/*
Description:
  arribasail.js - common Javascript for arribasail.com web apps

License:
  Copyright (C) 2016-2017 Alan Noble <anoble@gmail.com>

  arribasail.js 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 3 of the
  License, or (at your option) any later version.

  arribasail.js 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
  (http://www.gnu.org/licenses/).
*/

const EARTH_RADIUS = 6373000;

// handy Math functions
Math.radians = function(deg) { return deg * Math.PI / 180; };

Math.degrees = function(rad) { return rad * 180 / Math.PI; };

Math.square = function(num) { return num * num; };

// utility functions
function isNumber(value) {
  // return true if value is a number
  return !isNaN(value);
}

function isAngle(value, range) {
  // return true if value is an angle within the given range, e.g., [-90,+90]
  if (isNaN(value)) return false;
  var angle = parseFloat(value);
  return (angle >= range[0] && angle <= range[1]);
}

function item(arr, prop, value) {
  // return the array item for which the property has a given value
  for (var ii = 0; ii < arr.length; ii++) {
    if (arr[ii][prop] == value) {
      return arr[ii];
    }
  }
}

function getParam(name) {
  // returns part of a query string
  var regex = new RegExp("[\\?&]" + name + "=([^&#]*)");
  var match = regex.exec(window.location.href);
  if(match == null) {
    return '';
  } else {
    return decodeURIComponent(match[1].replace(/\+/g, " "));
  }
}

function getUrlPart(name) {
  // returns part of current location URL, given blah.com/foo/bar and "foo", returns "bar"
  var regex = new RegExp("/" + name + "/([^/]*)");
  var match = regex.exec(window.location.href);
  if(match == null) {
    return '';
  } else {
    return decodeURIComponent(match[1].replace(/\+/g, " "));
  }
}

function hasLabel(labels, label) {
  // returns true if comma-separated labels contains a given label
  var regex = new RegExp("(^|,)" + label + "($|,)");
  return regex.test(labels);
}

function quote(str) {
  // quote a string using single quotes
  return "'" + str.replace(/'/g,"\\'") + "'";
}

// DOM accessors/mutators
function getInput(name) {
  // get an input value
  return document.getElementById(name).value;
}

function setInput(name, value) {
  // set an input value
  if (value != null && value != '') {
    document.getElementById(name).value = value;
  }
}

function getChecked(name) {
  return document.getElementById(name).checked;
}

function setChecked(name, value) {
  if (value == 'true') {
    document.getElementById(name).checked = true;
  } else {
    document.getElementById(name).checked = false;
  }
}

function getSelected(name) {
  var menu= document.getElementById(name);
  return menu.options[menu.selectedIndex].value;
}

function setSelected(name, value) {
  var menu = document.getElementById(name);
  for (var ii = 0; ii < menu.options.length; ii++) {
    if (menu.options[ii].value === value) {
      menu.selectedIndex = ii;
      return;
    }
  }
}

// latlng functions
// a latlng object is simply { lat:lat_value, lng:lng_value }

function parseLatlng(latlng_str) {
  // returns a lat,lng object given a string representing a latlng in either decdeg or decmin format
  var lat = null;
  var lng = null;
  var regex_decdeg = /([-\.\d]+)[\s°]?\s*,\s*([-\.\d]+)[\s°]?/; // NB: comma is required for decimal degree format
  var match = regex_decdeg.exec(latlng_str);
  if (match) {
    lat = parseFloat(match[1]);
    lng = parseFloat(match[2]);
  } else {
    var regex_decmin = /([\d]+)[\s°]?([\d]*\.?[\d]*)?[’']?\s*([NS])\s*,?\s*([\d]+)[\s°]?([\d]*\.?[\d]*)?[’']?\s*([EW])/;
    match = regex_decmin.exec(latlng_str.toUpperCase());
    if (match) {
      var sign = (match[3] == 'S') ? -1 : 1;
      if (!match[2]) match[2] = '0';
      lat = sign * (parseInt(match[1]) + parseFloat(match[2])/60);
      sign = (match[6] == 'W') ? -1 : 1;
      if (!match[5]) match[5] = '0';
      lng = sign * (parseInt(match[4]) + parseFloat(match[5])/60);
    }
  }
  if (isAngle(lat, [-90, 90]) && isAngle(lng, [-180, 180])) {
    return { lat:lat, lng:lng };
  }
  return null;
}

function splitLatlng(latlng) {
  // split latlng object into 4 components: [abs(lat),lat_hemisphere,abs(lng),lng_hemisphere]
  var ll;
  if (typeof latlng.lat == 'function' && typeof latlng.lng == 'function') {
    ll = [latlng.lat(),'N',latlng.lng(),'E'];
  } else {
    ll = [latlng.lat,'N',latlng.lng,'E'];
  }
  if (ll[0] < 0) {
    ll[0] = Math.abs(ll[0]);
    ll[1] = 'S';
  }
  if (ll[2] < 0) {
    ll[2] = Math.abs(ll[2]);
    ll[3] = 'W';
  }
  return ll;
}

