package seoser

import (
	"net/http"
	"net/url"
	"strconv"
	"strings"
	"videoweb/app/service/configser"

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

// ResolveSiteURL 解析对外站点根地址（无尾斜杠）。
// 优先有效正式域名；跳过占位域名后回退到当前请求 Host。
func ResolveSiteURL(c *gin.Context, cfg configser.AppConfigVM) string {
	candidates := []string{
		cfg.SeoInfo.CanonicalURL,
		cfg.ForeverURLAddr,
		cfg.NewURLAddr,
	}
	for _, raw := range candidates {
		if u := usableSiteURL(raw); u != "" {
			return u
		}
	}
	if c != nil && c.Request != nil {
		return requestOrigin(c.Request)
	}
	return ""
}

func usableSiteURL(raw string) string {
	u := sanitizeBase(raw)
	if u == "" {
		return ""
	}
	host := strings.ToLower(originHost(u))
	if isPlaceholderHost(host) {
		return ""
	}
	return u
}

func originHost(raw string) string {
	u, err := url.Parse(strings.TrimSpace(raw))
	if err != nil {
		return ""
	}
	return u.Hostname()
}

func isPlaceholderHost(host string) bool {
	host = strings.TrimSpace(strings.ToLower(host))
	switch host {
	case "", "localhost", "127.0.0.1", "0.0.0.0", "www.xx.xxx", "xx.xxx", "example.com", "www.example.com":
		return true
	}
	return strings.HasSuffix(host, ".example.com") || strings.HasSuffix(host, ".local")
}

// AbsURL 将 path 或完整 URL 转为绝对地址。
func AbsURL(siteURL, raw string) string {
	raw = strings.TrimSpace(raw)
	if raw == "" {
		if siteURL == "" {
			return "/"
		}
		return siteURL + "/"
	}
	if strings.HasPrefix(raw, "http://") || strings.HasPrefix(raw, "https://") {
		return raw
	}
	if siteURL == "" {
		if strings.HasPrefix(raw, "/") {
			return raw
		}
		return "/" + raw
	}
	if strings.HasPrefix(raw, "/") {
		return siteURL + raw
	}
	return siteURL + "/" + raw
}

// PageCanonicalURL 首页用 siteURL 根路径；其他页用 siteURL + 当前 path + query。
// siteURL 为空时回退 foreverURLAddr。
func PageCanonicalURL(siteURL, foreverURLAddr string, c *gin.Context) string {
	base := strings.TrimRight(strings.TrimSpace(siteURL), "/")
	if base == "" {
		base = strings.TrimRight(strings.TrimSpace(usableSiteURL(foreverURLAddr)), "/")
	}
	if c == nil || c.Request == nil || c.Request.URL == nil {
		return AbsURL(base, "/")
	}
	path := c.Request.URL.Path
	if path == "" || path == "/" {
		return AbsURL(base, "/")
	}
	return ensureTrailingSlash(AbsURL(base, relativeRequestURI(c.Request.URL)))
}

// CanonicalWithoutQuery 移除 canonical 中的查询参数与片段，避免参数变体形成重复 URL。
func CanonicalWithoutQuery(raw string) string {
	raw = strings.TrimSpace(raw)
	u, err := url.Parse(raw)
	if err != nil {
		return raw
	}
	u.RawQuery = ""
	u.ForceQuery = false
	u.Fragment = ""
	return u.String()
}

// ContentCanonicalURL 由实际内容生成 slug 路由。
func ContentCanonicalURL(siteURL, fallback string, data map[string]any) string {
	if detail, ok := asPlaylet(data["detail"]); ok {
		if path := playletPath("/detail", detail.Slug, detail.ID); path != "" {
			return AbsURL(siteURL, path)
		}
	} else if chapter, ok := asChapter(data["chapter"]); ok {
		playlet, _ := asPlaylet(data["playlet"])
		playletID := chapter.PlayletID
		playletSlug := ""
		if playlet != nil {
			playletID = playlet.ID
			playletSlug = playlet.Slug
		}
		path := playletPath("/play", playletSlug, playletID)
		if path == "" {
			return fallback
		}
		if chapter.ID > 0 {
			path += strconv.FormatInt(chapter.ID, 10) + "/"
		}
		return AbsURL(siteURL, path)
	}
	return ensureTrailingSlash(fallback)
}

// ensureTrailingSlash 将 HTML 页面 URL 统一为目录式尾斜杠形式，并保留查询参数。
func ensureTrailingSlash(raw string) string {
	raw = strings.TrimSpace(raw)
	u, err := url.Parse(raw)
	if err != nil {
		return raw
	}
	if u.Path == "" {
		u.Path = "/"
	}
	if u.Path != "/" && !strings.HasSuffix(u.Path, "/") {
		u.Path += "/"
	}
	return u.String()
}

func relativeRequestURI(u *url.URL) string {
	if u == nil {
		return "/"
	}
	path := u.EscapedPath()
	if path == "" {
		path = "/"
	}
	if u.RawQuery != "" {
		return path + "?" + u.RawQuery
	}
	return path
}

func sanitizeBase(raw string) string {
	raw = strings.TrimSpace(raw)
	if raw == "" {
		return ""
	}
	u, err := url.Parse(raw)
	if err != nil || u.Scheme == "" || u.Host == "" {
		if !strings.Contains(raw, "://") && strings.Contains(raw, ".") {
			return sanitizeBase("https://" + strings.TrimPrefix(raw, "/"))
		}
		return ""
	}
	if u.Scheme != "http" && u.Scheme != "https" {
		return ""
	}
	return strings.TrimRight(u.Scheme+"://"+u.Host, "/")
}

func requestOrigin(r *http.Request) string {
	if r == nil {
		return ""
	}
	proto := strings.TrimSpace(r.Header.Get("X-Forwarded-Proto"))
	if proto == "" {
		if r.TLS != nil {
			proto = "https"
		} else {
			proto = "http"
		}
	}
	if i := strings.IndexByte(proto, ','); i >= 0 {
		proto = strings.TrimSpace(proto[:i])
	}
	host := strings.TrimSpace(r.Header.Get("X-Forwarded-Host"))
	if host == "" {
		host = strings.TrimSpace(r.Host)
	}
	if i := strings.IndexByte(host, ','); i >= 0 {
		host = strings.TrimSpace(host[:i])
	}
	if host == "" {
		return ""
	}
	return strings.TrimRight(proto+"://"+host, "/")
}