import std/[strutils, sequtils, strformat, sugar]

let input = readFile("day_05/input.txt")

type Stacks = seq[seq[char]]

proc readStacks(data: string): Stacks =
  let lines = data.splitLines()
  let count = lines[lines.len - 1].split("   ").len
  var stacks = newSeqWith[char](count, newSeq[char]())
  for line in 0..lines.len-2:
    for stack in 0..count-1:
      let crate = lines[line][stack*4..stack*4+2]
      if not crate.isEmptyOrWhitespace:
        stacks[stack].insert(lines[line][stack*4+1..stack*4+1])
  return stacks

#region debug-only
proc echoStacks(stacks: Stacks) =
  var height = stacks.mapIt(it.len).max()
  while height > 0:
    height -= 1
    var line = ""
    for i in 0..stacks.len-1:
      if height < stacks[i].len:
        # let item = stacks[i][height]
        line.add fmt"[{stacks[i][height]}] "
      else:
        line.add fmt"    "
    echo line
  var line = ""
  for i in 0..stacks.len-1:
    line.add fmt" {i+1}  "
  echo line
#endregion debug-only

proc moveCrate(stacks: var Stacks, operation: string, preserveOrder: bool = false) =
  let tokens = operation.split(" ")
  assert tokens[0] == "move"
  let amount = tokens[1].parseInt
  assert tokens[2] == "from"
  let fromStack = tokens[3].parseInt - 1
  assert tokens[4] == "to"
  let toStack = tokens[5].parseInt - 1

  if preserveOrder:
    var moving = (0..amount-1).toSeq.mapIt(stacks[fromStack].pop)
    for crate in 0..amount-1:
      stacks[toStack].add(moving.pop)
    return
  
  for i in 0..amount-1:
    stacks[toStack].add(stacks[fromStack].pop)

proc solvePart1() =
  let inputData = input.split("\n\n")
  var stacks = readStacks(inputData[0])
  for operation in inputData[1].splitLines:
    stacks.moveCrate(operation)
  
  stacks.echoStacks
  echo stacks.mapIt(it[it.len - 1]).foldl(a & b, "")

proc solvePart2() =
  let inputData = input.split("\n\n")
  var stacks = readStacks(inputData[0])
  for operation in inputData[1].splitLines:
    stacks.moveCrate(operation, true)
  
  stacks.echoStacks
  echo stacks.mapIt(it[it.len - 1]).foldl(a & b, "")

if isMainModule:
  solvePart1()
  solvePart2()