/**
 * @file  client_find_servers.c
 * @brief OPC UA client that queries a Local Discovery Server for registered
 * servers.
 *
 * This program connects to an LDS and calls the FindServers service to
 * retrieve all registered servers. It then queries each server's endpoints
 * using the GetEndpoints service and displays the results in a human-readable
 * format.
 */

#include "common.h"
#include "config.h"

#include <open62541/client_highlevel.h>
#include <open62541/plugin/log_stdout.h>

#include <stdlib.h>
#include <string.h>

/* ========================================================================
 * Discovery Service Calls
 * ======================================================================== */

/**
 * Calls the FindServers service on the LDS and prints all discovered servers.
 *
 * @param client The OPC UA client instance.
 * @param discoveryServerEndpoint The LDS endpoint URL.
 * @param applicationDescriptionArraySize Output: number of servers found.
 * @param applicationDescriptionArray Output: array of server descriptions.
 * @return UA_STATUSCODE_GOOD on success, error code otherwise.
 */
static UA_StatusCode
findServers (UA_Client *client, const char *discoveryServerEndpoint,
             size_t *applicationDescriptionArraySize,
             UA_ApplicationDescription **applicationDescriptionArray)
{
  UA_StatusCode retval = UA_Client_findServers (
      client, discoveryServerEndpoint, 0, NULL, 0, NULL,
      applicationDescriptionArraySize, applicationDescriptionArray);

  if (retval != UA_STATUSCODE_GOOD)
    {
      UA_LOG_ERROR (UA_Log_Stdout, UA_LOGCATEGORY_SERVER,
                    "Could not call FindServers service. "
                    "Is the discovery server started? StatusCode %s",
                    UA_StatusCode_name (retval));
      return retval;
    }

  for (size_t i = 0; i < *applicationDescriptionArraySize; i++)
    printApplicationDescription (&(*applicationDescriptionArray)[i], i);

  return UA_STATUSCODE_GOOD;
}

/**
 * Queries endpoints for each discovered server using the GetEndpoints service.
 *
 * For each server in the applicationDescriptionArray, this function extracts
 * the first discovery URL and calls GetEndpoints to retrieve all available
 * endpoints. Results are logged via UA_LOG_INFO.
 *
 * @param client The OPC UA client instance.
 * @param applicationDescriptionArray Array of server descriptions from
 * FindServers.
 * @param applicationDescriptionArraySize Number of servers in the array.
 */
static void
getServersEndpoints (UA_Client *client,
                     UA_ApplicationDescription *applicationDescriptionArray,
                     size_t applicationDescriptionArraySize)
{
  for (size_t i = 0; i < applicationDescriptionArraySize; i++)
    {
      UA_ApplicationDescription *description = &applicationDescriptionArray[i];
      if (description->discoveryUrlsSize == 0)
        {
          UA_LOG_INFO (UA_Log_Stdout, UA_LOGCATEGORY_CLIENT,
                       "[GetEndpoints] Server %.*s did not provide any "
                       "discovery urls. Skipping.",
                       (int)description->applicationUri.length,
                       description->applicationUri.data);
          continue;
        }

      /* UA_String is not null-terminated; build a C string for the API. */
      char *discoveryUrl = (char *)UA_malloc (
          sizeof (char) * description->discoveryUrls[0].length + 1);
      memcpy (discoveryUrl, description->discoveryUrls[0].data,
              description->discoveryUrls[0].length);
      discoveryUrl[description->discoveryUrls[0].length] = '\0';

      UA_EndpointDescription *endpointArray = NULL;
      size_t endpointArraySize = 0;
      UA_StatusCode retval = UA_Client_getEndpoints (
          client, discoveryUrl, &endpointArraySize, &endpointArray);
      UA_free (discoveryUrl);
      if (retval != UA_STATUSCODE_GOOD)
        {
          UA_Client_disconnect (client);
          break;
        }

      UA_LOG_INFO (UA_Log_Stdout, UA_LOGCATEGORY_APPLICATION,
                   "Endpoints for Server[%lu]: %.*s", (unsigned long)i,
                   (int)description->applicationUri.length,
                   description->applicationUri.data);
      for (size_t j = 0; j < endpointArraySize; j++)
        printEndpoint (&endpointArray[j], j);

