// Copyright 2010 Anders Bakken
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

#include "TextPagerCursor.hpp"
#include "TextPagerCursor_p.hpp"
#include "TextPagerDocument.hpp"
#include "TextPagerDocument_p.hpp"
#include "TextPagerEdit_p.hpp"
#include "TextPagerLayout_p.hpp"
#include "TextPagerEdit.hpp"

class SelectionChangedEmitter
{
public:
    SelectionChangedEmitter(TextPagerEdit* t) :
        selectionStart(-1),
        selectionEnd(-1),
        textEdit(t)
    {
        if (textEdit) {
            selectionStart = textEdit->textCursor().selectionStart();
            selectionEnd = textEdit->textCursor().selectionEnd();
        }
    }

    ~SelectionChangedEmitter()
    {
        if (textEdit) {
            const TextPagerCursor& cursor = textEdit->textCursor();
            if (((selectionStart != selectionEnd) != cursor.hasSelection()) || (selectionStart != selectionEnd && (selectionStart != cursor.selectionStart() || selectionEnd != cursor.selectionEnd()))) {
                QMetaObject::invokeMethod(textEdit, "selectionChanged");
            }
        }
    }

private:
    int selectionStart, selectionEnd;
    TextPagerEdit* textEdit;
};

TextPagerCursor::TextPagerCursor() :
    d(0),
    textEdit(0)
{
}

TextPagerCursor::TextPagerCursor(const TextPagerDocument* document, int pos, int anc) :
    d(0),
    textEdit(0)
{
    if (document) {
        const int documentSize = document->d->documentSize;
        if (pos < 0 || pos > documentSize || anc < -1 || anc > documentSize) {
#ifndef LAZYTEXTEDIT_AUTOTEST
            qWarning("Invalid cursor data %d %d - %d\n",
                     pos, anc, documentSize);
            Q_ASSERT(0);
#endif
            return;
        }
        d = new TextCursorSharedPrivate;
        d->document = const_cast<TextPagerDocument*>(document);
        d->position = pos;
        d->anchor = anc == -1 ? pos : anc;
        d->document->d->textCursors.insert(d);
    }
}

TextPagerCursor::TextPagerCursor(const TextPagerEdit* edit, int pos, int anc) :
    d(0),
    textEdit(0)
{
    if (edit) {
        TextPagerDocument* document = edit->document();
        const int documentSize = document->d->documentSize;
        if (pos < 0 || pos > documentSize || anc < -1 || anc > documentSize) {
#ifndef LAZYTEXTEDIT_AUTOTEST
            qWarning("Invalid cursor data %d %d - %d\n",
                     pos, anc, documentSize);
            Q_ASSERT(0);
#endif
            return;
        }
        d = new TextCursorSharedPrivate;
        d->document = const_cast<TextPagerDocument*>(document);
        d->position = pos;
        d->anchor = anc == -1 ? pos : anc;
        d->document->d->textCursors.insert(d);
    }
}

TextPagerCursor::TextPagerCursor(const TextPagerCursor& cursor) :
    d(cursor.d),
    textEdit(0)
{
    ref();
}

TextPagerCursor& TextPagerCursor::operator=(const TextPagerCursor& other)
{
    deref();
    d = other.d;
    textEdit = 0;
    ref();
    return *this;
}

TextPagerCursor::~TextPagerCursor()
{
    deref();
}

bool TextPagerCursor::isNull() const
{
    return !d || !d->document;
}

TextPagerDocument* TextPagerCursor::document() const
{
    return d ? d->document : 0;
}

void TextPagerCursor::setSelection(int pos, int length)  // can be negative
{
    setPosition(pos + length);
    if (length != 0)
        setPosition(pos, KeepAnchor);
}

void TextPagerCursor::setPosition(int pos, MoveMode mode)
{
    Q_ASSERT(!isNull());
    d->overrideColumn = -1;
    if (pos < 0 || pos > d->document->documentSize()) {
        clearSelection();
        return;
    }
    else if (pos == d->position && (mode == KeepAnchor || d->anchor == d->position)) {
        return;
    }

