<?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/>.

/**
 * Quiz statistics report, table for showing statistics of each question in the quiz.
 *
 * @package   quiz_statistics
 * @copyright 2008 Jamie Pratt
 * @license   http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
 */


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

require_once($CFG->libdir.'/tablelib.php');


/**
 * This table has one row for each question in the quiz, with sub-rows when
 * random questions appear. There are columns for the various statistics.
 *
 * @copyright 2008 Jamie Pratt
 * @license   http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
 */
class quiz_statistics_table extends flexible_table {
    /** @var object the quiz settings. */
    protected $quiz;

    /** @var integer the quiz course_module id. */
    protected $cmid;

    /**
     * Constructor.
     */
    public function __construct() {
        parent::__construct('mod-quiz-report-statistics-report');
    }

    /**
     * Set up the columns and headers and other properties of the table and then
     * call flexible_table::setup() method.
     *
     * @param object $quiz the quiz settings
     * @param int $cmid the quiz course_module id
     * @param moodle_url $reporturl the URL to redisplay this report.
     * @param int $s number of attempts included in the statistics.
     */
    public function statistics_setup($quiz, $cmid, $reporturl, $s) {
        $this->quiz = $quiz;
        $this->cmid = $cmid;

        // Define the table columns.
        $columns = array();
        $headers = array();

        $columns[] = 'number';
        $headers[] = get_string('questionnumber', 'quiz_statistics');

        if (!$this->is_downloading()) {
            $columns[] = 'icon';
            $headers[] = '';
            $columns[] = 'actions';
            $headers[] = '';
        } else {
            $columns[] = 'qtype';
            $headers[] = get_string('questiontype', 'quiz_statistics');
        }

        $columns[] = 'name';
        $headers[] = get_string('questionname', 'quiz');

        $columns[] = 's';
        $headers[] = get_string('attempts', 'quiz_statistics');

        if ($s > 1) {
            $columns[] = 'facility';
            $headers[] = get_string('facility', 'quiz_statistics');

            $columns[] = 'sd';
            $headers[] = get_string('standarddeviationq', 'quiz_statistics');
        }

        $columns[] = 'random_guess_score';
        $headers[] = get_string('random_guess_score', 'quiz_statistics');

        $columns[] = 'intended_weight';
        $headers[] = get_string('intended_weight', 'quiz_statistics');

        $columns[] = 'effective_weight';
        $headers[] = get_string('effective_weight', 'quiz_statistics');

        $columns[] = 'discrimination_index';
        $headers[] = get_string('discrimination_index', 'quiz_statistics');

        $columns[] = 'discriminative_efficiency';
        $headers[] = get_string('discriminative_efficiency', 'quiz_statistics');

        $this->define_columns($columns);
        $this->define_headers($headers);
        $this->sortable(false);

        $this->column_class('s', 'numcol');
        $this->column_class('facility', 'numcol');
        $this->column_class('sd', 'numcol');
        $this->column_class('random_guess_score', 'numcol');
        $this->column_class('intended_weight', 'numcol');
        $this->column_class('effective_weight', 'numcol');
        $this->column_class('discrimination_index', 'numcol');
        $this->column_class('discriminative_efficiency', 'numcol');

        // Set up the table.
        $this->define_baseurl($reporturl->out());

        $this->collapsible(true);

        $this->set_attribute('id', 'questionstatistics');
        $this->set_attribute('class', 'generaltable generalbox boxaligncenter');

        parent::setup();
    }

    /**
     * The question number.
     * @param object $question containst the data to display.
     * @return string contents of this table cell.
     */
    protected function col_number($question) {
        if ($question->_stats->subquestion) {
            return '';
        }

        return $question->number;
    }

    /**
     * The question type icon.
     * @param object $question containst the data to display.
     * @return string contents of this table cell.
     */
    protected function col_icon($question) {
        return print_question_icon($question, true);
    }

    /**
     * Actions that can be performed on the question by this user (e.g. edit or preview).
     * @param object $question containst the data to display.
     * @return string contents of this table cell.
     */
    protected function col_actions($question) {
        return quiz_question_action_icons($this->quiz, $this->cmid, $question, $this->baseurl);
    }

    /**
     * The question type name.
     * @param object $question containst the data to display.
     * @return string contents of this table cell.
     */
    protected function col_qtype($question) {
        return question_bank::get_qtype_name($question->qtype);
    }

