<?php
// This file is part of Moodle - http://moodle.org/
//
// Moodle is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// Moodle is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with Moodle.  If not, see <http://www.gnu.org/licenses/>.

/**
 * Tests for the {@link core_question\bank\random_question_loader} class.
 *
 * @package   core_question
 * @copyright 2015 The Open University
 * @license   http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
 */

defined('MOODLE_INTERNAL') || die();


/**
 * Tests for the {@link core_question\bank\random_question_loader} class.
 *
 * @copyright  2015 The Open University
 * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
 */
class random_question_loader_testcase extends advanced_testcase {

    public function test_empty_category_gives_null() {
        $this->resetAfterTest();
        $generator = $this->getDataGenerator()->get_plugin_generator('core_question');

        $cat = $generator->create_question_category();
        $loader = new \core_question\bank\random_question_loader(new qubaid_list(array()));

        $this->assertNull($loader->get_next_question_id($cat->id, 0));
        $this->assertNull($loader->get_next_question_id($cat->id, 1));
    }

    public function test_unknown_category_behaves_like_empty() {
        // It is up the caller to make sure the category id is valid.
        $loader = new \core_question\bank\random_question_loader(new qubaid_list(array()));
        $this->assertNull($loader->get_next_question_id(-1, 1));
    }

    public function test_descriptions_not_returned() {
        $this->resetAfterTest();
        $generator = $this->getDataGenerator()->get_plugin_generator('core_question');

        $cat = $generator->create_question_category();
        $info = $generator->create_question('description', null, array('category' => $cat->id));
        $loader = new \core_question\bank\random_question_loader(new qubaid_list(array()));

        $this->assertNull($loader->get_next_question_id($cat->id, 0));
    }

    public function test_hidden_questions_not_returned() {
        global $DB;
        $this->resetAfterTest();
        $generator = $this->getDataGenerator()->get_plugin_generator('core_question');

        $cat = $generator->create_question_category();
        $question1 = $generator->create_question('shortanswer', null, array('category' => $cat->id));
        $DB->set_field('question', 'hidden', 1, array('id' => $question1->id));
        $loader = new \core_question\bank\random_question_loader(new qubaid_list(array()));

        $this->assertNull($loader->get_next_question_id($cat->id, 0));
    }

    public function test_cloze_subquestions_not_returned() {
        $this->resetAfterTest();
        $generator = $this->getDataGenerator()->get_plugin_generator('core_question');

        $cat = $generator->create_question_category();
        $question1 = $generator->create_question('multianswer', null, array('category' => $cat->id));
        $loader = new \core_question\bank\random_question_loader(new qubaid_list(array()));

        $this->assertEquals($question1->id, $loader->get_next_question_id($cat->id, 0));
        $this->assertNull($loader->get_next_question_id($cat->id, 0));
    }

    public function test_random_questions_not_returned() {
        $this->resetAfterTest();
        $this->setAdminUser();
        $generator = $this->getDataGenerator()->get_plugin_generator('core_question');

        $cat = $generator->create_question_category();
        $course = $this->getDataGenerator()->create_course();
        $quiz = $this->getDataGenerator()->create_module('quiz', array('course' => $course));
        quiz_add_random_questions($quiz, 1, $cat->id, 1, false);
        $loader = new \core_question\bank\random_question_loader(new qubaid_list(array()));

        $this->assertNull($loader->get_next_question_id($cat->id, 0));
    }

    public function test_one_question_category_returns_that_q_then_null() {
        $this->resetAfterTest();
        $generator = $this->getDataGenerator()->get_plugin_generator('core_question');

        $cat = $generator->create_question_category();
        $question1 = $generator->create_question('shortanswer', null, array('category' => $cat->id));
        $loader = new \core_question\bank\random_question_loader(new qubaid_list(array()));

        $this->assertEquals($question1->id, $loader->get_next_question_id($cat->id, 1));
        $this->assertNull($loader->get_next_question_id($cat->id, 0));
    }

    public function test_two_question_category_returns_both_then_null() {
        $this->resetAfterTest();
        $generator = $this->getDataGenerator()->get_plugin_generator('core_question');

        $cat = $generator->create_question_category();
        $question1 = $generator->create_question('shortanswer', null, array('category' => $cat->id));
        $question2 = $generator->create_question('shortanswer', null, array('category' => $cat->id));
        $loader = new \core_question\bank\random_question_loader(new qubaid_list(array()));

