<?php namespace Backend\Behaviors;

use Db;
use Lang;
use Event;
use Form as FormHelper;
use Backend\Classes\ControllerBehavior;
use ApplicationException;
use October\Rain\Database\Model;

/**
 * Relation Controller Behavior
 * Uses a combination of lists and forms for managing Model relations.
 *
 * @package october\backend
 * @author Alexey Bobkov, Samuel Georges
 */
class RelationController extends ControllerBehavior
{
    use \Backend\Traits\FormModelSaver;

    /**
     * @var const Postback parameter for the active relationship field.
     */
    const PARAM_FIELD = '_relation_field';

    /**
     * @var const Postback parameter for the active management mode.
     */
    const PARAM_MODE = '_relation_mode';

    /**
     * @var Backend\Classes\WidgetBase Reference to the search widget object.
     */
    protected $searchWidget;

    /**
     * @var Backend\Classes\WidgetBase Reference to the toolbar widget object.
     */
    protected $toolbarWidget;

    /**
     * @var Backend\Classes\WidgetBase Reference to the widget used for viewing (list or form).
     */
    protected $viewWidget;

    /**
     * @var Backend\Classes\WidgetBase Reference to the widget used for relation management.
     */
    protected $manageWidget;

    /**
     * @var Backend\Classes\WidgetBase Reference to widget for relations with pivot data.
     */
    protected $pivotWidget;

    /**
     * {@inheritDoc}
     */
    protected $requiredProperties = ['relationConfig'];

    /**
     * @var array Properties that must exist for each relationship definition.
     */
    protected $requiredRelationProperties = ['label'];

    /**
     * @var array Configuration values that must exist when applying the primary config file.
     */
    protected $requiredConfig = [];

    /**
     * @var array Original configuration values
     */
    protected $originalConfig;

    /**
     * @var bool Has the behavior been initialized.
     */
    protected $initialized = false;

    /**
     * @var string Relationship type
     */
    public $relationType;

    /**
     * @var string Relationship name
     */
    public $relationName;

    /**
     * @var Model Relationship model
     */
    public $relationModel;

    /**
     * @var Model Relationship object
     */
    public $relationObject;

    /**
     * @var Model The parent model of the relationship.
     */
    protected $model;

    /**
     * @var Model The relationship field as defined in the configuration.
     */
    protected $field;

    /**
     * @var string A unique alias to pass to widgets.
     */
    protected $alias;

    /**
     * @var array The set of buttons to display in view mode.
     */
    protected $toolbarButtons;

    /**
     * @var Model Reference to the model used for viewing (form only).
     */
    protected $viewModel;

    /**
     * @var string Relation has many (multi) or has one (single).
     */
    protected $viewMode;

    /**
     * @var string Management of relation as list, form, or pivot.
     */
    protected $manageMode;

    /**
     * @var string Force a certain view mode.
     */
    protected $forceViewMode;

    /**
     * @var string Force a certain manage mode.
     */
    protected $forceManageMode;

    /**
     * @var string The target that triggered an AJAX event (button, list)
     */
    protected $eventTarget;

    /**
     * @var int Primary id of an existing relation record.
     */
    protected $manageId;

    /**
     * @var string Active session key, used for deferred bindings.
     */
    public $sessionKey;

    /**
     * @var bool Disables the ability to add, update, delete or create relations.
     */
    public $readOnly = false;

    /**
     * @var bool Defers all binding actions using a session key when it is available.
     */
    public $deferredBinding = false;

    /**
     * Behavior constructor
     * @param Backend\Classes\Controller $controller
     * @return void
     */
    public function __construct($controller)
    {
        parent::__construct($controller);

        $this->addJs('js/october.relation.js', 'core');
        $this->addCss('css/relation.css', 'core');

        /*
         * Build configuration
         */
        $this->config = $this->originalConfig = $this->makeConfig($controller->relationConfig, $this->requiredConfig);
    }

    /**
     * Prepare the widgets used by this behavior
     * @param Model $model
     * @param string $field
     * @return void
     */
    public function initRelation($model, $field = null)
    {
        if ($field == null) {
            $field = post(self::PARAM_FIELD);
        }

