// 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 <QFileDialog>
#include <QSettings>
#include <QDir>

namespace {
    constexpr auto kDataRootEnvVar = "JUNGFRAUJOCH_DATA_ROOT";
    constexpr auto kSettingsKey = "fileBrowserRoot";

    // 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::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 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;

    return QDir::homePath();
}

JFJochViewerFileBrowser::JFJochViewerFileBrowser(QWidget *parent) : QWidget(parent) {
    auto *layout = new QVBoxLayout(this);
    layout->setContentsMargins(4, 4, 4, 4);

    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…");
    root_row->addWidget(root_edit_);
    root_row->addWidget(browse_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 among
    // files. The many _data_NNNNNN.h5 shards of a dataset are not meant to be opened directly.
    model_->setNameFilters({"*_master.h5", "*_process.h5"});
    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);

    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::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);
}