<?php

namespace App\Business;

use Generator;
use RuntimeException;
use ZipArchive;

/**
 * 聚水潭「导出订单」Excel（.xlsx）流式读取器。
 *
 * 聚水潭导出的文件有几个特点，直接套常规 Excel 读法会踩坑：
 *  - 字符串用 inlineStr 内联存储（sharedStrings 里是空的）；
 *  - worksheet 的 <dimension> 只写一个 A1，靠它判断行数会把整表读成空；
 *  - 一行订单一个商品明细，单文件常见上万行 × 上百列，解压后几十 MB。
 *
 * 所以这里用 ZipArchive 取压缩流 + expat 增量解析，只保留调用方点名的列，
 * 内存占用与文件大小无关（导出 20 万行也不会整表进内存）。
 */
class JstOrderExportReader
{
    private const READ_CHUNK = 262144;

    /**
     * 逐行读取导出文件（跳过表头行）。
     *
     * @param  list<string>  $columns  需要取出并作为返回键的表头名，必须与文件第一行完全一致
     * @return Generator<int, array<string, string>>
     */
    public function rows(string $path, array $columns): Generator
    {
        if (! is_file($path)) {
            throw new RuntimeException('订单导出文件不存在：' . $path);
        }

        $zip = new ZipArchive();
        if ($zip->open($path) !== true) {
            throw new RuntimeException('无法打开订单导出文件（不是有效的 xlsx）：' . $path);
        }

        $stream = $zip->getStream($this->worksheetPath($zip));
        if ($stream === false) {
            $zip->close();

            throw new RuntimeException('订单导出文件里没有可读的工作表。');
        }

        try {
            yield from $this->parseSheet($stream, $this->sharedStrings($zip), $columns);
        } finally {
            fclose($stream);
            $zip->close();
        }
    }

    /**
     * @param  resource  $stream
     * @param  list<string>  $shared
     * @param  list<string>  $columns
     * @return Generator<int, array<string, string>>
     */
    private function parseSheet($stream, array $shared, array $columns): Generator
    {
        $state = [
            'row' => [],
            'column' => -1,
            'type' => null,
            'value' => '',
            'inValue' => false,
            'rowNumber' => 0,
            'wanted' => [],
            'pending' => [],
        ];

        $parser = xml_parser_create('UTF-8');
        xml_parser_set_option($parser, XML_OPTION_CASE_FOLDING, 0);

        xml_set_element_handler(
            $parser,
            static function ($parser, string $name, array $attributes) use (&$state): void {
                switch ($name) {
                    case 'row':
                        $state['row'] = [];
                        $state['column'] = -1;
                        break;

                    case 'c':
                        $state['column'] = self::columnIndex($attributes['r'] ?? null, $state['column'] + 1);
                        $state['type'] = $attributes['t'] ?? null;
                        $state['value'] = '';
                        break;

                    case 'v':
                    case 't':
                        $state['inValue'] = true;
                        break;
                }
            },
            static function ($parser, string $name) use (&$state, $shared, $columns): void {
                switch ($name) {
                    case 'v':
                    case 't':
                        $state['inValue'] = false;
                        break;

                    case 'c':
                        $state['row'][$state['column']] = self::cellValue($state['type'], $state['value'], $shared);
                        break;

                    case 'row':
                        $state['rowNumber']++;
                        if ($state['rowNumber'] === 1) {
                            $state['wanted'] = self::wantedColumns($state['row'], $columns);

                            break;
                        }

                        $values = [];
                        foreach ($state['wanted'] as $index => $column) {
                            $values[$column] = $state['row'][$index] ?? '';
                        }
                        $state['pending'][] = $values;
                        break;
                }
            }
        );

        xml_set_character_data_handler($parser, static function ($parser, string $data) use (&$state): void {
            if ($state['inValue']) {
                $state['value'] .= $data;
            }
        });

        $first = true;
        try {
            while (! feof($stream)) {
                $chunk = fread($stream, self::READ_CHUNK);
                if ($chunk === false || $chunk === '') {
                    break;
                }
                if ($first) {
                    // 聚水潭导出的 XML 带 UTF-8 BOM，expat 会当成非法前缀。
                    $chunk = preg_replace('/^\xEF\xBB\xBF/', '', $chunk, 1);
                    $first = false;
                }

                if (xml_parse($parser, $chunk, false) === 0) {
                    throw new RuntimeException('订单导出文件解析失败：' . xml_error_string(xml_get_error_code($parser)));
                }

                while ($state['pending'] !== []) {
                    yield array_shift($state['pending']);
                }
            }

            if (xml_parse($parser, '', true) === 0) {
                throw new RuntimeException('订单导出文件解析失败：' . xml_error_string(xml_get_error_code($parser)));
            }
        } finally {
            xml_parser_free($parser);
        }

        while ($state['pending'] !== []) {
            yield array_shift($state['pending']);
        }
    }

