/*
 * This file is part of the Flowee project
 * Copyright (C) 2019 Tom Zander <tomz@freedommail.ch>
 *
 * 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 3 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, see <http://www.gnu.org/licenses/>.
 */

// #undef	NDEBUG // make assert do something
#include "Flowee.h"

#include "ContextData.h"
#include <boost/algorithm/hex.hpp>
#include <base58.h>
#include <cashaddr.h>
#include <utilstrencodings.h>

namespace {

/* Javascripts ArrayBuffer is almost the same as Flowee's ConstBuffer
 * and technically it is posible to create one ArrayBuffer for one
 * of Flowee's shared buffers. Which may be shared between many ConstBuffer
 * instances and subsequently, many Javascript UInt8Array instances.
 *
 * To do this, however, I need to somehow figure out to reuse a BufferWrap
 * when I see the same share pointer used in a different ConstBuffer.
 * The correct solution for this is to have a map on the context object
 * to remember the Napi::ArrayBuffer instances and make the BufferWrap
 * update that map.
 *
 * This is left for the future, as we already have zero copy, all the way
 * from the network layer to the Javascript layer.
 *
 * Which is pretty decent.
 *
 * Refactoring stuff to pass in the context everywhere is a lot of work
 * and then profiling it to see if the map overhead is keeping the whole
 * actually beneficial is a lot more work...
 */

struct BufferWrap
{
    BufferWrap(const std::shared_ptr<char> &buffer) : buf(buffer) {}
    std::shared_ptr<char> buf;
};

void destructor(Napi::Env, void *bufPtr, void *bufWrap)
{
    (void)bufPtr;
    BufferWrap *w = reinterpret_cast<BufferWrap*>(bufWrap);
    assert(w);
    assert(bufPtr == w->buf.get());
    delete  w;
}

}

Napi::Uint8Array Flowee::wrap(Napi::Env env, const Streaming::ConstBuffer &buffer)
{
    if (buffer.isEmpty())
        return Napi::Uint8Array::New(env, 0);

    BufferWrap *wrap = new BufferWrap(buffer.internal_buffer());
    auto buf = Napi::ArrayBuffer::New(env, const_cast<void*>(reinterpret_cast<const void*>(buffer.begin())),
                                  static_cast<size_t>(buffer.size()), destructor, wrap);
    return Napi::Uint8Array::New(env, static_cast<size_t>(buffer.size()), buf, 0);
}

char nibbleToChar(uint8_t k) {
    k = k & 0xF;
    if (k < 10)
        return char('0' + k);
    return char('a' + k - 10);
}

// custom made since Bitcoin Cash likes the order to be reversed on printing.
Napi::String Flowee::hashToString(Napi::Env env, const Streaming::ConstBuffer &buffer)
{
    if (buffer.isEmpty())
        return Napi::String::New(env, "");
    assert(buffer.size() == 32);
    if (buffer.size() != 32)
        throw std::runtime_error("Internal error (hash invalid size)");

    char buf[65];
    char *ptr = buf;
    for (int i = 31; i >= 0; --i) {
        uint8_t byte = static_cast<uint8_t>(buffer.begin()[i]);
        *ptr = nibbleToChar(byte >> 4);
        ++ptr;
        *ptr = nibbleToChar(byte);
        ++ptr;
    }
    buf[64] = 0;

    return Napi::String::New(env, buf);
}


Napi::Object Flowee::populateTransaction(Napi::Env env, const Blockchain::Transaction *transaction, bool binaryHash)
{
    using boost::algorithm::hex;
    Napi::Object tx = Napi::Object::New(env);

    tx.Set("blockHeight", Napi::Number::From(env, transaction->blockHeight));
    tx.Set("offsetInBlock", Napi::Number::From(env, transaction->offsetInBlock));
    tx.Set("jobId", Napi::Number::From(env, transaction->jobId));
    tx.Set("isCoinbase", Napi::Boolean::From(env, transaction->isCoinbase()));
    tx.Set("fullTxData", wrap(env, transaction->fullTxData));
    tx.Set("txid",
        binaryHash ? wrap(env, transaction->txid) : hashToString(env, transaction->txid));

    Napi::Array inputs = Napi::Array::New(env, transaction->inputs.size());
    for (size_t i = 0 ; i < transaction->inputs.size(); ++i)  {
        const Blockchain::Input &input = transaction->inputs.at(i);
        Napi::Object in = Napi::Object::New(env);
        in.Set("outputIndex", Napi::Number::From(env, input.outIndex));

        in.Set("previousTxid",
                binaryHash ? wrap(env, input.prevTxId) : hashToString(env, input.prevTxId));

        std::string is;
        hex(input.inputScript.begin(), input.inputScript.end(), back_inserter(is));
        in.Set("script", Napi::String::New(env, is));
        in.Set("script-array", wrap(env, input.inputScript));
        inputs[uint32_t(i)] = in;
    }
    tx.Set("inputs", inputs);

