box-o-sand/conway/web.go

package conway

import (
	"bytes"
	"compress/gzip"
	"encoding/base64"
	"encoding/json"
	"errors"
	"fmt"
	"image/png"
	"io/ioutil"
	"log"
	"math/rand"
	"net/http"
	"net/url"
	"strconv"
	"time"
)

type WebGameParams struct {
	Height int
	Width  int
	Xmul   int
	Ymul   int
}

type WebGameState struct {
	State *GameState `json:"s"`
	Img   string     `json:"i"`
}

type webAssetStrings struct {
	IndexHTML    []byte
	NormalizeCSS []byte
	JqueryMinJS  []byte
}

var WebAssets webAssetStrings

func init() {
	rand.Seed(time.Now().UTC().UnixNano())
	idxHt, err := fromGzB64(gameOfLifeIndexHtml)
	if err != nil {
		log.Fatal("Failed to decode internal index.html: ", err)
	}

	WebAssets.IndexHTML = idxHt

	normCss, err := fromGzB64(normalizeCss)
	if err != nil {
		log.Fatal("Failed to decode internal normalize.css: ", err)
	}
	WebAssets.NormalizeCSS = normCss

	jqmin, err := fromGzB64(jqueryMinJs)
	if err != nil {
		log.Fatal("Failed to decode internal jquery.min.js: ", err)
	}
	WebAssets.JqueryMinJS = jqmin
}

func fromGzB64(input string) ([]byte, error) {
	decoded, err := base64.StdEncoding.DecodeString(input)
	if err != nil {
		return []byte(""), err
	}

	buf := bytes.NewBuffer(decoded)
	zReader, err := gzip.NewReader(buf)
	if err != nil {
		return []byte(""), err
	}

	defer zReader.Close()

	gunzipped, err := ioutil.ReadAll(zReader)
	if err != nil {
		return []byte(""), err
	}

	return gunzipped, nil
}

func NewWebGameParams(q url.Values) *WebGameParams {
	params := &WebGameParams{
		Height: 50,
		Width:  50,
		Xmul:   10,
		Ymul:   10,
	}

	h := q.Get("h")
	if len(h) > 0 {
		if i, err := strconv.Atoi(h); err == nil {
			params.Height = i
		}
	}

	w := q.Get("w")
	if len(w) > 0 {
		if i, err := strconv.Atoi(w); err == nil {
			params.Width = i
		}
	}

	xm := q.Get("xm")
	if len(xm) > 0 {
		if i, err := strconv.Atoi(xm); err == nil {
			params.Xmul = i
		}
	}

	ym := q.Get("ym")
	if len(ym) > 0 {
		if i, err := strconv.Atoi(ym); err == nil {
			params.Ymul = i
		}
	}

	return params
}

func handle405(method, uri string, w http.ResponseWriter) {
	w.Header().Set("Content-Type", "text/plain")
	w.WriteHeader(http.StatusMethodNotAllowed)
	w.Write([]byte(fmt.Sprintf("Nope.  %v not allowed at %v\n", method, uri)))
}

func handle500(err error, w http.ResponseWriter) {
	log.Println("ERROR:", err)
	w.Header().Set("Content-Type", "text/plain")
	w.WriteHeader(http.StatusInternalServerError)
	w.Write([]byte(fmt.Sprintf("We exploded!: %v\n", err)))
}

func HandleWebGameRoot(w http.ResponseWriter, req *http.Request) {
	if req.Method != "GET" {
		handle405(req.Method, req.RequestURI, w)
		return
	}

	w.Header().Set("Content-Type", "text/html")
	w.WriteHeader(http.StatusOK)
	w.Write(WebAssets.IndexHTML)
	return
}

func HandleWebGameStatic(w http.ResponseWriter, req *http.Request) {
	if req.Method != "GET" {
		handle405(req.Method, req.RequestURI, w)
		return
	}

	if req.URL.Path == "/static/normalize.css" {
		w.Header().Set("Content-Type", "text/css")
		w.WriteHeader(http.StatusOK)
		w.Write(WebAssets.NormalizeCSS)
		return
	}

	if req.URL.Path == "/static/jquery.min.js" {
		w.Header().Set("Content-Type", "text/javascript")
		w.WriteHeader(http.StatusOK)
		w.Write(WebAssets.JqueryMinJS)
		return
	}

	w.Header().Set("Content-Type", "text/plain")
	w.WriteHeader(http.StatusNotFound)
	w.Write([]byte(fmt.Sprintf("Don't have: %v\n", req.URL.Path)))
}

func HandleWebGameState(w http.ResponseWriter, req *http.Request) {
	switch req.Method {
	case "GET":
		handleWebGameStateGET(w, req)
		return
	case "POST":
		handleWebGameStatePOST(w, req)
		return
	default:
		handle405(req.Method, req.RequestURI, w)
		return
	}
}

func handleWebGameStateGET(w http.ResponseWriter, req *http.Request) {
	q := req.URL.Query()
	params := NewWebGameParams(q)

	game := NewGameOfLife(params.Height, params.Width)
	err := game.ImportRandomState()
	if err != nil {
		handle500(err, w)
		return
	}

	sendWebGameStateJSONPayload(w, http.StatusOK, game, params)
}

func handleWebGameStatePOST(w http.ResponseWriter, req *http.Request) {
	q := req.URL.Query()
	params := NewWebGameParams(q)

	defer func() {
		r := recover()
		if r != nil {
			handle500(errors.New(fmt.Sprintf("OH NOES! %v", r)), w)
		}
	}()

	body, err := ioutil.ReadAll(req.Body)
	if err != nil {
		handle500(err, w)
	}

	webGameState := &WebGameState{}
	err = json.Unmarshal(body, webGameState)
	if err != nil {
		handle500(err, w)
	}

	height, width := webGameState.State.Height(), webGameState.State.Width()
	game := NewGameOfLife(height, width)
	game.ImportState(webGameState.State)

	game.EvaluateGeneration()

	sendWebGameStateJSONPayload(w, http.StatusCreated, game, params)
}

func sendWebGameStateJSONPayload(w http.ResponseWriter, status int, game *GameOfLife, params *WebGameParams) {
	img, err := game.Image(params.Xmul, params.Ymul)

	if err != nil {
		handle500(err, w)
		return
	}

	log.Println("Serving state image.")

	var pngBuf bytes.Buffer
	err = png.Encode(&pngBuf, img)
	if err != nil {
		handle500(err, w)
	}

	imgB64 := base64.StdEncoding.EncodeToString(pngBuf.Bytes())
	webGameState := &WebGameState{State: game.State, Img: imgB64}
	wgsJson, err := json.Marshal(webGameState)

	if err != nil {
		handle500(err, w)
	}

	w.Header().Set("Content-Type", "application/json")
	w.WriteHeader(status)
	w.Write(wgsJson)
}

func RunWebGame(address string, height, width, sleepMs int, mutate bool) (int, error) {
	http.HandleFunc("/", HandleWebGameRoot)
	http.HandleFunc("/state", HandleWebGameState)
	http.HandleFunc("/static/", HandleWebGameStatic)

	fmt.Printf("Serving on %v\n", address)
	err := http.ListenAndServe(address, nil)
	if err != nil {
		return 1, err
	}
	return 0, nil
}