package handler

import (
	"io/fs"
	"net/http"
	"path"
	"strings"
)

// indexHandler 服务嵌入式前端首页 web/static/index.html。
func indexHandler(fsys fs.FS) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		b, err := fs.ReadFile(fsys, "index.html")
		if err != nil {
			http.Error(w, "前端页面尚未构建：请在 frontend 目录执行 pnpm build", http.StatusNotFound)
			return
		}
		w.Header().Set("Content-Type", "text/html; charset=utf-8")
		_, _ = w.Write(b)
	}
}

// mimeFallback 构建产物常见静态资源的 Content-Type 兜底表
// （mime.TypeByExtension 在部分 Windows 环境依赖系统注册表，结果不稳定）。
var mimeFallback = map[string]string{
	".html": "text/html; charset=utf-8",
	".css":  "text/css; charset=utf-8",
	".js":   "text/javascript; charset=utf-8",
	".mjs":  "text/javascript; charset=utf-8",
	".json": "application/json; charset=utf-8",
	".svg":  "image/svg+xml",
	".png":  "image/png",
	".jpg":  "image/jpeg",
	".jpeg": "image/jpeg",
	".gif":  "image/gif",
	".ico":  "image/x-icon",
	".woff": "font/woff",
	".woff2": "font/woff2",
	".ttf":  "font/ttf",
	".webp": "image/webp",
}

// assetHandler 服务 vite 构建产物 /assets/<file>。
// 前端使用 hash 路由，静态托管只需覆盖根路径与扁平的 assets 目录。
func assetHandler(fsys fs.FS) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		name := strings.TrimPrefix(r.URL.EscapedPath(), "/assets/")
		if name == "" || strings.ContainsAny(name, `/\`) || strings.Contains(name, "..") {
			http.NotFound(w, r)
			return
		}
		if _, err := fs.Stat(fsys, "assets/"+name); err != nil {
			http.NotFound(w, r)
			return
		}

		ct := mimeFallback[strings.ToLower(path.Ext(name))]
		if ct == "" {
			ct = "application/octet-stream"
		}
		w.Header().Set("Content-Type", ct)
		w.Header().Set("Cache-Control", "public, max-age=31536000, immutable") // vite 产物带内容哈希
		b, err := fs.ReadFile(fsys, "assets/"+name)
		if err != nil {
			return
		}
		_, _ = w.Write(b)
	}
}