package main

import (
	"context"
	"crypto/sha256"
	"encoding/base64"
	"encoding/json"
	"fmt"
	"io"
	"log"
	"math/rand"
	"net/http"
	"net/url"
	"os"
	"strconv"
	"strings"
	"sync"
	"time"

	"github.com/99designs/keyring"
	"github.com/wailsapp/wails/v2/pkg/runtime"
)

var myAnimeListJwt MyAnimeListJWT

var myAnimeListRing, _ = keyring.Open(keyring.Config{
	ServiceName: "AniTrack",
})

var myAnimeListCtxShutdown, myAnimeListCancel = context.WithCancel(context.Background())

type CodeVerifier struct {
	Value string
}

const (
	length = 32
)

func base64URLEncode(str []byte) string {
	encoded := base64.StdEncoding.EncodeToString(str)
	encoded = strings.Replace(encoded, "+", "-", -1)
	encoded = strings.Replace(encoded, "/", "_", -1)
	encoded = strings.Replace(encoded, "=", "", -1)
	return encoded
}

func verifier() (*CodeVerifier, error) {
	r := rand.New(rand.NewSource(time.Now().UnixNano()))
	b := make([]byte, length, length)
	for i := 0; i < length; i++ {
		b[i] = byte(r.Intn(255))
	}
	return CreateCodeVerifierFromBytes(b)
}

func CreateCodeVerifierFromBytes(b []byte) (*CodeVerifier, error) {
	return &CodeVerifier{
		Value: base64URLEncode(b),
	}, nil
}

func (v *CodeVerifier) CodeChallengeS256() string {
	h := sha256.New()
	h.Write([]byte(v.Value))
	return base64URLEncode(h.Sum(nil))
}

func (a *App) CheckIfMyAnimeListLoggedIn() bool {
	if (MyAnimeListJWT{} == myAnimeListJwt) {
		tokenType, err := myAnimeListRing.Get("MyAnimeListTokenType")
		expiresIn, err := myAnimeListRing.Get("MyAnimeListExpiresIn")
		accessToken, err := myAnimeListRing.Get("MyAnimeListAccessToken")
		refreshToken, err := myAnimeListRing.Get("MyAnimeListRefreshToken")
		if err != nil || len(accessToken.Data) == 0 {
			return false
		} else {
			myAnimeListJwt.TokenType = string(tokenType.Data)
			myAnimeListJwt.ExpiresIn, err = strconv.Atoi(string(expiresIn.Data))
			if err != nil {
				fmt.Println("unable to convert string to int")
			}
			myAnimeListJwt.AccessToken = string(accessToken.Data)
			myAnimeListJwt.RefreshToken = string(refreshToken.Data)
			return true
		}
	} else {
		return true
	}
}

func (a *App) MyAnimeListLogin() {
	if a.CheckIfMyAnimeListLoggedIn() == false {
		tokenType, err := myAnimeListRing.Get("MyAnimeListTokenType")
		expiresIn, err := myAnimeListRing.Get("MyAnimeListExpiresIn")
		accessToken, err := myAnimeListRing.Get("MyAnimeListAccessToken")
		refreshToken, err := myAnimeListRing.Get("MyAnimeListRefreshToken")
		if err != nil || len(accessToken.Data) == 0 {
			verifier, _ := verifier()
			getMyAnimeListCodeUrl := "https://myanimelist.net/v1/oauth2/authorize?response_type=code&client_id=" + os.Getenv("MAL_CLIENT_ID") + "&redirect_uri=" + os.Getenv("MAL_CALLBACK_URI") + "&code_challenge=" + verifier.Value + "&code_challenge_method=plain"
			runtime.BrowserOpenURL(a.ctx, getMyAnimeListCodeUrl)
			serverDone := &sync.WaitGroup{}
			serverDone.Add(1)
			handleMyAnimeListCallback(serverDone, verifier)
			serverDone.Wait()
		} else {
			myAnimeListJwt.TokenType = string(tokenType.Data)
			myAnimeListJwt.ExpiresIn, err = strconv.Atoi(string(expiresIn.Data))
			if err != nil {
				fmt.Println("unable to convert string to int in Login function")
			}
			myAnimeListJwt.AccessToken = string(accessToken.Data)
			myAnimeListJwt.RefreshToken = string(refreshToken.Data)
		}
	}
}

