#include "webinterface.h"
#include <Arduino.h>
#include <DNSServer.h>
#include <Preferences.h>
#include <Update.h>
#include <WebServer.h>
#include <WiFi.h>
#include <cctype>

namespace
{
constexpr char default_access_point_password[] = "telemetry";
constexpr char settings_namespace[] = "telemetry";
constexpr char default_callsign[] = "D1234";
constexpr int default_min_speed = 80;
constexpr int default_max_speed = 150;
constexpr unsigned int default_active_time_seconds = 90;
constexpr unsigned long access_point_timeout_ms = 5UL * 60UL * 1000UL;
constexpr char telemetry_ap_prefix[] = "Telemetry-";

String default_access_point_name()
{
#ifdef DEVICE_SAILPLANE
  return String(telemetry_ap_prefix) + default_callsign;
#else
  return String(telemetry_ap_prefix) + "Winch";
#endif
}

String generated_access_point_name(const String &callsign)
{
#ifdef DEVICE_SAILPLANE
  String safe_callsign = callsign;
  if (safe_callsign.length() == 0)
    safe_callsign = default_callsign;
  return String(telemetry_ap_prefix) + safe_callsign;
#else
  return String(telemetry_ap_prefix) + "Winch";
#endif
}

String url_encode(const String &value)
{
  String encoded;
  encoded.reserve(value.length() * 3);
  for (unsigned int i = 0; i < value.length(); ++i)
  {
    const char c = value.charAt(i);
    if (std::isalnum(static_cast<unsigned char>(c)) || c == '-' || c == '_' || c == '.' || c == '~')
      encoded += c;
    else
    {
      char buffer[4];
      snprintf(buffer, sizeof(buffer), "%%%02X", static_cast<unsigned char>(c));
      encoded += buffer;
    }
  }
  return encoded;
}

WebServer server(80);
DNSServer dns_server;
Preferences preferences;
TelemetrySettings *active_settings = nullptr;
bool restart_after_update = false;
bool update_failed = false;
bool access_point_restart_pending = false;
bool access_point_active = false;
unsigned long access_point_started_ms = 0UL;

String html_escape(const String &value)
{
  String escaped = value;
  escaped.replace("&", "&amp;");
  escaped.replace("<", "&lt;");
  escaped.replace(">", "&gt;");
  escaped.replace("\"", "&quot;");
  escaped.replace("'", "&#39;");
  return escaped;
}

bool is_captive_portal_target(const String &host, const String &uri)
{
  String lowercase_host = host;
  lowercase_host.toLowerCase();

  String lowercase_uri = uri;
  lowercase_uri.toLowerCase();

  static const char *captive_hosts[] = {
      "connectivitycheck.gstatic.com",
      "clients3.google.com",
      "google.com",
      "www.google.com",
      "msftconnecttest.com",
      "msftncsi.com",
      "captive.apple.com",
      "www.apple.com",
      "apple.com",
      "connectivitycheck.android.com"};

  for (const char *candidate : captive_hosts)
  {
    if (lowercase_host == candidate)
      return true;
  }

  static const char *captive_paths[] = {
      "/generate_204",
      "/hotspot-detect.html",
      "/library/test/success.html",
      "/connecttest.txt",
      "/redirect",
      "/ncsi.txt",
      "/success.txt",
      "/wap"};

  for (const char *candidate : captive_paths)
  {
    if (lowercase_uri == candidate)
      return true;
  }

  return false;
}

void redirect_to_root(const String &message, bool success)
{
  String location = String("/?status=") + (success ? "success" : "error") + "&msg=" + url_encode(message);
  server.sendHeader("Location", location, true);
  server.send(303, "text/plain; charset=utf-8", "");
}

void handle_captive_portal_redirect()
{
  String host = server.hostHeader();
  String uri = server.uri();

  if (is_captive_portal_target(host, uri))
  {
    server.sendHeader("Location", "/", true);
    server.send(302, "text/plain; charset=utf-8", "");
    return;
  }

