// adapted from https://www.avahi.org/doxygen/html/client-publish-service_8c-example.html
#include <thread>

#include "misc.h"
#include "sunshine/main.h"
#include "sunshine/nvhttp.h"
#include "sunshine/platform/common.h"
#include "sunshine/utility.h"

using namespace std::literals;

namespace avahi {

/** Error codes used by avahi */
enum err_e {
  OK                      = 0,  /**< OK */
  ERR_FAILURE             = -1, /**< Generic error code */
  ERR_BAD_STATE           = -2, /**< Object was in a bad state */
  ERR_INVALID_HOST_NAME   = -3, /**< Invalid host name */
  ERR_INVALID_DOMAIN_NAME = -4, /**< Invalid domain name */
  ERR_NO_NETWORK          = -5, /**< No suitable network protocol available */
  ERR_INVALID_TTL         = -6, /**< Invalid DNS TTL */
  ERR_IS_PATTERN          = -7, /**< RR key is pattern */
  ERR_COLLISION           = -8, /**< Name collision */
  ERR_INVALID_RECORD      = -9, /**< Invalid RR */

  ERR_INVALID_SERVICE_NAME = -10, /**< Invalid service name */
  ERR_INVALID_SERVICE_TYPE = -11, /**< Invalid service type */
  ERR_INVALID_PORT         = -12, /**< Invalid port number */
  ERR_INVALID_KEY          = -13, /**< Invalid key */
  ERR_INVALID_ADDRESS      = -14, /**< Invalid address */
  ERR_TIMEOUT              = -15, /**< Timeout reached */
  ERR_TOO_MANY_CLIENTS     = -16, /**< Too many clients */
  ERR_TOO_MANY_OBJECTS     = -17, /**< Too many objects */
  ERR_TOO_MANY_ENTRIES     = -18, /**< Too many entries */
  ERR_OS                   = -19, /**< OS error */

  ERR_ACCESS_DENIED     = -20, /**< Access denied */
  ERR_INVALID_OPERATION = -21, /**< Invalid operation */
  ERR_DBUS_ERROR        = -22, /**< An unexpected D-Bus error occurred */
  ERR_DISCONNECTED      = -23, /**< Daemon connection failed */
  ERR_NO_MEMORY         = -24, /**< Memory exhausted */
  ERR_INVALID_OBJECT    = -25, /**< The object passed to this function was invalid */
  ERR_NO_DAEMON         = -26, /**< Daemon not running */
  ERR_INVALID_INTERFACE = -27, /**< Invalid interface */
  ERR_INVALID_PROTOCOL  = -28, /**< Invalid protocol */
  ERR_INVALID_FLAGS     = -29, /**< Invalid flags */

  ERR_NOT_FOUND               = -30, /**< Not found */
  ERR_INVALID_CONFIG          = -31, /**< Configuration error */
  ERR_VERSION_MISMATCH        = -32, /**< Verson mismatch */
  ERR_INVALID_SERVICE_SUBTYPE = -33, /**< Invalid service subtype */
  ERR_INVALID_PACKET          = -34, /**< Invalid packet */
  ERR_INVALID_DNS_ERROR       = -35, /**< Invlaid DNS return code */
  ERR_DNS_FORMERR             = -36, /**< DNS Error: Form error */
  ERR_DNS_SERVFAIL            = -37, /**< DNS Error: Server Failure */
  ERR_DNS_NXDOMAIN            = -38, /**< DNS Error: No such domain */
  ERR_DNS_NOTIMP              = -39, /**< DNS Error: Not implemented */

  ERR_DNS_REFUSED       = -40, /**< DNS Error: Operation refused */
  ERR_DNS_YXDOMAIN      = -41,
  ERR_DNS_YXRRSET       = -42,
  ERR_DNS_NXRRSET       = -43,
  ERR_DNS_NOTAUTH       = -44, /**< DNS Error: Not authorized */
  ERR_DNS_NOTZONE       = -45,
  ERR_INVALID_RDATA     = -46, /**< Invalid RDATA */
  ERR_INVALID_DNS_CLASS = -47, /**< Invalid DNS class */
  ERR_INVALID_DNS_TYPE  = -48, /**< Invalid DNS type */
  ERR_NOT_SUPPORTED     = -49, /**< Not supported */

  ERR_NOT_PERMITTED    = -50, /**< Operation not permitted */
  ERR_INVALID_ARGUMENT = -51, /**< Invalid argument */
  ERR_IS_EMPTY         = -52, /**< Is empty */
  ERR_NO_CHANGE        = -53, /**< The requested operation is invalid because it is redundant */

