<?php

namespace App\Scene;

use App\Audio\Scale;
use App\Render\Gfx;
use JumPHP\Renderer\Renderer;

/**
 * A spiral of dots that turns: the arms seem to flow outwards (or inwards) while the dots only circle, their size ripples along the arms and the
 * colours run round. Each arm that goes past the top or the bottom plays a note of a whole-tone scale (dreamy, no resolution). One turn
 * every 4 seconds, so the film loops with no seam.
 */
final class SpiralScene extends VideoScene
{
    public const SECONDS = 24.0;
    protected const LOOPS = true;
    public const PERIOD = 4.0;
    public const ARMS = 8;
    private const DOTS = 24;
    private int $lastTick = -1;
    private float $glowTop = 0.0;

    protected function melodyNotes(): string
    {
        return 'C4';
    }

    protected function headingText(): string
    {
        return 'WATCH THE CENTRE';
    }

    protected function hookText(): string
    {
        return 'ARE THE ARMS MOVING OUT?';
    }

    protected function captionText(): string
    {
        return $this->t('TURNS {n}', ['n' => (int)floor($this->time / self::PERIOD)]);
    }

    protected function build(): void
    {
        $this->lastTick = -1;
        $this->glowTop = 0.0;
    }

    protected function tick(float $dt): void
    {
        // an arm is at the top (or the bottom) every PERIOD / (2 ARMS) seconds
        $n = (int)floor($this->time / self::PERIOD * self::ARMS * 2);
        if ($n > $this->lastTick) {
            $this->lastTick = $n;
            $this->glowTop = 1.0;
            $this->play(Scale::freq(Scale::WHOLE_TONE, 2 + [0, 3, 1, 4, 2, 5, 3, 6][$n % 8] + ($n % 2) * 6, 60), 'bell', 0.9, 0.22, 0.0);
            $this->pulse = 0.8;
            $this->tint = Gfx::hsv($n * 0.05);
        }
        $this->glowTop = max(0.0, $this->glowTop - $dt * 3);
    }

    protected function drawWorld(Renderer $r): void
    {
        $cx = 135.0;
        $cy = 262.0;
        $turn = $this->time / self::PERIOD;
        for ($arm = 0; $arm < self::ARMS; $arm++) {
            for ($j = 0; $j < self::DOTS; $j++) {
                $u = ($j + 1) / self::DOTS;                              // 0..1 along the arm
                $rad = 8 + 128 * $u ** 0.9;
                $a = $turn * 2 * M_PI + $arm * 2 * M_PI / self::ARMS + $u * 4.4;
                $size = 1.1 + 4.6 * $u * (0.55 + 0.45 * sin(2 * M_PI * (3 * $u - 2 * $turn)));
                $hue = $arm / self::ARMS + $u * 0.35 + $turn * 0.25;
                $x = $cx + cos($a) * $rad;
                $y = $cy + sin($a) * $rad;
                Gfx::disc($r, $x, $y, $size, Gfx::hsv($hue, 0.55, 0.65 + 0.35 * $u));
            }
        }
        Gfx::glow($r, $cx, $cy, 5 + 4 * $this->glowTop, [255, 255, 255], 0.9);
        Gfx::disc($r, $cx, $cy, 3.4, [255, 255, 255]);
    }
}