Various fix ups (#5)

* Add a --all command line option to run all days

* Switch answer type from Any to an associated type, defaulting to Int

* Switch to String(contentsOf:encoding:)

* Clarify new day instructions

README.md

@@ -33,8 +33,23 @@ The challenges assume three files (replace 00 with the day of the challenge).
 - `Sources/Day00.swift`: the code to solve the challenge
 - `Tests/Day00.swift`: any unit tests that you want to include
 
-To start a new day's challenge, make a copy of these files and update as
-necessary. The `AdventOfCode.swift` file controls which day's challenge is run
+To start a new day's challenge, make a copy of these files, updating 00 to the 
+day number.
+
+```diff
+// Add each new day implementation to this array:
+let allChallenges: [any AdventDay] = [
+-  Day00()
++  Day00(),
++  Day01(),
+]
+```
+
+Then implement part 1 and 2. The `AdventOfCode.swift` file controls which challenge
+is run with `swift run`. Add your new type to its `allChallenges` array. By default 
+it runs the most recent challenge.
+
+The `AdventOfCode.swift` file controls which day's challenge is run
 with `swift run`. By default that runs the most recent challenge in the package.
 
 To supply command line arguments use `swift run AdventOfCode`. For example,

Sources/AdventDay.swift

@@ -3,6 +3,8 @@
 import Foundation
 
 protocol AdventDay {
+  associatedtype Answer = Int
+
   /// The day of the Advent of Code challenge.
   ///
   /// You can implement this property, or, if your type is named with the
@@ -13,10 +15,15 @@ protocol AdventDay {
   init(data: String)
 
   /// Computes and returns the answer for part one.
-  func part1() async throws -> Any
+  func part1() async throws -> Answer
 
   /// Computes and returns the answer for part two.
-  func part2() async throws -> Any
+  func part2() async throws -> Answer
+}
+
+struct PartUnimplemented: Error {
+  let day: Int
+  let part: Int
 }
 
 extension AdventDay {
@@ -42,8 +49,8 @@ extension AdventDay {
 
   // Default implementation of `part2`, so there aren't interruptions before
   // working on `part1()`.
-  func part2() -> Any {
-    "Not implemented yet"
+  func part2() throws -> Answer {
+    throw PartUnimplemented(day: day, part: 2)
   }
 
   /// An initializer that loads the test data from the corresponding data file.
@@ -60,12 +67,12 @@ extension AdventDay {
       subdirectory: "Data")
 
     guard let dataURL,
-      let data = try? String(contentsOf: dataURL)
+      let data = try? String(contentsOf: dataURL, encoding: .utf8)
     else {
       fatalError("Couldn't find file '\(dataFilename).txt' in the 'Data' directory.")
     }
 
-    // On Windows, line separators may be CRLF. Converting to LF so that \n 
+    // On Windows, line separators may be CRLF. Converting to LF so that \n
     // works for string parsing.
     return data.replacingOccurrences(of: "\r", with: "")
   }

Sources/AdventOfCode.swift

@@ -13,6 +13,9 @@ struct AdventOfCode: AsyncParsableCommand {
   @Flag(help: "Benchmark the time taken by the solution")
   var benchmark: Bool = false
 
+  @Flag(help: "Run all the days available")
+  var all: Bool = false
+
   /// The selected day, or the latest day if no selection is provided.
   var selectedChallenge: any AdventDay {
     get throws {
@@ -33,36 +36,46 @@ struct AdventOfCode: AsyncParsableCommand {
     allChallenges.max(by: { $0.day < $1.day })!
   }
 
-  func run(part: () async throws -> Any, named: String) async -> Duration {
-    var result: Result<Any, Error> = .success("<unsolved>")
+  func run<T>(part: () async throws -> T, named: String) async -> Duration {
+    var result: Result<T, Error>?
     let timing = await ContinuousClock().measure {
       do {
         result = .success(try await part())
       } catch {
         result = .failure(error)
       }
     }
-    switch result {
+    switch result! {
     case .success(let success):
       print("\(named): \(success)")
+    case .failure(let failure as PartUnimplemented):
+      print("Day \(failure.day) part \(failure.part) unimplemented")
     case .failure(let failure):
       print("\(named): Failed with error: \(failure)")
     }
     return timing
   }
 
   func run() async throws {
-    let challenge = try selectedChallenge
-    print("Executing Advent of Code challenge \(challenge.day)...")
+    let challenges =
+      if all {
+        allChallenges
+      } else {
+        try [selectedChallenge]
+      }
 
-    let timing1 = await run(part: challenge.part1, named: "Part 1")
-    let timing2 = await run(part: challenge.part2, named: "Part 2")
+    for challenge in challenges {
+      print("Executing Advent of Code challenge \(challenge.day)...")
 
-    if benchmark {
-      print("Part 1 took \(timing1), part 2 took \(timing2).")
-      #if DEBUG
-        print("Looks like you're benchmarking debug code. Try swift run -c release")
-      #endif
+      let timing1 = await run(part: challenge.part1, named: "Part 1")
+      let timing2 = await run(part: challenge.part2, named: "Part 2")
+
+      if benchmark {
+        print("Part 1 took \(timing1), part 2 took \(timing2).")
+        #if DEBUG
+          print("Looks like you're benchmarking debug code. Try swift run -c release")
+        #endif
+      }
     }
   }
 }