// Copyright (C) 2021 The Qt Company Ltd.
// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR LGPL-3.0-only OR GPL-2.0-only OR GPL-3.0-only

// This file is included from qnsview.mm, and only used to organize the code

@implementation QNSView (ComplexText)

// ------------- Text insertion -------------

/*
    Inserts the given text, potentially replacing existing text.

    The text input management system calls this as a result of:

     - A normal key press, via [NSView interpretKeyEvents:] or
       [NSInputContext handleEvent:]

     - An input method finishing (confirming) composition

     - Pressing a key in the Keyboard Viewer panel

     - Confirming an inline input area (accent popup e.g.)

    \a replacementRange refers to the existing text to replace.
    Under normal circumstances this is {NSNotFound, 0}, and the
    implementation should replace either the existing marked text,
    the current selection, or just insert the text at the current
    cursor location.
*/
- (void)insertText:(id)text replacementRange:(NSRange)replacementRange
{
    qCDebug(lcQpaKeys).nospace() << "Inserting \"" << text << "\""
        << ", replacing range " << replacementRange;

    if (m_composingText.isEmpty()) {
        // The input method may have transformed the incoming key event
        // to text that doesn't match what the original key event would
        // have produced, for example when 'Pinyin - Simplified' does smart
        // replacement of quotes. If that's the case we can't rely on
        // handleKeyEvent for sending the text.
        auto *currentEvent = NSApp.currentEvent;
        NSString *eventText = currentEvent.type == NSEventTypeKeyDown
                           || currentEvent.type == NSEventTypeKeyUp
                                ? currentEvent.characters : nil;

        if ([text isEqualToString:eventText]) {
            // We do not send input method events for simple text input,
            // and instead let handleKeyEvent send the key event.
            qCDebug(lcQpaKeys) << "Ignoring text insertion for simple text";
            m_sendKeyEvent = true;
            return;
        }
    }

    QObject *focusObject = m_platformWindow->window()->focusObject();
    if (queryInputMethod(focusObject)) {
        QInputMethodEvent inputMethodEvent;

        const bool isAttributedString = [text isKindOfClass:NSAttributedString.class];
        QString commitString = QString::fromNSString(isAttributedString ? [text string] : text);

        // Ensure we have a valid replacement range
        replacementRange = [self sanitizeReplacementRange:replacementRange];

        // Qt's QInputMethodEvent has different semantics for the replacement
        // range than AppKit does, so we need to sanitize the range first.
        auto [replaceFrom, replaceLength] = [self inputMethodRangeForRange:replacementRange];

        if (replaceFrom == NSNotFound) {
            qCWarning(lcQpaKeys) << "Failed to compute valid replacement range for text insertion";
            inputMethodEvent.setCommitString(commitString);
        } else {
            qCDebug(lcQpaKeys) << "Replacing from" << replaceFrom << "with length" << replaceLength
                << "based on replacement range" << replacementRange;
            inputMethodEvent.setCommitString(commitString, replaceFrom, replaceLength);
        }

        QCoreApplication::sendEvent(focusObject, &inputMethodEvent);
    }

    m_composingText.clear();
    m_composingFocusObject = nullptr;
}

- (void)insertNewline:(id)sender
{
    Q_UNUSED(sender);

    // Depending on the input method, pressing enter may
    // result in simply dismissing the input method editor,
    // without confirming the composition. In other cases
    // it may confirm the composition as well. And in some
    // cases the IME will produce an explicit new line, which
    // brings us here.

    // Semantically, the input method has asked us to insert
    // a newline, and we should do so via an QInputMethodEvent,
    // either directly or via [self insertText:@"\r"]. This is
    // also how NSTextView handles the command. But, if we did,
    // we would bypass all the code in Qt (and clients) that
    // assume that pressing the return key results in a key
    // event, for example the QLineEdit::returnPressed logic.
    // To ensure that clients will still see the Qt::Key_Return
    // key event, we send it as a normal key event.

    // But, we can not fall back to handleKeyEvent for this,
    // as the original key event may have text that reflects
    // the combination of the inserted text and the newline,
    // e.g. "~\r". We have already inserted the composition,
    // so we need to follow up with a single newline event.

