# geo functions
# -------------------------------------------------------------------------------------------------
#
#
# geo.Coord class
# -------------------------------------------------------------------------------------------------
#
# geo.Coord.new([<coord>])        ... class that holds and maintains geographical coordinates
#                                     can be initialized with another geo.Coord instance
#
# SETTER METHODS:
#
#     .set(<coord>)               ... sets coordinates from another geo.Coord instance
#
#     .set_lat(<num>)             ... functions for setting latitude/longitude/altitude
#     .set_lon(<num>)
#     .set_alt(<num>)             ..this is in meters
#     .set_latlon(<num>, <num> [, <num>])      (altitude (meters) is optional; default=0)
#
#     .set_x(<num>)               ... functions for setting cartesian x/y/z coordinates
#     .set_y(<num>)
#     .set_z(<num>)
#     .set_xyz(<num>, <num>, <num>)
#
#
# GETTER METHODS:
#
#     .lat()
#     .lon()                      ... functions for getting lat/lon/alt
#     .alt()                          ... returns altitude in m
#     .latlon()                       ... returns vector  [<lat>, <lon>, <alt>]
#
#     .x()                        ... functions for reading cartesian coords (in m)
#     .y()
#     .z()
#     .xyz()                          ... returns vector  [<x>, <y>, <z>]
#
#
# QUERY METHODS:
#
#     .is_defined()               ... returns whether the coords are defined
#     .dump()                     ... outputs coordinates
#     .course_to(<coord>)         ... returns course to another geo.Coord instance (degree)
#     .distance_to(<coord>)       ... returns distance in m along Earth curvature, ignoring altitudes
#                                     useful for map distance
#     .direct_distance_to(<coord>)      ...   distance in m direct, considers altitude,
#                                             but cuts through Earth surface
#     .greatcircle_distance_to(<coord>, <coord>)  ... returns distance to a great circle (in m along Earth curvature)
#                                                     defined by two points  
#     .horizon()                  ... returns distance to the horizon in m along Earth curvature, ignoring altitudes
#
#
# MANIPULATION METHODS:
#
#     .apply_course_distance(<course>, <distance>)       ... moves the coord distance in meters in course direction (true)
#
#
#
#
# -------------------------------------------------------------------------------------------------
#
# geo.aircraft_position()         ... returns current aircraft position as geo.Coord
# geo.viewer_position()           ... returns viewer position as geo.Coord
# geo.click_position()            ... returns last click coords as geo.Coord or nil before first click
#
# geo.tile_path(<lat>, <lon>)     ... returns tile path string (e.g. "w130n30/w123n37/942056.stg")
# geo.elevation(<lat>, <lon> [, <top:10000>])
#                                 ... returns elevation in meter for given lat/lon, or nil on error;
#                                     <top> is the altitude at which the intersection test starts
#
# geo.normdeg(<angle>)            ... returns angle normalized to    0 <= angle < 360
# geo.normdeg180(<angle>)         ... returns angle normalized to -180 < angle <= 360
#
# geo.put_model(<path>, <lat>, <lon> [, <elev:nil> [, <hdg:0> [, <pitch:0> [, <roll:0>]]]]);
#                                 ... put model <path> at location <lat>/<lon> with given elevation
#                                     (optional, default: surface). <hdg>/<pitch>/<roll> are optional
#                                     and default to zero.
# geo.put_model(<path>, <coord> [, <hdg:0> [, <pitch:0> [, <roll:0>]]]);
#                                 ... same as above, but lat/lon/elev are taken from a Coord object


var EPSILON = 1e-15;
var ERAD = 6378138.12;		# Earth radius (m)

# class that maintains one set of geographical coordinates
#
var Coord = {
	new: func(copy = nil) {
		var m = { parents: [Coord] };
		m._pdirty = 1;  # polar
		m._cdirty = 1;  # cartesian
		m._lat = nil;   # in radian
		m._lon = nil;   #
		m._alt = nil;   # ASL
		m._x = nil;     # in m
		m._y = nil;
		m._z = nil;
		if (copy != nil)
			m.set(copy);
		return m;
	},
	_cupdate: func {
		me._cdirty or return;
		var xyz = geodtocart(me._lat * R2D, me._lon * R2D, me._alt);
		me._x = xyz[0];
		me._y = xyz[1];
		me._z = xyz[2];
		me._cdirty = 0;
	},
	_pupdate: func {
		me._pdirty or return;
		var lla = carttogeod(me._x, me._y, me._z);
		me._lat = lla[0] * D2R;
		me._lon = lla[1] * D2R;
		me._alt = lla[2];
		me._pdirty = 0;
	},

