<?php

namespace app\mzl\common\traits;

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

trait DataTransformer
{
    /**
     * 核心方法：对任意数据进行转换并返回数组
     *
     * @param mixed         $rawData        原始数据，可为 Paginator / Model / Collection / array 等
     * @param callable|null $postProcessor  可选的后置处理回调，接受处理完的数组再返回新的数组
     * @param callable|null $fieldFormatter 可选的字段命名转换回调，如 snake_case
     *
     * @return array
     */
    protected function transformData(
        mixed $rawData,
        ?callable $postProcessor = null,
        ?callable $fieldFormatter = null
    ): array {
        try {
            $fieldFormatter = $fieldFormatter ?: fn($field) => $field;

            if ($rawData instanceof LengthAwarePaginator) {
                $formatted = $this->formatPaginated($rawData, $postProcessor, $fieldFormatter);
            } elseif ($rawData instanceof Model) {
                $formatted = $this->formatModel($rawData, $fieldFormatter);
            } elseif ($rawData instanceof Collection) {
                $formatted = $this->formatCollection($rawData, $fieldFormatter);
            } elseif (is_array($rawData)) {
                $formatted = $this->formatArray($rawData, $fieldFormatter);
            } else {
                $formatted = (array) $rawData;
            }

            if (is_callable($postProcessor)) {
                $formatted = $postProcessor($formatted);
            }

            return $formatted;
        } catch (\Throwable $e) {
            return [
                'error'   => true,
                'message' => $e->getMessage(),
                'code'    => $e->getCode(),
            ];
        }
    }

    /**
     * 格式化分页数据：将每条记录也进行 transformData 递归处理
     *
     * @param LengthAwarePaginator $paginator
     * @param callable|null        $postProcessor
     * @param callable             $fieldFormatter
     * @return array
     */
    protected function formatPaginated(
        LengthAwarePaginator $paginator,
        ?callable $postProcessor,
        callable $fieldFormatter
    ): array {
        $list = $paginator->getCollection()->map(function ($item) use ($postProcessor, $fieldFormatter) {
            return $this->transformData($item, $postProcessor, $fieldFormatter);
        })->toArray();

        $meta = [
            'current_page'   => $paginator->currentPage(),
            'per_page'       => $paginator->perPage(),
            'total'          => $paginator->total(),
            'last_page'      => $paginator->lastPage(),
            'first_page_url' => $paginator->url(1),
            'last_page_url'  => $paginator->url($paginator->lastPage()),
            'next_page_url'  => $paginator->nextPageUrl(),
            'prev_page_url'  => $paginator->previousPageUrl(),
        ];

        return [
            'list' => $list,
            'meta' => $meta,
        ];
    }

    /**
     * 格式化 Eloquent 模型：递归嵌套关联
     *
     * @param Model    $model
     * @param callable $fieldFormatter
     * @return array
     */
    protected function formatModel(Model $model, callable $fieldFormatter): array
    {
        $formatted = [];

        // 主表字段
        foreach ($model->getAttributes() as $key => $value) {
            $formatted[$fieldFormatter($key)] = $value;
        }

        // 关联数据，递归嵌套
        foreach ($model->getRelations() as $relation => $relationData) {
            if ($relationData instanceof Model) {
                // 单个关联模型
                $formatted[$relation] = $this->formatModel($relationData, $fieldFormatter);
            } elseif ($relationData instanceof Collection) {
                // 关联集合
                $formatted[$relation] = $relationData
                    ->map(fn($item) => $this->transformData($item, null, $fieldFormatter))
                    ->toArray();
            }
        }

        return $formatted;
    }

    /**
     * 格式化集合
     *
     * @param Collection $collection
     * @param callable   $fieldFormatter
     * @return array
     */
    protected function formatCollection(Collection $collection, callable $fieldFormatter): array
    {
        return $collection->map(fn($item) => $this->transformData($item, null, $fieldFormatter))
                          ->toArray();
    }

    /**
     * 格式化普通数组
     *
     * @param array    $array
     * @param callable $fieldFormatter
     * @return array
     */
    protected function formatArray(array $array, callable $fieldFormatter): array
    {
        return array_map(fn($item) => $this->transformData($item, null, $fieldFormatter), $array);
    }

    /**
     * 递归裁剪数组，只保留指定字段
     *
     * @param array       $data      当前要裁剪的数据（可能是单条关联，也可能是 list）
     * @param array       $fieldsMap 白名单映射，key=>[allowed fields]
     * @param string      $path      当前路径（'' / 'items' / 'items.sub' …）
     * @return array
     */
    protected function pruneFields(array $data, array $fieldsMap, string $path = ''): array
    {
        // —— 新增：如果这是一个纯列表（list），逐项递归 prune 并返回
        if ($this->isListArray($data)) {
            return array_map(
                fn($item) => is_array($item)
                    ? $this->pruneFields($item, $fieldsMap, $path)
                    : $item,
                $data
            );
        }

        // 如果当前层没有配置白名单，原样返回（或也可以 return [] 视业务）
        if (! isset($fieldsMap[$path])) {
            return $data;
        }

        $allowed = $fieldsMap[$path];
        $out     = [];

        foreach ($allowed as $key) {
            if (! array_key_exists($key, $data)) {
                continue;
            }
            $val = $data[$key];

            // 如果下一层还是个数组，继续递归
            if (is_array($val)) {
                $nextPath = ltrim($path . '.' . $key, '.');
                $out[$key] = $this->pruneFields($val, $fieldsMap, $nextPath);
            } else {
                $out[$key] = $val;
            }
        }

        return $out;
    }

    /**
     * 把 Paginator/Model/Collection/array 统一格式化，并按 fieldsMap 裁剪
     *
     * @param mixed         $rawData
     * @param array|null    $fieldsMap   顶层 '' + 各关联路径的白名单
     * @param callable|null $fieldFormatter 字段格式化回调
     * @param callable|null $postProcessor  单条记录后置处理回调
     * @return array
     */
    protected function transformAndPrune(
        mixed $rawData,
        ?array $fieldsMap = null,
        ?callable $fieldFormatter = null,
        ?callable $postProcessor = null
    ): array {
        // 1) 统一转换成数组
        $data = $this->transformData($rawData, null, $fieldFormatter);

        // 2) 如果没有白名单配置，直接返回原始数据
        if (empty($fieldsMap) || !isset($fieldsMap[''])) {
            return $data;
        }

        // 3) 分页结构：['list'=>[...],'meta'=>[...]]
        if (isset($data['list'], $data['meta'])) {
            $data['list'] = array_map(
                fn($item) => $this->processItem($item, $fieldsMap, $postProcessor),
                $data['list']
            );
            return $data;
        }

        // 4) 数字索引数组 => 当作“非分页列表”处理
        if ($this->isListArray($data)) {
            return array_map(
                fn($item) => $this->processItem($item, $fieldsMap, $postProcessor),
                $data
            );
        }

        // 5) 单条记录
        return $this->processItem($data, $fieldsMap, $postProcessor);
    }

    /**
     * 裁剪并做后置处理
     */
    private function processItem(
        array $item,
        array $fieldsMap,
        ?callable $postProcessor
    ): array {
        $pruned = $this->pruneFields($item, $fieldsMap);
        return $postProcessor ? $postProcessor($pruned) : $pruned;
    }

    /**
     * 判断一个数组是不是“索引从 0 开始的列表”
     */
    private function isListArray(array $arr): bool
    {
        if (empty($arr)) {
            return true;
        }
        return array_keys($arr) === range(0, count($arr) - 1);
    }
}