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

package com.infendro.cli.command

import com.infendro.cli.Dsl
import com.infendro.cli.argument.Argument
import com.infendro.cli.command.context.Context
import com.infendro.cli.command.context.ContextParser
import com.infendro.cli.command.help.DefaultHelpRenderer
import com.infendro.cli.command.help.HelpRenderer
import com.infendro.cli.option.Option
import com.infendro.cli.error.build.*
import com.infendro.cli.parser.Parser
import com.infendro.cli.util.Regex

sealed class Command private constructor(
    val name: String,
    val description: String?,
    val commands: List<Command>,
    val arguments: List<Argument<*>>,
    val options: List<Option<*>>,
    internal val execute: Context.() -> Unit,
    internal val renderer: HelpRenderer,
) {
    init {
        if (!name.matches(Regex.COMMAND)) throw InvalidCommandName(name)
    }

    fun run(vararg args: String) {
        when (val result = ContextParser(this, arrayOf(*args)).parse()) {
            is ContextParser.Result.Success -> result.context.execute()
            is ContextParser.Result.Help -> {
                val command = result.path.last()
                val help = command.renderer.render(result.path)
                if (help != null) print(help)
            }
            is ContextParser.Result.Failure -> {
                println("error: ${result.failure.message}")
                val command = result.path.last()
                val help = command.renderer.render(result.path)
                if (help != null) print("\n$help")
            }
        }
    }

    class Named(
        name: String,
        description: String?,
        commands: List<Command>,
        arguments: List<Argument<*>>,
        options: List<Option<*>>,
        execute: Context.() -> Unit,
        renderer: HelpRenderer,
    ) : Command(name, description, commands, arguments, options, execute, renderer) {
        class Builder(
            name: String,
            description: String?,
        ) : Command.Builder<Named>(name, description) {
            override fun create() =
                Named(name, description, commands, arguments, options, execute, renderer)
        }
    }

    class Fallback<T : Any>(
        val key: Key<T>,
        val parser: Parser<T>,
        name: String,
        description: String?,
        commands: List<Command>,
        arguments: List<Argument<*>>,
        options: List<Option<*>>,
        execute: Context.() -> Unit,
        renderer: HelpRenderer,
    ) : Command(name, description, commands, arguments, options, execute, renderer) {
        class Builder<T : Any>(
            val parser: Parser<T>,
            name: String,
            description: String?,
        ) : Command.Builder<Fallback<T>>(name, description) {
            internal val key = Key<T>()

            override fun create() =
                Fallback(key, parser, name, description, commands, arguments, options, execute, renderer)
        }

        class Key<T>
    }

    @Dsl
    sealed class Builder<COMMAND : Command>(
        protected val name: String,
        protected val description: String?,
    ) {
        protected val commands = mutableListOf<Command>()
        protected val arguments = mutableListOf<Argument<*>>()
        protected val options = mutableListOf<Option<*>>()
        private var _execute: (Context.() -> Unit)? = null
        private var _renderer: HelpRenderer? = null

        protected val execute: Context.() -> Unit
            get() = _execute!!
        protected val renderer: HelpRenderer
            get() = _renderer!!

        fun register(command: Command) {
            validateCommand(command)
            commands += command
        }

        fun register(vararg commands: Command) = commands.forEach(::register)
        operator fun <T : Command> T.unaryPlus() = also(::register)

        fun register(argument: Argument<*>) {
            validateArgument(argument)
            arguments += argument
        }

        fun register(vararg arguments: Argument<*>) = arguments.forEach(::register)
        operator fun <T : Argument<*>> T.unaryPlus() = also(::register)

        fun register(option: Option<*>) {
            validateOption(option)
            options += option
        }

        fun register(vararg options: Option<*>) = options.forEach(::register)
        operator fun <T : Option<*>> T.unaryPlus() = also(::register)

        fun execute(block: Context.() -> Unit) {
            validateExecute()
            _execute = block
        }

        fun renderer(renderer: HelpRenderer) {
            validateRenderer()
            _renderer = renderer
        }

        internal abstract fun create(): COMMAND

        internal fun build(): Command {
            if (_execute == null) _execute = {}
            if (_renderer == null) _renderer = DefaultHelpRenderer

            validate()
            return create()
        }

        private fun validateCommand(command: Command) {
            if (commands.isNotEmpty()) {
                val last = commands.last()
                if (last is Fallback<*>) throw InvalidCommandOrder()
            }
            if (commands.any { it.name == command.name }) throw DuplicateCommand(command)
        }

        private fun validateArgument(argument: Argument<*>) {
            if (arguments.isNotEmpty()) {
                val last = arguments.last()
                when {
                    last.unbounded -> throw InvalidArgumentOrder()
                    argument.required && last.optional -> throw InvalidArgumentOrder()
                }
            }
            if (arguments.any { it.name == argument.name }) throw DuplicateArgument(argument)
        }

        private fun validateOption(option: Option<*>) {
            for (name in option.names) {
                if (options.any { name in it.names }) throw DuplicateOption(option)
            }
        }

        private fun validateExecute() {
            if (_execute != null) throw DuplicateExecute()
        }

        private fun validateRenderer() {
            if (_renderer != null) throw DuplicateRenderer()
        }

        private fun validate() {
            if (commands.any { it is Fallback<*> } && arguments.isNotEmpty()) throw InvalidFallback()
        }
    }
}