/*
 * Copyright (C) 2003, International Business Machines Corporation
 * and others. All Rights Reserved.
 ******************************************************************************
 *
 * File ISLAMCAL.H
 *
 * Modification History:
 *
 *   Date        Name        Description
 *   10/14/2003  srl         ported from java IslamicCalendar
 *****************************************************************************
 */

#include "islamcal.h"

#if !UCONFIG_NO_FORMATTING

#include "mutex.h"
#include <float.h>
#include "gregoimp.h" // Math
#include "astro.h" // CalendarAstronomer
#include "uhash.h"

static const UDate HIJRA_MILLIS = -42521587200000.0;    // 7/16/622 AD 00:00

// Debugging
#ifdef U_DEBUG_ISLAMCAL
# include <stdio.h>
# include <stdarg.h>
static void debug_islamcal_loc(const char *f, int32_t l)
{
  fprintf(stderr, "%s:%d: ", f, l);
}

static void debug_islamcal_msg(const char *pat, ...)
{
  va_list ap;
  va_start(ap, pat);
  vfprintf(stderr, pat, ap);
  fflush(stderr);
}
// must use double parens, i.e.:  U_DEBUG_ISLAMCAL_MSG(("four is: %d",4));
#define U_DEBUG_ISLAMCAL_MSG(x) {debug_islamcal_loc(__FILE__,__LINE__);debug_islamcal_msg x;}
#else
#define U_DEBUG_ISLAMCAL_MSG(x)
#endif


// --- The cache --
// cache of months
static UMTX astroLock = 0;  // pod bay door lock
static UHashtable *monthCache = NULL;

static void createCache(UErrorCode &success) {
  if(monthCache == NULL) {
    monthCache = uhash_openSize(uhash_hashLong, uhash_compareLong, 32, &success);
  }
}

/**
 * Delete the cache, clean up. 
 * called by calendar_islamic_cleanup()
 */
static void deleteCache() {
  if(monthCache != NULL) {
    uhash_close(monthCache);
    monthCache = NULL;
  }
  umtx_destroy(&astroLock);
  astroLock = NULL;
}

static void putCache(int32_t month, int32_t start, UErrorCode &status) {
  umtx_lock(&astroLock);
  uhash_puti(monthCache, (void*)month, start, &status);
  U_DEBUG_ISLAMCAL_MSG(("Add: m%d, st%d\n", month, start));
  umtx_unlock(&astroLock);
}

int32_t getCache(int32_t month, UBool& found, UErrorCode &success) {
  int32_t res = 0;

  umtx_lock(&astroLock);
  if(monthCache == NULL) {
    createCache(success);
  }
  
  res = uhash_geti(monthCache, (void*)month);
  
  umtx_unlock(&astroLock);
  if(res!=0) { 
    found=TRUE;
  } else { 
    found=FALSE;
  }
  
  U_DEBUG_ISLAMCAL_MSG(("Get: m%d, res%d, found%s\n", month, res, found?"Y":"N"));
  return res;
}

U_NAMESPACE_BEGIN

// Implementation of the IslamicCalendar class

//-------------------------------------------------------------------------
// Constructors...
//-------------------------------------------------------------------------

const char *IslamicCalendar::getType() const { 
  if(civil==CIVIL) {
    return "islamic-civil";
  } else {
    return "islamic";
  }
}

Calendar* IslamicCalendar::clone() const {
  return new IslamicCalendar(*this);
}

IslamicCalendar::IslamicCalendar(const Locale& aLocale, UErrorCode& success, ECivil beCivil)
  :   Calendar(TimeZone::createDefault(), aLocale, success),
      civil(beCivil)
{
  setTimeInMillis(getNow(), success); // Call this again now that the vtable is set up properly.
}

IslamicCalendar::IslamicCalendar(const IslamicCalendar& other) : Calendar(other), civil(other.civil) {
}

IslamicCalendar::~IslamicCalendar()
{
}

/**
 * Determines whether this object uses the fixed-cycle Islamic civil calendar
 * or an approximation of the religious, astronomical calendar.
 *
 * @param beCivil   <code>true</code> to use the civil calendar,
 *                  <code>false</code> to use the astronomical calendar.
 * @draft ICU 2.4
 */
void IslamicCalendar::setCivil(ECivil beCivil, UErrorCode &status)
{
  if (civil != beCivil) {
    // The fields of the calendar will become invalid, because the calendar
    // rules are different
    UDate m = getTimeInMillis(status);
    civil = beCivil;
    clear();
    setTimeInMillis(m, status);
  }
}
    
/**
 * Returns <code>true</code> if this object is using the fixed-cycle civil
 * calendar, or <code>false</code> if using the religious, astronomical
 * calendar.
 * @draft ICU 2.4
 */
UBool IslamicCalendar::isCivil() {
  return (civil == CIVIL);
}
    
