfws(t[-1]))
			*--t = 0;
		// zero fill gap
		while (t < h)
			*t++ = 0;
	}
}


static void
unfold_hdr(char *buf, char *end)
{
	char *s, *l;
	*end = 0;

	// sanitize all nul in message headers, srsly
	if (memchr(buf, 0, end-buf))
		for (s = buf; s < end; s++)
			if (*s == 0)
				*s = ' ';

	// normalize crlf
	if (memchr(buf, '\r', end-buf))
		for (s = buf; s < end; s++)
			if (*s == '\r') {
				if (*(s+1) == '\n')
					*s = '\n';
				else
					*s = ' ';
			}

	l = buf;
	s = buf;

	while (s < end && *s != ':' && *s != '\n') {
		*s = lc(*s);
		s++;
	}

	while (s < end) {
		s = memchr(s+1, '\n', end-s);
		if (!s)
			break;

		while (s < end && *s == '\n')
			s++;
		if (!iswsp(*s)) {
			*(s-1) = 0;
			compress_hdr(l, s-1);
			l = s;
			while (s < end && *s != ':' && *s != '\n') {
				*s = lc(*s);
				s++;
			}
		}
	}
	compress_hdr(l, end);
}

struct message *
blaze822(char *file)
{
	int fd;
	ssize_t rd;
	char *buf;
	ssize_t bufalloc;
	ssize_t used;
	char *end;

	struct message *mesg = malloc(sizeof (struct message));
	if (!mesg)
		return 0;

	fd = open(file, O_RDONLY);
	if (fd < 0) {
//		perror("open");
		free(mesg);
		return 0;
	}

	buf = 0;
	bufalloc = 0;
	used = 0;

	while (1) {
		int overlap = used > 3 ? 3 : 0;

		bufalloc += bufsiz;
		buf = realloc(buf, bufalloc);
		if (!buf) {
			free(mesg);
			close(fd);
			return 0;
		}

		rd = read(fd, buf+used, bufalloc-used);
		if (rd == 0) {
			end = buf+used;
			break;
		}
		if (rd < 0) {
			free(mesg);
			free(buf);
			close(fd);
			return 0;
		}

		if ((end = memmem(buf-overlap+used, rd+overlap, "\n\n", 2))) {
			end++;
			break;
		}
		if ((end = memmem(buf-overlap+used, rd+overlap, "\r\n\r\n", 4))) {
			end++;
			end++;
			break;
		}

		used += rd;
	}
	close(fd);

	*end = 0;   // dereferencing *end is safe

	unfold_hdr(buf, end);

	mesg->msg = buf;
	mesg->end = end;
	mesg->body = mesg->bodyend = mesg->bodychunk = 0;

	return mesg;
}

struct message *
blaze822_mem(char *src, size_t len)
{
	char *buf;
	char *end;

	struct message *mesg = malloc(sizeof (struct message));
	if (!mesg)
		return 0;

	if ((end = memmem(src, len, "\n\n", 2))) {
		mesg->body = end+2;
	} else if ((end = memmem(src, len, "\r\n\r\n", 4))) {
		mesg->body = end+4;
	} else {
		end = src + len;
		mesg->body = end;
		mesg->bodyend = end;
	}
	if (mesg->body)
		mesg->bodyend = src + len;

	size_t hlen = end - src;

	buf = malloc(hlen+1);
	if (!buf)
		return 0;
	memcpy(buf, src, hlen);

	end = buf+hlen;
	*end = 0;   // dereferencing *end is safe

	unfold_hdr(buf, end);

	mesg->msg = buf;
	mesg->end = end;
	mesg->bodychunk = 0;   // src is not ours

	return mesg;
}

void
blaze822_free(struct message *mesg)
{
	if (!mesg)
		return;
	if (mesg->bodychunk == mesg->msg) {
		munmap(mesg->bodychunk, mesg->bodyend - mesg->msg);
	} else {
		free(mesg->msg);
		free(mesg->bodychunk);
	}
	free(mesg);
}

char *
blaze822_hdr_(struct message *mesg, const char *hdr, size_t hdrlen)
{
	char *v;

	if (hdrlen == 0 || hdrlen-1 >= (size_t)(mesg->end - mesg->msg))
		return 0;  // header too small for the key, probably empty

	// special case: first header, no leading nul
	if (memcmp(mesg->msg, hdr+1, hdrlen-1) == 0)
		v = mesg->msg;
	else
		v = memmem(mesg->msg, mesg->end - mesg->msg, hdr, hdrlen);
	if (!v)
		return 0;
	v += hdrlen;
	while (*v && iswsp(*v))
		v++;
	return v;
}

char *
blaze822_chdr(struct message *mesg, const char *chdr)
{
	char hdr[256];
	size_t l = snprintf(hdr, sizeof hdr, "%c%s:", 0, chdr);

	return blaze822_hdr_(mesg, hdr, l);
}

struct message *
blaze822_file(char *file)
{
	int fd = open(file, O_RDONLY);
	if (fd < 0)
		return 0;

	struct stat st;
	if (fstat(fd, &st) < 0)
		goto error;

	size_t s = st.st_size;

	char *buf = malloc(s+1);
	if (read(fd, buf, s) < 0) {
		// XXX handle short reads?
		perror("read");
		goto error;
	}
	close(fd);

	buf[s] = 0;

	// XXX duplicate header in ram...
	struct message *mesg = blaze822_mem(buf, s);
	if (mesg)
		mesg->bodychunk = buf;
	return mesg;

error:
	close(fd);
	return 0;
}

struct message *
blaze822_mmap(char *file)
{
	int fd = open(file, O_RDONLY);
	if (fd < 0)
		return 0;

	struct stat st;
	if (fstat(fd, &st) < 0)
		goto error;

	size_t len = st.st_size;

	struct message *mesg = malloc(sizeof (struct message));
	if (!mesg)
		goto error;

	char *buf = mmap(0, len+1, PROT_READ | PROT_WRITE, MAP_PRIVATE, fd, 0);
	if (buf == MAP_FAILED) {
		perror("mmap");
		goto error;
	}
	close(fd);

	char *end;
	if ((end = memmem(buf, len, "\n\n", 2))) {
		mesg->body = end+2;
	} else if ((end = memmem(buf, len, "\r\n\r\n", 4))) {
		mesg->body = end+4;
	} else {
		end = buf + len;
		mesg->body = end;
	}

	unfold_hdr(buf, end);

	mesg->msg = mesg->bodychunk = buf;
	mesg->end = end;
	mesg->bodyend = buf + len;

	return mesg;

error:
	close(fd);
	return 0;
}

size_t
blaze822_headerlen(struct message *mesg)
{
	return mesg->end - mesg->msg;
}

char *
blaze822_body(struct message *mesg)
{
	return mesg->body;
}

size_t
blaze822_bodylen(struct message *mesg)
{
	if (!mesg->body || !mesg->bodyend)
		return 0;
	return mesg->bodyend - mesg->body;
}

char *
blaze822_next_header(struct message *mesg, char *prev)
{
	if (!prev) {
		prev = mesg->msg;
	} else {
		if (prev >= mesg->end)
			return 0;
		prev = prev + strlen(prev);
	}
	while (prev < mesg->end && *prev == 0)
		prev++;
	if (prev >= mesg->end)
		return 0;
	return prev;
}