    KeyEvent newlineEvent(m_currentlyInterpretedKeyEvent ?
        m_currentlyInterpretedKeyEvent : NSApp.currentEvent);
    newlineEvent.type = QEvent::KeyPress;

    const bool isEnter = newlineEvent.modifiers & Qt::KeypadModifier;
    newlineEvent.key = isEnter ? Qt::Key_Enter : Qt::Key_Return;
    newlineEvent.text = isEnter ? QLatin1Char(kEnterCharCode)
                                : QLatin1Char(kReturnCharCode);
    newlineEvent.nativeVirtualKey = isEnter ? kVK_ANSI_KeypadEnter
                                            : kVK_Return;

    qCDebug(lcQpaKeys) << "Inserting newline via" << newlineEvent;
    newlineEvent.sendWindowSystemEvent(m_platformWindow->window());
}

// ------------- Text composition -------------

/*
    Updates the composed text, potentially replacing existing text.

    The NSTextInputClient protocol refers to composed text as "marked",
    since it is "marked differently from the selection, using temporary
    attributes that affect only display, not layout or storage.""

    The concept maps to the preeditString of our QInputMethodEvent.

    \a selectedRange refers to the part of the marked text that
    is considered selected, for example when composing text with
    multiple clause segments (Hiragana - Kana e.g.).

    \a replacementRange refers to the existing text to replace.
    Under normal circumstances this is {NSNotFound, 0}, and the
    implementation should replace either the existing marked text,
    the current selection, or just insert the text at the current
    cursor location. But when initiating composition of existing
    committed text (Hiragana - Kana e.g.), the range will be valid.
*/
- (void)setMarkedText:(id)text selectedRange:(NSRange)selectedRange replacementRange:(NSRange)replacementRange
{
    qCDebug(lcQpaKeys).nospace() << "Marking \"" << text << "\""
        << " with selected range " << selectedRange
        << ", replacing range " << replacementRange;

    const bool isAttributedString = [text isKindOfClass:NSAttributedString.class];
    QString preeditString = QString::fromNSString(isAttributedString ? [text string] : text);

    QList<QInputMethodEvent::Attribute> preeditAttributes;

    // The QInputMethodEvent::Cursor specifies that the length
    // determines whether the cursor is visible or not, but uses
    // logic opposite of that of native AppKit application, where
    // the cursor is visible if there's no selection, and hidden
    // if there's a selection. Instead of passing on the length
    // directly we need to inverse the logic.
    const bool showCursor = !selectedRange.length;
    preeditAttributes << QInputMethodEvent::Attribute(
        QInputMethodEvent::Cursor, selectedRange.location, showCursor);

    // QInputMethodEvent::Selection unfortunately doesn't apply to the
    // preedit text, and QInputMethodEvent::Cursor which does, doesn't
    // support setting a selection. Until we've introduced attributes
    // that allow us to propagate the preedit selection semantically
    // we resort to styling the selection via the TextFormat attribute,
    // so that the preedit selection is visible to the user.
    QTextCharFormat selectionFormat;
    auto *platformTheme = QGuiApplicationPrivate::platformTheme();
    auto *systemPalette = platformTheme->palette();
    selectionFormat.setBackground(systemPalette->color(QPalette::Highlight));
    preeditAttributes << QInputMethodEvent::Attribute(
        QInputMethodEvent::TextFormat,
        selectedRange.location, selectedRange.length,
        selectionFormat);

    int index = 0;
    int composingLength = preeditString.length();
    while (index < composingLength) {
        NSRange range = NSMakeRange(index, composingLength - index);

        static NSDictionary *defaultMarkedTextAttributes = []{
            NSTextView *textView = [[NSTextView new] autorelease];
            return [textView.markedTextAttributes retain];
        }();

        NSDictionary *attributes = isAttributedString
            ? [text attributesAtIndex:index longestEffectiveRange:&range inRange:range]
            : defaultMarkedTextAttributes;

        qCDebug(lcQpaKeys) << "Decorating range" << range << "based on" << attributes;
        QTextCharFormat format;

        if (NSNumber *underlineStyle = attributes[NSUnderlineStyleAttributeName]) {
            format.setFontUnderline(true);
            NSUnderlineStyle style = underlineStyle.integerValue;
            if (style & NSUnderlineStylePatternDot)
                format.setUnderlineStyle(QTextCharFormat::DotLine);
            else if (style & NSUnderlineStylePatternDash)
                format.setUnderlineStyle(QTextCharFormat::DashUnderline);
            else if (style & NSUnderlineStylePatternDashDot)
                format.setUnderlineStyle(QTextCharFormat::DashDotLine);
            if (style & NSUnderlineStylePatternDashDotDot)
                format.setUnderlineStyle(QTextCharFormat::DashDotDotLine);
            else
                format.setUnderlineStyle(QTextCharFormat::SingleUnderline);

