module cli

type FnCommandCallback fn (cmd Command)?

pub fn (f FnCommandCallback) str() string {
	return 'FnCommandCallback=>' + ptr_str(f)
}

pub struct Command {
pub mut:
	name            string
	usage           string
	description     string
	version         string
	pre_execute     FnCommandCallback
	execute         FnCommandCallback
	post_execute    FnCommandCallback
	disable_help    bool
	disable_version bool
	disable_flags   bool
	sort_flags      bool = true
	sort_commands   bool = true
	parent          &Command = 0
	commands        []Command
	flags           []Flag
	args            []string
}

pub fn (cmd Command) str() string {
	mut res := []string{}
	res << 'Command{'
	res << '	name: "$cmd.name"'
	res << '	usage: "$cmd.usage"'
	res << '	version: "$cmd.version"'
	res << '	description: "$cmd.description"'
	res << '	disable_help: $cmd.disable_help'
	res << '	disable_flags: $cmd.disable_flags'
	res << '	disable_version: $cmd.disable_version'
	res << '	sort_flags: $cmd.sort_flags'
	res << '	sort_commands: $cmd.sort_commands'
	res << '	cb execute: $cmd.execute'
	res << '	cb pre_execute: $cmd.pre_execute'
	res << '	cb post_execute: $cmd.post_execute'
	if cmd.parent == 0 {
		res << '	parent: &Command(0)'
	} else {
		res << '	parent: &Command{$cmd.parent.name ...}'
	}
	res << '	commands: $cmd.commands'
	res << '	flags: $cmd.flags'
	res << '	args: $cmd.args'
	res << '}'
	return res.join('\n')
}

pub fn (cmd Command) is_root() bool {
	return isnil(cmd.parent)
}

pub fn (cmd Command) root() Command {
	if cmd.is_root() {
		return cmd
	}
	return cmd.parent.root()
}

pub fn (cmd Command) full_name() string {
	if cmd.is_root() {
		return cmd.name
	}
	return cmd.parent.full_name() + ' $cmd.name'
}

pub fn (mut cmd Command) add_commands(commands []Command) {
	for command in commands {
		cmd.add_command(command)
	}
}

pub fn (mut cmd Command) add_command(command Command) {
	for existing_cmd in cmd.commands {
		if existing_cmd.name == command.name {
			println("command with the same name \'$command.name\' already exists")
			exit(1)
		}
	}
	cmd.commands << command
}

pub fn (mut cmd Command) add_flags(flags []Flag) {
	for flag in flags {
		cmd.add_flag(flag)
	}
}

pub fn (mut cmd Command) add_flag(flag Flag) {
	for existing_flag in cmd.flags {
		if existing_flag.name == flag.name {
			println("flag with the same name \'$flag.name\' already exists")
			exit(1)
		}
	}
	cmd.flags << flag
}

pub fn (mut cmd Command) parse(args []string) {
	if !cmd.disable_flags {
		cmd.add_default_flags()
	}
	cmd.add_default_commands()
	if cmd.sort_flags {
		cmd.flags.sort(a.name < b.name)
	}
	if cmd.sort_commands {
		cmd.commands.sort(a.name < b.name)
	}
	cmd.args = args[1..]
	for i in 0 .. cmd.commands.len {
		cmd.commands[i].parent = cmd
	}
	if !cmd.disable_flags {
		cmd.parse_flags()
	}
	cmd.parse_commands()
}

fn (mut cmd Command) add_default_flags() {
	if !cmd.disable_help && !cmd.flags.contains('help') {
		cmd.add_flag(help_flag(!cmd.flags.contains('h') && cmd.has_abbrev_flags()))
	}
	if cmd.version != '' && !cmd.flags.contains('version') {
		cmd.add_flag(version_flag(!cmd.flags.contains('v') && cmd.has_abbrev_flags()))
	}
}

