<?php
/**
 * SeekQuarry/Yioop --
 * Open Source Pure PHP Search Engine, Crawler, and Indexer
 *
 * Copyright (C) 2009 - 2026  Chris Pollett chris@pollett.org
 *
 * LICENSE:
 *
 * This program 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.
 *
 * This program 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 this program.  If not, see <https://www.gnu.org/licenses/>.
 *
 * END LICENSE
 *
 * @author Chris Pollett chris@pollett.org
 * @license https://www.gnu.org/licenses/ GPL3
 * @link https://www.seekquarry.com/
 * @copyright 2009 - 2026
 * @filesource
 */
namespace seekquarry\yioop\tests;

use seekquarry\yioop\library\av_processing\SpeechFilter;
use seekquarry\yioop\library\UnitTest;

/**
 * SpeechFilterTest checks that SpeechFilter turns the sixteen
 * frequencies describing a stretch of speech into the sixteen terms of
 * the filter that plays it back.
 *
 * The terms were compared against the reference decoder for the Opus
 * audio codec, built here and made to print the terms it works out: on
 * ten seconds of speech, 198 packets, all sixteen terms of every packet
 * agree. The cases below hold that agreement for one stretch and the
 * rules the arithmetic must keep for any stretch.
 *
 * @author Chris Pollett
 */
class SpeechFilterTest extends UnitTest
{
    /**
     * A_REAL_SHAPE is the sixteen frequencies of the forty-third packet
     * of the test speech, each written out of 32768.
     * @var array
     */
    const A_REAL_SHAPE = [1324, 1675, 3953, 5462, 6723, 8741, 10291,
        12230, 13144, 14993, 17664, 20645, 22656, 24687, 27345, 30336];
    /**
     * ITS_TERMS is the sixteen filter terms the reference decoder works
     * out from those frequencies, each written out of 4096.
     * @var array
     */
    const ITS_TERMS = [12204, -16443, 13071, -6614, 3016, -2091, 326,
        2283, -3013, 1807, -652, 334, -526, 715, -705, 259];
    /**
     * setUp does nothing; every case works from numbers it holds itself.
     */
    public function setUp()
    {
    }
    /**
     * tearDown does nothing, since no case here writes a file.
     */
    public function tearDown()
    {
    }
    /**
     * realShapeGivesTheTermsTheReferenceGivesTestCase checks the
     * sixteen terms worked out for one stretch of the test speech
     * against what the reference decoder works out for it. Every step of
     * the arithmetic shows up in these numbers, so one wrong rounding
     * anywhere breaks this case.
     */
    public function realShapeGivesTheTermsTheReferenceGivesTestCase()
    {
        $this->assertEqual(self::ITS_TERMS,
            SpeechFilter::termsFor(self::A_REAL_SHAPE),
            "the sixteen terms are the ones the reference works out");
    }
    /**
     * everyShapeGivesSixteenTermsTestCase checks that a shape gives one
     * term for each of its frequencies, and that each term fits in the
     * range a term is written in. A term outside that range would be cut
     * short when the sound is played back.
     */
    public function everyShapeGivesSixteenTermsTestCase()
    {
        $terms = SpeechFilter::termsFor(self::A_REAL_SHAPE);
        $this->assertEqual(SpeechFilter::TERMS_IN_FILTER, count($terms),
            "sixteen frequencies give sixteen terms");
        foreach ($terms as $one) {
            $this->assertTrue($one >= -32768 && $one <= 32767,
                "each term fits where it is written, and one was $one");
        }
    }
    /**
     * frequenciesSpreadEvenlyGiveASmallFilterTestCase checks that
     * frequencies spread evenly across the range give terms that are all
     * small. Even spreading is what a flat sound looks like, and a flat
     * sound needs almost no filtering.
     */
    public function frequenciesSpreadEvenlyGiveASmallFilterTestCase()
    {
        $even = [];
        for ($at = 1; $at <= SpeechFilter::TERMS_IN_FILTER; $at++) {
            $even[] = (int)(32768 * $at /
                (SpeechFilter::TERMS_IN_FILTER + 1));
        }
        $terms = SpeechFilter::termsFor($even);
        $largest = 0;
        foreach ($terms as $one) {
            $largest = max($largest, abs($one));
        }
        $this->assertTrue($largest < 4096,
            "evenly spread frequencies give terms under one, and the " .
            "largest was $largest");
    }
    /**
     * roundingGoesToTheNearestTestCase checks the rounding the whole
     * arithmetic rests on. Rounding toward zero instead moves a term by
     * one, which is enough to disagree with every other decoder.
     */
    public function roundingGoesToTheNearestTestCase()
    {
        $this->assertEqual(2, SpeechFilter::roundedShift(3, 1),
            "three halved rounds up to two");
        $this->assertEqual(1, SpeechFilter::roundedShift(2, 1),
            "two halved stays at one");
        $this->assertEqual(-1, SpeechFilter::roundedShift(-3, 1),
            "minus three halved rounds toward zero to minus one");
        $this->assertEqual(5, SpeechFilter::roundedShift(5, 0),
            "no halving at all leaves the number alone");
    }
}
