package providers

import (
	"context"
	"crypto/rand"
	"encoding/base64"
	"encoding/json"
	"fmt"
	"net/http"
	"net/url"
	"time"
)

// WeiboProvider 微博OAuth提供者
type WeiboProvider struct {
	AppKey      string
	AppSecret   string
	RedirectURI string
}

// WeiboAuthURLResponse 微博授权URL响应
type WeiboAuthURLResponse struct {
	URL      string `json:"url"`
	State    string `json:"state"`
	Redirect string `json:"redirect,omitempty"`
}

// WeiboTokenResponse 微博Token响应
type WeiboTokenResponse struct {
	AccessToken string `json:"access_token"`
	ExpiresIn   int    `json:"expires_in"`
	RemindIn    string `json:"remind_in"`
	UID         string `json:"uid"`
}

// WeiboUserInfo 微博用户信息
type WeiboUserInfo struct {
	ID              int64  `json:"id"`
	IDStr           string `json:"idstr"`
	ScreenName      string `json:"screen_name"`
	Name            string `json:"name"`
	Province        string `json:"province"`
	City            string `json:"city"`
	Location        string `json:"location"`
	Description     string `json:"description"`
	URL             string `json:"url"`
	ProfileImageURL string `json:"profile_image_url"`
	Gender          string `json:"gender"` // m:男, f:女, n:未知
	FollowersCount  int    `json:"followers_count"`
	FriendsCount    int    `json:"friends_count"`
	StatusesCount   int    `json:"statuses_count"`
}

// NewWeiboProvider 创建微博OAuth提供者
func NewWeiboProvider(appKey, appSecret, redirectURI string) *WeiboProvider {
	return &WeiboProvider{
		AppKey:      appKey,
		AppSecret:   appSecret,
		RedirectURI: redirectURI,
	}
}

// GenerateState 生成随机状态码
func (w *WeiboProvider) GenerateState() (string, error) {
	b := make([]byte, 32)
	_, err := rand.Read(b)
	if err != nil {
		return "", err
	}
	return base64.URLEncoding.EncodeToString(b), nil
}

// GetAuthURL 获取微博授权URL
func (w *WeiboProvider) GetAuthURL(state string) (*WeiboAuthURLResponse, error) {
	authURL := fmt.Sprintf(
		"https://api.weibo.com/oauth2/authorize?client_id=%s&redirect_uri=%s&response_type=code&state=%s",
		w.AppKey,
		url.QueryEscape(w.RedirectURI),
		state,
	)

	return &WeiboAuthURLResponse{
		URL:      authURL,
		State:    state,
		Redirect: w.RedirectURI,
	}, nil
}

// ExchangeCode 用授权码换取访问令牌
func (w *WeiboProvider) ExchangeCode(ctx context.Context, code string) (*WeiboTokenResponse, error) {
	tokenURL := "https://api.weibo.com/oauth2/access_token"

	data := url.Values{}
	data.Set("client_id", w.AppKey)
	data.Set("client_secret", w.AppSecret)
	data.Set("grant_type", "authorization_code")
	data.Set("code", code)
	data.Set("redirect_uri", w.RedirectURI)

	client := &http.Client{Timeout: 10 * time.Second}
	resp, err := postFormWithContext(ctx, client, tokenURL, data)
	if err != nil {
		return nil, fmt.Errorf("request failed: %w", err)
	}
	defer resp.Body.Close()

	body, err := readOAuthResponseBody(resp)
	if err != nil {
		return nil, fmt.Errorf("read response failed: %w", err)
	}

	var tokenResp WeiboTokenResponse
	if err := json.Unmarshal(body, &tokenResp); err != nil {
		return nil, fmt.Errorf("parse token response failed: %w", err)
	}

	return &tokenResp, nil
}

// GetUserInfo 获取微博用户信息
func (w *WeiboProvider) GetUserInfo(ctx context.Context, accessToken, uid string) (*WeiboUserInfo, error) {
	userInfoURL := fmt.Sprintf(
		"https://api.weibo.com/2/users/show.json?access_token=%s&uid=%s",
		accessToken,
		uid,
	)

	req, err := http.NewRequestWithContext(ctx, "GET", userInfoURL, nil)
	if err != nil {
		return nil, fmt.Errorf("create request failed: %w", err)
	}

	client := &http.Client{Timeout: 10 * time.Second}
	resp, err := client.Do(req)
	if err != nil {
		return nil, fmt.Errorf("request failed: %w", err)
	}
	defer resp.Body.Close()

	body, err := readOAuthResponseBody(resp)
	if err != nil {
		return nil, fmt.Errorf("read response failed: %w", err)
	}

	// 微博错误响应
	var errResp struct {
		Error     int    `json:"error"`
		ErrorCode int    `json:"error_code"`
		Request   string `json:"request"`
	}
	if err := json.Unmarshal(body, &errResp); err == nil && errResp.Error != 0 {
		return nil, fmt.Errorf("weibo api error: code=%d", errResp.ErrorCode)
	}

	var userInfo WeiboUserInfo
	if err := json.Unmarshal(body, &userInfo); err != nil {
		return nil, fmt.Errorf("parse user info failed: %w", err)
	}

	return &userInfo, nil
}

// ValidateToken 验证访问令牌是否有效
func (w *WeiboProvider) ValidateToken(ctx context.Context, accessToken string) (bool, error) {
	// 微博没有专门的token验证接口，通过获取API token信息来验证
	tokenInfoURL := fmt.Sprintf("https://api.weibo.com/oauth2/get_token_info?access_token=%s", accessToken)

	req, err := http.NewRequestWithContext(ctx, "GET", tokenInfoURL, nil)
	if err != nil {
		return false, fmt.Errorf("create request failed: %w", err)
	}

	client := &http.Client{Timeout: 10 * time.Second}
	resp, err := client.Do(req)
	if err != nil {
		return false, fmt.Errorf("request failed: %w", err)
	}
	defer resp.Body.Close()

	body, err := readOAuthResponseBody(resp)
	if err != nil {
		return false, fmt.Errorf("read response failed: %w", err)
	}

	var result map[string]interface{}
	if err := json.Unmarshal(body, &result); err != nil {
		return false, fmt.Errorf("parse response failed: %w", err)
	}

	// 如果返回了错误，说明token无效
	if _, ok := result["error"]; ok {
		return false, nil
	}

	// 如果有expire_in字段，说明token有效
	if _, ok := result["expire_in"]; ok {
		return true, nil
	}

	return false, nil
}