Add --new flag for creating new files for the next day

Sources/AdventOfCode.swift

@@ -1,15 +1,44 @@
 import ArgumentParser
+import Foundation
 
 // Add each new day implementation to this array:
 let allChallenges: [any AdventDay] = [
-  Day00()
+  Day00(),
+//  Day01(),
+//  Day02(),
+//  Day03(),
+//  Day04(),
+//  Day05(),
+//  Day06(),
+//  Day07(),
+//  Day08(),
+//  Day09(),
+//  Day10(),
+//  Day11(),
+//  Day12(),
+//  Day13(),
+//  Day14(),
+//  Day15(),
+//  Day16(),
+//  Day17(),
+//  Day18(),
+//  Day19(),
+//  Day20(),
+//  Day21(),
+//  Day22(),
+//  Day23(),
+//  Day24(),
+//  Day25(),
 ]
 
 @main
 struct AdventOfCode: AsyncParsableCommand {
   @Argument(help: "The day of the challenge. For December 1st, use '1'.")
   var day: Int?
 
+  @Flag(help: "Create new code, data, and test files for the next day.")
+  var new: Bool = false
+
   @Flag(help: "Benchmark the time taken by the solution")
   var benchmark: Bool = false
 
@@ -57,6 +86,16 @@ struct AdventOfCode: AsyncParsableCommand {
   }
 
   func run() async throws {
+    if self.new {
+      let day = (allChallenges.last?.day ?? 0) + 1
+      try createFiles(for: day)
+      let year = Calendar(identifier: .gregorian).component(.year, from: Date())
+      try uncommentAllChallenges(for: day)
+      print("See your question at https://adventofcode.com/\(year)/day/\(day)")
+      print("Good luck!")
+      return
+    }
+
     let challenges =
       if all {
         allChallenges
@@ -78,4 +117,49 @@ struct AdventOfCode: AsyncParsableCommand {
       }
     }
   }
+
+  private func createFiles(for day: Int) throws {
+    let fileManager = FileManager.default
+    let currentPath = fileManager.currentDirectoryPath
+    let className = String(format: "Day%02d", Int(day))
+
+    // Data file
+    let newDataFilePath = "\(currentPath)/Sources/Data/\(className).txt"
+    try createFile(atPath: newDataFilePath, content: "")
+
+    // Code file
+    let templateFilePath = "\(currentPath)/Sources/DayTemplate.swift"
+    let newCodeFilePath = "\(currentPath)/Sources/\(className).swift"
+    let newCodeFileContent = try String(contentsOfFile: templateFilePath, encoding: .utf8)
+      .replacingOccurrences(of: "DayTemplate", with: className)
+    try createFile(atPath: newCodeFilePath, content: newCodeFileContent)
+
+    // Test file
+    let templateTestFilePath = "\(currentPath)/Tests/DayTemplate.swift"
+    let newTestFilePath = "\(currentPath)/Tests/\(className).swift"
+    let newTestFileContent = try String(contentsOfFile: templateTestFilePath, encoding: .utf8)
+      .replacingOccurrences(of: "DayTemplate", with: className)
+    try createFile(atPath: newTestFilePath, content: newTestFileContent)
+  }
+
+  private func createFile(atPath path: String, content: String) throws {
+    let fileManager = FileManager.default
+    guard !fileManager.fileExists(atPath: path) else {
+      fatalError("File already exists at \(path).")
+    }
+    try content.write(toFile: path, atomically: true, encoding: .utf8)
+    print("Created \(path)")
+  }
+
+  private func uncommentAllChallenges(for day: Int) throws {
+    let fileManager = FileManager.default
+    let currentPath = fileManager.currentDirectoryPath
+    let filePath = "\(currentPath)/Sources/AdventOfCode.swift"
+    let className = String(format: "Day%02d", Int(day))
+
+    let fileContent = try String(contentsOfFile: filePath, encoding: .utf8)
+    let newFileContent = fileContent.replacingOccurrences(of: "//  \(className)()", with: "  \(className)()")
+    try newFileContent.write(toFile: filePath, atomically: true, encoding: .utf8)
+  }
+
 }

Sources/DayTemplate.swift

@@ -0,0 +1,16 @@
+import Foundation
+
+final class DayTemplate: AdventDay {
+
+  init(data: String) {
+  }
+
+  func part1() -> Any {
+    return 0
+  }
+
+  func part2() -> Any {
+    return 0
+  }
+
+}

Tests/DayTemplate.swift

@@ -0,0 +1,21 @@
+import Testing
+
+@testable import AdventOfCode
+
+final class DayTemplateTests {
+
+  let testData = """
+
+    """
+
+  @Test func testPart1() async throws {
+    let challenge = DayTemplate(data: testData)
+    #expect(String(describing: challenge.part1()) == "")
+  }
+
+  @Test func testPart2() async throws {
+    let challenge = DayTemplate(data: testData)
+    #expect(String(describing: challenge.part2()) == "")
+  }
+
+}