add ch14

ch12/3/ch12_3.go

@@ -0,0 +1,28 @@
+package main
+
+import (
+	"fmt"
+	"math"
+	"sync"
+)
+
+func CreateSqrtMap() map[int]float64 {
+	numKeys := 100_000
+	newMap := make(map[int]float64)
+
+	for i := range numKeys {
+		newMap[i] = math.Sqrt(float64(i))
+	}
+	return newMap
+}
+
+var initCreateMapSqrt func() map[int]float64 = sync.OnceValue(CreateSqrtMap)
+
+func main() {
+	sqrtMap := initCreateMapSqrt()
+	n := 100_000 / 1_000
+	for i := range n {
+		keyVal := i * 1_000
+		fmt.Printf("Value of map by key[%d]: %f\n", keyVal, sqrtMap[keyVal])
+	}
+}

ch12/3/go.mod

@@ -0,0 +1,3 @@
+module gitea.local.lab/Lbenedar/learning_go/ch12/3
+
+go 1.25.0

ch13/1/ch13_1.go

@@ -0,0 +1,28 @@
+package main
+
+import (
+	"net/http"
+	"time"
+)
+
+type TimeHandler struct{}
+
+func (th TimeHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
+	w.Write([]byte(time.Now().Format(time.RFC3339)))
+}
+
+func main() {
+	server := http.Server{
+		Addr:         ":10100",
+		ReadTimeout:  30 * time.Second,
+		WriteTimeout: 90 * time.Second,
+		IdleTimeout:  120 * time.Second,
+		Handler:      TimeHandler{},
+	}
+	err := server.ListenAndServe()
+	if err != nil {
+		if err != http.ErrServerClosed {
+			panic(err)
+		}
+	}
+}

ch13/1/go.mod

@@ -0,0 +1,3 @@
+module gitea.local.lab/Lbenedar/learning_go/ch13/1
+
+go 1.25.0

ch13/2/ch13_2.go

@@ -0,0 +1,46 @@
+package main
+
+import (
+	"fmt"
+	"log/slog"
+	"net"
+	"net/http"
+	"time"
+)
+
+type TimeHandler struct{}
+
+func (th TimeHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
+	w.Write([]byte(time.Now().Format(time.RFC3339)))
+}
+
+func RequestToIP(r *http.Request) string {
+	ip, _, err := net.SplitHostPort(r.RemoteAddr)
+	if err != nil {
+		slog.Error(fmt.Sprintf("Wrong format of address: %q", r.RemoteAddr))
+	}
+	return ip
+}
+
+func RequestIPHandler(h http.Handler) http.Handler {
+	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		slog.Info(RequestToIP(r))
+		h.ServeHTTP(w, r)
+	})
+}
+
+func main() {
+	server := http.Server{
+		Addr:         ":10100",
+		ReadTimeout:  30 * time.Second,
+		WriteTimeout: 90 * time.Second,
+		IdleTimeout:  120 * time.Second,
+		Handler:      RequestIPHandler(TimeHandler{}),
+	}
+	err := server.ListenAndServe()
+	if err != nil {
+		if err != http.ErrServerClosed {
+			panic(err)
+		}
+	}
+}

ch13/2/go.mod

@@ -0,0 +1,3 @@
+module gitea.local.lab/Lbenedar/learning_go/ch13/2
+
+go 1.25.0

ch13/3/ch13_3.go

@@ -0,0 +1,86 @@
+package main
+
+import (
+	"bytes"
+	"encoding/json"
+	"fmt"
+	"log/slog"
+	"net"
+	"net/http"
+	"time"
+)
+
+type RFCTime struct {
+	DayOfWeek  string `json:"day_of_week"`
+	DayOfMonth int    `json:"day_of_month"`
+	Month      string `json:"month"`
+	Year       int    `json:"year"`
+	Hour       int    `json:"hour"`
+	Minute     int    `json:"minute"`
+	Second     int    `json:"second"`
+}
+
+type TimeHandler struct{}
+
+func StructToJsString(data any) string {
+	var b bytes.Buffer
+	enc := json.NewEncoder(&b)
+	err := enc.Encode(data)
+	if err != nil {
+		slog.Error("Problems with encoding json")
+	}
+	return b.String()
+}
+
+func (th TimeHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
+	headerAccept := http.Header.Get(r.Header, "Accept")
+	var output string
+	switch headerAccept {
+	case "application/json":
+		currTime := time.Now()
+		rfcTime := RFCTime{
+			DayOfWeek:  currTime.Weekday().String(),
+			DayOfMonth: currTime.Day(),
+			Month:      currTime.Month().String(),
+			Year:       currTime.Year(),
+			Hour:       currTime.Hour(),
+			Minute:     currTime.Minute(),
+			Second:     currTime.Second(),
+		}
+		output = StructToJsString(rfcTime)
+	default:
+		output = time.Now().Format(time.RFC3339)
+	}
+	w.Write([]byte(output))
+}
+
+func RequestToIP(r *http.Request) string {
+	ip, _, err := net.SplitHostPort(r.RemoteAddr)
+	if err != nil {
+		slog.Error(fmt.Sprintf("Wrong format of address: %q", r.RemoteAddr))
+	}
+	return ip
+}
+
+func RequestIPHandler(h http.Handler) http.Handler {
+	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		slog.Info(RequestToIP(r))
+		h.ServeHTTP(w, r)
+	})
+}
+
+func main() {
+	server := http.Server{
+		Addr:         ":10100",
+		ReadTimeout:  30 * time.Second,
+		WriteTimeout: 90 * time.Second,
+		IdleTimeout:  120 * time.Second,
+		Handler:      RequestIPHandler(TimeHandler{}),
+	}
+	err := server.ListenAndServe()
+	if err != nil {
+		if err != http.ErrServerClosed {
+			panic(err)
+		}
+	}
+}

