package main

import (
	"context"
	"fmt"
	"io"
	"log"
	"net/http"
	"os"

	"golang.org/x/oauth2"
)

func main() {
	authConfigPath := os.Getenv("AUTH_CONFIG")
	if authConfigPath == "" {
		log.Fatalf("AUTH_CONFIG env is missing")
	}

	token, err := readConfig(authConfigPath)
	if err != nil {
		log.Fatalf("failed to read config file: %v\n", err)
	}

	oauthConfig := oauth2.Config{
		ClientID:     os.Getenv("CLIENT_ID"),
		ClientSecret: os.Getenv("CLIENT_SECRET"),
		Endpoint: oauth2.Endpoint{
			AuthURL:       os.Getenv("AUTH_URL"),
			TokenURL:      os.Getenv("TOKEN_URL"),
			DeviceAuthURL: os.Getenv("DEVICE_AUTH_URL"),
			AuthStyle:     oauth2.AuthStyleAutoDetect,
		},
		RedirectURL: os.Getenv("REDIRECT_URI"),
	}

	oauthClient := oauthConfig.Client(context.Background(), token)

	mux := http.NewServeMux()

	mux.HandleFunc("GET /oauth", func(w http.ResponseWriter, r *http.Request) {
		http.Redirect(w, r, oauthConfig.AuthCodeURL(""), http.StatusTemporaryRedirect)
	})

	mux.HandleFunc("GET /oauth/callback", func(w http.ResponseWriter, r *http.Request) {
		token, err = oauthConfig.Exchange(context.Background(), r.URL.Query().Get("code"))
		if err != nil {
			http.Error(w, err.Error(), 500)
			return
		}

		oauthClient = oauthConfig.Client(context.Background(), token)
		if err := writeConfig(authConfigPath, token); err != nil {
			http.Error(w, err.Error(), 500)
			return
		}

		w.WriteHeader(200)
		fmt.Fprintf(w, "ok")
	})

	mux.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
		tokenSource := oauthConfig.TokenSource(context.Background(), token)
		newToken, err := tokenSource.Token()
		if err != nil {
			http.Error(w, fmt.Sprintf("failed to get new token: %v", err), 500)
			return
		}

		if newToken.AccessToken != token.AccessToken {
			if err := writeConfig(authConfigPath, newToken); err != nil {
				http.Error(w, fmt.Sprintf("failed to save new token: %v", err), 500)
				return
			}
		}

		baseURL := os.Getenv("API_URL")
		req, err := http.NewRequest(r.Method, baseURL+r.URL.Path, r.Body)
		if err != nil {
			http.Error(w, fmt.Sprintf("failed to create request: %v", err), 500)
			return
		}
		req.URL.RawQuery = r.URL.RawQuery

		resp, err := oauthClient.Do(req)
		if err != nil {
			http.Error(w, err.Error(), 500)
			return
		}
		defer resp.Body.Close()

		for header, values := range resp.Header {
			for _, v := range values {
				w.Header().Add(header, v)
			}
		}

		if _, err := io.Copy(w, resp.Body); err != nil {
			http.Error(w, err.Error(), 500)
		}
	})

	log.Println("starting http server")
	if err := http.ListenAndServe(":5000", mux); err != nil {
		log.Fatalf("failed to start http server: %v\n", err)
	}
}