package router

import (
	"html"
	"net/http"
	"net/url"
	"os"
	"path/filepath"
	"regexp"
	"strings"

	"github.com/gin-gonic/gin"
)

const sitemapDir = "./templates/page/sitemaps"

var sitemapLocPattern = regexp.MustCompile(`<loc>([^<]+)</loc>`)

// registerSitemapRoutes 暴露 hgdj_server app 生成的 sitemap 索引及分片文件。
func registerSitemapRoutes(r *gin.Engine) {
	r.StaticFile("/sitemap.xml", filepath.Join(sitemapDir, "sitemap.xml"))
	r.GET("/sitemaps/:name", serveSitemapShard)
}

func serveSitemapShard(c *gin.Context) {
	name := c.Param("name")
	if !isValidSitemapShardName(name) {
		renderNotFound(c)
		return
	}
	raw, err := os.ReadFile(filepath.Join(sitemapDir, name))
	if err != nil {
		renderNotFound(c)
		return
	}
	c.Data(http.StatusOK, "application/xml; charset=utf-8", normalizeSitemapPageURLs(raw))
}

// normalizeSitemapPageURLs 让运行时生成的旧 sitemap 与当前 canonical 路由保持一致。
// sitemap 索引和静态文件地址不经过这里，仍保留文件型 URL（无尾斜杠）。
func normalizeSitemapPageURLs(raw []byte) []byte {
	return sitemapLocPattern.ReplaceAllFunc(raw, func(match []byte) []byte {
		parts := sitemapLocPattern.FindSubmatch(match)
		if len(parts) != 2 {
			return match
		}
		loc := html.UnescapeString(strings.TrimSpace(string(parts[1])))
		u, err := url.Parse(loc)
		if err != nil || u.Path == "" {
			return match
		}
		u.Path = canonicalSitemapPagePath(u.Path)
		return []byte("<loc>" + html.EscapeString(u.String()) + "</loc>")
	})
}

func canonicalSitemapPagePath(path string) string {
	switch {
	case path == "/more":
		path = "/topic"
	case strings.HasPrefix(path, "/more/"):
		path = "/topic/" + strings.TrimPrefix(path, "/more/")
	case path == "/tag-list":
		path = "/tag"
	case strings.HasPrefix(path, "/tag-list/"):
		path = "/tag/" + strings.TrimPrefix(path, "/tag-list/")
	}
	if path != "/" && !strings.HasSuffix(path, "/") {
		path += "/"
	}
	return path
}

// isValidSitemapShardName 校验分片文件名，防止路径遍历。
// 合法示例：sitemap-pages.xml、sitemap-playletdetail-0.xml
func isValidSitemapShardName(name string) bool {
	if !strings.HasPrefix(name, "sitemap-") || !strings.HasSuffix(name, ".xml") {
		return false
	}
	base := strings.TrimSuffix(name, ".xml")
	if len(base) <= len("sitemap-") {
		return false
	}
	for _, ch := range base[len("sitemap-"):] {
		if !((ch >= 'a' && ch <= 'z') || (ch >= '0' && ch <= '9') || ch == '-') {
			return false
		}
	}
	return true
}