#include "downloadworker.h"
#include <QIODevice>
#include <QEventLoop>
#include <QNetworkAccessManager>
#include <QNetworkRequest>
#include <QNetworkReply>
#include <QDebug>
#include <QThread>

DownloadWorker::DownloadWorker(QObject *parent)
{

}

void DownloadWorker::setIdentifier(int identifier)
{
    this->identifier = identifier;
}

void DownloadWorker::setParamter(const QString &url, QPair<qint64, qint64> range, QFile *file)
{
    this->url = url;
    this->startPos = range.first;
    this->endPos = range.second;
    this->file = file;
}

qint64 DownloadWorker::getReceivedPos()
{
    return receivedPos;
}

void DownloadWorker::doWork()
{
        mgr = new QNetworkAccessManager(this);
        QNetworkRequest request;
        request.setUrl(url);
        request.setAttribute(QNetworkRequest::FollowRedirectsAttribute, true);
        request.setRawHeader("Range", QString("bytes=%1-%2").arg(startPos)
                    .arg(endPos).toLocal8Bit());
        reply = mgr->get(request);
        qDebug() << "开始下载数据：" << QString(" %1~%2 -> writePos Start %3")
            .arg(startPos).arg(endPos).arg(receivedPos);
        connect(reply, &QNetworkReply::errorOccurred, [this](QNetworkReply::NetworkError error){
            if (error != QNetworkReply::NoError) {
                qDebug() << "出错了：" << reply->errorString();
            }
        });
        connect(reply, &QNetworkReply::finished, mgr, &QNetworkAccessManager::deleteLater);
        connect(reply, &QNetworkReply::finished, reply, &QNetworkReply::deleteLater);
        connect(reply, &QNetworkReply::readyRead, this, &DownloadWorker::dataReady);
        connect(reply, &QNetworkReply::finished, this, &DownloadWorker::slotFinish);
        connect(reply, &QNetworkReply::downloadProgress, this, &DownloadWorker::handleProcess);

}

void DownloadWorker::doStop()
{
    reply->deleteLater();
    reply = nullptr;
    mgr->deleteLater();
    mgr = nullptr;
}

void DownloadWorker::dataReady()
{
    qDebug() << QString("测试是否执行: %1 %2").arg(startPos).arg(receivedPos);
    QByteArray data = reply->readAll();
    file->seek(startPos + receivedPos);
    file->write(data);
    receivedPos += data.size();
}

void DownloadWorker::slotFinish()
{
    file->flush();
    qDebug() << "数据块下载完毕：" << QString(" %1~%2 -> writePos Start %3")
        .arg(startPos).arg(endPos).arg(receivedPos);
    emit workFinished();
}

void DownloadWorker::handleProcess(qint64, qint64)
{
    emit this->downloadProcess();
}


DownloadController::DownloadController(QObject *parent)
{
    this->threadNum = 4;
}

void DownloadController::setFilename(QString filename)
{
    this->filename = filename;
}

void DownloadController::setThreadNum(int threadNum)
{
    this->threadNum = threadNum;
}

/**
 * @brief 开始下载
 */
void DownloadController::startDownload(const QString &url, qint64 fileSize)
{
    finish = 0;

    // 下载任务等分，计算每个线程的下载数据
    this->fileSize = fileSize;
    qint64 segmentSize = fileSize / threadNum;
    ranges.resize(threadNum);
    QVector<qint64> receivedBytes;
    receivedBytes.resize(threadNum);
    for (int i = 0; i < threadNum; i++) {
        ranges[i].first = i * segmentSize;
        ranges[i].second = i * segmentSize + segmentSize - 1;
        receivedBytes[i] = 0;
    }
    ranges[threadNum-1].second = fileSize; // 余数部分加入最后一个

    // 打开文件
    file = new QFile;
    file->setFileName(filename);
    if (file->exists())
        file->remove();
    if (!file->open(QIODevice::WriteOnly)) {
        delete file;
        file = nullptr;
        emit errorOccur(file->errorString());
        return;
    }
    file->resize(fileSize);

    // 创建下载线程
    for(int i = 0; i < ranges.size(); i++) {
        qDebug() << QString("第%1个下载请求：%2-%3").arg(i).arg(ranges.at(i).first).arg(ranges.at(i).second);
        auto worker = new DownloadWorker(this);
        auto range = ranges.at(i);
        worker->setIdentifier(i);
        worker->setParamter(url, range, file);
        workers.append(worker);
        connect(worker, &DownloadWorker::downloadProcess, this, &DownloadController::handleProcess);
        connect(worker, &DownloadWorker::workFinished, this, &DownloadController::chunkDownloadFinish);
        worker->doWork();
    }
}

/**
 * @brief 停止下载
 */
void DownloadController::stopDownload()
{
    for(int i = 0; i < workers.size(); i++) {
        workers.at(i)->doStop();
    }
    file->flush();
    file->close();
    delete file;
    file = nullptr;
}


void DownloadController::handleProcess()
{
    qint64 bytesReceived = 0;
    for(int i = 0; i < workers.size(); i++) {
        bytesReceived += workers.at(i)->getReceivedPos();
    }
    qDebug() << QString("下载进度 %1-%2").arg(bytesReceived).arg(fileSize);
    emit downloadProcess(bytesReceived, fileSize);
}

void DownloadController::chunkDownloadFinish()
{
    finish++;
    if (finish == threadNum) {
        emit downloadFinished();
    }
}