ch13/3/go.mod

@@ -0,0 +1,3 @@
+module gitea.local.lab/Lbenedar/learning_go/ch13/3
+
+go 1.25.0

ch14/1/ch14_1.go

@@ -0,0 +1,24 @@
+package main
+
+import (
+	"context"
+	"net/http"
+	"time"
+)
+
+type MsReq struct{}
+
+func CreateTimeoutCtx(msReq time.Duration) func(http.Handler) http.Handler {
+	return func(h http.Handler) http.Handler {
+		return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+			reqCtx := r.Context()
+			reqCtx = context.WithValue(reqCtx, MsReq{}, msReq)
+			r.WithContext(reqCtx)
+			h.ServeHTTP(w, r)
+		})
+	}
+}
+
+func main() {
+
+}

ch14/1/go.mod

@@ -0,0 +1,3 @@
+module gitea.local.lab/Lbenedar/learning_go/ch14/1
+
+go 1.25.0

ch14/2/ch14_2.go

@@ -0,0 +1,36 @@
+package main
+
+import (
+	"context"
+	"fmt"
+	"math/rand"
+	"time"
+)
+
+type RandSum struct{}
+
+func main() {
+	sum := 0
+	ctx, cancel := context.WithTimeout(context.Background(), time.Duration(2)*time.Second)
+	defer cancel()
+	start := time.Now()
+	i := 0
+outLoop:
+	for {
+		select {
+		case <-ctx.Done():
+			ctx = context.WithValue(ctx, RandSum{}, "timeout")
+			break outLoop
+		default:
+			i++
+			randNum := rand.Int() % 100_000_000
+			//fmt.Printf("Randnum is %d\n", randNum)
+			sum = sum + randNum
+			if randNum == 1234 {
+				ctx = context.WithValue(ctx, RandSum{}, "number reached")
+				break outLoop
+			}
+		}
+	}
+	fmt.Printf("Sum is %d after %v; iterations - %d; cause - %s\n", sum, time.Since(start), i, ctx.Value(RandSum{}))
+}

ch14/2/go.mod

@@ -0,0 +1,3 @@
+module gitea.local.lab/Lbenedar/learning_go/ch14/2
+
+go 1.25.0

ch14/3/ch14_3.go

@@ -0,0 +1,67 @@
+package main
+
+import (
+	"context"
+	"fmt"
+	"log/slog"
+	"net/http"
+	"time"
+)
+
+type TimeHandler struct{}
+
+func (th TimeHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
+	w.Write([]byte(time.Now().Format(time.RFC3339)))
+}
+
+type Level string
+
+const (
+	Debug Level = "debug"
+	Info  Level = "info"
+)
+
+func ExtractLogLevel(ctx context.Context) Level {
+	return ctx.Value("log_level").(Level)
+}
+
+func StoreLogLevel(ctx context.Context, level Level) context.Context {
+	return context.WithValue(ctx, "log_level", level)
+}
+
+func GetLogLevelQuery(http.Handler) http.Handler {
+	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		logLevel := r.URL.Query().Get("log_level")
+		if logLevel != "info" && logLevel != "debug" {
+			slog.Info("Wrong logLevel")
+		}
+		Log(StoreLogLevel(r.Context(), Level(logLevel)), Debug, "Test message")
+	})
+}
+
+func Log(ctx context.Context, level Level, message string) {
+	var inLevel Level
+	inLevel = ExtractLogLevel(ctx)
+	if level == Debug && inLevel == Debug {
+		fmt.Println(message)
+	}
+	if level == Info && (inLevel == Debug || inLevel == Info) {
+		fmt.Println(message)
+	}
+}
+
+func main() {
+	server := http.Server{
+		Addr:         ":10100",
+		ReadTimeout:  30 * time.Second,
+		WriteTimeout: 90 * time.Second,
+		IdleTimeout:  120 * time.Second,
+		Handler:      GetLogLevelQuery(TimeHandler{}),
+	}
+	err := server.ListenAndServe()
+	if err != nil {
+		if err != http.ErrServerClosed {
+			panic(err)
+		}
+	}
+}

ch14/3/go.mod

@@ -0,0 +1,3 @@
+module gitea.local.lab/Lbenedar/learning_go/ch14/3
+
+go 1.25.0