      UA_Array_delete (endpointArray, endpointArraySize,
                       &UA_TYPES[UA_TYPES_ENDPOINTDESCRIPTION]);
    }
}

/* ========================================================================
 * Node Reading
 * ======================================================================== */

/**
 * Connects to each non-discovery server and reads the current time node.
 *
 * For each server that is not a DiscoveryServer, this function establishes a
 * secure session, reads the Server_ServerStatus_CurrentTime variable, prints
 * the result, and disconnects.
 *
 * @param client The OPC UA client instance.
 * @param applicationDescriptionArray Array of server descriptions from
 * FindServers.
 * @param applicationDescriptionArraySize Number of servers in the array.
 * @param username Username for session auth, or NULL for anonymous.
 * @param password Password for session auth (ignored when username is NULL).
 */
static void
readServerTime (UA_Client *client,
                UA_ApplicationDescription *applicationDescriptionArray,
                size_t applicationDescriptionArraySize, const char *username,
                const char *password)
{
  for (size_t i = 0; i < applicationDescriptionArraySize; i++)
    {
      UA_ApplicationDescription *desc = &applicationDescriptionArray[i];

      if (desc->applicationType == UA_APPLICATIONTYPE_DISCOVERYSERVER)
        continue;

      if (desc->discoveryUrlsSize == 0)
        {
          UA_LOG_INFO (UA_Log_Stdout, UA_LOGCATEGORY_CLIENT,
                       "[ReadTime] Server %.*s has no discovery URLs. "
                       "Skipping.",
                       (int)desc->applicationUri.length,
                       desc->applicationUri.data);
          continue;
        }

      /* UA_String is not null-terminated; build a C string for the API. */
      char *url = (char *)UA_malloc (desc->discoveryUrls[0].length + 1);
      memcpy (url, desc->discoveryUrls[0].data, desc->discoveryUrls[0].length);
      url[desc->discoveryUrls[0].length] = '\0';

      UA_LOG_INFO (UA_Log_Stdout, UA_LOGCATEGORY_CLIENT,
                   "Connecting to %s to read current time...", url);

      UA_StatusCode retval;
      if (username)
        retval = UA_Client_connectUsername (client, url, username, password);
      else
        retval = UA_Client_connect (client, url);
      UA_free (url);
      if (retval != UA_STATUSCODE_GOOD)
        {
          UA_LOG_ERROR (UA_Log_Stdout, UA_LOGCATEGORY_CLIENT,
                        "Could not connect: %s", UA_StatusCode_name (retval));
          continue;
        }

      UA_Variant value;
      UA_Variant_init (&value);

      const UA_NodeId nodeId = UA_NS0ID (SERVER_SERVERSTATUS_CURRENTTIME);
      retval = UA_Client_readValueAttribute (client, nodeId, &value);

      if (retval == UA_STATUSCODE_GOOD
          && UA_Variant_hasScalarType (&value, &UA_TYPES[UA_TYPES_DATETIME]))
        {
          UA_DateTime raw_date = *(UA_DateTime *)value.data;
          UA_DateTimeStruct dts = UA_DateTime_toStruct (raw_date);
          UA_LOG_INFO (UA_Log_Stdout, UA_LOGCATEGORY_APPLICATION,
                       "date is: %u-%u-%u %u:%u:%u.%03u", dts.day, dts.month,
                       dts.year, dts.hour, dts.min, dts.sec, dts.milliSec);
        }
      else
        {
          UA_LOG_ERROR (UA_Log_Stdout, UA_LOGCATEGORY_CLIENT,
                        "Could not read current time: %s",
                        UA_StatusCode_name (retval));
        }

      UA_Variant_clear (&value);
      UA_Client_disconnect (client);
    }
}

/* ========================================================================
 * Main
 * ======================================================================== */

int
main (int argc, char **argv)
{
  if (argc < 2 || argc > 3)
    {
      UA_LOG_FATAL (UA_Log_Stdout, UA_LOGCATEGORY_USERLAND,
                    "Usage: %s <config-file> [log-level]", argv[0]);
      return EXIT_FAILURE;
    }

  const char *logLevelStr = (argc == 3) ? argv[2] : "info";
  int logLevel = parseLogLevel (logLevelStr);
  if (logLevel < 0)
    {
      UA_LOG_FATAL (UA_Log_Stdout, UA_LOGCATEGORY_USERLAND,
                    "Unknown log level: %s "
                    "(expected trace, debug, info, warning, error, fatal)",
                    logLevelStr);
      return EXIT_FAILURE;
    }

