/*
    SPDX-FileCopyrightText: 2004, 2010 Joseph Wenninger <jowenn@kde.org>
    SPDX-FileCopyrightText: 2009 Milian Wolff <mail@milianw.de>
    SPDX-FileCopyrightText: 2014 Sven Brauch <svenbrauch@gmail.com>

    SPDX-License-Identifier: LGPL-2.0-or-later
*/

#include <QQueue>
#include <QRegularExpression>

#include <ktexteditor/movingcursor.h>
#include <ktexteditor/movingrange.h>

#include "kateconfig.h"
#include "katedocument.h"
#include "kateglobal.h"
#include "katepartdebug.h"
#include "kateregexpsearch.h"
#include "katerenderer.h"
#include "katetemplatehandler.h"
#include "kateundomanager.h"
#include "kateview.h"
#include "script/katescriptmanager.h"

using namespace KTextEditor;

#define ifDebug(x)

KateTemplateHandler::KateTemplateHandler(KTextEditor::ViewPrivate *view,
                                         Cursor position,
                                         const QString &templateString,
                                         const QString &script,
                                         KateUndoManager *undoManager)
    : QObject(view)
    , m_view(view)
    , m_undoManager(undoManager)
    , m_wholeTemplateRange()
    , m_internalEdit(false)
    , m_templateScript(script, KateScript::InputSCRIPT)
{
    Q_ASSERT(m_view);

    m_templateScript.setView(m_view);

    // remember selection, it will be lost when inserting the template
    std::unique_ptr<MovingRange> selection(doc()->newMovingRange(m_view->selectionRange(), MovingRange::DoNotExpand));

    m_undoManager->setAllowComplexMerge(true);

    {
        connect(doc(), &KTextEditor::DocumentPrivate::textInsertedRange, this, &KateTemplateHandler::slotTemplateInserted);
        KTextEditor::Document::EditingTransaction t(doc());
        // insert the raw template string
        if (!doc()->insertText(position, templateString)) {
            deleteLater();
            return;
        }
        // now there must be a range, caught by the textInserted slot
        Q_ASSERT(m_wholeTemplateRange);
        doc()->align(m_view, *m_wholeTemplateRange);
    }

    // before initialization, restore selection (if any) so user scripts can retrieve it
    m_view->setSelection(selection->toRange());
    initializeTemplate();
    // then delete the selected text (if any); it was replaced by the template
    doc()->removeText(selection->toRange());

    const bool have_editable_field = std::any_of(m_fields.constBegin(), m_fields.constEnd(), [](const TemplateField &field) {
        return (field.kind == TemplateField::Editable);
    });
    // only do complex stuff when required
    if (have_editable_field) {
        const auto views = doc()->views();
        for (View *view : views) {
            setupEventHandler(view);
        }

        // place the cursor at the first field and select stuff
        jump(1, true);

        connect(doc(), &KTextEditor::Document::viewCreated, this, &KateTemplateHandler::slotViewCreated);
        connect(doc(), &KTextEditor::DocumentPrivate::textInsertedRange, this, &KateTemplateHandler::updateDependentFields);
        connect(doc(), &KTextEditor::DocumentPrivate::textRemoved, this, &KateTemplateHandler::updateDependentFields);
        connect(doc(), &KTextEditor::Document::aboutToReload, this, &KateTemplateHandler::deleteLater);

    } else {
        // when no interesting ranges got added, we can terminate directly
        jumpToFinalCursorPosition();
        deleteLater();
    }
}