        $questionids = array();
        $questionids[] = $loader->get_next_question_id($cat->id, 0);
        $questionids[] = $loader->get_next_question_id($cat->id, 0);
        sort($questionids);
        $this->assertEquals(array($question1->id, $question2->id), $questionids);

        $this->assertNull($loader->get_next_question_id($cat->id, 1));
    }

    public function test_nested_categories() {
        $this->resetAfterTest();
        $generator = $this->getDataGenerator()->get_plugin_generator('core_question');

        $cat1 = $generator->create_question_category();
        $cat2 = $generator->create_question_category(array('parent' => $cat1->id));
        $question1 = $generator->create_question('shortanswer', null, array('category' => $cat1->id));
        $question2 = $generator->create_question('shortanswer', null, array('category' => $cat2->id));
        $loader = new \core_question\bank\random_question_loader(new qubaid_list(array()));

        $this->assertEquals($question2->id, $loader->get_next_question_id($cat2->id, 1));
        $this->assertEquals($question1->id, $loader->get_next_question_id($cat1->id, 1));

        $this->assertNull($loader->get_next_question_id($cat1->id, 0));
    }

    public function test_used_question_not_returned_until_later() {
        $this->resetAfterTest();
        $generator = $this->getDataGenerator()->get_plugin_generator('core_question');

        $cat = $generator->create_question_category();
        $question1 = $generator->create_question('shortanswer', null, array('category' => $cat->id));
        $question2 = $generator->create_question('shortanswer', null, array('category' => $cat->id));
        $loader = new \core_question\bank\random_question_loader(new qubaid_list(array()),
                array($question2->id => 2));

        $this->assertEquals($question1->id, $loader->get_next_question_id($cat->id, 0));
        $this->assertNull($loader->get_next_question_id($cat->id, 0));
    }

    public function test_previously_used_question_not_returned_until_later() {
        $this->resetAfterTest();
        $generator = $this->getDataGenerator()->get_plugin_generator('core_question');

        $cat = $generator->create_question_category();
        $question1 = $generator->create_question('shortanswer', null, array('category' => $cat->id));
        $question2 = $generator->create_question('shortanswer', null, array('category' => $cat->id));
        $quba = question_engine::make_questions_usage_by_activity('test', context_system::instance());
        $quba->set_preferred_behaviour('deferredfeedback');
        $question = question_bank::load_question($question2->id);
        $quba->add_question($question);
        $quba->add_question($question);
        $quba->start_all_questions();
        question_engine::save_questions_usage_by_activity($quba);

        $loader = new \core_question\bank\random_question_loader(new qubaid_list(array($quba->get_id())));

        $this->assertEquals($question1->id, $loader->get_next_question_id($cat->id, 0));
        $this->assertEquals($question2->id, $loader->get_next_question_id($cat->id, 0));
        $this->assertNull($loader->get_next_question_id($cat->id, 0));
    }

    public function test_empty_category_does_not_have_question_available() {
        $this->resetAfterTest();
        $generator = $this->getDataGenerator()->get_plugin_generator('core_question');

        $cat = $generator->create_question_category();
        $loader = new \core_question\bank\random_question_loader(new qubaid_list(array()));

        $this->assertFalse($loader->is_question_available($cat->id, 0, 1));
        $this->assertFalse($loader->is_question_available($cat->id, 1, 1));
    }

    public function test_descriptions_not_available() {
        $this->resetAfterTest();
        $generator = $this->getDataGenerator()->get_plugin_generator('core_question');

        $cat = $generator->create_question_category();
        $info = $generator->create_question('description', null, array('category' => $cat->id));
        $loader = new \core_question\bank\random_question_loader(new qubaid_list(array()));

        $this->assertFalse($loader->is_question_available($cat->id, 0, $info->id));
        $this->assertFalse($loader->is_question_available($cat->id, 1, $info->id));
    }

    public function test_existing_question_is_available_but_then_marked_used() {
        $this->resetAfterTest();
        $generator = $this->getDataGenerator()->get_plugin_generator('core_question');

        $cat = $generator->create_question_category();
        $question1 = $generator->create_question('shortanswer', null, array('category' => $cat->id));
        $loader = new \core_question\bank\random_question_loader(new qubaid_list(array()));