    SelectionChangedEmitter emitter(textEdit);
    detach();
    cursorChanged(false);

#if 0
    Link *link = d->document->links(pos, 1).value(0, 0);
    if (link && link->position < pos && link->position + link->size > pos) { // inside a link
        pos = (pos > d->position ? link->position + link->size : link->position);
    }
#endif

    if (mode == TextPagerCursor::MoveAnchor) {
        clearSelection();
    }

    d->position = pos;
    if (mode == MoveAnchor) {
        d->anchor = pos;
    }
    cursorChanged(true);
}

int TextPagerCursor::position() const
{
    return isNull() ? -1 : d->position;
}

int TextPagerCursor::anchor() const
{
    return isNull() ? -1 : d->anchor;
}

bool TextPagerCursor::movePosition(TextPagerCursor::MoveOperation op, TextPagerCursor::MoveMode mode, int n)
{
    if (!d || !d->document || n <= 0)
        return false;

    switch (op) {
        case Start:
        case StartOfLine:
        case End:
        case EndOfLine:
            n = 1;
            break;
        default:
            break;
    }

    if (n > 1) {
        while (n > 0 && movePosition(op, mode, 1))
            --n;
        return n == 0;
    }
    detach();

    switch (op) {
        case NoMove:
            return true;

        case PreviousCharacter:
        case NextCharacter:
            return movePosition(op == TextPagerCursor::PreviousCharacter
                                    ? TextPagerCursor::Left
                                    : TextPagerCursor::Right,
                                mode);

        case End:
        case Start:
            setPosition(op == TextPagerCursor::Start ? 0 : d->document->documentSize(), mode);
            break;

        case Up:
        case Down: {
            TextPagerLayout* textLayout = TextLayoutCacheManager::requestLayout(*this, 1);  // should I use 1?
            Q_ASSERT(textLayout);
            int index;
            bool currentIsLast;
            const QTextLine currentLine = textLayout->lineForPosition(d->position, 0,
                                                                      &index,
                                                                      &currentIsLast);
            Q_ASSERT(textLayout->lines.size() <= 1 || (index != -1 && currentLine.isValid()));
            if (!currentLine.isValid())
                return false;
            const int col = columnNumber();
            int targetLinePos;
            if (op == Up) {
                targetLinePos = d->position - col - 1;
                //             qDebug() << "I was at column" << col << "and position"
                //                      << d->position << "so naturally I can find the previous line around"
                //                      << (d->position - col - 1);
            }
            else {
                targetLinePos = d->position + currentLine.textLength() - col + (currentIsLast ? 1 : 0);
                //             qDebug() << "currentLine.textLength" << currentLine.textLength() << "col" << col
                //                      << "currentIsLast" << currentIsLast;
                // ### probably need to add only if last line in layout
            }
            if (targetLinePos < 0) {
                if (d->position == 0) {
                    return false;
                }
                else {
                    setPosition(0, mode);
                    return true;
                }
            }
            else if (targetLinePos >= d->document->documentSize()) {
                if (d->position == d->document->documentSize()) {
                    return false;
                }
                else {
                    setPosition(d->document->documentSize(), mode);
                    return true;
                }
            }
            int offsetInLine;

            const QTextLine targetLine = textLayout->lineForPosition(targetLinePos, &offsetInLine);
            if (!targetLine.isValid())
                return false;
            targetLinePos -= offsetInLine;  // targetLinePos should now be at col 0

