Uiua

Part one was simple enough. Part two nearly made me give up.
Part two has the most ugly and least performant code I’ve made in uiua so far but it gets the job done and that’s all I care about for now.

Run with example input here

RotateClock ← (
  ⊙⊙(⍉⇌)
  ⊙(⇌⍜(⊡0)(-⊙(⧻⊡0.)+1))
  ↻¯1
)

RotateCounter ← (
  ⊙⊙(⇌⍉)
  ⊙(⍜(⊡0)(-⊙(⧻.)+1)⇌)
  ↻1
)

NewPos ← (
  ⊙⍜(⊙⊡:)(-1+⊙(⊗@#)⟜↘⊙.)⟜°⊟
  ⍜(⊡1)⋅
)

MarkPath ← (
  RotateClock
  ⍢( # replace characters up til next '#'
    ⊙(⊙⍜(↘⊙⊡:)(⍜(↙)(▽:@^⧻)⊗@#.)⟜°⊟
      NewPos
    )
    RotateCounter
  | ⋅(≠0⊡0))
  ◌◌
)

PartOne ← (
  &rs ∞ &fo "input-6.txt"
  ⊜∘≠@\n.
  # maybe make compatible with
  # non-up facing inputs
  ♭⊚=@^.
  [0 1 2 3]
  MarkPath
  &fwa "test.txt" json.
  /+/+=@^
)

PartTwo ← (
  &rs ∞ &fo "input-6.txt"
  ⊜∘≠@\n.
  # maybe make compatible with
  # non-up facing inputs
  ♭⊚=@^.
  [0 1 2 3]
  ◡MarkPath
  ⊙::
  # rotate the field to match the intital state
  ⊙⊙(
    ⊙(⊚=@#)
    ⍢(⇌⍉|¬≍⊚=@#)
    ⊙◌
  )
  ⊙⊙(⊚=@^.)
  ⊙⊙⊙¤∩¤
  ⊞(⊙⊙(⍜⊡⋅@#)
    RotateClock
    ⊙NewPos
    ¤¯1_¯1_¯1
    ⍢(⊙◡(⊂⊢)
      ⊂
      ⊙(RotateCounter
        ⊙NewPos
      )
    | =1+⊙(∈↘1⇌)◡⋅(≠129⊡2)⊙(⊂⊢))
    # 129 = length of input array. Hardcoded because
    # the condition block doesn't seem to get the
    # input array passed to it so the length can't
    # be read dynamically
    ⊙(⊂⊢)
    ∈
    ⊙◌
  )
  /+♭
)

&p "Day 6:"
&pf "Part 1: "
&p PartOne
&pf "Part 2: "
&p PartTwo