8 files changed, 0 insertions, 1207 deletions
diff --git a/assets/component-oriented-design/v1/main.go b/assets/component-oriented-design/v1/main.go
deleted file mode 100644
index 490a516..0000000
--- a/assets/component-oriented-design/v1/main.go
+++ /dev/null
@@ -1,314 +0,0 @@
-package main
-
-import (
-	"encoding/json"
-	"errors"
-	"fmt"
-	"io"
-	"io/ioutil"
-	"log"
-	"math/rand"
-	"net"
-	"net/http"
-	"os"
-	"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
-
-	// 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) (*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,
-		saveLoopWaitCh: make(chan struct{}),
-	}
-
-	go scoreboard.saveLoop(saveTicker, logger)
-
-	return scoreboard, nil
-}
-
-func (s *scoreboard) guessedCorrect(name string) int {
-	s.scoresLock.Lock()
-	defer s.scoresLock.Unlock()
-
-	s.scoresM[name] += 1000
-	return s.scoresM[name]
-}
-
-func (s *scoreboard) guessedIncorrect(name string) int {
-	s.scoresLock.Lock()
-	defer s.scoresLock.Unlock()
-
-	s.scoresM[name] -= 1
-	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.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
-}
-
-////////////////////////////////////////////////////////////////////////////////
-// main
-
-const (
-	saveFilePath = "./save.json"
-	listenAddr   = ":8888"
-	saveInterval = 5 * time.Second
-)
-
-func main() {
-	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)
-	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")
-	newHTTPServer(listener, httpHandlers, logger)
-
-	logger.Printf("initialization done")
-	select {} // block forever
-}
diff --git a/assets/component-oriented-design/v1/main.md b/assets/component-oriented-design/v1/main.md
deleted file mode 100644
index 37346c6..0000000
--- a/assets/component-oriented-design/v1/main.md
+++ /dev/null
@@ -1,4 +0,0 @@
----
-layout: code
-include: main.go
----
diff --git a/assets/component-oriented-design/v1/main_test.go b/assets/component-oriented-design/v1/main_test.go
deleted file mode 100644
index 6cfd9fb..0000000
--- a/assets/component-oriented-design/v1/main_test.go
+++ /dev/null
@@ -1,167 +0,0 @@
-package main
-
-import (
-	"bytes"
-	"net/http"
-	"net/http/httptest"
-	"reflect"
-	"testing"
-	"time"
-)
-
-type nullLogger struct{}
-
-func (nullLogger) Printf(string, ...interface{}) {}
-
-////////////////////////////////////////////////////////////////////////////////
-// Test scoreboard component
-
-type fileStub struct {
-	*bytes.Buffer
-}
-
-func newFileStub(init string) *fileStub {
-	return &fileStub{Buffer: bytes.NewBufferString(init)}
-}
-
-func (fs *fileStub) Truncate(i int64) error {
-	fs.Buffer.Truncate(int(i))
-	return nil
-}
-
-func (fs *fileStub) Seek(i int64, whence int) (int64, error) {
-	return i, nil
-}
-
-func TestScoreboard(t *testing.T) {
-	newScoreboard := func(t *testing.T, fileStub *fileStub, saveTicker <-chan time.Time) *scoreboard {
-		t.Helper()
-		scoreboard, err := newScoreboard(fileStub, saveTicker, nullLogger{})
-		if err != nil {
-			t.Errorf("unexpected error checking saved scored: %v", err)
-		}
-		return scoreboard
-	}
-
-	assertScores := func(t *testing.T, expScores, gotScores map[string]int) {
-		t.Helper()
-		if !reflect.DeepEqual(expScores, gotScores) {
-			t.Errorf("expected scores of %+v, but instead got %+v", expScores, gotScores)
-		}
-	}
-
-	assertSavedScores := func(t *testing.T, expScores map[string]int, fileStub *fileStub) {
-		t.Helper()
-		fileStubCp := newFileStub(fileStub.String())
-		tmpScoreboard := newScoreboard(t, fileStubCp, nil)
-		assertScores(t, expScores, tmpScoreboard.scores())
-	}
-
-	t.Run("loading", func(t *testing.T) {
-		// make sure loading scoreboards with various file contents works
-		assertSavedScores(t, map[string]int{}, newFileStub(""))
-		assertSavedScores(t, map[string]int{"foo": 1}, newFileStub(`{"foo":1}`))
-		assertSavedScores(t, map[string]int{"foo": 1, "bar": -2}, newFileStub(`{"foo":1,"bar":-2}`))
-	})
-
-	t.Run("tracking", func(t *testing.T) {
-		scoreboard := newScoreboard(t, newFileStub(""), nil)
-		assertScores(t, map[string]int{}, scoreboard.scores()) // sanity check
-
-		scoreboard.guessedCorrect("foo")
-		assertScores(t, map[string]int{"foo": 1000}, scoreboard.scores())
-
-		scoreboard.guessedIncorrect("bar")
-		assertScores(t, map[string]int{"foo": 1000, "bar": -1}, scoreboard.scores())
-
-		scoreboard.guessedIncorrect("foo")
-		assertScores(t, map[string]int{"foo": 999, "bar": -1}, scoreboard.scores())
-	})
-
-	t.Run("saving", func(t *testing.T) {
-		// this test tests scoreboard's periodic save feature using a ticker
-		// channel which will be written to manually. The saveLoopWaitCh is used
-		// here to ensure that each ticker has been fully processed.
