Simple & Elegant Command Line Interfaces in Swift

dependencies: [
.Package(url: "https://github.com/surfandneptune/CommandCougar.git", from: "1.0.0")
]

var helloCommand = Command(
    name: "hello",
    overview: "Say Hello",
    callback: { print($0.options, $0.parameters) },
    options: [
        Option(flag: .short("v"), overview: "Increase verbosity"),
        Option(flag: .short("w"), overview: "Wave hello")
    ],
    parameters:[.optional("Name")])

let arguments = ["hello", "-v", "Mr.Rogers"]
let helloEvaluation = helloCommand.evaluate(arguments: arguments)

let helloEvaluation = helloCommand.evaluate(arguments: CommandLine.arguments)

helloCommand.options        // ['-v', '-w']
helloEvaluation.options     // ['-v']
helloEvaluation.parameters  // ['Mr.Rogers']

try helloEvaluation.performCallbacks()

// will match -v
Option(flag: .short("v"), overview: "verbose")

// will match -v | --verbose
Option(flag: .both(short: "v", long: "verbose"), overview: "verbose")

// will match --path=/etc
Option(flag: .long("path"), overview: "File path", parameterName: "/etc")

/// Used for callback
func echo(evaluation: Command.Evaluation) throws {
  print(
    "\(evaluation.name) evaluated with " +
    "options: \(evaluation.options) " +
    "and parameters \(evaluation.parameters)"
    )
}

let swiftCommand =
Command(
    name: "swift",
    overview: "Swift Program",
    callback: echo,
    options: [],
    subCommands: [
        Command(
            name: "package",
            overview: "Perform operations on Swift packages",
            callback: echo,
            options: [
                Option(
                    flag: .both(short: "v", long: "verbose"),
                    overview: "Increase verbosity of informational output"),
                Option(
                    flag: .long("enable-prefetching"),
                    overview: "Increase verbosity of informational output")
            ],
            subCommands: [
                Command(
                    name: "update",
                    overview: "Update package dependencies",
                    callback: echo,
                    options: [
                        Option(
                            flag: .long("repin"),
                            overview: "Update without applying pins and repin the updated versions.")
                    ],
                    subCommands: [])
            ])
    ])

do {
    // normally CommandLine.arguments
    let args = ["swift", "package", "-v", "update", "--repin"]
    let evaluation: Command.Evaluation = try swiftCommand.evaluate(arguments: args)
    try evaluation.performCallbacks()
} catch {
    print(error)
}

// Output
// swift evaluated with  options: []  and parameters []
// package evaluated with  options: [-v]  and parameters []
// update evaluated with  options: [--repin]  and parameters []

evaluation["package"]?.name  // results in "package"

evaluation["package"]?.options["v"] // results in Option.Evaluation

evaluation["package"]?.options["v"]?.flag.shortName // results in "v"

evaluation["package"]?.options["enable-prefetching"] // results in nil

evaluation["package"]?["update"]?.options["repin"]?.flag.longName // results in "repin"

func callback(evaluation: CommandEvaluation) throws {
    guard let first = evaluation.parameters.first else {
    throw CommandCougar.Errors.parameterAccessError("Parameter not found.")
	}
}

func callback(evaluation: CommandEvaluation) throws {
    let first = try evaluation.parameter(at: 0)
}