Basic golang web server.

2024/07/golang_demo1/main.go

@@ -0,0 +1,97 @@
+package main
+
+import (
+	"encoding/json"
+	"flag"
+	"fmt"
+	"net/http"
+	"time"
+)
+
+type PersonRequest struct {
+	Name string
+	Age  int
+}
+
+type PersonResponse struct {
+	Greeting string
+	Errors   string
+}
+
+type StatusResponse struct {
+	StartDateTime string
+	UpTime        string
+	Status        string
+}
+
+var startTime = time.Now()
+
+func main() {
+	portPtr := flag.Int("port", 8080, "port for webserver")
+	flag.Parse()
+	port := *portPtr
+
+	fmt.Printf("Server is listening on port: %d", port)
+
+	server := http.NewServeMux()
+	server.HandleFunc("/status", statusHandler)
+	server.HandleFunc("/greeting", greetingHandler)
+	err := http.ListenAndServe(fmt.Sprintf("localhost:%d", port), server)
+
+	if err != nil {
+		fmt.Println("Error:", err)
+		return
+	}
+}
+
+func greetingHandler(writer http.ResponseWriter, request *http.Request) {
+	decoder := json.NewDecoder(request.Body)
+	decoder.DisallowUnknownFields()
+	var p = PersonRequest{}
+	errDecode := decoder.Decode(&p)
+	if errDecode != nil {
+		println("Error: ", errDecode)
+		writer.WriteHeader(400)
+		_, _ = writer.Write([]byte("Bad request data"))
+		return
+	}
+
+	r := PersonResponse{
+		Greeting: fmt.Sprintf("Hey %s. Your age is %d", p.Name, p.Age),
+		Errors:   "",
+	}
+
+	writer.Header().Add("Content-Type", "application/json")
+	encoder := produceEncoder(writer)
+	errEncode := encoder.Encode(&r)
+	if errEncode != nil {
+		writer.WriteHeader(500)
+		println("Error: ", errEncode)
+		return
+	}
+	writer.WriteHeader(200)
+}
+
+func produceEncoder(writer http.ResponseWriter) *json.Encoder {
+	encoder := json.NewEncoder(writer)
+	return encoder
+}
+
+func statusHandler(writer http.ResponseWriter, _ *http.Request) {
+	upTime := time.Now().Unix() - startTime.Unix()
+	status := StatusResponse{
+		Status:        "Ok",
+		StartDateTime: startTime.Format("2006-01-02 15:04:05.000-0700"),
+		UpTime:        fmt.Sprintf("%d", upTime),
+	}
+
+	writer.Header().Add("Content-Type", "application/json")
+	encoder := produceEncoder(writer)
+	errEncode := encoder.Encode(&status)
+	if errEncode != nil {
+		writer.WriteHeader(500)
+		println("Error: ", errEncode)
+		return
+	}
+	writer.WriteHeader(200)
+}