runoncepath("lib/throttle").
runoncepath("lib/navigation").

parameter APOAPSIS_TARGET is 80000.
parameter GRAVITY_TURN_START is 8000.
parameter GRAVITY_PITCH is 75.
parameter INITIAL_PITCH is 85.
parameter MINIMUM_PITCH is 5.

local ATMO_TWR is 1.6.

// Configure subsystems.
RCS off.
SAS off.

// Countdowns are cute.
print "Initiating automated launch sequence.".
from { local x is 5. } until x = 0 step { set x to x - 1. } do {
  print "..." + x.
  wait 0.5.
}

// Hold throttle to maintain 1.5 TWR.
// We do *not* use a PID Loop here because we can
// calculate the correct value discretely.
lock THROTTLE to ThrottleToTWR(ATMO_TWR).
print "Throttling to maintain a TWR  of " + ATMO_TWR.

// Main ascent control.
lock STEERING to heading(90,90,270).
stage.
wait until SHIP:ALTITUDE > 200.

print "Vectoring away from launchpad.".
lock STEERING to heading(90, INITIAL_PITCH, 270).
wait until SHIP:ALTITUDE > GRAVITY_TURN_START.

print "Pitching for gravity turn.".
// Pitch over...
lock STEERING to heading(90, GRAVITY_PITCH, 270).
// Wait until we have rotated to (approximately) that pitch...
wait until vectorangle(
  SHIP:FACING:FOREVECTOR,
  STEERINGMANAGER:TARGET:FOREVECTOR)
  < 0.5.

// then wait until Prograde catches up (or passes us).
local targetPitch is GetPitch(STEERINGMANAGER:TARGET:FOREVECTOR).
wait until GetPitch(SHIP:SRFPROGRADE:FOREVECTOR) <= targetPitch.

print "Locking to prograde, letting gravity do the hard work.".
lock STEERING to GetAscentVector(MINIMUM_PITCH).
wait until SHIP:ALTITUDE > 32000. // todo: if we have a pressure sensor we can use it to decide when to kick the throttle up instead, neat solution for e.g. Duna and Eve.

lock THROTTLE to 1.0.
wait until SHIP:ORBIT:APOAPSIS > APOAPSIS_TARGET.

lock THROTTLE to 0.0.
set SHIP:CONTROL:PILOTMAINTHROTTLE to 0.
wait 0.001. // make sure these control updates get applied

print "Target apoapsis acquired. Creating maneuver node.".
add CreateCircularizationNode().
runpath("/rocket/execnode").
print "Orbit acquired. Releasing controls. Good luck, Kerman.".
unlock THROTTLE.
unlock STEERING.
SAS on.