#include "KeyboardController.h"
#include "TextRules.h"

#include "engine/InputEngine.h"
#include "layout/LayoutModel.h"

#include <xkbcommon/xkbcommon-keysyms.h>

// ShiftMode mirrors ShiftState::Mode for QML.
static_assert(int(KeyboardController::ShiftMode::Off) == int(ShiftState::Mode::Off));
static_assert(int(KeyboardController::ShiftMode::Once) == int(ShiftState::Mode::Once));
static_assert(int(KeyboardController::ShiftMode::Locked) == int(ShiftState::Mode::Locked));

namespace {
// Enough history for the text rules; fields may report megabytes.
constexpr qsizetype MaxTextBefore = 256;
}

KeyboardController::KeyboardController(InputEngine &engine, LayoutModel &model, QObject *parent)
    : QObject(parent)
    , m_engine(engine)
    , m_model(model)
{
    connect(&m_backspaceRepeater, &KeyRepeater::repeat, this, &KeyboardController::deleteBackward);
}

KeyboardController::ShiftMode KeyboardController::shiftMode() const
{
    return ShiftMode(m_shift.mode());
}

void KeyboardController::keyDown(const KeyDef &key, qint64 timeMs)
{
    switch (key.type) {
    case KeyType::Shift:
        changeShift([&] { m_shift.press(timeMs); });
        break;
    case KeyType::Backspace:
        deleteBackward(false);
        m_backspaceRepeater.start();
        break;
    case KeyType::LayerSwitch:
        m_layerBeforeSwitch = m_model.layerName();
        m_model.setLayer(key.target);
        break;
    default:
        break; // everything else acts on release
    }
}

void KeyboardController::keyUp(const KeyDef &key, KeyOutput output, const QString &alternate, qint64)
{
    switch (key.type) {
    case KeyType::Shift:
        changeShift([&] { m_shift.release(); });
        break;
    case KeyType::Backspace:
        m_backspaceRepeater.stop();
        break;
    case KeyType::Character:
        if (output == KeyOutput::Alternate && !alternate.isEmpty())
            typeText(alternate);
        else if (output == KeyOutput::Flick && !key.flick.isEmpty())
            typeText(key.flick);
        else
            typeText(key.text(m_shift.isUppercase()));
        break;
    case KeyType::Space:
        typeText(QStringLiteral(" "));
        break;
    case KeyType::Enter:
        m_engine.sendKeysym(XKB_KEY_Return);
        m_textBefore += u'\n';
        autoCapitalize();
        break;
    case KeyType::Globe:
        Q_EMIT nextLayoutRequested();
        break;
    case KeyType::Dismiss:
        Q_EMIT dismissRequested();
        break;
    default:
        break;
    }
}

void KeyboardController::keyCancelled(const KeyDef &key)
{
    if (key.type == KeyType::Shift)
        changeShift([&] { m_shift.release(); });
    else if (key.type == KeyType::Backspace)
        m_backspaceRepeater.stop();
}

void KeyboardController::slideReleased(const KeyDef &target, qint64 timeMs)
{
    keyUp(target, KeyOutput::Primary, {}, timeMs);
    m_model.setLayer(m_layerBeforeSwitch);
}

void KeyboardController::moveCursor(QPoint steps)
{
    const auto repeat = [this](int count, quint32 keysym) {
        for (int i = 0; i < count; ++i)
            m_engine.sendKeysym(keysym);
    };
    repeat(qMax(0, steps.x()), XKB_KEY_Right);
    repeat(qMax(0, -steps.x()), XKB_KEY_Left);
    repeat(qMax(0, steps.y()), XKB_KEY_Down);
    repeat(qMax(0, -steps.y()), XKB_KEY_Up);
}

void KeyboardController::resetContext()
{
    m_context = {};
    m_textBefore.clear();
    autoCapitalize();
}

void KeyboardController::setContext(const TextContext &context)
{
    m_context = context;
    if (context.hasSurroundingText)
        m_textBefore = context.textBeforeCursor.right(MaxTextBefore);
    autoCapitalize();
}

void KeyboardController::setOptions(const TypingOptions &options)
{
    m_options = options;
    autoCapitalize();
}

void KeyboardController::typeText(const QString &text)
{
    if (text == u" " && m_options.doubleSpacePeriod && m_context.isProse()
        && TextRules::wantsDoubleSpacePeriod(m_textBefore)) {
        // "word " + space → "word. ", replacing the first space in place.
        m_engine.replaceBeforeCursor(QStringLiteral(" "), QStringLiteral(". "));
        m_textBefore.chop(1);
        m_textBefore += QStringLiteral(". ");
    } else {
        m_engine.commitText(text);
        m_textBefore += text;
    }
    m_textBefore = m_textBefore.right(MaxTextBefore);
    changeShift([&] { m_shift.characterTyped(); });
    autoCapitalize();
}

void KeyboardController::deleteBackward(bool wholeWord)
{
    m_engine.sendKeysym(XKB_KEY_BackSpace, wholeWord ? Qt::ControlModifier : Qt::NoModifier);
    m_textBefore = wholeWord ? TextRules::withoutLastWord(m_textBefore)
                             : TextRules::withoutLastCharacter(m_textBefore);
    autoCapitalize();
}

void KeyboardController::autoCapitalize()
{
    const bool capitalize = m_options.autoCapitalize && m_context.allowsAutoCapitalization()
                            && TextRules::startsSentence(m_textBefore);
    changeShift([&] { m_shift.setAutomatic(capitalize); });
}

template<typename Change>
void KeyboardController::changeShift(Change change)
{
    const ShiftState::Mode before = m_shift.mode();
    change();
    if (m_shift.mode() == before)
        return;
    m_model.setUppercase(m_shift.isUppercase());
    Q_EMIT shiftChanged();
}