// Javascript Solar Eclipse Explorer
//
// This code is being released under the terms of the GNU General Public
// License (http://www.gnu.org/copyleft/gpl.html) with the request that if
// you do improve on it or use it in your own site, please let us know at
// chris@obyrne.com  and  fred.espenak@nasa.gov    Thanks!
//
//http://eclipse.gsfc.nasa.gov/JSEX/JSEX-index.html
//
/*
Javascript Solar Eclipse Explorer
Version 1 by Chris O'Byrne and Fred Espenak - 2007.
(based on "Eclipse Calculator" by Chris O'Byrne and Stephen McCann - 2003)

This program is free software; you can redistribute it and/or
modify it under the terms of the GNU General Public License
as published by the Free Software Foundation; either version 2
of the License, or (at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.
*/


//
// Observer constants -
// (0) North Latitude (radians)
// (1) West Longitude (radians)
// (2) Altitude (metres)
// (3) West time zone (hours)
// (4) rho sin O'
// (5) rho cos O'
// (6) index into the elements array for the eclipse in question
//
// Note that correcting for refraction will involve creating a "virtual" altitude
// for each contact, and hence a different value of rho and O' for each contact!
//
var obsvconst = new Array();

//
// Eclipse circumstances
//  (0) Event type (C1=-2, C2=-1, Mid=0, C3=1, C4=2)
//  (1) t
// -- time-only dependent circumstances (and their per-hour derivatives) follow --
//  (2) x
//  (3) y
//  (4) d
//  (5) sin d
//  (6) cos d
//  (7) mu
//  (8) l1
//  (9) l2
// (10) dx
// (11) dy
// (12) dd
// (13) dmu
// (14) dl1
// (15) dl2
// -- time and location dependent circumstances follow --
// (16) h
// (17) sin h
// (18) cos h
// (19) xi
// (20) eta
// (21) zeta
// (22) dxi
// (23) deta
// (24) u
// (25) v
// (26) a
// (27) b
// (28) l1'
// (29) l2'
// (30) n^2
// -- observational circumstances follow --
// (31) p
// (32) alt
// (33) q
// (34) v
// (35) azi
// (36) m (mid eclipse only) or limb correction applied (where available!)
// (37) magnitude (mid eclipse only)
// (38) moon/sun (mid eclipse only)
// (39) calculated local event type for a transparent earth (mid eclipse only)
//      (0 = none, 1 = partial, 2 = annular, 3 = total)
// (40) event visibility
//      (0 = above horizon, 1 = below horizon, 2 = sunrise, 3 = sunset, 4 = below horizon, disregard)
//

var month = new Array("Jan","Feb","Mar","Apr","May","Jun","Jul",
                      "Aug","Sep","Oct","Nov","Dec");

var c1 = new Array();
var c2 = new Array();
var mid = new Array();
var c3 = new Array();
var c4 = new Array();


var currenttimeperiod = "";
var loadedtimeperiods = new Array();

//
// Populate the circumstances array with the time-only dependent circumstances (x, y, d, m, ...)
function timedependent(elements, circumstances) {
  var type, index, t, ans;

  t = circumstances[1]
  index = obsvconst[6]
  // Calculate x
  ans = elements[9+index] * t + elements[8+index]
  ans = ans * t + elements[7+index]
  ans = ans * t + elements[6+index]
  circumstances[2] = ans
  // Calculate dx
  ans = 3.0 * elements[9+index] * t + 2.0 * elements[8+index]
  ans = ans * t + elements[7+index]
  circumstances[10] = ans
  // Calculate y
  ans = elements[13+index] * t + elements[12+index]
  ans = ans * t + elements[11+index]
  ans = ans * t + elements[10+index]
  circumstances[3] = ans
  // Calculate dy
  ans = 3.0 * elements[13+index] * t + 2.0 * elements[12+index]
  ans = ans * t + elements[11+index]
  circumstances[11] = ans
  // Calculate d
  ans = elements[16+index] * t + elements[15+index]
  ans = ans * t + elements[14+index]
  ans = ans * Math.PI / 180.0
  circumstances[4] = ans
  // sin d and cos d
  circumstances[5] = Math.sin(ans)
  circumstances[6] = Math.cos(ans)
  // Calculate dd
  ans = 2.0 * elements[16+index] * t + elements[15+index]
  ans = ans * Math.PI / 180.0
  circumstances[12] = ans
  // Calculate m
  ans = elements[19+index] * t + elements[18+index]
  ans = ans * t + elements[17+index]
  if (ans >= 360.0) {
    ans = ans - 360.0
  }
  ans = ans * Math.PI / 180.0
  circumstances[7] = ans
  // Calculate dm
  ans = 2.0 * elements[19+index] * t + elements[18+index]
  ans = ans * Math.PI / 180.0
  circumstances[13] = ans
  // Calculate l1 and dl1
  type = circumstances[0]
  if ((type == -2) || (type == 0) || (type == 2)) {
    ans = elements[22+index] * t + elements[21+index]
    ans = ans * t + elements[20+index]
    circumstances[8] = ans
    circumstances[14] = 2.0 * elements[22+index] * t + elements[21+index]
  }
  // Calculate l2 and dl2
  if ((type == -1) || (type == 0) || (type == 1)) {
    ans = elements[25+index] * t + elements[24+index]
    ans = ans * t + elements[23+index]
    circumstances[9] = ans
    circumstances[15] = 2.0 * elements[25+index] * t + elements[24+index]
  }
  return circumstances
}

