#include "downloader.h"

#include <QCoreApplication>
#include <QDateTime>
#include <QFileInfo>
#include <QRegularExpression>

namespace
{
/**
 * @brief 从 Content-Disposition 响应头中提取服务器建议文件名。
 * @param headerValue 响应头原始值，可能包含百分号编码和 filename 字段。
 * @return 安全的纯文件名；解析失败返回空字符串。
 *
 * 设计意图：只接收文件名部分，丢弃目录，避免服务器返回带路径的名称覆盖应用目录外文件。
 * 边界条件：响应头为空、格式不匹配、文件名为空时交给调用方继续使用本地预设文件名。
 */
QString fileNameFromContentDisposition(const QVariant &headerValue)
{
    if(!headerValue.isValid())
    {
        return QString();
    }

    const QString contentDisposition =
        QString::fromUtf8(QByteArray::fromPercentEncoding(headerValue.toByteArray()));
    const QRegularExpression regExp(R"(filename\*?=(?:UTF-8''|")?([^";]+))",
                                    QRegularExpression::CaseInsensitiveOption);
    const QRegularExpressionMatch match = regExp.match(contentDisposition);
    if(!match.hasMatch())
    {
        return QString();
    }

    return QFileInfo(match.captured(1).trimmed()).fileName();
}
}

Downloader::Downloader(QObject *parent)
    : QObject{parent}
{
    m_pNetWorkAccessManager = new QNetworkAccessManager(this);
    dir.setPath(QCoreApplication::applicationDirPath());
}

void Downloader::setUrl(const QString &_url)
{
    m_pUrl = QUrl(_url);
}

void Downloader::startDownload(const QString &_url)
{
    if(m_bIsDownloading)
    {
        emit doShowInfo(tr("download task is already running"));
        return;
    }

    if(!_url.isEmpty())
    {
        m_pUrl = QUrl(_url);
    }

    if(!m_pUrl.isValid() || m_pUrl.isEmpty())
    {
        emit doShowInfo(tr("download url is invalid"));
        return;
    }

    if(m_fileName.trimmed().isEmpty())
    {
        const QString urlFileName = QFileInfo(m_pUrl.path()).fileName();
        if(urlFileName.isEmpty())
        {
            emit doShowInfo(tr("download file name is empty"));
            return;
        }
        m_fileName = urlFileName;
    }

    m_bIsDownloading = true;

    if(!dir.exists() && !dir.mkpath("."))
    {
        m_bIsDownloading = false;
        emit doShowInfo(tr("create download directory failed"));
        return;
    }

    const QString targetPath = targetFilePath();
    const QString partPath = partialFilePath();

    // 保留旧版本文件，便于更新失败时人工回滚；同一天多次下载时追加时间避免重名。
    if(QFile::exists(targetPath))
    {
        QFile oldFile(targetPath);
        const QString backupPath = targetPath + "_" + QDateTime::currentDateTime().toString("yyyy-MM-dd_hhmmss");
        if(!oldFile.rename(backupPath))
        {
            emit doShowInfo(tr("backup old file failed: %1").arg(oldFile.errorString()));
        }
    }

    QFile::remove(partPath);
    file.setFileName(partPath);
    if(!file.open(QIODevice::WriteOnly | QIODevice::Truncate))
    {
        m_bIsDownloading = false;
        emit doShowInfo(tr("open download file failed: %1").arg(file.errorString()));
        return;
    }

    QNetworkRequest request;
    request.setUrl(m_pUrl);
    m_pReply = m_pNetWorkAccessManager->get(request);

    connect(m_pReply, &QNetworkReply::readyRead, this, [this]()
    {
        if(!file.isOpen() || !m_pReply)
        {
            return;
        }

        const QByteArray chunk = m_pReply->readAll();
        if(file.write(chunk) != chunk.size())
        {
            emit doShowInfo(tr("write download file failed: %1").arg(file.errorString()));
            m_pReply->abort();
        }
    });

    connect(m_pReply, &QNetworkReply::downloadProgress, this, [this](qint64 received, qint64 total)
    {
        emit doProgress(received, total);
    });

    connect(m_pReply, &QNetworkReply::metaDataChanged, this, [this]()
    {
        const QString responseFileName =
            fileNameFromContentDisposition(m_pReply->header(QNetworkRequest::ContentDispositionHeader));
        if(!responseFileName.isEmpty() && m_fileName.isEmpty())
        {
            m_fileName = responseFileName;
        }
    });

    connect(m_pReply, &QNetworkReply::finished, this, [this]()
    {
        QNetworkReply *finishedReply = m_pReply;
        const QNetworkReply::NetworkError errorCode = finishedReply->error();
        // HTTP 状态码用于拦截 404/500 等服务器错误，避免把错误页面当作升级包落盘。
        const int httpStatusCode =
            finishedReply->attribute(QNetworkRequest::HttpStatusCodeAttribute).toInt();
        if(errorCode != QNetworkReply::NoError)
        {
            emit onError(errorCode);
            emit doShowInfo(finishedReply->errorString());
            cleanupCurrentReply(true);
            return;
        }
        if(httpStatusCode >= 400)
        {
            emit doShowInfo(tr("http download failed, status code: %1").arg(httpStatusCode));
            cleanupCurrentReply(true);
            return;
        }

        if(file.isOpen())
        {
            file.close();
        }

        const QString partPath = partialFilePath();
        const QString targetPath = targetFilePath();
        if(!QFile::exists(partPath))
        {
            emit doShowInfo(tr("download temporary file not exists"));
            cleanupCurrentReply(true);
            return;
        }

        QFile::remove(targetPath);
        if(!QFile::rename(partPath, targetPath))
        {
            emit doShowInfo(tr("rename file failed"));
            cleanupCurrentReply(true);
            return;
        }

        file.setFileName(targetPath);
        m_bIsDownloading = false;
        finishedReply->deleteLater();
        m_pReply = nullptr;
        emit doFinished();
    });
}

void Downloader::checkVersion()
{
    QNetworkRequest request{QUrl(CHECK_URL)};
    m_pNetWorkAccessManager->get(request);
}

const QFile &Downloader::getFile() const
{
    return file;
}

const QDir &Downloader::getDir() const
{
    return dir;
}

const QString &Downloader::fileName() const
{
    return m_fileName;
}

void Downloader::setFileName(const QString &newFileName)
{
    m_fileName = QFileInfo(newFileName).fileName();
}

void Downloader::cleanupCurrentReply(bool removePartial)
{
    if(file.isOpen())
    {
        file.close();
    }

    if(removePartial)
    {
        QFile::remove(partialFilePath());
    }

    if(m_pReply)
    {
        m_pReply->deleteLater();
        m_pReply = nullptr;
    }

    m_bIsDownloading = false;
}

QString Downloader::partialFilePath() const
{
    if(m_fileName.isEmpty())
    {
        return QString();
    }

    return dir.filePath(m_fileName + ".part");
}

QString Downloader::targetFilePath() const
{
    if(m_fileName.isEmpty())
    {
        return QString();
    }

    return dir.filePath(m_fileName);
}