package xiaomi

import (
	"context"
	"crypto/rand"
	"encoding/hex"
	"fmt"
	"time"

	"git.zeroonesoft.cn/golib/xiaomihome/miot"
)

// TokenResult OAuth token 交换/刷新结果
type TokenResult struct {
	AccessToken  string `json:"access_token"`
	RefreshToken string `json:"refresh_token"`
	ExpiresIn    int32  `json:"expires_in"`
	ExpiresTS    int64  `json:"expires_ts"`
	UID          string `json:"uid"`
}

// AuthURL 生成小米 OAuth 授权页面 URL。
func AuthURL(cfg Config) string {
	uuid := cfg.UUID
	if uuid == "" {
		uuid = generateUUID()
	}
	redirectURL := cfg.RedirectURL
	if redirectURL == "" {
		redirectURL = miot.OAUTH_REDIRECT_URL
	}
	oa := miot.NewMIoTOauthClient(miot.OAUTH2_CLIENT_ID, redirectURL, "cn", uuid)
	return oa.GenAuthURL("", "", nil, false)
}

// ExchangeCode 用 authorization code 交换 access token。
func ExchangeCode(ctx context.Context, cfg Config, code string) (*TokenResult, error) {
	uuid := cfg.UUID
	if uuid == "" {
		uuid = generateUUID()
	}
	redirectURL := cfg.RedirectURL
	if redirectURL == "" {
		redirectURL = miot.OAUTH_REDIRECT_URL
	}
	oa := miot.NewMIoTOauthClient(miot.OAUTH2_CLIENT_ID, redirectURL, "cn", uuid)
	result, err := oa.GetAccessToken(code)
	if err != nil {
		return nil, fmt.Errorf("xiaomi: exchange token: %w", err)
	}
	expiresIn := intVal(result, "expires_in")
	return &TokenResult{
		AccessToken:  strVal(result, "access_token"),
		RefreshToken: strVal(result, "refresh_token"),
		ExpiresIn:    int32(expiresIn),
		ExpiresTS:    time.Now().Unix() + int64(expiresIn),
		UID:          strVal(result, "uid"),
	}, nil
}

func generateUUID() string {
	b := make([]byte, 16)
	rand.Read(b)
	return hex.EncodeToString(b)
}