package server

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

//go:embed ui-dist/*
var uiDist embed.FS

type uiRenderer struct {
	fsys fs.FS
}

// newUIRenderer loads the embedded UI bundle using the default dist directory.
func newUIRenderer() *uiRenderer {
	return newUIRendererFromFS(uiDist, "ui-dist")
}

// newUIRendererFromFS builds a renderer from an arbitrary filesystem root.
func newUIRendererFromFS(root fs.FS, dir string) *uiRenderer {
	sub, err := fs.Sub(root, dir)
	if err != nil {
		return &uiRenderer{}
	}
	return &uiRenderer{fsys: sub}
}

// ServeIndex writes the SPA entrypoint so deep links can hydrate client-side routes.
func (u *uiRenderer) ServeIndex(w http.ResponseWriter, _ *http.Request) error {
	if u.fsys == nil {
		return fmt.Errorf("UI assets are not available")
	}
	body, err := fs.ReadFile(u.fsys, "index.html")
	if err != nil {
		return fmt.Errorf("read index: %w", err)
	}
	w.Header().Set("Content-Type", "text/html; charset=utf-8")
	w.Header().Set("Cache-Control", "no-store")
	_, _ = w.Write(body)
	return nil
}

// ServeAsset serves hashed static assets when the request path matches a built file.
func (u *uiRenderer) ServeAsset(w http.ResponseWriter, r *http.Request) bool {
	if u.fsys == nil {
		return false
	}
	if r.Method != http.MethodGet && r.Method != http.MethodHead {
		return false
	}

	requestPath := strings.TrimPrefix(r.URL.Path, "/")
	if requestPath == "" || requestPath == "." {
		return false
	}
	if strings.HasPrefix(requestPath, "v1/") {
		return false
	}
	cleaned := path.Clean(requestPath)
	if cleaned == "." || strings.HasPrefix(cleaned, "../") {
		return false
	}
	if strings.HasSuffix(requestPath, "/") || strings.HasSuffix(cleaned, "/") {
		return false
	}
	if _, err := fs.Stat(u.fsys, cleaned); err != nil {
		return false
	}

	http.FileServer(http.FS(u.fsys)).ServeHTTP(w, r)
	return true
}