package xiaomi

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

	"xiaomihome/miot"
)

// TokenResult OAuth token 交换结果
type TokenResult struct {
	AccessToken  string `json:"access_token"`
	RefreshToken string `json:"refresh_token"`
	ExpiresIn    int    `json:"expires_in"`
	UID          string `json:"uid"`
}

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

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

func generateUUID() string {
	b := make([]byte, 16)
	rand.Read(b)
	buf := make([]byte, 36)
	hex.Encode(buf[:8], b[:4])
	buf[8] = '-'
	hex.Encode(buf[9:13], b[4:6])
	buf[13] = '-'
	hex.Encode(buf[14:18], b[6:8])
	buf[18] = '-'
	hex.Encode(buf[19:23], b[8:10])
	buf[23] = '-'
	hex.Encode(buf[24:], b[10:16])
	return string(buf)
}