//  date.c

#include "common.h"
#include "cstring.h"
#include "cyber.h"
#include "disk.h"
#include "floating.h"
#include "calend.h"
#include "date.h"

//  Time stored as a ulong is stored in Mac system format, which is the number of
//  seconds since 12:00 a.m., Jan 1, 1904.


//  Date and time functions

static char Calends[]={ 0,3,2,5,0,3,5,1,4,6,2,4 };

  int gregdayofweek(int AD, int MONTH, int DATE) {
if (MONTH<2) AD--;  //  This algorithm was not written by me
return (AD + (AD/4) - (AD/100) + (AD/400) + Calends[MONTH] + DATE) % 7; }

  ulong secssince1904(int YEAR, int MONTH, int DATE, int HOUR) {
DateTimeRec D; ulong T; D.year=YEAR; D.month= MONTH + 1; D.day= DATE + 1;
D.hour=HOUR; D.minute=0; D.second=0; DateToSeconds(&D,&T); return T; }

  ulong currentgmt(void) {
ulong U; MachineLocation ML; long L;
ReadLocation(&ML); L= (ML.u.gmtDelta << 8) >> 8;
GetDateTime(&U); return U - L; }

  void incrementtime(ulong *TIME, char UNIT, long NUM, bool Round) {
DateTimeRec D; if (!TIME) return;
switch (UNIT) {  //  breaks intentionally omitted
  case 'w': NUM*=7; case 'd': NUM*=24; case 'h': NUM*=60; case 'm': NUM*=60;
  case 's': (*TIME)+=NUM; if (!Round) return; SecondsToDate(*TIME,&D); break;
  case 'M': case 'y': SecondsToDate(*TIME,&D); if (UNIT=='y') D.year+=NUM;
            else { D.month+= NUM - 1; D.year+= D.month / 12; D.month%=12;
            if (D.month<0) { D.month+=12; D.year--; } D.month++; }
            if (!Round) { DateToSeconds(&D,TIME); return; } break;
  default: return; }
switch (UNIT) {  //  breaks intentionally omitted
  case 'w': D.day-= D.dayOfWeek - 1;
  case 'd': D.hour=0; case 'h': D.minute=0; case 'm': D.second=0; break;
  case 'y': D.month=1; case 'M': D.day=1; D.hour=0; D.minute=0; D.second=0; }
DateToSeconds(&D,TIME); }


//  Date and time strings

  string timestring(ulong TIME) {
DateTimeRec D; char *S; SecondsToDate(TIME,&D);
S=cat3(5,fig(D.hour),D.minute<10 ? ":0" : ":",fig(D.minute));
return cat3(5,S,D.second<10 ? ":0" : ":",fig(D.second)); }

  string datestring(ulong TIME, bool WeekDay) {
DateTimeRec D; char *S; SecondsToDate(TIME,&D);
S=cat5(17,fig(D.year)," ",monthname(D.month - 1)," ",fig(D.day));
return WeekDay ? cat3(1,S,", ",dayname(D.dayOfWeek - 1)) : S; }


//  Parsing date strings

  bool parseepoch(const char *S, ulong *TIME) {
long Q; DateTimeRec D; if (!S || !TIME) return 0; while (*S==' ') S++;
if (!parseinteger(S,&Q)) return 0; while (numeral(*S)) S++;
if (*(S++)!='.') return 0; if (*(S++)!='0') return 0; if (numeral(*S)) return 0;
if (Q<1905 || Q>2040) return 0;
D.year= Q - 1; D.month=12; D.day=31;  //  ?  confirm
D.hour=0; D.minute=0; D.second=0; DateToSeconds(&D,TIME); return 1; }

  bool parsejuliandate(const char *S, ulong *TIME) {
long Q; if (!S || !TIME) return 0; while (*S==' ') S++;
if (!parseinteger(S,&Q)) return 0; while (numeral(*S)) S++;
if (*(S++)!='.') return 0; if (*(S++)!='5') return 0; if (numeral(*S)) return 0;
Q-=2416480; if (Q<0) return 0; *TIME= Q * (ulong)86400L; return 1; }

  bool parsenoraddate(const char *S, ulong *TIME) {
real Q; char C; DateTimeRec D; if (!S || !TIME) return 0;
while (*S==' ') S++; D.year=1900;
if (!numeral(C=S[0])) return 0; D.year+= 10 * (C - '0');
if (!numeral(C=S[1])) return 0; D.year+= C - '0';
if (D.year<=1940) D.year+=100; S+=2;
if (!parsereal(S,&Q)) return 0;
D.month=1; D.day=(int)Q; Q-=D.day;
Q*=24.0; D.hour=(int)Q; Q-=D.hour;
Q*=60.0; D.minute=(int)Q; Q-=D.minute;
Q*=60.0; D.second=(int)Q; DateToSeconds(&D,TIME); return 1; }