package rss

import (
	"crypto/md5"
	"encoding/xml"
	"fmt"
	"io"
	"net/http"
	"sort"
	"time"
)

func CheckRssFeed(feedURL string) error {
	//确认返回头
	resp, err := http.Head(feedURL)
	if err != nil {
		return err
	}
	if resp.StatusCode != 200 {
		return fmt.Errorf("RSS源无效: %d", resp.StatusCode)
	}
	if resp.Header.Get("Content-Type") != "application/rss+xml" {
		return fmt.Errorf("RSS源无效: %s", resp.Header.Get("Content-Type"))
	}
	return nil
}

func ParseRssFeed(feedURL string) ([]RssItem, error) {
	//确认大小
	resp, err := http.Head(feedURL)
	if err != nil {
		return nil, err
	}
	if resp.StatusCode != 200 {
		return nil, fmt.Errorf("RSS源无效: %d", resp.StatusCode)
	}
	if resp.ContentLength == 0 || resp.ContentLength > 1024*1024*10 {
		return nil, fmt.Errorf("RSS源的大小为%d,超出限制", resp.ContentLength)
	}

	//获取rss数据
	resp, err = http.Get(feedURL)
	if err != nil {
		return nil, err
	}
	defer resp.Body.Close()

	//解析rss数据
	var rssFeed RSSFeed
	decoder := xml.NewDecoder(resp.Body)
	decoder.CharsetReader = func(charset string, input io.Reader) (io.Reader, error) {
		// 处理不同的字符编码
		switch charset {
		case "GB2312", "GBK", "GB18030":
			// 如果需要处理中文编码，可以在这里添加转换逻辑
			return input, nil
		default:
			return input, nil
		}
	}

	if err := decoder.Decode(&rssFeed); err != nil {
		return nil, fmt.Errorf("解析RSS数据失败: %v", err)
	}

	// 转换为RssItem数组
	var items []RssItem
	for _, item := range rssFeed.Channel.Items {
		rssItem := RssItem{
			Title:       item.Title,
			Link:        item.Link,
			Description: item.Description,
			GUID:        item.GUID,
			Author:      item.Author,
			Category:    item.Category,
		}

		// 解析发布时间
		if item.PubDate != "" {
			// 尝试多种时间格式
			timeFormats := []string{
				time.RFC1123,                // "Mon, 02 Jan 2006 15:04:05 MST"
				time.RFC1123Z,               // "Mon, 02 Jan 2006 15:04:05 -0700"
				time.RFC822,                 // "02 Jan 06 15:04 MST"
				time.RFC822Z,                // "02 Jan 06 15:04 -0700"
				"2006-01-02T15:04:05Z07:00", // ISO 8601
				"2006-01-02 15:04:05",       // 简单格式
			}

			for _, format := range timeFormats {
				if parsedTime, err := time.Parse(format, item.PubDate); err == nil {
					rssItem.PubDate = parsedTime
					break
				}
			}
		}

		// 生成内容哈希值
		content := fmt.Sprintf("%s%s%s", item.Title, item.Link, item.Description)
		hash := md5.Sum([]byte(content))
		rssItem.Hash = fmt.Sprintf("%x", hash)

		items = append(items, rssItem)
	}
	//按时间降序排序
	sort.Slice(items, func(i, j int) bool {
		return items[i].PubDate.Before(items[j].PubDate)
	})

	return items, nil
}