extends Node

var Downloader = preload("res://downloader.gd")

var datafile = "height/SLDEM2015_512_00N_30N_000_045_FLOAT.IMG"
var samplesPerLine = 23040
var lines = 15360
var offset = 1737.4#*1000
var scaleFact = 1
var resolution = 512

var latMin = 0
var latMax = 30
var lonMin = 0
var lonMax = 45

var cache = {}
var file: File

# Called when the node enters the scene tree for the first time.
func open():
	file = File.new()
	if not file.file_exists("user://"+datafile):
		var downloader = Downloader.new()
		add_child(downloader)
		downloader.load(datafile, "height")
		yield(downloader, "request_completed")
	file.open("user://"+datafile, File.READ)
	
func close():
	file.close()
	queue_free()
	
func cacheArea(latMinIN, latMaxIN, lonMinIN, lonMaxIN):
	if not _validate(latMinIN,lonMinIN) and not _validate(latMaxIN,lonMaxIN) :
		print("out of scope!")
		return
		
	var lat = latMinIN
	while lat <= latMaxIN:
		cache[lat]={}
		var line = lat*resolution*samplesPerLine*4
		# the origin of each .img file lies in it's upper left corner
		# so we need to read the files from the end on the northern hemisphere
		if lat >= 0:
			var origin = latMax*resolution*samplesPerLine*4
			file.seek((origin - line) + lonMinIN*resolution*4)
		else:
			file.seek(line + lonMinIN*resolution*4)
		var lon = lonMinIN
		while lon <= lonMaxIN:
			cache[lat][lon] = file.get_float()
			lon += 1.0/float(resolution)
		lat += 1.0/float(resolution)
	return
	
func read(lat,lon):
	if _validate(lat,lon):
		return cache[lat][lon]
	else:
		print("out of scope!")

func _validate(lat,lon):
	if lat <= latMax and lat >= latMin and lon <= lonMax and lon >= lonMin:
		return true
	return false

# Called every frame. 'delta' is the elapsed time since the previous frame.
#func _process(delta):
#	pass