module Task1 (task1) where

import Common
import Control.Monad (join)
import Flow

type AllocatedBlock = (Int, Int)

task1 :: String -> IO Int
task1 input = let blocks = parseBlocks input
                  compacted = compact blocks
              in do
                -- print blocks
                -- print compacted
                -- print $ showBlocks compacted
                return $ reduce 0 compacted
  where
    compact :: [Block] -> [AllocatedBlock]
    compact blocks = compactInner blocks (reverse blocks) (minBound :: Int)
      where
        compactInner :: [Block] -> [Block] -> Int -> [AllocatedBlock]
        compactInner [] _ _ = []
        compactInner _ [] _ = error "Backwards list cannot be empty when forwards list isn't"
        compactInner forwards ((Empty, _):backwards) curBId = compactInner forwards backwards curBId
        compactInner forwards ((Allocated _, 0):backwards) curBId = compactInner forwards backwards curBId
        compactInner ((Empty, 0):forwards) backwards curBId = compactInner forwards backwards curBId
        compactInner ((Empty, fLength):forwards) ((Allocated bId, bLength):backwards) _
          | bLength <= fLength = (bId, bLength) : compactInner ((Empty, fLength - bLength) : forwards) backwards bId
          | otherwise = (bId, fLength) : compactInner forwards ((Allocated bId, bLength - fLength):backwards) bId
        compactInner ((Allocated fId, fLength):forwards) bAll@((Allocated bId, bLength):_) curBId
          | fId >= bId = [(bId, bLength)]
          | otherwise = (fId, fLength) : compactInner forwards bAll curBId

    reduce :: Int -> [AllocatedBlock] -> Int
    reduce _ [] = 0
    reduce i ((_, 0): blocks) = reduce i blocks
    reduce i ((bId, bSize):blocks) = i * bId + reduce (i + 1) ((bId, bSize - 1):blocks)

    showBlocks :: [AllocatedBlock] -> String
    showBlocks [] = ""
    showBlocks ((blockId, blockLength):blocks) = (show blockId |> repeat |> take blockLength |> join) ++ showBlocks blocks