improve argument/option declaration

src/commonMain/kotlin/com/infendro/cli/command/Argument.kt

@@ -41,28 +41,17 @@ sealed class Argument<T : Any>(
     }
 
     companion object {
-        fun string() =
-            Required(StringParser)
+        fun string() = argument(StringParser)
+        fun int() = argument(IntParser)
+        fun long() = argument(LongParser)
+        fun float() = argument(FloatParser)
+        fun double() = argument(DoubleParser)
+        fun boolean() = argument(BooleanParser)
 
-        fun int() =
-            Required(IntParser)
-
-        fun long() =
-            Required(LongParser)
-
-        fun float() =
-            Required(FloatParser)
-
-        fun double() =
-            Required(DoubleParser)
-
-        fun boolean() =
-            Required(BooleanParser)
-
-        inline fun <reified T : Enum<T>> enum() =
-            Required(enumParser<T>())
-
-        fun regex() =
-            Required(RegexParser)
+        inline fun <reified T : Enum<T>> enum() = argument(enumParser<T>())
+        fun regex() = argument(RegexParser)
     }
 }
+
+fun <T : Any> argument(parser: Parser<T>) =
+    Argument.Required(parser)

src/commonMain/kotlin/com/infendro/cli/command/Command.kt

@@ -1,11 +1,13 @@
 package com.infendro.cli.command
 
+import com.infendro.cli.Dsl
 import com.infendro.cli.command.context.Context
 import com.infendro.cli.command.context.Parser
 import com.infendro.cli.exception.build.*
 import com.infendro.cli.exception.run.CliException
 import com.infendro.cli.util.Regex.COMMAND
 import com.infendro.cli.util.Regex.OPTION
+import kotlin.reflect.KProperty
 
 class Command private constructor(
     val name: String?,
@@ -23,6 +25,7 @@ class Command private constructor(
         println(e.message)
     }
 
+    @Dsl
     class Builder internal constructor(
         private val level: Int,
         private val name: String?,
@@ -68,10 +71,10 @@ class Command private constructor(
             arguments += argument
         }
 
-        fun <T : Argument<*>> T.register() = also(::argument)
-
         fun arguments(vararg arguments: Argument<*>) = arguments.forEach(::argument)
-        fun <T : Argument<*>> Array<T>.register() = also(::arguments)
+
+        operator fun <T : Argument<*>> T.provideDelegate(thisRef: Nothing?, property: KProperty<*>) = also(::argument)
+        operator fun <T : Argument<*>> T.getValue(thisRef: Nothing?, property: KProperty<*>) = this
 
         fun option(option: Option<*>) {
             // validate
@@ -85,10 +88,10 @@ class Command private constructor(
             options += option
         }
 
-        fun <T : Option<*>> T.register() = also(::option)
-
         fun options(vararg options: Option<*>) = options.forEach(::option)
-        fun <T : Option<*>> Array<T>.register() = also(::options)
+
+        operator fun <T : Option<*>> T.provideDelegate(thisRef: Nothing?, property: KProperty<*>) = also(::option)
+        operator fun <T : Option<*>> T.getValue(thisRef: Nothing?, property: KProperty<*>) = this
 
         fun execute(block: Context.() -> Unit) {
             if (::_execute.isInitialized)

src/commonMain/kotlin/com/infendro/cli/command/Option.kt

@@ -84,28 +84,20 @@ sealed class Option<T : Any>(
     }
 
     companion object {
-        fun string(vararg names: String) =
-            Required(StringParser, names.asList())
+        fun string(vararg names: String) = option(StringParser, *names)
+        fun int(vararg names: String) = option(IntParser, *names)
+        fun long(vararg names: String) = option(LongParser, *names)
+        fun float(vararg names: String) = option(FloatParser, *names)
+        fun double(vararg names: String) = option(DoubleParser, *names)
+        fun boolean(vararg names: String) = option(BooleanParser, true, *names)
 
-        fun int(vararg names: String) =
-            Required(IntParser, names.asList())
-
-        fun long(vararg names: String) =
-            Required(LongParser, names.asList())
-
-        fun float(vararg names: String) =
-            Required(FloatParser, names.asList())
-
-        fun double(vararg names: String) =
-            Required(DoubleParser, names.asList())
-
-        fun boolean(vararg names: String) =
-            Required(BooleanParser, true, names.asList())
-
-        inline fun <reified T : Enum<T>> enum(vararg names: String) =
-            Required(enumParser<T>(), names.asList())
-
-        fun regex(vararg names: String) =
-            Required(RegexParser, names.asList())
+        inline fun <reified T : Enum<T>> enum(vararg names: String) = option(enumParser<T>(), *names)
+        fun regex(vararg names: String) = option(RegexParser, *names)
     }
 }
+
+fun <T : Any> option(parser: Parser<T>, vararg names: String) =
+    Option.Required(parser, names.asList())
+
+fun <T : Any> option(parser: Parser<T>, fallback: T, vararg names: String) =
+    Option.Required(parser, fallback, names.asList())

src/commonMain/kotlin/com/infendro/cli/command/context/Context.kt

@@ -1,10 +1,12 @@
 package com.infendro.cli.command.context
 
+import com.infendro.cli.Dsl
 import com.infendro.cli.command.Argument
 import com.infendro.cli.command.Command
 import com.infendro.cli.command.Option
 import kotlin.reflect.KProperty
 
+@Dsl
 class Context internal constructor(
     val command: Command,
     val commands: List<Cmd>,