From 4f01edb9230f58ff84b0dd892c931ec8ac9aad55 Mon Sep 17 00:00:00 2001 From: Brian Picciano Date: Tue, 13 Sep 2022 12:56:08 +0200 Subject: move src out of srv, clean up default.nix and Makefile --- .../static/component-oriented-design/v3/main.go | 390 +++++++++++++++++++++ 1 file changed, 390 insertions(+) create mode 100644 src/http/static/component-oriented-design/v3/main.go (limited to 'src/http/static/component-oriented-design/v3/main.go') diff --git a/src/http/static/component-oriented-design/v3/main.go b/src/http/static/component-oriented-design/v3/main.go new file mode 100644 index 0000000..afe8bab --- /dev/null +++ b/src/http/static/component-oriented-design/v3/main.go @@ -0,0 +1,390 @@ +package main + +import ( + "context" + "encoding/json" + "errors" + "flag" + "fmt" + "io" + "io/ioutil" + "log" + "math/rand" + "net" + "net/http" + "os" + "os/signal" + "sort" + "strconv" + "sync" + "time" +) + +// Logger describes a simple component used for printing log lines. +type Logger interface { + Printf(string, ...interface{}) +} + +//////////////////////////////////////////////////////////////////////////////// +// The scoreboard component + +// File wraps the standard os.File type. +type File interface { + io.ReadWriter + Truncate(int64) error + Seek(int64, int) (int64, error) +} + +// scoreboard loads player scores from a save file, tracks score updates, and +// periodically saves those scores back to the save file. +type scoreboard struct { + file File + scoresM map[string]int + scoresLock sync.Mutex + + pointsOnCorrect, pointsOnIncorrect int + + // The cleanup method closes cleanupCh to signal to all scoreboard's running + // go-routines to clean themselves up, and cleanupWG is then used to wait + // for those goroutines to do so. + cleanupCh chan struct{} + cleanupWG sync.WaitGroup + + // this field will only be set in tests, and is used to synchronize with the + // the for-select loop in saveLoop. + saveLoopWaitCh chan struct{} +} + +// newScoreboard initializes a scoreboard using scores saved in the given File +// (which may be empty). The scoreboard will rewrite the save file with the +// latest scores everytime saveTicker is written to. +func newScoreboard(file File, saveTicker <-chan time.Time, logger Logger, pointsOnCorrect, pointsOnIncorrect int) (*scoreboard, error) { + fileBody, err := ioutil.ReadAll(file) + if err != nil { + return nil, fmt.Errorf("reading saved scored: %w", err) + } + + scoresM := map[string]int{} + if len(fileBody) > 0 { + if err := json.Unmarshal(fileBody, &scoresM); err != nil { + return nil, fmt.Errorf("decoding saved scores: %w", err) + } + } + + scoreboard := &scoreboard{ + file: file, + scoresM: scoresM, + pointsOnCorrect: pointsOnCorrect, + pointsOnIncorrect: pointsOnIncorrect, + cleanupCh: make(chan struct{}), + saveLoopWaitCh: make(chan struct{}), + } + + scoreboard.cleanupWG.Add(1) + go func() { + scoreboard.saveLoop(saveTicker, logger) + scoreboard.cleanupWG.Done() + }() + + return scoreboard, nil +} + +func (s *scoreboard) cleanup() error { + close(s.cleanupCh) + s.cleanupWG.Wait() + + if err := s.save(); err != nil { + return fmt.Errorf("saving scores during cleanup: %w", err) + } + return nil +} + +func (s *scoreboard) guessedCorrect(name string) int { + s.scoresLock.Lock() + defer s.scoresLock.Unlock() + + s.scoresM[name] += s.pointsOnCorrect + return s.scoresM[name] +} + +func (s *scoreboard) guessedIncorrect(name string) int { + s.scoresLock.Lock() + defer s.scoresLock.Unlock() + + s.scoresM[name] += s.pointsOnIncorrect + return s.scoresM[name] +} + +func (s *scoreboard) scores() map[string]int { + s.scoresLock.Lock() + defer s.scoresLock.Unlock() + + scoresCp := map[string]int{} + for name, score := range s.scoresM { + scoresCp[name] = score + } + + return scoresCp +} + +func (s *scoreboard) save() error { + scores := s.scores() + if _, err := s.file.Seek(0, 0); err != nil { + return fmt.Errorf("seeking to start of save file: %w", err) + } else if err := s.file.Truncate(0); err != nil { + return fmt.Errorf("truncating save file: %w", err) + } else if err := json.NewEncoder(s.file).Encode(scores); err != nil { + return fmt.Errorf("encoding scores to save file: %w", err) + } + return nil +} + +func (s *scoreboard) saveLoop(ticker <-chan time.Time, logger Logger) { + for { + select { + case <-ticker: + if err := s.save(); err != nil { + logger.Printf("error saving scoreboard to file: %v", err) + } + case <-s.cleanupCh: + return + case <-s.saveLoopWaitCh: + // test will unblock, nothing to do here. + } + } +} + +//////////////////////////////////////////////////////////////////////////////// +// The httpHandlers component + +// Scoreboard describes the scoreboard component from the point of view of the +// httpHandler component (which only needs a subset of scoreboard's methods). +type Scoreboard interface { + guessedCorrect(name string) int + guessedIncorrect(name string) int + scores() map[string]int +} + +// RandSrc describes a randomness component which can produce random integers. +type RandSrc interface { + Int() int +} + +// httpHandlers implements the http.HandlerFuncs used by the httpServer. +type httpHandlers struct { + scoreboard Scoreboard + randSrc RandSrc + logger Logger + + mux *http.ServeMux + n int + nLock sync.Mutex +} + +func newHTTPHandlers(scoreboard Scoreboard, randSrc RandSrc, logger Logger) *httpHandlers { + n := randSrc.Int() + logger.Printf("first n is %v", n) + + httpHandlers := &httpHandlers{ + scoreboard: scoreboard, + randSrc: randSrc, + logger: logger, + mux: http.NewServeMux(), + n: n, + } + + httpHandlers.mux.HandleFunc("/guess", httpHandlers.handleGuess) + httpHandlers.mux.HandleFunc("/scores", httpHandlers.handleScores) + + return httpHandlers +} + +func (h *httpHandlers) ServeHTTP(rw http.ResponseWriter, r *http.Request) { + h.mux.ServeHTTP(rw, r) +} + +func (h *httpHandlers) handleGuess(rw http.ResponseWriter, r *http.Request) { + r.Header.Set("Content-Type", "text/plain") + + name := r.FormValue("name") + nStr := r.FormValue("n") + if name == "" || nStr == "" { + http.Error(rw, `"name" and "n" GET args are required`, http.StatusBadRequest) + return + } + + n, err := strconv.Atoi(nStr) + if err != nil { + http.Error(rw, err.Error(), http.StatusBadRequest) + return + } + + h.nLock.Lock() + defer h.nLock.Unlock() + + if h.n == n { + newScore := h.scoreboard.guessedCorrect(name) + h.n = h.randSrc.Int() + h.logger.Printf("new n is %v", h.n) + rw.WriteHeader(http.StatusOK) + fmt.Fprintf(rw, "Correct! Your score is now %d\n", newScore) + return + } + + hint := "higher" + if h.n < n { + hint = "lower" + } + + newScore := h.scoreboard.guessedIncorrect(name) + rw.WriteHeader(http.StatusBadRequest) + fmt.Fprintf(rw, "Try %s. Your score is now %d\n", hint, newScore) +} + +func (h *httpHandlers) handleScores(rw http.ResponseWriter, r *http.Request) { + r.Header.Set("Content-Type", "text/plain") + + h.nLock.Lock() + defer h.nLock.Unlock() + + type scoreTup struct { + name string + score int + } + + scores := h.scoreboard.scores() + scoresTups := make([]scoreTup, 0, len(scores)) + for name, score := range scores { + scoresTups = append(scoresTups, scoreTup{name, score}) + } + + sort.Slice(scoresTups, func(i, j int) bool { + return scoresTups[i].score > scoresTups[j].score + }) + + for _, scoresTup := range scoresTups { + fmt.Fprintf(rw, "%s: %d\n", scoresTup.name, scoresTup.score) + } +} + +//////////////////////////////////////////////////////////////////////////////// +// The httpServer component. + +type httpServer struct { + httpServer *http.Server + errCh chan error +} + +func newHTTPServer(listener net.Listener, httpHandlers *httpHandlers, logger Logger) *httpServer { + loggingHandler := http.HandlerFunc(func(rw http.ResponseWriter, r *http.Request) { + ip, _, _ := net.SplitHostPort(r.RemoteAddr) + logger.Printf("HTTP request -> %s %s %s", ip, r.Method, r.URL.String()) + httpHandlers.ServeHTTP(rw, r) + }) + + server := &httpServer{ + httpServer: &http.Server{ + Handler: loggingHandler, + }, + errCh: make(chan error, 1), + } + + go func() { + err := server.httpServer.Serve(listener) + if errors.Is(err, http.ErrServerClosed) { + err = nil + } + server.errCh <- err + }() + + return server +} + +func (s *httpServer) cleanup() error { + ctx, cancel := context.WithTimeout(context.Background(), 30*time.Second) + defer cancel() + if err := s.httpServer.Shutdown(ctx); err != nil { + return fmt.Errorf("shutting down http server: %w", err) + } + return <-s.errCh +} + +//////////////////////////////////////////////////////////////////////////////// +// main + +func main() { + saveFilePath := flag.String("save-file", "./save.json", "File used to save scores") + listenAddr := flag.String("listen-addr", ":8888", "Address to listen for HTTP requests on") + saveInterval := flag.Duration("save-interval", 5*time.Second, "How often to resave scores") + pointsOnCorrect := flag.Int("points-on-correct", 1000, "Amount to change a user's score by upon a correct score") + pointsOnIncorrect := flag.Int("points-on-incorrect", -1, "Amount to change a user's score by upon an incorrect score") + flag.Parse() + + logger := log.New(os.Stdout, "", log.LstdFlags) + + logger.Printf("opening scoreboard save file %q", *saveFilePath) + file, err := os.OpenFile(*saveFilePath, os.O_RDWR|os.O_CREATE, 0644) + if err != nil { + logger.Fatalf("failed to open file %q: %v", *saveFilePath, err) + } + + saveTicker := time.NewTicker(*saveInterval) + randSrc := rand.New(rand.NewSource(time.Now().UnixNano())) + + logger.Printf("initializing scoreboard") + scoreboard, err := newScoreboard(file, saveTicker.C, logger, *pointsOnCorrect, *pointsOnIncorrect) + if err != nil { + logger.Fatalf("failed to initialize scoreboard: %v", err) + } + + logger.Printf("listening on %q", *listenAddr) + listener, err := net.Listen("tcp", *listenAddr) + if err != nil { + logger.Fatalf("failed to listen on %q: %v", *listenAddr, err) + } + + logger.Printf("setting up HTTP handlers") + httpHandlers := newHTTPHandlers(scoreboard, randSrc, logger) + + logger.Printf("serving HTTP requests") + httpServer := newHTTPServer(listener, httpHandlers, logger) + + logger.Printf("initialization done, waiting for interrupt signal") + sigCh := make(chan os.Signal) + signal.Notify(sigCh, os.Interrupt) + <-sigCh + logger.Printf("interrupt signal received, cleaning up") + go func() { + <-sigCh + log.Fatalf("interrupt signal received again, forcing shutdown") + }() + + if err := httpServer.cleanup(); err != nil { + logger.Fatalf("cleaning up http server: %v", err) + } + + // NOTE go's builtin http server does not follow component property 5a, and + // instead closes the net.Listener given to it as a parameter when Shutdown + // is called. Because of that inconsistency this Close would error if it + // were called. + // + // While there are ways to work around this, it's instead highlighted in + // this example as an instance of a language making the component-oriented + // pattern more difficult. + // + //if err := listener.Close(); err != nil { + // logger.Fatalf("closing listener %q: %v", listenAddr, err) + //} + + if err := scoreboard.cleanup(); err != nil { + logger.Fatalf("cleaning up scoreboard: %v", err) + } + + saveTicker.Stop() + + if err := file.Close(); err != nil { + logger.Fatalf("closing file %q: %v", *saveFilePath, err) + } + + os.Stdout.Sync() +} -- cgit v1.2.3