  ERR_MAX = -54
};

constexpr auto IF_UNSPEC = -1;
enum proto {
  PROTO_INET   = 0, /**< IPv4 */
  PROTO_INET6  = 1, /**< IPv6 */
  PROTO_UNSPEC = -1 /**< Unspecified/all protocol(s) */
};

enum ServerState {
  SERVER_INVALID,     /**< Invalid state (initial) */
  SERVER_REGISTERING, /**< Host RRs are being registered */
  SERVER_RUNNING,     /**< All host RRs have been established */
  SERVER_COLLISION,   /**< There is a collision with a host RR. All host RRs have been withdrawn, the user should set a new host name via avahi_server_set_host_name() */
  SERVER_FAILURE      /**< Some fatal failure happened, the server is unable to proceed */
};

enum ClientState {
  CLIENT_S_REGISTERING = SERVER_REGISTERING, /**< Server state: REGISTERING */
  CLIENT_S_RUNNING     = SERVER_RUNNING,     /**< Server state: RUNNING */
  CLIENT_S_COLLISION   = SERVER_COLLISION,   /**< Server state: COLLISION */
  CLIENT_FAILURE       = 100,                /**< Some kind of error happened on the client side */
  CLIENT_CONNECTING    = 101                 /**< We're still connecting. This state is only entered when AVAHI_CLIENT_NO_FAIL has been passed to avahi_client_new() and the daemon is not yet available. */
};

enum EntryGroupState {
  ENTRY_GROUP_UNCOMMITED,  /**< The group has not yet been commited, the user must still call avahi_entry_group_commit() */
  ENTRY_GROUP_REGISTERING, /**< The entries of the group are currently being registered */
  ENTRY_GROUP_ESTABLISHED, /**< The entries have successfully been established */
  ENTRY_GROUP_COLLISION,   /**< A name collision for one of the entries in the group has been detected, the entries have been withdrawn */
  ENTRY_GROUP_FAILURE      /**< Some kind of failure happened, the entries have been withdrawn */
};

enum ClientFlags {
  CLIENT_IGNORE_USER_CONFIG = 1, /**< Don't read user configuration */
  CLIENT_NO_FAIL            = 2  /**< Don't fail if the daemon is not available when avahi_client_new() is called, instead enter CLIENT_CONNECTING state and wait for the daemon to appear */
};

/** Some flags for publishing functions */
enum PublishFlags {
  PUBLISH_UNIQUE         = 1,  /**< For raw records: The RRset is intended to be unique */
  PUBLISH_NO_PROBE       = 2,  /**< For raw records: Though the RRset is intended to be unique no probes shall be sent */
  PUBLISH_NO_ANNOUNCE    = 4,  /**< For raw records: Do not announce this RR to other hosts */
  PUBLISH_ALLOW_MULTIPLE = 8,  /**< For raw records: Allow multiple local records of this type, even if they are intended to be unique */
                               /** \cond fulldocs */
  PUBLISH_NO_REVERSE = 16,     /**< For address records: don't create a reverse (PTR) entry */
  PUBLISH_NO_COOKIE  = 32,     /**< For service records: do not implicitly add the local service cookie to TXT data */
                               /** \endcond */
  PUBLISH_UPDATE = 64,         /**< Update existing records instead of adding new ones */
                               /** \cond fulldocs */
  PUBLISH_USE_WIDE_AREA = 128, /**< Register the record using wide area DNS (i.e. unicast DNS update) */
  PUBLISH_USE_MULTICAST = 256  /**< Register the record using multicast DNS */
  /** \endcond */
};

using IfIndex  = int;
using Protocol = int;

struct EntryGroup;
struct Poll;
struct SimplePoll;
struct Client;

typedef void (*ClientCallback)(Client *, ClientState, void *userdata);
typedef void (*EntryGroupCallback)(EntryGroup *g, EntryGroupState state, void *userdata);

typedef void (*free_fn)(void *);

typedef Client *(*client_new_fn)(const Poll *poll_api, ClientFlags flags, ClientCallback callback, void *userdata, int *error);
typedef void (*client_free_fn)(Client *);
typedef char *(*alternative_service_name_fn)(char *);

typedef Client *(*entry_group_get_client_fn)(EntryGroup *);

typedef EntryGroup *(*entry_group_new_fn)(Client *, EntryGroupCallback, void *userdata);
typedef int (*entry_group_add_service_fn)(
  EntryGroup *group,
  IfIndex interface,
  Protocol protocol,
  PublishFlags flags,
  const char *name,
  const char *type,
  const char *domain,
  const char *host,
  uint16_t port,
  ...);