func handleMyAnimeListCallback(wg *sync.WaitGroup, verifier *CodeVerifier) {
	srv := &http.Server{Addr: ":6734"}
	http.HandleFunc("/callback", func(w http.ResponseWriter, r *http.Request) {
		select {
		case <-myAnimeListCtxShutdown.Done():
			fmt.Println("Shutting down...")
			return
		default:
		}
		content := r.FormValue("code")

		if content != "" {
			myAnimeListJwt = getMyAnimeListAuthorizationToken(content, verifier)
			_ = myAnimeListRing.Set(keyring.Item{
				Key:  "MyAnimeListTokenType",
				Data: []byte(myAnimeListJwt.TokenType),
			})
			_ = myAnimeListRing.Set(keyring.Item{
				Key:  "MyAnimeListExpiresIn",
				Data: []byte(strconv.Itoa(myAnimeListJwt.ExpiresIn)),
			})
			_ = myAnimeListRing.Set(keyring.Item{
				Key:  "MyAnimeListAccessToken",
				Data: []byte(myAnimeListJwt.AccessToken),
			})
			_ = myAnimeListRing.Set(keyring.Item{
				Key:  "MyAnimeListRefreshToken",
				Data: []byte(myAnimeListJwt.RefreshToken),
			})
			fmt.Println("Shutting down...")
			myAnimeListCancel()
			err := srv.Shutdown(context.Background())
			if err != nil {
				log.Println("server.Shutdown:", err)
			}
		} else {
			_, err := fmt.Fprintf(w, "Getting code failed.")
			if err != nil {
				return
			}
		}
	})

	go func() {
		defer wg.Done()
		if err := srv.ListenAndServe(); err != nil && err != http.ErrServerClosed {
			log.Fatalf("listen: %s\n", err)
		}
		fmt.Println("Shutting down...")
	}()
}

func getMyAnimeListAuthorizationToken(content string, verifier *CodeVerifier) MyAnimeListJWT {
	dataForURLs := struct {
		GrantType    string        `json:"grant_type"`
		ClientID     string        `json:"client_id"`
		ClientSecret string        `json:"client_secret"`
		RedirectURI  string        `json:"redirect_uri"`
		Code         string        `json:"code"`
		CodeVerifier *CodeVerifier `json:"code_verifier"`
	}{
		GrantType:    "authorization_code",
		ClientID:     os.Getenv("MAL_CLIENT_ID"),
		ClientSecret: os.Getenv("MAL_CLIENT_SECRET"),
		RedirectURI:  os.Getenv("MAL_CALLBACK_URI"),
		Code:         content,
		CodeVerifier: verifier,
	}

	data := url.Values{}
	data.Set("grant_type", dataForURLs.GrantType)
	data.Set("client_id", dataForURLs.ClientID)
	data.Set("client_secret", dataForURLs.ClientSecret)
	data.Set("redirect_uri", dataForURLs.RedirectURI)
	data.Set("code", dataForURLs.Code)
	data.Set("code_verifier", dataForURLs.CodeVerifier.Value)

	response, err := http.NewRequest("POST", "https://myanimelist.net/v1/oauth2/token", strings.NewReader(data.Encode()))
	if err != nil {
		log.Printf("Failed at response, %s\n", err)
	}
	response.Header.Add("Content-Type", "application/x-www-form-urlencoded")

	client := &http.Client{}
	res, reserr := client.Do(response)
	if reserr != nil {
		log.Printf("Failed at res, %s\n", err)
	}

	defer res.Body.Close()

	returnedBody, err := io.ReadAll(res.Body)

	var post MyAnimeListJWT
	err = json.Unmarshal(returnedBody, &post)
	if err != nil {
		log.Printf("Failed at unmarshal, %s\n", err)
	}

	return post
}

func (a *App) GetMyAnimeListLoggedInUser() MyAnimeListUser {
	a.MyAnimeListLogin()

	client := &http.Client{}

	req, _ := http.NewRequest("GET", "https://api.myanimelist.net/v2/users/@me?fields=anime_statistics", nil)

	req.Header.Add("Content-Type", "application/json")
	req.Header.Add("Authorization", "Bearer "+myAnimeListJwt.AccessToken)
	req.Header.Add("myAnimeList-api-key", os.Getenv("MAL_CLIENT_ID"))

	response, err := client.Do(req)

	if err != nil {
		log.Printf("Failed at request, %s\n", err)
		return MyAnimeListUser{}
	}

	defer response.Body.Close()

	var user MyAnimeListUser

	respBody, _ := io.ReadAll(response.Body)

	err = json.Unmarshal(respBody, &user)
	if err != nil {
		log.Printf("Failed at unmarshal, %s\n", err)
	}

	return user
}