        $this->assertTrue($loader->is_question_available($cat->id, 0, $question1->id));
        $this->assertFalse($loader->is_question_available($cat->id, 0, $question1->id));

        $this->assertFalse($loader->is_question_available($cat->id, 0, -1));
    }

    /**
     * Data provider for the get_questions test.
     */
    public function get_questions_test_cases() {
        return [
            'empty category' => [
                'categoryindex' => 'emptycat',
                'includesubcategories' => false,
                'usetagnames' => [],
                'expectedquestionindexes' => []
            ],
            'single category' => [
                'categoryindex' => 'cat1',
                'includesubcategories' => false,
                'usetagnames' => [],
                'expectedquestionindexes' => ['cat1q1', 'cat1q2']
            ],
            'include sub category' => [
                'categoryindex' => 'cat1',
                'includesubcategories' => true,
                'usetagnames' => [],
                'expectedquestionindexes' => ['cat1q1', 'cat1q2', 'subcatq1', 'subcatq2']
            ],
            'single category with tags' => [
                'categoryindex' => 'cat1',
                'includesubcategories' => false,
                'usetagnames' => ['cat1'],
                'expectedquestionindexes' => ['cat1q1']
            ],
            'include sub category with tag on parent' => [
                'categoryindex' => 'cat1',
                'includesubcategories' => true,
                'usetagnames' => ['cat1'],
                'expectedquestionindexes' => ['cat1q1']
            ],
            'include sub category with tag on sub' => [
                'categoryindex' => 'cat1',
                'includesubcategories' => true,
                'usetagnames' => ['subcat'],
                'expectedquestionindexes' => ['subcatq1']
            ],
            'include sub category with same tag on parent and sub' => [
                'categoryindex' => 'cat1',
                'includesubcategories' => true,
                'usetagnames' => ['foo'],
                'expectedquestionindexes' => ['cat1q1', 'subcatq1']
            ],
            'include sub category with tag not matching' => [
                'categoryindex' => 'cat1',
                'includesubcategories' => true,
                'usetagnames' => ['cat1', 'cat2'],
                'expectedquestionindexes' => []
            ]
        ];
    }

    /**
     * Test the get_questions function with various parameter combinations.
     *
     * This function creates a data set as follows:
     *      Category: cat1
     *          Question: cat1q1
     *              Tags: 'cat1', 'foo'
     *          Question: cat1q2
     *      Category: cat2
     *          Question: cat2q1
     *              Tags: 'cat2', 'foo'
     *          Question: cat2q2
     *      Category: subcat
     *          Question: subcatq1
     *              Tags: 'subcat', 'foo'
     *          Question: subcatq2
     *          Parent: cat1
     *      Category: emptycat
     *
     * @dataProvider get_questions_test_cases()
     * @param string $categoryindex The named index for the category to use
     * @param bool $includesubcategories If the search should include subcategories
     * @param string[] $usetagnames The tag names to include in the search
     * @param string[] $expectedquestionindexes The questions expected in the result
     */
    public function test_get_questions_variations(
        $categoryindex,
        $includesubcategories,
        $usetagnames,
        $expectedquestionindexes
    ) {
        $this->resetAfterTest();

        $categories = [];
        $questions = [];
        $tagnames = [
            'cat1',
            'cat2',
            'subcat',
            'foo'
        ];
        $collid = core_tag_collection::get_default();
        $tags = core_tag_tag::create_if_missing($collid, $tagnames);
        $generator = $this->getDataGenerator()->get_plugin_generator('core_question');

        // First category and questions.
        list($category, $categoryquestions) = $this->create_category_and_questions(2, ['cat1', 'foo']);
        $categories['cat1'] = $category;
        $questions['cat1q1'] = $categoryquestions[0];
        $questions['cat1q2'] = $categoryquestions[1];
        // Second category and questions.
        list($category, $categoryquestions) = $this->create_category_and_questions(2, ['cat2', 'foo']);
        $categories['cat2'] = $category;
        $questions['cat2q1'] = $categoryquestions[0];
        $questions['cat2q2'] = $categoryquestions[1];
        // Sub category and questions.
        list($category, $categoryquestions) = $this->create_category_and_questions(2, ['subcat', 'foo'], $categories['cat1']);
        $categories['subcat'] = $category;
        $questions['subcatq1'] = $categoryquestions[0];
        $questions['subcatq2'] = $categoryquestions[1];
        // Empty category.
        list($category, $categoryquestions) = $this->create_category_and_questions(0);
        $categories['emptycat'] = $category;

