client/client.go

package client

import (
	"encoding/gob"
	"encoding/json"
	"errors"
	"fmt"

	"golang.org/x/net/websocket"

	"hackerbots.us/server"
)

func connect(addr string) (*websocket.Conn, error) {
	origin := "http://localhost/"
	url := fmt.Sprintf("%s/ws/", addr)
	return websocket.Dial(url, "", origin)
}

// Client keeps track of connection to server and has two interesting methods:
// Negotiate and Play. Users of this struct will likely use most everything as
// is while defining their own Player to specify desired game play behavior.
type Client struct {
	ForceJSON bool
	GameId    string
	Name      string
	Server    string
	Game      server.GameParam

	boardstate *server.Boardstate
	enc        encoder
	dec        decoder
	ws         *websocket.Conn

	// visualization members
	width, height float64
	viewX, viewY  int
	StateStream   chan *server.Boardstate
	Die           chan struct{}

	Player
}

type encoder interface {
	Encode(v interface{}) error
}

type decoder interface {
	Decode(v interface{}) error
}

// Negotiate runs through the hackerbots negociation protocol.
func (c *Client) Negotiate(clientType string, player Player) (err error) {
	c.ws, err = connect(c.Server)
	if err != nil {
		return errors.New(fmt.Sprintf("connection failure: %s", err))
	}

	err = websocket.JSON.Send(c.ws, struct {
		Id string `json:"id"`
	}{
		c.GameId,
	})
	if err != nil {
		return err
	}

	var idreq struct {
		Type     string `json:"type"`
		PlayerId string `json:"id"`
	}
	err = websocket.JSON.Receive(c.ws, &idreq)
	if err != nil || idreq.Type == "failure" {
		return errors.New(fmt.Sprintf("failure: %+v", idreq))
	}

	err = websocket.JSON.Send(c.ws, struct {
		Type      string `json:"type"`
		Name      string `json:"name"`
		Useragent string `json:"useragent"`
	}{
		Name:      c.Name,
		Useragent: "gobot",
		Type:      clientType,
	})
	if err != nil {
		return err
	}

	supportedEncs := []string{"bson", "json", "gob"}
	if c.ForceJSON {
		supportedEncs = []string{"json"}
	}
	err = websocket.JSON.Send(c.ws, supportedEncs)
	if err != nil {
		return errors.New(fmt.Sprintf("failure: %+v", err))
	}

	err = websocket.JSON.Receive(c.ws, &c.Game)
	if c.Game.Type != "gameparam" {
		return errors.New("didn't receive a good gameparam")
	}

	if c.Game.Encoding == "json" {
		c.enc = json.NewEncoder(c.ws)
		c.dec = json.NewDecoder(c.ws)
	} else {
		c.enc = gob.NewEncoder(c.ws)
		c.dec = gob.NewDecoder(c.ws)
	}

	switch clientType {
	case "robot":
		conf := server.ClientConfig{
			ID:    c.GameId,
			Stats: player.GetStats(),
		}

		err = websocket.JSON.Send(c.ws, conf)

		var handshake struct {
			Id      string `json:"id"`
			Success bool   `json:"success"`
			Type    string `json:"type"`
			server.Failure
		}
		websocket.JSON.Receive(c.ws, &handshake)
		if !handshake.Success {
			return errors.New(handshake.Reason)
		}

		// we don't do anything useful with dstats, but could be interesting to
		// pass along to the player?
		dstats := struct {
			Stats map[string]server.Stats `json:"stats"`
			Type  string                  `json:"type"`
		}{}
		err = websocket.JSON.Receive(c.ws, &dstats)
		if err != nil {
			return err
		}
	case "spectator":
	}

	c.width = c.Game.BoardSize.Width
	c.height = c.Game.BoardSize.Height

	return nil
}

// Play contains the main game run loop. It gets a server.Boardstate from the
// server, and passes this along to the embedded Player. Following this it
// sends the server the Player's instruction.
func (c *Client) Play() error {
	bs := &server.Boardstate{}
	var err error
	for {
		err = c.dec.Decode(bs)
		if err != nil {
			return errors.New(fmt.Sprintf("%s: Connection likely lost: %s", c.Name, err))
		}

		select {
		case c.StateStream <- bs:
		default:
		}

		err = c.enc.Encode(c.Update(bs))
		if err != nil {
			return err
		}
	}
}