<?php
namespace JVBase\managers\queue\mergers;

use JVBase\managers\queue\Mergeable;
use JVBase\managers\queue\Operation;

/**
 * Field-aware merger for upload operations.
 * Ensures uploads only merge when targeting the same field + post/term context.
 * Post_group uploads (no field_name) merge by content type only.
 */
final class UploadMerger implements Mergeable
{
	public function __construct(
		private string|array $chunkKey
	) {}

	public function matchCriteria(Operation $incoming): array
	{
		$data = $incoming->requestData;
		$criteria = [];

		if (!empty($data['content'])) {
			$criteria['content'] = $data['content'];
		}

		// Meta destination: scope to specific field + target
		if (($data['destination'] ?? 'meta') === 'meta') {
			if (!empty($data['field_name'])) {
				$criteria['field_name'] = $data['field_name'];
			}
			if (!empty($data['post_id'])) {
				$criteria['post_id'] = $data['post_id'];
			} elseif (!empty($data['term_id'])) {
				$criteria['term_id'] = $data['term_id'];
			}
		}

		return $criteria;
	}

	public function canMerge(Operation $existing, Operation $incoming): bool
	{
		foreach ((array) $this->chunkKey as $key) {
			if (!isset($incoming->requestData[$key])) {
				return false;
			}
		}
		return true;
	}

	public function merge(Operation $existing, Operation $incoming): Operation
	{
		foreach ((array) $this->chunkKey as $key) {
			$existing->requestData[$key] = array_replace(
				$existing->requestData[$key] ?? [],
				$incoming->requestData[$key] ?? []
			);
		}

		$existing->totalItems += $incoming->totalItems;
		return $existing;
	}
}