package commands

import (
	"fmt"
	"reflect"
	"strings"
)

type Command struct {
	Help        string
	Options     []Option
	f           func(*Request, *Response)
	subcommands map[string]*Command
}

// Register adds a subcommand
func (c *Command) Register(id string, sub *Command) error {
	if c.subcommands == nil {
		c.subcommands = make(map[string]*Command)
	}

	// check for duplicate option names (only checks downwards)
	names := make(map[string]bool)
	globalCommand.checkOptions(names)
	c.checkOptions(names)
	err := sub.checkOptions(names)
	if err != nil {
		return err
	}

	if _, ok := c.subcommands[id]; ok {
		return fmt.Errorf("There is already a subcommand registered with id '%s'", id)
	}

	c.subcommands[id] = sub
	return nil
}

// Call invokes the command at the given subcommand path
func (c *Command) Call(path []string, req *Request) *Response {
	options := make([]Option, len(c.Options))
	copy(options, c.Options)
	options = append(options, globalOptions...)
	cmd := c
	res := &Response{req: req}

	if path != nil {
		for i, id := range path {
			cmd = c.Sub(id)

			if cmd == nil {
				pathS := strings.Join(path[0:i], "/")
				res.SetError(fmt.Errorf("Undefined command: '%s'", pathS), Client)
				return res
			}

			options = append(options, cmd.Options...)
		}
	}

	optionsMap := make(map[string]Option)
	for _, opt := range options {
		for _, name := range opt.Names {
			optionsMap[name] = opt
		}
	}

	for k, v := range req.options {
		opt, ok := optionsMap[k]

		if !ok {
			res.SetError(fmt.Errorf("Unrecognized command option: '%s'", k), Client)
			return res
		}

		for _, name := range opt.Names {
			if _, ok = req.options[name]; name != k && ok {
				res.SetError(fmt.Errorf("Duplicate command options were provided ('%s' and '%s')",
					k, name), Client)
				return res
			}
		}

		kind := reflect.TypeOf(v).Kind()
		if kind != opt.Type {
			res.SetError(fmt.Errorf("Option '%s' should be type '%s', but got type '%s'",
				k, opt.Type.String(), kind.String()), Client)
			return res
		}
	}

	cmd.f(req, res)

	return res
}

// Sub returns the subcommand with the given id
func (c *Command) Sub(id string) *Command {
	return c.subcommands[id]
}

func (c *Command) checkOptions(names map[string]bool) error {
	for _, opt := range c.Options {
		for _, name := range opt.Names {
			if _, ok := names[name]; ok {
				return fmt.Errorf("Multiple options are using the same name ('%s')", name)
			}
			names[name] = true
		}
	}

	for _, cmd := range c.subcommands {
		err := cmd.checkOptions(names)
		if err != nil {
			return err
		}
	}

	return nil
}