#include "user_guide_dialog.h"

#include <QApplication>
#include <QDesktopServices>
#include <QDialogButtonBox>
#include <QFile>
#include <QListWidget>
#include <QSplitter>
#include <QTextBrowser>
#include <QTextStream>
#include <QUrl>
#include <QVBoxLayout>

namespace {

QString slugify(const QString& title)
{
    QString slug;
    slug.reserve(title.size());
    bool lastWasHyphen = false;
    for (const QChar& ch : title) {
        if (ch.isLetterOrNumber()) {
            slug += ch.toLower();
            lastWasHyphen = false;
        } else if (!lastWasHyphen && !slug.isEmpty()) {
            slug += QLatin1Char('-');
            lastWasHyphen = true;
        }
    }
    while (slug.endsWith(QLatin1Char('-'))) {
        slug.chop(1);
    }
    return slug;
}

}

UserGuideDialog::UserGuideDialog(QWidget* parent)
    : QDialog(parent), m_sectionList(nullptr), m_browser(nullptr)
{
    setWindowTitle(QStringLiteral("OrbitHub User Guide"));
    setWindowIcon(QApplication::windowIcon());
    resize(900, 640);

    auto* layout = new QVBoxLayout(this);
    layout->setContentsMargins(16, 16, 16, 16);
    layout->setSpacing(12);

    auto* splitter = new QSplitter(Qt::Horizontal, this);

    m_sectionList = new QListWidget(splitter);
    m_sectionList->setMaximumWidth(220);

    m_browser = new QTextBrowser(splitter);
    m_browser->setOpenExternalLinks(false);
    m_browser->setOpenLinks(false);

    splitter->addWidget(m_sectionList);
    splitter->addWidget(m_browser);
    splitter->setStretchFactor(0, 0);
    splitter->setStretchFactor(1, 1);

    auto* buttons = new QDialogButtonBox(QDialogButtonBox::Close, this);
    connect(buttons, &QDialogButtonBox::rejected, this, &QDialog::reject);
    connect(buttons, &QDialogButtonBox::accepted, this, &QDialog::accept);

    layout->addWidget(splitter, 1);
    layout->addWidget(buttons);

    loadSections();

    connect(m_sectionList,
            &QListWidget::currentRowChanged,
            this,
            [this](int row) { showSection(row); });
    connect(m_browser, &QTextBrowser::anchorClicked, this, &UserGuideDialog::onAnchorClicked);

    if (!m_sections.isEmpty()) {
        m_sectionList->setCurrentRow(0);
    }
}

void UserGuideDialog::loadSections()
{
    QFile file(QStringLiteral(":/docs/USER_GUIDE.md"));
    if (!file.open(QIODevice::ReadOnly | QIODevice::Text)) {
        return;
    }

    QTextStream stream(&file);
    const QString content = stream.readAll();
    const QStringList lines = content.split(QLatin1Char('\n'));

    QString currentTitle;
    QStringList currentLines;

    auto flushSection = [this, &currentTitle, &currentLines]() {
        if (currentTitle.isEmpty()) {
            return;
        }
        Section section;
        section.title = currentTitle;
        section.anchor = slugify(currentTitle);
        section.markdown = currentLines.join(QLatin1Char('\n'));
        m_sections.append(section);
    };

    for (const QString& line : lines) {
        if (line.startsWith(QStringLiteral("## "))) {
            flushSection();
            currentTitle = line.mid(3).trimmed();
            currentLines.clear();
        }
        currentLines.append(line);
    }
    flushSection();

    for (const Section& section : m_sections) {
        m_sectionList->addItem(section.title);
    }
}

void UserGuideDialog::showSection(int index)
{
    if (index < 0 || index >= m_sections.size()) {
        return;
    }
    m_browser->setMarkdown(m_sections[index].markdown);
}

void UserGuideDialog::onAnchorClicked(const QUrl& url)
{
    if (!url.scheme().isEmpty()) {
        QDesktopServices::openUrl(url);
        return;
    }

    const QString fragment = url.fragment();
    if (fragment.isEmpty()) {
        return;
    }

    for (int i = 0; i < m_sections.size(); ++i) {
        if (m_sections[i].anchor == fragment) {
            m_sectionList->setCurrentRow(i);
            return;
        }
    }
}