// SPDX-FileCopyrightText: 2026 Filip Leonarski, Paul Scherrer Institute <filip.leonarski@psi.ch>
// SPDX-License-Identifier: GPL-3.0-only

#include "JFJochViewerFileBrowser.h"

#include <QVBoxLayout>
#include <QHBoxLayout>
#include <QLineEdit>
#include <QToolButton>
#include <QTreeView>
#include <QHeaderView>
#include <QScrollBar>
#include <QFileDialog>
#include <QSettings>
#include <QDir>
#include <QFileInfo>
#include <QRegularExpression>
#include <QShortcut>
#include <QStyle>
#include <QTimer>
#include <QApplication>
#include <QSet>

namespace {
    constexpr auto kDataRootEnvVar = "JUNGFRAUJOCH_DATA_ROOT";
    constexpr auto kSettingsKey = "fileBrowserRoot";
    constexpr int kRefreshIntervalMs = 3000;

    // The filter box narrows files only; a directory always passes. Filtering directories too would
    // hide everything below one whose own name does not match - including the files that do match -
    // and would hide the root's ancestors, which leaves the tree with no valid root index at all.
    class FileOnlyFilterProxy : public QSortFilterProxyModel {
    public:
        using QSortFilterProxyModel::QSortFilterProxyModel;

    protected:
        bool filterAcceptsRow(int row, const QModelIndex &parent) const override {
            const auto *fs = qobject_cast<const QFileSystemModel *>(sourceModel());
            if (fs && fs->isDir(fs->index(row, 0, parent)))
                return true;
            return QSortFilterProxyModel::filterAcceptsRow(row, parent);
        }
    };
}

QString JFJochViewerFileBrowser::SlsDataRoot(const QString &user) {
    const auto match = QRegularExpression("\\Ae(\\d{5})\\z").match(user);
    if (!match.hasMatch())
        return {};
    return "/sls/mx/data/p" + match.captured(1) + "/raw";
}

QString JFJochViewerFileBrowser::DefaultRoot() {
    // Site default (e.g. a beamline launcher setting it to /sls/mx/data/p<group>), then whatever
    // root was last browsed to (so re-launching without the variable set doesn't start over from
    // scratch), then - for an SLS beamline account - that proposal's raw data, then the user's home
    // - never the current directory, which for an installed binary is typically the install
    // location rather than anywhere the user would keep data.
    const QString env_root = qEnvironmentVariable(kDataRootEnvVar);
    if (!env_root.isEmpty() && QDir(env_root).exists())
        return env_root;

    const QString last_root = QSettings("PSI", "jfjoch_viewer").value(kSettingsKey).toString();
    if (!last_root.isEmpty() && QDir(last_root).exists())
        return last_root;

    // USER is the portable spelling Qt exposes; it is simply empty where the beamline directory
    // could not exist anyway, so everyone else silently gets home, as before.
    const QString sls_root = SlsDataRoot(qEnvironmentVariable("USER"));
    if (!sls_root.isEmpty() && QDir(sls_root).exists())
        return sls_root;

    return QDir::homePath();
}

JFJochViewerFileBrowser::JFJochViewerFileBrowser(QWidget *parent) : QWidget(parent) {
    auto *layout = new QVBoxLayout(this);
    // No inset: every other dock panel sits flush against its edges, and 4 px here put the panel's
    // content 4 px away from the resize handle it shares with the image, which reads as a handle
    // that is off-centre.
    layout->setContentsMargins(0, 0, 0, 0);

    auto *root_row = new QHBoxLayout();
    root_edit_ = new QLineEdit(this);
    root_edit_->setToolTip("Data root - type a path or use Browse…");
    auto *browse_button = new QToolButton(this);
    browse_button->setText("…");
    browse_button->setToolTip("Browse for a data root…");
    auto *refresh_button = new QToolButton(this);
    refresh_button->setIcon(style()->standardIcon(QStyle::SP_BrowserReload));
    refresh_button->setToolTip("Refresh the file list (F5)");
    root_row->addWidget(root_edit_);
    root_row->addWidget(browse_button);
    root_row->addWidget(refresh_button);
    layout->addLayout(root_row);

