Coverage Summary for Class: Direction (day10p1)

 package day10p1
 
 import day10p1.Direction.*
 
 fun String.toPipeMap(): PipeMap {
   val startCoordinate = findStartCoordinate()
   val lines = lines()
   val startPipeType = lines.calcPipeType(startCoordinate)
   return PipeMap(
     pipes = lines.mapIndexed { row, line ->
       line.mapIndexed { column, ch ->
         val coordinate = Coordinate(row, column)
         if (coordinate == startCoordinate) startPipeType else ch.toPipeType()
       }
     },
     startCoordinate = startCoordinate
   )
 }
 
 data class PipeMap(val pipes: List<List<PipeType>>, val startCoordinate: Coordinate) {
   val numberOfRows = pipes.size
   val numberOfColumns = pipes[0].size
   operator fun get(coordinate: Coordinate): PipeType = pipes[coordinate.row][coordinate.column]
   fun findNumberOfStepsToFarthestPointInLoop(): Long {
     val reachMap = Array(numberOfRows) { arrayOfNulls<Long>(numberOfColumns) }
 
     val queue = mutableListOf(startCoordinate)
     reachMap[startCoordinate.row][startCoordinate.column] = 0L
 
     while (queue.isNotEmpty()) {
       val coordinate = queue.removeFirst()!!
       val numOfSteps = reachMap[coordinate.row][coordinate.column]!! + 1
       for (direction in pipes[coordinate.row][coordinate.column].directions) {
         val newCoordinate = direction(coordinate)
         if (newCoordinate.row < 0 || newCoordinate.row >= this.numberOfRows) continue
         if (newCoordinate.column < 0 || newCoordinate.column >= this.numberOfColumns) continue
         val existingNumOfSteps = reachMap[newCoordinate.row][newCoordinate.column]
         if (existingNumOfSteps != null) return if (existingNumOfSteps == numOfSteps) existingNumOfSteps else continue
         reachMap[newCoordinate.row][newCoordinate.column] = numOfSteps
         queue.add(newCoordinate)
       }
     }
 
     error("Didn't find farthest point")
   }
 }
 
 fun List<String>.calcPipeType(coordinate: Coordinate): PipeType {
   val directions = Direction.entries.asSequence().filter { direction ->
     val newCoordinate = direction(coordinate)
     if (newCoordinate.row < 0 || newCoordinate.row >= this.size) return@filter false
 
     val line = this[newCoordinate.row]
     if (newCoordinate.column < 0 || newCoordinate.column >= line.length) return@filter false
 
     val pipeType = line[newCoordinate.column].toPipeType()
     pipeType.directions.any { it.reverse == direction }
   }.toSet()
 
   val candidates = PipeType.entries.filter { it.directions == directions }
 
   require(candidates.size == 1)
 
   return candidates.first()
 }
 
 fun String.findStartCoordinate(): Coordinate = lineSequence().flatMapIndexed { row: Int, line: String ->
   line.mapIndexed { column: Int, char: Char -> Coordinate(row, column) to char }
 }.first { (_, char) -> char == 'S' }.first
 
 fun Char.toPipeType(): PipeType = when (this) {
   '|' -> PipeType.`|`
   '-' -> PipeType.`-`
   'L' -> PipeType.L
   'J' -> PipeType.J
   '7' -> PipeType.`7`
   'F' -> PipeType.F
   else -> PipeType.dot
 }
 
 enum class PipeType(val directions: Set<Direction>) {
   `|`(setOf(north, south)),
   `-`(setOf(east, west)),
   L(setOf(north, east)),
   J(setOf(north, west)),
   `7`(setOf(south, west)),
   F(setOf(south, east)),
   dot(emptySet());
 }
 
 enum class Direction {
   north {
     override operator fun invoke(coordinate: Coordinate) = coordinate.copy(row = coordinate.row - 1)
 
     override val reverse: Direction get() = south
   },
   south {
     override operator fun invoke(coordinate: Coordinate) = coordinate.copy(row = coordinate.row + 1)
 
     override val reverse: Direction get() = north
   },
   east {
     override operator fun invoke(coordinate: Coordinate) = coordinate.copy(column = coordinate.column + 1)
 
     override val reverse: Direction get() = west
   },
   west {
     override operator fun invoke(coordinate: Coordinate) = coordinate.copy(column = coordinate.column - 1)
 
     override val reverse: Direction get() = east
   };
 
   abstract operator fun invoke(coordinate: Coordinate): Coordinate
 
   abstract val reverse: Direction
 }
 
 data class Coordinate(val row: Int, val column: Int)