	x: func { me._cupdate(); me._x },
	y: func { me._cupdate(); me._y },
	z: func { me._cupdate(); me._z },
	xyz: func { me._cupdate(); [me._x, me._y, me._z] },

	lat: func { me._pupdate(); me._lat * R2D },  # return in degree
	lon: func { me._pupdate(); me._lon * R2D },
	alt: func { me._pupdate(); me._alt },
	latlon: func { me._pupdate(); [me._lat * R2D, me._lon * R2D, me._alt] },

	set_x: func(x) { me._cupdate(); me._pdirty = 1; me._x = x; me },
	set_y: func(y) { me._cupdate(); me._pdirty = 1; me._y = y; me },
	set_z: func(z) { me._cupdate(); me._pdirty = 1; me._z = z; me },

	set_lat: func(lat) { me._pupdate(); me._cdirty = 1; me._lat = lat * D2R; me },
	set_lon: func(lon) { me._pupdate(); me._cdirty = 1; me._lon = lon * D2R; me },
	set_alt: func(alt) { me._pupdate(); me._cdirty = 1; me._alt = alt; me },

	set: func(c) {
		c._pupdate();
		me._lat = c._lat;
		me._lon = c._lon;
		me._alt = c._alt;
		me._cdirty = 1;
		me._pdirty = 0;
		me;
	},
	set_latlon: func(lat, lon, alt = 0) {
		me._lat = lat * D2R;
		me._lon = lon * D2R;
		me._alt = alt;
		me._cdirty = 1;
		me._pdirty = 0;
		me;
	},
	set_xyz: func(x, y, z) {
		me._x = x;
		me._y = y;
		me._z = z;
		me._pdirty = 1;
		me._cdirty = 0;
		me;
	},
	apply_course_distance: func(course, dist) {
		me._pupdate();
		course *= D2R;
		dist /= ERAD;

		if (dist < 0.0) {
		  dist = abs(dist);
		  course = course - math.pi;
		}

		me._lat = math.asin(math.sin(me._lat) * math.cos(dist)
				+ math.cos(me._lat) * math.sin(dist) * math.cos(course));

		if (math.cos(me._lat) > EPSILON)
			me._lon = math.pi - math.mod(math.pi - me._lon
					- math.asin(math.sin(course) * math.sin(dist)
					/ math.cos(me._lat)), 2 * math.pi);

		me._cdirty = 1;
		me;
	},
	course_to: func(dest) {
		me._pupdate();
		dest._pupdate();

		if (me._lat == dest._lat and me._lon == dest._lon)
			return 0;

		var dlon = dest._lon - me._lon;
		var ret = nil;
		call(func ret = math.mod(math.atan2(math.sin(dlon) * math.cos(dest._lat),
				math.cos(me._lat) * math.sin(dest._lat)
				- math.sin(me._lat) * math.cos(dest._lat)
				* math.cos(dlon)), 2 * math.pi) * R2D, nil, var err = []);
		if (size(err)) {
			debug.printerror(err);
			debug.dump(me._lat, me._lon, dlon, dest._lat, dest._lon, "--------------------------");
		}
		return ret;
	},
	# arc distance on an earth sphere; doesn't consider altitude
	distance_to: func(dest) {
		me._pupdate();
		dest._pupdate();

		if (me._lat == dest._lat and me._lon == dest._lon)
			return 0;

		var a = math.sin((me._lat - dest._lat) * 0.5);
		var o = math.sin((me._lon - dest._lon) * 0.5);
		return 2.0 * ERAD * math.asin(math.sqrt(a * a + math.cos(me._lat)
				* math.cos(dest._lat) * o * o));
	},
	direct_distance_to: func(dest) {
		me._cupdate();
		dest._cupdate();
		var dx = dest._x - me._x;
		var dy = dest._y - me._y;
		var dz = dest._z - me._z;
		return math.sqrt(dx * dx + dy * dy + dz * dz);
	},
	# arc distance on an earth sphere to the great circle passing by A and B; doesn't consider altitude
	greatcircle_distance_to: func(destA, destB) {
		me._pupdate();
		destA._pupdate();
		destB._pupdate();

