/*
MIT License

Copyright (c) 2026 Poul Sander

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE.

*/

#include "fsdirmodel.h"

#include <QFileIconProvider>

#include <algorithm>
#include <filesystem>
#include <vector>

namespace fs = std::filesystem;

// ---------------------------------------------------------------------------
// Static helpers
// ---------------------------------------------------------------------------

QList<FsDirModel::Node *> FsDirModel::listSubdirs(Node *parentNode)
{
    QList<Node *> result;
    try {
        std::vector<std::pair<std::string, std::string>> entries; // {nativePath, filename}

        for (const fs::directory_entry &entry :
             fs::directory_iterator(parentNode->nativePath.toStdString(),
                                    fs::directory_options::skip_permission_denied))
        {
            std::error_code ec;
            const std::string fname = entry.path().filename().native();
            if (fname.empty() || fname[0] == '.')
                continue;
            if (!entry.is_directory(ec))
                continue;
            entries.push_back({entry.path().native(), fname});
        }

        std::sort(entries.begin(), entries.end(),
                  [](const auto &a, const auto &b) { return a.second < b.second; });

        result.reserve(static_cast<qsizetype>(entries.size()));
        for (const auto &[npath, fname] : entries) {
            auto *child = new Node;
            child->nativePath  = QByteArray::fromStdString(npath);
            child->displayName = QString::fromLocal8Bit(fname.c_str(),
                                                        static_cast<qsizetype>(fname.size()));
            child->parent      = parentNode;
            result.append(child);
        }
    } catch (const fs::filesystem_error &) {}

    return result;
}

void FsDirModel::destroyChildren(Node *node)
{
    for (Node *child : node->children) {
        destroyChildren(child);
        delete child;
    }
    node->children.clear();
    node->populated = false;
}

// ---------------------------------------------------------------------------
// Construction / destruction
// ---------------------------------------------------------------------------

FsDirModel::FsDirModel(QObject *parent)
    : QAbstractItemModel(parent)
{
    m_virtualRoot.populated = true; // virtual root is always "populated"

    QFileIconProvider iconProvider;
    m_folderIcon = iconProvider.icon(QFileIconProvider::Folder);
}

FsDirModel::~FsDirModel()
{
    destroyChildren(&m_virtualRoot);
}

// ---------------------------------------------------------------------------
// Public API
// ---------------------------------------------------------------------------

void FsDirModel::setRootPath(const QString &path)
{
    setRootPath(QFile::encodeName(path));
}

void FsDirModel::setRootPath(const QByteArray &nativePath)
{
    beginResetModel();
    destroyChildren(&m_virtualRoot);

    if (!nativePath.isEmpty()) {
        auto *node = new Node;
        node->nativePath  = nativePath;
        // Display name = last path component (empty for "/", use "/" in that case)
        std::string fname = fs::path(nativePath.toStdString()).filename().native();
        node->displayName = fname.empty()
            ? QFile::decodeName(nativePath)
            : QString::fromLocal8Bit(fname.c_str(), static_cast<qsizetype>(fname.size()));
        node->parent      = &m_virtualRoot;
        m_virtualRoot.children.append(node);
    }

    endResetModel();
}

QModelIndex FsDirModel::rootIndex() const
{
    if (m_virtualRoot.children.isEmpty())
        return {};
    return createIndex(0, 0, m_virtualRoot.children.first());
}

QByteArray FsDirModel::filePath(const QModelIndex &index) const
{
    if (!index.isValid())
        return {};
    return nodeForIndex(index)->nativePath;
}

QModelIndex FsDirModel::indexForPath(const QByteArray &nativePath)
{
    if (nativePath.isEmpty() || m_virtualRoot.children.isEmpty())
        return {};

    const fs::path target(nativePath.toStdString());
    const fs::path root(m_virtualRoot.children.first()->nativePath.toStdString());

