Refactor Plan to include pen up/down positions.

[jedahan]

Scratchpad discussion for refactoring to move pen positions out from the individual motions, to the plan

/// current data in Plan class
class Plan {
  motions: Array<XYMotion|PenMotion>
}

class PenMotion {
  public initialPos: number;
  public finalPos: number;
  public pDuration: number;
}

I would suggest the following refactoring

• Remove pDuration from PenMotion, and when executing motions, calculate the duration based on the current known position
• Remove initialPos from PenMotion, as it is ignored when executing the S2 ebb command
• Remove finalPos, and add a PenDirection enum that is either UP or DOWN
• Store the pen up and down positions in the Plan, and index on the newly created direction enum

class Plan {
  motions: Array<XYMotion|PenMotion>
  positions: {
    up: number
    down: number
  }
}

enum PenDirection { UP: "UP", DOWN: "DOWN" }

Speculated impact

• We no longer need the hack in the fast replanning - we can just add penUp and moveToOrigin to the plan executor
• We no longer have the ability to move the pen to arbitrary positions in the plan, only whatever up/down is defined
• We can remove a large amount of code
• Less memory usage during serialization
• More CPU used during execution

What else should we consider?