KateTemplateHandler::~KateTemplateHandler()
{
    m_undoManager->setAllowComplexMerge(false);
}

void KateTemplateHandler::sortFields()
{
    std::sort(m_fields.begin(), m_fields.end(), [](const TemplateField &l, const TemplateField &r) {
        // always sort the final cursor pos last
        if (l.kind == TemplateField::FinalCursorPosition) {
            return false;
        }
        if (r.kind == TemplateField::FinalCursorPosition) {
            return true;
        }
        // sort by range
        return l.range->toRange() < r.range->toRange();
    });
}

void KateTemplateHandler::jumpToNextRange()
{
    jump(+1);
}

void KateTemplateHandler::jumpToPreviousRange()
{
    jump(-1);
}

void KateTemplateHandler::jump(int by, bool initial)
{
    Q_ASSERT(by == 1 || by == -1);
    sortFields();

    // find (editable) field index of current cursor position
    int pos = -1;
    auto cursor = view()->cursorPosition();
    // if initial is not set, should start from the beginning (field -1)
    if (!initial) {
        pos = m_fields.indexOf(fieldForRange(KTextEditor::Range(cursor, cursor)));
    }

    // modulo field count and make positive
    auto wrap = [this](int x) -> unsigned int {
        x %= m_fields.size();
        return x + (x < 0 ? m_fields.size() : 0);
    };

    pos = wrap(pos);
    // choose field to jump to, including wrap-around
    auto choose_next_field = [this, by, wrap](unsigned int from_field_index) {
        for (int i = from_field_index + by;; i += by) {
            auto wrapped_i = wrap(i);
            auto kind = m_fields.at(wrapped_i).kind;
            if (kind == TemplateField::Editable || kind == TemplateField::FinalCursorPosition) {
                // found an editable field by walking into the desired direction
                return wrapped_i;
            }
            if (wrapped_i == from_field_index) {
                // nothing found, do nothing (i.e. keep cursor in current field)
                break;
            }
        }
        return from_field_index;
    };

    // jump
    auto jump_to_field = m_fields.at(choose_next_field(pos));
    view()->setCursorPosition(jump_to_field.range->toRange().start());
    if (!jump_to_field.touched) {
        // field was never edited by the user, so select its contents
        view()->setSelection(jump_to_field.range->toRange());
    }
}

void KateTemplateHandler::jumpToFinalCursorPosition()
{
    for (const auto &field : std::as_const(m_fields)) {
        if (field.kind == TemplateField::FinalCursorPosition) {
            view()->setCursorPosition(field.range->toRange().start());
            return;
        }
    }
    view()->setCursorPosition(m_wholeTemplateRange->end());
}

void KateTemplateHandler::slotTemplateInserted(Document * /*document*/, Range range)
{
    m_wholeTemplateRange.reset(doc()->newMovingRange(range, MovingRange::ExpandLeft | MovingRange::ExpandRight));

    disconnect(doc(), &KTextEditor::DocumentPrivate::textInsertedRange, this, &KateTemplateHandler::slotTemplateInserted);
}

KTextEditor::DocumentPrivate *KateTemplateHandler::doc() const
{
    return m_view->doc();
}

void KateTemplateHandler::slotViewCreated(Document *document, View *view)
{
    Q_ASSERT(document == doc());
    Q_UNUSED(document)
    setupEventHandler(view);
}

void KateTemplateHandler::setupEventHandler(View *view)
{
    view->focusProxy()->installEventFilter(this);
}

bool KateTemplateHandler::eventFilter(QObject *object, QEvent *event)
{
    // prevent indenting by eating the keypress event for TAB
    if (event->type() == QEvent::KeyPress || event->type() == QEvent::KeyRelease) {
        QKeyEvent *keyEvent = static_cast<QKeyEvent *>(event);
        if (keyEvent->key() == Qt::Key_Tab || keyEvent->key() == Qt::Key_Backtab) {
            if (!m_view->isCompletionActive()) {
                return true;
            }
        }
    }