            //         qDebug() << "finding targetLine at" << targetLinePos
            //                  << d->document->read(targetLinePos, 7)
            //                  << "d->position" << d->position
            //                  << "col" << col
            //                  << "offsetInLine" << offsetInLine;

            int gotoCol = qMax(d->overrideColumn, col);
            if (gotoCol > targetLine.textLength()) {
                d->overrideColumn = qMax(d->overrideColumn, gotoCol);
                gotoCol = targetLine.textLength();
            }
            const int overrideColumn = d->overrideColumn;
            setPosition(targetLinePos + gotoCol, mode);
            d->overrideColumn = overrideColumn;
            break;
        }

        case EndOfLine:
        case StartOfLine: {
            int offset;
            bool lastLine;
            TextPagerLayout* textLayout = TextLayoutCacheManager::requestLayout(*this, 1);
            QTextLine line = textLayout->lineForPosition(position(), &offset,
                                                         0, &lastLine);
            if (!line.isValid())
                return false;
            if (op == TextPagerCursor::StartOfLine) {
                setPosition(position() - offset, mode);
            }
            else {
                int pos = position() - offset + line.textLength();
                if (!lastLine)
                    --pos;
                setPosition(pos, mode);
            }
            break;
        }

        case StartOfBlock: {
            TextDocumentIterator it(d->document->d, d->position);
            const QLatin1Char newline('\n');
            while (it.hasPrevious() && it.previous() != newline)
                ;
            if (it.hasPrevious())
                it.next();
            setPosition(it.position(), mode);
            break;
        }
        case EndOfBlock: {
            TextDocumentIterator it(d->document->d, d->position);
            const QLatin1Char newline('\n');
            while (it.current() != newline && it.hasNext() && it.next() != newline)
                ;
            setPosition(it.position(), mode);
            break;
        }

        case StartOfWord:
        case PreviousWord:
        case WordLeft: {
            TextDocumentIterator it(d->document->d, d->position);

            while (it.hasPrevious()) {
                const QChar ch = it.previous();
                if (d->document->isWordCharacter(ch, it.position()))
                    break;
            }
            while (it.hasPrevious()) {
                const QChar ch = it.previous();
                if (!d->document->isWordCharacter(ch, it.position()))
                    break;
            }
            if (it.hasPrevious())
                it.next();
            setPosition(it.position(), mode);
            d->overrideColumn = -1;
            break;
        }

        case NextWord:
        case WordRight:
        case EndOfWord: {
            TextDocumentIterator it(d->document->d, d->position);
            while (it.hasNext()) {
                const QChar ch = it.next();
                if (d->document->isWordCharacter(ch, it.position()))
                    break;
            }
            while (it.hasNext()) {
                const QChar ch = it.next();
                if (!d->document->isWordCharacter(ch, it.position()))
                    break;
            }
            setPosition(it.position(), mode);
            d->overrideColumn = -1;
            break;
        }

        case PreviousBlock:
            movePosition(TextPagerCursor::StartOfBlock, mode);
            movePosition(TextPagerCursor::Left, mode);
            movePosition(TextPagerCursor::StartOfBlock, mode);
            break;

        case NextBlock:
            movePosition(TextPagerCursor::EndOfBlock, mode);
            movePosition(TextPagerCursor::Right, mode);
            return true;

        case Left:
        case Right:
            d->overrideColumn = -1;
            setPosition(qBound<int>(0, position() + (op == TextPagerCursor::Left ? -1 : 1),
                                    d->document->documentSize()),
                        mode);
            break;
    };

    return true;
}

void TextPagerCursor::select(SelectionType selection)
{
    if (!d || !d->document)
        return;

    clearSelection();

    switch (selection) {
        case LineUnderCursor:
            movePosition(StartOfLine);
            movePosition(EndOfLine, KeepAnchor);
            break;
        case WordUnderCursor:
            movePosition(StartOfWord);
            movePosition(EndOfWord, KeepAnchor);
            break;
        case BlockUnderCursor:
            movePosition(StartOfBlock);
            // also select the paragraph separator
            if (movePosition(PreviousBlock)) {
                movePosition(EndOfBlock);
                movePosition(NextBlock, KeepAnchor);
            }
            movePosition(EndOfBlock, KeepAnchor);
            break;
    }
}

