| | | 1 | | namespace CalculatorLibrary { |
| | | 2 | | |
| | | 3 | | /// <summary> |
| | | 4 | | /// Parses and runs the calculator's command-line arguments. |
| | | 5 | | /// </summary> |
| | | 6 | | /// <remarks> |
| | | 7 | | /// <para> |
| | | 8 | | /// The parsing logic lives here, in the library, instead of in <c>CalculatorApp/Program.cs</c>, so |
| | | 9 | | /// it can be unit tested directly (see <c>CalculatorLibrary.Tests/CalculatorCliTests.cs</c>) without |
| | | 10 | | /// spawning the console application as a process. <c>Program.cs</c> only calls |
| | | 11 | | /// <see cref="Run(string[])"/> or <see cref="RunDemo"/> and prints the result — it never reads from |
| | | 12 | | /// the console, so it never blocks when the app is launched from a script, a build pipeline or CI. |
| | | 13 | | /// </para> |
| | | 14 | | /// <para> |
| | | 15 | | /// When you rename this sample into your own project, replace this class with your own |
| | | 16 | | /// argument-parsing entry point, keeping the same "parsing is a library function, not something the |
| | | 17 | | /// console shell does inline" shape. |
| | | 18 | | /// </para> |
| | | 19 | | /// </remarks> |
| | | 20 | | public static class CalculatorCli { |
| | | 21 | | /// <summary>The usage line shown when the arguments cannot be parsed.</summary> |
| | | 22 | | public const string UsageText = "Usage: CalculatorApp <add|subtract|multiply|divide> <a> <b>"; |
| | | 23 | | |
| | | 24 | | /// <summary> |
| | | 25 | | /// Parses <paramref name="args"/> as <c><operation> <a> <b></c> and returns a |
| | | 26 | | /// line of text describing the result. |
| | | 27 | | /// </summary> |
| | | 28 | | /// <param name="args"> |
| | | 29 | | /// Exactly three arguments: the operation name (<c>add</c>, <c>subtract</c>, <c>multiply</c> or |
| | | 30 | | /// <c>divide</c>, case-insensitive) followed by the two integer operands. |
| | | 31 | | /// </param> |
| | | 32 | | /// <returns>A human-readable line such as <c>"2 add 2 = 4"</c>.</returns> |
| | | 33 | | /// <exception cref="ArgumentException"> |
| | | 34 | | /// Thrown when the argument count is wrong, an operand is not a valid 32-bit integer, or the |
| | | 35 | | /// operation name is not recognized. The message always ends with <see cref="UsageText"/>. |
| | | 36 | | /// </exception> |
| | | 37 | | /// <exception cref="DivideByZeroException">Thrown when dividing by zero.</exception> |
| | | 38 | | public static string Run(string[] args) { |
| | 32 | 39 | | if (args.Length != 3) { |
| | 8 | 40 | | throw new ArgumentException($"Expected 3 arguments (operation, a, b) but got {args.Length}. {UsageText}"); |
| | | 41 | | } |
| | | 42 | | |
| | 24 | 43 | | string operation = args[0].Trim().ToLowerInvariant(); |
| | | 44 | | |
| | 24 | 45 | | if (!int.TryParse(args[1], out int a)) { |
| | 6 | 46 | | throw new ArgumentException($"'{args[1]}' is not a valid 32-bit integer for <a>. {UsageText}"); |
| | | 47 | | } |
| | | 48 | | |
| | 18 | 49 | | if (!int.TryParse(args[2], out int b)) { |
| | 2 | 50 | | throw new ArgumentException($"'{args[2]}' is not a valid 32-bit integer for <b>. {UsageText}"); |
| | | 51 | | } |
| | | 52 | | |
| | 16 | 53 | | var calculator = new Calculator(); |
| | | 54 | | |
| | 16 | 55 | | int result = operation switch { |
| | 4 | 56 | | "add" => calculator.Add(a, b), |
| | 2 | 57 | | "subtract" => calculator.Subtract(a, b), |
| | 2 | 58 | | "multiply" => calculator.Multiply(a, b), |
| | 4 | 59 | | "divide" => calculator.Divide(a, b), |
| | 4 | 60 | | _ => throw new ArgumentException($"Unknown operation '{args[0]}'. {UsageText}"), |
| | 16 | 61 | | }; |
| | | 62 | | |
| | 10 | 63 | | return $"{a} {operation} {b} = {result}"; |
| | | 64 | | } |
| | | 65 | | |
| | | 66 | | /// <summary> |
| | | 67 | | /// Runs a small built-in demonstration that exercises every operation once, used when the |
| | | 68 | | /// application is started with no arguments at all (so a first run always shows something, |
| | | 69 | | /// without waiting on keyboard input). |
| | | 70 | | /// </summary> |
| | | 71 | | /// <returns>The combined demo output, ending with <see cref="UsageText"/>.</returns> |
| | | 72 | | public static string RunDemo() { |
| | 2 | 73 | | var calculator = new Calculator(); |
| | 2 | 74 | | var lines = new System.Text.StringBuilder(); |
| | 2 | 75 | | lines.AppendLine("Calculator Application Running (no arguments given, showing the built-in demo)..."); |
| | 2 | 76 | | lines.AppendLine($"2 add 2 = {calculator.Add(2, 2)}"); |
| | 2 | 77 | | lines.AppendLine($"2 multiply 2 = {calculator.Multiply(2, 2)}"); |
| | 2 | 78 | | lines.AppendLine($"2 subtract 2 = {calculator.Subtract(2, 2)}"); |
| | 2 | 79 | | lines.AppendLine($"2 divide 2 = {calculator.Divide(2, 2)}"); |
| | 2 | 80 | | lines.Append(UsageText); |
| | 2 | 81 | | return lines.ToString(); |
| | | 82 | | } |
| | | 83 | | } |
| | | 84 | | } |