package server

import (
	"errors"
	"io/fs"
	"mime"
	"net/http"
	"os"
	"path"
	"path/filepath"
	"strings"
)

// staticHandler serves the built web client with SPA fallback: unknown paths
// return index.html so client-side routes survive a page reload.
type staticHandler struct {
	root string
}

func newStaticHandler(root string) *staticHandler {
	return &staticHandler{root: root}
}

func (h *staticHandler) serve(w http.ResponseWriter, r *http.Request) {
	cleaned := path.Clean("/" + r.URL.Path)
	rel := strings.TrimPrefix(cleaned, "/")
	if rel == "" {
		h.serveIndex(w, r)
		return
	}

	info, err := fs.Stat(os.DirFS(h.root), rel)
	if err != nil || info.IsDir() {
		if err != nil && !errors.Is(err, fs.ErrNotExist) {
			http.Error(w, "internal error", http.StatusInternalServerError)
			return
		}
		h.serveIndex(w, r)
		return
	}

	if contentType := mime.TypeByExtension(filepath.Ext(rel)); contentType != "" {
		w.Header().Set("Content-Type", contentType)
	}
	if strings.HasPrefix(rel, "assets/") {
		w.Header().Set("Cache-Control", "public, max-age=31536000, immutable")
	} else {
		w.Header().Set("Cache-Control", "no-cache")
	}
	http.ServeFile(w, r, filepath.Join(h.root, filepath.FromSlash(rel)))
}

func (h *staticHandler) serveIndex(w http.ResponseWriter, r *http.Request) {
	index := filepath.Join(h.root, "index.html")
	if _, err := os.Stat(index); err != nil {
		writeClientNotBuilt(w)
		return
	}
	w.Header().Set("Content-Type", "text/html; charset=utf-8")
	w.Header().Set("Cache-Control", "no-cache")
	http.ServeFile(w, r, index)
}

func writeClientNotBuilt(w http.ResponseWriter) {
	w.Header().Set("Content-Type", "text/plain; charset=utf-8")
	w.WriteHeader(http.StatusServiceUnavailable)
	_, _ = w.Write([]byte("glchat: web client bundle is not present in this image\n"))
}