typedef int (*entry_group_is_empty_fn)(EntryGroup *);
typedef int (*entry_group_reset_fn)(EntryGroup *);
typedef int (*entry_group_commit_fn)(EntryGroup *);

typedef char *(*strdup_fn)(const char *);
typedef char *(*strerror_fn)(int);
typedef int (*client_errno_fn)(Client *);

typedef Poll *(*simple_poll_get_fn)(SimplePoll *);
typedef int (*simple_poll_loop_fn)(SimplePoll *);
typedef void (*simple_poll_quit_fn)(SimplePoll *);
typedef SimplePoll *(*simple_poll_new_fn)();
typedef void (*simple_poll_free_fn)(SimplePoll *);

free_fn free;
client_new_fn client_new;
client_free_fn client_free;
alternative_service_name_fn alternative_service_name;
entry_group_get_client_fn entry_group_get_client;
entry_group_new_fn entry_group_new;
entry_group_add_service_fn entry_group_add_service;
entry_group_is_empty_fn entry_group_is_empty;
entry_group_reset_fn entry_group_reset;
entry_group_commit_fn entry_group_commit;
strdup_fn strdup;
strerror_fn strerror;
client_errno_fn client_errno;
simple_poll_get_fn simple_poll_get;
simple_poll_loop_fn simple_poll_loop;
simple_poll_quit_fn simple_poll_quit;
simple_poll_new_fn simple_poll_new;
simple_poll_free_fn simple_poll_free;


int init_common() {
  static void *handle { nullptr };
  static bool funcs_loaded = false;

  if(funcs_loaded) return 0;

  if(!handle) {
    handle = dyn::handle({ "libavahi-common.so.3", "libavahi-common.so" });
    if(!handle) {
      return -1;
    }
  }

  std::vector<std::tuple<dyn::apiproc *, const char *>> funcs {
    { (dyn::apiproc *)&alternative_service_name, "avahi_alternative_service_name" },
    { (dyn::apiproc *)&free, "avahi_free" },
    { (dyn::apiproc *)&strdup, "avahi_strdup" },
    { (dyn::apiproc *)&strerror, "avahi_strerror" },
    { (dyn::apiproc *)&simple_poll_get, "avahi_simple_poll_get" },
    { (dyn::apiproc *)&simple_poll_loop, "avahi_simple_poll_loop" },
    { (dyn::apiproc *)&simple_poll_quit, "avahi_simple_poll_quit" },
    { (dyn::apiproc *)&simple_poll_new, "avahi_simple_poll_new" },
    { (dyn::apiproc *)&simple_poll_free, "avahi_simple_poll_free" },
  };

  if(dyn::load(handle, funcs)) {
    return -1;
  }

  funcs_loaded = true;
  return 0;
}

int init_client() {
  if(init_common()) {
    return -1;
  }

  static void *handle { nullptr };
  static bool funcs_loaded = false;

  if(funcs_loaded) return 0;

  if(!handle) {
    handle = dyn::handle({ "libavahi-client.so.3", "libavahi-client.so" });
    if(!handle) {
      return -1;
    }
  }

  std::vector<std::tuple<dyn::apiproc *, const char *>> funcs {
    { (dyn::apiproc *)&client_new, "avahi_client_new" },
    { (dyn::apiproc *)&client_free, "avahi_client_free" },
    { (dyn::apiproc *)&entry_group_get_client, "avahi_entry_group_get_client" },
    { (dyn::apiproc *)&entry_group_new, "avahi_entry_group_new" },
    { (dyn::apiproc *)&entry_group_add_service, "avahi_entry_group_add_service" },
    { (dyn::apiproc *)&entry_group_is_empty, "avahi_entry_group_is_empty" },
    { (dyn::apiproc *)&entry_group_reset, "avahi_entry_group_reset" },
    { (dyn::apiproc *)&entry_group_commit, "avahi_entry_group_commit" },
    { (dyn::apiproc *)&client_errno, "avahi_client_errno" },
  };

  if(dyn::load(handle, funcs)) {
    return -1;
  }

  funcs_loaded = true;
  return 0;
}
} // namespace avahi

namespace platf::publish {

template<class T>
void free(T *p) {
  avahi::free(p);
}

template<class T>
using ptr_t    = util::safe_ptr<T, free<T>>;
using client_t = util::dyn_safe_ptr<avahi::Client, &avahi::client_free>;
using poll_t   = util::dyn_safe_ptr<avahi::SimplePoll, &avahi::simple_poll_free>;

avahi::EntryGroup *group = nullptr;

poll_t poll;
client_t client;

ptr_t<char> name;

void create_services(avahi::Client *c);

void entry_group_callback(avahi::EntryGroup *g, avahi::EntryGroupState state, void *) {
  group = g;

  switch(state) {
  case avahi::ENTRY_GROUP_ESTABLISHED:
    BOOST_LOG(info) << "Avahi service " << name.get() << " successfully established.";
    break;
  case avahi::ENTRY_GROUP_COLLISION:
    name.reset(avahi::alternative_service_name(name.get()));