            // Unfortunately QTextCharFormat::UnderlineStyle does not distinguish
            // between NSUnderlineStyle{Single,Thick,Double}, which is used by CJK
            // input methods to highlight the selected clause segments.
        }
        if (NSColor *underlineColor = attributes[NSUnderlineColorAttributeName])
            format.setUnderlineColor(qt_mac_toQColor(underlineColor));
        if (NSColor *foregroundColor = attributes[NSForegroundColorAttributeName])
            format.setForeground(qt_mac_toQColor(foregroundColor));
        if (NSColor *backgroundColor = attributes[NSBackgroundColorAttributeName])
            format.setBackground(qt_mac_toQColor(backgroundColor));

        if (format != QTextCharFormat()) {
            preeditAttributes << QInputMethodEvent::Attribute(
                QInputMethodEvent::TextFormat, range.location, range.length, format);
        }

        index = range.location + range.length;
    }

    // Ensure we have a valid replacement range
    replacementRange = [self sanitizeReplacementRange:replacementRange];

    // Qt's QInputMethodEvent has different semantics for the replacement
    // range than AppKit does, so we need to sanitize the range first.
    auto [replaceFrom, replaceLength] = [self inputMethodRangeForRange:replacementRange];

    // Update the composition, now that we've computed the replacement range
    m_composingText = preeditString;

    if (QObject *focusObject = m_platformWindow->window()->focusObject()) {
        m_composingFocusObject = focusObject;
        if (queryInputMethod(focusObject)) {
            QInputMethodEvent event(preeditString, preeditAttributes);
            if (replaceLength > 0) {
                // The input method may extend the preedit into already
                // committed text. If so, we need to replace existing text
                // by committing an empty string.
                qCDebug(lcQpaKeys) << "Replacing from" << replaceFrom << "with length"
                    << replaceLength << "based on replacement range" << replacementRange;
                event.setCommitString(QString(), replaceFrom, replaceLength);
            }
            QCoreApplication::sendEvent(focusObject, &event);
        }
    }
}

- (NSArray<NSString *> *)validAttributesForMarkedText
{
    return @[
        NSUnderlineColorAttributeName,
        NSUnderlineStyleAttributeName,
        NSForegroundColorAttributeName,
        NSBackgroundColorAttributeName
    ];
}

- (BOOL)hasMarkedText
{
    return !m_composingText.isEmpty();
}

/*
    Returns the range of marked text or {cursorPosition, 0} if there's none.

    This maps to the location and length of the current preedit (composited) string.

    The returned range measures from the start of the receiver’s text storage,
    that is, from 0 to the document length.
*/
- (NSRange)markedRange
{
    QObject *focusObject = m_platformWindow->window()->focusObject();
    if (auto queryResult = queryInputMethod(focusObject, Qt::ImAbsolutePosition)) {
        int absoluteCursorPosition = queryResult.value(Qt::ImAbsolutePosition).toInt();

        // The cursor position as reflected by Qt::ImAbsolutePosition is not
        // affected by the offset of the cursor in the preedit area. That means
        // that when composing text, the cursor position stays the same, at the
        // preedit insertion point, regardless of where the cursor is positioned within
        // the preedit string by the QInputMethodEvent::Cursor attribute. This means
        // we can use the cursor position to determine the range of the marked text.

        // The NSTextInputClient documentation says {NSNotFound, 0} should be returned if there
        // is no marked text, but in practice NSTextView seems to report {cursorPosition, 0},
        // so we do the same.
        return NSMakeRange(absoluteCursorPosition, m_composingText.length());
    } else {
        return {NSNotFound, 0};
    }
}

/*
    Confirms the marked (composed) text.

    The marked text is accepted as if it had been inserted normally,
    and the preedit string is cleared.