        $this->config = $this->originalConfig;
        $this->model = $model;
        $this->field = $field;

        if ($field == null) {
            return;
        }

        if (!$this->model) {
            throw new ApplicationException(Lang::get(
                'backend::lang.relation.missing_model',
                ['class'=>get_class($this->controller)]
            ));
        }

        if (!$this->model instanceof Model) {
            throw new ApplicationException(Lang::get(
                'backend::lang.model.invalid_class',
                ['model'=>get_class($this->model), 'class'=>get_class($this->controller)]
            ));
        }

        if (!$this->getConfig($field)) {
            throw new ApplicationException(Lang::get('backend::lang.relation.missing_definition', compact('field')));
        }

        $this->alias = camel_case('relation ' . $field);
        $this->config = $this->makeConfig($this->getConfig($field), $this->requiredRelationProperties);

        /*
         * Relationship details
         */
        $this->relationName = $field;
        $this->relationType = $this->model->getRelationType($field);
        $this->relationObject = $this->model->{$field}();
        $this->relationModel = $this->relationObject->getRelated();

        $this->readOnly = $this->getConfig('readOnly');
        $this->deferredBinding = $this->getConfig('deferredBinding') || !$this->model->exists;
        $this->toolbarButtons = $this->evalToolbarButtons();
        $this->viewMode = $this->evalViewMode();
        $this->manageMode = $this->evalManageMode();
        $this->manageId = post('manage_id');

        /*
         * Toolbar widget
         */
        if ($this->toolbarWidget = $this->makeToolbarWidget()) {
            $this->toolbarWidget->bindToController();
        }

        /*
         * View widget
         */
        if ($this->viewWidget = $this->makeViewWidget()) {
            $this->viewWidget->bindToController();
        }

        /*
         * Manage widget
         */
        if ($this->manageWidget = $this->makeManageWidget()) {
            $this->manageWidget->bindToController();
        }

        /*
         * Pivot widget
         */
        if ($this->manageMode == 'pivot') {
            if ($this->pivotWidget = $this->makePivotWidget()) {
                $this->pivotWidget->bindToController();
            }
        }
    }

    /**
     * Renders the relationship manager.
     * @param string $field The relationship field.
     * @param array $options
     * @return string Rendered HTML for the relationship manager.
     */
    public function relationRender($field, $options = [])
    {
        $field = $this->validateField($field);

        if (is_string($options)) {
            $options = ['sessionKey' => $options];
        }

        $this->prepareVars();

        /*
         * Session key
         */
        if (isset($options['sessionKey'])) {
            $this->sessionKey = $options['sessionKey'];
        }

        /*
         * Determine the partial to use based on the supplied section option
         */
        $section = (isset($options['section'])) ? $options['section'] : null;
        switch (strtolower($section)) {
            case 'toolbar':
                return $this->toolbarWidget ? $this->toolbarWidget->render() : null;

            case 'view':
                return $this->relationMakePartial('view');

            default:
                return $this->relationMakePartial('container');
        }
    }

    /**
     * Refreshes the relation container only, useful for returning in custom AJAX requests.
     * @param  string $field Relation definition.
     * @return array The relation element selector as the key, and the relation view contents are the value.
     */
    public function relationRefresh($field = null)
    {
        $field = $this->validateField($field);

        $result = ['#'.$this->relationGetId('view') => $this->relationRenderView($field)];
        if ($toolbar = $this->relationRenderToolbar($field)) {
            $result['#'.$this->relationGetId('toolbar')] = $toolbar;
        }

        if ($eventResult = $this->controller->relationExtendRefreshResults($field)) {
            $result = $eventResult + $result;
        }

        return $result;
    }

    /**
     * Renders the toolbar only.
     * @param string $field The relationship field.
     * @return string Rendered HTML for the toolbar.
     */
    public function relationRenderToolbar($field = null)
    {
        return $this->relationRender($field, ['section' => 'toolbar']);
    }

    /**
     * Renders the view only.
     * @param string $field The relationship field.
     * @return string Rendered HTML for the view.
     */
    public function relationRenderView($field = null)
    {
        return $this->relationRender($field, ['section' => 'view']);
    }

