//  SPDX-FileCopyrightText: 2023 Yury Gubich <blue@macaw.me>
//  SPDX-License-Identifier: GPL-3.0-or-later

#include "api.h"
#include <QDebug>
#include <QJsonDocument>
#include <QJsonObject>
#include <QUrlQuery>

#include "codes.h"
#include "finalaction.h"
#include "helpers.h"

constexpr const char* json = "application/json";
constexpr const char* urlEncoded = "application/x-www-form-urlencoded";

const std::map<QString, QMetaType::Type> testStructure({
    {"type", QMetaType::QString},
    {"version", QMetaType::QString},
});

const std::map<QString, QMetaType::Type> resultStructure({
    {"result", QMetaType::LongLong},
});

const std::map<QString, QMetaType::Type> tokensStructure({
    {"accessToken", QMetaType::QString},
    {"renewToken", QMetaType::QString}
});

struct NetworkReplyDeleter {
    void operator () (QNetworkReply* reply) {
        reply->deleteLater();
    }
};

API::API(const QUrl& address, QObject* parent):
    QObject(parent),
    address(address),
    network(),
    state(NoServer),
    accessToken(),
    renewToken(),
    firstPoll(),
    pollReply(),
    assets()
{
    firstPoll.setSingleShot(true);
    firstPoll.setInterval(2000);
    connect(&firstPoll, &QTimer::timeout, this, &API::onFirstPollSuccess);
    connect(&assets, &Models::Assets::requestAssets, this, &API::requestAssets);
}

QUrl API::getAddress() const {
    return address;
}

API::State API::getState() const {
    return state;
}

void API::setTokens(const QString access, const QString &renew) {
    accessToken = access;
    renewToken = renew;
    setState(Authenticating);
    startPolling();
}

void API::startPolling() {
    qDebug() << "Starting polling...";
    if (state != Authenticating)
        throw std::runtime_error("Can not start polling in this state: " + std::to_string(state));

    sendPoll();
    firstPoll.start();
}

void API::setAddress(const QUrl& path) {
    if (address == path)
        return;

    if (state == Authenticated) {
        //do something
    }

    address = path;
    emit addressChanged(address);
    setState(address.isEmpty() ? NoServer : NotAuthenticated);
}

std::optional<QVariantMap> API::readResult(QNetworkReply* reply) {
    QVariant contentType = reply->header(QNetworkRequest::ContentTypeHeader);
    if (!
        contentType.isValid() ||
        contentType.userType() != QMetaType::QString ||
        contentType.toString() != json
    )
        return std::nullopt;

    QByteArray data = reply->readAll();
    QJsonDocument document = QJsonDocument::fromJson(data);
    if (!document.isObject())
        return std::nullopt;

    QJsonObject object = document.object();
    return object.toVariantMap();
}

bool API::validateResponse(const std::optional<QVariantMap>& data, const std::map<QString, QMetaType::Type>& structure) {
    if (!data.has_value())
        return false;

    for (const std::pair<const QString, QMetaType::Type>& pair : structure) {
        QVariantMap::ConstIterator itr = data->find(pair.first);
        if (itr == data->end())
            return false;

        if (itr->userType() != pair.second)
            return false;
    }

    return true;
}

void API::setState(State newState) {
    if (newState == state)
        return;

    state = newState;
    emit stateChanged(state);
}

QUrl API::createUrl(const QString &path) const {
    QString startingPath = address.path();
    QUrl url = address;
    url.setPath(startingPath + path);
    return url;
}

void API::test(const QString& path, const QJSValue& finished) {
    qDebug() << "Testing" << path;
    if (state == Offline)
        return callCallback(finished, "Need to be online to test");

    QUrl address(path);
    QNetworkRequest request(path + "/info");
    request.setHeader(QNetworkRequest::ContentTypeHeader, json);

