package main

import (
	"encoding/base64"
	"errors"
	"fmt"
	"io"
	"log/slog"
	"net/http"
	"net/url"
	"os"
	"strings"

	"resty.dev/v3"
)

type loginCredentials struct {
	user     string
	password string
}

// getLoginCookies 优先读取数据库中的 Cookie，未命中时执行登录并缓存新 Cookie。
func getLoginCookies(db *DB, client *resty.Client) ([]*http.Cookie, error) {
	cookies, err := db.GetCookie()
	if err == nil {
		return cookies, nil
	}
	if !errors.Is(err, errCookieNotFound) {
		return nil, err
	}

	credentials, err := loadLoginCredentials()
	if err != nil {
		return nil, err
	}

	cookies, err = login423Down(client, credentials)
	if err != nil {
		return nil, err
	}
	if len(cookies) == 0 {
		return cookies, nil
	}

	if err := db.SetCookie(cookies); err != nil {
		slog.Warn("failed to cache login cookies", slog.String("error", err.Error()))
	}

	return cookies, nil
}

// loadLoginCredentials 从环境变量读取 423down 登录账号。
func loadLoginCredentials() (loginCredentials, error) {
	credentials := loginCredentials{
		user:     strings.TrimSpace(os.Getenv(loginUserEnv)),
		password: os.Getenv(loginPasswordEnv),
	}
	if credentials.user == "" || credentials.password == "" {
		return loginCredentials{}, fmt.Errorf("missing login credentials: set %s and %s", loginUserEnv, loginPasswordEnv)
	}

	return credentials, nil
}

// login423Down 提交 WordPress 登录表单并返回登录态 Cookie。
func login423Down(client *resty.Client, credentials loginCredentials) ([]*http.Cookie, error) {
	form := url.Values{}
	form.Add("log", credentials.user)
	form.Add("pwd", credentials.password)
	form.Add("rememberme", "forever")
	form.Add("wp-submit", "登录")
	form.Add("testcookie", "1")

	resp, err := client.R().
		SetHeader("Content-Type", "application/x-www-form-urlencoded").
		SetBody(form.Encode()).
		Post(loginURL)
	if err != nil {
		return nil, fmt.Errorf("login request failed: %w", err)
	}
	defer func() { _ = resp.Body.Close() }()

	cookies := resp.Cookies()
	if hasWordPressLoggedInCookie(cookies) {
		return cookies, nil
	}

	body, err := io.ReadAll(resp.Body)
	if err != nil {
		return nil, fmt.Errorf("read login response failed: %w", err)
	}
	if canVisitLimitedPage(body) {
		return cookies, nil
	}

	return nil, errors.New("failed to get login cookies")
}

// hasWordPressLoggedInCookie 判断响应中是否包含 WordPress 登录态 Cookie。
func hasWordPressLoggedInCookie(cookies []*http.Cookie) bool {
	for _, cookie := range cookies {
		if strings.Contains(cookie.Name, "wordpress_logged_in") {
			return true
		}
	}

	return false
}

// canVisitLimitedPage 兼容源站可能返回明文或 base64 编码页面的情况。
func canVisitLimitedPage(body []byte) bool {
	if strings.Contains(string(body), "个人中心") {
		return true
	}

	decoded, err := base64.StdEncoding.DecodeString(string(body))
	if err != nil {
		return false
	}

	return strings.Contains(string(decoded), "个人中心")
}