    // Collect the ancestry chain from root down to target
    std::vector<fs::path> chain;
    fs::path cur = target;
    while (cur != root) {
        chain.push_back(cur);
        fs::path up = cur.parent_path();
        if (up == cur)
            return {}; // reached filesystem root without finding model root
        cur = up;
    }
    // chain is [target, …, root_child]; reverse so we walk root→target
    std::reverse(chain.begin(), chain.end());

    // Start at the root path node
    Node *node = m_virtualRoot.children.first();
    QModelIndex idx = createIndex(0, 0, node);

    for (const fs::path &step : chain) {
        // Ensure this node's children are loaded
        if (!node->populated) {
            QList<Node *> children = listSubdirs(node);
            if (!children.isEmpty()) {
                beginInsertRows(idx, 0, children.size() - 1);
                node->children = children;
                node->populated = true;
                endInsertRows();
            } else {
                node->populated = true;
            }
        }

        // Find the child whose nativePath matches step
        const std::string stepStr = step.native();
        bool found = false;
        for (int i = 0; i < node->children.size(); ++i) {
            if (node->children[i]->nativePath.toStdString() == stepStr) {
                node = node->children[i];
                idx  = createIndex(i, 0, node);
                found = true;
                break;
            }
        }
        if (!found)
            return {};
    }

    return idx;
}

// ---------------------------------------------------------------------------
// QAbstractItemModel interface
// ---------------------------------------------------------------------------

FsDirModel::Node *FsDirModel::nodeForIndex(const QModelIndex &index) const
{
    if (!index.isValid())
        return const_cast<Node *>(&m_virtualRoot);
    return static_cast<Node *>(index.internalPointer());
}

QModelIndex FsDirModel::indexForNode(Node *node) const
{
    if (!node || node == &m_virtualRoot)
        return {};
    Node *parentNode = node->parent;
    int row = parentNode->children.indexOf(node);
    if (row < 0)
        return {};
    return createIndex(row, 0, node);
}

QModelIndex FsDirModel::index(int row, int column, const QModelIndex &parent) const
{
    if (column != 0)
        return {};

    Node *parentNode = nodeForIndex(parent);
    if (row < 0 || row >= parentNode->children.size())
        return {};

    return createIndex(row, 0, parentNode->children[row]);
}

QModelIndex FsDirModel::parent(const QModelIndex &index) const
{
    if (!index.isValid())
        return {};

    Node *node       = static_cast<Node *>(index.internalPointer());
    Node *parentNode = node->parent;

    if (!parentNode || parentNode == &m_virtualRoot)
        return {};

    return indexForNode(parentNode);
}

int FsDirModel::rowCount(const QModelIndex &parent) const
{
    return nodeForIndex(parent)->children.size();
}

int FsDirModel::columnCount(const QModelIndex &) const
{
    return 1;
}

QVariant FsDirModel::data(const QModelIndex &index, int role) const
{
    if (!index.isValid())
        return {};

    const Node *node = static_cast<const Node *>(index.internalPointer());

    switch (role) {
    case Qt::DisplayRole:
        return node->displayName;
    case Qt::DecorationRole:
        return m_folderIcon;
    default:
        return {};
    }
}

bool FsDirModel::hasChildren(const QModelIndex &parent) const
{
    const Node *node = nodeForIndex(parent);
    if (!node->populated)
        return true; // optimistic: show expand arrow until we actually look
    return !node->children.isEmpty();
}

bool FsDirModel::canFetchMore(const QModelIndex &parent) const
{
    return !nodeForIndex(parent)->populated;
}

void FsDirModel::fetchMore(const QModelIndex &parent)
{
    Node *node = nodeForIndex(parent);
    if (node->populated)
        return;

    QList<Node *> children = listSubdirs(node);
    node->populated = true;

    if (children.isEmpty())
        return;

    beginInsertRows(parent, 0, children.size() - 1);
    node->children = children;
    endInsertRows();
}