    QNetworkReply* reply = network.get(request);
    connect(reply, &QNetworkReply::finished,
        std::bind(&API::onTestFinished, this, reply, address, finished)
    );
}

void API::onTestFinished(QNetworkReply* reply, const QUrl& addr, const QJSValue& finished) {
    std::unique_ptr<QNetworkReply, NetworkReplyDeleter> rpl(reply);
    QNetworkReply::NetworkError error = reply->error();
    if (error != QNetworkReply::NoError)
        return callCallback(finished, reply->errorString());

    std::optional<QVariantMap> data = readResult(reply);
    if (!validateResponse(data, testStructure))
        return callCallback(finished, "Malformed response");

    QString type = data->value("type").toString();
    if (type != "pica")
        return callCallback(finished, "server of this type (" + type + ") is not supported");

    QString version = data->value("version").toString();
    if (version != "0.0.1")
        return callCallback(finished, "server of this version (" + version + ") is not supported");

    callCallback(finished, QString(), {QJSValue(true)});
    address = "";       //to provoke singal change even if it's the same server
    setAddress(addr);
}

void API::sendRegister(const QString& login, const QString& password, const QJSValue& finished) {
    qDebug() << "Registering...";
    if (state != NotAuthenticated)
        return callCallback(finished, "Can not register in current state");

    QUrlQuery params({
        {"login", login},
        {"password", password}
    });

    QNetworkRequest request(createUrl("/register"));
    request.setHeader(QNetworkRequest::ContentTypeHeader, urlEncoded);

    QNetworkReply* reply = network.post(request, params.toString(QUrl::FullyEncoded).toUtf8());
    connect(reply, &QNetworkReply::finished,
        std::bind(&API::onRegisterFinished, this, reply, finished)
    );
}

void API::onRegisterFinished(QNetworkReply* reply, const QJSValue& finished) const {
    std::unique_ptr<QNetworkReply, NetworkReplyDeleter> rpl(reply);
    QNetworkReply::NetworkError error = reply->error();
    std::optional<QVariantMap> data = readResult(reply);
    std::optional<Codes::Register> code;
    QString detail;
    bool success = false;
    if (validateResponse(data, resultStructure)) {
        code = Codes::convertRegister(data->value("result").toInt());
        success = code.value() == Codes::Register::success;
        if (!success)
            detail = Codes::description(code.value());
    }

    if (error != QNetworkReply::NoError)
        return callCallback(finished, reply->errorString() + (success ? "" : ": " + detail));

    if (!code)
        return callCallback(finished, "Malformed result");

    callCallback(finished, detail, {QJSValue(success)});
}

void API::sendLogin(const QString& login, const QString& password, const QJSValue& finished) {
    qDebug() << "Logging in...";
    if (state != NotAuthenticated)
        return callCallback(finished, "Can not register in current state");

    QUrlQuery params({
        {"login", login},
        {"password", password}
    });

    QNetworkRequest request(createUrl("/login"));
    request.setHeader(QNetworkRequest::ContentTypeHeader, urlEncoded);
    setState(Authenticating);
    QNetworkReply* reply = network.post(request, params.toString(QUrl::FullyEncoded).toUtf8());
    connect(reply, &QNetworkReply::finished,
            std::bind(&API::onLoginFinished, this, reply, finished)
            );
}

void API::onLoginFinished(QNetworkReply* reply, const QJSValue& finished) {
    State state = NotAuthenticated;
    FinalAction action([this, &state]() {       //this should be executed on leaving the function in any way
        setState(state);                        //setting the state as a result of this object destruction
    });                                         //this way any error will result in NotAuthenticated, and on success it should be Authenticated

    std::unique_ptr<QNetworkReply, NetworkReplyDeleter> rpl(reply);
    QNetworkReply::NetworkError error = reply->error();
    std::optional<QVariantMap> data = readResult(reply);
    std::optional<Codes::Login> code;
    QString detail;
    bool success = false;
    if (validateResponse(data, resultStructure)) {
        code = Codes::convertLogin(data->value("result").toInt());
        success = code.value() == Codes::Login::success;
        if (!success)
            detail = Codes::description(code.value());
    }

