BIP: 15
  Layer: Applications
  Title: Aliases
  Author: Amir Taaki 
  Comments-Summary: No comments yet.
  Comments-URI: https://github.com/bitcoin/bips/wiki/Comments:BIP-0015
  Status: Deferred
  Type: Standards Track
  Created: 2011-12-10

// resolv.h
#ifndef NOMRESOLV_H__
#define NOMRESOLV_H__

#include 
#include "curl/curl.h"

using std::string;

/*

This class resolves against a server to lookup addresses.
To not conflict with the bitcoin addresses, we refer here to people's handles.
A handle is of the form:

   genjix@foo.org

Most characters are valid for the username + password (and handled accordingly), but the domain follows usual web standards. It is possible to affix a path if needed,

   genjix@bar.com/path/to/

*/

class NameResolutionService
{
public:
    NameResolutionService();
    ~NameResolutionService();

    // Three main methods map to RPC actions.
    string FetchAddress(const string& strHandle, string& strAddy);

private:
    // A POST block
    class PostVariables
    {
    public:
        PostVariables();
        ~PostVariables();
        // Add a new key, value pair
        bool Add(const string& strKey, const string& strVal);
        curl_httppost* operator()() const;
    private:
        // CURL stores POST blocks as linked lists.
        curl_httppost *pBegin, *pEnd;
    };

    // Explodes user@domain => user, domain
    static void ExplodeHandle(const string& strHandle, string& strNickname, string& strDomain);
    // Perform the HTTP request. Returns true on success.
    bool Perform();

    // CURL error message
    char pErrorBuffer[CURL_ERROR_SIZE];
    // CURL response
    string strBuffer;
    // CURL handle
    CURL *curl;
};

#endif

// resolv.cpp
#include "resolv.h"

#include 

#include "access.h"

// callback used to write response from the server
static int writer(char *pData, size_t nSize, size_t nNmemb, std::string *pBuffer)
{
  int nResult = 0;
  if (pBuffer != NULL)
  {
    pBuffer->append(pData, nSize * nNmemb);
    // How much did we write?
    nResult = nSize * nNmemb;
  }
  return nResult;
}

NameResolutionService::NameResolutionService()
{
    // Initialise CURL with our various options.
    curl = curl_easy_init();
    // This goes first in case of any problems below. We get an error message.
    curl_easy_setopt(curl, CURLOPT_ERRORBUFFER, pErrorBuffer);
    // fail when server sends >= 404
    curl_easy_setopt(curl, CURLOPT_FAILONERROR, 1);
    curl_easy_setopt(curl, CURLOPT_HEADER, 0);
    curl_easy_setopt(curl, CURLOPT_FOLLOWLOCATION, 1);
    curl_easy_setopt(curl, CURLOPT_POSTREDIR, CURL_REDIR_POST_302);
    curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, writer);
    curl_easy_setopt(curl, CURLOPT_USE_SSL, CURLUSESSL_TRY);
    curl_easy_setopt(curl, CURLOPT_SSL_VERIFYPEER, 1);
    // server response goes in strBuffer
    curl_easy_setopt(curl, CURLOPT_WRITEDATA, &strBuffer);
    pErrorBuffer[0] = '\0';
}
NameResolutionService::~NameResolutionService()
{
    curl_easy_cleanup(curl);
}

void NameResolutionService::ExplodeHandle(const string& strHandle, string& strNickname, string& strDomain)
{
    // split address at @ furthrest to the right
    size_t nPosAtsym = strHandle.rfind('@');
    strNickname = strHandle.substr(0, nPosAtsym);
    strDomain = strHandle.substr(nPosAtsym + 1, strHandle.size());
}
bool NameResolutionService::Perform()
{
    // Called after everything has been setup. This actually does the request.
    CURLcode result = curl_easy_perform(curl);
    return (result == CURLE_OK);
}

string NameResolutionService::FetchAddress(const string& strHandle, string& strAddy)
{
    // GET is defined for 'getting' data, so we use GET for the low risk fetching of people's addresses
    if (!curl)
        // For some reason CURL didn't start...
        return pErrorBuffer;
    // Expand the handle
    string strNickname, strDomain;
    ExplodeHandle(strHandle, strNickname, strDomain);
    // url encode the nickname for get request
    const char* pszEncodedNick = curl_easy_escape(curl, strNickname.c_str(), strNickname.size());
    if (!pszEncodedNick)
        return "Unable to encode nickname.";
    // construct url for GET request
    string strRequestUrl = strDomain + "/bitcoin-alias/?handle=" + pszEncodedNick;
    // Pass URL to CURL
    curl_easy_setopt(curl, CURLOPT_URL, strRequestUrl.c_str());
    if (!Perform())
        return pErrorBuffer;
    // Server should respond with a JSON that has the address in.
    strAddy = strBuffer;
    return "";  // no error
}

NameResolutionService::PostVariables::PostVariables()
{
    // pBegin/pEnd *must* be null before calling curl_formadd
    pBegin = NULL;
    pEnd = NULL;
}
NameResolutionService::PostVariables::~PostVariables()
{
    curl_formfree(pBegin);
}
bool NameResolutionService::PostVariables::Add(const string& strKey, const string& strVal)
{
    // Copy strings to this block. Return true on success.
    return curl_formadd(&pBegin, &pEnd, CURLFORM_COPYNAME, strKey.c_str(), CURLFORM_COPYCONTENTS, strVal.c_str(), CURLFORM_END) == CURL_FORMADD_OK;
}

curl_httppost* NameResolutionService::PostVariables::operator()() const
{
    return pBegin;
}



// rpc.cpp
...

const Object CheckMaybeThrow(const string& strJsonIn)
{
    // Parse input JSON
    Value valRequest;
    if (!read_string(strJsonIn, valRequest) || valRequest.type() != obj_type)
        throw JSONRPCError(-32700, "Parse error");
    const Object& request = valRequest.get_obj();
    // Now check for a key called "error"
    const Value& error  = find_value(request, "error");
    // It's an error JSON! so propagate the error.
    if (error.type() != null_type)
        throw JSONRPCError(-4, error.get_str());
    // Return JSON object
    return request;
}

const string CollectAddress(const string& strIn)
{
    // If the handle does not have an @ in it, then it's a normal base58 bitcoin address
    if (strIn.find('@') == (size_t)-1)
        return strIn;

    // Open the lookup service
    NameResolutionService ns;
    // We established that the input string is not a BTC address, so we use it as a handle now.
    string strHandle = strIn, strAddy;
    string strError = ns.FetchAddress(strHandle, strAddy);
    if (!strError.empty())
        throw JSONRPCError(-4, strError);

    const Object& request(CheckMaybeThrow(strAddy));
    // Get the BTC address from the JSON
    const Value& address = find_value(request, "address");
    if (address.type() != str_type)
        throw JSONRPCError(-32600, "Server responded with malformed reply.");
    return address.get_str();
}

// Named this way to prevent possible conflicts.
Value rpc_send(const Array& params, bool fHelp)
{
    if (fHelp || params.size() != 2)
        throw runtime_error(
            "send  \n"
            " is a real and is rounded to the nearest 0.01");

    // Intelligent function which looks up address given handle, or returns address
    string strAddy = CollectAddress(params[0].get_str());
    int64 nAmount = AmountFromValue(params[1]);
    // Do the send
    CWalletTx wtx;
    string strError = SendMoneyToBitcoinAddress(strAddy, nAmount, wtx);
    if (!strError.empty())
        throw JSONRPCError(-4, strError);
    return wtx.GetHash().GetHex();
}

...