    /**
     * Validates the supplied field and initializes the relation manager.
     * @param string $field The relationship field.
     * @return string The active field name.
     */
    protected function validateField($field = null)
    {
        $field = $field ?: post(self::PARAM_FIELD);

        if ($field && $field != $this->field) {
            $this->initRelation($this->model, $field);
        }

        if (!$field && !$this->field) {
            throw new ApplicationException(Lang::get('backend::lang.relation.missing_definition', compact('field')));
        }

        return $field ?: $this->field;
    }

    /**
     * Prepares the view data.
     * @return void
     */
    public function prepareVars()
    {
        $this->vars['relationManageId'] = $this->manageId;
        $this->vars['relationLabel'] = $this->config->label ?: $this->field;
        $this->vars['relationField'] = $this->field;
        $this->vars['relationType'] = $this->relationType;
        $this->vars['relationSearchWidget'] = $this->searchWidget;
        $this->vars['relationToolbarWidget'] = $this->toolbarWidget;
        $this->vars['relationManageMode'] = $this->manageMode;
        $this->vars['relationManageWidget'] = $this->manageWidget;
        $this->vars['relationToolbarButtons'] = $this->toolbarButtons;
        $this->vars['relationViewMode'] = $this->viewMode;
        $this->vars['relationViewWidget'] = $this->viewWidget;
        $this->vars['relationViewModel'] = $this->viewModel;
        $this->vars['relationPivotWidget'] = $this->pivotWidget;
        $this->vars['relationSessionKey'] = $this->relationGetSessionKey();
    }

    /**
     * The controller action is responsible for supplying the parent model
     * so it's action must be fired. Additionally, each AJAX request must
     * supply the relation's field name (_relation_field).
     */
    protected function beforeAjax()
    {
        if ($this->initialized) {
            return;
        }

        $this->controller->pageAction();
        $this->validateField();
        $this->prepareVars();
        $this->initialized = true;
    }

    /**
     * Controller accessor for making partials within this behavior.
     * @param string $partial
     * @param array $params
     * @return string Partial contents
     */
    public function relationMakePartial($partial, $params = [])
    {
        $contents = $this->controller->makePartial('relation_'.$partial, $params + $this->vars, false);
        if (!$contents) {
            $contents = $this->makePartial($partial, $params);
        }

        return $contents;
    }

    /**
     * Returns a unique ID for this relation and field combination.
     * @param string $suffix A suffix to use with the identifier.
     * @return string
     */
    public function relationGetId($suffix = null)
    {
        $id = class_basename($this);
        if ($this->field) {
            $id .= '-' . $this->field;
        }

        if ($suffix !== null) {
            $id .= '-' . $suffix;
        }

        return $this->controller->getId($id);
    }

    /**
     * Returns the existing record IDs for the relation.
     */
    protected function findExistingRelationIds($checkIds = null)
    {
        $foreignKeyName = $this->relationModel->getQualifiedKeyName();

        $results = $this->relationObject
            ->getBaseQuery()
            ->select($foreignKeyName);

        if ($checkIds !== null && is_array($checkIds) && count($checkIds)) {
            $results = $results->whereIn($foreignKeyName, $checkIds);
        }

        return $results->lists($foreignKeyName);
    }

    //
    // Overrides
    //

    /**
     * Controller override: Extend the query used for populating the list
     * after the default query is processed.
     * @param October\Rain\Database\Builder $query
     * @param string $field
     */
    public function relationExtendQuery($query, $field)
    {
    }

    public function relationExtendRefreshResults($field)
    {
    }

    //
    // AJAX (Buttons)
    //

    public function onRelationButtonAdd()
    {
        $this->eventTarget = 'button-add';
        return $this->onRelationManageForm();
    }

    public function onRelationButtonCreate()
    {
        $this->eventTarget = 'button-create';
        return $this->onRelationManageForm();
    }

    public function onRelationButtonDelete()
    {
        return $this->onRelationManageDelete();
    }

    public function onRelationButtonLink()
    {
        $this->eventTarget = 'button-link';
        return $this->onRelationManageForm();
    }

    public function onRelationButtonUnlink()
    {
        return $this->onRelationManageRemove();
    }

    public function onRelationButtonRemove()
    {
        return $this->onRelationManageRemove();
    }

    public function onRelationButtonUpdate()
    {
        $this->eventTarget = 'button-update';
        return $this->onRelationManageForm();
    }