    if (error != QNetworkReply::NoError)
        return callCallback(finished, reply->errorString() + (success ? "" : ": " + detail));

    if (!code)
        return callCallback(finished, "Malformed result");

    if (!validateResponse(data, tokensStructure))
        return callCallback(finished, "Malformed result: missing tokens");


    callCallback(finished, detail, {QJSValue(success)});

    state = Authenticating;
    accessToken = data->value("accessToken").toString();
    renewToken = data->value("renewToken").toString();
    emit storeTokens(accessToken, renewToken);
    startPolling();
}

void API::addAsset(const QString& title, const QString& icon, const QJSValue &finished) {
    qDebug() << "Adding asset...";
    if (state != Authenticated)
        return callCallback(finished, "Can not add assets in current state");

    QUrlQuery params({
        {"title", title},
        {"icon", icon},
        {"currency", "1"}
    });

    QNetworkRequest request(createUrl("/addAsset"));
    request.setHeader(QNetworkRequest::ContentTypeHeader, urlEncoded);
    request.setRawHeader("Authorization", "Bearer " + accessToken.toUtf8());
    QNetworkReply* reply = network.post(request, params.toString(QUrl::FullyEncoded).toUtf8());
    connect(reply, &QNetworkReply::finished,
        std::bind(&API::onAssetAdded, this, reply, finished)
    );
}

void API::onAssetAdded(QNetworkReply *reply, const QJSValue &finished) {
    std::unique_ptr<QNetworkReply, NetworkReplyDeleter> rpl(reply);
    QNetworkReply::NetworkError error = reply->error();

    qDebug() << error;
    if (error != QNetworkReply::NoError)
        return callCallback(finished, reply->errorString());

    callCallback(finished, QString(), {QJSValue(true)});
}

void API::sendPoll(bool clear) {
    if (accessToken.isEmpty())
        throw std::runtime_error("Can not start polling: access token is empty");

    QUrl url = createUrl("/poll");
    if (clear)
        url.setQuery(QUrlQuery({{"clearCache", "all"}}));

    QByteArray authorizationHeader = "Bearer " + accessToken.toUtf8();
    QNetworkRequest request(url);
    request.setHeader(QNetworkRequest::ContentTypeHeader, json);
    request.setRawHeader("Authorization", authorizationHeader);
    request.setTransferTimeout(30000);

    pollReply = std::unique_ptr<QNetworkReply>(network.get(request));
    connect(
        pollReply.get(), &QNetworkReply::finished,
        this, &API::onPollFinished,
        Qt::QueuedConnection
        );
}

void API::onPollFinished() {
    firstPoll.stop();
    QNetworkReply::NetworkError error = pollReply->error();
    std::optional<QVariantMap> data = readResult(pollReply.get());
    Codes::Poll code = Codes::Poll::unknownError;
    if (validateResponse(data, resultStructure))
        code = Codes::convertPoll(data->value("result").toInt());
    else
        qDebug() << "";

    QString detail = Codes::description(code);

    if (error != QNetworkReply::NoError)
        qDebug() << pollReply->errorString() + ": " + detail;
    else
        qDebug() << "Poll finished: " + detail;

    bool clear = false;
    switch (code) {
        case Codes::Poll::success: {
            QVariantMap::ConstIterator itr = data->constFind("data");
            if (itr == data->constEnd())
                qDebug("received a poll that claimed to have some updates, but the \"data\" field is abscent");

            const QVariant& vdata = itr.value();
            if (vdata.canConvert<QVariantMap>())
                clear = handleChanges(qast<QVariantMap>(itr.value()));
            else
                qDebug("received a poll that claimed to have some updates, but the \"data\" field is not an object");
        }
            //todo handle the result
        case Codes::Poll::timeout:
            setState(Authenticated);
            return sendPoll(clear);
        case Codes::Poll::tokenProblem:
        case Codes::Poll::replace:
        case Codes::Poll::unknownError: //todo this one doesn't actually mean that we can't work for now, the network may be temporarily down or something
            pollReply.reset();
            return setState(NotAuthenticated);
    }
}

