class SolarEventCalculator

# File lib/solareventcalculator.rb, line 7
def initialize(date, latitude, longitude)
  @date = date
  @latitude = latitude
  @longitude = longitude
end

# File lib/solareventcalculator.rb, line 186
def compute_astronomical_sunrise(timezone)
  put_in_timezone(compute_utc_solar_event(108, true), timezone)
end

# File lib/solareventcalculator.rb, line 190
def compute_astronomical_sunset(timezone)
  put_in_timezone(compute_utc_solar_event(108, false), timezone)
end

# File lib/solareventcalculator.rb, line 162
def compute_civil_sunrise(timezone)
  put_in_timezone(compute_utc_solar_event(96, true), timezone)
end

# File lib/solareventcalculator.rb, line 166
def compute_civil_sunset(timezone)
  put_in_timezone(compute_utc_solar_event(96, false), timezone)
end

# File lib/solareventcalculator.rb, line 63
def compute_cosine_sun_declination(sinSunDeclination)
  cosDec = BigDecimal(Math.cos(Math.asin(sinSunDeclination)).to_s)
  cosDec.round(4)
end

# File lib/solareventcalculator.rb, line 68
def compute_cosine_sun_local_hour(sunTrueLong, zenith)
  cosZenith = BigDecimal(Math.cos(degrees_as_rads(BigDecimal(zenith.to_s))).to_s)
  sinLatitude = BigDecimal(Math.sin(degrees_as_rads(@latitude)).to_s)
  cosLatitude = BigDecimal(Math.cos(degrees_as_rads(@latitude)).to_s)

  sinSunDeclination = compute_sin_sun_declination(sunTrueLong)
  top = cosZenith - (sinSunDeclination * sinLatitude)
  bottom = compute_cosine_sun_declination(sinSunDeclination) * cosLatitude

  cosLocalHour = top / bottom
  cosLocalHour.round(4)
end

# File lib/solareventcalculator.rb, line 13
def compute_lnghour
  lngHour = @longitude / BigDecimal("15")
  lngHour.round(4)
end

# File lib/solareventcalculator.rb, line 81
def compute_local_hour_angle(cosSunLocalHour, isSunrise)
  acosH = BigDecimal(Math.acos(cosSunLocalHour).to_s)
  acosHDegrees = rads_as_degrees(acosH)

  localHourAngle = (isSunrise) ? BigDecimal("360") - acosHDegrees : acosHDegrees
  localHourAngle = localHourAngle / BigDecimal("15")
  localHourAngle.round(4)
end

# File lib/solareventcalculator.rb, line 90
def compute_local_mean_time(sunTrueLong, longHour, t,  sunLocalHour)
  h = sunLocalHour
  ra = put_ra_in_correct_quadrant(sunTrueLong)

  parens = BigDecimal("0.06571") * t
  time = h + ra - parens - BigDecimal("6.622")

  utcTime = time - longHour
  utcTime = put_in_range(utcTime, 0, 24, 24)
  utcTime.round(4)
end

# File lib/solareventcalculator.rb, line 18
def compute_longitude_hour(isSunrise)
  minuend = (isSunrise) ? BigDecimal("6") : BigDecimal("18")
  longHour = @date.yday + ((minuend - compute_lnghour) / BigDecimal("24"))
  longHour.round(4)
end

# File lib/solareventcalculator.rb, line 178
def compute_nautical_sunrise(timezone)
  put_in_timezone(compute_utc_solar_event(102, true), timezone)
end

# File lib/solareventcalculator.rb, line 182
def compute_nautical_sunset(timezone)
  put_in_timezone(compute_utc_solar_event(102, false), timezone)
end

# File lib/solareventcalculator.rb, line 170
def compute_official_sunrise(timezone)
  put_in_timezone(compute_utc_solar_event(90.8333, true), timezone)
end

# File lib/solareventcalculator.rb, line 174
def compute_official_sunset(timezone)
  put_in_timezone(compute_utc_solar_event(90.8333, false), timezone)
end

# File lib/solareventcalculator.rb, line 40
def compute_right_ascension(sunTrueLong)
  tanL = BigDecimal(Math.tan(degrees_as_rads(sunTrueLong).to_f).to_s)
  ra = rads_as_degrees(BigDecimal(Math.atan(BigDecimal("0.91764") * tanL).to_s))

  ra = put_in_range(ra, 0, 360, 360)
  ra.round(4)
end

# File lib/solareventcalculator.rb, line 57
def compute_sin_sun_declination(sunTrueLong)
  sinL = BigDecimal(Math.sin(degrees_as_rads(sunTrueLong).to_f).to_s)
  sinDec = sinL * BigDecimal("0.39782")
  sinDec.round(4)
end

# File lib/solareventcalculator.rb, line 24
def compute_sun_mean_anomaly(longHour)
  constant = BigDecimal("0.9856")
  ((longHour * constant) - BigDecimal("3.289")).round(4)
end