  server.send(404, "text/plain; charset=utf-8", "Not Found");
}

void send_page(const String &message = String())
{
  String page;
  page.reserve(2600);
  page += F("<!doctype html><html lang='de'><head><meta charset='utf-8'>"
            "<meta name='viewport' content='width=device-width,initial-scale=1'>"
            "<title>Winden-Telemetry</title><style>"
            "body{font-family:sans-serif;max-width:38rem;margin:2rem auto;padding:0 1rem}"
            "label{display:block;margin-top:1rem}input{box-sizing:border-box;width:100%;padding:.6rem;font-size:1rem}"
            "button{margin-top:1rem;padding:.65rem 1rem;font-size:1rem}"
            ".msg{padding:.6rem;background:#e5f4e8}.error{padding:.6rem;background:#fbe5e5}small{color:#555}"
            "</style></head><body><h1>Winden-Telemetry</h1>");
  if (message.length() > 0)
  {
    page += F("<p class='");
    page += String(message.startsWith("Fehler") || message.startsWith("Ungueltig") || message.startsWith("Invalid") ? "error" : "msg");
    page += F("'>");
    page += html_escape(message);
    page += F("</p>");
  }
  page += F("<p><small>Firmware: ");
  page += html_escape(firmware_version_string());
  page += F("</small></p><form method='post' action='/settings'>"
            "<label>WLAN-Name<input name='ap_name' maxlength='32' required value='");
  page += html_escape(active_settings->access_point_name);
  page += F("'></label><label>WLAN-Passwort<input name='ap_password' type='password' minlength='8' maxlength='63' required value='");
  page += html_escape(active_settings->access_point_password);
  page += F("'></label><label>Callsign<input name='callsign' maxlength='16' required value='");
  page += html_escape(active_settings->callsign);
  page += F("'></label><label>Min Speed (km/h)<input name='min' type='number' min='0' max='300' required value='");
  page += String(active_settings->min_speed);
  page += F("'></label><label>Max Speed (km/h)<input name='max' type='number' min='1' max='300' required value='");
  page += String(active_settings->max_speed);
  page += F("'></label><label>Uebertragungszeit (Sekunden)<input name='active_time' type='number' min='1' max='600' required value='");
  page += String(active_settings->active_time_seconds);
  page += F("'></label><button type='submit'>Speichern</button></form>"
            "<h2>Firmware aktualisieren</h2><form method='post' action='/update' enctype='multipart/form-data'>"
            "<input name='firmware' type='file' accept='.bin' required><button type='submit'>Upload starten</button>"
            "</form><p><small>Access Point: ");
  page += html_escape(active_settings->access_point_name);
  page += F("</small></p></body></html>");
  server.send(200, "text/html; charset=utf-8", page);
}

bool parse_settings(TelemetrySettings &settings)
{
  String callsign = server.arg("callsign");
  String access_point_name = server.arg("ap_name");
  String access_point_password = server.arg("ap_password");
  int min_speed = server.arg("min").toInt();
  int max_speed = server.arg("max").toInt();
  int active_time_seconds = server.arg("active_time").toInt();
  callsign.trim();
  access_point_name.trim();
  access_point_password.trim();

  if (callsign.length() == 0 || callsign.length() > 16 || access_point_password.length() < 8 || access_point_password.length() > 63 || min_speed < 0 || max_speed > 300 ||
      min_speed >= max_speed || active_time_seconds < 1 || active_time_seconds > 600)
    return false;

  settings.callsign = callsign;
  settings.access_point_name = generated_access_point_name(callsign);
  settings.access_point_password = access_point_password;
  settings.min_speed = min_speed;
  settings.max_speed = max_speed;
  settings.active_time_seconds = active_time_seconds;
  return true;
}

void handle_root()
{
  String message = server.arg("msg");
  String status = server.arg("status");
  if (status == "error" && message.length() == 0)
    message = "Ungueltige Einstellungen";
  else if (status == "success" && message.length() == 0)
    message = "Einstellungen gespeichert.";
  send_page(message);
}

void handle_settings()
{
  TelemetrySettings updated = *active_settings;
  if (!parse_settings(updated))
  {
    redirect_to_root("Ungueltige Einstellungen", false);
    return;
  }

  const bool ap_name_changed = active_settings->access_point_name != updated.access_point_name;
  const bool ap_password_changed = active_settings->access_point_password != updated.access_point_password;

  active_settings->callsign = updated.callsign;
  active_settings->access_point_name = updated.access_point_name;
  active_settings->access_point_password = updated.access_point_password;
  active_settings->min_speed = updated.min_speed;
  active_settings->max_speed = updated.max_speed;
  active_settings->active_time_seconds = updated.active_time_seconds;
  preferences.putString("callsign", active_settings->callsign);
  preferences.putString("ap_name", active_settings->access_point_name);
  preferences.putString("ap_password", active_settings->access_point_password);
  preferences.putInt("min", active_settings->min_speed);
  preferences.putInt("max", active_settings->max_speed);
  preferences.putUInt("active_time", active_settings->active_time_seconds);

  if (ap_name_changed || ap_password_changed)
    access_point_restart_pending = true;

  redirect_to_root("Einstellungen gespeichert.", true);
}

void handle_update_upload()
{
  HTTPUpload &upload = server.upload();
  if (upload.status == UPLOAD_FILE_START)
  {
    restart_after_update = false;
    update_failed = false;
    Serial.printf("Firmware-Upload: %s\n", upload.filename.c_str());
    if (!Update.begin(UPDATE_SIZE_UNKNOWN))
    {
      update_failed = true;
      Update.printError(Serial);
    }
  }
  else if (upload.status == UPLOAD_FILE_WRITE)
  {
    if (Update.write(upload.buf, upload.currentSize) != upload.currentSize)
    {
      update_failed = true;
      Update.printError(Serial);
    }
  }
  else if (upload.status == UPLOAD_FILE_END)
  {
    if (Update.end(true))
    {
      restart_after_update = true;
      Serial.printf("Firmware-Upload abgeschlossen: %u Bytes\n", upload.totalSize);
    }
    else
    {
      update_failed = true;
      Update.printError(Serial);
    }
  }
}