//
// Populate the circumstances array with the time and location dependent circumstances
function timelocdependent(elements,circumstances) {
  var ans, index, type

  timedependent(elements,circumstances)
  index = obsvconst[6]
  // Calculate h, sin h, cos h
  circumstances[16] = circumstances[7] - obsvconst[1] - (elements[index+5] / 13713.44)
  circumstances[17] = Math.sin(circumstances[16])
  circumstances[18] = Math.cos(circumstances[16])
  // Calculate xi
  circumstances[19] = obsvconst[5] * circumstances[17]
  // Calculate eta
  circumstances[20] = obsvconst[4] * circumstances[6] - obsvconst[5] * circumstances[18] * circumstances[5]
  // Calculate zeta
  circumstances[21] = obsvconst[4] * circumstances[5] + obsvconst[5] * circumstances[18] * circumstances[6]
  // Calculate dxi
  circumstances[22] = circumstances[13] * obsvconst[5] * circumstances[18]
  // Calculate deta
  circumstances[23] = circumstances[13] * circumstances[19] * circumstances[5] - circumstances[21] * circumstances[12]
  // Calculate u
  circumstances[24] = circumstances[2] - circumstances[19]
  // Calculate v
  circumstances[25] = circumstances[3] - circumstances[20]
  // Calculate a
  circumstances[26] = circumstances[10] - circumstances[22]
  // Calculate b
  circumstances[27] = circumstances[11] - circumstances[23]
  // Calculate l1'
  type = circumstances[0]
  if ((type == -2) || (type == 0) || (type == 2)) {
    circumstances[28] = circumstances[8] - circumstances[21] * elements[26+index]
  }
  // Calculate l2'
  if ((type == -1) || (type == 0) || (type == 1)) {
    circumstances[29] = circumstances[9] - circumstances[21] * elements[27+index]
  }
  // Calculate n^2
  circumstances[30] = circumstances[26] * circumstances[26] + circumstances[27] * circumstances[27]
  return circumstances
}

//
// Iterate on C1 or C4
function c1c4iterate(elements,circumstances) {
  var sign, iter, tmp, n

  timelocdependent(elements,circumstances)
  if (circumstances[0] < 0) {
    sign=-1.0
  } else {
    sign=1.0
  }
  tmp=1.0
  iter=0
  while (((tmp > 0.000001) || (tmp < -0.000001)) && (iter < 50)) {
    n = Math.sqrt(circumstances[30])
    tmp = circumstances[26] * circumstances[25] - circumstances[24] * circumstances[27]
    tmp = tmp / n / circumstances[28]
    tmp = sign * Math.sqrt(1.0 - tmp * tmp) * circumstances[28] / n
    tmp = (circumstances[24] * circumstances[26] + circumstances[25] * circumstances[27]) / circumstances[30] - tmp
    circumstances[1] = circumstances[1] - tmp
    timelocdependent(elements,circumstances)
    iter++
  }
  return circumstances
}

//
// Get C1 and C4 data
//   Entry conditions -
//   1. The mid array must be populated
//   2. The magnitude at mid eclipse must be > 0.0
function getc1c4(elements) {
  var tmp, n

  n = Math.sqrt(mid[30])
  tmp = mid[26] * mid[25] - mid[24] * mid[27]
  tmp = tmp / n / mid[28]
  tmp = Math.sqrt(1.0 - tmp * tmp) * mid[28] / n
  c1[0] = -2
  c4[0] = 2
  c1[1] = mid[1] - tmp
  c4[1] = mid[1] + tmp
  c1c4iterate(elements,c1)
  c1c4iterate(elements,c4)
}

//
// Iterate on C2 or C3
function c2c3iterate(elements,circumstances) {
  var sign, iter, tmp, n

  timelocdependent(elements,circumstances)
  if (circumstances[0] < 0) {
    sign=-1.0
  } else {
    sign=1.0
  }
  if (mid[29] < 0.0) {
    sign = -sign
  }
  tmp=1.0
  iter=0
  while (((tmp > 0.000001) || (tmp < -0.000001)) && (iter < 50)) {
    n = Math.sqrt(circumstances[30])
    tmp = circumstances[26] * circumstances[25] - circumstances[24] * circumstances[27]
    tmp = tmp / n / circumstances[29]
    tmp = sign * Math.sqrt(1.0 - tmp * tmp) * circumstances[29] / n
    tmp = (circumstances[24] * circumstances[26] + circumstances[25] * circumstances[27]) / circumstances[30] - tmp
    circumstances[1] = circumstances[1] - tmp
    timelocdependent(elements,circumstances)
    iter++
  }
  return circumstances
}

