<?php
namespace app\common\traits;

use Illuminate\Pagination\LengthAwarePaginator;
use Illuminate\Database\Eloquent\Model;
use Illuminate\Support\Collection;

/**
 * 数据转换器 Trait
 * 用于将原始数据（如模型、集合、分页等）统一转换为数组格式，
 * 并支持字段级与结果级的灵活后置加工。
 */
trait DataTransformer
{
    /**
     * 核心转换方法
     *
     * @param mixed       $rawData          原始数据：Model、Collection、Paginator、数组等
     * @param array       $opts             可选配置：
     *   - 'fieldFormatter'  => callable 字段名格式化回调，如 fn($f)=>snake_case($f)
     *   - 'postFormatter'   => callable 结果级加工回调，接收整个数组并返回
     *
     * @return array 转换并加工后的纯 PHP 数组
     */
    protected function transformData(
        mixed $rawData,
        ?callable $postFormatter = null,
        ?callable $fieldFormatter = null
    ): array {
        try {
            $fieldFormatter = $fieldFormatter ?: fn($field) => $field;
            if ($rawData instanceof LengthAwarePaginator) {
                $arr = $this->formatPaginated($rawData, $postFormatter, $fieldFormatter);
            } elseif ($rawData instanceof Model) {
                $arr = $this->formatModel($rawData, $fieldFormatter);
            } elseif ($rawData instanceof Collection) {
                $arr = $this->formatCollection($rawData, $fieldFormatter);
            } elseif (is_array($rawData)) {
                $arr = $this->formatArray($rawData, $fieldFormatter);
            } else {
                $arr = (array)$rawData;
            }

            if (is_callable($postFormatter)) {
                $arr = $postFormatter($arr);
            }

            return $arr;
        } catch (\Throwable $e) {
            return [
                'error'   => true,
                'message' => $e->getMessage(),
                // 'message' => $e->getMessage()."\n".$e->getLine()."\n".$e->getFile(),
                'code'    => $e->getCode(),
            ];
        }
    }

    /**
     * 格式化分页数据：转换每条记录
     *
     * @param LengthAwarePaginator $p
     * @param callable             $fmt
     * @return array{records: array, total: int, current: int, size: int}
     */
    protected function formatPaginated(
        LengthAwarePaginator $p,
        ?callable $postFormatter,
        callable $fmt
    ): array {
        $records = $p->getCollection()
            ->map(fn($item) => $this->transformData($item, $postFormatter, $fmt))
            ->toArray();

        return [
            'records' => $records,
            'total'   => $p->total(),
            'current' => $p->currentPage(),
            'size'    => $p->perPage(),
        ];
    }

    /**
     * 格式化 Eloquent 模型：主表属性 + 关联递归
     *
     * @param Model    $model
     * @param callable $fmt
     * @return array
     */
    protected function formatModel(
        Model $model,
        callable $fmt
    ): array {
        $out = [];
        // 1) 主表字段
        foreach ($model->getAttributes() as $key => $value) {
            $out[$fmt($key)] = $value;
        }
        // 2) 关联递归
        foreach ($model->getRelations() as $rel => $relData) {
            if ($relData instanceof Model) {
                $out[$rel] = $this->formatModel($relData, $fmt);
            } elseif ($relData instanceof Collection) {
                $out[$rel] = $relData
                    ->map(fn($item) => $this->transformData($item, null, $fmt))
                    ->toArray();
            } else {
                $out[$rel] = $relData;
            }
        }
        return $out;
    }

    /**
     * 格式化集合数据：对每个元素递归调用 transformData
     *
     * @param Collection $c
     * @param callable   $fmt
     * @return array
     */
    protected function formatCollection(
        Collection $c,
        callable $fmt
    ): array {
        return $c
            ->map(fn($item) => $this->transformData($item, null, $fmt))
            ->toArray();
    }

    /**
     * 格式化普通数组：递归处理可能出现的模型或集合
     *
     * @param array    $arr
     * @param callable $fmt
     * @return array
     */
    protected function formatArray(
        array $arr,
        callable $fmt
    ): array {
        return array_map(function($item) use ($fmt) {
            if (is_array($item)
                || $item instanceof Model
                || $item instanceof Collection
                || $item instanceof LengthAwarePaginator
            ) {
                return $this->transformData($item, null, $fmt);
            }
            return $item;
        }, $arr);
    }
}