bool TextPagerCursor::hasSelection() const
{
    return !isNull() && d->anchor != d->position;
}

void TextPagerCursor::clearSelection()
{
    Q_ASSERT(!isNull());
    if (hasSelection()) {
        detach();
        SelectionChangedEmitter emitter(textEdit);
        d->anchor = d->position;
    }
}

int TextPagerCursor::selectionStart() const
{
    return qMin(d->anchor, d->position);
}

int TextPagerCursor::selectionEnd() const
{
    return qMax(d->anchor, d->position);
}

int TextPagerCursor::selectionSize() const
{
    return selectionEnd() - selectionStart();
}


QString TextPagerCursor::selectedText() const
{
    if (isNull() || d->anchor == d->position)
        return QString();

    const int min = qMin(d->anchor, d->position);
    const int max = qMax(d->anchor, d->position);
    return d->document->read(min, max - min);
}

bool TextPagerCursor::atBlockStart() const
{
    Q_ASSERT(!isNull());
    return atStart() || d->document->read(d->position - 1, 1).at(0) == '\n';
}

bool TextPagerCursor::atBlockEnd() const
{
    Q_ASSERT(!isNull());
    return atEnd() || d->document->read(d->position, 1).at(0) == '\n';  // ### is this right?
}

bool TextPagerCursor::atStart() const
{
    Q_ASSERT(!isNull());
    return d->position == 0;
}

bool TextPagerCursor::atEnd() const
{
    Q_ASSERT(!isNull());
    return d->position == d->document->documentSize();
}


bool TextPagerCursor::operator!=(const TextPagerCursor& rhs) const
{
    return !(*this == rhs);
}

bool TextPagerCursor::operator<(const TextPagerCursor& rhs) const
{
    if (!d)
        return true;

    if (!rhs.d)
        return false;

    Q_ASSERT_X(d->document == rhs.d->document, "TextCursor::operator<",
               "cannot compare cursors attached to different documents");

    return d->position < rhs.d->position;
}

bool TextPagerCursor::operator<=(const TextPagerCursor& rhs) const
{
    return *this < rhs || *this == rhs;
}

bool TextPagerCursor::operator==(const TextPagerCursor& rhs) const
{
    if (isCopyOf(rhs))
        return true;

    if (!d || !rhs.d)
        return false;

    return (d->position == rhs.d->position && d->anchor == rhs.d->anchor && d->document == rhs.d->document);
}

bool TextPagerCursor::operator>=(const TextPagerCursor& rhs) const
{
    return *this > rhs || *this == rhs;
}

bool TextPagerCursor::operator>(const TextPagerCursor& rhs) const
{
    if (!d)
        return false;

    if (!rhs.d)
        return true;

    Q_ASSERT_X(d->document == rhs.d->document, "TextCursor::operator>=",
               "cannot compare cursors attached to different documents");

    return d->position > rhs.d->position;
}

bool TextPagerCursor::isCopyOf(const TextPagerCursor& other) const
{
    return d == other.d;
}

int TextPagerCursor::columnNumber() const
{
    Q_ASSERT(d && d->document);
    TextPagerLayout* textLayout = TextLayoutCacheManager::requestLayout(*this, 0);
    int col;
    textLayout->lineForPosition(d->position, &col);
    return col;
}

int TextPagerCursor::lineNumber() const
{
    Q_ASSERT(d && d->document);
    return d->document->lineNumber(position());
}

void TextPagerCursor::detach()
{
    Q_ASSERT(d);
    if (d->ref > 1) {
        d->ref.deref();
        TextCursorSharedPrivate* p = new TextCursorSharedPrivate;
        p->position = d->position;
        p->overrideColumn = d->overrideColumn;
        p->anchor = d->anchor;
        p->document = d->document;
        d->document->d->textCursors.insert(p);
        d = p;
    }
}

