# Towers of Hanoi Formula
#
# Demonstrates that molecule algebra solves the "million step workflow" problem.
# LLMs fail on long sequences because errors accumulate (99.9%^1000 ≈ 37% success).
# MAKER used voting to reduce error. We use mechanical structure instead.
#
# Key insight: The move sequence is deterministic. Only execution needs AI.
# And each step is trivial: "move disk X from peg Y to peg Z".
#
# For n disks: 2^n - 1 moves
# 20 disks = 1,048,575 moves (the "million step" problem)
#
# The iterative algorithm (no recursion needed):
# For move k (1-indexed):
#   - disk = largest power of 2 dividing k (disk 1 is smallest)
#   - direction = computed from disk parity and move number
#
# This formula uses for-each to generate all moves at cook time.

formula: towers-of-hanoi
description: >
  Solve Towers of Hanoi for {disks} disks. Generates 2^{disks} - 1 steps,
  each a trivial move operation. Demonstrates mechanical structure generation
  for arbitrarily long workflows.
version: 1

vars:
  disks: "{{disks}}"
  source_peg: "A"
  target_peg: "C"
  auxiliary_peg: "B"

# The magic: for-each over computed move sequence
# Each move is deterministic, computed from move number
generate:
  # This is pseudo-syntax for the runtime expansion we'd need
  for-each:
    var: move_num
    range: "1..2^{disks}"  # 1 to 2^n - 1
  step:
    id: "move-{move_num}"
    description: >
      Move {computed_disk} from {computed_source} to {computed_target}.

      This is move {move_num} of {total_moves}.
      Simply execute the move - no decision needed.
    needs:
      - "move-{move_num - 1}"  # Sequential dependency
    compute:
      # Disk to move: position of lowest set bit in move_num
      disk: "lowest_set_bit({move_num})"
      # Peg calculations based on disk parity and move number
      source: "peg_for_disk({disk}, {move_num}, 'source')"
      target: "peg_for_disk({disk}, {move_num}, 'target')"

# Alternatively, simpler recursive template for smaller N:
# (This would need the recursive expansion operator)

steps:
  - id: setup
    description: >
      Verify initial state: {disks} disks stacked on peg {source_peg}.
      All disks in order (largest on bottom).

  - id: solve
    description: >
      Execute all {total_moves} moves to transfer tower from
      {source_peg} to {target_peg}.
    needs: [setup]
    # This step would be expanded by the generate block above

  - id: verify
    description: >
      Verify final state: all {disks} disks now on peg {target_peg}.
      Tower intact, all moves were legal.
    needs: [solve]

# For the prototype, let's show a 3-disk example (7 moves):
example_3_disk:
  # Move sequence for 3 disks: A→C, A→B, C→B, A→C, B→A, B→C, A→C
  steps:
    - id: move-1
      description: "Move disk 1 from A to C"
    - id: move-2
      description: "Move disk 2 from A to B"
      needs: [move-1]
    - id: move-3
      description: "Move disk 1 from C to B"
      needs: [move-2]
    - id: move-4
      description: "Move disk 3 from A to C"
      needs: [move-3]
    - id: move-5
      description: "Move disk 1 from B to A"
      needs: [move-4]
    - id: move-6
      description: "Move disk 2 from B to C"
      needs: [move-5]
    - id: move-7
      description: "Move disk 1 from A to C"
      needs: [move-6]