/*
--- Part Two ---

It turns out that this circuit is very timing-sensitive; you actually need to minimize the signal
delay.

To do this, calculate the number of steps each wire takes to reach each intersection; choose the
intersection where the sum of both wires' steps is lowest. If a wire visits a position on the grid
multiple times, use the steps value from the first time it visits that position when calculating the
total value of a specific intersection.

The number of steps a wire takes is the total number of grid squares the wire has entered to get to
that location, including the intersection being considered. Again consider the example from above:

...........
.+-----+...
.|.....|...
.|..+--X-+.
.|..|..|.|.
.|.-X--+.|.
.|..|....|.
.|.......|.
.o-------+.
...........

In the above example, the intersection closest to the central port is reached after 8+5+5+2 = 20
steps by the first wire and 7+6+4+3 = 20 steps by the second wire for a total of 20+20 = 40 steps.

However, the top-right intersection is better: the first wire takes only 8+5+2 = 15 and the second
wire takes only 7+6+2 = 15, a total of 15+15 = 30 steps.

Here are the best steps for the extra examples from above:

- R75,D30,R83,U83,L12,D49,R71,U7,L72
  U62,R66,U55,R34,D71,R55,D58,R83 = 610 steps
- R98,U47,R26,D63,R33,U87,L62,D20,R33,U53,R51
  U98,R91,D20,R16,D67,R40,U7,R15,U6,R7 = 410 steps

What is the fewest combined steps the wires must take to reach an intersection?
*/

package com.curtislb.adventofcode.year2019.day03.part2

import com.curtislb.adventofcode.year2019.day03.wire.Wire
import java.nio.file.Path
import java.nio.file.Paths

/**
 * Returns the solution to the puzzle for 2019, day 3, part 2.
 *
 * @param inputPath The path to the input file for this puzzle.
 */
fun solve(inputPath: Path = Paths.get("..", "input", "input.txt")): Int? {
    val (wireA, wireB) = inputPath.toFile().readLines().subList(0, 2).map { Wire(it.trim()) }
    val (intersection, pathLength) = wireA shortestIntersect wireB
    return if (intersection != null) pathLength else null
}

fun main() = when (val solution = solve()) {
    null -> println("No intersection found.")
    else -> println(solution)
}
