package main

import (
	"encoding/json"
	"fmt"
	"log"
	"net/http"
	"net/http/httputil"
	"os"
	"strings"
)

type listeners struct {
	Maven string `json:"maven"`
	Cargo string `json:"cargo"`
}

type config struct {
	Listen        listeners `json:"listen"`
	Domain        string    `json:"domain"`
	Organizations []string  `json:"organizations"`
}

func searcher(config *config, dst string, useGet bool, w http.ResponseWriter, r *http.Request) {
	for _, org := range config.Organizations {
		actualUrl := fmt.Sprintf(
			dst,
			config.Domain, org, strings.TrimLeft(r.URL.Path, "/"),
		)

		var resp *http.Response
		var err error
		if useGet {
			resp, err = http.Get(actualUrl)
		} else {
			resp, err = http.Head(actualUrl)
		}
		if err != nil {
			w.WriteHeader(500)
			_, err := fmt.Fprintf(w, "%v", err)
			if err != nil {
				log.Fatal(err)
			}
			return
		}
		switch resp.StatusCode {
		case 200:
			w.Header().Set("Location", actualUrl)
			w.WriteHeader(307)
			return
		case 404:
			fallthrough
		case 403:
			continue
		case 502:
			fallthrough
		case 503:
			w.WriteHeader(503)
			return
		default:
			w.WriteHeader(500)
			rawResp, err := httputil.DumpResponse(resp, true)
			if err != nil {
				log.Fatal(err)
				return
			}
			_, err = w.Write(rawResp)
			if err != nil {
				log.Fatal(err)
				return
			}
			return
		}
	}
	w.WriteHeader(404)
}

func readConfig(path string) config {
	file, err := os.Open(path)
	if err != nil {
		panic(err)
	}

	var data config
	if err := json.NewDecoder(file).Decode(&data); err != nil {
		panic(err)
	}

	if err := file.Close(); err != nil {
		panic(err)
	}

	return data
}

func main() {
	if len(os.Args) < 2 {
		fmt.Println("Missed path to config")
		return
	}
	if len(os.Args) > 2 {
		fmt.Println("Excess arguments")
		return
	}

	config := readConfig(os.Args[1])
	if config.Organizations == nil {
		fmt.Println("Missed organizations list")
		return
	}

	go func() {
		dispatcher := http.NewServeMux()
		dispatcher.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
			searcher(&config, "https://%s/api/packages/%s/maven/%s", false, w, r)
		})
		server := http.Server{
			Addr:    config.Listen.Maven,
			Handler: dispatcher,
		}
		log.Fatal(server.ListenAndServe())
	}()

	go func() {
		dispatcher := http.NewServeMux()
		dispatcher.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
			searcher(&config, "https://%s/api/packages/%s/cargo/%s", true, w, r)
		})
		server := http.Server{
			Addr:    config.Listen.Cargo,
			Handler: dispatcher,
		}
		log.Fatal(server.ListenAndServe())
	}()

	select {}
}