//
// Get C2 and C3 data
//   Entry conditions -
//   1. The mid array must be populated
//   2. There must be either a total or annular eclipse at the location!
function getc2c3(elements) {
  var tmp, n

  n = Math.sqrt(mid[30])
  tmp = mid[26] * mid[25] - mid[24] * mid[27]
  tmp = tmp / n / mid[29]
  tmp = Math.sqrt(1.0 - tmp * tmp) * mid[29] / n
  c2[0] = -1
  c3[0] = 1
  if (mid[29] < 0.0) {
    c2[1] = mid[1] + tmp
    c3[1] = mid[1] - tmp
  } else {
    c2[1] = mid[1] - tmp
    c3[1] = mid[1] + tmp
  }
  c2c3iterate(elements,c2)
  c2c3iterate(elements,c3)
}

//
// Get the observational circumstances
function observational(circumstances) {
  var contacttype, coslat, sinlat

  // We are looking at an "external" contact UNLESS this is a total eclipse AND we are looking at
  // c2 or c3, in which case it is an INTERNAL contact! Note that if we are looking at mid eclipse,
  // then we may not have determined the type of eclipse (mid[39]) just yet!
  if (circumstances[0] == 0) {
    contacttype = 1.0
  } else {
    if ((mid[39] == 3) && ((circumstances[0] == -1) || (circumstances[0] == 1))) {
      contacttype = -1.0
    } else {
      contacttype = 1.0
    }
  }
  // Calculate p
  circumstances[31] = Math.atan2(contacttype*circumstances[24], contacttype*circumstances[25])
  // Calculate alt
  sinlat = Math.sin(obsvconst[0])
  coslat = Math.cos(obsvconst[0])
  circumstances[32] = Math.asin(circumstances[5] * sinlat + circumstances[6] * coslat * circumstances[18])
  // Calculate q
  circumstances[33] = Math.asin(coslat * circumstances[17] / Math.cos(circumstances[32]))
  if (circumstances[20] < 0.0) {
    circumstances[33] = Math.PI - circumstances[33]
  }
  // Calculate v
  circumstances[34] = circumstances[31] - circumstances[33]
  // Calculate azi
  circumstances[35] = Math.atan2(-1.0*circumstances[17]*circumstances[6], circumstances[5]*coslat - circumstances[18]*sinlat*circumstances[6])
  // Calculate visibility
  if (circumstances[32] > -0.00524) {
    circumstances[40] = 0
  } else {
    circumstances[40] = 1
  }
}

//
// Get the observational circumstances for mid eclipse
function midobservational() {
  observational(mid)
  // Calculate m, magnitude and moon/sun
  mid[36] = Math.sqrt(mid[24]*mid[24] + mid[25]*mid[25])
  mid[37] = (mid[28] - mid[36]) / (mid[28] + mid[29])
  mid[38] = (mid[28] - mid[29]) / (mid[28] + mid[29])
}

//
// Calculate mid eclipse
function getmid(elements) {
  var iter, tmp

  mid[0] = 0
  mid[1] = 0.0
  iter = 0
  tmp = 1.0
  timelocdependent(elements,mid)
  while (((tmp > 0.000001) || (tmp < -0.000001)) && (iter < 50)) {
    tmp = (mid[24] * mid[26] + mid[25] * mid[27]) / mid[30]
    mid[1] = mid[1] - tmp
    iter++
    timelocdependent(elements,mid)
  }
}

//
// Calculate the time of sunrise or sunset
function getsunriset(elements,circumstances,riset) {
  var h0, diff, iter

  diff = 1.0
  iter = 0
  while ((diff > 0.00001) || (diff < -0.00001)) {
    iter++
    if (iter == 4) return
    h0 = Math.acos((Math.sin(-0.00524) - Math.sin(obsvconst[0]) * circumstances[5])/Math.cos(obsvconst[0])/circumstances[6])
    diff = (riset * h0 - circumstances[16])/circumstances[13];
    while (diff >= 12.0) diff -= 24.0;
    while (diff <= -12.0) diff += 24.0;
    circumstances[1] += diff
    timelocdependent(elements,circumstances)
  }
}

//
// Calculate the time of sunrise
function getsunrise(elements,circumstances) {
  getsunriset(elements,circumstances,-1.0)
}

//
// Calculate the time of sunset
function getsunset(elements,circumstances) {
  getsunriset(elements,circumstances,1.0)
}

//
// Copy a set of circumstances
function copycircumstances(circumstancesfrom, circumstancesto) {
  var i;

  for (i = 1 ; i < 41 ; i++) {
    circumstancesto[i] = circumstancesfrom[i];
  }
}

//
// Populate the c1, c2, mid, c3 and c4 arrays
function getall(elements) {
  var pattern

