<?php

declare(strict_types=1);

namespace Evomedien\Vitec\UserFunc;

use Evomedien\Vitec\Service\UsecaseSerializer;
use TYPO3\CMS\Core\Attribute\AsAllowedCallable;
use TYPO3\CMS\Core\Utility\GeneralUtility;
use TYPO3\CMS\Frontend\ContentObject\ContentObjectRenderer;

/**
 * UserFunc emitting the background block of a VITEC container.
 *
 * The container elements are rendered entirely in TypoScript
 * (Configuration/TypoScript/Headless/vitec_containers.typoscript), where plain
 * fields are TEXT objects. A FAL image is not a plain field, so it comes through
 * here — and going through `UsecaseSerializer::image()` rather than the headless
 * FilesProcessor is deliberate: Clause 9.2 puts image serialisation in one place,
 * so a background image has the same `{url, srcset, properties}` shape as every
 * other image in this JSON. One shape for the front end instead of two.
 *
 * Emits nothing at all when no image is set — the whole `background` key then
 * stays out of the payload, which is a clearer signal than an object with a null
 * image and two orphaned CSS settings.
 *
 * `size` and `position` are stored as CSS-ready values (`cover`, `left top`, …).
 * The single exception is `stretch`, which has no CSS keyword and the front end
 * maps to `100% 100%`; see the TCA comment in tt_content_vitec_shared.php.
 *
 * Fail-soft per Clause 9.5: any error yields an empty string, never an exception
 * that would take the surrounding content element down with it.
 */
class ContainerBackgroundRenderer
{
    private ?ContentObjectRenderer $cObj = null;

    /**
     * TYPO3 v14 no longer assigns `$classObj->cObj` dynamically. The renderer is
     * handed over through this setter, and only when the method exists at all -
     * ContentObjectRenderer::callUserFunction() duck-types it with
     * `is_callable([$classObj, 'setContentObjectRenderer'])`. Without the method
     * `$this->cObj` stays null and the userFunc never sees its own record.
     */
    public function setContentObjectRenderer(ContentObjectRenderer $cObj): void
    {
        $this->cObj = $cObj;
    }

    #[AsAllowedCallable]
    public function render(string $content, array $conf): string
    {
        try {
            $row = is_array($this->cObj?->data ?? null) ? $this->cObj->data : null;
            if ($row === null) {
                return '';
            }

            $uid = (int)($row['uid'] ?? 0);
            if ($uid <= 0) {
                return '';
            }
            // No shortcut on the tx_vitec_bg_image counter: sys_file_reference is
            // the single source of truth, and a counter that is stale or missing
            // (schema not updated yet) would silently swallow a set image. One
            // indexed query per container is cheaper than that class of bug.

            $image = GeneralUtility::makeInstance(UsecaseSerializer::class)
                ->image($uid, 'tx_vitec_bg_image', 'tt_content');
            if ($image === null) {
                return '';
            }

            return (string)json_encode([
                'image' => $image,
                'size' => $this->resolveSize($row),
                'position' => $this->resolvePosition($row),
            ]);
        } catch (\Throwable $e) {
            return '';
        }
    }

    /**
     * The stored size, resolved into something the front end can hand straight
     * to CSS. `custom` is the only value that needs a second field; turning it
     * into "80%" here keeps the promise that `size` is always usable as-is,
     * instead of making every consumer look up a companion field.
     *
     * A custom size without a usable percentage falls back to `auto` - the CSS
     * default - rather than emitting "0%" or the meaningless word "custom".
     *
     * @param array<string,mixed> $row
     */
    private function resolveSize(array $row): string
    {
        $size = (string)($row['tx_vitec_bg_size'] ?? 'cover');
        if ($size !== 'custom') {
            return $size;
        }
        $percent = (int)($row['tx_vitec_bg_size_percent'] ?? 0);
        return $percent > 0 ? $percent . '%' : 'auto';
    }

    /**
     * The stored position, again resolved into one CSS-ready value.
     *
     * The four custom fields are edge offsets, but CSS cannot take a top AND a
     * bottom offset at once, so they are folded into the percentage form. That
     * form says exactly the same thing: in `background-position` a percentage
     * aligns the same point of image and container, so "10% from the right edge"
     * IS `90%`. Nothing is lost in the translation.
     *
     * Per axis the near edge wins when both are filled - `left` over `right`,
     * `top` over `bottom` - because two opposing offsets contradict each other
     * and silently picking one beats emitting something invalid.
     *
     * @param array<string,mixed> $row
     */
    private function resolvePosition(array $row): string
    {
        $position = (string)($row['tx_vitec_bg_position'] ?? 'center center');
        if ($position !== 'custom') {
            return $position;
        }

        $x = $this->axisPercent($row, 'tx_vitec_bg_pos_left', 'tx_vitec_bg_pos_right');
        $y = $this->axisPercent($row, 'tx_vitec_bg_pos_top', 'tx_vitec_bg_pos_bottom');

        return $x . '% ' . $y . '%';
    }

    /**
     * One axis as a percentage. An empty field means "centred on this axis" -
     * which is why the columns are nullable: 0 is a legitimate offset (flush
     * against that edge) and has to stay distinguishable from "not set".
     *
     * @param array<string,mixed> $row
     */
    private function axisPercent(array $row, string $nearField, string $farField): int
    {
        $near = $row[$nearField] ?? null;
        if ($near !== null && $near !== '') {
            return (int)$near;
        }

        $far = $row[$farField] ?? null;
        if ($far !== null && $far !== '') {
            return 100 - (int)$far;
        }

        return 50;
    }
}