#include "denote_frontmatter.h"

#include <QRegularExpression>
#include <QStringList>

namespace Denote {

FileType fileTypeFromExtension(const QString &ext)
{
    const QString lower = ext.toLower();
    if (lower == QStringLiteral(".md") || lower == QStringLiteral(".markdown"))
        return FileType::MdYaml;
    if (lower == QStringLiteral(".org"))
        return FileType::Org;
    if (lower == QStringLiteral(".txt"))
        return FileType::Txt;
    return FileType::Unknown;
}

bool supportsFrontMatter(const QString &ext)
{
    return fileTypeFromExtension(ext) != FileType::Unknown;
}

// --- YAML frontmatter (Markdown) ---

static FrontMatter parseYamlFrontMatter(const QString &text)
{
    FrontMatter fm;

    // Match --- delimited block at start of file
    static const QRegularExpression reFm(
        QStringLiteral("\\A---\\n(.*?)\\n---"),
        QRegularExpression::DotMatchesEverythingOption);
    auto m = reFm.match(text);
    if (!m.hasMatch())
        return fm;

    const QString block = m.captured(1);

    // title: value or title: "value"
    static const QRegularExpression reTitle(
        QStringLiteral("(?:^|\\n)title:\\s*\"?([^\"\\n]+)\"?"));
    auto mt = reTitle.match(block);
    if (mt.hasMatch())
        fm.title = mt.captured(1).trimmed();

    // identifier: value
    static const QRegularExpression reId(
        QStringLiteral("(?:^|\\n)identifier:\\s*\"?(\\d{8}T\\d{6})\"?"));
    auto mi = reId.match(block);
    if (mi.hasMatch())
        fm.identifier = mi.captured(1);

    // signature: value
    static const QRegularExpression reSig(
        QStringLiteral("(?:^|\\n)signature:\\s*\"?([^\"\\n]+)\"?"));
    auto ms = reSig.match(block);
    if (ms.hasMatch())
        fm.signature = ms.captured(1).trimmed();

    // tags: [tag1, tag2] or tags:\n- tag1\n- tag2
    // Inline form first
    static const QRegularExpression reTagsInline(
        QStringLiteral("(?:^|\\n)tags:\\s*\\[([^\\]]*?)\\]"));
    auto mtags = reTagsInline.match(block);
    if (mtags.hasMatch()) {
        const QString raw = mtags.captured(1);
        const auto parts = raw.split(QLatin1Char(','), Qt::SkipEmptyParts);
        for (const auto &p : parts) {
            QString tag = p.trimmed();
            tag.remove(QLatin1Char('"'));
            if (!tag.isEmpty())
                fm.tags.append(tag);
        }
    } else {
        // List form: tags:\n  - tag1\n  - tag2
        static const QRegularExpression reTagsList(
            QStringLiteral("(?:^|\\n)tags:\\s*\\n((?:\\s*-\\s*[^\\n]+\\n?)+)"));
        auto mlist = reTagsList.match(block);
        if (mlist.hasMatch()) {
            static const QRegularExpression reItem(
                QStringLiteral("\\s*-\\s*\"?([^\"\\n]+)\"?"));
            auto it = reItem.globalMatch(mlist.captured(1));
            while (it.hasNext()) {
                auto item = it.next();
                QString tag = item.captured(1).trimmed();
                if (!tag.isEmpty())
                    fm.tags.append(tag);
            }
        }
    }

    return fm;
}

static QByteArray marshalYaml(const FrontMatter &fm)
{
    QString out;
    out += QStringLiteral("---\n");
    out += QStringLiteral("title: ") + fm.title + QStringLiteral("\n");
    out += QStringLiteral("tags: [");
    for (int i = 0; i < fm.tags.size(); ++i) {
        if (i > 0)
            out += QStringLiteral(", ");
        out += fm.tags[i];
    }
    out += QStringLiteral("]\n");
    out += QStringLiteral("identifier: ") + fm.identifier + QStringLiteral("\n");
    if (!fm.signature.isEmpty())
        out += QStringLiteral("signature: ") + fm.signature + QStringLiteral("\n");
    out += QStringLiteral("---\n");
    return out.toUtf8();
}

// --- Org-mode frontmatter ---

static FrontMatter parseOrgFrontMatter(const QString &text)
{
    FrontMatter fm;

    // #+title: value
    static const QRegularExpression reTitle(
        QStringLiteral("(?:^|\\n)#\\+title:\\s*(.+)"),
        QRegularExpression::CaseInsensitiveOption);
    auto m = reTitle.match(text);
    if (m.hasMatch())
        fm.title = m.captured(1).trimmed();

    // #+identifier: value
    static const QRegularExpression reId(
        QStringLiteral("(?:^|\\n)#\\+identifier:\\s*(\\d{8}T\\d{6})"),
        QRegularExpression::CaseInsensitiveOption);
    auto mi = reId.match(text);
    if (mi.hasMatch())
        fm.identifier = mi.captured(1);

    // #+filetags: :tag1:tag2:
    static const QRegularExpression reTags(
        QStringLiteral("(?:^|\\n)#\\+filetags:\\s*:?([^\\n]+)"),
        QRegularExpression::CaseInsensitiveOption);
    auto mt = reTags.match(text);
    if (mt.hasMatch()) {
        QString raw = mt.captured(1).trimmed();
        // Remove surrounding colons
        if (raw.startsWith(QLatin1Char(':')))
            raw = raw.mid(1);
        if (raw.endsWith(QLatin1Char(':')))
            raw.chop(1);
        fm.tags = raw.split(QLatin1Char(':'), Qt::SkipEmptyParts);
    }