    //
    // AJAX (List events)
    //

    public function onRelationClickManageList()
    {
        return $this->onRelationManageAdd();
    }

    public function onRelationClickManageListPivot()
    {
        return $this->onRelationManagePivotForm();
    }

    public function onRelationClickViewList()
    {
        $this->eventTarget = 'list';
        return $this->onRelationManageForm();
    }

    //
    // AJAX
    //

    public function onRelationManageForm()
    {
        $this->beforeAjax();

        if ($this->manageMode == 'pivot' && $this->manageId) {
            return $this->onRelationManagePivotForm();
        }

        // The form should not share its session key with the parent
        $this->vars['newSessionKey'] = str_random(40);

        $view = 'manage_' . $this->manageMode;
        return $this->relationMakePartial($view);
    }

    /**
     * Create a new related model
     */
    public function onRelationManageCreate()
    {
        $this->forceManageMode = 'form';
        $this->beforeAjax();
        $saveData = $this->manageWidget->getSaveData();

        if ($this->viewMode == 'multi') {
            $sessionKey = $this->deferredBinding ? $this->relationGetSessionKey(true) : null;

            if ($this->relationType == 'hasMany') {
                $newModel = $this->relationObject->create($saveData, $sessionKey);
            }
            elseif ($this->relationType == 'belongsToMany') {
                $newModel = $this->relationObject->create($saveData, [], $sessionKey);
            }

            $newModel->commitDeferred($this->manageWidget->getSessionKey());
        }
        elseif ($this->viewMode == 'single') {
            $newModel = $this->viewModel;
            $this->viewWidget->setFormValues($saveData);

            if ($this->relationType == 'belongsTo') {
                $newModel->save();
                $this->relationObject->associate($newModel);
                $this->relationObject->getParent()->save();
            }
            elseif ($this->relationType == 'hasOne') {
                $this->relationObject->add($newModel);
            }
        }

        return $this->relationRefresh();
    }

    /**
     * Updated an existing related model's fields
     */
    public function onRelationManageUpdate()
    {
        $this->forceManageMode = 'form';
        $this->beforeAjax();
        $saveData = $this->manageWidget->getSaveData();

        if ($this->viewMode == 'multi') {
            $model = $this->relationObject->find($this->manageId);
            $model->save($saveData, $this->manageWidget->getSessionKey());
        }
        elseif ($this->viewMode == 'single') {
            $this->viewWidget->setFormValues($saveData);
            $this->viewModel->save();
        }

        return ['#'.$this->relationGetId('view') => $this->relationRenderView()];
    }

    /**
     * Delete an existing related model completely
     */
    public function onRelationManageDelete()
    {
        $this->beforeAjax();

        /*
         * Multiple (has many, belongs to many)
         */
        if ($this->viewMode == 'multi') {
            if (($checkedIds = post('checked')) && is_array($checkedIds)) {
                $relatedModel = $this->relationObject->getRelated();
                 foreach ($checkedIds as $relationId) {
                    if (!$obj = $relatedModel->find($relationId)) {
                        continue;
                    }

                    $obj->delete();
                }
            }
        }
        /*
         * Single (belongs to, has one)
         */
        elseif ($this->viewMode == 'single') {
            $relatedModel = $this->viewModel;
            if ($relatedModel->exists) {
                $relatedModel->delete();
            }

            $this->viewWidget->setFormValues([]);
            $this->viewModel = $this->relationModel;
        }

        return $this->relationRefresh();
    }

    /**
     * Add an existing related model to the primary model
     */
    public function onRelationManageAdd()
    {
        $this->beforeAjax();

        $recordId = post('record_id');

        /*
         * Add
         */
        if ($this->viewMode == 'multi') {

            $checkedIds = $recordId ? [$recordId] : post('checked');

            if (is_array($checkedIds)) {
                /*
                 * Remove existing relations from the array
                 */
                $existingIds = $this->findExistingRelationIds($checkedIds);
                $checkedIds = array_diff($checkedIds, $existingIds);
                $foreignKeyName = $this->relationModel->getKeyName();

