module Part2 where

import Commons


getNumberNeighbors :: Coordinates -> [NumberPart] -> Int
getNumberNeighbors _ [] = 0
getNumberNeighbors symbolCoordinates (h: t)
  | symbolCoordinates `elem` neighbors h = 1 + getNumberNeighbors symbolCoordinates t
  | otherwise = getNumberNeighbors symbolCoordinates t

isGear :: SymbolPart -> [NumberPart] -> Bool
isGear symbolPart numberParts | symbol symbolPart == '*' = getNumberNeighbors (coordinates symbolPart) numberParts == 2
                              | otherwise = False

getRatioNeighbors :: Coordinates -> [NumberPart] -> Int
getRatioNeighbors _ [] = 1
getRatioNeighbors symbolCoordinates (h: t)
  | symbolCoordinates `elem` neighbors h = value h * getRatioNeighbors symbolCoordinates t
  | otherwise = getRatioNeighbors symbolCoordinates t

getGearRatio :: SymbolPart -> [NumberPart] -> Int
getGearRatio symbolPart numberParts
  | isGear symbolPart numberParts = getRatioNeighbors (coordinates symbolPart) numberParts
  | otherwise = 0

getGearRatios :: [SymbolPart] -> [NumberPart] -> [Int]
getGearRatios [] _ = []
getGearRatios (h: t) numberParts = let gearRatio = getGearRatio h numberParts
                                   in if gearRatio > 0
                                         then gearRatio: getGearRatios t numberParts
                                         else getGearRatios t numberParts

getGearRatiosFromEngine :: Engine -> [Int]
getGearRatiosFromEngine engine = getGearRatios (symbols engine) (numbers engine)