/*
 * s3fs - FUSE-based file system backed by Amazon S3
 *
 * Copyright 2007-2008 Randy Rizun <rrizun@gmail.com>
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
 */

#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#include <string.h>
#include <unistd.h>
#include <fcntl.h>
#include <dirent.h>
#include <errno.h>
#include <syslog.h>
#include <pthread.h>
#include <curl/curl.h>
#include <openssl/bio.h>
#include <openssl/buffer.h>
#include <openssl/evp.h>
#include <openssl/hmac.h>
#include <openssl/md5.h>
#include <iostream>
#include <fstream>
#include <string>
#include <map>

#include "curl.h"
#include "string_util.h"

using namespace std;

pthread_mutex_t curl_handles_lock;
std::map<CURL*, time_t> curl_times;
std::map<CURL*, progress_t> curl_progress;
std::string curl_ca_bundle;

class auto_curl_slist {
 public:
  auto_curl_slist() : slist(0) { }
  ~auto_curl_slist() { curl_slist_free_all(slist); }

  struct curl_slist* get() const { return slist; }

  void append(const string& s) {
    slist = curl_slist_append(slist, s.c_str());
  }

 private:
  struct curl_slist* slist;
};

static size_t header_callback(void *data, size_t blockSize, size_t numBlocks, void *userPtr) {
  headers_t* headers = reinterpret_cast<headers_t*>(userPtr);
  string header(reinterpret_cast<char*>(data), blockSize * numBlocks);
  string key;
  stringstream ss(header);
  if (getline(ss, key, ':')) {
    string value;
    getline(ss, value);
    (*headers)[key] = trim(value);
  }
  return blockSize * numBlocks;
}

CURL *create_curl_handle(void) {
  time_t now;
  CURL *curl_handle;

  pthread_mutex_lock(&curl_handles_lock);
  curl_handle = curl_easy_init();
  curl_easy_reset(curl_handle);
  curl_easy_setopt(curl_handle, CURLOPT_NOSIGNAL, 1);
  curl_easy_setopt(curl_handle, CURLOPT_FOLLOWLOCATION, true);
  curl_easy_setopt(curl_handle, CURLOPT_CONNECTTIMEOUT, connect_timeout);
  curl_easy_setopt(curl_handle, CURLOPT_NOPROGRESS, 0);
  curl_easy_setopt(curl_handle, CURLOPT_PROGRESSFUNCTION, my_curl_progress);
  curl_easy_setopt(curl_handle, CURLOPT_PROGRESSDATA, curl_handle);
  // curl_easy_setopt(curl_handle, CURLOPT_FORBID_REUSE, 1);
  
  if(ssl_verify_hostname.substr(0,1) == "0")
    curl_easy_setopt(curl_handle, CURLOPT_SSL_VERIFYHOST, 0);
  if(curl_ca_bundle.size() != 0)
    curl_easy_setopt(curl_handle, CURLOPT_CAINFO, curl_ca_bundle.c_str());

  now = time(0);
  curl_times[curl_handle] = now;
  curl_progress[curl_handle] = progress_t(-1, -1);
  pthread_mutex_unlock(&curl_handles_lock);

  return curl_handle;
}

void destroy_curl_handle(CURL *curl_handle) {
  if(curl_handle != NULL) {
    pthread_mutex_lock(&curl_handles_lock);
    curl_times.erase(curl_handle);
    curl_progress.erase(curl_handle);
    curl_easy_cleanup(curl_handle);
    pthread_mutex_unlock(&curl_handles_lock);
  }

  return;
}

int curl_delete(const char *path) {
  int result;
  string date;
  string url;
  string my_url;
  string resource;
  auto_curl_slist headers;
  CURL *curl = NULL;

  resource = urlEncode(service_path + bucket + path);
  url = host + resource;
  date = get_date();

  headers.append("Date: " + date);
  headers.append("Content-Type: ");
  if(public_bucket.substr(0,1) != "1")
    headers.append("Authorization: AWS " + AWSAccessKeyId + ":" +
      calc_signature("DELETE", "", date, headers.get(), resource));