                $models = $this->relationModel->whereIn($foreignKeyName, $checkedIds)->get();
                foreach ($models as $model) {

                    $sessionKey = $this->deferredBinding
                        ? $this->relationGetSessionKey()
                        : null;

                    $this->relationObject->add($model, $sessionKey);
                }
            }

        }
        /*
         * Link
         */
        elseif ($this->viewMode == 'single') {
            if ($recordId && ($model = $this->relationModel->find($recordId))) {

                if ($this->relationType == 'belongsTo') {
                    $this->relationObject->associate($model);
                    $this->relationObject->getParent()->save();
                }
                elseif ($this->relationType == 'hasOne') {
                    $this->relationObject->add($model);
                }
                $this->viewWidget->setFormValues($model->attributes);

            }
        }

        return $this->relationRefresh();
    }

    /**
     * Remove an existing related model from the primary model
     */
    public function onRelationManageRemove()
    {
        $this->beforeAjax();

        $recordId = post('record_id');

        /*
         * Remove
         */
        if ($this->viewMode == 'multi') {

            $checkedIds = $recordId ? [$recordId] : post('checked');

            if (is_array($checkedIds)) {

                if ($this->relationType == 'belongsToMany') {
                    $this->relationObject->detach($checkedIds);
                }
                elseif ($this->relationType == 'hasMany') {
                    $relatedModel = $this->relationObject->getRelated();
                    foreach ($checkedIds as $relationId) {
                        if ($obj = $relatedModel->find($relationId)) {
                            $this->relationObject->remove($obj);
                        }
                    }
                }

            }
        }
        /*
         * Unlink
         */
        elseif ($this->viewMode == 'single') {
            if ($this->relationType == 'belongsTo') {
                $this->relationObject->dissociate();
                $this->relationObject->getParent()->save();
            }
            elseif ($this->relationType == 'hasOne') {
                if ($obj = $this->relationModel->find($recordId)) {
                    $this->relationObject->remove($obj);
                }
                elseif ($this->viewModel->exists) {
                    $this->relationObject->remove($this->viewModel);
                }
            }

            $this->viewWidget->setFormValues([]);
        }

        return $this->relationRefresh();
    }

    public function onRelationManagePivotForm()
    {
        $this->beforeAjax();

        $this->vars['foreignId'] = post('foreign_id');
        return $this->relationMakePartial('pivot_form');
    }

    public function onRelationManagePivotCreate()
    {
        $this->beforeAjax();

        $foreignId = post('foreign_id');
        $foreignModel = $this->relationModel->find($foreignId);
        $saveData = $this->pivotWidget->getSaveData();

        /*
         * Check for existing relation
         */
        $foreignKeyName = $this->relationModel->getQualifiedKeyName();
        $existing = $this->relationObject->where($foreignKeyName, $foreignId)->count();

        if (!$existing) {
            $this->relationObject->add($foreignModel, null, $saveData);
        }

        return ['#'.$this->relationGetId('view') => $this->relationRenderView()];
    }

    public function onRelationManagePivotUpdate()
    {
        $this->beforeAjax();

        $foreignKeyName = $this->relationModel->getQualifiedKeyName();
        $hydratedModel = $this->relationObject->where($foreignKeyName, $this->manageId)->first();
        $saveData = $this->pivotWidget->getSaveData();

        $modelsToSave = $this->prepareModelsToSave($hydratedModel, $saveData);
        foreach ($modelsToSave as $modelToSave) {
            $modelToSave->save();
        }

        return ['#'.$this->relationGetId('view') => $this->relationRenderView()];
    }

    //
    // Widgets
    //

    protected function makeSearchWidget()
    {
        $config = $this->makeConfig();
        $config->alias = $this->alias . 'ManageSearch';
        $config->growable = false;
        $config->prompt = 'backend::lang.list.search_prompt';
        $widget = $this->makeWidget('Backend\Widgets\Search', $config);
        $widget->cssClasses[] = 'recordfinder-search';
        return $widget;
    }

    protected function makeToolbarWidget()
    {
        $defaultConfig = [];

        /*
         * Add buttons to toolbar
         */
        $defaultButtons = null;

        if (!$this->readOnly) {
            $defaultButtons = '~/modules/backend/behaviors/relationcontroller/partials/_toolbar.htm';
        }

