package api

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

// StaticHandler serves embedded SPA files with fallback to index.html
// for all non-API routes (SPA client-side routing support).
func StaticHandler(webFS fs.FS) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		// Skip API routes — they are handled by the API router.
		if strings.HasPrefix(r.URL.Path, "/api") {
			http.NotFound(w, r)
			return
		}

		// Try to serve the exact file from the embedded FS.
		path := strings.TrimPrefix(r.URL.Path, "/")
		if path == "" {
			path = "index.html"
		}

		// Check if file exists in the embedded FS.
		if f, err := webFS.Open(path); err == nil {
			stat, statErr := f.Stat()
			f.Close()
			if statErr == nil && !stat.IsDir() {
				// Serve the actual file. Use http.ServeContent for correct MIME detection.
				file, _ := webFS.Open(path)
				defer file.Close()
				http.ServeContent(w, r, stat.Name(), stat.ModTime(), file.(io.ReadSeeker))
				return
			}
		}

		// File not found: serve index.html for SPA client-side routing.
		indexFile, _ := webFS.Open("index.html")
		if indexFile != nil {
			defer indexFile.Close()
			stat, _ := indexFile.Stat()
			http.ServeContent(w, r, "index.html", stat.ModTime(), indexFile.(io.ReadSeeker))
		}
	})
}