  getmid(elements)
  midobservational()
  if (mid[37] > 0.0) {
    getc1c4(elements)
    if ((mid[36] < mid[29]) || (mid[36] < -mid[29])) {
      getc2c3(elements)
      if (mid[29] < 0.0) {
        mid[39] = 3 // Total eclipse
      } else {
        mid[39] = 2 // Annular eclipse
      }
      observational(c1)
      observational(c2)
      observational(c3)
      observational(c4)
      c2[36] = 999.9
      c3[36] = 999.9
      // Calculate how much of the eclipse is above the horizon
      pattern = 0
      if (c1[40] == 0) { pattern += 10000 }
      if (c2[40] == 0) { pattern += 1000 }
      if (mid[40] == 0) { pattern += 100 }
      if (c3[40] == 0) { pattern += 10 }
      if (c4[40] == 0) { pattern += 1 }
      // Now, time to make sure that all my observational[39] and observational[40] are OK
      if (pattern == 11110) {
        getsunset(elements,c4)
        observational(c4)
        c4[40] = 3
      } else if (pattern == 11100) {
        getsunset(elements,c3)
        observational(c3)
        c3[40] = 3
        copycircumstances(c3, c4);
      } else if (pattern == 11000) {
        c3[40] = 4
        getsunset(elements,mid)
        midobservational()
        mid[40] = 3
        copycircumstances(mid, c4)
      } else if (pattern == 10000) {
        mid[39] = 1
        getsunset(elements,mid)
        midobservational()
        mid[40] = 3
        copycircumstances(mid, c4)
      } else if (pattern == 1111) {
        getsunrise(elements,c1)
        observational(c1)
        c1[40] = 2
      } else if (pattern == 111) {
        getsunrise(elements,c2)
        observational(c2)
        c2[40] = 2
        copycircumstances(c2, c1)
      } else if (pattern == 11) {
        c2[40] = 4
        getsunrise(elements,mid)
        midobservational()
        mid[40] = 2
        copycircumstances(mid, c1)
      } else if (pattern == 1) {
        mid[39] = 1
        getsunrise(elements,mid)
        midobservational()
        mid[40] = 2
        copycircumstances(mid, c1)
      } else if (pattern == 0) {
        mid[39] = 0
      }
      // There are other patterns, but those are the only ones we're covering!
   } else {
      mid[39] = 1 // Partial eclipse
      pattern = 0
      observational(c1)
      observational(c4)
      if (c1[40] == 0) { pattern += 100 }
      if (mid[40] == 0) { pattern += 10 }
      if (c4[40] == 0) { pattern += 1 }
      if (pattern == 110) {
        getsunset(elements,c4)
        observational(c4)
        c4[40] = 3
      } else if (pattern == 100) {
        getsunset(elements,mid)
        midobservational()
        mid[40] = 3
        copycircumstances(mid, c4)
      } else if (pattern == 11) {
        getsunrise(elements,c1)
        observational(c1)
        c1[40] = 2
      } else if (pattern == 1) {
        getsunrise(elements,mid)
        midobservational()
        mid[40] = 2
        copycircumstances(mid, c1)
      } else if (pattern == 0) {
        mid[39]=0
      }
      // There are other patterns, but those are the only ones we're covering!
    }
  } else {
    mid[39] = 0 // No eclipse
  }
  // Magnitude for total and annular eclipse is moon/sun ratio
  if ((mid[39] == 2) || (mid[39] == 3)) {
     mid[37] = mid[38]
  }
}

//
// Read the data that's in the form, and populate the obsvconst array
function readform() {
  var tmp

  // Make sure that we have something to parse from the form
  if (document.eclipseform.latd.value == "") document.eclipseform.latd.value="0"
  if (document.eclipseform.latm.value == "") document.eclipseform.latm.value="0"
  if (document.eclipseform.lats.value == "") document.eclipseform.lats.value="0"
  if (document.eclipseform.lond.value == "") document.eclipseform.lond.value="0"
  if (document.eclipseform.lonm.value == "") document.eclipseform.lonm.value="0"
  if (document.eclipseform.lons.value == "") document.eclipseform.lons.value="0"
  if (document.eclipseform.alt.value == "") document.eclipseform.alt.value="0"

  // Write back to the form what we are parsing
  document.eclipseform.latd.value=Math.abs(parseFloat(document.eclipseform.latd.value))
  document.eclipseform.latm.value=Math.abs(parseFloat(document.eclipseform.latm.value))
  document.eclipseform.lats.value=Math.abs(parseFloat(document.eclipseform.lats.value))
  document.eclipseform.lond.value=Math.abs(parseFloat(document.eclipseform.lond.value))
  document.eclipseform.lonm.value=Math.abs(parseFloat(document.eclipseform.lonm.value))
  document.eclipseform.lons.value=Math.abs(parseFloat(document.eclipseform.lons.value))
  document.eclipseform.alt.value=Math.abs(parseFloat(document.eclipseform.alt.value))

  // Get the latitude
  obsvconst[0]=parseFloat(document.eclipseform.latd.value)+parseFloat(document.eclipseform.latm.value)/60.0+parseFloat(document.eclipseform.lats.value)/3600.0
  obsvconst[0]=obsvconst[0]*parseFloat(document.eclipseform.latx.options[document.eclipseform.latx.selectedIndex].value)
  obsvconst[0]=obsvconst[0]*Math.PI/180.0

  // Get the longitude
  obsvconst[1]=parseFloat(document.eclipseform.lond.value)+parseFloat(document.eclipseform.lonm.value)/60.0+parseFloat(document.eclipseform.lons.value)/3600.0
  obsvconst[1]=obsvconst[1]*parseFloat(document.eclipseform.lonx.options[document.eclipseform.lonx.selectedIndex].value)
  obsvconst[1]=obsvconst[1]*Math.PI/180.0

  // Get the altitude
  obsvconst[2]=parseFloat(document.eclipseform.alt.value)

  // Get the time zone
  obsvconst[3]=parseFloat(document.eclipseform.tzm.options[document.eclipseform.tzm.selectedIndex].value)
  obsvconst[3]=parseFloat(document.eclipseform.tzh.options[document.eclipseform.tzh.selectedIndex].value) + obsvconst[3]/60.0
  obsvconst[3]=parseFloat(document.eclipseform.tzx.options[document.eclipseform.tzx.selectedIndex].value) * obsvconst[3]

