// Package webserver implements the MCR web UI server.
//
// It serves HTML pages rendered from Go templates with htmx for
// interactive elements. All data is fetched via gRPC from the main
// mcrsrv API server. Authentication is handled via MCIAS, with session
// tokens stored in secure HttpOnly cookies.
package webserver

import (
	"io/fs"
	"log"
	"net/http"

	"github.com/go-chi/chi/v5"
	"github.com/go-chi/chi/v5/middleware"

	mcrv1 "git.wntrmute.dev/mc/mcr/gen/mcr/v1"
	"git.wntrmute.dev/mc/mcr/web"
)

// LoginFunc authenticates a user and returns a bearer token.
type LoginFunc func(username, password string) (token string, expiresIn int, err error)

// ValidateFunc validates a bearer token and returns the user's roles.
type ValidateFunc func(token string) (roles []string, err error)

// Server is the MCR web UI server.
type Server struct {
	router     chi.Router
	templates  *templateSet
	registry   mcrv1.RegistryServiceClient
	policy     mcrv1.PolicyServiceClient
	audit      mcrv1.AuditServiceClient
	admin      mcrv1.AdminServiceClient
	loginFn    LoginFunc
	validateFn ValidateFunc
	csrfKey    []byte // 32-byte key for HMAC signing
}

// New creates a new web UI server with the given gRPC clients and login function.
func New(
	registry mcrv1.RegistryServiceClient,
	policy mcrv1.PolicyServiceClient,
	audit mcrv1.AuditServiceClient,
	admin mcrv1.AdminServiceClient,
	loginFn LoginFunc,
	validateFn ValidateFunc,
	csrfKey []byte,
) (*Server, error) {
	tmpl, err := loadTemplates()
	if err != nil {
		return nil, err
	}

	s := &Server{
		templates:  tmpl,
		registry:   registry,
		policy:     policy,
		audit:      audit,
		admin:      admin,
		loginFn:    loginFn,
		validateFn: validateFn,
		csrfKey:    csrfKey,
	}

	s.router = s.buildRouter()
	return s, nil
}

// Handler returns the http.Handler for the server.
func (s *Server) Handler() http.Handler {
	return s.router
}

// buildRouter sets up the chi router with all routes and middleware.
func (s *Server) buildRouter() chi.Router {
	r := chi.NewRouter()

	// Global middleware.
	r.Use(middleware.Recoverer)
	r.Use(middleware.RequestID)
	r.Use(middleware.RealIP)

	// Static files (no auth required).
	staticFS, err := fs.Sub(web.Content, "static")
	if err != nil {
		log.Fatalf("webserver: failed to create static sub-filesystem: %v", err)
	}
	r.Handle("/static/*", http.StripPrefix("/static/", http.FileServer(http.FS(staticFS))))

	// Public routes (no session required).
	r.Get("/login", s.handleLoginPage)
	r.Post("/login", s.handleLoginSubmit)
	r.Get("/logout", s.handleLogout)

	// Protected routes (session required).
	r.Group(func(r chi.Router) {
		r.Use(s.sessionMiddleware)

		r.Get("/", s.handleDashboard)

		// Repository routes — name may contain slashes.
		r.Get("/repositories", s.handleRepositories)
		r.Get("/repositories/*", s.handleRepositoryOrManifest)

		// Policy routes (admin — gRPC interceptors enforce this).
		r.Get("/policies", s.handlePolicies)
		r.Post("/policies", s.handleCreatePolicy)
		r.Post("/policies/{id}/toggle", s.handleTogglePolicy)
		r.Post("/policies/{id}/delete", s.handleDeletePolicy)

		// Audit routes (admin — gRPC interceptors enforce this).
		r.Get("/audit", s.handleAudit)
	})

	return r
}

// handleRepositoryOrManifest dispatches between repository detail and
// manifest detail based on the URL path. This is necessary because
// repository names can contain slashes.
func (s *Server) handleRepositoryOrManifest(w http.ResponseWriter, r *http.Request) {
	path := r.URL.Path
	if idx := lastIndex(path, "/manifests/"); idx >= 0 {
		s.handleManifestDetail(w, r)
		return
	}
	s.handleRepositoryDetail(w, r)
}

// lastIndex returns the index of the last occurrence of sep in s, or -1.
func lastIndex(s, sep string) int {
	for i := len(s) - len(sep); i >= 0; i-- {
		if s[i:i+len(sep)] == sep {
			return i
		}
	}
	return -1
}