        $defaultConfig['buttons'] = $this->getConfig('view[toolbarPartial]', $defaultButtons);

        /*
         * Make config
         */
        $toolbarConfig = $this->makeConfig($this->getConfig('toolbar', $defaultConfig));
        $toolbarConfig->alias = $this->alias . 'Toolbar';

        /*
         * Add search to toolbar
         */
        $useSearch = $this->viewMode == 'multi' && $this->getConfig('view[showSearch]');

        if ($useSearch) {
            $toolbarConfig->search = [
                'prompt' => 'backend::lang.list.search_prompt'
            ];
        }

        /*
         * No buttons, no search should mean no toolbar
         */
        if (empty($toolbarConfig->search) && empty($toolbarConfig->buttons))
            return;

        $toolbarWidget = $this->makeWidget('Backend\Widgets\Toolbar', $toolbarConfig);
        $toolbarWidget->cssClasses[] = 'list-header';

        return $toolbarWidget;
    }

    protected function makeViewWidget()
    {
        /*
         * Multiple (has many, belongs to many)
         */
        if ($this->viewMode == 'multi') {
            $config = $this->makeConfigForMode('view', 'list');
            $config->model = $this->relationModel;
            $config->alias = $this->alias . 'ViewList';
            $config->showSorting = $this->getConfig('view[showSorting]', true);
            $config->defaultSort = $this->getConfig('view[defaultSort]');
            $config->recordsPerPage = $this->getConfig('view[recordsPerPage]');
            $config->showCheckboxes = $this->getConfig('view[showCheckboxes]', !$this->readOnly);

            $defaultOnClick = sprintf(
                "$.oc.relationBehavior.clickViewListRecord(':id', '%s', '%s')",
                $this->field,
                $this->relationGetSessionKey()
            );

            $config->recordOnClick = $this->getConfig('view[recordOnClick]', $defaultOnClick);
            $config->recordUrl = $this->getConfig('view[recordUrl]', null);

            if ($emptyMessage = $this->getConfig('emptyMessage')) {
                $config->noRecordsMessage = $emptyMessage;
            }

            /*
             * Constrain the query by the relationship and deferred items
             */
            $widget = $this->makeWidget('Backend\Widgets\Lists', $config);
            $widget->bindEvent('list.extendQuery', function ($query) {
                $this->controller->relationExtendQuery($query, $this->field);

                $this->relationObject->setQuery($query);
                if ($sessionKey = $this->relationGetSessionKey()) {
                    $this->relationObject->withDeferred($sessionKey);
                }
                elseif ($this->model->exists) {
                    $this->relationObject->addConstraints();
                }

                /*
                 * Allows pivot data to enter the fray
                 */
                if ($this->relationType == 'belongsToMany') {
                    $this->relationObject->setQuery($query->getQuery());
                    return $this->relationObject;
                }
            });

            /*
             * Constrain the list by the search widget, if available
             */
            if ($this->toolbarWidget && $this->getConfig('view[showSearch]')) {
                if ($searchWidget = $this->toolbarWidget->getSearchWidget()) {
                    $searchWidget->bindEvent('search.submit', function () use ($widget, $searchWidget) {
                        $widget->setSearchTerm($searchWidget->getActiveTerm());
                        return $widget->onRefresh();
                    });

                    $searchWidget->setActiveTerm(null);
                }
            }
        }
        /*
         * Single (belongs to, has one)
         */
        elseif ($this->viewMode == 'single') {
            $query = $this->relationObject;
            $this->controller->relationExtendQuery($query, $this->field);
            $this->viewModel = $query->getResults() ?: $this->relationModel;

            $config = $this->makeConfigForMode('view', 'form');
            $config->model = $this->viewModel;
            $config->arrayName = class_basename($this->relationModel);
            $config->context = 'relation';
            $config->alias = $this->alias . 'ViewForm';