function formatLatlng(latlng, fmt, decimals) {
  // formats latlng object as decimal degrees (decdeg), decimal minutes (decmin) or minutes/seconds (minsec)
  // convert google.maps.LatLng if necessary
  if (typeof latlng.lat == 'function' && typeof latlng.lng == 'function') {
    latlng = { lat:latlng.lat(), lng:latlng.lng() }
  }
  if (fmt == 'decdeg') {
    if (typeof decimals === 'undefined') decimals = 6;
    var mm = Math.pow(10, decimals);
    var lat = Math.round(latlng.lat * mm)/mm;
    var lng = Math.round(latlng.lng * mm)/mm;
    return lat + ', ' + lng;
  } else if(fmt == 'decmin') {
    if (typeof decimals === 'undefined') decimals = 3;
    var mm = Math.pow(10, decimals);
    var ll = splitLatlng(latlng);
    var latmin = Math.round(60 * (ll[0] % 1) * mm)/mm;
    var lngmin = Math.round(60 * (ll[2] % 1) * mm)/mm;
    return ~~ll[0] + '°' + latmin + "'" + ll[1] + ' ' + ~~ll[2] + '°' + lngmin + "'" + ll[3];
  } else if(fmt == 'minsec') {
    var ll = splitLatlng(latlng);
    var latmin = 60 * (ll[0] % 1);
    var lngmin = 60 * (ll[2] % 1);
    var latsec = Math.round(60 * (latmin % 1));
    if (latsec == 60) {
      latsec = 0;
      latmin++;
    }
    var lngsec = Math.round(60 * (lngmin % 1));
    if (lngsec == 60) {
      lngsec = 0;
      lngmin++;
    }
    return ~~ll[0] + '°' + ~~latmin + "'"  + latsec + '"' + ll[1] + ' ' + ~~ll[2] + '°' + ~~lngmin + "'" + lngsec + '"' + ll[3];
  } else {
    return '';
  }
}

function latlngDistance(latlng1, latlng2) {
  // calculate great-circle distance between 2 latlngs in meters, using Haversine Formula
  // convert google.maps.LatLng if necessary
  if (typeof latlng1.lat == 'function' && typeof latlng1.lng == 'function') {
    latlng1 = { lat:latlng1.lat(), lng:latlng1.lng() }
  }
  if (typeof latlng2.lat == 'function' && typeof latlng2.lng == 'function') {
    latlng2 = { lat:latlng2.lat(), lng:latlng2.lng() }
  }
  var lat1 = Math.radians(latlng1.lat);
  var lng1 = Math.radians(latlng1.lng);
  var lat2 = Math.radians(latlng2.lat);
  var lng2 = Math.radians(latlng2.lng);

  var dlng = lng2 - lng1;
  var dlat = lat2 - lat1;
  var aa = Math.square(Math.sin(dlat/2)) + Math.cos(lat1) * Math.cos(lat2) * Math.square(Math.sin(dlng/2));
  cc = 2 * Math.atan2(Math.sqrt(aa), Math.sqrt(1 - aa));
  return EARTH_RADIUS * cc;
}

function latlngBearing(latlng1, latlng2) {
  // caculate bearing from latlng1 to latlng2
  if (typeof latlng1.lat == 'function' && typeof latlng1.lng == 'function') {
    latlng1 = { lat:latlng1.lat(), lng:latlng1.lng() }
  }
  if (typeof latlng2.lat == 'function' && typeof latlng2.lng == 'function') {
    latlng2 = { lat:latlng2.lat(), lng:latlng2.lng() }
  }
  var lat1 = Math.radians(latlng1.lat);
  var lat2 = Math.radians(latlng2.lat);
  var dlng = Math.radians(latlng2.lng - latlng1.lng);
  var bearing = Math.degrees(Math.atan2(Math.sin(dlng)*Math.cos(lat2), Math.cos(lat1)*Math.sin(lat2)-Math.sin(lat1)*Math.cos(lat2)*Math.cos(dlng)));
  return (bearing + 360) % 360
}

function latlngCrossTrackDistance(pos, orig, dest) {
  // calculate cross-track distance (cross-track error) for position on a track between orig and dest
  var dist = latlngDistance(orig, pos); // how far along the track we are
  var dangle = latlngBearing(orig, pos) - latlngBearing(orig, dest); // relative angle off center
  return Math.asin(Math.sin(dist/EARTH_RADIUS) * Math.sin(Math.radians(dangle))) * EARTH_RADIUS;
}

function groundResolution(lat, zoom) {
  // groundResolution is the distance in m on the ground per Google Maps pixel
  // # pixels for the width of the (square) world map in Web Mercator.
  // For zoom level 0, this  is 256 pixels.
  var pixels = Math.pow(2, 8 + zoom);
  // divide earth's circumference (at given latitude) by # pixels
  return Math.cos(lat * Math.PI / 180) * 2 * Math.PI * EARTH_RADIUS / pixels;
}