1<?php
2// This file is part of Moodle - http://moodle.org/
3//
4// Moodle is free software: you can redistribute it and/or modify
5// it under the terms of the GNU General Public License as published by
6// the Free Software Foundation, either version 3 of the License, or
7// (at your option) any later version.
8//
9// Moodle is distributed in the hope that it will be useful,
10// but WITHOUT ANY WARRANTY; without even the implied warranty of
11// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
12// GNU General Public License for more details.
13//
14// You should have received a copy of the GNU General Public License
15// along with Moodle.  If not, see <http://www.gnu.org/licenses/>.
16
17/**
18 * Discrete values target.
19 *
20 * @package   core_analytics
21 * @copyright 2017 David Monllao {@link http://www.davidmonllao.com}
22 * @license   http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
23 */
24
25namespace core_analytics\local\target;
26
27defined('MOODLE_INTERNAL') || die();
28
29/**
30 * Discrete values target.
31 *
32 * @package   core_analytics
33 * @copyright 2017 David Monllao {@link http://www.davidmonllao.com}
34 * @license   http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
35 */
36abstract class discrete extends base {
37
38    /**
39     * Are this target calculations linear values?
40     *
41     * @return bool
42     */
43    public function is_linear() {
44        // Not supported yet.
45        throw new \coding_exception('Sorry, this version\'s prediction processors only support targets with binary values.' .
46            ' You can write your own and overwrite this method though.');
47    }
48
49    /**
50     * Is the provided class one of this target valid classes?
51     *
52     * @param mixed $class
53     * @return bool
54     */
55    protected static function is_a_class($class) {
56        return (in_array($class, static::get_classes(), false));
57    }
58
59    /**
60     * get_display_value
61     *
62     * @param float $value
63     * @param string $ignoredsubtype
64     * @return string
65     */
66    public function get_display_value($value, $ignoredsubtype = false) {
67
68        if (!self::is_a_class($value)) {
69            throw new \moodle_exception('errorpredictionformat', 'analytics');
70        }
71
72        // To discard any possible weird keys devs used.
73        $classes = array_values(static::get_classes());
74        $descriptions = array_values(static::classes_description());
75
76        if (count($classes) !== count($descriptions)) {
77            throw new \coding_exception('You need to describe all your classes (' . json_encode($classes) .
78                ') in self::classes_description');
79        }
80
81        $key = array_search($value, $classes);
82        if ($key === false) {
83            throw new \coding_exception('You need to describe all your classes (' . json_encode($classes) .
84                ') in self::classes_description');
85        }
86
87        return $descriptions[$key];
88    }
89
90    /**
91     * get_calculation_outcome
92     *
93     * @param float $value
94     * @param string $ignoredsubtype
95     * @return int
96     */
97    public function get_calculation_outcome($value, $ignoredsubtype = false) {
98
99        if (!self::is_a_class($value)) {
100            throw new \moodle_exception('errorpredictionformat', 'analytics');
101        }
102
103        if (in_array($value, $this->ignored_predicted_classes(), false)) {
104            // Just in case, if it is ignored the prediction should not even be recorded.
105            return self::OUTCOME_OK;
106        }
107
108        debugging('Please overwrite \core_analytics\local\target\discrete::get_calculation_outcome, all your target ' .
109            'classes are styled the same way otherwise', DEBUG_DEVELOPER);
110        return self::OUTCOME_OK;
111    }
112
113    /**
114     * Returns all the possible values the target calculation can return.
115     *
116     * Only useful for targets using discrete values, must be overwriten if it is the case.
117     *
118     * @return array
119     */
120    public static function get_classes() {
121        // Coding exception as this will only be called if this target have non-linear values.
122        throw new \coding_exception('Overwrite get_classes() and return an array with the different values the ' .
123            'target calculation can return');
124    }
125
126    /**
127     * Returns descriptions for each of the values the target calculation can return.
128     *
129     * The array indexes should match self::get_classes indexes.
130     *
131     * @return array
132     */
133    protected static function classes_description() {
134        throw new \coding_exception('Overwrite classes_description() and return an array with a description for each of the ' .
135            'different values the target calculation can return. Indexes should match self::get_classes indexes');
136    }
137
138    /**
139     * Returns the predicted classes that will be ignored.
140     *
141     * Better be keen to add more than less classes here, the callback is always able to discard some classes. As an example
142     * a target with classes 'grade 0-3', 'grade 3-6', 'grade 6-8' and 'grade 8-10' is interested in flagging both 'grade 6-8'
143     * and 'grade 8-10' as ignored. On the other hand, a target like dropout risk with classes 'yes', 'no' may just be
144     * interested in 'yes'.
145     *
146     * @return array List of values that will be ignored (array keys are ignored).
147     */
148    public function ignored_predicted_classes() {
149        // Coding exception as this will only be called if this target have non-linear values.
150        throw new \coding_exception('Overwrite ignored_predicted_classes() and return an array with the classes that should not ' .
151            'trigger the callback');
152    }
153
154    /**
155     * This method determines if a prediction is interesing for the model or not.
156     *
157     * This method internally calls ignored_predicted_classes to skip classes
158     * flagged by the target as not important for users.
159     *
160     * @param mixed $predictedvalue
161     * @param float $predictionscore
162     * @return bool
163     */
164    public function triggers_callback($predictedvalue, $predictionscore) {
165
166        if (!parent::triggers_callback($predictedvalue, $predictionscore)) {
167            return false;
168        }
169
170        if (in_array($predictedvalue, $this->ignored_predicted_classes())) {
171            return false;
172        }
173
174        return true;
175    }
176}
177