  my_url = prepare_url(url.c_str());
  curl = create_curl_handle();
  curl_easy_setopt(curl, CURLOPT_CUSTOMREQUEST, "DELETE");
  curl_easy_setopt(curl, CURLOPT_HTTPHEADER, headers.get());
  curl_easy_setopt(curl, CURLOPT_URL, my_url.c_str());
  result = my_curl_easy_perform(curl);
  destroy_curl_handle(curl);

  return result;
}

int curl_get_headers(const char *path, headers_t &meta) {
  int result;
  CURL *curl;

  if(foreground)
    printf("  curl_headers[path=%s]\n", path);

  string resource(urlEncode(service_path + bucket + path));
  string url(host + resource);

  headers_t responseHeaders;
  curl = create_curl_handle();
  curl_easy_setopt(curl, CURLOPT_NOBODY, true);   // HEAD
  curl_easy_setopt(curl, CURLOPT_FILETIME, true); // Last-Modified
  curl_easy_setopt(curl, CURLOPT_HEADERDATA, &responseHeaders);
  curl_easy_setopt(curl, CURLOPT_HEADERFUNCTION, header_callback);

  auto_curl_slist headers;
  string date = get_date();
  headers.append("Date: " + date);
  headers.append("Content-Type: ");
  if(public_bucket.substr(0,1) != "1") {
    headers.append("Authorization: AWS " + AWSAccessKeyId + ":" +
      calc_signature("HEAD", "", date, headers.get(), resource));
  }
  curl_easy_setopt(curl, CURLOPT_HTTPHEADER, headers.get());
  string my_url = prepare_url(url.c_str());
  curl_easy_setopt(curl, CURLOPT_URL, my_url.c_str());
  result = my_curl_easy_perform(curl);
  destroy_curl_handle(curl);

  if(result != 0)
     return result;

  // file exists in s3
  // fixme: clean this up.
  for (headers_t::iterator iter = responseHeaders.begin(); iter != responseHeaders.end(); ++iter) {
    string key = (*iter).first;
    string value = (*iter).second;
    if(key == "Content-Type")
      meta[key] = value;
    if(key == "Content-Length")
      meta[key] = value;
    if(key == "ETag")
      meta[key] = value;
    if(key == "Last-Modified")
      meta[key] = value;
    if(key.substr(0, 5) == "x-amz")
      meta[key] = value;
  }

  return 0;
}

/**
 * @return fuse return code
 */
int my_curl_easy_perform(CURL* curl, BodyStruct* body, FILE* f) {
  char url[256];
  time_t now;
  char* ptr_url = url;
  curl_easy_getinfo(curl, CURLINFO_EFFECTIVE_URL , &ptr_url);

  if(debug)
    syslog(LOG_DEBUG, "connecting to URL %s", ptr_url);

  // curl_easy_setopt(curl, CURLOPT_VERBOSE, true);
  if(ssl_verify_hostname.substr(0,1) == "0")
    curl_easy_setopt(curl, CURLOPT_SSL_VERIFYHOST, 0);

  if(curl_ca_bundle.size() != 0)
    curl_easy_setopt(curl, CURLOPT_CAINFO, curl_ca_bundle.c_str());

  long responseCode;

  // 1 attempt + retries...
  int t = retries + 1;
  while (t-- > 0) {
    if (f) {
      rewind(f);
    }
    CURLcode curlCode = curl_easy_perform(curl);

    switch (curlCode) {
      case CURLE_OK:
        // Need to look at the HTTP response code

        if (curl_easy_getinfo(curl, CURLINFO_RESPONSE_CODE, &responseCode) != 0) {
          syslog(LOG_ERR, "curl_easy_getinfo failed while trying to retrieve HTTP response code");
          return -EIO;
        }
        
        if(debug)
          syslog(LOG_DEBUG, "HTTP response code %ld", responseCode);

        if (responseCode < 400) {
          return 0;
        }

        if (responseCode >= 500) {
          syslog(LOG_ERR, "###HTTP response=%ld", responseCode);
          sleep(4);
          break; 
        }

