collectgarbage()
local startStopSwitch
local startStopSwitchState=0
local windowValue1,windowValue2
local altitudeSensorID,altitudeSensorParam
local distanceSensorID,distanceSensorParam
local distanceUnit

local windowValues={"Duration","Sink Rate","Airspeed","Glide Ratio"}
local windowValueUnits={"[s]","[m/s]","[m/s]","[:1]"}
local sensorLabels,sensorIDs,sensorParams
local distanceUnits={"[m]","[km]"}

local duration,sinkRate,airspeed,glideRatio={},{},{},{}
local timeStart,altitudeStart,distanceStart

local function printRowWindow(y,windowValue)
	local value="-"
	if #duration>0 then
		if windowValue==4 then
			if glideRatio[1]>=0 then value=string.format("%.1f",glideRatio[1]) end
		elseif windowValue==3 then
			if airspeed[1]>=0 then value=string.format("%.1f",airspeed[1]) end
		elseif windowValue==2 then
			if sinkRate[1]>=0 then value=string.format("%.2f",sinkRate[1]) end
		else
			value=string.format("%d",duration[1])
		end
	end
	lcd.drawText(5,y+7,windowValues[windowValue],FONT_MINI)
	lcd.drawText(5,y+19,windowValueUnits[windowValue],FONT_MINI)
	lcd.drawText(145-lcd.getTextWidth(FONT_MAXI,value),y,value,FONT_MAXI)
end
local function printWindow()
	printRowWindow(-3,windowValue1)
	printRowWindow(30,windowValue2)
end
local function printCellTable(x,y,w,text,format)
	lcd.drawText(x+(w+1-lcd.getTextWidth(format,text))/2,y,text,format)
	--lcd.drawRectangle(x,y,w+1)
	return x+w
end
local function printRowTable(row,text,format)
	local x,y=-1,-1+row*18
	x=printCellTable(x,y,80,text[1],format)
	x=printCellTable(x,y,80,text[2],format)
	x=printCellTable(x,y,80,text[3],format)
	x=printCellTable(x,y,80,text[4],format)
	lcd.drawLine(0,y,320,y)
end
local function printTable()
	printRowTable(0,windowValues,FONT_BOLD)
	
	for i=1,#duration do
		local text={"-","-","-","-"}
		if duration[i]>=0 then text[1]=string.format("%d s",duration[i]) end
		if sinkRate[i]>=0 then text[2]=string.format("%.2f m/s",sinkRate[i]) end
		if airspeed[i]>=0 then text[3]=string.format("%.1f m/s",airspeed[i]) end
		if glideRatio[i]>=0 then text[4]=string.format("%.1f:1",glideRatio[i]) end
		printRowTable(i,text,FONT_NORMAL)
	end
end
local function initSensors()
	local telSensors=system.getSensors()
	sensorLabels={"..."}
	sensorIDs={nil}
	sensorParams={nil}
	
	for i,sensor in ipairs(telSensors) do
		table.insert(sensorIDs,sensor.ID)
		table.insert(sensorParams,sensor.param)
		if sensor.param==0 then
			table.insert(sensorLabels,sensor.label)
		else
			table.insert(sensorLabels,sensor.label.." ["..sensor.unit.."]")
		end
	end
end
local function createForm(formID)
	initSensors()
	