    filter_edit_ = new QLineEdit(this);
    filter_edit_->setPlaceholderText("Filter…");
    filter_edit_->setClearButtonEnabled(true);
    layout->addWidget(filter_edit_);

    model_ = new QFileSystemModel(this);
    model_->setFilter(QDir::AllDirs | QDir::Files | QDir::NoDotAndDotDot);
    // Directories are always listed regardless of these; only *_master.h5 / *_process.h5 and
    // miniCBF frames among files. The many _data_NNNNNN.h5 shards of a dataset are not meant to be
    // opened directly; a .cbf is one frame per file, and opening any of them opens its whole sweep.
    model_->setNameFilters({"*_master.h5", "*_process.h5", "*.cbf"});
    model_->setNameFilterDisables(false);   // hide non-matching files rather than just greying them out

    proxy_ = new FileOnlyFilterProxy(this);
    proxy_->setSourceModel(model_);
    proxy_->setFilterKeyColumn(0);
    proxy_->setFilterCaseSensitivity(Qt::CaseInsensitive);
    // Deliberately not recursive: it only ever narrows names already listed at an expanded level,
    // never forces fetching a collapsed subtree just to search inside it.

    tree_ = new QTreeView(this);
    tree_->setModel(proxy_);
    tree_->setHeaderHidden(true);
    for (int col = 1; col < model_->columnCount(); ++col)
        tree_->hideColumn(col);
    tree_->setSortingEnabled(false);
    layout->addWidget(tree_);

    connect(browse_button, &QToolButton::clicked, this, &JFJochViewerFileBrowser::onBrowseClicked);
    connect(root_edit_, &QLineEdit::editingFinished, this, &JFJochViewerFileBrowser::onRootEditingFinished);
    connect(filter_edit_, &QLineEdit::textChanged, proxy_, &QSortFilterProxyModel::setFilterFixedString);
    connect(tree_, &QTreeView::doubleClicked, this, &JFJochViewerFileBrowser::onDoubleClicked);
    connect(refresh_button, &QToolButton::clicked, this, [this] { Refresh(); });
    // Window-wide, but a shortcut on a hidden widget never fires, so F5 does nothing while the panel is
    // tabbed behind the Processing one.
    connect(new QShortcut(QKeySequence(Qt::Key_F5), this), &QShortcut::activated, this, [this] { Refresh(); });

    auto *refresh_timer = new QTimer(this);
    connect(refresh_timer, &QTimer::timeout, this, [this] {
        // Not while hidden, and not in the middle of a click or a scroll-bar drag.
        if (isVisible() && QApplication::mouseButtons() == Qt::NoButton)
            Refresh(false);
    });
    refresh_timer->start(kRefreshIntervalMs);

    SetRoot(DefaultRoot());
}

void JFJochViewerFileBrowser::SetRoot(const QString &path) {
    QDir dir(path);
    if (!dir.exists())
        return;

    const QString canonical = QDir::toNativeSeparators(dir.absolutePath());
    root_edit_->setText(canonical);
    model_->setRootPath(canonical);
    tree_->setRootIndex(proxy_->mapFromSource(model_->index(canonical)));