  // Get the observer's geocentric position
  tmp=Math.atan(0.99664719*Math.tan(obsvconst[0]))
  obsvconst[4]=0.99664719*Math.sin(tmp)+(obsvconst[2]/6378140.0)*Math.sin(obsvconst[0])
  obsvconst[5]=Math.cos(tmp)+(obsvconst[2]/6378140.0*Math.cos(obsvconst[0]))

  // The index of the selected eclipse...
  //obsvconst[6] = 28 * (parseInt(document.eclipseform.index.options[document.eclipseform.index.selectedIndex].value) + 65)

}

//
// Get the local date of an event
function getdate(elements,circumstances) {
  var t, ans, jd, a, b, c, d, e, index

  index = obsvconst[6]
  // Calculate the JD for noon (TDT) the day before the day that contains T0
  jd = Math.floor(elements[index] - (elements[1+index]/24.0))
  // Calculate the local time (ie the offset in hours since midnight TDT on the day containing T0).
  t = circumstances[1] + elements[1+index] - obsvconst[3] - (elements[4+index] - 0.5) / 3600.0
  if (t < 0.0) {
    jd--;
  }
  if (t >= 24.0) {
    jd++;
  }
  if (jd >= 2299160.0) {
    a = Math.floor((jd - 1867216.25) / 36524.25)
    a = jd + 1 + a - Math.floor(a/4);
  } else {
    a = jd;
  }
  b = a + 1525.0
  c = Math.floor((b-122.1)/365.25)
  d = Math.floor(365.25*c)
  e = Math.floor((b - d) / 30.6001)
  d = b - d - Math.floor(30.6001*e)
  if (e < 13.5) {
    e = e - 1
  } else {
    e = e - 13
  }
  if (e > 2.5) {
    ans = c - 4716 + "-"
  } else {
    ans = c - 4715 + "-"
  }
  ans += month[e-1] + "-"
  if (d < 10) {
    ans = ans + "0"
  }
  ans = ans + d
  return ans
}

//
// Get the local time of an event
function gettime(elements,circumstances) {
  var t, ans, index

  ans = ""
  index = obsvconst[6]
  t = circumstances[1] + elements[1+index] - obsvconst[3] - (elements[4+index] - 0.5) / 3600.0
  if (t < 0.0) {
    t = t + 24.0
  }
  if (t >= 24.0) {
    t = t - 24.0
  }
  if (t < 10.0) {
    ans = ans + "0"
  }
  ans = ans + Math.floor(t) + ":"
  t = (t * 60.0) - 60.0 * Math.floor(t)
  if (t < 10.0) {
    ans = ans + "0"
  }
  ans = ans + Math.floor(t)
  if (circumstances[40] <= 1) { // not sunrise or sunset
    ans = ans + ":"
    t = (t * 60.0) - 60.0 * Math.floor(t)
    if (t < 10.0) {
      ans = ans + "0"
    }
    ans = ans + Math.floor(t)
  }
  if (circumstances[40] == 1) {
    html = document.createElement("font");
    html.setAttribute("color","#808080");
    ital = document.createElement("i");
    ital.appendChild(document.createTextNode(ans));
    html.appendChild(ital);
    return html;
  } else if (circumstances[40] == 2) {
    return document.createTextNode(ans+"(r)");
  } else if (circumstances[40] == 3) {
    return document.createTextNode(ans+"(s)");
  } else {
    return document.createTextNode(ans);
  }
}

//
// Get the altitude
function getalt(circumstances) {
  var t, ans

  if (circumstances[40] == 2) {
    return document.createTextNode("0(r)");
  }
  if (circumstances[40] == 3) {
    return document.createTextNode("0(s)");
  }
  if ((circumstances[32] < 0.0) && (circumstances[32] >= -0.00524)) {
    // Crude correction for refraction (and for consistency's sake)
    t = 0.0
  } else {
    t = circumstances[32] * 180.0 / Math.PI
  }
  if (t < 0.0) {
    ans = "-"
    t = -t
  } else {
    ans = ""
  }
  t = Math.floor(t+0.5)
  if (t < 10.0) {
    ans = ans + "0"
  }
  ans = ans + t
  if (circumstances[40] == 1) {
    html = document.createElement("font");
    html.setAttribute("color","#808080");
    ital = document.createElement("i");
    ital.appendChild(document.createTextNode(ans));
    html.appendChild(ital);
    return html;
  } else {
    return document.createTextNode(ans);
  }
}

//
// Get the azimuth
function getazi(circumstances) {
  var t, ans

  ans = ""
  t = circumstances[35] * 180.0 / Math.PI
  if (t < 0.0) {
    t = t + 360.0
  }
  if (t >= 360.0) {
    t = t - 360.0
  }
  t = Math.floor(t + 0.5)
  if (t < 100.0) {
    ans = ans + "0"
  }
  if (t < 10.0) {
    ans = ans + "0"
  }
  ans = ans + t
  if (circumstances[40] == 1) {
    html = document.createElement("font");
    html.setAttribute("color","#808080");
    ital = document.createElement("i");
    ital.appendChild(document.createTextNode(ans));
    html.appendChild(ital);
   return html;
  } else {
    return document.createTextNode(ans);
  }
}