bool TextPagerCursor::ref()
{
    return d && d->ref.ref();
}

bool TextPagerCursor::deref()
{
    TextCursorSharedPrivate* dd = d;
    d = 0;
    if (dd && !dd->ref.deref()) {
        if (dd->document) {
            const bool removed = dd->document->d->textCursors.remove(dd);
            Q_ASSERT(removed);
            Q_UNUSED(removed)
        }
        delete dd;
        return false;
    }
    return true;
}

void TextPagerCursor::cursorChanged(bool ensureVisible)
{
    if (textEdit) {
        if (textEdit->d->cursorBlinkTimer.isActive())
            textEdit->d->cursorVisible = true;
        if (ensureVisible) {
            Q_EMIT textEdit->cursorPositionChanged(d->position);
            textEdit->ensureCursorVisible();
        }
        const QRect r = textEdit->cursorBlockRect(*this) & textEdit->viewport()->rect();
        if (!r.isNull()) {
            textEdit->viewport()->update(r);
        }
    }
}

bool TextPagerCursor::cursorMoveKeyEvent(QKeyEvent* e)
{
    MoveMode mode = MoveAnchor;
    MoveOperation op = NoMove;

    if (e == QKeySequence::MoveToNextChar) {
        op = Right;
    }
    else if (e == QKeySequence::MoveToPreviousChar) {
        op = Left;
    }
    else if (e == QKeySequence::SelectNextChar) {
        op = Right;
        mode = KeepAnchor;
    }
    else if (e == QKeySequence::SelectPreviousChar) {
        op = Left;
        mode = KeepAnchor;
    }
    else if (e == QKeySequence::SelectNextWord) {
        op = WordRight;
        mode = KeepAnchor;
    }
    else if (e == QKeySequence::SelectPreviousWord) {
        op = WordLeft;
        mode = KeepAnchor;
    }
    else if (e == QKeySequence::SelectStartOfLine) {
        op = StartOfLine;
        mode = KeepAnchor;
    }
    else if (e == QKeySequence::SelectEndOfLine) {
        op = EndOfLine;
        mode = KeepAnchor;
    }
    else if (e == QKeySequence::SelectStartOfBlock) {
        op = StartOfBlock;
        mode = KeepAnchor;
    }
    else if (e == QKeySequence::SelectEndOfBlock) {
        op = EndOfBlock;
        mode = KeepAnchor;
    }
    else if (e == QKeySequence::SelectStartOfDocument) {
        op = Start;
        mode = KeepAnchor;
    }
    else if (e == QKeySequence::SelectEndOfDocument) {
        op = End;
        mode = KeepAnchor;
    }
    else if (e == QKeySequence::SelectPreviousLine) {
        op = Up;
        mode = KeepAnchor;
    }
    else if (e == QKeySequence::SelectNextLine) {
        op = Down;
        mode = KeepAnchor;
#if 0
        {
            QTextBlock block = cursor.block();
            QTextLine line = currentTextLine(cursor);
            if (!block.next().isValid()
                && line.isValid()
                && line.lineNumber() == block.layout()->lineCount() - 1)
                op = End;
        }
#endif
    }
    else if (e == QKeySequence::MoveToNextWord) {
        op = WordRight;
    }
    else if (e == QKeySequence::MoveToPreviousWord) {
        op = WordLeft;
    }
    else if (e == QKeySequence::MoveToEndOfBlock) {
        op = EndOfBlock;
    }
    else if (e == QKeySequence::MoveToStartOfBlock) {
        op = StartOfBlock;
    }
    else if (e == QKeySequence::MoveToNextLine) {
        op = Down;
    }
    else if (e == QKeySequence::MoveToPreviousLine) {
        op = Up;
    }
    else if (e == QKeySequence::MoveToStartOfLine) {
        op = StartOfLine;
    }
    else if (e == QKeySequence::MoveToEndOfLine) {
        op = EndOfLine;
    }
    else if (e == QKeySequence::MoveToStartOfDocument) {
        op = Start;
    }
    else if (e == QKeySequence::MoveToEndOfDocument) {
        op = End;
    }
    else if (e == QKeySequence::MoveToNextPage || e == QKeySequence::MoveToPreviousPage || e == QKeySequence::SelectNextPage || e == QKeySequence::SelectPreviousPage) {
        const MoveMode mode = (e == QKeySequence::MoveToNextPage || e == QKeySequence::MoveToPreviousPage
                                   ? MoveAnchor
                                   : KeepAnchor);
        const MoveOperation operation = (e == QKeySequence::MoveToNextPage || e == QKeySequence::SelectNextPage
                                             ? Down
                                             : Up);
        int visibleLines = 10;
        if (textEdit)
            visibleLines = textEdit->d->visibleLines;
        for (int i = 0; i < visibleLines; ++i) {
            if (!movePosition(operation, mode))
                break;
        }
        return true;
    }
    else {
        return false;
    }
    return movePosition(op, mode);
}

