package server

import (
	"errors"
	"fmt"
	"html"
	"log"
	"net/http"
	"os"
	"path/filepath"
	"runtime"
	"sync"
	"time"
)

const (
	address          = ":5000"
	htmlContentType  = "text/html; charset=utf-8"
	notFoundTemplate = `
		<div class="tui-window">
			<fieldset class="tui-fieldset">
				<legend>Error</legend>
				<p>Route %s not found.</p>
			</fieldset>
		</div>
		`
)

// Server hosts the Luxtools HTTP handlers.
type Server struct {
	mux        *http.ServeMux
	indexPage  []byte
	staticRoot string
	assetsRoot string

	counterMu  sync.Mutex
	clickCount int
}

// New constructs a configured Server ready to serve requests.
func New() (*Server, error) {
	projectRoot, err := goProjectRoot()
	if err != nil {
		return nil, err
	}

	indexPath := filepath.Join(projectRoot, "web", "templates", "index.html")
	staticDir := filepath.Join(projectRoot, "web", "static")
	assetsDir := filepath.Join(projectRoot, "assets")

	indexPage, err := os.ReadFile(indexPath)
	if err != nil {
		return nil, fmt.Errorf("failed to read index template: %w", err)
	}

	if _, err := os.Stat(staticDir); err != nil {
		return nil, fmt.Errorf("static directory check failed: %w", err)
	}
	if _, err := os.Stat(assetsDir); err != nil {
		return nil, fmt.Errorf("assets directory check failed: %w", err)
	}

	s := &Server{
		mux:        http.NewServeMux(),
		indexPage:  indexPage,
		staticRoot: staticDir,
		assetsRoot: assetsDir,
	}

	s.registerRoutes()
	return s, nil
}

// Router exposes the configured http.Handler for the server.
func (s *Server) Router() http.Handler {
	return s.mux
}

// Address returns the default listen address for the server.
func (s *Server) Address() string {
	return address
}

func (s *Server) registerRoutes() {
	s.mux.Handle("/static/", http.StripPrefix("/static/", allowGetHead(http.FileServer(http.Dir(s.staticRoot)))))
	s.mux.Handle("/assets/", http.StripPrefix("/assets/", allowGetHead(http.FileServer(http.Dir(s.assetsRoot)))))
	s.mux.HandleFunc("/", s.handleRequest)
}

func (s *Server) handleRequest(w http.ResponseWriter, r *http.Request) {
	switch r.URL.Path {
	case "/":
		s.sendHTML(w, http.StatusOK, s.indexPage)
	case "/counter":
		s.handleCounter(w, r)
	case "/time":
		s.sendHTMLString(w, http.StatusOK, renderTime(time.Now()))
	default:
		s.sendHTMLString(w, http.StatusNotFound, fmt.Sprintf(notFoundTemplate, html.EscapeString(r.URL.Path)))
	}
}

func (s *Server) handleCounter(w http.ResponseWriter, r *http.Request) {
	if r.Method == http.MethodPost || r.Method == http.MethodPut {
		s.counterMu.Lock()
		s.clickCount++
		s.counterMu.Unlock()
	}

	s.counterMu.Lock()
	count := s.clickCount
	s.counterMu.Unlock()

	s.sendHTMLString(w, http.StatusOK, renderCounter(count))
}

func (s *Server) sendHTML(w http.ResponseWriter, status int, body []byte) {
	w.Header().Set("Content-Type", htmlContentType)
	w.WriteHeader(status)
	if len(body) > 0 {
		if _, err := w.Write(body); err != nil {
			log.Printf("write response failed: %v", err)
		}
	}
}

func (s *Server) sendHTMLString(w http.ResponseWriter, status int, body string) {
	s.sendHTML(w, status, []byte(body))
}

func renderCounter(count int) string {
	return fmt.Sprintf(`
  <div id="counter" class="tui-panel tui-panel-inline">
    <p><strong>Clicks:</strong> %d</p>
    <button class="tui-button" hx-post="/counter" hx-target="#counter" hx-swap="outerHTML">
      Increment
    </button>
  </div>
  `, count)
}

func renderTime(now time.Time) string {
	return fmt.Sprintf(`
  <div id="server-time" class="tui-panel tui-panel-inline">
    <p><strong>Server time:</strong> %s</p>
  </div>
  `, now.Format("2006-01-02 15:04:05"))
}

func allowGetHead(next http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		switch r.Method {
		case http.MethodGet, http.MethodHead:
			next.ServeHTTP(w, r)
		default:
			http.NotFound(w, r)
		}
	})
}

func goProjectRoot() (string, error) {
	_, currentFile, _, ok := runtime.Caller(0)
	if !ok {
		return "", errors.New("unable to determine caller information")
	}

	dir := filepath.Dir(currentFile)
	projectRoot := filepath.Clean(filepath.Join(dir, "..", ".."))
	return projectRoot, nil
}