    Napi::Array outputs = Napi::Array::New(env, transaction->outputs.size());
    for (size_t i = 0 ; i < transaction->outputs.size(); ++i)  {
        const Blockchain::Output &output = transaction->outputs.at(i);
        Napi::Object out = Napi::Object::New(env);
        out.Set("index", Napi::Number::From(env, output.index));
        out.Set("amount", Napi::Number::From(env, output.amount));
        switch (output.type) {
        case Blockchain::Output::Nothing: break;
        case Blockchain::Output::FullScript: {
            out.Set("script-array", wrap(env, output.outScript));
            std::string s;
            hex(output.outScript.begin(), output.outScript.end(), back_inserter(s));
            out.Set("script", Napi::String::New(env, s));
            break;
        }
        case Blockchain::Output::OnlyAddress: {
            // TODO we assume we use main-chain addresses here.
            // maybe useful to ask the hub which chain it is on?
            const std::string cashAddress = CashAddress::encodeCashAddr("bitcoincash", { CashAddress::PUBKEY_TYPE,
                std::vector<uint8_t>(output.outScript.begin(), output.outScript.end()) });
            out.Set("address", cashAddress);
            out.Set("address-array", wrap(env, output.outScript));
            break;
        }
        default:
            assert(false);
        }
        outputs[uint32_t(i)] = out;
    }
    tx.Set("outputs", outputs);

    return tx;
}

Flowee::PromiseCallback::PromiseCallback(Napi::Env env)
    : p(Napi::Promise::Deferred::New(env))
{
}

void Flowee::PromiseCallback::resolve(Napi::Value value)
{
    if (!present)
        return;
    assert(!value.IsNull()); // null values make Resolve below throw
    present = false;
    p.Resolve(value);
}

Napi::Promise Flowee::PromiseCallback::promise(Napi::Env env)
{
    p = Napi::Promise::Deferred::New(env);
    present = true;
    return p.Promise();
}

void Flowee::PromiseCallback::reject(Napi::Value value)
{
    if (!present)
        return;
    assert(!value.IsNull()); // null values make Reject below throw
    present = false;
    p.Reject(value);
}

Streaming::ConstBuffer Flowee::hexStringToBuffer(const std::string &hash)
{
    size_t i = 0;
    if (hash.size() == 66) {
        if (hash[0] == '0' && (hash[1] == 'x' || hash[1] == 'X')) {
            i = 2;
        } else {
            return Streaming::ConstBuffer(); // invalid input
        }
    } else if (hash.size() != 64) { // invalid input
        return Streaming::ConstBuffer(); // invalid input
    }

    Streaming::BufferPool pool(32);
    int i2 = 31; // back to front
    while (i < hash.size()) {
        const int8_t k = hash[i];
        const uint8_t v = static_cast<uint8_t>(HexDigit(k));
        if (k > 'f' || v == 0xFF)
            return Streaming::ConstBuffer(); // invalid input
        if ((i % 2) == 0) {
            pool.begin()[i2] = static_cast<char>(v << 4);
        } else {
            pool.begin()[i2--] += v;
        }
        ++i;
    }
    return pool.commit(32);
}


Streaming::ConstBuffer Flowee::parseAddress(const Napi::String &input, bool *isHash)
{
    // this can be either a hex string, or an address. Either way, utf8 should suffice.
    std::string str = input.ToString().Utf8Value();
    str.erase(remove_if(str.begin(), str.end(), isspace), str.end()); // trim

    auto rc = hexStringToBuffer(str);
    if (!rc.isEmpty()) {
        if (isHash)
            *isHash = true;
        return rc;
    }

    CashAddress::Content c = CashAddress::decodeCashAddrContent(str, "bitcoincash");
    bool ok = !c.hash.empty();
    if (!ok) { // try to fall back to legacy address encoding (btc compatible)
        CBase58Data old;
        if (old.SetString(str)) {
            c.hash = old.data();
            ok = true;
            if (old.isMainnetPkh())
                c.type = CashAddress::PUBKEY_TYPE;
            else if (old.isMainnetSh())
                c.type = CashAddress::SCRIPT_TYPE;
            else
                ok = false;
        }
    }
    if (ok) {
        if (isHash)
            *isHash = false;
        return CashAddress::createHashedOutputScript(c);
    }
    return Streaming::ConstBuffer();
}



Napi::Object setupBindings(Napi::Env env, Napi::Object exports)
{
    ContextData *data = new ContextData(env);
    data->setupBindings(env, exports);

    /*
     // uncomment this to have full debug-level logging.
    auto *logger = Log::Manager::instance();
    logger->clearChannels();
    Log::Verbosity v = Log::WarningLevel;
    v = Log::DebugLevel;
    logger->clearLogLevels(v);
    logger->addConsoleChannel();
    */

    return exports;
}


NODE_API_MODULE(flowee, setupBindings)