package commands

import (
	"errors"
	"fmt"
	"strings"

	u "github.com/jbenet/go-ipfs/util"
)

var log = u.Logger("command")

// Function is the type of function that Commands use.
// It reads from the Request, and writes results to the Response.
type Function func(Response, Request)

// Formatter is a function that takes in a Response, and returns a human-readable string
// (or an error on failure)
// MAYBE_TODO: maybe this should be a io.Reader instead of a string?
type Formatter func(Response) (string, error)

// Command is a runnable command, with input arguments and options (flags).
// It can also have Subcommands, to group units of work into sets.
type Command struct {
	Help        string
	Options     []Option
	Run         Function
	Format      Formatter
	Type        interface{}
	Subcommands map[string]*Command
	Private     bool
}

// ErrNotCallable signals a command that cannot be called.
var ErrNotCallable = errors.New("This command can't be called directly. Try one of its subcommands.")

var ErrNoFormatter = errors.New("This command cannot be formatted to plain text")

// Call invokes the command for the given Request
func (c *Command) Call(req Request) Response {
	res := NewResponse(req)

	cmds, err := c.Resolve(req.Path())
	if err != nil {
		res.SetError(err, ErrClient)
		return res
	}
	cmd := cmds[len(cmds)-1]

	if cmd.Run == nil {
		res.SetError(ErrNotCallable, ErrClient)
		return res
	}

	options, err := c.GetOptions(req.Path())
	if err != nil {
		res.SetError(err, ErrClient)
		return res
	}

	err = req.ConvertOptions(options)
	if err != nil {
		res.SetError(err, ErrClient)
		return res
	}

	cmd.Run(res, req)

	return res
}

// Resolve gets the subcommands at the given path
func (c *Command) Resolve(path []string) ([]*Command, error) {
	cmds := make([]*Command, len(path)+1)
	cmds[0] = c

	cmd := c
	for i, name := range path {
		cmd = cmd.Subcommand(name)

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

		cmds[i+1] = cmd
	}

	return cmds, nil
}

// Get resolves and returns the Command addressed by path
func (c *Command) Get(path []string) (*Command, error) {
	cmds, err := c.Resolve(path)
	if err != nil {
		return nil, err
	}
	return cmds[len(cmds)-1], nil
}

// GetOptions gets the options in the given path of commands
func (c *Command) GetOptions(path []string) (map[string]Option, error) {
	options := make([]Option, len(c.Options))

	cmds, err := c.Resolve(path)
	if err != nil {
		return nil, err
	}
	cmds = append(cmds, globalCommand)

	for _, cmd := range cmds {
		options = append(options, cmd.Options...)
	}

	optionsMap := make(map[string]Option)
	for _, opt := range options {
		for _, name := range opt.Names {
			if _, found := optionsMap[name]; found {
				return nil, fmt.Errorf("Option name '%s' used multiple times", name)
			}

			optionsMap[name] = opt
		}
	}

	return optionsMap, nil
}

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