#include "DesktopEntry.hpp"

#include <QDir>
#include <QFile>
#include <QFileInfo>
#include <QLocale>
#include <QMap>
#include <QProcess>
#include <QStandardPaths>
#include <QtGlobal>

#include <utility>

namespace {

QString unquote(QString value)
{
    value = value.trimmed();
    if (value.size() >= 2) {
        const QChar first = value.front();
        const QChar last = value.back();
        if ((first == QLatin1Char('"') && last == QLatin1Char('"'))
            || (first == QLatin1Char('\'') && last == QLatin1Char('\''))) {
            value = value.mid(1, value.size() - 2);
        }
    }
    return value;
}

bool parseBool(const QString &value)
{
    const QString lowered = value.trimmed().toLower();
    return lowered == QLatin1String("true") || lowered == QLatin1String("1");
}

struct LocalizedValue
{
    QString fallback;
    QMap<QString, QString> locales;
};

void storeLocalized(LocalizedValue *target, const QString &key, const QString &prefix, const QString &value)
{
    if (key == prefix) {
        target->fallback = value;
        return;
    }

    const QString start = prefix + QLatin1Char('[');
    if (!key.startsWith(start) || !key.endsWith(QLatin1Char(']')))
        return;

    const QString locale = key.mid(start.size(), key.size() - start.size() - 1);
    if (!locale.isEmpty())
        target->locales.insert(locale, value);
}

QString resolveLocalized(const LocalizedValue &value, const QLocale &locale)
{
    const QString name = locale.name(); // e.g. en_US
    const QString language = name.section(QLatin1Char('_'), 0, 0);

    auto match = [&value](const QString &tag) -> QString {
        if (tag.isEmpty())
            return {};
        return value.locales.value(tag);
    };

    if (QString found = match(name); !found.isEmpty())
        return found;

    if (QString found = match(language); !found.isEmpty())
        return found;

    const int underscore = name.indexOf(QLatin1Char('_'));
    if (underscore > 0) {
        if (QString found = match(name.left(underscore)); !found.isEmpty())
            return found;
    }

    return value.fallback;
}

QString findTerminalEmulator()
{
    const QStringList candidates = {
        QStringLiteral("foot"),
        QStringLiteral("x-terminal-emulator"),
        QStringLiteral("kitty"),
        QStringLiteral("alacritty"),
        QStringLiteral("kgx"),
        QStringLiteral("gnome-terminal"),
        QStringLiteral("konsole"),
        QStringLiteral("xterm"),
    };

    for (const QString &name : candidates) {
        const QString path = QStandardPaths::findExecutable(name);
        if (!path.isEmpty())
            return path;
    }

    return {};
}

bool executableAvailable(const QString &command)
{
    if (command.isEmpty())
        return false;

    const QFileInfo info(command);
    if (info.isAbsolute())
        return info.isExecutable();

    return !QStandardPaths::findExecutable(command).isEmpty();
}

} // namespace

QStringList splitDesktopList(const QString &value)
{
    const QStringList raw = value.split(QLatin1Char(';'), Qt::SkipEmptyParts);
    QStringList cleaned;
    cleaned.reserve(raw.size());
    for (const QString &item : raw) {
        const QString trimmed = item.trimmed();
        if (!trimmed.isEmpty())
            cleaned.append(trimmed);
    }
    return cleaned;
}

QStringList currentDesktopIdentifiers()
{
    const QByteArray raw = qgetenv("XDG_CURRENT_DESKTOP");
    if (raw.isEmpty())
        return {QStringLiteral("NebulaOS")};

    QStringList ids;
    for (const QByteArray &part : raw.split(':')) {
        const QString id = QString::fromLocal8Bit(part).trimmed();
        if (!id.isEmpty())
            ids.append(id);
    }
    if (ids.isEmpty())
        ids.append(QStringLiteral("NebulaOS"));
    return ids;
}

QStringList applicationDirectories()
{
    QStringList dirs;

    QString dataHome = QString::fromLocal8Bit(qgetenv("XDG_DATA_HOME"));
    if (dataHome.isEmpty())
        dataHome = QDir::homePath() + QStringLiteral("/.local/share");
    dirs.append(QDir::cleanPath(dataHome + QStringLiteral("/applications")));

