module Day5 where

import Debug.Trace
import Data.Char
import Data.List
import Util

type Range = (Int,Int)

parse :: String -> ([Range], [Int])
parse s = foldl addLine ([], []) $ map (map read) $ map (splitOn (not . isDigit)) $ lines s
  where addLine (ranges, queries) [lhs, rhs] = ((lhs, rhs) : ranges, queries)
        addLine (ranges, queries) [q] = (ranges, q : queries)
        addLine (ranges, queries) [] = (ranges, queries)

inRange :: Range -> Int -> Bool
inRange (lo,hi) q = lo <= q && q <= hi

inRanges :: [Range] -> Int -> Bool
inRanges rs q = any (\r -> inRange r q) rs

part1 :: String -> String
part1 input =
  let (rs,qs) = parse input
   in show $
      length $
      filter (inRanges rs) qs

rangeUnion :: [Range] -> [Range]
rangeUnion rs =
  let mergeWith cur [] = [cur]
      mergeWith (lo,hi) ((lo',hi') : rest) =
        if lo' <= hi then
          mergeWith (lo, max hi hi') rest
        else
          (lo, hi) : mergeWith (lo', hi') rest

      merge [] = []
      merge (r : rest) = mergeWith r rest
   in merge $ sort rs

part2 :: String -> String
part2 input =
  let (rs, _) = parse input
   in show $
      sum $
      map (\(a,b) -> b-a+1) $
      rangeUnion rs