    /**
     * 表头行 -> [列下标 => 列名]，并校验需要的列都在。
     *
     * @param  array<int, string>  $header
     * @param  list<string>  $columns
     * @return array<int, string>
     */
    private static function wantedColumns(array $header, array $columns): array
    {
        $byName = [];
        foreach ($header as $index => $name) {
            $name = trim($name);
            if ($name !== '' && ! isset($byName[$name])) {
                $byName[$name] = $index;
            }
        }

        $wanted = [];
        foreach ($columns as $column) {
            if (! isset($byName[$column])) {
                throw new RuntimeException('订单导出文件缺少列：' . $column);
            }
            $wanted[$byName[$column]] = $column;
        }

        return $wanted;
    }

    /**
     * @param  list<string>  $shared
     */
    private static function cellValue(?string $type, string $value, array $shared): string
    {
        if ($type === 's') {
            return $shared[(int) $value] ?? '';
        }

        return trim($value);
    }

    /** 单元格引用（如 AV12）-> 0 基列下标。 */
    private static function columnIndex(?string $reference, int $fallback): int
    {
        if ($reference === null || preg_match('/^([A-Z]+)/i', $reference, $matches) !== 1) {
            return $fallback;
        }

        $letters = strtoupper($matches[1]);
        $index = 0;
        for ($i = 0, $length = strlen($letters); $i < $length; $i++) {
            $index = $index * 26 + (ord($letters[$i]) - 64);
        }

        return $index - 1;
    }

    private function worksheetPath(ZipArchive $zip): string
    {
        $workbook = $zip->getFromName('xl/workbook.xml');
        $relationships = $zip->getFromName('xl/_rels/workbook.xml.rels');
        if (is_string($workbook) && is_string($relationships)
            && preg_match('/<sheet[^>]*r:id="([^"]+)"/', $workbook, $sheet) === 1
            && preg_match('/Id="' . preg_quote($sheet[1], '/') . '"[^>]*Target="([^"]+)"/', $relationships, $target) === 1) {
            $path = ltrim($target[1], '/');

            return str_starts_with($path, 'xl/') ? $path : 'xl/' . $path;
        }

        for ($i = 0; $i < $zip->numFiles; $i++) {
            $name = (string) $zip->getNameIndex($i);
            if (preg_match('#^xl/worksheets/[^/]+\.xml$#', $name) === 1) {
                return $name;
            }
        }

        return 'xl/worksheets/sheet1.xml';
    }

    /**
     * 读取共享字符串表；聚水潭导出通常为空，但标准 xlsx 会用到。
     *
     * @return list<string>
     */
    private function sharedStrings(ZipArchive $zip): array
    {
        $xml = $zip->getFromName('xl/sharedStrings.xml');
        if (! is_string($xml) || $xml === '') {
            return [];
        }

        $out = [];
        $index = -1;
        $buffer = '';
        $inside = false;

        $parser = xml_parser_create('UTF-8');
        xml_parser_set_option($parser, XML_OPTION_CASE_FOLDING, 0);
        xml_set_element_handler(
            $parser,
            static function ($parser, string $name) use (&$inside, &$buffer, &$index): void {
                if ($name === 'si') {
                    $index++;
                    $buffer = '';
                } elseif ($name === 't') {
                    $inside = true;
                }
            },
            static function ($parser, string $name) use (&$inside, &$buffer, &$out): void {
                if ($name === 't') {
                    $inside = false;
                } elseif ($name === 'si') {
                    $out[] = $buffer;
                }
            }
        );
        xml_set_character_data_handler($parser, static function ($parser, string $data) use (&$inside, &$buffer): void {
            if ($inside) {
                $buffer .= $data;
            }
        });

        try {
            xml_parse($parser, preg_replace('/^\xEF\xBB\xBF/', '', $xml, 1), true);
        } finally {
            xml_parser_free($parser);
        }

        return $out;
    }
}