package main

import (
	"net/http"
	"os"
	"path"
	"path/filepath"
	"strings"
)

func (a *app) handler() http.Handler {
	api := a.routes()
	webDir := strings.TrimSpace(a.cfg.WebDir)
	if webDir == "" {
		return api
	}

	indexPath := filepath.Join(webDir, "index.html")

	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		if r.URL.Path == "/health" {
			a.healthHandler(w, r)
			return
		}

		if isBackendPath(r.URL.Path) {
			api.ServeHTTP(w, r)
			return
		}

		cleanPath := path.Clean("/" + r.URL.Path)
		relativePath := strings.TrimPrefix(cleanPath, "/")
		if relativePath != "" {
			candidate := filepath.Join(webDir, filepath.FromSlash(relativePath))
			if info, err := os.Stat(candidate); err == nil && !info.IsDir() {
				http.ServeFile(w, r, candidate)
				return
			}

			// Missing static assets should be real 404s rather than the SPA shell.
			if filepath.Ext(relativePath) != "" {
				http.NotFound(w, r)
				return
			}
		}

		if _, err := os.Stat(indexPath); err != nil {
			api.ServeHTTP(w, r)
			return
		}
		http.ServeFile(w, r, indexPath)
	})
}

func isBackendPath(requestPath string) bool {
	switch {
	case requestPath == "/api", strings.HasPrefix(requestPath, "/api/"):
		return true
	case requestPath == "/auth", strings.HasPrefix(requestPath, "/auth/"):
		return true
	case requestPath == "/.well-known", strings.HasPrefix(requestPath, "/.well-known/"):
		return true
	case requestPath == "/sitemap.xml", requestPath == "/robots.txt":
		return true
	default:
		return false
	}
}