//-------------------------------------------------------------------------
// Minimum / Maximum access functions
//-------------------------------------------------------------------------

static const int32_t LIMITS[UCAL_FIELD_COUNT][4] = {
  // Minimum  Greatest    Least  Maximum
  //           Minimum  Maximum
  {        0,        0,       0,       0 }, // ERA
  {        1,        1, 5000000, 5000000 }, // YEAR
  {        0,        0,      11,      11 }, // MONTH
  {        1,        1,      51,      52 }, // WEEK_OF_YEAR
  {        0,        0,       5,       6 }, // WEEK_OF_MONTH
  {        1,        1,      29,      30 }, // DAY_OF_MONTH
  {        1,        1,     354,     355 }, // DAY_OF_YEAR
  {/*N/A*/-1,/*N/A*/-1,/*N/A*/-1,/*N/A*/-1}, // DAY_OF_WEEK
  {       -1,       -1,       4,       5 }, // DAY_OF_WEEK_IN_MONTH
  {/*N/A*/-1,/*N/A*/-1,/*N/A*/-1,/*N/A*/-1}, // AM_PM
  {/*N/A*/-1,/*N/A*/-1,/*N/A*/-1,/*N/A*/-1}, // HOUR
  {/*N/A*/-1,/*N/A*/-1,/*N/A*/-1,/*N/A*/-1}, // HOUR_OF_DAY
  {/*N/A*/-1,/*N/A*/-1,/*N/A*/-1,/*N/A*/-1}, // MINUTE
  {/*N/A*/-1,/*N/A*/-1,/*N/A*/-1,/*N/A*/-1}, // SECOND
  {/*N/A*/-1,/*N/A*/-1,/*N/A*/-1,/*N/A*/-1}, // MILLISECOND
  {/*N/A*/-1,/*N/A*/-1,/*N/A*/-1,/*N/A*/-1}, // ZONE_OFFSET
  {/*N/A*/-1,/*N/A*/-1,/*N/A*/-1,/*N/A*/-1}, // DST_OFFSET
  { -5000001, -5000001, 5000001, 5000001 }, // YEAR_WOY
  {/*N/A*/-1,/*N/A*/-1,/*N/A*/-1,/*N/A*/-1}, // DOW_LOCAL
  { -5000000, -5000000, 5000000, 5000000 }, // EXTENDED_YEAR
  {/*N/A*/-1,/*N/A*/-1,/*N/A*/-1,/*N/A*/-1}, // JULIAN_DAY
  {/*N/A*/-1,/*N/A*/-1,/*N/A*/-1,/*N/A*/-1} // MILLISECONDS_IN_DAY
};

/**
 * @draft ICU 2.4
 */
int32_t IslamicCalendar::handleGetLimit(UCalendarDateFields field, ELimitType limitType) const {
  return LIMITS[field][limitType];
}

//-------------------------------------------------------------------------
// Assorted calculation utilities
//

/**
 * Determine whether a year is a leap year in the Islamic civil calendar
 */
UBool IslamicCalendar::civilLeapYear(int32_t year)
{
  return (14 + 11 * year) % 30 < 11;
}
    
/**
 * Return the day # on which the given year starts.  Days are counted
 * from the Hijri epoch, origin 0.
 */
int32_t IslamicCalendar::yearStart(int32_t year) {
  if (civil == CIVIL) {
    return (year-1)*354 + Math::floorDivide((3+11*year),30);
  } else {
    return trueMonthStart(12*(year-1));
  }
}
    
/**
 * Return the day # on which the given month starts.  Days are counted
 * from the Hijri epoch, origin 0.
 *
 * @param year  The hijri year
 * @param year  The hijri month, 0-based
 */
int32_t IslamicCalendar::monthStart(int32_t year, int32_t month) const {
  if (civil == CIVIL) {
    return (int32_t)uprv_ceil(29.5*month)
      + (year-1)*354 + (int32_t)Math::floorDivide((3+11*year),30);
  } else {
    return trueMonthStart(12*(year-1) + month);
  }
}
    
/**
 * Find the day number on which a particular month of the true/lunar
 * Islamic calendar starts.
 *
 * @param month The month in question, origin 0 from the Hijri epoch
 *
 * @return The day number on which the given month starts.
 */
int32_t IslamicCalendar::trueMonthStart(int32_t month) const
{
  UBool found;
  UErrorCode status = U_ZERO_ERROR;
  int32_t start = getCache(month, found, status);
  
  if (found==FALSE) {
    // Make a guess at when the month started, using the average length
    UDate origin = HIJRA_MILLIS 
      + uprv_floor(month * CalendarAstronomer::SYNODIC_MONTH - 1) * kOneDay;
    
    double age = moonAge(origin);
    
    if (moonAge(origin) >= 0) {
      // The month has already started
      do {
        origin -= kOneDay;
        age = moonAge(origin);
      } while (age >= 0);
    }
    else {
      // Preceding month has not ended yet.
      do {
          origin += kOneDay;
        age = moonAge(origin);
      } while (age < 0);
    }
    start = (int32_t)Math::floorDivide((origin - HIJRA_MILLIS), (double)kOneDay) + 1;
    putCache(month, start, status);
  }
  if(U_FAILURE(status)) {
    start = 0;
  }
  return start;
}