        // Service response codes which are >= 400 && < 500
        switch(responseCode) {
          case 400:
            if(debug) syslog(LOG_ERR, "HTTP response code 400 was returned");
            if(body) {
              if(body->size && debug) {
                syslog(LOG_ERR, "Body Text: %s", body->text);
              }
            }
            if(debug) syslog(LOG_DEBUG, "Now returning EIO");
            return -EIO;

          case 403:
            if(debug) syslog(LOG_ERR, "HTTP response code 403 was returned");
            if(body)
              if(body->size && debug)
                syslog(LOG_ERR, "Body Text: %s", body->text);
            return -EPERM;

          case 404:
            if(debug) syslog(LOG_DEBUG, "HTTP response code 404 was returned");
            if(body) {
              if(body->size && debug) {
                syslog(LOG_DEBUG, "Body Text: %s", body->text);
              }
            }
            if(debug) syslog(LOG_DEBUG, "Now returning ENOENT");
            return -ENOENT;

          default:
            syslog(LOG_ERR, "###response=%ld", responseCode);
            printf("responseCode %ld\n", responseCode);
            if(body) {
              if(body->size) {
                printf("Body Text %s\n", body->text);
              }
            }
            return -EIO;
        }
        break;

      case CURLE_WRITE_ERROR:
        syslog(LOG_ERR, "### CURLE_WRITE_ERROR");
        sleep(2);
        break; 

      case CURLE_OPERATION_TIMEDOUT:
        syslog(LOG_ERR, "### CURLE_OPERATION_TIMEDOUT");
        sleep(2);
        break; 

      case CURLE_COULDNT_RESOLVE_HOST:
        syslog(LOG_ERR, "### CURLE_COULDNT_RESOLVE_HOST");
        sleep(2);
        break; 

      case CURLE_COULDNT_CONNECT:
        syslog(LOG_ERR, "### CURLE_COULDNT_CONNECT");
        sleep(4);
        break; 

      case CURLE_GOT_NOTHING:
        syslog(LOG_ERR, "### CURLE_GOT_NOTHING");
        sleep(4);
        break; 

      case CURLE_ABORTED_BY_CALLBACK:
        syslog(LOG_ERR, "### CURLE_ABORTED_BY_CALLBACK");
        sleep(4);
        now = time(0);
        curl_times[curl] = now;
        break; 

      case CURLE_PARTIAL_FILE:
        syslog(LOG_ERR, "### CURLE_PARTIAL_FILE");
        sleep(4);
        break; 

      case CURLE_SEND_ERROR:
        syslog(LOG_ERR, "### CURLE_SEND_ERROR");
        sleep(2);
        break;

      case CURLE_RECV_ERROR:
        syslog(LOG_ERR, "### CURLE_RECV_ERROR");
        sleep(2);
        break;

      case CURLE_SSL_CACERT:
        // try to locate cert, if successful, then set the
        // option and continue
        if (curl_ca_bundle.size() == 0) {
           locate_bundle();
           if (curl_ca_bundle.size() != 0) {
              t++;
              curl_easy_setopt(curl, CURLOPT_CAINFO, curl_ca_bundle.c_str());
              continue;
           }
        }
        syslog(LOG_ERR, "curlCode: %i  msg: %s", curlCode,
           curl_easy_strerror(curlCode));;
        fprintf (stderr, "%s: curlCode: %i -- %s\n", 
           program_name.c_str(),
           curlCode,
           curl_easy_strerror(curlCode));
        exit(EXIT_FAILURE);
        break;

#ifdef CURLE_PEER_FAILED_VERIFICATION
      case CURLE_PEER_FAILED_VERIFICATION:
        first_pos = bucket.find_first_of(".");
        if (first_pos != string::npos) {
          fprintf (stderr, "%s: curl returned a CURL_PEER_FAILED_VERIFICATION error\n", program_name.c_str());
          fprintf (stderr, "%s: security issue found: buckets with periods in their name are incompatible with https\n", program_name.c_str());
          fprintf (stderr, "%s: This check can be over-ridden by using the -o ssl_verify_hostname=0\n", program_name.c_str());
          fprintf (stderr, "%s: The certificate will still be checked but the hostname will not be verified.\n", program_name.c_str());
          fprintf (stderr, "%s: A more secure method would be to use a bucket name without periods.\n", program_name.c_str());
        } else {
          fprintf (stderr, "%s: my_curl_easy_perform: curlCode: %i -- %s\n", 
             program_name.c_str(),
             curlCode,
             curl_easy_strerror(curlCode));
        }
        exit(EXIT_FAILURE);
        break;
#endif