bool API::handleChanges(const QVariantMap& changes) {
    QVariantMap::ConstIterator itr = changes.constFind("system");
    if (itr != changes.constEnd()) {
        const QVariant& vsys = itr.value();
        if (vsys.canConvert<QVariantMap>()) {
            const QVariantMap& sys = qast<QVariantMap>(vsys);
            QVariantMap::ConstIterator invItr = sys.constFind("invalidate");
            if (invItr != sys.constEnd()) {
                const QVariant& vinv = invItr.value();
                if (vinv.canConvert<bool>() && vinv.toBool())
                    resetAllModels();
            }
        }
    }

    itr = changes.constFind("assets");
    if (itr != changes.constEnd()) {
        const QVariant& vassets = itr.value();
        if (vassets.canConvert<QVariantMap>()) {
            const QVariantMap& assets = qast<QVariantMap>(vassets);
            QVariantMap::ConstIterator aItr = assets.constFind("invalidate");
            if (aItr != assets.constEnd()) {
                const QVariant& vinv = aItr.value();
                if (vinv.canConvert<bool>() && vinv.toBool())
                    API::assets.clear();
            }

            aItr = assets.constFind("added");
            if (aItr != assets.constEnd()) {
                const QVariant& vadd = aItr.value();
                std::deque<Models::Asset> added;
                if (!Models::Assets::deserialize(qast<QVariantList>(itr.value()), added))
                    qDebug() << "Error deserializng added assets";
                else
                    API::assets.addAssets(added);
            }
        }
    }

    return true;
}

void API::resetAllModels() {
    assets.clear();
}

void API::onFirstPollSuccess() {
    setState(Authenticated);
}

void API::requestAssets() {
    if (state != Authenticated) {
        qDebug() << "An attempt to request assets on unauthenticated state";
        assets.receivedAssets({});
        return;
    }
    qDebug() << "Requesting assets...";

    QUrl url = createUrl("/listAssets");
    QByteArray authorizationHeader = "Bearer " + accessToken.toUtf8();
    QNetworkRequest request(url);
    request.setHeader(QNetworkRequest::ContentTypeHeader, json);
    request.setRawHeader("Authorization", authorizationHeader);

    QNetworkReply* reply = network.get(request);
    connect(
        pollReply.get(), &QNetworkReply::finished,
        this, std::bind(&API::responseAssets, this, reply)
    );
}

void API::responseAssets(QNetworkReply *reply) {
    std::deque<Models::Asset> result;
    FinalAction action([this, &result]() {
        assets.receivedAssets(result);
    });

    std::unique_ptr<QNetworkReply, NetworkReplyDeleter> rpl(reply);
    QNetworkReply::NetworkError error = reply->error();

    if (error != QNetworkReply::NoError) {
        qDebug() << "Error receiving assets:" << reply->errorString();
        return;
    }

    std::optional<QVariantMap> data = readResult(reply);
    if (!data) {
        qDebug() << "Error receiving assets: bad data";
        return;
    }

    QVariantMap::ConstIterator itr = data->find("assets");
    if (itr == data->constEnd() || !itr->canConvert<QVariantList>()) {
        qDebug() << "Error receiving assets: assets are missing or not in an array";
        return;
    }

    if (!Models::Assets::deserialize(qast<QVariantList>(itr.value()), result)) {
        qDebug() << "Error deserializng assets";
        result.clear();
    }

    qDebug() << "Assets successfully received";
    //final action goes automatically
}

void API::callCallback(const QJSValue& callback, const QString& error, const QJSValueList& arguments) const {
    if (callback.isCallable()) {
        if (error.isEmpty())
            callback.call(QJSValueList({QJSValue(QJSValue::NullValue)}) + arguments);
        else
            callback.call({QJSValue(error)});
    }
}