int TextPagerCursor::viewportWidth() const
{
    return textEdit ? textEdit->viewport()->width() : d->viewportWidth;
}

void TextPagerCursor::setViewportWidth(int width)
{
    if (textEdit) {
        qWarning("It makes no sense to set the viewportWidth of a text cursor that belongs to a text edit. The actual viewportWidth will be used");
        return;
    }
    d->viewportWidth = width;
}

QChar TextPagerCursor::cursorCharacter() const
{
    Q_ASSERT(d && d->document);
    return d->document->readCharacter(d->anchor);
}

QString TextPagerCursor::cursorLine() const
{
    Q_ASSERT(d && d->document);
    int layoutIndex = -1;
    TextPagerLayout* textLayout = TextLayoutCacheManager::requestLayout(*this, 2);  // should I use 1?

    QTextLine line = textLayout->lineForPosition(position(), 0, &layoutIndex);
    Q_ASSERT(line.isValid());  // ### could this be legitimate?
    Q_ASSERT(textLayout);
    return textLayout->textLayouts.at(layoutIndex)->text().mid(line.textStart(), line.textLength());
    // ### there is a bug here. It doesn't seem to use the right
    // ### viewportWidth even though it is the textEdit's cursor
}

int TextPagerCursor::lineHeight() const
{
    int res = -1;
    Q_ASSERT(d && d->document);
    int layoutIndex = -1;
    TextPagerLayout* textLayout = TextLayoutCacheManager::requestLayout(*this, 2);
    QTextLine line = textLayout->lineForPosition(position(), 0, &layoutIndex);
    if (line.isValid())
        res = line.height();
    return res;
}


QString TextPagerCursor::wordUnderCursor() const
{
    Q_ASSERT(!isNull());
    return d->document->d->wordAt(d->position);
}

QString TextPagerCursor::paragraphUnderCursor() const
{
    Q_ASSERT(!isNull());
    return d->document->d->paragraphAt(d->position);
}

QDebug operator<<(QDebug dbg, const TextPagerCursor& cursor)
{
    QString ret = QString::fromLatin1("TextCursor(");
    if (cursor.isNull()) {
        ret.append(QLatin1String("null)"));
        dbg.maybeSpace() << ret;
    }
    else {
        if (!cursor.hasSelection()) {
            dbg << "anchor/position:" << cursor.anchor() << "character:" << cursor.cursorCharacter();
        }
        else {
            dbg << "anchor:" << cursor.anchor() << "position:" << cursor.position()
                << "selectionSize:" << cursor.selectionSize();
            QString selectedText;
            if (cursor.selectionSize() > 10) {
                selectedText = cursor.document()->read(cursor.selectionStart(), 7);
                selectedText.append("...");
            }
            else {
                selectedText = cursor.selectedText();
            }
            dbg << "selectedText:" << selectedText;
        }
    }
    return dbg.space();
}