    // #+signature: value
    static const QRegularExpression reSig(
        QStringLiteral("(?:^|\\n)#\\+signature:\\s*(.+)"),
        QRegularExpression::CaseInsensitiveOption);
    auto ms = reSig.match(text);
    if (ms.hasMatch())
        fm.signature = ms.captured(1).trimmed();

    return fm;
}

static QByteArray marshalOrg(const FrontMatter &fm)
{
    QString out;
    out += QStringLiteral("#+title: ") + fm.title + QStringLiteral("\n");
    if (!fm.tags.isEmpty()) {
        out += QStringLiteral("#+filetags: :") + fm.tags.join(QLatin1Char(':'))
             + QStringLiteral(":\n");
    }
    out += QStringLiteral("#+identifier: ") + fm.identifier + QStringLiteral("\n");
    if (!fm.signature.isEmpty())
        out += QStringLiteral("#+signature: ") + fm.signature + QStringLiteral("\n");
    return out.toUtf8();
}

// --- Plain text frontmatter ---

static FrontMatter parseTxtFrontMatter(const QString &text)
{
    FrontMatter fm;

    // title: value
    static const QRegularExpression reTitle(
        QStringLiteral("(?:^|\\n)title:\\s*(.+)"),
        QRegularExpression::CaseInsensitiveOption);
    auto m = reTitle.match(text);
    if (m.hasMatch())
        fm.title = m.captured(1).trimmed();

    // identifier: value
    static const QRegularExpression reId(
        QStringLiteral("(?:^|\\n)identifier:\\s*(\\d{8}T\\d{6})"),
        QRegularExpression::CaseInsensitiveOption);
    auto mi = reId.match(text);
    if (mi.hasMatch())
        fm.identifier = mi.captured(1);

    // tags: tag1, tag2
    static const QRegularExpression reTags(
        QStringLiteral("(?:^|\\n)tags:\\s*(.+)"),
        QRegularExpression::CaseInsensitiveOption);
    auto mt = reTags.match(text);
    if (mt.hasMatch()) {
        fm.tags = mt.captured(1).split(QLatin1Char(','), Qt::SkipEmptyParts);
        for (auto &t : fm.tags)
            t = t.trimmed();
    }

    // signature: value
    static const QRegularExpression reSig(
        QStringLiteral("(?:^|\\n)signature:\\s*(.+)"),
        QRegularExpression::CaseInsensitiveOption);
    auto ms = reSig.match(text);
    if (ms.hasMatch())
        fm.signature = ms.captured(1).trimmed();

    return fm;
}

static QByteArray marshalTxt(const FrontMatter &fm)
{
    QString out;
    out += QStringLiteral("title: ") + fm.title + QStringLiteral("\n");
    if (!fm.tags.isEmpty())
        out += QStringLiteral("tags: ") + fm.tags.join(QStringLiteral(", ")) + QStringLiteral("\n");
    out += QStringLiteral("identifier: ") + fm.identifier + QStringLiteral("\n");
    if (!fm.signature.isEmpty())
        out += QStringLiteral("signature: ") + fm.signature + QStringLiteral("\n");
    out += QStringLiteral("--\n");
    return out.toUtf8();
}

// --- Public API ---

FrontMatter parseFrontMatter(const QByteArray &content, FileType type)
{
    const QString text = QString::fromUtf8(content);

    switch (type) {
    case FileType::MdYaml:
        return parseYamlFrontMatter(text);
    case FileType::Org:
        return parseOrgFrontMatter(text);
    case FileType::Txt:
        return parseTxtFrontMatter(text);
    case FileType::Unknown:
        return {};
    }
    return {};
}

QByteArray marshalFrontMatter(const FrontMatter &fm, FileType type)
{
    switch (type) {
    case FileType::MdYaml:
        return marshalYaml(fm);
    case FileType::Org:
        return marshalOrg(fm);
    case FileType::Txt:
        return marshalTxt(fm);
    case FileType::Unknown:
        return {};
    }
    return {};
}

QString extractBody(const QByteArray &content, FileType type)
{
    const QString text = QString::fromUtf8(content);

    switch (type) {
    case FileType::MdYaml: {
        // Body is everything after closing ---
        static const QRegularExpression reFm(
            QStringLiteral("\\A---\\n.*?\\n---\\n?"),
            QRegularExpression::DotMatchesEverythingOption);
        auto m = reFm.match(text);
        if (m.hasMatch())
            return text.mid(m.capturedEnd());
        return text;
    }
    case FileType::Org: {
        // Body starts after the last #+key: line at the top
        static const QRegularExpression reHeader(
            QStringLiteral("\\A((?:#\\+[^\\n]+\\n)*)"));
        auto m = reHeader.match(text);
        if (m.hasMatch())
            return text.mid(m.capturedEnd());
        return text;
    }
    case FileType::Txt: {
        // Body starts after the -- separator line
        int idx = text.indexOf(QStringLiteral("\n--\n"));
        if (idx >= 0)
            return text.mid(idx + 4);
        return text;
    }
    case FileType::Unknown:
        return text;
    }
    return text;
}

} // namespace Denote