    // actually offer shortcuts for navigation
    if (event->type() == QEvent::ShortcutOverride) {
        QKeyEvent *keyEvent = static_cast<QKeyEvent *>(event);

        if (keyEvent->key() == Qt::Key_Escape || (keyEvent->key() == Qt::Key_Return && keyEvent->modifiers() & Qt::AltModifier)) {
            // terminate
            jumpToFinalCursorPosition();
            view()->clearSelection();
            deleteLater();
            keyEvent->accept();
            return true;
        } else if (keyEvent->key() == Qt::Key_Tab && !m_view->isCompletionActive()) {
            if (keyEvent->modifiers() & Qt::ShiftModifier) {
                jumpToPreviousRange();
            } else {
                jumpToNextRange();
            }
            keyEvent->accept();
            return true;
        } else if (keyEvent->key() == Qt::Key_Backtab && !m_view->isCompletionActive()) {
            jumpToPreviousRange();
            keyEvent->accept();
            return true;
        }
    }

    return QObject::eventFilter(object, event);
}

/**
 * Returns an attribute with \p color as background with @p alpha alpha value.
 */
Attribute::Ptr getAttribute(QColor color, int alpha = 230)
{
    Attribute::Ptr attribute(new Attribute());
    color.setAlpha(alpha);
    attribute->setBackground(QBrush(color));
    return attribute;
}

void KateTemplateHandler::parseFields(const QString &templateText)
{
    // matches any field, i.e. the three forms ${foo}, ${foo=expr}, ${func()}
    // this also captures escaped fields, i.e. \\${foo} etc.
    static const QRegularExpression field(QStringLiteral("\\\\?\\${([^}]+)}"), QRegularExpression::UseUnicodePropertiesOption);
    // matches the "foo=expr" form within a match of the above expression
    static const QRegularExpression defaultField(QStringLiteral("\\w+=([^\\}]*)"), QRegularExpression::UseUnicodePropertiesOption);

    // compute start cursor of a match
    auto startOfMatch = [this, &templateText](const QRegularExpressionMatch &match) {
        const auto offset = match.capturedStart(0);
        const auto left = QStringView(templateText).left(offset);
        const auto nl = QLatin1Char('\n');
        const auto rel_lineno = left.count(nl);
        const auto start = m_wholeTemplateRange->start().toCursor();
        return Cursor(start.line(), rel_lineno == 0 ? start.column() : 0) + Cursor(rel_lineno, offset - left.lastIndexOf(nl) - 1);
    };

    // create a moving range spanning the given field
    auto createMovingRangeForMatch = [this, startOfMatch](const QRegularExpressionMatch &match) {
        auto matchStart = startOfMatch(match);
        return doc()->newMovingRange({matchStart, matchStart + Cursor(0, match.capturedLength(0))}, MovingRange::ExpandLeft | MovingRange::ExpandRight);
    };

    // list of escape backslashes to remove after parsing
    QVector<KTextEditor::Cursor> stripBackslashes;
    auto fieldMatch = field.globalMatch(templateText);
    while (fieldMatch.hasNext()) {
        const auto match = fieldMatch.next();
        if (match.captured(0).startsWith(QLatin1Char('\\'))) {
            // $ is escaped, not a field; mark the backslash for removal
            // prepend it to the list so the characters are removed starting from the
            // back and ranges do not move around
            stripBackslashes.prepend(startOfMatch(match));
            continue;
        }
        // a template field was found, instantiate a field object and populate it
        auto defaultMatch = defaultField.match(match.captured(0));
        const QString contents = match.captured(1);
        TemplateField f;
        f.range.reset(createMovingRangeForMatch(match));
        f.identifier = contents;
        f.kind = TemplateField::Editable;
        if (defaultMatch.hasMatch()) {
            // the field has a default value, i.e. ${foo=3}
            f.defaultValue = defaultMatch.captured(1);
            f.identifier = QStringView(contents).left(contents.indexOf(QLatin1Char('='))).trimmed().toString();
        } else if (f.identifier.contains(QLatin1Char('('))) {
            // field is a function call when it contains an opening parenthesis
            f.kind = TemplateField::FunctionCall;
        } else if (f.identifier == QLatin1String("cursor")) {
            // field marks the final cursor position
            f.kind = TemplateField::FinalCursorPosition;
        }
        for (const auto &other : std::as_const(m_fields)) {
            if (other.kind == TemplateField::Editable && !(f == other) && other.identifier == f.identifier) {
                // field is a mirror field
                f.kind = TemplateField::Mirror;
                break;
            }
        }
        m_fields.append(f);
    }

