main.go

package main

import (
	"encoding/json"
	"flag"
	"log"
	"net/http"
	"os"
)

func main() {
	filename := flag.String("file", "logs.json", "file to append logs that is send to this server")
	addr := flag.String("address", "127.0.0.1:8081", "address for the server to bind to")

	flag.Parse()

	// Open the logs file for appending (create it if it does not exist).
	f, err := os.OpenFile(*filename, os.O_APPEND|os.O_WRONLY, 0666)
	if err != nil {
		if !os.IsNotExist(err) {
			log.Fatalf("could not open the logs file: %s", err)
		}

		f, err = os.Create(*filename)
		if err != nil {
			log.Fatalf("could not create the logs file: %s", err)
		}
	}
	defer f.Close()

	// Create the JSON encoder. When objects are encoded into the encoder it
	// will write it to the writer (the file in this case) followed by a
	// newline.
	encoder := json.NewEncoder(f)

	http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
		if r.Method != http.MethodPost {
			log.Printf("unexpected method: %s", r.Method)
			http.Error(w, http.StatusText(http.StatusMethodNotAllowed), http.StatusMethodNotAllowed)
			return
		}

		contentType := r.Header.Get("content-type")
		if contentType != "application/json" {
			log.Printf("unexpected content type: %s", contentType)
			http.Error(w, http.StatusText(http.StatusBadRequest), http.StatusBadRequest)
			return
		}

		var packets []map[string]interface{}
		if err := json.NewDecoder(r.Body).Decode(&packets); err != nil {
			log.Printf("could not decode request: %s", err)
			http.Error(w, http.StatusText(http.StatusInternalServerError), http.StatusInternalServerError)
			return
		}

		for _, packet := range packets {
			if err := encoder.Encode(packet); err != nil {
				log.Printf("could not encode packet: %s", err)
				http.Error(w, http.StatusText(http.StatusInternalServerError), http.StatusInternalServerError)
				return
			}
		}

		w.WriteHeader(http.StatusNoContent)
	})

	log.Printf("listening on %s", *addr)
	if err := http.ListenAndServe(*addr, nil); err != nil {
		log.Fatalf("could not listen and serve: %s", err)
	}
}