// NextNVR — MIT License
// Copyright (c) 2026 NextNVR Contributors
// SPDX-License-Identifier: MIT
//
// auth.go — Session-based authentication with bcrypt password hashing.
package main

import (
	"crypto/rand"
	"encoding/hex"
	"encoding/json"
	"net/http"
	"strings"
	"sync"
	"time"

	"golang.org/x/crypto/bcrypt"
)

// SessionStore holds authenticated sessions in memory.
type SessionStore struct {
	mu       sync.RWMutex
	sessions map[string]*Session
}

// Session represents an authenticated user session.
type Session struct {
	Username string
	Role     string // "master" or "viewer"
	Expires  time.Time
}

// NewSessionStore creates a new in-memory session store.
func NewSessionStore() *SessionStore {
	s := &SessionStore{sessions: make(map[string]*Session)}
	go s.cleanupLoop()
	return s
}

// Create generates a new session token and stores it.
func (s *SessionStore) Create(username, role string) string {
	s.mu.Lock()
	defer s.mu.Unlock()
	token := generateToken()
	s.sessions[token] = &Session{
		Username: username,
		Role:     role,
		Expires:  time.Now().Add(24 * time.Hour),
	}
	return token
}

// Get returns a session by token, or nil if expired/missing.
func (s *SessionStore) Get(token string) *Session {
	s.mu.RLock()
	defer s.mu.RUnlock()
	sess, ok := s.sessions[token]
	if !ok || time.Now().After(sess.Expires) {
		return nil
	}
	return sess
}

// Delete removes a session (logout).
func (s *SessionStore) Delete(token string) {
	s.mu.Lock()
	defer s.mu.Unlock()
	delete(s.sessions, token)
}

// cleanupLoop removes expired sessions every hour.
func (s *SessionStore) cleanupLoop() {
	ticker := time.NewTicker(1 * time.Hour)
	for range ticker.C {
		s.mu.Lock()
		now := time.Now()
		for token, sess := range s.sessions {
			if now.After(sess.Expires) {
				delete(s.sessions, token)
			}
		}
		s.mu.Unlock()
	}
}

func generateToken() string {
	b := make([]byte, 32)
	rand.Read(b)
	return hex.EncodeToString(b)
}

// ── Handlers ──

// handleLogin processes POST /api/login.
func (s *Server) handleLogin(w http.ResponseWriter, r *http.Request) {
	if r.Method != http.MethodPost {
		jsonResponse(w, http.StatusMethodNotAllowed, APIResponse{Error: "method not allowed"})
		return
	}

	var req struct {
		Username string `json:"username"`
		Password string `json:"password"`
	}
	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
		jsonResponse(w, http.StatusBadRequest, APIResponse{Error: "invalid request"})
		return
	}

	auth := s.appConfig.Auth

	// Check master credentials.
	if auth.Master.Username != "" && req.Username == auth.Master.Username {
		if err := bcrypt.CompareHashAndPassword([]byte(auth.Master.Password), []byte(req.Password)); err == nil {
			token := s.sessions.Create(req.Username, "master")
			http.SetCookie(w, &http.Cookie{
				Name:     "session",
				Value:    token,
				Path:     "/",
				HttpOnly: true,
				SameSite: http.SameSiteLaxMode,
				MaxAge:   86400,
			})
			jsonResponse(w, http.StatusOK, APIResponse{Success: true, Data: map[string]string{"role": "master"}})
			return
		}
	}

	// Check viewer credentials.
	if auth.Viewer.Enabled && auth.Viewer.Username != "" && req.Username == auth.Viewer.Username {
		if err := bcrypt.CompareHashAndPassword([]byte(auth.Viewer.Password), []byte(req.Password)); err == nil {
			token := s.sessions.Create(req.Username, "viewer")
			http.SetCookie(w, &http.Cookie{
				Name:     "session",
				Value:    token,
				Path:     "/",
				HttpOnly: true,
				SameSite: http.SameSiteLaxMode,
				MaxAge:   86400,
			})
			jsonResponse(w, http.StatusOK, APIResponse{Success: true, Data: map[string]string{"role": "viewer"}})
			return
		}
	}

	jsonResponse(w, http.StatusUnauthorized, APIResponse{Error: "invalid credentials"})
}

