package token

import (
	"context"
	"encoding/json"
	"fmt"
	"net/http"
	"os"
	"time"

	"github.com/charmbracelet/log"
	"golang.org/x/oauth2"
)

// Return OAuth2 Client
func GetClient(config *oauth2.Config) *http.Client {
	// The file token.json stores the user's access and refresh tokens, and is
	// created automatically when the autorization flow completes for the first time

	tokFile := "token.json"
	tok, err := GetTokenFromFile(tokFile)
	if err != nil {
		tok = GetTokenFromWeb(config)
		SaveToken(tokFile, tok)
	}

	return config.Client(context.Background(), tok)
}

// Request a token from the web
func GetTokenFromWeb(config *oauth2.Config) *oauth2.Token {
	// Simple HTTP callback handler
	codeCh := make(chan string)
	srv := &http.Server{Addr: ":4444"}

	http.HandleFunc("/callback", func(w http.ResponseWriter, r *http.Request) {
		code := r.URL.Query().Get("code")
		fmt.Fprint(w, "Authorization successful! You can close this tab.")
		codeCh <- code
	})

	// Start in background
	go func() {
		srv.ListenAndServe()
	}()

	authURL := config.AuthCodeURL("state-token", oauth2.AccessTypeOffline, oauth2.ApprovalForce)
	log.Info("Go to the following link in your browser and then type the authorization code:")
	fmt.Println(authURL)

	// Get authCode from channel
	authCode := <-codeCh

	tok, err := config.Exchange(context.TODO(), authCode) 
	if err != nil {
		log.Fatal("Unable to retrieve token from web", "err", err)
	}

	ctxShutdown, cancel := context.WithTimeout(context.Background(), 5*time.Second)
	defer cancel()
	srv.Shutdown(ctxShutdown)

	return tok
}

// Retrieves a token from a file
func GetTokenFromFile(file string) (*oauth2.Token, error) {
	f, err := os.Open(file)
	if err != nil {
		return nil, err
	}
	defer f.Close()

	tok := &oauth2.Token{}
	err = json.NewDecoder(f).Decode(tok)
	return tok, err
}

// Saves a token to a file path
func SaveToken(path string, token *oauth2.Token) {
	log.Info("Saving credential file to", "path", path)
	f, err := os.OpenFile(path, os.O_RDWR|os.O_CREATE|os.O_TRUNC, 0600)
	if err != nil {
		log.Fatal("Unable to cache oauth token", "err", err)
	}
	defer f.Close()

	json.NewEncoder(f).Encode(token)
}