    // remove escape characters
    for (const auto &backslash : stripBackslashes) {
        doc()->removeText(KTextEditor::Range(backslash, backslash + Cursor(0, 1)));
    }
}

void KateTemplateHandler::setupFieldRanges()
{
    auto config = m_view->renderer()->config();
    auto editableAttribute = getAttribute(config->templateEditablePlaceholderColor(), 255);
    editableAttribute->setDynamicAttribute(Attribute::ActivateCaretIn, getAttribute(config->templateFocusedEditablePlaceholderColor(), 255));
    auto notEditableAttribute = getAttribute(config->templateNotEditablePlaceholderColor(), 255);

    // color the whole template
    m_wholeTemplateRange->setAttribute(getAttribute(config->templateBackgroundColor(), 200));

    // color all the template fields
    for (const auto &field : std::as_const(m_fields)) {
        field.range->setAttribute(field.kind == TemplateField::Editable ? editableAttribute : notEditableAttribute);
    }
}

void KateTemplateHandler::setupDefaultValues()
{
    for (const auto &field : std::as_const(m_fields)) {
        if (field.kind != TemplateField::Editable) {
            continue;
        }
        QString value;
        if (field.defaultValue.isEmpty()) {
            // field has no default value specified; use its identifier
            value = field.identifier;
        } else {
            // field has a default value; evaluate it with the JS engine
            value = m_templateScript.evaluate(field.defaultValue).toString();
        }
        doc()->replaceText(field.range->toRange(), value);
    }
}

void KateTemplateHandler::initializeTemplate()
{
    auto templateString = doc()->text(*m_wholeTemplateRange);
    parseFields(templateString);
    setupFieldRanges();
    setupDefaultValues();

    // call update for each field to set up the initial stuff
    for (int i = 0; i < m_fields.size(); i++) {
        auto &field = m_fields[i];
        ifDebug(qCDebug(LOG_KTE) << "update field:" << field.range->toRange();) updateDependentFields(doc(), field.range->toRange());
        // remove "user edited field" mark set by the above call since it's not a real edit
        field.touched = false;
    }
}

const KateTemplateHandler::TemplateField KateTemplateHandler::fieldForRange(KTextEditor::Range range) const
{
    for (const auto &field : m_fields) {
        if (field.range->contains(range.start()) || field.range->end() == range.start()) {
            return field;
        }
        if (field.kind == TemplateField::FinalCursorPosition && range.end() == field.range->end().toCursor()) {
            return field;
        }
    }
    return {};
}

void KateTemplateHandler::updateDependentFields(Document *document, Range range)
{
    Q_ASSERT(document == doc());
    Q_UNUSED(document);
    if (!m_undoManager->isActive()) {
        // currently undoing stuff; don't update fields
        return;
    }

    bool in_range = m_wholeTemplateRange->toRange().contains(range.start());
    bool at_end = m_wholeTemplateRange->toRange().end() == range.end() || m_wholeTemplateRange->toRange().end() == range.start();
    if (m_wholeTemplateRange->toRange().isEmpty() || (!in_range && !at_end)) {
        // edit outside template range, abort
        ifDebug(qCDebug(LOG_KTE) << "edit outside template range, exiting";) deleteLater();
        return;
    }

    if (m_internalEdit || range.isEmpty()) {
        // internal or null edit; for internal edits, don't do anything
        // to prevent unwanted recursion
        return;
    }

    ifDebug(qCDebug(LOG_KTE) << "text changed" << document << range;)

        // group all the changes into one undo transaction
        KTextEditor::Document::EditingTransaction t(doc());