		# AB is not a circle but a point
		if (destA._lat == destB._lat and destA._lon == destB._lon) {
		    return me.distance_to(destA);
		}

		var ca1 = math.cos(destA._lon);
		var cd1 = math.cos(destA._lat);   
		var sa1 = math.sin(destA._lon);
		var sd1 = math.sin(destA._lat);    

		var ca2 = math.cos(destB._lon);
		var cd2 = math.cos(destB._lat);    
		var sa2 = math.sin(destB._lon);
		var sd2 = math.sin(destB._lat);    

		var sa12 = math.sin(destA._lon - destB._lon);
		
    		var ca3 = math.cos(me._lon);
		var cd3 = math.cos(me._lat);    
		var sa3 = math.sin(me._lon);
		var sd3 = math.sin(me._lat);    

		# this is sin(greatcircle_dist) * sin(arcAB)
                var sDsAB = cd3 * sa3 * (ca2 * cd2 * sd1 - ca1 * cd1 * sd2 )
		    + ca3 * cd3 * ( cd1 * sa1 * sd2 - cd2 * sa2 * sd1 )
		    - cd1 * cd2 * sd3 * sa12;
		
		# direct calculation of sin(arcAB) to not call sin(arcsin(distance_to))    
		var a = math.sin((destA._lat - destB._lat) * 0.5);
		var o = math.sin((destA._lon - destB._lon) * 0.5);

		var hs12 = a * a + cd1 * cd2 * o * o;
		var hc12 = 1.0 - hs12;		


		# AB is undertermined; a great circle should be defined with non-colinear vectors
		if (hs12*hc12 == 0.0) {
		    die("Great circles are defined with non-colinear vectors");
		}

		
		return ERAD * math.abs( math.asin( 0.5 * sDsAB / math.sqrt( hs12 * hc12 ) ) );
	},
	# arc distance on an earth sphere to the horizon    
        horizon: func() {
	        me._pupdate();
		if (me._alt < 0.0) {
		    return 0.0;
		}
		else {
		    return ERAD*math.acos(ERAD/(ERAD+me._alt));
		}
	},		
	is_defined: func {
		return !(me._cdirty and me._pdirty);
	},
	dump: func {
		if (me._cdirty and me._pdirty)
			print("Coord.dump(): coordinates undefined");

		me._cupdate();
		me._pupdate();
		printf("x=%f  y=%f  z=%f    lat=%f  lon=%f  alt=%f",
				me.x(), me.y(), me.z(), me.lat(), me.lon(), me.alt());
	},
};


# normalize degree to 0 <= angle < 360
#
var normdeg = func(angle) {
	while (angle < 0)
		angle += 360;
	while (angle >= 360)
		angle -= 360;
	return angle;
}

# normalize degree to -180 < angle <= 180
#
var normdeg180 = func(angle) {
	while (angle <= -180)
		angle += 360;
	while (angle > 180)
		angle -= 360;
	return angle;
}

var tile_index = func(lat, lon) {
    return tileIndex(lat, lon);
}


var format = func(lat, lon) {
	sprintf("%s%03d%s%02d", lon < 0 ? "w" : "e", abs(lon), lat < 0 ? "s" : "n", abs(lat));
}


var tile_path = func(lat, lon) {
	var p = tilePath(lat, lon) ~ "/" ~ tileIndex(lat, lon) ~ ".stg";
}


var put_model = func(path, c, arg...) {
	call(_put_model, [path] ~ (isa(c, Coord) ? c.latlon() : [c]) ~ arg);
}


var _put_model = func(path, lat, lon, elev_m = nil, hdg = 0, pitch = 0, roll = 0) {
	if (elev_m == nil)
		elev_m = elevation(lat, lon);
	if (elev_m == nil)
		die("geo.put_model(): cannot get elevation for " ~ lat ~ "/" ~ lon);
	fgcommand("add-model", var n = props.Node.new({ "path": path,
		"latitude-deg": lat, "longitude-deg": lon, "elevation-m": elev_m,
		"heading-deg": hdg, "pitch-deg": pitch, "roll-deg": roll,
	}));
	return props.globals.getNode(n.getNode("property").getValue());
}


var elevation = func(lat, lon, maxalt = 10000) {
	var d = geodinfo(lat, lon, maxalt);
	return d == nil ? nil : d[0];
}


var click_coord = Coord.new();