/**
 * Return the "age" of the moon at the given time; this is the difference
 * in ecliptic latitude between the moon and the sun.  This method simply
 * calls CalendarAstronomer.moonAge, converts to degrees, 
 * and adjusts the result to be in the range [-180, 180].
 *
 * @param time  The time at which the moon's age is desired,
 *              in millis since 1/1/1970.
 */
double IslamicCalendar::moonAge(UDate time)
{
  double age = 0;
  static CalendarAstronomer *astro = NULL;

  umtx_lock(&astroLock);
  if(astro == NULL) {
    astro = new CalendarAstronomer();
  }
  astro->setTime(time);
  age = astro->getMoonAge();
  umtx_unlock(&astroLock);

  // Convert to degrees and normalize...
  age = age * 180 / CalendarAstronomer::PI;
  if (age > 180) {
    age = age - 360;
  }

  return age;
}

//----------------------------------------------------------------------
// Calendar framework
//----------------------------------------------------------------------

/**
 * Return the length (in days) of the given month.
 *
 * @param year  The hijri year
 * @param year  The hijri month, 0-based
 * @draft ICU 2.4
 */
int32_t IslamicCalendar::handleGetMonthLength(int32_t extendedYear, int32_t month) const {

  int32_t length = 0;
        
  if (civil == CIVIL) {
    length = 29 + (month+1) % 2;
    if (month == DHU_AL_HIJJAH && civilLeapYear(extendedYear)) {
      length++;
    }
  } else {
    month = 12*(extendedYear-1) + month;
    length =  trueMonthStart(month+1) - trueMonthStart(month) ;
  }
  return length;
}

/**
 * Return the number of days in the given Islamic year
 * @draft ICU 2.4
 */
int32_t IslamicCalendar::handleGetYearLength(int32_t extendedYear) const {
  if (civil == CIVIL) {
    return 354 + (civilLeapYear(extendedYear) ? 1 : 0);
  } else {
    int32_t month = 12*(extendedYear-1);
    return (trueMonthStart(month + 12) - trueMonthStart(month));
  }
}
    
//-------------------------------------------------------------------------
// Functions for converting from field values to milliseconds....
//-------------------------------------------------------------------------

// Return JD of start of given month/year
/**
 * @draft ICU 2.4
 */
int32_t IslamicCalendar::handleComputeMonthStart(int32_t eyear, int32_t month, UBool /* useMonth */) const {
  return monthStart(eyear, month) + 1948439;
}    

//-------------------------------------------------------------------------
// Functions for converting from milliseconds to field values
//-------------------------------------------------------------------------

    /**
     * @draft ICU 2.4
     */
int32_t IslamicCalendar::handleGetExtendedYear() {
    int32_t year;
    if (newerField(UCAL_EXTENDED_YEAR, UCAL_YEAR) == UCAL_EXTENDED_YEAR) {
        year = internalGet(UCAL_EXTENDED_YEAR, 1); // Default to year 1
    } else {
        year = internalGet(UCAL_YEAR, 1); // Default to year 1
    }
    return year;
}

/**
 * Override Calendar to compute several fields specific to the Islamic
 * calendar system.  These are:
 *
 * <ul><li>ERA
 * <li>YEAR
 * <li>MONTH
 * <li>DAY_OF_MONTH
 * <li>DAY_OF_YEAR
 * <li>EXTENDED_YEAR</ul>
 * 
 * The DAY_OF_WEEK and DOW_LOCAL fields are already set when this
 * method is called. The getGregorianXxx() methods return Gregorian
 * calendar equivalents for the given Julian day.
     * @draft ICU 2.4
     */
void IslamicCalendar::handleComputeFields(int32_t julianDay, UErrorCode &/*status*/) {
    int32_t year, month, dayOfMonth, dayOfYear;
    UDate startDate;
    int32_t days = julianDay - 1948440;
    
    if (civil == CIVIL) {
        // Use the civil calendar approximation, which is just arithmetic
        year  = (int)Math::floorDivide( (double)(30 * days + 10646) , 10631.0 );
        month = (int32_t)uprv_ceil((days - 29 - yearStart(year)) / 29.5 );
        month = month<11?month:11;
        startDate = monthStart(year, month);
    } else {
        // Guess at the number of elapsed full months since the epoch
        int32_t months = (int32_t)uprv_floor((double)days / CalendarAstronomer::SYNODIC_MONTH);

        startDate = uprv_floor(months * CalendarAstronomer::SYNODIC_MONTH - 1);

        if ( days - startDate >= 28 && moonAge(internalGetTime()) > 0) {
            // If we're near the end of the month, assume next month and search backwards
            months++;
        }