# File lib/solareventcalculator.rb, line 29
def compute_sun_true_longitude(meanAnomaly)
  mAsRads = degrees_as_rads(meanAnomaly)
  sinM = BigDecimal(Math.sin(mAsRads.to_f).to_s)
  sinTwoM = BigDecimal(Math.sin((2 * mAsRads).to_f).to_s)
  firstParens = BigDecimal("1.916") * sinM
  secondParens = BigDecimal("0.020") * sinTwoM
  trueLong = meanAnomaly + firstParens + secondParens + BigDecimal("282.634")
  trueLong = put_in_range(trueLong, 0, 360, 360)
  trueLong.round(4)
end

# File lib/solareventcalculator.rb, line 150
def compute_utc_astronomical_sunrise
  convert_to_datetime(compute_utc_solar_event(108, true))
end

# File lib/solareventcalculator.rb, line 154
def compute_utc_astronomical_sunset
  convert_to_datetime(compute_utc_solar_event(108, false))
end

# File lib/solareventcalculator.rb, line 126
def compute_utc_civil_sunrise
  convert_to_datetime(compute_utc_solar_event(96, true))
end

# File lib/solareventcalculator.rb, line 130
def compute_utc_civil_sunset
  convert_to_datetime(compute_utc_solar_event(96, false))
end

# File lib/solareventcalculator.rb, line 142
def compute_utc_nautical_sunrise
  convert_to_datetime(compute_utc_solar_event(102, true))
end

# File lib/solareventcalculator.rb, line 146
def compute_utc_nautical_sunset
  convert_to_datetime(compute_utc_solar_event(102, false))
end

# File lib/solareventcalculator.rb, line 134
def compute_utc_official_sunrise
  convert_to_datetime(compute_utc_solar_event(90.8333, true))
end

# File lib/solareventcalculator.rb, line 138
def compute_utc_official_sunset
  convert_to_datetime(compute_utc_solar_event(90.8333, false))
end

# File lib/solareventcalculator.rb, line 102
def compute_utc_solar_event(zenith, isSunrise)
  longHour = compute_lnghour
  eventLongHour = compute_longitude_hour(isSunrise)

  meanAnomaly = compute_sun_mean_anomaly(eventLongHour)
  sunTrueLong = compute_sun_true_longitude(meanAnomaly)
  cosineSunLocalHour = compute_cosine_sun_local_hour(sunTrueLong, zenith)

  if(cosineSunLocalHour > BigDecimal("1") || cosineSunLocalHour < BigDecimal("-1"))
    return nil
  end

  sunLocalHour = compute_local_hour_angle(cosineSunLocalHour, isSunrise)
  localMeanTime = compute_local_mean_time(sunTrueLong, longHour, eventLongHour, sunLocalHour)

  timeParts = localMeanTime.to_f.to_s.split('.')
  mins = BigDecimal("." + timeParts[1]) * BigDecimal("60")
  mins = mins.truncate()
  mins = pad_minutes(mins.to_i)
  hours = timeParts[0]

  Time.utc(@date.year, @date.mon, @date.mday, hours, pad_minutes(mins.to_i))
end

# File lib/solareventcalculator.rb, line 158
def convert_to_datetime(time)
  DateTime.parse("#{@date.strftime}T#{time.hour}:#{time.min}:00+0000") unless time == nil
end

# File lib/solareventcalculator.rb, line 232
def degrees_as_rads(degrees)
  pi = BigDecimal(Math::PI.to_s)
  radian = pi / BigDecimal("180")
  degrees * radian
end

# File lib/solareventcalculator.rb, line 208
def get_utc_offset(timezone)
  tz = TZInfo::Timezone.get(timezone)
  noonUTC = Time.gm(@date.year, @date.mon, @date.mday, 12, 0)
  tz.utc_to_local(noonUTC) - noonUTC
end

# File lib/solareventcalculator.rb, line 214
def pad_minutes(minutes)
  if(minutes < 10)
    "0" + minutes.to_s
  else
    minutes
  end
end

# File lib/solareventcalculator.rb, line 222
def put_in_range(number, lower, upper, adjuster)
  if number > upper then
    number -= adjuster
  elsif number < lower then
    number += adjuster
  else
    number
  end
end

# File lib/solareventcalculator.rb, line 194
def put_in_timezone(utcTime, timezone)
  tz = TZInfo::Timezone.get(timezone)
  # puts "UTCTime #{utcTime}"
  local = utcTime + get_utc_offset(timezone)
  # puts "LocalTime #{local}"

  offset = (get_utc_offset(timezone) / 60 / 60).to_i
  offset = (offset > 0) ? "+" + offset.to_s : offset.to_s

  timeInZone = DateTime.parse("#{@date.strftime}T#{local.strftime('%H:%M:%S')}#{offset}")
  # puts "CALC:timeInZone #{timeInZone}"
  timeInZone
end

# File lib/solareventcalculator.rb, line 48
def put_ra_in_correct_quadrant(sunTrueLong)
  lQuadrant = BigDecimal("90") * (sunTrueLong / BigDecimal("90")).floor
  raQuadrant = BigDecimal("90") * (compute_right_ascension(sunTrueLong) / BigDecimal("90")).floor

  ra = compute_right_ascension(sunTrueLong) + (lQuadrant - raQuadrant)
  ra = ra / BigDecimal("15")
  ra.round(4)
end

# File lib/solareventcalculator.rb, line 238
def rads_as_degrees(radians)
  pi = BigDecimal(Math::PI.to_s)
  degree = BigDecimal("180") / pi
  radians * degree
end