package main

import (
	"fmt"
	"io/ioutil"
	"log"
	"net"
	"net/http"
	"os"
	"time"
)

var version string

var tracer = []string{
	"x-request-id",
	"x-b3-traceid",
	"x-b3-spanid",
	"x-b3-parentspanid",
	"x-b3-sampled",
	"x-b3-flags",
	"x-ot-span-context",
}

func trace(rd, rs *http.Request) {
	if rd == nil || rs == nil {
		return
	}
	for _, t := range tracer {
		v := rs.Header.Get(t)
		if v != "" {
			rd.Header.Set(t, v)
		}
	}
}

func get(c *http.Client, req *http.Request, url string) (body string, err error) {
	r, err := http.NewRequest("GET", url, nil)
	if err != nil {
		return
	}
	trace(r, req)
	resp, err := c.Do(r)
	if err != nil {
		return
	}
	defer resp.Body.Close()
	b, err := ioutil.ReadAll(resp.Body)
	if err != nil {
		return
	}
	body = string(b)
	return
}

func main() {
	http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
		log.Printf("%s %s %s", r.RemoteAddr, r.Method, r.URL)
		h, err := os.Hostname()
		if err != nil {
			http.Error(w, err.Error(), http.StatusInternalServerError)
			return
		}
		c := &http.Client{Transport: &http.Transport{
			DialContext: (&net.Dialer{
				Timeout: 5 * time.Second,
			}).DialContext,
		}}
		health, err := get(c, r, "http://testapp-db:8080/healthz")
		if err != nil {
			health = err.Error()
		}
		ext, err := get(c, nil, "http://httpbin.org/robots.txt")
		if err != nil {
			ext = err.Error()
		}
		fmt.Fprintf(w, "%s (%s) DB Health: '%s' external GET: '%s'", h, version, health, ext)
	})
	http.HandleFunc("/healthz", func(w http.ResponseWriter, r *http.Request) {
		log.Printf("%s %s %s", r.RemoteAddr, r.Method, r.URL)
		fmt.Fprintf(w, "api: ok")
	})
	http.HandleFunc("/favicon.ico", func(w http.ResponseWriter, r *http.Request) {
		w.WriteHeader(http.StatusNotFound)
	})
	s := &http.Server{
		ReadTimeout:  5 * time.Second,
		WriteTimeout: 10 * time.Second,
		IdleTimeout:  120 * time.Second,
		Addr:         ":8080",
	}
	log.Fatal(s.ListenAndServe())
}