package auth

import (
	"encoding/json"
	"fmt"
	"net/http"
	"strings"
	"time"

	"github.com/google/go-querystring/query"
	"golang.org/x/oauth2"
)

type Token struct {
	AccessToken string    `json:"access_token"`
	ExpiresIn   int       `json:"expires_in"`
	Expiry      time.Time `json:"-"`

	// Only present when using OIDC.
	IdToken *string `json:"id_token"`

	RefreshToken string   `json:"refresh_token"`
	Scope        []string `json:"scope"`
	TokenType    string   `json:"token_type"`
}

func (t *Token) Valid() bool {
	return t.AccessToken != "" && t.Expiry.After(time.Now())
}

func (t *Token) Underlying() *oauth2.Token {
	return &oauth2.Token{
		AccessToken:  t.AccessToken,
		TokenType:    t.TokenType,
		RefreshToken: t.RefreshToken,
		Expiry:       t.Expiry,
	}
}

const TokenUrl = "https://id.twitch.tv/oauth2/token"

type GetTokenParams struct {
	ClientId     string `url:"client_id"`
	ClientSecret string `url:"client_secret"`
	Code         string `url:"code"`
	GrantType    string `url:"grant_type"`
	RedirectUri  string `url:"redirect_uri"`
}

func GetToken(params *GetTokenParams) (*Token, error) {
	v, err := query.Values(params)
	if err != nil {
		return nil, err
	}

	res, err := http.Post(TokenUrl, "application/x-www-form-urlencoded", strings.NewReader(v.Encode()))
	if err != nil {
		return nil, err
	}
	defer res.Body.Close()

	statusOK := res.StatusCode >= 200 && res.StatusCode < 300
	if !statusOK {
		return nil, fmt.Errorf("failed to get token (%d)", res.StatusCode)
	}

	var token Token
	if err := json.NewDecoder(res.Body).Decode(&token); err != nil {
		return nil, err
	}

	token.Expiry = time.Now().Add(time.Duration(token.ExpiresIn) * time.Second)

	return &token, nil
}

type TokenHandler interface {
	Handle(state string, token string)
}

type TokenHandlerFunc func(state string, token string)

var _ TokenHandler = (*TokenHandlerFunc)(nil)

func (f TokenHandlerFunc) Handle(state string, token string) {
	f(state, token)
}