//
// Get the duration in mm:ss.s format
//
// Adapted from code written by Stephen McCann - 27/04/2001
function getduration() {
  var tmp,ans;
  
  if (c3[40] == 4) {
    tmp = mid[1]-c2[1]
  } else if (c2[40] == 4) {
    tmp = c3[1]-mid[1]
  } else {
    tmp=c3[1]-c2[1];
  }
  if (tmp<0.0) {
    tmp=tmp+24.0
  } else if (tmp >= 24.0) {
    tmp=tmp-24.0
  }
  tmp=(tmp*60.0)-60.0*Math.floor(tmp)+0.05/60.0;
  ans=Math.floor(tmp)+"m"
  tmp=(tmp*60.0)-60.0*Math.floor(tmp)
  if (tmp < 10.0) {
    ans=ans+"0"
  }
  ans+=Math.floor(tmp)+"s"
  return ans
}

//
// Get the magnitude
function getmagnitude() {
  var a

  a = Math.floor(1000.0*mid[37]+0.5)/1000.0
  if (mid[40] == 1) {
    html = document.createElement("font");
    html.setAttribute("color","#808080");
    ital = document.createElement("i");
    ital.appendChild(document.createTextNode(a));
    html.appendChild(ital);
    return html;
  }
  if (mid[40] == 2) {
    a = a + "(r)"
  }
  if (mid[40] == 3) {
    a = a + "(s)"
  }
  return document.createTextNode(a);
}

//
// Get the coverage
function getcoverage() {
  var a, b, c

  if (mid[37] <= 0.0) {
    a = "0.0"
  } else if (mid[37] >= 1.0) {
    a = "1.000"
  } else {
    if (mid[39] == 2) {
      c = mid[38] * mid[38]
    } else {
      c = Math.acos((mid[28]*mid[28] + mid[29]*mid[29] - 2.0*mid[36]*mid[36]) / (mid[28]*mid[28] - mid[29]*mid[29]))
      b = Math.acos((mid[28]*mid[29] + mid[36]*mid[36])/mid[36]/(mid[28]+mid[29]))
      a = Math.PI - b - c
      c = ((mid[38]*mid[38]*a + b) - mid[38]*Math.sin(c))/Math.PI
    }
    a = Math.floor(1000.0*c+0.5)/1000.0
  }
  if (mid[40] == 1) {
    html = document.createElement("font");
    html.setAttribute("color","#808080");
    ital = document.createElement("i");
    ital.appendChild(document.createTextNode(a));
    html.appendChild(ital);
    return html;
  }
  if (mid[40] == 2) {
    a = a + "(r)"
  }
  if (mid[40] == 3) {
    a = a + "(s)"
  }
  return document.createTextNode(a);
}

function clearoldresults() {
  results = document.getElementById("el_results");
  resultsTable = document.getElementById("el_locationtable");
  if (resultsTable != null) results.removeChild(resultsTable);
  resultsTable = document.getElementById("el_resultstable");
  if (resultsTable != null) results.removeChild(resultsTable);
}

// CALCULATE!
function calculatefor(el) {
  readform()
  clearoldresults();
  results = document.getElementById("el_results");
  p = document.createElement("p");
  p.setAttribute("id","el_locationtable");
  b = document.createElement("h2");
  b.appendChild(document.createTextNode("Solar Eclipses visible from  "+document.eclipseform.loc_name.value));
  p.appendChild(b);
  resultsTable = document.createElement("table");
  resultsTable.setAttribute("border","0");
  tbody = document.createElement("tbody");
  row = document.createElement("tr");
  td = document.createElement("td");
  td.setAttribute("align","right");
  td.setAttribute("nowrap","");
  td.appendChild(document.createTextNode("Latitude: "));
  row.appendChild(td);
  td = document.createElement("td");
  td.setAttribute("nowrap","");
  text = document.eclipseform.latd.value;
  text += "\u00b0 ";
  if (document.eclipseform.latm.value < 10) text += "0";
  text += document.eclipseform.latm.value;
  text += "' ";
  if (document.eclipseform.lats.value < 10) text += "0";
  text += document.eclipseform.lats.value;
  text += '" ';
  text += (document.eclipseform.latx.options[document.eclipseform.latx.selectedIndex]).text;
  td.appendChild(document.createTextNode(text));
  row.appendChild(td);
  tbody.appendChild(row);
  row = document.createElement("tr");
  td = document.createElement("td");
  td.setAttribute("align","right");
  td.setAttribute("nowrap","");
  td.appendChild(document.createTextNode("Longitude: "));
  row.appendChild(td);
  td = document.createElement("td");
  td.setAttribute("nowrap","");
  text = document.eclipseform.lond.value;
  text += "\u00b0 ";
  if (document.eclipseform.lonm.value < 10) text += "0";
  text += document.eclipseform.lonm.value;
  text += "' ";
  if (document.eclipseform.lons.value < 10) text += "0";
  text += document.eclipseform.lons.value;
  text += '" ';
  text += (document.eclipseform.lonx.options[document.eclipseform.lonx.selectedIndex]).text;
  td.appendChild(document.createTextNode(text));
  row.appendChild(td);
  tbody.appendChild(row);
  row = document.createElement("tr");
  td = document.createElement("td");
  td.setAttribute("align","right");
  td.setAttribute("nowrap","");
  td.appendChild(document.createTextNode("Altitude: "));
  row.appendChild(td);
  td = document.createElement("td");
  td.setAttribute("nowrap","");
  text = document.eclipseform.alt.value;
  text += "m";
  td.appendChild(document.createTextNode(text));
  row.appendChild(td);
  tbody.appendChild(row);
  row = document.createElement("tr");
  td = document.createElement("td");
  td.setAttribute("align","right");
  td.setAttribute("nowrap","");
  td.appendChild(document.createTextNode("Time Zone: "));
  row.appendChild(td);
  td = document.createElement("td");
  td.setAttribute("nowrap","");
  text = (document.eclipseform.tzh.options[document.eclipseform.tzh.selectedIndex]).text;
  text += ":";
  text += (document.eclipseform.tzm.options[document.eclipseform.tzm.selectedIndex]).text;
  text += " ";
  text += (document.eclipseform.tzx.options[document.eclipseform.tzx.selectedIndex]).text;
  td.appendChild(document.createTextNode(text));
  row.appendChild(td);
  tbody.appendChild(row);
  resultsTable.appendChild(tbody);
  p.appendChild(resultsTable);
  results.appendChild(p);