    BOOST_LOG(info) << "Avahi service name collision, renaming service to " << name.get();

    create_services(avahi::entry_group_get_client(g));
    break;
  case avahi::ENTRY_GROUP_FAILURE:
    BOOST_LOG(error) << "Avahi entry group failure: " << avahi::strerror(avahi::client_errno(avahi::entry_group_get_client(g)));
    avahi::simple_poll_quit(poll.get());
    break;
  case avahi::ENTRY_GROUP_UNCOMMITED:
  case avahi::ENTRY_GROUP_REGISTERING:;
  }
}

void create_services(avahi::Client *c) {
  int ret;

  auto fg = util::fail_guard([]() {
    avahi::simple_poll_quit(poll.get());
  });

  if(!group) {
    if(!(group = avahi::entry_group_new(c, entry_group_callback, nullptr))) {
      BOOST_LOG(error) << "avahi::entry_group_new() failed: "sv << avahi::strerror(avahi::client_errno(c));
      return;
    }
  }

  if(avahi::entry_group_is_empty(group)) {
    BOOST_LOG(info) << "Adding avahi service "sv << name.get();

    ret = avahi::entry_group_add_service(
      group,
      avahi::IF_UNSPEC, avahi::PROTO_UNSPEC,
      avahi::PublishFlags(0),
      name.get(),
      SERVICE_TYPE,
      nullptr, nullptr,
      map_port(nvhttp::PORT_HTTP),
      nullptr);

    if(ret < 0) {
      if(ret == avahi::ERR_COLLISION) {
        // A service name collision with a local service happened. Let's pick a new name
        name.reset(avahi::alternative_service_name(name.get()));
        BOOST_LOG(info) << "Service name collision, renaming service to "sv << name.get();

        avahi::entry_group_reset(group);

        create_services(c);

        fg.disable();
        return;
      }

      BOOST_LOG(error) << "Failed to add "sv << SERVICE_TYPE << " service: "sv << avahi::strerror(ret);
      return;
    }

    ret = avahi::entry_group_commit(group);
    if(ret < 0) {
      BOOST_LOG(error) << "Failed to commit entry group: "sv << avahi::strerror(ret);
      return;
    }
  }

  fg.disable();
}

void client_callback(avahi::Client *c, avahi::ClientState state, void *) {
  switch(state) {
  case avahi::CLIENT_S_RUNNING:
    create_services(c);
    break;
  case avahi::CLIENT_FAILURE:
    BOOST_LOG(error) << "Client failure: "sv << avahi::strerror(avahi::client_errno(c));
    avahi::simple_poll_quit(poll.get());
    break;
  case avahi::CLIENT_S_COLLISION:
  case avahi::CLIENT_S_REGISTERING:
    if(group)
      avahi::entry_group_reset(group);
    break;
  case avahi::CLIENT_CONNECTING:;
  }
}

class deinit_t : public ::platf::deinit_t {
public:
  std::thread poll_thread;

  deinit_t(std::thread poll_thread) : poll_thread { std::move(poll_thread) } {}

  ~deinit_t() override {
    if(avahi::simple_poll_quit && poll) {
      avahi::simple_poll_quit(poll.get());
    }

    if(poll_thread.joinable()) {
      poll_thread.join();
    }
  }
};

[[nodiscard]] std::unique_ptr<::platf::deinit_t> start() {
  if(avahi::init_client()) {
    return nullptr;
  }

  int avhi_error;

  poll.reset(avahi::simple_poll_new());
  if(!poll) {
    BOOST_LOG(error) << "Failed to create simple poll object."sv;
    return nullptr;
  }

  name.reset(avahi::strdup(SERVICE_NAME));

  client.reset(
    avahi::client_new(avahi::simple_poll_get(poll.get()), avahi::ClientFlags(0), client_callback, nullptr, &avhi_error));

  if(!client) {
    BOOST_LOG(error) << "Failed to create client: "sv << avahi::strerror(avhi_error);
    return nullptr;
  }

  return std::make_unique<deinit_t>(std::thread { avahi::simple_poll_loop, poll.get() });
}
} // namespace platf::publish