    QString dataDirs = QString::fromLocal8Bit(qgetenv("XDG_DATA_DIRS"));
    if (dataDirs.isEmpty())
        dataDirs = QStringLiteral("/usr/local/share:/usr/share");

    for (const QString &root : dataDirs.split(QLatin1Char(':'), Qt::SkipEmptyParts)) {
        const QString trimmed = root.trimmed();
        if (trimmed.isEmpty())
            continue;
        dirs.append(QDir::cleanPath(trimmed + QStringLiteral("/applications")));
    }

    dirs.removeDuplicates();
    return dirs;
}

QString resolveIconName(const QString &icon)
{
    if (icon.isEmpty())
        return {};

    const QFileInfo info(icon);
    if (info.isAbsolute())
        return icon;

    QString name = icon;
    if (name.endsWith(QLatin1String(".png"), Qt::CaseInsensitive)
        || name.endsWith(QLatin1String(".svg"), Qt::CaseInsensitive)
        || name.endsWith(QLatin1String(".xpm"), Qt::CaseInsensitive)) {
        name = QFileInfo(name).completeBaseName();
    }
    return name;
}

QStringList expandExec(const QString &exec, const DesktopEntry &entry)
{
    QString expanded;
    expanded.reserve(exec.size());

    for (int i = 0; i < exec.size(); ++i) {
        const QChar ch = exec.at(i);
        if (ch != QLatin1Char('%') || i + 1 >= exec.size()) {
            expanded.append(ch);
            continue;
        }

        const QChar code = exec.at(++i);
        auto trimTrailingSpace = [&expanded]() {
            if (expanded.endsWith(QLatin1Char(' ')))
                expanded.chop(1);
        };

        switch (code.toLatin1()) {
        case '%':
            expanded.append(QLatin1Char('%'));
            break;
        case 'f':
        case 'F':
        case 'u':
        case 'U':
        case 'd':
        case 'D':
        case 'n':
        case 'N':
        case 'v':
        case 'm':
            // File/URL/deprecated codes are omitted when launching without arguments.
            trimTrailingSpace();
            break;
        case 'c':
            expanded.append(QLatin1Char('"'));
            expanded.append(entry.name);
            expanded.append(QLatin1Char('"'));
            break;
        case 'k':
            expanded.append(QLatin1Char('"'));
            expanded.append(entry.filePath);
            expanded.append(QLatin1Char('"'));
            break;
        case 'i':
            if (!entry.icon.isEmpty()) {
                expanded.append(QStringLiteral("--icon \""));
                expanded.append(entry.icon);
                expanded.append(QLatin1Char('"'));
            } else {
                trimTrailingSpace();
            }
            break;
        default:
            trimTrailingSpace();
            break;
        }
    }

    const QStringList parts = QProcess::splitCommand(expanded.trimmed());
    return parts;
}

bool DesktopEntry::isLauncherVisible() const
{
    if (hidden || noDisplay)
        return false;
    if (exec.trimmed().isEmpty())
        return false;
    if (!tryExec.trimmed().isEmpty() && !executableAvailable(tryExec.trimmed()))
        return false;
    return true;
}

bool DesktopEntry::launch() const
{
    QStringList args = expandExec(exec, *this);
    if (args.isEmpty()) {
        qWarning("nebula: cannot launch %s: empty Exec", qPrintable(desktopId));
        return false;
    }

    QString program = args.takeFirst();
    if (program.isEmpty()) {
        qWarning("nebula: cannot launch %s: missing program", qPrintable(desktopId));
        return false;
    }

    if (terminal) {
        const QString term = findTerminalEmulator();
        if (term.isEmpty()) {
            qWarning("nebula: cannot launch %s: Terminal=true but no terminal emulator was found",
                     qPrintable(desktopId));
            return false;
        }
        QStringList wrapped;
        wrapped.append(QStringLiteral("-e"));
        wrapped.append(program);
        wrapped.append(args);
        args = std::move(wrapped);
        program = term;
    }

    const QString cwd = workingDirectory.isEmpty() ? QDir::homePath() : workingDirectory;
    qint64 pid = 0;
    if (!QProcess::startDetached(program, args, cwd, &pid)) {
        qWarning("nebula: failed to launch %s (%s)", qPrintable(desktopId), qPrintable(program));
        return false;
    }

    qInfo("nebula: launched %s (%s) pid %lld", qPrintable(desktopId), qPrintable(program), static_cast<long long>(pid));
    return true;
}