  resultsTable = document.createElement("table");
  resultsTable.setAttribute("id","el_resultstable");
  resultsTable.setAttribute("width","150");
  resultsTable.setAttribute("border","2");
  tbody = document.createElement("tbody");
  row = document.createElement("tr");
  td = document.createElement("th");
  td.appendChild(document.createTextNode("Calendar Date"));
  row.appendChild(td);
  td = document.createElement("th");
  td.appendChild(document.createTextNode("Eclipse Type"));
  row.appendChild(td);
  td = document.createElement("th");
  td.appendChild(document.createTextNode("Partial Eclipse Begins"));
  row.appendChild(td);
  td = document.createElement("th");
  td.appendChild(document.createTextNode("Sun Alt"));
  row.appendChild(td);
  td = document.createElement("th");
  td.appendChild(document.createTextNode("A or T Eclipse Begins"));
  row.appendChild(td);
  td = document.createElement("th");
  td.appendChild(document.createTextNode("Maximum Eclipse"));
  row.appendChild(td);
  td = document.createElement("th");
  td.appendChild(document.createTextNode("Sun Alt"));
  row.appendChild(td);
  td = document.createElement("th");
  td.appendChild(document.createTextNode("Sun Azi"));
  row.appendChild(td);
  td = document.createElement("th");
  td.appendChild(document.createTextNode("A or T Eclipse Ends"));
  row.appendChild(td);
  td = document.createElement("th");
  td.appendChild(document.createTextNode("Partial Eclipse Ends"));
  row.appendChild(td);
  td = document.createElement("th");
  td.appendChild(document.createTextNode("Sun Alt"));
  row.appendChild(td);
  td = document.createElement("th");
  td.appendChild(document.createTextNode("Eclipse Mag."));
  row.appendChild(td);
  td = document.createElement("th");
  td.appendChild(document.createTextNode("Eclipse Obs."));
  row.appendChild(td);
  td = document.createElement("th");
  td.appendChild(document.createTextNode("A or T Eclipse Duration"));
  row.appendChild(td);
  tbody.appendChild(row);
  for (i = 0 ; i < el.length ; i+=28) {
    obsvconst[6]=i;
    getall(el)
    // Is there an event...
    if (mid[39] > 0) {
      row = document.createElement("tr");
      td = document.createElement("td");
      td.setAttribute("nowrap","")
      val = document.createTextNode(getdate(el,mid));
      td.appendChild(val);
      row.appendChild(td);
      td = document.createElement("td");
      td.setAttribute("align","center");
      if (mid[39] == 1) {
	   val = document.createTextNode("P");
      } else if (mid[39] == 2) {
        val = document.createTextNode("A");
      } else {
        val = document.createTextNode("T");
      }
	td.appendChild(val);
	row.appendChild(td);
      // Partial eclipse start
      if (c1[40] == 4) {
        td = document.createElement("td")
        td.setAttribute("align","center")
        td.appendChild(document.createTextNode("-"))
        row.appendChild(td)
        td = document.createElement("td")
        td.appendChild(document.createTextNode("\u00a0"))
        row.appendChild(td)
      } else {
	  // Partial eclipse start time
	  td = document.createElement("td");
        td.setAttribute("nowrap","")
        td.appendChild(gettime(el,c1));
	  row.appendChild(td);
	  // Partial eclipse alt
	  td = document.createElement("td");
	  td.setAttribute("align","right");
	  td.appendChild(getalt(c1));
	  row.appendChild(td);
      }
	// Central eclipse time
	td = document.createElement("td");
	if ((mid[39] > 1) && (c2[40] != 4)) {
        td.setAttribute("nowrap","")
        td.appendChild(gettime(el,c2));
	} else {
	  td.setAttribute("align","center");
	  td.appendChild(document.createTextNode("-"));
	}
	row.appendChild(td);
	// Maximum eclipse time
	td = document.createElement("td");
      td.setAttribute("nowrap","")
	td.appendChild(gettime(el,mid));
	row.appendChild(td);
	// Maximum eclipse alt
	td = document.createElement("td");
	td.setAttribute("align","right");
	td.appendChild(getalt(mid));
	row.appendChild(td);
	// Maximum eclipse azi
	td = document.createElement("td");
	td.setAttribute("align","right");
	td.appendChild(getazi(mid));
	row.appendChild(td);
	// Central eclipse ends
	td = document.createElement("td");
	if ((mid[39] > 1) && (c3[40] != 4)) {
        td.setAttribute("nowrap","")
	  td.appendChild(gettime(el,c3));
	} else {
	  td.setAttribute("align","center");
	  td.appendChild(document.createTextNode("-"));
	}
	row.appendChild(td);
      // Partial eclipse ends
      if (c4[40] == 4) {
        td = document.createElement("td")
        td.setAttribute("align","center")
        td.appendChild(document.createTextNode("-"))
        row.appendChild(td)
        td = document.createElement("td")
        td.appendChild(document.createTextNode("\u00a0"))
        row.appendChild(td)
      } else {
	  // Partial eclipse ends
	  td = document.createElement("td");
        td.setAttribute("nowrap","")
        td.appendChild(gettime(el,c4));
	  row.appendChild(td);
	  // ... sun alt
	  td = document.createElement("td");
	  td.setAttribute("align","right");
	  td.appendChild(getalt(c4));
	  row.appendChild(td);
      }
	// Eclipse magnitude
	td = document.createElement("td");
	td.appendChild(getmagnitude());
	row.appendChild(td);
	// Coverage
	td = document.createElement("td");
	td.appendChild(getcoverage());
	row.appendChild(td);
	// Central duration
	td = document.createElement("td");
	if (mid[39] > 1) {
	  td.setAttribute("align","right");
        td.setAttribute("nowrap","")
	  val = document.createTextNode(getduration());
	} else {
	  td.setAttribute("align","center");
	  val = document.createTextNode("-");
	}
	td.appendChild(val);
	row.appendChild(td);
	tbody.appendChild(row);
    }
  }
  resultsTable.appendChild(tbody);
  results.appendChild(resultsTable);
}