    QSettings("PSI", "jfjoch_viewer").setValue(kSettingsKey, canonical);
}

void JFJochViewerFileBrowser::ResetToDefaultRoot() {
    SetRoot(DefaultRoot());
}

void JFJochViewerFileBrowser::CollectExpanded(const QModelIndex &parent, QStringList &dirs) const {
    for (int row = 0; row < proxy_->rowCount(parent); ++row) {
        const QModelIndex child = proxy_->index(row, 0, parent);
        if (tree_->isExpanded(child)) {
            dirs.append(model_->filePath(proxy_->mapToSource(child)));
            CollectExpanded(child, dirs);
        }
    }
}

void JFJochViewerFileBrowser::Refresh(bool force) {
    QStringList dirs{model_->rootPath()};
    CollectExpanded(tree_->rootIndex(), dirs);
    const QPersistentModelIndex top = tree_->indexAt(QPoint(0, 0));

    bool added = false;
    for (const QString &path : dirs) {
        // One stat per directory: a directory's mtime moves whenever an entry is added or removed, so an
        // unchanged one - typically all but the one being written to - is not read at all.
        const QDateTime mtime = QFileInfo(path).lastModified();
        if (!force && listed_mtime_.value(path) == mtime)
            continue;
        listed_mtime_[path] = mtime;

        const QModelIndex parent = model_->index(path);
        QSet<QString> listed;
        for (int row = 0; row < model_->rowCount(parent); ++row)
            listed.insert(model_->fileName(model_->index(row, 0, parent)));

        // QFileSystemModel has no call to re-read a directory it has already listed, but index() of a path
        // it does not know yet adds that path as a new row - in place, so the selection and the expanded
        // directories stay as they are. Same filters as the model's own; only the names it lacks are
        // passed, as index() costs ~10 us a call and a CBF sweep is thousands of files. There is no
        // counterpart for removal: an entry deleted by another host stays listed (a local delete is seen
        // by the model's own watching).
        const QDir dir(path);
        const QStringList names = dir.entryList(model_->nameFilters(),
                                                QDir::AllDirs | QDir::Files | QDir::NoDotAndDotDot,
                                                QDir::Unsorted);
        for (const QString &name : names) {
            if (!listed.contains(name)) {
                model_->index(dir.filePath(name));
                added = true;
            }
        }
    }
    if (!added)
        return;
    // Rows added this way land at the end of their directory. Setting the same name filters again marks
    // the model as needing a sort, which sort() then does at once instead of on the next event loop pass.
    model_->setNameFilters(model_->nameFilters());
    model_->sort(0);
    // A row sorted in above the first visible one would push everything below it down; keep the first
    // visible row where it was - unless the view is scrolled to the very top, where a new row should show.
    if (top.isValid() && tree_->verticalScrollBar()->value() > 0)
        tree_->scrollTo(top, QAbstractItemView::PositionAtTop);
}

void JFJochViewerFileBrowser::FollowPath(const QString &path) {
    const QString absolute = QFileInfo(path).absoluteFilePath();
    // Containment by path components, not by string prefix, so /data/foo2 is not inside /data/foo.
    // relativeFilePath hands back an absolute path when there is no relative route at all (a file on
    // another Windows drive).
    const QString relative = QDir(model_->rootPath()).relativeFilePath(absolute);
    if (QDir::isAbsolutePath(relative) || relative == ".." || relative.startsWith("../"))
        return;

    const QModelIndex index = proxy_->mapFromSource(model_->index(absolute));
    if (!index.isValid())
        return;

    tree_->setCurrentIndex(index);
    tree_->scrollTo(index);
}

void JFJochViewerFileBrowser::onBrowseClicked() {
    const QString dir = QFileDialog::getExistingDirectory(this, "Select data root", root_edit_->text());
    if (!dir.isEmpty())
        SetRoot(dir);
}

void JFJochViewerFileBrowser::onRootEditingFinished() {
    SetRoot(root_edit_->text());
}

void JFJochViewerFileBrowser::onDoubleClicked(const QModelIndex &index) {
    const QModelIndex source = proxy_->mapToSource(index);
    if (!source.isValid() || model_->isDir(source))
        return;   // directories: let the tree's own expand/collapse handle the double click
    emit openDataset(QDir::toNativeSeparators(model_->filePath(source)), 0, 1, false);
}