aoc2021/Sources/02/02.swift

//
//  File.swift
//  
//
//  Created by Max Nuding on 02.12.21.
//

import Foundation
import Runner

enum Direction: String {
    case forward
    case down
    case up
    init?(rawValue: String) {
        switch rawValue {
        case "forward":
            self = .forward
        case "down":
            self = .down
        case "up":
            self = .up
        default:
            return nil
        }
    }
}

struct MoveCommand {
    let direction: Direction
    let amount: Int
    
    init?(line: String) {
        guard !line.isEmpty else {
            return nil
        }
        let parts = line.components(separatedBy: .whitespaces)
        direction = Direction(rawValue: parts[0])!
        amount = Int(parts[1])!
    }
}

struct Day02: Runnable {
    let inputPath: String
    
    
    func run() {
        let input = try! String(contentsOfFile: inputPath)
        let commands = input
            .components(separatedBy: .newlines)
            .compactMap { MoveCommand(line: $0) }
        runA(commands: commands)
        runB(commands: commands)
    }
    
    func runA(commands: [MoveCommand]) {
        var horizontalPos = 0
        var depth = 0
        for command in commands {
            switch command.direction {
            case .forward:
                horizontalPos += command.amount
            case .up:
                depth -= command.amount
            case .down:
                depth += command.amount
            }
        }
        print(horizontalPos * depth)
    }
    
    func runB(commands: [MoveCommand]) {
        var horizontalPos = 0
        var depth = 0
        var aim = 0
        for command in commands {
            switch command.direction {
            case .forward:
                horizontalPos += command.amount
                depth += aim * command.amount
            case .up:
                aim -= command.amount
            case .down:
                aim += command.amount
            }
        }
        print(horizontalPos * depth)
    }
}