void handle_update_result()
{
  if (!update_failed && restart_after_update)
  {
    server.send(200, "text/plain; charset=utf-8", "Upload erfolgreich. Neustart...");
    if (restart_after_update)
    {
      delay(500);
      ESP.restart();
    }
  }
  else
    server.send(500, "text/plain; charset=utf-8", "Firmware-Upload fehlgeschlagen");
}
} // namespace

String firmware_version_string(void)
{
#ifdef FIRMWARE_VERSION
  return String(FIRMWARE_VERSION);
#else
  return "dev";
#endif
}

bool webinterface_begin(TelemetrySettings &settings)
{
  active_settings = &settings;
  preferences.begin(settings_namespace, false);
  settings.callsign = preferences.getString("callsign", default_callsign);
  settings.access_point_name = preferences.getString("ap_name", default_access_point_name());
  settings.access_point_password = preferences.getString("ap_password", default_access_point_password);
  settings.min_speed = preferences.getInt("min", default_min_speed);
  settings.max_speed = preferences.getInt("max", default_max_speed);
  settings.active_time_seconds = preferences.getUInt("active_time", default_active_time_seconds);
  if (settings.access_point_name.length() == 0 || settings.access_point_name.length() > 32 || settings.access_point_password.length() < 8 || settings.access_point_password.length() > 63 || settings.callsign.length() == 0 || settings.min_speed < 0 || settings.min_speed >= settings.max_speed ||
      settings.max_speed > 300 || settings.active_time_seconds < 1 || settings.active_time_seconds > 600)
  {
    settings.callsign = default_callsign;
    settings.access_point_name = default_access_point_name();
    settings.access_point_password = default_access_point_password;
    settings.min_speed = default_min_speed;
    settings.max_speed = default_max_speed;
    settings.active_time_seconds = default_active_time_seconds;
  }
  else
  {
    settings.access_point_name = generated_access_point_name(settings.callsign);
  }

  WiFi.mode(WIFI_AP);
  bool ap_started = WiFi.softAP(settings.access_point_name, settings.access_point_password);
  if (!ap_started)
    return false;

  access_point_active = true;
  access_point_started_ms = millis();
  dns_server.start(53, "connectivitycheck.gstatic.com", WiFi.softAPIP());
  dns_server.start(53, "clients3.google.com", WiFi.softAPIP());
  dns_server.start(53, "msftconnecttest.com", WiFi.softAPIP());
  dns_server.start(53, "msftncsi.com", WiFi.softAPIP());
  dns_server.start(53, "captive.apple.com", WiFi.softAPIP());
  dns_server.start(53, "apple.com", WiFi.softAPIP());
  dns_server.start(53, "*", WiFi.softAPIP());
  server.on("/", HTTP_GET, handle_root);
  server.on("/generate_204", HTTP_GET, handle_captive_portal_redirect);
  server.on("/hotspot-detect.html", HTTP_GET, handle_captive_portal_redirect);
  server.on("/connecttest.txt", HTTP_GET, handle_captive_portal_redirect);
  server.on("/ncsi.txt", HTTP_GET, handle_captive_portal_redirect);
  server.on("/success.txt", HTTP_GET, handle_captive_portal_redirect);
  server.on("/settings", HTTP_POST, handle_settings);
  server.on("/update", HTTP_POST, handle_update_result, handle_update_upload);
  server.onNotFound(handle_captive_portal_redirect);
  server.begin();
  Serial.print("Firmware-Version: ");
  Serial.println(firmware_version_string());
  Serial.print("Webinterface: http://");
  Serial.println(WiFi.softAPIP());
  return true;
}

void webinterface_handle(void)
{
  server.handleClient();
  dns_server.processNextRequest();
  if (access_point_restart_pending)
  {
    access_point_restart_pending = false;
    WiFi.softAPdisconnect(true);
    access_point_active = false;
    delay(100);
    if (!WiFi.softAP(active_settings->access_point_name, active_settings->access_point_password))
      Serial.println("Access Point konnte nicht neu gestartet werden");
    else
      access_point_active = true;
    access_point_started_ms = millis();
  }

  if (access_point_active && WiFi.softAPgetStationNum() == 0 && (millis() - access_point_started_ms) >= access_point_timeout_ms)
  {
    Serial.println("Access Point nach 5 Minuten ohne Client deaktiviert");
    WiFi.softAPdisconnect(true);
    access_point_active = false;
  }
}

const TelemetrySettings &webinterface_settings(void)
{
  return *active_settings;
}