package chat

import (
	"errors"
	"io"
	"math/rand"
	"sync"
	"time"
)

const messageBuffer = 20

var ErrUserClosed = errors.New("user closed")

// Id is a unique immutable identifier for a user.
type Id string

// Identifier is an interface that can uniquely identify itself.
type Identifier interface {
	Id() Id
	SetId(Id)
	Name() string
}

// User definition, implemented set Item interface and io.Writer
type User struct {
	Identifier
	Config    UserConfig
	colorIdx  int
	joined    time.Time
	msg       chan Message
	done      chan struct{}
	replyTo   *User // Set when user gets a /msg, for replying.
	closed    bool
	closeOnce sync.Once
}

func NewUser(identity Identifier) *User {
	u := User{
		Identifier: identity,
		Config:     *DefaultUserConfig,
		joined:     time.Now(),
		msg:        make(chan Message, messageBuffer),
		done:       make(chan struct{}, 1),
	}
	u.SetColorIdx(rand.Int())

	return &u
}

func NewUserScreen(identity Identifier, screen io.Writer) *User {
	u := NewUser(identity)
	go u.Consume(screen)

	return u
}

// Rename the user with a new Identifier.
func (u *User) SetId(id Id) {
	u.Identifier.SetId(id)
	u.SetColorIdx(rand.Int())
}

// ToggleQuietMode will toggle whether or not quiet mode is enabled
func (u *User) ToggleQuietMode() {
	u.Config.Quiet = !u.Config.Quiet
}

// SetColorIdx will set the colorIdx to a specific value, primarily used for
// testing.
func (u *User) SetColorIdx(idx int) {
	u.colorIdx = idx
}

// Block until user is closed
func (u *User) Wait() {
	<-u.done
}

// Disconnect user, stop accepting messages
func (u *User) Close() {
	u.closeOnce.Do(func() {
		u.closed = true
		close(u.done)
		close(u.msg)
	})
}

// Consume message buffer into an io.Writer. Will block, should be called in a
// goroutine.
// TODO: Not sure if this is a great API.
func (u *User) Consume(out io.Writer) {
	for m := range u.msg {
		u.HandleMsg(m, out)
	}
}

// Consume one message and stop, mostly for testing
func (u *User) ConsumeOne(out io.Writer) {
	u.HandleMsg(<-u.msg, out)
}

func (u *User) HandleMsg(m Message, out io.Writer) {
	s := m.Render(u.Config.Theme)
	_, err := out.Write([]byte(s + Newline))
	if err != nil {
		logger.Printf("Write failed to %s, closing: %s", u.Name(), err)
		u.Close()
	}
}

// Add message to consume by user
func (u *User) Send(m Message) error {
	if u.closed {
		return ErrUserClosed
	}

	select {
	case u.msg <- m:
	default:
		logger.Printf("Msg buffer full, closing: %s", u.Name())
		u.Close()
		return ErrUserClosed
	}
	return nil
}

// Container for per-user configurations.
type UserConfig struct {
	Highlight bool
	Bell      bool
	Quiet     bool
	Theme     *Theme
}

// Default user configuration to use
var DefaultUserConfig *UserConfig

func init() {
	DefaultUserConfig = &UserConfig{
		Highlight: true,
		Bell:      false,
		Quiet:     false,
	}

	// TODO: Seed random?
}