_setlistener("/sim/signals/click", func {
	var lat = getprop("/sim/input/click/latitude-deg");
	var lon = getprop("/sim/input/click/longitude-deg");
	var elev = getprop("/sim/input/click/elevation-m");
	click_coord.set_latlon(lat, lon, elev);
});

var click_position = func {
	return click_coord.is_defined() ? Coord.new(click_coord) : nil;
}


var aircraft_position = func {
	var lat = getprop("/position/latitude-deg");
	var lon = getprop("/position/longitude-deg");
	var alt = getprop("/position/altitude-ft") * FT2M;
	return Coord.new().set_latlon(lat, lon, alt);
}


var viewer_position = func {
	var x = getprop("/sim/current-view/viewer-x-m");
	var y = getprop("/sim/current-view/viewer-y-m");
	var z = getprop("/sim/current-view/viewer-z-m");
	return Coord.new().set_xyz(x, y, z);
}

# A object to handle differential positioned searches:
# searchCmd executes and returns the actual search,
# onAdded and onRemoved are callbacks,
# and obj is a "me" reference (defaults to "me" in the
# caller's namespace). If searchCmd returns nil, nothing
# happens, i.e. the diff is cancelled.
var PositionedSearch = {
	new: func(searchCmd, onAdded, onRemoved, obj=nil) {
		return {
			parents:[PositionedSearch],
			obj: obj == nil ? caller(1)[0]["me"] : obj,
			searchCmd: searchCmd,
			onAdded: onAdded,
			onRemoved: onRemoved,
			result: [],
		};
	},
	_equals: func(a,b) {
		return a == b; # positioned objects are created once
		#return (a == b or a.id == b.id);
	},
	condense: func(vec) {
		var ret = [];
		foreach (var e; vec)
			if (e != nil) append(ret, e);
		return ret;
	},
	diff: func(old, new) {
		if (new == nil)
			return [old, [], []];
		var removed = old~[]; #copyvec
		var added = new~[];
		# Mark common elements from removed and added:
		forindex (OUTER; var i; removed)
			forindex (var j; new)
				if (removed[i] != nil and added[j] != nil and me._equals(removed[i], added[j])) {
					removed[i] = added[j] = nil;
					continue OUTER;
				}
		# And remove those common elements, returning the result:
		return [new, me.condense(removed), me.condense(added)];
	},
	update: func(searchCmd=nil) {
		if (searchCmd == nil) searchCmd = me.searchCmd;
		if (me._equals == PositionedSearch._equals) {
			# Optimized search using C code
			var old = me.result~[]; #copyvec
			me.result = call(searchCmd, nil, me.obj);
			if (me.result == nil)
			{ me.result = old; return }
			if (typeof(me.result) != 'vector') die("geo.PositionedSearch(): A searchCmd must return a vector of elements or nil !!"); # TODO: Maybe make this a hash instead to wrap a vector, so that we can implement basic type-checking - e.g. doing isa(PositionedSearchResult, me.result) would be kinda neat and could help troubleshooting
			else
			positioned.diff( old,
			                 me.result,
			                 func call(me.onAdded, arg, me.obj),
			                 func call(me.onRemoved, arg, me.obj) );
		} else {
			(me.result, var removed, var added) = me.diff(me.result, call(searchCmd, nil, me.obj));
			foreach (var e; removed)
				call(me.onRemoved, [e], me.obj);
			foreach (var e; added)
				call(me.onAdded, [e], me.obj);
		}
	},
	# this is the worst case scenario: switching from 640 to 320 (or vice versa)
	test: func(from=640, to=320) {
	  var s= geo.PositionedSearch.new(
	    func positioned.findWithinRange(from, 'fix'),
	    func print('added:', arg[0].id),
	    func print('removed:', arg[0].id)
	  );
	  debug.benchmark('Toggle '~from~'nm/'~to~'nm', func {
	    s.update();
	    s.update( func positioned.findWithinRange(to, 'fix') );
	  }); # ~ takes
	}, # of test
};