#include "line_edit_completer.h"

#include <QAbstractItemModel>
#include <QAbstractItemView>
#include <QChar>
#include <QCompleter>
#include <QFocusEvent>
#include <QItemSelectionModel>
#include <QKeyEvent>
#include <QModelIndex>
#include <QVariant>
#include <QtGlobal>
#include <qnamespace.h>

class QWidget;

LineEditCompleter::LineEditCompleter(QWidget *parent) : LineEditUnfocusable(parent)
{
}

void LineEditCompleter::addCompleter(QCompleter *c, CompleterTrigger trigger)
{
    c->setWidget(this);
    c->setCompletionMode(QCompleter::PopupCompletion);
    c->setCaseSensitivity(Qt::CaseInsensitive);
    connect(c, qOverload<const QString &>(&QCompleter::activated), this,
            qOverload<const QString &>(&LineEditCompleter::insertCompletion));

    completers.append({c, trigger});
}

bool LineEditCompleter::hasVisibleCompleterPopup() const
{
    for (const auto &info : completers) {
        if (info.completer->popup()->isVisible()) {
            return true;
        }
    }
    return false;
}

void LineEditCompleter::hideCompleterPopups()
{
    for (const auto &info : completers) {
        info.completer->popup()->hide();
    }
}

void LineEditCompleter::focusOutEvent(QFocusEvent *e)
{
    LineEditUnfocusable::focusOutEvent(e);

    // Commit completion when focus moves away via Tab if popup is visible.
    // Other focus losses (e.g. the unfocus shortcut / Escape) must simply close
    // the popup without inserting anything.
    bool popupWasVisible = false;
    for (auto &info : completers) {
        if (info.completer->popup()->isVisible()) {
            popupWasVisible = true;
            const QModelIndex currentIndex = info.completer->popup()->currentIndex();
            QString completionText;
            if (currentIndex.isValid()) {
                completionText = currentIndex.data().toString();
            } else {
                completionText = info.completer->currentCompletion();
            }
            if (!completionText.isEmpty()) {
                insertCompletion(info.completer, completionText);
            }
        }
    }
    hideCompleterPopups();

    if (popupWasVisible && e->reason() == Qt::TabFocusReason) {
        // Refocus the edit so Tab doesn't move focus away
        // Use a queued connection to ensure focus is restored after the focus change completes
        QMetaObject::invokeMethod(this, "setFocus", Qt::QueuedConnection);
        e->accept();
        return;
    }

    if (popupWasVisible) {
        return;
    }
}

void LineEditCompleter::keyPressEvent(QKeyEvent *event)
{
    if (event->key() == Qt::Key_Escape) {
        if (hasVisibleCompleterPopup()) {
            event->ignore();
            hideCompleterPopups();
            return;
        }
        LineEditUnfocusable::keyPressEvent(event);
        return;
    }

    if (event->key() == Qt::Key_Return || event->key() == Qt::Key_Enter || event->key() == Qt::Key_Space) {
        for (auto &info : completers) {
            if (info.completer->popup()->isVisible()) {
                event->ignore();
                const QModelIndex currentIndex = info.completer->popup()->currentIndex();
                QString completionText;
                if (currentIndex.isValid()) {
                    completionText = currentIndex.data().toString();
                } else {
                    completionText = info.completer->currentCompletion();
                }
                if (!completionText.isEmpty()) {
                    insertCompletion(info.completer, completionText);
                }
                hideCompleterPopups();
                return;
            }
        }
    }

    if (event->key() == Qt::Key_Tab) {
        // Let Tab proceed normally; focusOutEvent will handle completion if popup is visible
        LineEditUnfocusable::keyPressEvent(event);
        return;
    }

    LineEditUnfocusable::keyPressEvent(event);

    QString textValue = text();
    int cursorPos = cursorPosition();

    CompleterInfo *active = nullptr;
    QString prefix;

