client/client.go

package client

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

	hbserver "bitbucket.org/hackerbots/server"
	"code.google.com/p/go.net/websocket"
)

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

// Client keeps track of connection to server and has two interesting methods:
// Negociate 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
	Port      int
	Server    string
	StatsReq  hbserver.StatsRequest
	Verbose   bool
	Player    Player
	Game      hbserver.GameParam

	boardstate hbserver.Boardstate
	enc        encoder
	dec        decoder
	ws         *websocket.Conn
}

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

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

// Negociate runs through the hackerbots negociation protocol.
func (c *Client) Negociate() (err error) {
	if c.Verbose {
		log.Printf("%s: trying to connect to game '%s'", c.Name, c.GameId)
	}
	c.ws, err = connect(c.Server, c.Port)
	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))
	}
	if c.Verbose {
		log.Printf("%s: idreq: %+v", c.Name, 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:      "robot",
	})
	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.Verbose {
		log.Printf("%s: game parameters: %+v", c.Name, c.Game)
	}

	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)
	}

	conf := hbserver.ClientConfig{
		ID: c.GameId,
		Stats: map[string]hbserver.StatsRequest{
			c.Name: c.StatsReq,
		},
	}

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

	var handshake struct {
		Id      string `json:"id"`
		Success bool   `json:"success"`
		Type    string `json:"type"`
		hbserver.Failure
	}
	websocket.JSON.Receive(c.ws, &handshake)
	if !handshake.Success {
		return errors.New(handshake.Reason)
	}
	if c.Verbose {
		log.Printf("%s: handshake: %+v", c.Name, handshake)
	}

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

	return nil
}

// Play contains the main game run loop. It gets a hbserver.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 {
	log.Printf("%s: starting loop", c.Name)

	var err error
	for {
		err = c.dec.Decode(&c.boardstate)
		if err != nil {
			return errors.New(fmt.Sprintf("%s: Connection likely lost: %s", c.Name, err))
		}
		c.Player.Recv(&c.boardstate)

		instruction := c.Player.Instruction()
		err = c.enc.Encode(instruction)
		if err != nil {
			return err
		}
	}
	return nil
}