DesktopEntry parseDesktopEntryFile(const QString &filePath, const QString &desktopId)
{
    DesktopEntry entry;
    entry.filePath = filePath;
    entry.desktopId = desktopId;

    QFile file(filePath);
    if (!file.open(QIODevice::ReadOnly | QIODevice::Text))
        return entry;

    LocalizedValue names;
    LocalizedValue genericNames;
    LocalizedValue comments;
    QString type = QStringLiteral("Application");
    QStringList onlyShowIn;
    QStringList notShowIn;
    bool inDesktopEntry = false;

    while (!file.atEnd()) {
        QString line = QString::fromUtf8(file.readLine());
        if (!line.isEmpty() && line.back() == QLatin1Char('\n'))
            line.chop(1);
        if (!line.isEmpty() && line.back() == QLatin1Char('\r'))
            line.chop(1);

        const QString trimmed = line.trimmed();
        if (trimmed.isEmpty() || trimmed.startsWith(QLatin1Char('#')))
            continue;

        if (trimmed.startsWith(QLatin1Char('[')) && trimmed.endsWith(QLatin1Char(']'))) {
            inDesktopEntry = (trimmed == QLatin1String("[Desktop Entry]"));
            continue;
        }
        if (!inDesktopEntry)
            continue;

        const int equals = trimmed.indexOf(QLatin1Char('='));
        if (equals <= 0)
            continue;

        const QString key = trimmed.left(equals).trimmed();
        const QString value = unquote(trimmed.mid(equals + 1));

        if (key == QLatin1String("Type"))
            type = value;
        else if (key == QLatin1String("Exec"))
            entry.exec = value;
        else if (key == QLatin1String("TryExec"))
            entry.tryExec = value;
        else if (key == QLatin1String("Icon"))
            entry.icon = value;
        else if (key == QLatin1String("Path"))
            entry.workingDirectory = value;
        else if (key == QLatin1String("Categories"))
            entry.categories = splitDesktopList(value);
        else if (key == QLatin1String("Terminal"))
            entry.terminal = parseBool(value);
        else if (key == QLatin1String("Hidden"))
            entry.hidden = parseBool(value);
        else if (key == QLatin1String("NoDisplay"))
            entry.noDisplay = parseBool(value);
        else if (key == QLatin1String("OnlyShowIn"))
            onlyShowIn = splitDesktopList(value);
        else if (key == QLatin1String("NotShowIn"))
            notShowIn = splitDesktopList(value);
        else {
            storeLocalized(&names, key, QStringLiteral("Name"), value);
            storeLocalized(&genericNames, key, QStringLiteral("GenericName"), value);
            storeLocalized(&comments, key, QStringLiteral("Comment"), value);
        }
    }

    const QLocale locale = QLocale::system();
    entry.name = resolveLocalized(names, locale);
    entry.genericName = resolveLocalized(genericNames, locale);
    entry.comment = resolveLocalized(comments, locale);
    entry.icon = resolveIconName(entry.icon);

    if (entry.desktopId.isEmpty())
        entry.desktopId = QFileInfo(filePath).fileName();

    if (type != QLatin1String("Application")) {
        entry.hidden = true;
        return entry;
    }

    const QStringList desktops = currentDesktopIdentifiers();
    if (!onlyShowIn.isEmpty()) {
        bool matched = false;
        for (const QString &desktop : desktops) {
            if (onlyShowIn.contains(desktop)) {
                matched = true;
                break;
            }
        }
        if (!matched)
            entry.noDisplay = true;
    }
    for (const QString &desktop : desktops) {
        if (notShowIn.contains(desktop)) {
            entry.noDisplay = true;
            break;
        }
    }

    return entry;
}