      // This should be invalid since curl option HTTP FAILONERROR is now off
      case CURLE_HTTP_RETURNED_ERROR:
        syslog(LOG_ERR, "### CURLE_HTTP_RETURNED_ERROR");

        if (curl_easy_getinfo(curl, CURLINFO_RESPONSE_CODE, &responseCode) != 0) {
          return -EIO;
        }
        syslog(LOG_ERR, "###response=%ld", responseCode);

        // Let's try to retrieve the 

        if (responseCode == 404) {
          return -ENOENT;
        }
        if (responseCode < 500) {
          return -EIO;
        }
        break;

      // Unknown CURL return code
      default:
        syslog(LOG_ERR, "###curlCode: %i  msg: %s", curlCode,
           curl_easy_strerror(curlCode));;
        exit(EXIT_FAILURE);
        break;
    }
    syslog(LOG_ERR, "###retrying...");
  }
  syslog(LOG_ERR, "###giving up");
  return -EIO;
}

// libcurl callback
size_t WriteMemoryCallback(void *ptr, size_t blockSize, size_t numBlocks, void *data) {
  size_t realsize = blockSize * numBlocks;
  struct BodyStruct *mem = (struct BodyStruct *)data;
 
  mem->text = (char *)realloc(mem->text, mem->size + realsize + 1);
  if(mem->text == NULL) {
    /* out of memory! */ 
    fprintf(stderr, "not enough memory (realloc returned NULL)\n");
    exit(EXIT_FAILURE);
  }
 
  memcpy(&(mem->text[mem->size]), ptr, realsize);
  mem->size += realsize;
  mem->text[mem->size] = 0;

  return realsize;
}

// read_callback
// http://curl.haxx.se/libcurl/c/post-callback.html
size_t read_callback(void *ptr, size_t size, size_t nmemb, void *userp) {
  struct WriteThis *pooh = (struct WriteThis *)userp;
 
  if(size*nmemb < 1)
    return 0;
 
  if(pooh->sizeleft) {
    *(char *)ptr = pooh->readptr[0]; /* copy one single byte */ 
    pooh->readptr++;                 /* advance pointer */ 
    pooh->sizeleft--;                /* less data left */ 
    return 1;                        /* we return 1 byte at a time! */ 
  }
 
  return 0;                          /* no more data left to deliver */ 
}

// homegrown timeout mechanism
int my_curl_progress(
    void *clientp, double dltotal, double dlnow, double ultotal, double ulnow) {
  CURL* curl = static_cast<CURL*>(clientp);

  time_t now = time(0);
  progress_t p(dlnow, ulnow);

  pthread_mutex_lock(&curl_handles_lock);

  // any progress?
  if(p != curl_progress[curl]) {
    // yes!
    curl_times[curl] = now;
    curl_progress[curl] = p;
  } else {
    // timeout?
    if (now - curl_times[curl] > readwrite_timeout) {
      pthread_mutex_unlock( &curl_handles_lock );

      syslog(LOG_ERR, "timeout  now: %li  curl_times[curl]: %lil  readwrite_timeout: %li",
                      (long int)now, curl_times[curl], (long int)readwrite_timeout);

      return CURLE_ABORTED_BY_CALLBACK;
    }
  }

  pthread_mutex_unlock(&curl_handles_lock);
  return 0;
}

/**
 * Returns the Amazon AWS signature for the given parameters.
 *
 * @param method e.g., "GET"
 * @param content_type e.g., "application/x-directory"
 * @param date e.g., get_date()
 * @param resource e.g., "/pub"
 */
string calc_signature(
    string method, string content_type, string date, curl_slist* headers, string resource) {
  int ret;
  int bytes_written;
  int offset;
  int write_attempts = 0;

  string Signature;
  string StringToSign;
  StringToSign += method + "\n";
  StringToSign += "\n"; // md5
  StringToSign += content_type + "\n";
  StringToSign += date + "\n";
  int count = 0;
  if(headers != 0) {
    do {
      if(strncmp(headers->data, "x-amz", 5) == 0) {
        ++count;
        StringToSign += headers->data;
        StringToSign += 10; // linefeed
      }
    } while ((headers = headers->next) != 0);
  }