// handleLogout processes POST /api/logout.
func (s *Server) handleLogout(w http.ResponseWriter, r *http.Request) {
	if cookie, err := r.Cookie("session"); err == nil {
		s.sessions.Delete(cookie.Value)
	}
	http.SetCookie(w, &http.Cookie{
		Name:     "session",
		Value:    "",
		Path:     "/",
		MaxAge:   -1,
		HttpOnly: true,
	})
	jsonResponse(w, http.StatusOK, APIResponse{Success: true, Data: "logged out"})
}

// handleSession returns the current session info.
func (s *Server) handleSession(w http.ResponseWriter, r *http.Request) {
	cookie, err := r.Cookie("session")
	if err != nil {
		jsonResponse(w, http.StatusOK, APIResponse{Success: true, Data: map[string]string{"role": ""}})
		return
	}
	sess := s.sessions.Get(cookie.Value)
	if sess == nil {
		jsonResponse(w, http.StatusOK, APIResponse{Success: true, Data: map[string]string{"role": ""}})
		return
	}
	jsonResponse(w, http.StatusOK, APIResponse{Success: true, Data: map[string]string{"role": sess.Role, "username": sess.Username}})
}

// ── Middleware ──

// authRequired redirects to /login if no valid session.
func (s *Server) authRequired(next http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		// Allow login page and API, static assets, and recordings.
		path := r.URL.Path
		if path == "/login" || path == "/login.html" ||
			strings.HasPrefix(path, "/api/login") ||
			strings.HasPrefix(path, "/api/logout") ||
			strings.HasPrefix(path, "/api/session") ||
			strings.HasPrefix(path, "/recordings/") ||
			strings.HasPrefix(path, "/go2rtc/") ||
			strings.HasPrefix(path, "/stream/") {
			next.ServeHTTP(w, r)
			return
		}

		// If auth is disabled, allow all.
		if !s.appConfig.Auth.Enabled {
			next.ServeHTTP(w, r)
			return
		}

		cookie, err := r.Cookie("session")
		if err != nil {
			// Redirect API calls with 401, page requests to /login.
			if strings.HasPrefix(path, "/api/") {
				jsonResponse(w, http.StatusUnauthorized, APIResponse{Error: "authentication required"})
			} else {
				http.Redirect(w, r, "/login", http.StatusFound)
			}
			return
		}

		sess := s.sessions.Get(cookie.Value)
		if sess == nil {
			if strings.HasPrefix(path, "/api/") {
				jsonResponse(w, http.StatusUnauthorized, APIResponse{Error: "session expired"})
			} else {
				http.Redirect(w, r, "/login", http.StatusFound)
			}
			return
		}

		// Inject role into request context.
		r.Header.Set("X-NextNVR-Role", sess.Role)
		next.ServeHTTP(w, r)
	})
}

// viewerOnly restricts access to live wall only (port 8090).
func (s *Server) viewerOnly(next http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		path := r.URL.Path
		// Allow live wall assets and recordings.
		if path == "/" || path == "/index.html" ||
			strings.HasPrefix(path, "/app.js") ||
			strings.HasPrefix(path, "/style.css") ||
			strings.HasPrefix(path, "/recordings/") ||
			strings.HasPrefix(path, "/go2rtc/") ||
			strings.HasPrefix(path, "/stream/") ||
			strings.HasPrefix(path, "/api/cameras") ||
			strings.HasPrefix(path, "/api/status") {
			r.Header.Set("X-NextNVR-Role", "viewer")
			next.ServeHTTP(w, r)
			return
		}
		// Block everything else (settings, playback API, config).
		jsonResponse(w, http.StatusForbidden, APIResponse{Error: "viewer access only"})
	})
}

// HashPassword returns a bcrypt hash of the password.
func HashPassword(password string) (string, error) {
	bytes, err := bcrypt.GenerateFromPassword([]byte(password), bcrypt.DefaultCost)
	return string(bytes), err
}