summaryrefslogtreecommitdiff
path: root/assets/component-oriented-design/v3
diff options
context:
space:
mode:
authorBrian Picciano <mediocregopher@gmail.com>2021-01-21 17:22:53 -0700
committerBrian Picciano <mediocregopher@gmail.com>2021-01-21 17:22:53 -0700
commitbcf9b230be6d74c71567fd0771b31d47d8dd39c7 (patch)
tree2d0fc16142d55bbd5876ac6b8174c2857883b40e /assets/component-oriented-design/v3
parentd57fd70640948cf20eeb41b56e8d4e23e616cec0 (diff)
build the blog with nix
Diffstat (limited to 'assets/component-oriented-design/v3')
-rw-r--r--assets/component-oriented-design/v3/main.go390
-rw-r--r--assets/component-oriented-design/v3/main.md4
2 files changed, 0 insertions, 394 deletions
diff --git a/assets/component-oriented-design/v3/main.go b/assets/component-oriented-design/v3/main.go
deleted file mode 100644
index afe8bab..0000000
--- a/assets/component-oriented-design/v3/main.go
+++ /dev/null
@@ -1,390 +0,0 @@
-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()
-}
diff --git a/assets/component-oriented-design/v3/main.md b/assets/component-oriented-design/v3/main.md
deleted file mode 100644
index 37346c6..0000000
--- a/assets/component-oriented-design/v3/main.md
+++ /dev/null
@@ -1,4 +0,0 @@
----
-layout: code
-include: main.go
----