            $widget = $this->makeWidget('Backend\Widgets\Form', $config);
            $widget->previewMode = true;
        }

        return $widget;
    }

    protected function makeManageWidget()
    {
        $widget = null;
        /*
         * Pivot
         */
        if ($this->manageMode == 'pivot' && isset($this->config->pivot)) {
            $config = $this->makeConfigForMode('manage', 'list');
            $config->model = $this->relationModel;
            $config->alias = $this->alias . 'ManagePivotList';
            $config->showSetup = false;
            $config->showSorting = $this->getConfig('manage[showSorting]', false);
            $config->defaultSort = $this->getConfig('manage[defaultSort]');
            $config->recordsPerPage = $this->getConfig('manage[recordsPerPage]');
            $config->recordOnClick = sprintf(
                "$.oc.relationBehavior.clickManagePivotListRecord(:id, '%s', '%s')",
                $this->field,
                $this->relationGetSessionKey()
            );

            $widget = $this->makeWidget('Backend\Widgets\Lists', $config);

            /*
             * Link the Search Widget to the List Widget
             */
            if ($this->getConfig('pivot[showSearch]')) {
                $this->searchWidget = $this->makeSearchWidget();
                $this->searchWidget->bindToController();
                $this->searchWidget->bindEvent('search.submit', function () use ($widget) {
                    $widget->setSearchTerm($this->searchWidget->getActiveTerm());
                    return $widget->onRefresh();
                });

                $this->searchWidget->setActiveTerm(null);
            }
        }
        /*
         * List
         */
        elseif ($this->manageMode == 'list' && isset($this->config->list)) {
            $config = $this->makeConfigForMode('manage', 'list');
            $config->model = $this->relationModel;
            $config->alias = $this->alias . 'ManageList';
            $config->showSetup = false;
            $config->showCheckboxes = true;
            $config->showSorting = $this->getConfig('manage[showSorting]', true);
            $config->defaultSort = $this->getConfig('manage[defaultSort]');
            $config->recordsPerPage = $this->getConfig('manage[recordsPerPage]');

            if ($this->viewMode == 'single') {
                $config->showCheckboxes = false;
                $config->recordOnClick = sprintf(
                    "$.oc.relationBehavior.clickManageListRecord(:id, '%s', '%s')",
                    $this->field,
                    $this->relationGetSessionKey()
                );
            }

            $widget = $this->makeWidget('Backend\Widgets\Lists', $config);

            /*
             * Link the Search Widget to the List Widget
             */
            if ($this->getConfig('manage[showSearch]')) {
                $this->searchWidget = $this->makeSearchWidget();
                $this->searchWidget->bindToController();
                $this->searchWidget->bindEvent('search.submit', function () use ($widget) {
                    $widget->setSearchTerm($this->searchWidget->getActiveTerm());
                    return $widget->onRefresh();
                });

                $this->searchWidget->setActiveTerm(null);
            }
        }
        /*
         * Form
         */
        elseif ($this->manageMode == 'form' && isset($this->config->form)) {

            /*
             * Determine supplied form context
             */
            $manageConfig = isset($this->config->manage) ? $this->config->manage : [];

            if ($context = array_get($manageConfig, 'context')) {
                if (is_array($context)) {
                    $context = $this->manageId
                        ? array_get($context, 'update')
                        : array_get($context, 'create');
                }
            }

            $config = $this->makeConfigForMode('manage', 'form');
            $config->model = $this->relationModel;
            $config->arrayName = class_basename($this->relationModel);
            $config->context = $context ?: 'relation';
            $config->alias = $this->alias . 'ManageForm';

            /*
             * Existing record
             */
            if ($this->manageId) {
                $config->model = $config->model->find($this->manageId);
                if (!$config->model) {
                    throw new ApplicationException(Lang::get('backend::lang.model.not_found', [
                        'class' => get_class($config->model), 'id' => $this->manageId
                    ]));
                }
            }

            $widget = $this->makeWidget('Backend\Widgets\Form', $config);
        }

        if (!$widget) {
            return null;
        }

        /*
         * Exclude existing relationships
         */
        if ($this->manageMode == 'pivot' || $this->manageMode == 'list') {
            $widget->bindEvent('list.extendQuery', function ($query) {
                $this->controller->relationExtendQuery($query, $this->field);

                /*
                 * Where not in the current list of related records
                 */
                $existingIds = $this->findExistingRelationIds();
                if (count($existingIds)) {
                    $query->whereNotIn($this->relationModel->getQualifiedKeyName(), $existingIds);
                }

