// Package web embeds the built React SPA (web/dist, copied to
// internal/web/dist by `make web` before go build/test) and serves it
// with SPA-fallback: any non-file path resolves to index.html so
// client-side routing works.
package web

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

//go:embed all:dist
var distFS embed.FS

// Handler serves the embedded SPA with fallback to index.html for
// client-side routes (any non-file path that isn't an API route).
func Handler() (http.Handler, error) {
	sub, err := fs.Sub(distFS, "dist")
	if err != nil {
		return nil, err
	}
	fileServer := http.FileServer(http.FS(sub))
	index, err := fs.ReadFile(sub, "index.html")
	if err != nil {
		return nil, err
	}
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		// существующий файл (ассет) — отдать как есть
		p := strings.TrimPrefix(r.URL.Path, "/")
		if p != "" {
			if f, err := sub.Open(p); err == nil {
				_ = f.Close()
				fileServer.ServeHTTP(w, r)
				return
			}
		}
		// иначе — SPA index
		w.Header().Set("Content-Type", "text/html; charset=utf-8")
		_, _ = w.Write(index)
	}), nil
}