SET turnOnEngine TO 1.0.
SET turnOffEngine TO 0.0.
SET turnReverseEngine TO -1.0.
SET suicideBurnDone TO FALSE.

CLEARSCREEN.
PRINT "Initiating landing code".

RCS ON.
SAS OFF.


PRINT "Prepare to nullify horizontal speed".

SET mysteer TO ship:retrograde.
LOCK STEERING TO mysteer. 
PRINT "mysteer " + mysteer.

SET SHIP:CONTROL:FORE TO turnOnEngine.
WAIT 4.
LOCK THROTTLE TO turnOnEngine.  
SET SHIP:CONTROL:FORE TO 0. 

//TODO detect of the groundspeed is rising. If it is, cut off the
UNTIL SHIP:GROUNDSPEED < 10 {
	SET mysteer TO ship:retrograde.
	WAIT 0.3.
}
LOCK THROTTLE TO turnOffEngine. 

PRINT "Horizontal speed cancelled".	

//Acquire retrograde direction and hold 
LOCK steering TO SHIP:RETROGRADE.
WAIT 3.
PRINT "Lander realigned".
PRINT "Descending".
LEGS ON.

//TODO remove excess horizontal speed using rcs

LOCK height to ALT:RADAR.

UNTIL height < 10 {
	
	PRINT "Altitude to start: " + altitude_to_start_suicide_burn AT(0,20). 
	SET mysteer TO ship:retrograde.
	
	IF (height < (altitude_to_start_suicide_burn +1000) AND suicideBurnDone = FALSE) {
		SET SHIP:CONTROL:FORE TO turnOnEngine.
		WAIT 2.
		LOCK THROTTLE TO turnOnEngine. 
		SET suicideBurnDone TO true.
	}	
	IF (height < (altitude_to_start_suicide_burn +1000) AND SHIP:VERTICALSPEED > -1 AND suicideBurnDone = TRUE){
		SET SHIP:CONTROL:FORE TO turnOffEngine.
		LOCK THROTTLE TO turnOffEngine. 
	}	
	
	IF (height < 1000 AND SHIP:VERTICALSPEED < -5){
		PRINT "Descent3 - Ver:" +  ROUND(SHIP:VERTICALSPEED,1).	
		SET SHIP:CONTROL:FORE TO turnOnEngine.
	}
	IF (height < 1000 AND SHIP:VERTICALSPEED > -1){
		PRINT "Descent4 - Ver:" +  ROUND(SHIP:VERTICALSPEED,1).	
		SET SHIP:CONTROL:FORE TO turnOffEngine.
	}
	
	IF (height < 50 AND SHIP:VERTICALSPEED < -2){
		PRINT "Descent5 - Ver:" +  ROUND(SHIP:VERTICALSPEED,1).	
		SET SHIP:CONTROL:FORE TO turnOnEngine.
	}
	IF (height < 50 AND SHIP:VERTICALSPEED > -1){
		PRINT "Descent6 - Ver:" +  ROUND(SHIP:VERTICALSPEED,1).	
		SET SHIP:CONTROL:FORE TO turnOffEngine.
	}
}.

LOCK THROTTLE TO turnOffEngine. 
SET SHIP:CONTROL:FORE TO turnOffEngine.
RCS OFF.
SAS OFF.

function altitude_to_start_suicide_burn {
	//(altitude to start suicide burn) = [ (current altitude)(acceleration of gravity) + (1/2)(current velocity)2 ] / (acceleration of engines)
	  
	declare local goal to (ALT:RADAR * -gravity_calculator + (1/2) * SHIP:VERTICALSPEED^2) / ship:maxthrust.
	return goal.
}.

function gravity_calculator {
	declare local GM to ship:body:mu.
	declare local R to (body:radius + ship:altitude).
	declare local g to GM/(R^2).
	return -g.
}.