<?php

namespace App\View;

use JumPHP\Input\TouchControls;
use JumPHP\Renderer\Renderer;

/**
 * Watches the fingers on the screen (the engine only follows one): two fingers moving apart or together are a pinch.
 * Installed as the input's touch observer; what was there before (the phone app's own controls) still gets everything.
 */
final class Pinch extends TouchControls
{
    /** @var array<string, array{0: float, 1: float}> finger id => position, 0..1 of the screen */
    private array $fingers = [];
    private float $factor = 1.0;
    private ?float $last = null;

    public function __construct(private ?TouchControls $inner = null)
    {
    }

    public function beforeEvents(): void
    {
        $this->inner?->beforeEvents();
    }

    public function handle($event, Renderer $renderer): bool
    {
        $f = $event->tfinger;
        $id = (string)$f->fingerId;
        if ($event->type === \SDL_FINGERUP) {
            unset($this->fingers[$id]);
            $this->last = null;
        } else {
            $this->fingers[$id] = [(float)$f->x, (float)$f->y];
        }
        if (count($this->fingers) > 2) {   // a third finger: start again with the newest two
            $this->fingers = array_slice($this->fingers, -2, null, true);
            $this->last = null;
        }
        if (count($this->fingers) === 2) {
            [$a, $b] = array_values($this->fingers);
            $d = hypot(($a[0] - $b[0]) * 16, ($a[1] - $b[1]) * 9);
            if ($this->last !== null && $this->last > 0.01 && $d > 0.01) {
                $this->factor *= $d / $this->last;
            }
            $this->last = $d;
        }
        return $this->inner?->handle($event, $renderer) ?? false;
    }

    public function draw(Renderer $r): void
    {
        $this->inner?->draw($r);
    }

    /** Forgets every finger (a lost finger-up must not leave a pinch on forever). */
    public function reset(): void
    {
        $this->fingers = [];
        $this->factor = 1.0;
        $this->last = null;
    }

    /** Two fingers are down. */
    public function active(): bool
    {
        return count($this->fingers) >= 2;
    }

    /** How much the fingers spread since the last call (1: nothing), and where their middle is (0..1). @return array{0: float, 1: float, 2: float} */
    public function take(): array
    {
        $factor = $this->factor;
        $this->factor = 1.0;
        $pts = array_values($this->fingers);
        $n = max(1, count($pts));
        return [$factor, array_sum(array_column($pts, 0)) / $n, array_sum(array_column($pts, 1)) / $n];
    }
}