        // Generate the arguments for the get_questions function.
        $category = $categories[$categoryindex];
        $tagids = array_map(function($tagname) use ($tags) {
            return $tags[$tagname]->id;
        }, $usetagnames);

        $loader = new \core_question\bank\random_question_loader(new qubaid_list([]));
        $result = $loader->get_questions($category->id, $includesubcategories, $tagids);
        // Generate the expected question set.
        $expectedquestions = array_map(function($index) use ($questions) {
            return $questions[$index];
        }, $expectedquestionindexes);

        // Ensure the result matches what was expected.
        $this->assertCount(count($expectedquestions), $result);
        foreach ($expectedquestions as $question) {
            $this->assertEquals($result[$question->id]->id, $question->id);
            $this->assertEquals($result[$question->id]->category, $question->category);
        }
    }

    /**
     * get_questions should allow limiting and offsetting of the result set.
     */
    public function test_get_questions_with_limit_and_offset() {
        $this->resetAfterTest();
        $numberofquestions = 5;
        $includesubcategories = false;
        $tagids = [];
        $limit = 1;
        $offset = 0;
        $loader = new \core_question\bank\random_question_loader(new qubaid_list([]));
        list($category, $questions) = $this->create_category_and_questions($numberofquestions);

        // Sort the questions by id to match the ordering of the get_questions
        // function.
        usort($questions, function($a, $b) {
            $aid = $a->id;
            $bid = $b->id;

            if ($aid == $bid) {
                return 0;
            }
            return $aid < $bid ? -1 : 1;
        });

        for ($i = 0; $i < $numberofquestions; $i++) {
            $result = $loader->get_questions(
                $category->id,
                $includesubcategories,
                $tagids,
                $limit,
                $offset
            );

            $this->assertCount($limit, $result);
            $actual = array_shift($result);
            $expected = $questions[$i];
            $this->assertEquals($expected->id, $actual->id);
            $offset++;
        }
    }

    /**
     * get_questions should allow retrieving questions with only a subset of
     * fields populated.
     */
    public function test_get_questions_with_restricted_fields() {
        $this->resetAfterTest();
        $includesubcategories = false;
        $tagids = [];
        $limit = 10;
        $offset = 0;
        $fields = ['id', 'name'];
        $loader = new \core_question\bank\random_question_loader(new qubaid_list([]));
        list($category, $questions) = $this->create_category_and_questions(1);

        $result = $loader->get_questions(
            $category->id,
            $includesubcategories,
            $tagids,
            $limit,
            $offset,
            $fields
        );

        $expectedquestion = array_shift($questions);
        $actualquestion = array_shift($result);
        $actualfields = get_object_vars($actualquestion);
        $actualfields = array_keys($actualfields);
        sort($actualfields);
        sort($fields);

        $this->assertEquals($fields, $actualfields);
    }

    /**
     * Data provider for the count_questions test.
     */
    public function count_questions_test_cases() {
        return [
            'empty category' => [
                'categoryindex' => 'emptycat',
                'includesubcategories' => false,
                'usetagnames' => [],
                'expectedcount' => 0
            ],
            'single category' => [
                'categoryindex' => 'cat1',
                'includesubcategories' => false,
                'usetagnames' => [],
                'expectedcount' => 2
            ],
            'include sub category' => [
                'categoryindex' => 'cat1',
                'includesubcategories' => true,
                'usetagnames' => [],
                'expectedcount' => 4
            ],
            'single category with tags' => [
                'categoryindex' => 'cat1',
                'includesubcategories' => false,
                'usetagnames' => ['cat1'],
                'expectedcount' => 1
            ],
            'include sub category with tag on parent' => [
                'categoryindex' => 'cat1',
                'includesubcategories' => true,
                'usetagnames' => ['cat1'],
                'expectedcount' => 1
            ],
            'include sub category with tag on sub' => [
                'categoryindex' => 'cat1',
                'includesubcategories' => true,
                'usetagnames' => ['subcat'],
                'expectedcount' => 1
            ],
            'include sub category with same tag on parent and sub' => [
                'categoryindex' => 'cat1',
                'includesubcategories' => true,
                'usetagnames' => ['foo'],
                'expectedcount' => 2
            ],
            'include sub category with tag not matching' => [
                'categoryindex' => 'cat1',
                'includesubcategories' => true,
                'usetagnames' => ['cat1', 'cat2'],
                'expectedcount' => 0
            ]
        ];
    }