    // An open "[[" card link takes precedence over a mention: while the cursor is
    // inside it, an earlier "@" must not shadow the card completer.
    const int openCardPos = textValue.lastIndexOf("[[", cursorPos - 1);
    const int closeCardPos = openCardPos == -1 ? -1 : textValue.indexOf("]]", openCardPos + 2);
    const bool insideCardLink = openCardPos != -1 && (closeCardPos == -1 || closeCardPos >= cursorPos);

    for (auto &info : completers) {
        bool triggered = false;
        switch (info.trigger) {
            case CompleterTrigger::Mention: {
                if (insideCardLink) {
                    break;
                }
                int triggerPos = textValue.lastIndexOf("@", cursorPos - 1);
                if (triggerPos != -1 && (triggerPos == 0 || textValue[triggerPos - 1].isSpace())) {
                    triggered = true;
                    // Keep the "@" so the prefix matches the "@"-prefixed mention model entries.
                    prefix = textValue.mid(triggerPos, cursorPos - triggerPos);
                }
                break;
            }
            case CompleterTrigger::Card: {
                int triggerPos = textValue.lastIndexOf("[[", cursorPos - 1);
                int closePos = textValue.indexOf("]]", triggerPos + 2);
                if (triggerPos != -1 && (closePos == -1 || closePos >= cursorPos)) {
                    triggered = true;
                    prefix = textValue.mid(triggerPos + 2, cursorPos - (triggerPos + 2));
                }
                break;
            }
        }

        if (triggered) {
            active = &info;
            break;
        }
    }

    if (!active) {
        for (auto &info : completers) {
            info.completer->popup()->hide();
        }
        return;
    }

    active->completer->setCompletionPrefix(prefix);

    switch (active->trigger) {
        case CompleterTrigger::Card:
            emit cardPartialChanged(prefix);
            return;
        case CompleterTrigger::Mention:
            break;
    }

    active->completer->complete();

    // The popup opens without a current row, so nothing is highlighted and there
    // is no visual indication of what Enter will insert. Select the row that
    // currentCompletion() would use so the current mention stays visible.
    auto *completionModel = active->completer->completionModel();
    const int currentRow = active->completer->currentRow();
    if (currentRow >= 0 && currentRow < completionModel->rowCount()) {
        active->completer->popup()->selectionModel()->setCurrentIndex(
            completionModel->index(currentRow, active->completer->completionColumn()),
            QItemSelectionModel::ClearAndSelect | QItemSelectionModel::Rows);
    }
}

void LineEditCompleter::insertCompletion(const QString &completion)
{
    for (auto &info : completers) {
        if (info.completer == sender()) {
            insertCompletion(info.completer, completion);
            return;
        }
    }
}

void LineEditCompleter::insertCompletion(QCompleter *completer, const QString &completion)
{
    QString t = text();
    int pos = cursorPosition();

    for (const auto &info : completers) {
        if (info.completer != completer) {
            continue;
        }

        switch (info.trigger) {
            case CompleterTrigger::Card: {
                int triggerPos = t.lastIndexOf("[[", pos - 1);
                if (triggerPos == -1) {
                    return;
                }

                // If an earlier "[[" is still open it also encloses the cursor, so
                // replace from its start. Otherwise completing in text such as
                // "[[Opt[[Amok" would leave a stray "[[" behind.
                int startPos = triggerPos;
                for (int searchFrom = triggerPos; searchFrom > 0;) {
                    const int earlier = t.lastIndexOf("[[", searchFrom - 1);
                    if (earlier == -1) {
                        break;
                    }
                    const int earlierClose = t.indexOf("]]", earlier + 2);
                    if (earlierClose != -1 && earlierClose < pos) {
                        break;
                    }
                    startPos = earlier;
                    searchFrom = earlier;
                }

                // If the cursor sits inside an already-closed [[...]] pair, replace
                // the whole construct instead of leaving a duplicate closing bracket
                // behind.
                int insertEnd = pos;
                const int closePos = t.indexOf("]]", startPos + 2);
                if (closePos != -1 && closePos >= pos) {
                    insertEnd = closePos + 2;
                }

                QString after = t.mid(insertEnd);
                QString replaced = t.left(startPos + 2) + completion + "]] ";
                setText(replaced + after);
                setCursorPosition(replaced.length());
                return;
            }
            case CompleterTrigger::Mention: {
                int triggerPos = t.lastIndexOf("@", pos - 1);
                if (triggerPos == -1) {
                    return;
                }
                setText(t.replace(triggerPos, pos - triggerPos, completion + " "));
                setCursorPosition(triggerPos + completion.length() + 1);
                return;
            }
        }
    }
}