#include <regexp.h>

#include <u.h>
#include <libc.h>
#include <bio.h>
#include <regexp.h>
#include <ctype.h>

typedef struct Date Date;
struct Date {
Reprog *p; /* an RE to match this date */
Date *next; /* pointer to next in list */
};

enum{
Secondsperday = 24*60*60
};

Biobuf in;
int debug, matchyear;

Date *dates(Date**, Tm*);
void upper2lower(char*, char*, int);
void *alloc(unsigned int);

void
main(int argc, char *argv[])
{
int i, fd;
long now;
char *line;
Tm *tm;
Date *first, *last, *d;
char buf[1024];

ARGBEGIN{
case 'y':
matchyear = 1;
break;
case 'd':
debug = 1;
break;
default:
fprint(2, "usage: calendar [-d] [files ...]\n");
exits("usage");
}ARGEND;

/* make a list of dates */
now = time(0);
tm = localtime(now);
first = dates(&last, tm);
now += Secondsperday;
tm = localtime(now);
dates(&last, tm);
if(tm->wday == 6){
now += Secondsperday;
tm = localtime(now);
dates(&last, tm);
}
if(tm->wday == 0){
now += Secondsperday;
tm = localtime(now);
dates(&last, tm);
}

for(i=0; i<argc || (i==0 && argc==0); i++){
if(i==0 && argc==0)
snprint(buf, sizeof(buf),
"/usr/%s/lib/calendar", getuser());
else
strcpy(buf, argv[i]);
fd = open(buf, OREAD);
if(fd<0 || Binit(&in, fd, OREAD)<0){
fprint(2, "calendar: can't open %s: %r\n", buf);
exits("open");
}

/* go through the file */
while(line = Brdline(&in, '\n')){
line[Blinelen(&in) - 1] = 0;
upper2lower(buf, line, sizeof buf);
for(d=first; d; d=d->next)
if(regexec(d->p, buf, 0, 0)){
print("%s\n", line);
break;
}
}
close(fd);
}
exits("");
}

char *months[] =
{
"january",
"february",
"march",
"april",
"may",
"june",
"july",
"august",
"september",
"october",
"november",
"december"
};

/*
* Generate two Date structures. First has month followed by day;
* second has day followed by month. Link them into list after
* last, and return the first.
*/
Date*
dates(Date **last, Tm *tm)
{
Date *first;
Date *nd;
char mo[128], buf[128];

if(utflen(months[tm->mon]) > 3)
snprint(mo, sizeof mo, "%3.3s(%s)?",
months[tm->mon], months[tm->mon]+3);
else
snprint(mo, sizeof mo, "%3.3s", months[tm->mon]);
if (matchyear)
snprint(buf, sizeof buf,
"(^| |\t)((%s( |\t)+)|(%d/))%d( |\t|$)(((%d|%d)( |\t|$))|[^0-9]|([0-9]+[^0-9 \t]))",
mo, tm->mon+1, tm->mday, tm->year+1900, tm->year%100);
else
snprint(buf, sizeof buf,
"(^| |\t)((%s( |\t)+)|(%d/))%d( |\t|$)",
mo, tm->mon+1, tm->mday);
if(debug)
print("%s\n", buf);

first = alloc(sizeof(Date));
if(*last)
(*last)->next = first;
first->p = regcomp(buf);

if (matchyear)
snprint(buf, sizeof buf,
"(^| |\t)%d( |\t)+(%s)( |\t|$)(((%d|%d)( |\t|$))|[^0-9]|([0-9]+[^0-9 \t]))",
tm->mday, mo, tm->year+1900, tm->year%100);
else
snprint(buf, sizeof buf,
"(^| |\t)%d( |\t)+(%s)( |\t|$)",
tm->mday, mo);
if(debug)
print("%s\n", buf);
nd = alloc(sizeof(Date));
nd->p = regcomp(buf);
nd->next = 0;
first->next = nd;
*last = nd;

return first;
}

/*
* Copy 'from' to 'to', converting to lower case
*/
void
upper2lower(char *to, char *from, int len)
{
while(--len>0 && *from!='\0')
*to++ = tolower(*from++);
*to = 0;
}

/*
* Call malloc and check for errors
*/
void*
alloc(unsigned int n)
{
void *p;

p = malloc(n);
if(p == 0){
fprint(2, "calendar: malloc failed: %r\n");
exits("malloc");
}
return p;
}