#include "dialogs/ImageCropDialog.h"

#include <QBoxLayout>
#include <QDialogButtonBox>
#include <QLabel>
#include <QMouseEvent>
#include <QPainter>
#include <QPushButton>
#include <QImageReader>
#include <QtMath>

class ImageCropDialog::CropView final : public QWidget {
public:
    explicit CropView(QWidget* parent = nullptr)
        : QWidget(parent) {
        setMouseTracking(true);
        setMinimumSize(480, 320);
    }

    void setImage(const QImage& img) {
        m_image = img;
        m_selection = {};
        updateGeometry();
        update();
    }

    bool hasSelection() const { return !m_selection.isNull() && m_selection.width() > 0 && m_selection.height() > 0; }

    QRect selectionInImagePixels() const {
        if (m_image.isNull() || !hasSelection()) {
            return {};
        }
        const auto map = viewToImageTransform();
        // selection 是 view 坐标；映射到 image 像素坐标
        const QRectF selF = QRectF(m_selection).normalized();
        bool invertible = false;
        const QTransform inv = map.inverted(&invertible);
        if (!invertible) {
            return {};
        }

        const QPointF topLeftImg = inv.map(selF.topLeft());
        const QPointF bottomRightImg = inv.map(selF.bottomRight());

        // 使用 floor/ceil，避免因为取整导致宽高变 0
        const int left = qFloor(std::min(topLeftImg.x(), bottomRightImg.x()));
        const int top = qFloor(std::min(topLeftImg.y(), bottomRightImg.y()));
        const int right = qCeil(std::max(topLeftImg.x(), bottomRightImg.x()));
        const int bottom = qCeil(std::max(topLeftImg.y(), bottomRightImg.y()));

        QRect r(QPoint(left, top), QPoint(right, bottom));
        r = r.normalized().intersected(QRect(0, 0, m_image.width(), m_image.height()));
        return r;
    }

    void resetSelection() {
        m_selection = {};
        update();
    }

protected:
    void paintEvent(QPaintEvent*) override {
        QPainter p(this);
        p.fillRect(rect(), palette().window());

        if (m_image.isNull()) {
            p.setPen(palette().text().color());
            p.drawText(rect(), Qt::AlignCenter, QStringLiteral("无法加载图片"));
            return;
        }

        const auto map = viewToImageTransform();
        p.setRenderHint(QPainter::SmoothPixmapTransform, true);
        p.setTransform(map);
        p.drawImage(QPoint(0, 0), m_image);
        p.resetTransform();

        if (hasSelection()) {
            // 避免 CompositionMode_Clear 在某些平台/样式下表现异常：
            // 用“围绕选区画四块遮罩”的方式实现高亮裁剪区域。
            const QRect sel = m_selection.normalized().intersected(rect());
            const QColor shade(0, 0, 0, 120);

            // 上
            p.fillRect(QRect(0, 0, width(), sel.top()), shade);
            // 下
            p.fillRect(QRect(0, sel.bottom(), width(), height() - sel.bottom()), shade);
            // 左
            p.fillRect(QRect(0, sel.top(), sel.left(), sel.height()), shade);
            // 右
            p.fillRect(QRect(sel.right(), sel.top(), width() - sel.right(), sel.height()), shade);

            p.setPen(QPen(QColor(255, 255, 255, 220), 2));
            p.drawRect(sel);
        }
    }

    void mousePressEvent(QMouseEvent* e) override {
        if (m_image.isNull() || e->button() != Qt::LeftButton) {
            return;
        }
        m_dragging = true;
        m_anchor = e->position().toPoint();
        m_selection = QRect(m_anchor, m_anchor);
        update();
    }

    void mouseMoveEvent(QMouseEvent* e) override {
        if (!m_dragging) {
            return;
        }
        const QPoint cur = e->position().toPoint();
        m_selection = QRect(m_anchor, cur).normalized();
        update();
    }