	form.addRow(2)
	form.addLabel({label="Start/Stop Switch"})
	form.addInputbox(startStopSwitch,false,function(input) startStopSwitch=input system.pSave("startStopSwitch",startStopSwitch) end)
	form.addRow(2)
	form.addLabel({label="Window Value 1",width=120})
	form.addSelectbox(windowValues,windowValue1,false,function(index) windowValue1=index system.pSave("windowValue1",windowValue1) end,{width=192})
	form.addRow(2)
	form.addLabel({label="Window Value 2",width=120})
	form.addSelectbox(windowValues,windowValue2,false,function(index) windowValue2=index system.pSave("windowValue2",windowValue2) end,{width=192})
	form.addLabel()
	form.addLabel({label="Sensors",font=FONT_BOLD})
	form.addRow(2)
	form.addLabel({label="Altitude [m]",width=134})
	form.addSelectbox(sensorLabels,1,true,function(index) altitudeSensorID=sensorIDs[index] system.pSave("altitudeSensorID",altitudeSensorID) altitudeSensorParam=sensorParams[index] system.pSave("altitudeSensorParam",altitudeSensorParam) end,{width=178})
	form.addRow(3)
	form.addLabel({label="Distance",width=69})
	form.addSelectbox(distanceUnits,distanceUnit,false,function(index) distanceUnit=index system.pSave("distanceUnit",distanceUnit) end,{width=65})
	form.addSelectbox(sensorLabels,1,true,function(index) distanceSensorID=sensorIDs[index] system.pSave("distanceSensorID",distanceSensorID) distanceSensorParam=sensorParams[index] system.pSave("distanceSensorParam",distanceSensorParam) end,{width=178})
end
local function init(code)
	startStopSwitch=system.pLoad("startStopSwitch")
	windowValue1=system.pLoad("windowValue1")
	if not windowValue1 then windowValue1=1 end
	windowValue2=system.pLoad("windowValue2")
	if not windowValue2 then windowValue2=2 end
	altitudeSensorID=system.pLoad("altitudeSensorID",1)
	altitudeSensorParam=system.pLoad("altitudeSensorParam",1)
	distanceSensorID=system.pLoad("distanceSensorID",1)
	distanceSensorParam=system.pLoad("distanceSensorParam",1)
	distanceUnit=system.pLoad("distanceUnit")
	if not distanceUnit then distanceUnit=1	end
	initSensors()
	
	system.registerTelemetry(1,"Glide Performance Window",2,printWindow)
	system.registerTelemetry(2,"Glide Performance Table",4,printTable)
	system.registerForm(1,MENU_APPS,"Glide Performance",createForm)
	collectgarbage()	
end
local function loop()
	if not startStopSwitch then return end
	local startStopSwitchStateOld=startStopSwitchState
	startStopSwitchState=system.getInputsVal(startStopSwitch)

	if startStopSwitchState>0 then
		local timeNow=system.getTimeCounter()
		local telSensors=system.getSensors()
		local altitudeSensor=system.getSensorByID(altitudeSensorID,altitudeSensorParam)
		local distanceSensor=system.getSensorByID(distanceSensorID,distanceSensorParam)
		
		if startStopSwitchStateOld<=0 then
			timeStart,altitudeStart,distanceStart=timeNow,nil,nil
			if altitudeSensor then altitudeStart=altitudeSensor.value end
			if distanceSensor then distanceStart=distanceSensor.value end
			
			table.insert(duration,1,-1)
			table.insert(sinkRate,1,-1)
			table.insert(airspeed,1,-1)
			table.insert(glideRatio,1,-1)
			
			if #duration==9 then
				table.remove(duration,9)
				table.remove(sinkRate,9)
				table.remove(airspeed,9)
				table.remove(glideRatio,9)
			end
		else
			duration[1]=(timeNow-timeStart)/1000
			if altitudeSensor then sinkRate[1]=(altitudeStart-altitudeSensor.value)/duration[1] end
			if distanceSensor then
				airspeed[1]=(distanceSensor.value-distanceStart)/duration[1]
				if distanceUnit==2 then airspeed[1]=airspeed[1]*1000 end
			end
			if altitudeSensor and distanceSensor then
				glideRatio[1]=(distanceSensor.value-distanceStart)/(altitudeStart-altitudeSensor.value)
				if distanceUnit==2 then glideRatio[1]=glideRatio[1]*1000 end
			end
		end
	end
	collectgarbage()
end

collectgarbage()
return {init=init,loop=loop,author="LD",version="2.0",name="Glide Performance"}