    /**
     * The question name.
     * @param object $question containst the data to display.
     * @return string contents of this table cell.
     */
    protected function col_name($question) {
        $name = $question->name;

        if ($this->is_downloading()) {
            return $name;
        }

        $url = null;
        if ($question->_stats->subquestion) {
            $url = new moodle_url($this->baseurl, array('qid' => $question->id));
        } else if ($question->_stats->slot && $question->qtype != 'random') {
            $url = new moodle_url($this->baseurl, array('slot' => $question->_stats->slot));
        }

        if ($url) {
            $name = html_writer::link($url, $name,
                    array('title' => get_string('detailedanalysis', 'quiz_statistics')));
        }

        if ($this->is_dubious_question($question)) {
            $name = html_writer::tag('div', $name, array('class' => 'dubious'));
        }

        return $name;
    }

    /**
     * The number of attempts at this question.
     * @param object $question containst the data to display.
     * @return string contents of this table cell.
     */
    protected function col_s($question) {
        if (!isset($question->_stats->s)) {
            return 0;
        }

        return $question->_stats->s;
    }

    /**
     * The facility index (average fraction).
     * @param object $question containst the data to display.
     * @return string contents of this table cell.
     */
    protected function col_facility($question) {
        if (is_null($question->_stats->facility)) {
            return '';
        }

        return number_format($question->_stats->facility*100, 2) . '%';
    }

    /**
     * The standard deviation of the fractions.
     * @param object $question containst the data to display.
     * @return string contents of this table cell.
     */
    protected function col_sd($question) {
        if (is_null($question->_stats->sd) || $question->_stats->maxmark == 0) {
            return '';
        }

        return number_format($question->_stats->sd*100 / $question->_stats->maxmark, 2) . '%';
    }

    /**
     * An estimate of the fraction a student would get by guessing randomly.
     * @param object $question containst the data to display.
     * @return string contents of this table cell.
     */
    protected function col_random_guess_score($question) {
        if (is_null($question->_stats->randomguessscore)) {
            return '';
        }

        return number_format($question->_stats->randomguessscore * 100, 2).'%';
    }

    /**
     * The intended question weight. Maximum mark for the question as a percentage
     * of maximum mark for the quiz. That is, the indended influence this question
     * on the student's overall mark.
     * @param object $question containst the data to display.
     * @return string contents of this table cell.
     */
    protected function col_intended_weight($question) {
        return quiz_report_scale_summarks_as_percentage(
                $question->_stats->maxmark, $this->quiz);
    }

    /**
     * The effective question weight. That is, an estimate of the actual
     * influence this question has on the student's overall mark.
     * @param object $question containst the data to display.
     * @return string contents of this table cell.
     */
    protected function col_effective_weight($question) {
        global $OUTPUT;

        if ($question->_stats->subquestion) {
            return '';
        }

        if ($question->_stats->negcovar) {
            $negcovar = get_string('negcovar', 'quiz_statistics');

            if (!$this->is_downloading()) {
                $negcovar = html_writer::tag('div',
                        $negcovar . $OUTPUT->help_icon('negcovar', 'quiz_statistics'),
                        array('class' => 'negcovar'));
            }

            return $negcovar;
        }

        return number_format($question->_stats->effectiveweight, 2) . '%';
    }

    /**
     * Discrimination index. This is the product moment correlation coefficient
     * between the fraction for this qestion, and the average fraction for the
     * other questions in this quiz.
     * @param object $question containst the data to display.
     * @return string contents of this table cell.
     */
    protected function col_discrimination_index($question) {
        if (!is_numeric($question->_stats->discriminationindex)) {
            return $question->_stats->discriminationindex;
        }

        return number_format($question->_stats->discriminationindex, 2) . '%';
    }

    /**
     * Discrimination efficiency, similar to, but different from, the Discrimination index.
     * @param object $question containst the data to display.
     * @return string contents of this table cell.
     */
    protected function col_discriminative_efficiency($question) {
        if (!is_numeric($question->_stats->discriminativeefficiency)) {
            return '';
        }

        return number_format($question->_stats->discriminativeefficiency, 2) . '%';
    }

    /**
     * This method encapsulates the test for wheter a question should be considered dubious.
     * @param object question the question object with a property _stats which
     * includes all the stats for the question.
     * @return bool is this question possibly not pulling it's weight?
     */
    protected function is_dubious_question($question) {
        if (!is_numeric($question->_stats->discriminativeefficiency)) {
            return false;
        }

        return $question->_stats->discriminativeefficiency < 15;
    }

    public function  wrap_html_start() {
        // Horrible Moodle 2.0 wide-content work-around.
        if (!$this->is_downloading()) {
            echo html_writer::start_tag('div', array('id' => 'tablecontainer',
                    'class' => 'statistics-tablecontainer'));
        }
    }

    public function wrap_html_finish() {
        if (!$this->is_downloading()) {
            echo html_writer::end_tag('div');
        }
    }
}
