package fadada

import (
	"fmt"
	"strconv"
	"sync"
	"time"
)

// tokenCache accessToken 内存缓存（官方有效期约 2 小时）
type tokenCache struct {
	mu        sync.Mutex
	token     string
	expiresAt time.Time
}

func (c *tokenCache) get() (string, bool) {
	c.mu.Lock()
	defer c.mu.Unlock()
	if c.token == "" || time.Now().After(c.expiresAt) {
		return "", false
	}
	return c.token, true
}

func (c *tokenCache) set(token string, ttl time.Duration) {
	c.mu.Lock()
	defer c.mu.Unlock()
	c.token = token
	c.expiresAt = time.Now().Add(ttl)
}

// ensureAccessToken 获取可用 accessToken，过期前自动刷新
func (c *Client) ensureAccessToken() (string, error) {
	if token, ok := c.tokenCache.get(); ok {
		return token, nil
	}

	c.tokenMu.Lock()
	defer c.tokenMu.Unlock()

	if token, ok := c.tokenCache.get(); ok {
		return token, nil
	}

	res, err := c.http.PostToken(pathGetAccessToken)
	if err != nil {
		return "", err
	}
	if res.Code != "" && res.Code != successCode {
		return "", fmt.Errorf("获取法大大 accessToken 失败: code=%s msg=%s requestId=%s", res.Code, res.Msg, res.RequestID)
	}

	var data accessTokenData
	if err := decodeData(res.Data, &data); err != nil {
		return "", fmt.Errorf("解析 accessToken 失败: %w", err)
	}
	if data.AccessToken == "" {
		return "", fmt.Errorf("获取法大大 accessToken 失败: 响应为空 code=%s msg=%s", res.Code, res.Msg)
	}

	ttl := 2*time.Hour - 5*time.Minute
	if expiresIn, err := strconv.Atoi(data.ExpiresIn); err == nil && expiresIn > 0 {
		ttl = time.Duration(expiresIn)*time.Second - 5*time.Minute
		if ttl < time.Minute {
			ttl = time.Minute
		}
	}
	c.tokenCache.set(data.AccessToken, ttl)
	return data.AccessToken, nil
}