  Config cfg;
  if (configLoad (argv[1], &cfg) != 0)
    return EXIT_FAILURE;

  /* ---- Shared keys ---- */

  const char *discoveryServerEndpoint
      = configRequire (&cfg, "discoveryEndpoint", "ClientFindServers");
  const char *applicationUri
      = configRequire (&cfg, "applicationUri", "ClientFindServers");

  if (!discoveryServerEndpoint || !applicationUri)
    {
      configFree (&cfg);
      return EXIT_FAILURE;
    }

  /* ---- Discovery-side config (LDS connection) ---- */

  const char *discCertPath
      = configRequire (&cfg, "discoveryCertificate", "ClientFindServers");
  const char *discKeyPath
      = configRequire (&cfg, "discoveryPrivateKey", "ClientFindServers");
  const char *discSecModeStr
      = configRequire (&cfg, "discoverySecurityMode", "ClientFindServers");
  const char *discSecPolStr
      = configRequire (&cfg, "discoverySecurityPolicy", "ClientFindServers");
  const char *discAuthMode
      = configRequire (&cfg, "discoveryAuthMode", "ClientFindServers");

  if (!discCertPath || !discKeyPath || !discSecModeStr || !discSecPolStr
      || !discAuthMode)
    {
      configFree (&cfg);
      return EXIT_FAILURE;
    }

  UA_MessageSecurityMode discSecMode = parseSecurityMode (discSecModeStr);
  if (discSecMode == UA_MESSAGESECURITYMODE_INVALID)
    {
      UA_LOG_FATAL (UA_Log_Stdout, UA_LOGCATEGORY_USERLAND,
                    "Unknown discovery security mode: %s", discSecModeStr);
      configFree (&cfg);
      return EXIT_FAILURE;
    }

  const char *discSecPolUri = resolveSecurityPolicyUri (discSecPolStr);
  if (!discSecPolUri)
    {
      UA_LOG_FATAL (UA_Log_Stdout, UA_LOGCATEGORY_USERLAND,
                    "Unknown discovery security policy: %s", discSecPolStr);
      configFree (&cfg);
      return EXIT_FAILURE;
    }

  /* ---- Server-side config (connections to discovered servers) ---- */

  const char *srvCertPath
      = configRequire (&cfg, "serverCertificate", "ClientFindServers");
  const char *srvKeyPath
      = configRequire (&cfg, "serverPrivateKey", "ClientFindServers");
  const char *srvSecModeStr
      = configRequire (&cfg, "serverSecurityMode", "ClientFindServers");
  const char *srvSecPolStr
      = configRequire (&cfg, "serverSecurityPolicy", "ClientFindServers");
  const char *srvAuthMode
      = configRequire (&cfg, "serverAuthMode", "ClientFindServers");

  if (!srvCertPath || !srvKeyPath || !srvSecModeStr || !srvSecPolStr
      || !srvAuthMode)
    {
      configFree (&cfg);
      return EXIT_FAILURE;
    }

  UA_MessageSecurityMode srvSecMode = parseSecurityMode (srvSecModeStr);
  if (srvSecMode == UA_MESSAGESECURITYMODE_INVALID)
    {
      UA_LOG_FATAL (UA_Log_Stdout, UA_LOGCATEGORY_USERLAND,
                    "Unknown server security mode: %s", srvSecModeStr);
      configFree (&cfg);
      return EXIT_FAILURE;
    }

  const char *srvSecPolUri = resolveSecurityPolicyUri (srvSecPolStr);
  if (!srvSecPolUri)
    {
      UA_LOG_FATAL (UA_Log_Stdout, UA_LOGCATEGORY_USERLAND,
                    "Unknown server security policy: %s", srvSecPolStr);
      configFree (&cfg);
      return EXIT_FAILURE;
    }