    /**
     * Test the count_questions function with various parameter combinations.
     *
     * This function creates a data set as follows:
     *      Category: cat1
     *          Question: cat1q1
     *              Tags: 'cat1', 'foo'
     *          Question: cat1q2
     *      Category: cat2
     *          Question: cat2q1
     *              Tags: 'cat2', 'foo'
     *          Question: cat2q2
     *      Category: subcat
     *          Question: subcatq1
     *              Tags: 'subcat', 'foo'
     *          Question: subcatq2
     *          Parent: cat1
     *      Category: emptycat
     *
     * @dataProvider count_questions_test_cases()
     * @param string $categoryindex The named index for the category to use
     * @param bool $includesubcategories If the search should include subcategories
     * @param string[] $usetagnames The tag names to include in the search
     * @param int $expectedcount The number of questions expected in the result
     */
    public function test_count_questions_variations(
        $categoryindex,
        $includesubcategories,
        $usetagnames,
        $expectedcount
    ) {
        $this->resetAfterTest();

        $categories = [];
        $questions = [];
        $tagnames = [
            'cat1',
            'cat2',
            'subcat',
            'foo'
        ];
        $collid = core_tag_collection::get_default();
        $tags = core_tag_tag::create_if_missing($collid, $tagnames);
        $generator = $this->getDataGenerator()->get_plugin_generator('core_question');

        // First category and questions.
        list($category, $categoryquestions) = $this->create_category_and_questions(2, ['cat1', 'foo']);
        $categories['cat1'] = $category;
        $questions['cat1q1'] = $categoryquestions[0];
        $questions['cat1q2'] = $categoryquestions[1];
        // Second category and questions.
        list($category, $categoryquestions) = $this->create_category_and_questions(2, ['cat2', 'foo']);
        $categories['cat2'] = $category;
        $questions['cat2q1'] = $categoryquestions[0];
        $questions['cat2q2'] = $categoryquestions[1];
        // Sub category and questions.
        list($category, $categoryquestions) = $this->create_category_and_questions(2, ['subcat', 'foo'], $categories['cat1']);
        $categories['subcat'] = $category;
        $questions['subcatq1'] = $categoryquestions[0];
        $questions['subcatq2'] = $categoryquestions[1];
        // Empty category.
        list($category, $categoryquestions) = $this->create_category_and_questions(0);
        $categories['emptycat'] = $category;

        // Generate the arguments for the get_questions function.
        $category = $categories[$categoryindex];
        $tagids = array_map(function($tagname) use ($tags) {
            return $tags[$tagname]->id;
        }, $usetagnames);

        $loader = new \core_question\bank\random_question_loader(new qubaid_list([]));
        $result = $loader->count_questions($category->id, $includesubcategories, $tagids);

        // Ensure the result matches what was expected.
        $this->assertEquals($expectedcount, $result);
    }

    /**
     * Create a question category and create questions in that category. Tag
     * the first question in each category with the given tags.
     *
     * @param int $questioncount How many questions to create.
     * @param string[] $tagnames The list of tags to use.
     * @param stdClass|null $parentcategory The category to set as the parent of the created category.
     * @return array The category and questions.
     */
    protected function create_category_and_questions($questioncount, $tagnames = [], $parentcategory = null) {
        $generator = $this->getDataGenerator()->get_plugin_generator('core_question');

        if ($parentcategory) {
            $catparams = ['parent' => $parentcategory->id];
        } else {
            $catparams = [];
        }

        $category = $generator->create_question_category($catparams);
        $questions = [];

        for ($i = 0; $i < $questioncount; $i++) {
            $questions[] = $generator->create_question('shortanswer', null, ['category' => $category->id]);
        }

        if (!empty($tagnames) && !empty($questions)) {
            $context = context::instance_by_id($category->contextid);
            core_tag_tag::set_item_tags('core_question', 'question', $questions[0]->id, $context, $tagnames);
        }

        return [$category, $questions];
    }
}