    If there is no marked text this method has no effect.
*/
- (void)unmarkText
{
    // FIXME: Match cancelComposingText in early exit and focus object handling

    qCDebug(lcQpaKeys) << "Unmarking" << m_composingText
        << "for focus object" << m_composingFocusObject;

    if (!m_composingText.isEmpty()) {
        QObject *focusObject = m_platformWindow->window()->focusObject();
        if (queryInputMethod(focusObject)) {
            QInputMethodEvent e;
            e.setCommitString(m_composingText);
            QCoreApplication::sendEvent(focusObject, &e);
        }
    }

    m_composingText.clear();
    m_composingFocusObject = nullptr;
}

/*
    Cancels composition.

    The marked text is discarded, and the preedit string is cleared.

    If there is no marked text this method has no effect.
*/
- (void)cancelComposingText
{
    if (m_composingText.isEmpty())
        return;

    qCDebug(lcQpaKeys) << "Canceling composition" << m_composingText
        << "for focus object" << m_composingFocusObject;

    if (queryInputMethod(m_composingFocusObject)) {
        QInputMethodEvent e;
        QCoreApplication::sendEvent(m_composingFocusObject, &e);
    }

    m_composingText.clear();
    m_composingFocusObject = nullptr;
}

// ------------- Key binding command handling -------------

- (void)doCommandBySelector:(SEL)selector
{
    // Note: if the selector cannot be invoked, then doCommandBySelector:
    // should not pass this message up the responder chain (nor should it
    // call super, as the NSResponder base class would in that case pass
    // the message up the responder chain, which we don't want). We will
    // pass the originating key event up the responder chain if applicable.

    qCDebug(lcQpaKeys) << "Trying to perform command" << selector;
    if (![self tryToPerform:selector with:self]) {
        m_sendKeyEvent = true;

        // The text input system determined that the key event was not
        // meant for text insertion, and instead asked us to treat it
        // as a (possibly noop) command. This typically happens for key
        // events with either ⌘ or ⌃, function keys such as F1-F35,
        // arrow keys, etc. We reflect that when sending the key event
        // later on, by removing the text from the event, so that the
        // event does not result in text insertion on the client side.
        m_sendKeyEventWithoutText = true;
    }
}

// ------------- Various text properties -------------

/*
    Returns the range of selected text, or {cursorPosition, 0} if there's none.

    The returned range measures from the start of the receiver’s text storage,
    that is, from 0 to the document length.
*/
- (NSRange)selectedRange
{
    QObject *focusObject = m_platformWindow->window()->focusObject();
    if (auto queryResult = queryInputMethod(focusObject,
            Qt::ImCursorPosition | Qt::ImAbsolutePosition | Qt::ImAnchorPosition)) {

        // Unfortunately the Qt::InputMethodQuery values are all relative
        // to the start of the current editing block (paragraph), but we
        // need them in absolute values relative to the entire text.
        // Luckily we have one property, Qt::ImAbsolutePosition, that
        // we can use to compute the offset.
        int cursorPosition = queryResult.value(Qt::ImCursorPosition).toInt();
        int absoluteCursorPosition = queryResult.value(Qt::ImAbsolutePosition).toInt();
        int absoluteOffset = absoluteCursorPosition - cursorPosition;

        int anchorPosition = absoluteOffset + queryResult.value(Qt::ImAnchorPosition).toInt();
        int selectionStart = anchorPosition >= absoluteCursorPosition ? absoluteCursorPosition : anchorPosition;
        int selectionEnd = selectionStart == anchorPosition ? absoluteCursorPosition : anchorPosition;
        int selectionLength = selectionEnd - selectionStart;

        // Note: The cursor position as reflected by these properties are not
        // affected by the offset of the cursor in the preedit area. That means
        // that when composing text, the cursor position stays the same, at the
        // preedit insertion point, regardless of where the cursor is positioned within
        // the preedit string by the QInputMethodEvent::Cursor attribute.

        // The NSTextInputClient documentation says {NSNotFound, 0} should be returned if there is no
        // selection, but in practice NSTextView seems to report {cursorPosition, 0}, so we do the same.
        return NSMakeRange(selectionStart, selectionLength);
    } else {
        return {NSNotFound, 0};
    }
}

/*
    Returns an attributed string derived from the given range
    in the underlying focus object's text storage.

    Input methods may call this with a proposed range that is
    out of bounds. For example, the InkWell text input service
    may ask for the contents of the text input client that extends
    beyond the document's range. To remedy this we always compute
    the intersection between the proposed range and the available
    text.