function init() {
  opt = document.getElementById("el_cities");
  for (i = 0 ; i < cities.length ; i+=9) {
    name = String(cities[i]);
    if (name.indexOf("--",0) == 0) {
      group = document.createElement("optgroup");
      group.setAttribute("label",name.substring(2));
      opt.appendChild(group);
      i++;
    }
    city = document.createElement("option");
    city.setAttribute("value",i);
    cityName = document.createTextNode(cities[i]);
    city.appendChild(cityName);
    opt.appendChild(city);
  }
}

function citychange() {
  clearoldresults();
  index = Number(document.eclipseform.cityndx.value);
  if (index <= 0) return;
  hemisphere=0;
  document.eclipseform.loc_name.value = cities[index++];
  val = cities[index++];
  if (val < 0) { val=-val; hemisphere=1; }
  document.eclipseform.latd.value = val;
  val = cities[index++];
  if (val < 0) { val=-val; hemisphere=1; }
  document.eclipseform.latm.value = val;
  val = cities[index++];
  if (val < 0) { val=-val; hemisphere=1; }
  document.eclipseform.lats.value = val;
  document.eclipseform.latx.selectedIndex = hemisphere;
  hemisphere=0;
  val = cities[index++];
  if (val < 0) { val=-val; hemisphere=1; }
  document.eclipseform.lond.value = val;
  val = cities[index++];
  if (val < 0) { val=-val; hemisphere=1; }
  document.eclipseform.lonm.value = val;
  val = cities[index++];
  if (val < 0) { val=-val; hemisphere=1; }
  document.eclipseform.lons.value = val;
  document.eclipseform.lonx.selectedIndex = hemisphere;
  document.eclipseform.alt.value=cities[index++];
  val = cities[index];
  if (val < 0) {
    document.eclipseform.tzx.selectedIndex=1;
    val = -val;
  } else {
    document.eclipseform.tzx.selectedIndex=0;
  }
  document.eclipseform.tzh.selectedIndex = Math.floor(val);
  document.eclipseform.tzm.selectedIndex = Math.floor(4*(val-document.eclipseform.tzh.selectedIndex)+0.5);
}

function newloc() {
  document.eclipseform.cityndx.selectedIndex=0;
  clearoldresults();
}

function settimeperiod(timeperiod) {
  for (i = 0 ; i < loadedtimeperiods.length ; i++) {
    if (loadedtimeperiods[i] == timeperiod) {
      if (eval("self."+timeperiod)) {
        currenttimeperiod = timeperiod;
        eval(timeperiod+"()");
      }
      return;
    }
  }
  currenttimeperiod = timeperiod;
  loadedtimeperiods.push(timeperiod);
  head = document.getElementsByTagName("head")[0];
  script = document.createElement("script");
  script.setAttribute("language","JavaScript");
  script.setAttribute("src",timeperiod+".js");
  script.type = "text/javascript";
  script.defer = false;
  head.appendChild(script);
}

function recalculate() {
  eval(currenttimeperiod+"()");
}