/*
   SPDX-FileCopyrightText: 2016-2026 Laurent Montel <montel@kde.org>

   SPDX-License-Identifier: LGPL-2.0-or-later
*/

#include "urlhashing.h"

#include <QCryptographicHash>
#include <QDebug>

using namespace Qt::Literals;
using namespace WebEngineViewer;
using namespace Qt::Literals::StringLiterals;

UrlHashing::UrlHashing(const QUrl &url)
    : mUrl(url)
{
}

UrlHashing::~UrlHashing() = default;

QString UrlHashing::canonicalizeUrl(QUrl url)
{
    if (url.isEmpty()) {
        return {};
    }
    QString path = url.path();
    if (url.path().isEmpty()) {
        url.setPath(u"/"_s);
    } else {
        // First, remove tab (0x09), CR (0x0d), and LF (0x0a) characters from the URL. Do not remove escape sequences for these characters (e.g. '%0a').
        path.remove(u'\t');
        path.remove(u'\r');
        path.remove(u'\n');

        // remove repeated leading slashes
        while (path.startsWith("//"_L1)) {
            path.removeAt(0);
        }

        // In the URL, percent-escape all characters that are <= ASCII 32, >= 127, "#", or "%". The escapes should use uppercase hex characters.
        // TODO

        url.setPath(path);
    }
    // Remove all leading and trailing dots.
#if 0
    QString hostname = url.host();
    qDebug() << " hostname" << hostname;
    while (!hostname.isEmpty() && hostname.at(0) == u'.') {
        hostname.remove(0, 1);
    }
    qDebug() << "BEFORE hostname" << hostname;
    for (int i = hostname.length(); i >= 0; --i) {
        if (hostname.at(i) == u'.') {
            hostname.remove(i);
        } else {
            break;
        }
    }
    qDebug() << "AFTER hostname" << hostname;
    mUrl.setHost(hostname);
#endif
    QByteArray urlEncoded = url.toEncoded(QUrl::RemoveFragment | QUrl::NormalizePathSegments | QUrl::EncodeUnicode | QUrl::RemoveUserInfo | QUrl::RemovePort
                                          | QUrl::RemovePassword);
    // qDebug() << "BEFORE  urlEncoded" <<urlEncoded;
    urlEncoded.replace(QByteArrayLiteral("%25"), QByteArrayLiteral("%"));
    // qDebug() << "AFTER  urlEncoded" <<urlEncoded;
    return QString::fromLatin1(urlEncoded);
}

QStringList UrlHashing::generatePathsToCheck(const QString &str, const QString &query)
{
    QStringList pathToCheck;
    if (str.isEmpty()) {
        return pathToCheck;
    }
    const int strLength(str.length());
    for (int i = 0; i < strLength; ++i) {
        // We check 5 element => 4 here and host if necessary
        if (pathToCheck.count() == 4) {
            break;
        }
        if (str.at(i) == u'/') {
            if (i == 0) {
                pathToCheck << u"/"_s;
            } else {
                pathToCheck << str.left(i + 1);
            }
        }
    }
    if (!pathToCheck.isEmpty() && pathToCheck.at(pathToCheck.count() - 1) != str) {
        pathToCheck << str;
    }
    if (!query.isEmpty()) {
        pathToCheck << str + u'?' + query;
    }
    return pathToCheck;
}

QStringList UrlHashing::generateHostsToCheck(const QString &str)
{
    QStringList hostToCheck;
    if (str.isEmpty()) {
        return hostToCheck;
    }
    const int strLength(str.length());
    bool lastElement = true;
    for (int i = (strLength - 1); i > 0; --i) {
        // We need to check just 5 element => 4 splits hosts + current host
        if (hostToCheck.count() == 4) {
            break;
        }
        if (str.at(i) == u'.') {
            if (lastElement) {
                lastElement = false;
            } else {
                hostToCheck << str.right(strLength - i - 1);
            }
        }
    }
    hostToCheck << str;
    return hostToCheck;
}

QHash<QByteArray, QByteArray> UrlHashing::hashList() const
{
    QHash<QByteArray, QByteArray> lst;
    if (mUrl.isValid()) {
        const QString result = WebEngineViewer::UrlHashing::canonicalizeUrl(mUrl);
        const QUrl url(result);
        const QStringList hosts = WebEngineViewer::UrlHashing::generateHostsToCheck(url.host());
        const QStringList paths = WebEngineViewer::UrlHashing::generatePathsToCheck(url.path(), url.query());

        for (const QString &host : hosts) {
            for (const QString &path : paths) {
                const QString str = host + path;
                QByteArray ba = QCryptographicHash::hash(str.toLatin1(), QCryptographicHash::Sha256);
                QByteArray baShort = ba;
                baShort.truncate(4);
                lst.insert(ba, baShort);
                // qDebug() << " ba " << ba.toBase64();
            }
        }
    }
    return lst;
}