-		ticker := make(chan time.Time)
-		fileStub := newFileStub("")
-		scoreboard := newScoreboard(t, fileStub, ticker)
-
-		tick := func() {
-			ticker <- time.Time{}
-			scoreboard.saveLoopWaitCh <- struct{}{}
-		}
-
-		// this should not effect the save file at first
-		scoreboard.guessedCorrect("foo")
-		assertSavedScores(t, map[string]int{}, fileStub)
-
-		// after the ticker the new score should get saved
-		tick()
-		assertSavedScores(t, map[string]int{"foo": 1000}, fileStub)
-
-		// ticker again after no changes should save the same thing as before
-		tick()
-		assertSavedScores(t, map[string]int{"foo": 1000}, fileStub)
-
-		// buffer a bunch of changes, shouldn't get saved till after tick
-		scoreboard.guessedCorrect("foo")
-		scoreboard.guessedCorrect("bar")
-		scoreboard.guessedCorrect("bar")
-		assertSavedScores(t, map[string]int{"foo": 1000}, fileStub)
-		tick()
-		assertSavedScores(t, map[string]int{"foo": 2000, "bar": 2000}, fileStub)
-	})
-}
-
-////////////////////////////////////////////////////////////////////////////////
-// Test httpHandlers component
-
-type mockScoreboard map[string]int
-
-func (mockScoreboard) guessedCorrect(name string) int { return 1 }
-
-func (mockScoreboard) guessedIncorrect(name string) int { return -1 }
-
-func (m mockScoreboard) scores() map[string]int { return m }
-
-type mockRandSrc struct{}
-
-func (m mockRandSrc) Int() int { return 666 }
-
-func TestHTTPHandlers(t *testing.T) {
-	mockScoreboard := mockScoreboard{"foo": 1, "bar": 2}
-	httpHandlers := newHTTPHandlers(mockScoreboard, mockRandSrc{}, nullLogger{})
-
-	assertRequest := func(t *testing.T, expCode int, expBody string, r *http.Request) {
-		t.Helper()
-		rw := httptest.NewRecorder()
-		httpHandlers.ServeHTTP(rw, r)
-		if rw.Code != expCode {
-			t.Errorf("expected HTTP response code %d, got %d", expCode, rw.Code)
-		} else if rw.Body.String() != expBody {
-			t.Errorf("expected HTTP response body %q, got %q", expBody, rw.Body.String())
-		}
-	}
-
-	r := httptest.NewRequest("GET", "/guess?name=foo&n=665", nil)
-	assertRequest(t, 400, "Try higher. Your score is now -1\n", r)
-
-	r = httptest.NewRequest("GET", "/guess?name=foo&n=667", nil)
-	assertRequest(t, 400, "Try lower. Your score is now -1\n", r)
-
-	r = httptest.NewRequest("GET", "/guess?name=foo&n=666", nil)
-	assertRequest(t, 200, "Correct! Your score is now 1\n", r)
-
-	r = httptest.NewRequest("GET", "/scores", nil)
-	assertRequest(t, 200, "bar: 2\nfoo: 1\n", r)
-}
-
-////////////////////////////////////////////////////////////////////////////////
-//
-// httpServer is NOT tested, for the following reasons:
-// * It depends on a `net.Listener`, which is not trivial to mock.
-// * It does very little besides passing an httpHandlers along to an http.Server
-//   and managing cleanup.
-// * It isn't likely to be changed often.
-// * If it were to break it would be very apparent in subsequent testing stages.
-//
diff --git a/assets/component-oriented-design/v1/main_test.md b/assets/component-oriented-design/v1/main_test.md
deleted file mode 100644
index b0a0751..0000000
--- a/assets/component-oriented-design/v1/main_test.md
+++ /dev/null
@@ -1,4 +0,0 @@
----
-layout: code
-include: main_test.go
----
diff --git a/assets/component-oriented-design/v2/main.go b/assets/component-oriented-design/v2/main.go
deleted file mode 100644
index fb5773c..0000000
--- a/assets/component-oriented-design/v2/main.go
+++ /dev/null
@@ -1,320 +0,0 @@
-package main
-
-import (
-	"encoding/json"
-	"errors"
-	"flag"
-	"fmt"
-	"io"
-	"io/ioutil"
-	"log"
-	"math/rand"
-	"net"
-	"net/http"
-	"os"
-	"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
-
-	// 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,
-		saveLoopWaitCh:    make(chan struct{}),
-	}
-
-	go scoreboard.saveLoop(saveTicker, logger)
-
-	return scoreboard, 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.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
-}
-
-////////////////////////////////////////////////////////////////////////////////
-// 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")
-	newHTTPServer(listener, httpHandlers, logger)
-
-	logger.Printf("initialization done")
-	select {} // block forever
-}
diff --git a/assets/component-oriented-design/v2/main.md b/assets/component-oriented-design/v2/main.md
deleted file mode 100644
index 37346c6..0000000
--- a/assets/component-oriented-design/v2/main.md
+++ /dev/null
@@ -1,4 +0,0 @@
----
-layout: code
-include: main.go
----
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
----