  StringToSign += resource;

  const void* key = AWSSecretAccessKey.data();
  int key_len = AWSSecretAccessKey.size();
  const unsigned char* d = reinterpret_cast<const unsigned char*>(StringToSign.data());
  int n = StringToSign.size();
  unsigned int md_len;
  unsigned char md[EVP_MAX_MD_SIZE];

  HMAC(evp_md, key, key_len, d, n, md, &md_len);

  BIO* b64 = BIO_new(BIO_f_base64());
  BIO* bmem = BIO_new(BIO_s_mem());
  b64 = BIO_push(b64, bmem);

  offset = 0;
  for(;;) {
    bytes_written = BIO_write(b64, &(md[offset]), md_len);
    write_attempts++;
    // -1 indicates that an error occurred, or a temporary error, such as
    // the server is busy, occurred and we need to retry later.
    // BIO_write can do a short write, this code addresses this condition
    if(bytes_written <= 0) {
      // Indicates whether a temporary error occurred or a failure to
      // complete the operation occurred
      if ((ret = BIO_should_retry(b64))) {
        // Wait until the write can be accomplished
        if(write_attempts <= 10)
          continue;

        // Too many write attempts
        syslog(LOG_ERR, "Failure during BIO_write, returning null String");  
        BIO_free_all(b64);
        Signature.clear();
        return Signature;
      } else {
        // If not a retry then it is an error
        syslog(LOG_ERR, "Failure during BIO_write, returning null String");  
        BIO_free_all(b64);
        Signature.clear();
        return Signature;
      }
    }
  
    // The write request succeeded in writing some Bytes
    offset += bytes_written;
    md_len -= bytes_written;
  
    // If there is no more data to write, the request sending has been
    // completed
    if(md_len <= 0)
      break;
  }

  // Flush the data
  ret = BIO_flush(b64);
  if ( ret <= 0) { 
    syslog(LOG_ERR, "Failure during BIO_flush, returning null String");  
    BIO_free_all(b64);
    Signature.clear();
    return Signature;
  } 

  BUF_MEM *bptr;

  BIO_get_mem_ptr(b64, &bptr);

  Signature.resize(bptr->length - 1);
  memcpy(&Signature[0], bptr->data, bptr->length-1);

  BIO_free_all(b64);

  return Signature;
}

void locate_bundle(void) {
  // See if environment variable CURL_CA_BUNDLE is set
  // if so, check it, if it is a good path, then set the
  // curl_ca_bundle variable to it
  char *CURL_CA_BUNDLE; 

  if(curl_ca_bundle.size() == 0) {
    CURL_CA_BUNDLE = getenv("CURL_CA_BUNDLE");
    if(CURL_CA_BUNDLE != NULL)  {
      // check for existance and readability of the file
      ifstream BF(CURL_CA_BUNDLE);
      if(BF.good()) {
         BF.close();
         curl_ca_bundle.assign(CURL_CA_BUNDLE); 
      } else {
        fprintf(stderr, "%s: file specified by CURL_CA_BUNDLE environment variable is not readable\n",
                program_name.c_str());
        exit(EXIT_FAILURE);
      }

      return;
    }
  }

  // not set via environment variable, look in likely locations

  ///////////////////////////////////////////
  // from curl's (7.21.2) acinclude.m4 file
  ///////////////////////////////////////////
  // dnl CURL_CHECK_CA_BUNDLE
  // dnl -------------------------------------------------
  // dnl Check if a default ca-bundle should be used
  // dnl
  // dnl regarding the paths this will scan:
  // dnl /etc/ssl/certs/ca-certificates.crt Debian systems
  // dnl /etc/pki/tls/certs/ca-bundle.crt Redhat and Mandriva
  // dnl /usr/share/ssl/certs/ca-bundle.crt old(er) Redhat
  // dnl /usr/local/share/certs/ca-root.crt FreeBSD
  // dnl /etc/ssl/cert.pem OpenBSD
  // dnl /etc/ssl/certs/ (ca path) SUSE
  ifstream BF("/etc/pki/tls/certs/ca-bundle.crt"); 
  if(BF.good()) {
     BF.close();
     curl_ca_bundle.assign("/etc/pki/tls/certs/ca-bundle.crt"); 
     return;
  }

  return;
}