collectgarbage()
local startStopSwitch
local startStopSwitchState=0
local valueIndexLeft,valueIndexRight
local altitudeSensorId,altitudeSensorParam
local distanceSensorId,distanceSensorParam
local distanceUnit

local valueNames={"Duration","Sink Rate","Airspeed","Glide Ratio"}
local valueUnits={"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 printColumnBox(x,valueIndex)
	local value="-"
	if #duration>0 then
		if valueIndex==4 then
			if glideRatio[1]>=0 then value=string.format("%.1f",glideRatio[1]) end
		elseif valueIndex==3 then
			if airspeed[1]>=0 then value=string.format("%.1f",airspeed[1]) end
		elseif valueIndex==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(x-lcd.getTextWidth(FONT_MINI,valueNames[valueIndex])/2,3,valueNames[valueIndex],FONT_MINI)
	lcd.drawText(x-lcd.getTextWidth(FONT_MINI,"["..valueUnits[valueIndex].."]")/2,15,"["..valueUnits[valueIndex].."]",FONT_MINI)
	lcd.drawText(x-lcd.getTextWidth(FONT_MAXI,value)/2,28,value,FONT_MAXI)
end
local function printBox()
	printColumnBox(38,valueIndexLeft)
	printColumnBox(113,valueIndexRight)
end
local function printCellTable(x,y,w,value,format)
	lcd.drawText(x+(w+1-lcd.getTextWidth(format,value))/2,y,value,format)
	return x+w
end
local function printRowTable(row,values,format)
	local x,y=-1,-1+row*18
	x=printCellTable(x,y,80,values[1],format)
	x=printCellTable(x,y,80,values[2],format)
	x=printCellTable(x,y,80,values[3],format)
	x=printCellTable(x,y,80,values[4],format)
	lcd.drawLine(0,y,320,y)
end
local function printTable()
	printRowTable(0,valueNames,FONT_BOLD)
	
	for i=1,#duration do
		local values={"-","-","-","-"}
		if duration[i]>=0 then values[1]=string.format("%d ",duration[i])..valueUnits[1] end
		if sinkRate[i]>=0 then values[2]=string.format("%.2f ",sinkRate[i])..valueUnits[2] end
		if airspeed[i]>=0 then values[3]=string.format("%.1f ",airspeed[i])..valueUnits[3] end
		if glideRatio[i]>=0 then values[4]=string.format("%.1f ",glideRatio[i])..valueUnits[4] end
		
		printRowTable(i,values,FONT_NORMAL)
	end
end
local function initSensors()
	local sensors=system.getSensors()
	sensorLabels={"..."}
	sensorIds={0}
	sensorParams={0}
	
	for i,sensor in ipairs(sensors) do
		if sensor.param>0 then
			table.insert(sensorLabels,sensor.sensorName..": "..sensor.label.." ["..sensor.unit.."]")
			table.insert(sensorIds,sensor.id)
			table.insert(sensorParams,sensor.param)
		end
	end
end
local function createForm(formID)
	initSensors()
	local altitudeSensorIndex,distanceSensorIndex=1,1
	for i=2,#sensorLabels do
		if altitudeSensorId==sensorIds[i] and altitudeSensorParam==sensorParams[i] then altitudeSensorIndex=i end
		if distanceSensorId==sensorIds[i] and distanceSensorParam==sensorParams[i] then distanceSensorIndex=i end
	end
	
	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="Box Value Left",width=120})
	form.addSelectbox(valueNames,valueIndexLeft,false,function(index) valueIndexLeft=index system.pSave("valueIndexLeft",valueIndexLeft) end,{width=192})
	form.addRow(2)
	form.addLabel({label="Box Value Right",width=120})
	form.addSelectbox(valueNames,valueIndexRight,false,function(index) valueIndexRight=index system.pSave("valueIndexRight",valueIndexRight) end,{width=192})
	form.addLabel()
	form.addLabel({label="Sensors",font=FONT_BOLD})
	form.addRow(2)
	form.addLabel({label="Altitude [m]",width=135})
	form.addSelectbox(sensorLabels,altitudeSensorIndex,true,function(index) altitudeSensorId=sensorIds[index] system.pSave("altitudeSensorId",altitudeSensorId) altitudeSensorParam=sensorParams[index] system.pSave("altitudeSensorParam",altitudeSensorParam) end,{width=177})
	form.addRow(3)
	form.addLabel({label="Distance",width=72})
	form.addSelectbox(distanceUnits,distanceUnit,false,function(index) distanceUnit=index system.pSave("distanceUnit",distanceUnit) end,{width=63})
	form.addSelectbox(sensorLabels,distanceSensorIndex,true,function(index) distanceSensorId=sensorIds[index] system.pSave("distanceSensorId",distanceSensorId) distanceSensorParam=sensorParams[index] system.pSave("distanceSensorParam",distanceSensorParam) end,{width=177})
	form.addRow(3)
end
local function init(code)
	startStopSwitch=system.pLoad("startStopSwitch")
	valueIndexLeft=system.pLoad("valueIndexLeft",1)
	valueIndexRight=system.pLoad("valueIndexRight",2)
	altitudeSensorId=system.pLoad("altitudeSensorId",0)
	altitudeSensorParam=system.pLoad("altitudeSensorParam",0)
	distanceSensorId=system.pLoad("distanceSensorId",0)
	distanceSensorParam=system.pLoad("distanceSensorParam",0)
	distanceUnit=system.pLoad("distanceUnit",1)
	
	system.registerTelemetry(1,"Glide Performance Box",2,printBox)
	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 altitudeSensor=system.getSensorValueByID(altitudeSensorId,altitudeSensorParam)
		local distanceSensor=system.getSensorValueByID(distanceSensorId,distanceSensorParam)
		
		if startStopSwitchStateOld<=0 then
			timeStart=timeNow
			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="2.1",name="Glide Performance"}