            });
        }

        return $widget;
    }

    protected function makePivotWidget()
    {
        $config = $this->makeConfigForMode('pivot', 'form');
        $config->model = $this->relationModel;
        $config->arrayName = class_basename($this->relationModel);
        $config->context = 'relation';
        $config->alias = $this->alias . 'ManagePivotForm';

        /*
         * Existing record
         */
        if ($this->manageId) {
            $foreignKeyName = $this->relationModel->getQualifiedKeyName();
            $hydratedModel = $this->relationObject->where($foreignKeyName, $this->manageId)->first();

            $config->model = $hydratedModel;
            if (!$config->model) {
                throw new ApplicationException(Lang::get('backend::lang.model.not_found', [
                    'class' => get_class($config->model), 'id' => $this->manageId
                ]));
            }
        }

        $widget = $this->makeWidget('Backend\Widgets\Form', $config);
        return $widget;
    }

    /**
     * Returns the active session key.
     */
    public function relationGetSessionKey($force = false)
    {
        if ($this->sessionKey && !$force) {
            return $this->sessionKey;
        }

        if (post('_relation_session_key')) {
            return $this->sessionKey = post('_relation_session_key');
        }

        if (post('_session_key')) {
            return $this->sessionKey = post('_session_key');
        }

        return $this->sessionKey = FormHelper::getSessionKey();
    }

    //
    // Helpers
    //


    /**
     * Determine the default buttons based on the model relationship type.
     * @return string
     */
    protected function evalToolbarButtons()
    {
        if ($buttons = $this->getConfig('view[toolbarButtons]')) {
            return is_array($buttons)
                ? $buttons
                : array_map('trim', explode('|', $buttons));
        }

        switch ($this->relationType) {
            case 'hasMany':
            case 'belongsToMany':
                return ['create', 'add', 'delete', 'remove'];

            case 'hasOne':
            case 'belongsTo':
                return ['create', 'update', 'link', 'delete', 'unlink'];
        }
    }

    /**
     * Determine the view mode based on the model relationship type.
     * @return string
     */
    protected function evalViewMode()
    {
        if ($this->forceViewMode) {
            return $this->forceViewMode;
        }

        switch ($this->relationType) {
            case 'hasMany':
            case 'belongsToMany':
                return 'multi';

            case 'hasOne':
            case 'belongsTo':
                return 'single';
        }
    }

    /**
     * Determine the management mode based on the relation type and settings.
     * @return string
     */
    protected function evalManageMode()
    {
        if ($mode = post(self::PARAM_MODE)) {
            return $mode;
        }

        if ($this->forceManageMode) {
            return $this->forceManageMode;
        }

        switch ($this->eventTarget) {
            case 'button-create':
            case 'button-update':
                return 'form';

            case 'button-link':
                return 'list';
        }

        switch ($this->relationType) {
            case 'belongsTo':
                return 'list';

            case 'belongsToMany':
                if (isset($this->config->pivot)) return 'pivot';
                elseif ($this->eventTarget == 'list') return 'form';
                else return 'list';

            case 'hasOne':
            case 'hasMany':
                if ($this->eventTarget == 'button-add') return 'list';
                else return 'form';
        }
    }

    /**
     * Returns the configuration for a mode (view, manage, pivot) for an
     * expected type (list, form). Uses fallback configuration.
     */
    protected function makeConfigForMode($mode = 'view', $type = 'list')
    {
        $config = null;

        /*
         * Look for $this->config->view['list']
         */
        if (
            isset($this->config->{$mode}) &&
            array_key_exists($type, $this->config->{$mode})
        ) {
            $config = $this->config->{$mode}[$type];
        }
        /*
         * Look for $this->config->list
         */
        elseif (isset($this->config->{$type})) {
            $config = $this->config->{$type};
        }

        /*
         * Apply substitutes:
         *
         * - view.list => manage.list
         */
        if (!$config) {

            if ($mode == 'manage' && $type == 'list') {
                return $this->makeConfigForMode('view', $type);
            }

            throw new ApplicationException('Missing configuration for '.$mode.'.'.$type.' in RelationController definition '.$this->field);
        }

        return $this->makeConfig($config);
    }

}