  /* ---- Server-side auth ---- */

  const char *srvUsername = NULL, *srvPassword = NULL;

  if (strcmp (srvAuthMode, "anonymous") == 0)
    {
      /* No credentials needed */
    }
  else if (strcmp (srvAuthMode, "user") == 0)
    {
      srvUsername
          = configRequire (&cfg, "serverUsername", "ClientFindServers");
      srvPassword
          = configRequire (&cfg, "serverPassword", "ClientFindServers");
      if (!srvUsername || !srvPassword)
        {
          configFree (&cfg);
          return EXIT_FAILURE;
        }
    }
  else
    {
      UA_LOG_FATAL (UA_Log_Stdout, UA_LOGCATEGORY_USERLAND,
                    "Unknown server auth mode: %s "
                    "(expected 'anonymous' or 'user')",
                    srvAuthMode);
      configFree (&cfg);
      return EXIT_FAILURE;
    }

  /* ---- Trust lists ---- */

  char **discTrustPaths = NULL;
  size_t discTrustSize = 0;
  configGetAll (&cfg, "discoveryTrustList", &discTrustPaths, &discTrustSize);

  char **srvTrustPaths = NULL;
  size_t srvTrustSize = 0;
  configGetAll (&cfg, "serverTrustList", &srvTrustPaths, &srvTrustSize);

  /* ---- Create discovery client (LDS) ---- */

  UA_Client *discoveryClient = UA_Client_new ();
  UA_StatusCode retval = createSecureClientConfig (
      UA_Client_getConfig (discoveryClient), applicationUri, discCertPath,
      discKeyPath, discTrustPaths, discTrustSize, discSecMode, discSecPolUri);
  if (retval != UA_STATUSCODE_GOOD)
    {
      UA_Client_delete (discoveryClient);
      free (discTrustPaths);
      free (srvTrustPaths);
      configFree (&cfg);
      return EXIT_FAILURE;
    }
  UA_Client_getConfig (discoveryClient)->logging->context
      = (void *)(uintptr_t)logLevel;

  /* ---- Create server client (discovered servers) ---- */

  UA_Client *serverClient = UA_Client_new ();
  retval = createSecureClientConfig (
      UA_Client_getConfig (serverClient), applicationUri, srvCertPath,
      srvKeyPath, srvTrustPaths, srvTrustSize, srvSecMode, srvSecPolUri);
  if (retval != UA_STATUSCODE_GOOD)
    {
      UA_Client_delete (discoveryClient);
      UA_Client_delete (serverClient);
      free (discTrustPaths);
      free (srvTrustPaths);
      configFree (&cfg);
      return EXIT_FAILURE;
    }
  UA_Client_getConfig (serverClient)->logging->context
      = (void *)(uintptr_t)logLevel;

  /* ---- Discovery calls (use discoveryClient) ---- */

  UA_ApplicationDescription *applicationDescriptionArray = NULL;
  size_t applicationDescriptionArraySize = 0;

  retval = findServers (discoveryClient, discoveryServerEndpoint,
                        &applicationDescriptionArraySize,
                        &applicationDescriptionArray);
  if (retval != UA_STATUSCODE_GOOD)
    {
      UA_Client_delete (discoveryClient);
      UA_Client_delete (serverClient);
      free (discTrustPaths);
      free (srvTrustPaths);
      configFree (&cfg);
      return EXIT_FAILURE;
    }

  getServersEndpoints (discoveryClient, applicationDescriptionArray,
                       applicationDescriptionArraySize);

  /* ---- Server calls (use serverClient) ---- */

  readServerTime (serverClient, applicationDescriptionArray,
                  applicationDescriptionArraySize, srvUsername, srvPassword);

  /* ---- Cleanup ---- */

  UA_Client_delete (discoveryClient);
  UA_Client_delete (serverClient);
  UA_Array_delete (applicationDescriptionArray,
                   applicationDescriptionArraySize,
                   &UA_TYPES[UA_TYPES_APPLICATIONDESCRIPTION]);
  free (discTrustPaths);
  free (srvTrustPaths);
  configFree (&cfg);

  return EXIT_SUCCESS;
}