        // Find out the last time that the new moon was actually visible at this longitude
        // This returns midnight the night that the moon was visible at sunset.
        while ((startDate = trueMonthStart(months)) > days) {
            // If it was after the date in question, back up a month and try again
            months--;
        }
        
        year = months / 12 + 1;
        month = months % 12;
    }
    
    dayOfMonth = (days - monthStart(year, month)) + 1;

    // Now figure out the day of the year.
    dayOfYear = (days - monthStart(year, 0) + 1);

    internalSet(UCAL_ERA, 0);
    internalSet(UCAL_YEAR, year);
    internalSet(UCAL_EXTENDED_YEAR, year);
    internalSet(UCAL_MONTH, month);
    internalSet(UCAL_DAY_OF_MONTH, dayOfMonth);
    internalSet(UCAL_DAY_OF_YEAR, dayOfYear);       
}    

UBool
IslamicCalendar::inDaylightTime(UErrorCode& status) const
{
// copied from GregorianCalendar
if (U_FAILURE(status) || !getTimeZone().useDaylightTime()) 
  return FALSE;

    // Force an update of the state of the Calendar.
((IslamicCalendar*)this)->complete(status); // cast away const

return (UBool)(U_SUCCESS(status) ? (internalGet(UCAL_DST_OFFSET) != 0) : FALSE);
}

// default century
const UDate     IslamicCalendar::fgSystemDefaultCentury        = DBL_MIN;
const int32_t   IslamicCalendar::fgSystemDefaultCenturyYear    = -1;

UDate           IslamicCalendar::fgSystemDefaultCenturyStart       = DBL_MIN;
int32_t         IslamicCalendar::fgSystemDefaultCenturyStartYear   = -1;


UBool IslamicCalendar::haveDefaultCentury() const
{
  return TRUE;
}

UDate IslamicCalendar::defaultCenturyStart() const
{
  return internalGetDefaultCenturyStart();
}

int32_t IslamicCalendar::defaultCenturyStartYear() const
{
  return internalGetDefaultCenturyStartYear();
}

UDate
IslamicCalendar::internalGetDefaultCenturyStart() const
{
  // lazy-evaluate systemDefaultCenturyStart
  UBool needsUpdate;
  { 
    Mutex m;
    needsUpdate = (fgSystemDefaultCenturyStart == fgSystemDefaultCentury);
  }

  if (needsUpdate) {
    initializeSystemDefaultCentury();
  }

  // use defaultCenturyStart unless it's the flag value;
  // then use systemDefaultCenturyStart
  
  return fgSystemDefaultCenturyStart;
}

int32_t
IslamicCalendar::internalGetDefaultCenturyStartYear() const
{
  // lazy-evaluate systemDefaultCenturyStartYear
  UBool needsUpdate;
  { 
    Mutex m;
    needsUpdate = (fgSystemDefaultCenturyStart == fgSystemDefaultCentury);
  }

  if (needsUpdate) {
    initializeSystemDefaultCentury();
  }

  // use defaultCenturyStart unless it's the flag value;
  // then use systemDefaultCenturyStartYear
  
  return    fgSystemDefaultCenturyStartYear;
}

void
IslamicCalendar::initializeSystemDefaultCentury()
{
  // initialize systemDefaultCentury and systemDefaultCenturyYear based
  // on the current time.  They'll be set to 80 years before
  // the current time.
  // No point in locking as it should be idempotent.
  if (fgSystemDefaultCenturyStart == fgSystemDefaultCentury)
  {
    UErrorCode status = U_ZERO_ERROR;
    Calendar *calendar = new IslamicCalendar(Locale("ar@calendar=islamic-civil"),status);
    if (calendar != NULL && U_SUCCESS(status))
    {
      calendar->setTime(Calendar::getNow(), status);
      calendar->add(UCAL_YEAR, -80, status);
      UDate    newStart =  calendar->getTime(status);
      int32_t  newYear  =  calendar->get(UCAL_YEAR, status);
      {
        Mutex m;
        fgSystemDefaultCenturyStart = newStart;
        fgSystemDefaultCenturyStartYear = newYear;
      }
      delete calendar;
    }
    // We have no recourse upon failure unless we want to propagate the failure
    // out.
  }
}

UOBJECT_DEFINE_RTTI_IMPLEMENTATION(IslamicCalendar)


U_NAMESPACE_END

U_CFUNC UBool calendar_islamic_cleanup(void) {
  deleteCache();
  return TRUE;
}

#endif