    If the intersection is completely outside of the available text
    this method returns nil.
*/
- (NSAttributedString *)attributedSubstringForProposedRange:(NSRange)range actualRange:(NSRangePointer)actualRange
{
    QObject *focusObject = m_platformWindow->window()->focusObject();
    if (auto queryResult = queryInputMethod(focusObject,
            Qt::ImAbsolutePosition | Qt::ImTextBeforeCursor | Qt::ImTextAfterCursor)) {
        const int absoluteCursorPosition = queryResult.value(Qt::ImAbsolutePosition).toInt();
        const QString textBeforeCursor = queryResult.value(Qt::ImTextBeforeCursor).toString();
        const QString textAfterCursor = queryResult.value(Qt::ImTextAfterCursor).toString();

        // The documentation doesn't say whether the marked text should be included
        // in the available text, but observing NSTextView shows that this is the
        // case, so we follow suit.
        const QString availableText = textBeforeCursor + m_composingText + textAfterCursor;
        const NSRange availableRange = NSMakeRange(absoluteCursorPosition - textBeforeCursor.length(),
                                  availableText.length());

        const NSRange intersectedRange = NSIntersectionRange(range, availableRange);
        if (actualRange)
            *actualRange = intersectedRange;

        if (!intersectedRange.length)
            return nil;

        NSString *substring = QStringView(availableText).mid(
            intersectedRange.location - availableRange.location,
            intersectedRange.length).toNSString();

        return [[[NSAttributedString alloc] initWithString:substring] autorelease];

    } else {
        return nil;
    }
}

- (NSRect)firstRectForCharacterRange:(NSRange)range actualRange:(NSRangePointer)actualRange
{
    Q_UNUSED(range);
    Q_UNUSED(actualRange);

    QWindow *window = m_platformWindow->window();
    if (queryInputMethod(window->focusObject())) {
        QRect cursorRect = qApp->inputMethod()->cursorRectangle().toRect();
        cursorRect.moveBottomLeft(window->mapToGlobal(cursorRect.bottomLeft()));
        return QCocoaScreen::mapToNative(cursorRect);
    } else {
        return NSZeroRect;
    }
}

- (NSUInteger)characterIndexForPoint:(NSPoint)point
{
    // We don't support cursor movements using mouse while composing.
    Q_UNUSED(point);
    return NSNotFound;
}

// ------------- Helper functions -------------

/*
    Sanitizes the replacement range, ensuring it's valid.

    If \a range is not valid the range of the current
    marked text will be used.

    If there's no marked text the range of the current
    selection will be used.

    If there's no selection the range will be {cursorPosition, 0}.
*/
- (NSRange)sanitizeReplacementRange:(NSRange)range
{
    if (range.location != NSNotFound)
        return range; // Use as is

    // If the replacement range is not specified we are expected to compute
    // the range ourselves, based on the current state of the input context.

    const auto markedRange = [self markedRange];
    if (markedRange.location != NSNotFound)
        return markedRange;
    else
        return [self selectedRange];
}

/*
    Computes the QInputMethodEvent commit string range,
    based on the NSTextInputClient replacement range.

    The two APIs have different semantics.
*/
- (std::pair<long long, long long>)inputMethodRangeForRange:(NSRange)range
{
    long long replaceFrom = range.location;
    long long replaceLength = range.length;

    const auto markedRange = [self markedRange];
    const auto selectedRange = [self selectedRange];

    // The QInputMethodEvent replacement start is relative to the start
    // of the marked text (the location of the preedit string).
    if (markedRange.location != NSNotFound)
        replaceFrom -= markedRange.location;
    else
        replaceFrom = 0;

    // The replacement length of QInputMethodEvent already includes
    // the selection, as the documentation says that "If the widget
    // has selected text, the selected text should get removed."
    replaceLength -= selectedRange.length;

    // The replacement length of QInputMethodEvent already includes
    // the preedit string, as the documentation says that "When doing
    // replacement, the area of the preedit string is ignored".
    replaceLength -= markedRange.length;

    // What we're left with is any _additional_ replacement.
    // Make sure it's valid before passing it on.
    replaceLength = qMax(0ll, replaceLength);

    return {replaceFrom, replaceLength};
}

@end
