// Raspberry Pi LPC1114 I/O Processor Expansion Board
// SPI Agent firmware services over HTTP

// Copyright (C)2013-2018, Philip Munts, President, Munts AM Corp.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are met:
//
// * Redistributions of source code must retain the above copyright notice,
//   this list of conditions and the following disclaimer.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
// ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
// LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
// CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
// SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
// INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
// CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
// ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
// POSSIBILITY OF SUCH DAMAGE.

#include <ctype.h>
#include <errno.h>
#include <netdb.h>
#include <regex.h>
#include <stdio.h>
#include <string.h>

#include <curl/curl.h>
#include <spi-agent.h>

#define SERVICENAME	"spiagent-http"

#define REGEX_RESPONSE_TEMPLATE "^[0-9]+,[0-9]+,[0-9]+,[0-9]+,[0-9]+;$"

static regex_t response_template;
static char URL[256];
static CURL *curlhandle;
static char curlerrormsg[CURL_ERROR_SIZE];
static char curlresponse[256];

static size_t min(size_t x, size_t y)
{
  if (x > y)
    return y;
  else
    return x;
}

static void strrtrim(char *s)
{
  int n = strlen(s);

  while ((n > 0) && isspace(s[n-1]))
  {
    s[n-1] = 0;
    n--;
  }
}

static size_t curlcallback(char *ptr, size_t size, size_t nmemb, void *userdata)
{
  size_t count = min(sizeof(curlresponse) - 1, size*nmemb);

  memset(curlresponse, 0, sizeof(curlresponse));
  memcpy(curlresponse, ptr, count);

  return size*nmemb;
}

void spiagent_command_http(SPIAGENT_COMMAND_MSG_t *cmd, SPIAGENT_RESPONSE_MSG_t *resp, int32_t *error)
{
  char query[1024];
  int servererror;

  // Check whether we have an open connection

  if (curlhandle == NULL)
  {
    *error = EBADF;
    return;
  }

  // Build the query string

  snprintf(query, sizeof(query), "%s?%d,%d,%d", URL, cmd->command, cmd->pin, cmd->data);

  // Perform the HTTP transfer

  if (curl_easy_setopt(curlhandle, CURLOPT_URL, query))
  {
#ifdef DEBUG
    fprintf(stderr, "ERROR: curl_easy_setopt() for CURLOPT_URL failed\n");
#endif

    *error = EIO;
    return;
  }

  if (curl_easy_perform(curlhandle))
  {
#ifdef DEBUG
    fprintf(stderr, "ERROR: curl_easy_perform() failed, %s\n", curlerrormsg);
#endif

    *error = EIO;
    return;
  }

  // Sanitize the response

  curlresponse[sizeof(curlresponse)-1] = 0;	// Guarantee NUL terminator
  strrtrim(curlresponse);			// Strip trailing whitespace

  // The query string must be of the form n,n,n,n,n

  if (regexec(&response_template, curlresponse, 0, NULL, 0))
  {
#ifdef DEBUG
    fprintf(stderr, "ERROR: regexec() failed, invalid response\n");
#endif

    *error = EIO;
    return;
  }

  // Decode the query string

  if (sscanf(curlresponse, "%d,%u,%u,%u,%u;", &servererror, &resp->command,
        &resp->pin, &resp->data, &resp->error) != 5)
  {
#ifdef DEBUG
    fprintf(stderr, "ERROR: sscanf() failed, invalid response\n");
#endif

    *error = EIO;
    return;
  }

  // Check for server error

  if (servererror)
  {
#ifdef DEBUG
    fprintf(stderr, "ERROR: server returned error %d\n", servererror);
#endif

    *error = EIO;
    return;
  }

  *error = 0;
}

void spiagent_open_http(const char *servername, int32_t *error)
{
  struct servent *service;
  SPIAGENT_COMMAND_MSG_t cmd;
  SPIAGENT_RESPONSE_MSG_t resp;

  // Check whether we have an open connection

  if (curlhandle != NULL)
  {
    *error = EBUSY;
    return;
  }

  // NULL servername is not allowed

  if (servername == NULL)
  {
#ifdef DEBUG
    fprintf(stderr, "ERROR: server name is NULL\n");
#endif

    *error = EINVAL;
    return;
  }

  // Look up the service

  service = getservbyname(SERVICENAME, "tcp");
  if (service == NULL)
  {
#ifdef DEBUG
    fprintf(stderr, "ERROR: getservbyname() failed, unknown service\n");
#endif
    *error = EIO;
    return;
  }

  // Compile the regular expression template

  if (regcomp(&response_template, REGEX_RESPONSE_TEMPLATE, REG_EXTENDED))
  {
#ifdef DEBUG
    fprintf(stderr, "ERROR: regcomp() failed\n");
#endif

    *error = EIO;
    return;
  }

  // Build the HTTP server URL

  memset(URL, 0, sizeof(URL));
  snprintf(URL, sizeof(URL), "http://%s:%d/SPIAGENT", servername, ntohs(service->s_port));

  // Initialize the curl library

  curlhandle = curl_easy_init();
  if (curlhandle == NULL)
  {
#ifdef DEBUG
    fprintf(stderr, "ERROR: curl_easy_init() failed\n");
#endif

    regfree(&response_template);
    *error = EIO;
    return;
  }

  if (curl_easy_setopt(curlhandle, CURLOPT_ERRORBUFFER, curlerrormsg))
  {
#ifdef DEBUG
    fprintf(stderr, "ERROR: curl_easy_setopt() for CURLOPT_ERRORBUFFER failed\n");
#endif

    regfree(&response_template);
    curl_easy_cleanup(curlhandle);
    curlhandle = NULL;
    *error = EIO;
    return;
  }

  if (curl_easy_setopt(curlhandle, CURLOPT_WRITEFUNCTION, curlcallback))
  {
#ifdef DEBUG
    fprintf(stderr, "ERROR: curl_easy_setopt() for CURLOPT_WRITEFUNCTION failed\n");
#endif

    regfree(&response_template);
    curl_easy_cleanup(curlhandle);
    curlhandle = NULL;
    *error = EIO;
    return;
  }

  // Ping the server

  memset(&cmd, 0, sizeof(cmd));
  cmd.command = SPIAGENT_CMD_NOP;

  memset(&resp, 0, sizeof(resp));

  spiagent_command_http(&cmd, &resp, error);

  if (*error)
  {
#ifdef DEBUG
    fprintf(stderr, "ERROR: spiagent_command_http() failed, error=%d\n", *error);
#endif

    regfree(&response_template);
    curl_easy_cleanup(curlhandle);
    curlhandle = NULL;
    *error = EIO;
    return;
  }

#ifdef DEBUG
  fprintf(stderr, "DEBUG: SPI Agent Firmware version is %d\n", resp.data);
#endif

  *error = 0;
}

void spiagent_close_http(int32_t *error)
{

  // Check whether we have an open connection

  if (curlhandle == NULL)
  {
    *error = EBADF;
    return;
  }

  regfree(&response_template);
  curl_easy_cleanup(curlhandle);
  curlhandle = NULL;
  *error = 0;
}