    void mouseReleaseEvent(QMouseEvent* e) override {
        if (e->button() != Qt::LeftButton) {
            return;
        }
        m_dragging = false;
        update();
    }

private:
    QTransform viewToImageTransform() const {
        // 让图片按比例 fit 到 view 中居中显示
        const QSizeF viewSize = size();
        const QSizeF imgSize = m_image.size();
        const qreal sx = viewSize.width() / imgSize.width();
        const qreal sy = viewSize.height() / imgSize.height();
        const qreal s = std::min(sx, sy);

        const qreal drawW = imgSize.width() * s;
        const qreal drawH = imgSize.height() * s;
        const qreal offsetX = (viewSize.width() - drawW) / 2.0;
        const qreal offsetY = (viewSize.height() - drawH) / 2.0;

        QTransform t;
        t.translate(offsetX, offsetY);
        t.scale(s, s);
        return t;
    }

private:
    QImage m_image;
    bool m_dragging = false;
    QPoint m_anchor;
    QRect m_selection;
};

ImageCropDialog::ImageCropDialog(const QString& imagePath, QWidget* parent)
    : QDialog(parent),
      m_imagePath(imagePath) {
    setWindowTitle(QStringLiteral("裁剪图片"));
    setModal(true);
    resize(900, 600);
    loadImageOrClose();
    rebuildUi();
}

void ImageCropDialog::loadImageOrClose() {
    // Qt 默认的 image allocation limit 较小（常见为 256MB），超大分辨率图会被拒绝。
    // 这里用 QImageReader 并提高 limit；同时对极端大图按像素数上限自动缩放，避免 OOM。
#if QT_VERSION >= QT_VERSION_CHECK(6, 0, 0)
    QImageReader::setAllocationLimit(1024); // MB
#endif
    QImageReader reader(m_imagePath);
    reader.setAutoTransform(true);
    const QSize sz = reader.size();
    if (sz.isValid()) {
        constexpr qint64 kMaxPixels = 120LL * 1000LL * 1000LL; // 120MP
        const qint64 pixels = qint64(sz.width()) * qint64(sz.height());
        if (pixels > kMaxPixels) {
            const double s = std::sqrt(double(kMaxPixels) / std::max<double>(1.0, double(pixels)));
            const int nw = std::max(1, int(std::lround(sz.width() * s)));
            const int nh = std::max(1, int(std::lround(sz.height() * s)));
            reader.setScaledSize(QSize(nw, nh));
        }
    }
    m_image = reader.read();
    if (m_image.isNull()) {
        reject();
    }
}

void ImageCropDialog::rebuildUi() {
    auto* root = new QVBoxLayout(this);

    auto* hint = new QLabel(QStringLiteral("拖拽选择裁剪区域（不选则使用整张图）。"), this);
    root->addWidget(hint);

    m_view = new CropView(this);
    m_view->setImage(m_image);
    root->addWidget(m_view, 1);

    auto* buttons = new QDialogButtonBox(QDialogButtonBox::Ok | QDialogButtonBox::Cancel, this);
    m_okButton = buttons->button(QDialogButtonBox::Ok);
    auto* resetBtn = new QPushButton(QStringLiteral("重置选择"), this);
    buttons->addButton(resetBtn, QDialogButtonBox::ActionRole);

    connect(resetBtn, &QPushButton::clicked, this, &ImageCropDialog::onReset);
    connect(buttons, &QDialogButtonBox::accepted, this, &ImageCropDialog::onOk);
    connect(buttons, &QDialogButtonBox::rejected, this, &ImageCropDialog::reject);
    root->addWidget(buttons);
}

bool ImageCropDialog::hasValidSelection() const {
    return m_view && m_view->hasSelection();
}

QRect ImageCropDialog::selectedRectInImagePixels() const {
    if (!m_view) {
        return {};
    }
    return m_view->selectionInImagePixels();
}

void ImageCropDialog::onReset() {
    if (m_view) {
        m_view->resetSelection();
    }
}

void ImageCropDialog::onOk() {
    accept();
}