fn (mut cmd Command) add_default_commands() {
	if !cmd.disable_help && !cmd.commands.contains('help') && cmd.is_root() {
		cmd.add_command(help_cmd())
	}
	if cmd.version != '' && !cmd.commands.contains('version') {
		cmd.add_command(version_cmd())
	}
}

fn (mut cmd Command) parse_flags() {
	for {
		if cmd.args.len < 1 || !cmd.args[0].starts_with('-') {
			break
		}
		mut found := false
		for i in 0 .. cmd.flags.len {
			mut flag := &cmd.flags[i]
			if flag.matches(cmd.args, cmd.has_abbrev_flags()) {
				found = true
				flag.found = true
				cmd.args = flag.parse(cmd.args, cmd.has_abbrev_flags()) or {
					println('failed to parse flag ${cmd.args[0]}: $err')
					exit(1)
				}
				break
			}
		}
		if !found {
			println('invalid flag: ${cmd.args[0]}')
			exit(1)
		}
	}
}

fn (mut cmd Command) parse_commands() {
	global_flags := cmd.flags.filter(it.global)
	cmd.check_help_flag()
	cmd.check_version_flag()
	for i in 0 .. cmd.args.len {
		arg := cmd.args[i]
		for j in 0 .. cmd.commands.len {
			mut command := cmd.commands[j]
			if command.name == arg {
				for flag in global_flags {
					command.add_flag(flag)
				}
				command.parse(cmd.args[i..])
				return
			}
		}
	}
	// if no further command was found, execute current command
	if int(cmd.execute) == 0 {
		if !cmd.disable_help {
			cmd.execute_help()
		}
	} else {
		cmd.check_required_flags()
		if int(cmd.pre_execute) > 0 {
			cmd.pre_execute(*cmd) or {
				println('cli preexecution error: $err')
				exit(1)
			}
		}
		cmd.execute(*cmd) or {
			println('cli execution error: $err')
			exit(1)
		}
		if int(cmd.post_execute) > 0 {
			cmd.post_execute(*cmd) or {
				println('cli postexecution error: $err')
				exit(1)
			}
		}
	}
}

fn (cmd Command) has_abbrev_flags() bool {
	mut has_abbrev := false
	for flag in cmd.flags {
		if flag.abbrev != '' {
			has_abbrev = true
		}
	}
	return has_abbrev
}

fn (cmd Command) check_help_flag() {
	if !cmd.disable_help && cmd.flags.contains('help') {
		help_flag := cmd.flags.get_bool('help') or {
			return
		} // ignore error and handle command normally
		if help_flag {
			cmd.execute_help()
			exit(0)
		}
	}
}

fn (cmd Command) check_version_flag() {
	if cmd.version != '' && cmd.flags.contains('version') {
		version_flag := cmd.flags.get_bool('version') or {
			return
		} // ignore error and handle command normally
		if version_flag {
			version_cmd := cmd.commands.get('version') or {
				return
			} // ignore error and handle command normally
			version_cmd.execute(version_cmd)
			exit(0)
		}
	}
}

fn (cmd Command) check_required_flags() {
	for flag in cmd.flags {
		if flag.required && flag.value == '' {
			full_name := cmd.full_name()
			println("flag \'$flag.name\' is required by \'$full_name\'")
			exit(1)
		}
	}
}

fn (cmd Command) execute_help() {
	if cmd.commands.contains('help') {
		help_cmd := cmd.commands.get('help') or {
			return
		} // ignore error and handle command normally
		help_cmd.execute(help_cmd)
	} else {
		print(cmd.help_message())
	}
}

fn (cmds []Command) get(name string) ?Command {
	for cmd in cmds {
		if cmd.name == name {
			return cmd
		}
	}
	return error("command \'$name\' not found.")
}

fn (cmds []Command) contains(name string) bool {
	for cmd in cmds {
		if cmd.name == name {
			return true
		}
	}
	return false
}