aoc-2019/06/main.pony

use "collections"
use "files"
use "format"
use "itertools"

class Orbit
  let _name: String
  var _orbits: Array[Orbit ref]

  new create(n: String) =>
    _name = n
    _orbits = Array[Orbit]()

  fun ref add(o: Orbit ref) =>
    _orbits.push(o)

  fun name(): String => _name

  fun print(env: Env) =>
    env.out.write(_name + ":")
    for o in _orbits.values() do
      env.out.write(" " + o.name())
    end
    env.out.print("")

  fun checksum(path_len: USize): USize =>
    var sum = path_len
    for o in _orbits.values() do
      sum = sum + o.checksum(path_len + 1)
    end
    sum

  fun ref contains(n: String): Bool =>
    (n == _name) or (Iter[Orbit](_orbits.values()).any({(o) => o.contains(n)}))

  fun ref closest_parent(l: String, r: String): String ? =>
    for o in _orbits.values() do
      try
        return o.closest_parent(l, r)?
      end
    end
    if contains(l) and contains(r) then
      return _name
    end
    error

  fun ref find_distance(n: String, dist: USize = 0): USize ? =>
    if n == _name then
      return dist
    end
    for o in _orbits.values() do
      try
        return o.find_distance(n, dist + 1)?
      end
    end
    error

class System
  var orbits: Map[String, Orbit]

  new create(mapping: Array[(String, String)]) =>
    orbits = Map[String, Orbit]()

    orbits.insert("COM", Orbit("COM"))
    for (inner_name, outer_name) in mapping.values() do
      let outer = orbits.insert_if_absent(outer_name, Orbit(outer_name))
      let inner = orbits.insert_if_absent(inner_name, Orbit(inner_name))
      inner.add(outer)
    end

  fun print(env: Env) =>
    for o in orbits.values() do
      o.print(env)
    end

  fun checksum(): USize =>
    try
      orbits("COM")?.checksum(0)
    else
      0
    end

  fun ref closest_parent(l: String, r: String): (String | None) =>
    try
      orbits("COM")?.closest_parent(l, r)?
    else
      None
    end

  fun ref distance(parent: String, child: String): USize =>
    try
      orbits(parent)?.find_distance(child)?
    else
      0
    end

actor Main
  new create(env: Env) =>
    let caps = recover val FileCaps.>set(FileRead).>set(FileStat) end

    let target_file = try env.args(1)? else "input.txt" end
    try
      with
        file = OpenFile(FilePath(env.root as AmbientAuth, target_file, caps)?) as File
      do
      let mapping = Array[(String, String)]()
      for line in file.lines() do
        try
          let sline = line.split(")")
          mapping.push((sline(0)?, sline(1)?))
        else
          env.out.write("Failed to parse line: " + line.clone())
        end
      end
      let s = System(mapping)
      env.out.print("Checksum: " + Format.int[USize](s.checksum()))
      s.print(env)
      match s.closest_parent("YOU", "SAN")
        | None => env.out.print("No connection between the two somehow?")
        | let o: String =>
        env.out.print("Closest parent between YOU and SAN is " + o)
        let d1 = s.distance(o, "YOU")
        let d2 = s.distance(o, "SAN")
        env.out.print("Distance is " + Format.int[USize]((d1 + d2) - 2))
      end
      end
    end