    // find the field which was modified, if any
    sortFields();
    const auto changedField = fieldForRange(range);
    if (changedField.kind == TemplateField::Invalid) {
        // edit not within a field, nothing to do
        ifDebug(qCDebug(LOG_KTE) << "edit not within a field:" << range;) return;
    }
    if (changedField.kind == TemplateField::FinalCursorPosition && doc()->text(changedField.range->toRange()).isEmpty()) {
        // text changed at final cursor position: the user is done, so exit
        // this is not executed when the field's range is not empty: in that case this call
        // is for initial setup and we have to continue below
        ifDebug(qCDebug(LOG_KTE) << "final cursor changed:" << range;) deleteLater();
        return;
    }

    // turn off expanding left/right for all ranges except @p current;
    // this prevents ranges from overlapping each other when they are adjacent
    auto dontExpandOthers = [this](const TemplateField &current) {
        for (qsizetype i = 0; i < m_fields.size(); i++) {
            if (current.range != m_fields.at(i).range) {
                m_fields.at(i).range->setInsertBehaviors(MovingRange::DoNotExpand);
            } else {
                m_fields.at(i).range->setInsertBehaviors(MovingRange::ExpandLeft | MovingRange::ExpandRight);
            }
        }
    };

    // new contents of the changed template field
    const auto &newText = doc()->text(changedField.range->toRange());
    m_internalEdit = true;
    // go through all fields and update the contents of the dependent ones
    for (auto field = m_fields.begin(); field != m_fields.end(); field++) {
        if (field->kind == TemplateField::FinalCursorPosition) {
            // only relevant on first run
            doc()->replaceText(field->range->toRange(), QString());
        }

        if (*field == changedField) {
            // mark that the user changed this field
            field->touched = true;
        }

        // If this is mirrored field with the same identifier as the
        // changed one and the changed one is editable, mirror changes
        // edits to non-editable mirror fields are ignored
        if (field->kind == TemplateField::Mirror && changedField.kind == TemplateField::Editable && field->identifier == changedField.identifier) {
            // editable field changed, mirror changes
            dontExpandOthers(*field);
            doc()->replaceText(field->range->toRange(), newText);
        } else if (field->kind == TemplateField::FunctionCall) {
            // replace field by result of function call
            dontExpandOthers(*field);
            // build map of objects in the scope to pass to the function
            auto map = fieldMap();
            const auto &callResult = m_templateScript.evaluate(field->identifier, map);
            doc()->replaceText(field->range->toRange(), callResult.toString());
        }
    }
    m_internalEdit = false;
    updateRangeBehaviours();
}

void KateTemplateHandler::updateRangeBehaviours()
{
    KTextEditor::Cursor last = {-1, -1};
    for (int i = 0; i < m_fields.size(); i++) {
        auto field = m_fields.at(i);
        auto end = field.range->end().toCursor();
        auto start = field.range->start().toCursor();
        if (field.kind == TemplateField::FinalCursorPosition) {
            // final cursor position never grows
            field.range->setInsertBehaviors(MovingRange::DoNotExpand);
        } else if (start <= last) {
            // ranges are adjacent, only expand to the right to prevent overlap
            field.range->setInsertBehaviors(MovingRange::ExpandRight);
        } else {
            // ranges are not adjacent, can grow in both directions
            field.range->setInsertBehaviors(MovingRange::ExpandLeft | MovingRange::ExpandRight);
        }
        last = end;
    }
}

KateScript::FieldMap KateTemplateHandler::fieldMap() const
{
    KateScript::FieldMap map;
    for (const auto &field : m_fields) {
        if (field.kind != TemplateField::Editable) {
            // only editable fields are of interest to the scripts
            continue;
        }
        map.insert(field.identifier, QJSValue(doc()->text(field.range->toRange())));
    }
    return map;
}

KTextEditor::ViewPrivate *KateTemplateHandler::view() const
{
    return m_view;
}
